US20160046693A1 - Antigen-Binding Molecule for Promoting Disappearance of Antigen via Fc gamma RIIB - Google Patents

Antigen-Binding Molecule for Promoting Disappearance of Antigen via Fc gamma RIIB Download PDF

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US20160046693A1
US20160046693A1 US14/379,825 US201314379825A US2016046693A1 US 20160046693 A1 US20160046693 A1 US 20160046693A1 US 201314379825 A US201314379825 A US 201314379825A US 2016046693 A1 US2016046693 A1 US 2016046693A1
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antigen
binding
amino acid
region
aspartic acid
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Tomoyuki Igawa
Atsuhiko Maeda
Yuki Iwayanagi
Kenta Haraya
Hitoshi Katada
Shojiro Kadono
Futa Mimoto
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Chugai Pharmaceutical Co Ltd
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Chugai Pharmaceutical Co Ltd
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Priority claimed from PCT/JP2012/054624 external-priority patent/WO2012115241A1/ja
Priority claimed from PCT/JP2012/075092 external-priority patent/WO2013047752A1/ja
Application filed by Chugai Pharmaceutical Co Ltd filed Critical Chugai Pharmaceutical Co Ltd
Assigned to CHUGAI SEIYAKU KABUSHIKI KAISHA reassignment CHUGAI SEIYAKU KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: IGAWA, TOMOYUKI, KATADA, Hitoshi, IWAYANAGI, Yuki, MAEDA, ATSUHIKO, MIMOTO, FUTA, KADONO, SHOJIRO, HARAYA, Kenta
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K16/00—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K16/00—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies
    • C07K16/46—Hybrid immunoglobulins
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P29/00—Non-central analgesic, antipyretic or antiinflammatory agents, e.g. antirheumatic agents; Non-steroidal antiinflammatory drugs [NSAID]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P35/00—Antineoplastic agents
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K16/00—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies
    • C07K16/18—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from animals or humans
    • C07K16/28—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants
    • C07K16/2866—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants against receptors for cytokines, lymphokines, interferons
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K16/00—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies
    • C07K16/18—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from animals or humans
    • C07K16/28—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants
    • C07K16/30—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants from tumour cells
    • C07K16/303—Liver or Pancreas
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K39/00—Medicinal preparations containing antigens or antibodies
    • A61K2039/505—Medicinal preparations containing antigens or antibodies comprising antibodies
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/40—Immunoglobulins specific features characterized by post-translational modification
    • C07K2317/41—Glycosylation, sialylation, or fucosylation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/50—Immunoglobulins specific features characterized by immunoglobulin fragments
    • C07K2317/52—Constant or Fc region; Isotype
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/50—Immunoglobulins specific features characterized by immunoglobulin fragments
    • C07K2317/52—Constant or Fc region; Isotype
    • C07K2317/524—CH2 domain
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/50—Immunoglobulins specific features characterized by immunoglobulin fragments
    • C07K2317/52—Constant or Fc region; Isotype
    • C07K2317/526—CH3 domain
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/70—Immunoglobulins specific features characterized by effect upon binding to a cell or to an antigen
    • C07K2317/71—Decreased effector function due to an Fc-modification
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/70—Immunoglobulins specific features characterized by effect upon binding to a cell or to an antigen
    • C07K2317/72—Increased effector function due to an Fc-modification
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/70—Immunoglobulins specific features characterized by effect upon binding to a cell or to an antigen
    • C07K2317/76—Antagonist effect on antigen, e.g. neutralization or inhibition of binding
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/90—Immunoglobulins specific features characterized by (pharmaco)kinetic aspects or by stability of the immunoglobulin
    • C07K2317/92—Affinity (KD), association rate (Ka), dissociation rate (Kd) or EC50 value
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/90—Immunoglobulins specific features characterized by (pharmaco)kinetic aspects or by stability of the immunoglobulin
    • C07K2317/94—Stability, e.g. half-life, pH, temperature or enzyme-resistance

Definitions

  • the present invention provides uses of antigen-binding molecules for eliminating antigens from plasma; methods for eliminating antigens from plasma, which comprise administering antigen-binding molecules; pharmaceutical compositions comprising antigen-binding molecules that are capable of eliminating antigens from plasma; and methods for producing antigen-binding molecules for eliminating antigens from plasma.
  • Non-patent Documents 1 and 2 various technologies applicable to second-generation therapeutic antibodies have been reported, including those that enhance effector function, antigen-binding ability, pharmacokinetics, and stability, and those that reduce the risk of immunogenicity.
  • the requisite dose of a therapeutic antibody is very high. This, in turn, has led to problems, such as high production cost, as well as the difficulty in producing subcutaneous formulations.
  • the dose of a therapeutic antibody may be reduced by improving antibody pharmacokinetics or improving the affinity between antibodies and antigens.
  • Non-patent Documents 4 and 5 have reported methods for improving antibody pharmacokinetics using artificial substitution of amino acids in constant regions.
  • affinity maturation has been reported as a technology for enhancing antigen-binding activity and/or antigen-neutralizing activity of an antibody (Non-patent Document 6).
  • This technology enables enhancement of antigen-binding activity by introduction of amino acid mutations into the CDR region of a variable region or such.
  • the enhancement of antigen-binding ability enables improvement of in vitro biological activity or reduction of dosage, and further enables improvement of in vivo efficacy (Non-patent Document 7).
  • the antigen-neutralizing capacity of a single antibody molecule having neutralizing activity depends on its affinity. Therefore, the affinity of antibodies has been enhanced using various methods in order to neutralize antigens with a small amount of antibodies (Non-patent Document 6). Furthermore, if the affinity of the antibody to the antigen could be made infinite by covalent binding to the antigen, a single antibody molecule could neutralize one antigen molecule (a divalent antibody can neutralize two antigen molecules). However, the stoichiometric neutralization reaction of one antibody molecule against one antigen molecule (one divalent antibody against two antigens) is the limit of such methods, and thus it is impossible to completely neutralize antigen with an amount of antibody smaller than the amount of antigen.
  • Non-patent Document 8 antigen-neutralizing effect by enhancing affinity has a limit.
  • the antibody To sustain the neutralization effect of a neutralizing antibody for a certain period, the antibody must be administered at a dose higher than the amount of antigens produced in the body during the same period. With just the improvement of antibody pharmacokinetics or affinity maturation technology described above, there is thus a limitation in the reduction of the required antibody dose. Accordingly, in order to sustain the antigen-neutralizing effect for a target period with an amount of antibody smaller than the amount of antigen, a single antibody must neutralize multiple antigens.
  • An antigen-binding molecule that binds to an antigen in a pH- and/or metal ion concentration-dependent manner has recently been reported as a novel method for achieving the above objective (Patent Documents 1 and 2).
  • the ion concentration-dependent antigen-binding molecules which strongly bind to an antigen under neutral pH and/or high calcium ion concentration conditions in plasma and dissociate from the antigen under acidic pH and/or low calcium ion concentration conditions in the endosome, can dissociate from the antigen in the endosome.
  • an ion concentration-dependent antigen-binding molecule dissociates from the antigen is recycled to the plasma by FcRn, it can bind to another antigen again.
  • a single ion concentration-dependent antigen-binding molecule can bind to a number of antigens repeatedly.
  • the plasma retention of an antigen is very short compared to antibodies recycled via FcRn binding.
  • the plasma retention of the antigen itself is short, when a typical antibody with such a long plasma retention binds to the antigen, the plasma retention of the antigen-antibody complex is prolonged similar to the antibody.
  • the antigen bound by the antibody exists in the form of an antigen-antibody complex, which prolongs plasma retention of the antigen (antigen is not easily eliminated from plasma), and causes an increase of plasma antigen concentration.
  • an ion concentration-dependent antigen-binding molecule can suppress increase in plasma antigen concentration by dissociating from the antigen in the endosome.
  • Patent Document 3 This suppression of increase in plasma antigen concentration is affected by the balance with the amount of the antigens produced in vivo. Therefore, the possibility that administration of such ion concentration-dependent antigen-binding molecules may elevate the plasma antigen concentration as compared to before administration was considered (Patent Document 3).
  • antigen-binding molecules that bind to FcRn under neutral conditions were produced.
  • Administration of an antigen-binding molecule that binds to an antigen in an ion concentration-dependent manner and binds to FcRn under neutral conditions revealed that the molecule can decrease the plasma antigen concentration as compared to before administration (Patent Document 3).
  • typical antibodies increase the plasma antigen concentration when administered, antigen-binding molecules having FcRn-binding activity under a neutral pH condition and antigen-binding molecules that bind to an antigen in an ion concentration-dependent manner and having FcRn-binding activity under a neutral pH condition can decrease the plasma antigen concentration when they are administered. Since such antigen-binding molecules can actively eliminate antigens from plasma via endocytosis that takes place as a result of binding to FcRn, these molecules are highly useful as pharmaceuticals.
  • Fc ⁇ RI, Fc ⁇ RIIa, Fc ⁇ RIIb, and Fc ⁇ RIIIa Fc ⁇ RI, Fc ⁇ RIIa, Fc ⁇ RIIb, and Fc ⁇ RIIIa
  • IgG IgG
  • Non-patent Document 9 Since binding activity of antibodies to activating Fc ⁇ receptors play an important role in an antibody's cytotoxicity, antibodies targeting membrane antigens, whose cytotoxicities have been enhanced by enhancing their binding activity to activating Fc ⁇ receptors have been developed to date (Non-patent Documents 10 and 11).
  • Non-patent Documents 12, 13, and 14 since binding activity to inhibitory Fc ⁇ receptor (Fc ⁇ RIIb) plays an important role in immunosuppression activity (Non-patent Documents 12, 13, and 14), agonistic activity (Non-Patent Documents 15 and 16), and such, antibodies targeting membrane antigens, which have enhanced binding activity to inhibitory Fc ⁇ receptors, are being studied (Non-Patent Documents 17 and 18).
  • Non-patent Document 19 Effects of antibodies that bind to soluble antigens on Fc ⁇ R binding have been examined mainly from the viewpoint of side effects. For example, it is known that the risk for thromboembolism increased in a group of patients who were administered bevacizumab, an antibody against VEGF (Non-patent Document 19). Similarly, thromboembolism has been observed in clinical development tests of antibodies against the CD40 ligand, and the clinical study was discontinued (Non-patent Document 20).
  • Fc ⁇ RIIa an activating Fc ⁇ receptor
  • Fc ⁇ RIIb an inhibitory Fc ⁇ receptor
  • both of the administered antibodies aggregate platelets via binding to Fc ⁇ RIIa on the platelets, and form blood clots as a result
  • Non-patent Documents 22 and 23 In patients with systemic lupus erythematosus which is an autoimmune disease, platelets are activated via an Fc ⁇ RIIa-dependent mechanism, and platelet activation has been reported to correlate with the severity of symptoms (Non-patent Document 24).
  • Non-Patent Document 25 an antibody that binds to a membrane antigen, whose Fc ⁇ RIIa-binding has been enhanced, enhances antibody-dependent cellular phagocytosis (ADCP) via macrophages and dendritic cells
  • ADCP antibody-dependent cellular phagocytosis
  • Non-patent Document 26 the binding activity towards activating and/or inhibitory Fc ⁇ receptors of antibodies targeting soluble antigens had not been known to have an effect on plasma kinetics of antibodies or antigens bound by the antibodies in the organisms administered with the antibodies.
  • an objective of the present invention is to suppress increase in plasma concentration of an antigen bound by an antigen-binding molecule by administering the antigen-binding molecule that has a binding activity towards a pathogenic antigen present in a soluble form in plasma, and also has a desired binding activity towards activating and/or inhibitory Fc ⁇ receptors.
  • Another objective of the present invention is to optimize the binding activity towards activating and/or inhibitory Fc ⁇ receptors of antigen-binding molecules against the disease-causing antigens present in a soluble form in plasma, and thereby optimize the suppression of the increase in plasma concentration of antigens bound by the antigen-binding molecules.
  • the present invention provides antigen-binding molecules comprising (i) an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, (ii) an Fc ⁇ -binding domain having Fc ⁇ RIIb-selective binding activity, and (iii) an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition, and methods for decreasing plasma concentration of the antigen as compared to before administering the antigen-binding molecule, which comprises the step of administering the molecule.
  • the present invention provides agents for decreasing plasma concentration of the antigen, which comprise an antigen-binding molecule comprising (i) an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, (ii) an Fc ⁇ -binding domain having Fc ⁇ RIIb-selective binding activity, and (iii) an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition.
  • an antigen-binding molecule comprising (i) an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, (ii) an Fc ⁇ -binding domain having Fc ⁇ RIIb-selective binding activity, and (iii) an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition.
  • compositions which comprise an antigen-binding molecule comprising (i) an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, (ii) an Fc ⁇ -binding domain having Fc ⁇ RIIb-selective binding activity, and (iii) an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition.
  • the present invention also provides uses of the antigen-binding molecule for decreasing plasma concentration of the antigen, wherein the molecule comprises (i) an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, (ii) an Fc ⁇ -binding domain having Fc ⁇ RIIb-selective binding activity, and (iii) an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition.
  • the present invention provides methods of producing and/or methods of screening for the antigen-binding molecules.
  • an antigen-binding molecule for eliminating antigen from plasma, wherein the antigen-binding molecule comprises an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, and an Fc region in which the amino acid at position 238 is Asp and the amino acid at position 271 is Gly as indicated by EU numbering; [2] the use of [1], wherein the Fc region has an amino acid substitution at at least one or more positions selected from the group consisting of 233, 234, 237, 264, 265, 266, 267, 268, 269, 272, 274, 296, 326, 327, 330, 331, 332, 333, 355, 356, 358, 396, 409, and 419 as indicated by EU numbering; [3] the use of [2], wherein the amino acids of the Fc region include any one or more of the following amino acids indicated by EU numbering: Asp at amino acid position 233; Tyr at amino acid position 234; Asp at amino acid position 237; I
  • the following phrases are used synonymously: “use of an antigen-binding molecule for eliminating antigen from plasma, wherein the antigen-binding molecule comprises an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, and an Fc region in which the amino acid at position 238 is Asp and the amino acid at position 271 is Gly as indicated by EU numbering”; “a method for treating a disease caused by an antigen, which comprises administering an antigen-binding molecule comprising an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, and an Fc region in which the amino acid at position 238 is Asp and the amino acid at position 271 is Gly as indicated by EU numbering”; “a pharmaceutical composition comprising an antigen-binding molecule which comprises an antigen-binding domain whose antigen-binding activity varies depending on ion concentration condition, and an Fc region in which the amino acid at position 238 is Asp and the amino acid at
  • FIG. 1 shows a non-limiting action mechanism for the elimination of soluble antigen from plasma by administering an antibody that binds to an antigen in an ion concentration-dependent manner and whose Fc ⁇ receptor binding is enhanced at a neutral pH as compared to existing neutralizing antibodies.
  • FIG. 2 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, which binds to human IL-6 receptor in a pH-dependent manner, or H54/L28-IgG1.
  • FIG. 3 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1 which binds to human IL-6 receptor in a pH-dependent manner, Fv4-IgG1-F760 which is an Fv4-IgG1 variant that lacks mouse Fc ⁇ R binding, Fv4-IgG1-F1022 which is an Fv4-IgG1 variant with enhanced mouse Fc ⁇ R binding, or Fv4-IgG1-Fuc which is an Fv4-IgG1 antibody with low fucose content.
  • FIG. 4 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1 or antigen-binding molecules comprising as the heavy chain, Fv4-IgG1-F1022 or Fv4-IgG1-F1093 which is a Fv4-IgG1-F1022 variant with improved FcRn binding in an acidic pH range.
  • FIG. 5 shows a concentration time course of the administered antigen-binding molecules in the plasma of human FcRn transgenic mice administered with Fv4-IgG1 or antigen-binding molecules comprising as the heavy chain, Fv4-IgG1-F1022 or Fv4-IgG1-F1093 which is a Fv4-IgG1-F1022 variant with improved FcRn binding in an acidic pH range.
  • FIG. 6 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1087 which is an Fv4-IgG1 variant with enhanced mouse Fc ⁇ R binding (in particular, enhanced mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding), and Fv4-IgG1-F1182 which is an Fv4-IgG1 variant with enhanced mouse Fc ⁇ R binding (in particular, enhanced mouse Fc ⁇ RI binding and mouse Fc ⁇ RIV binding).
  • FIG. 7 shows a concentration time course of the administered antigen-binding molecules in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1087, and Fv4-IgG1-F1180 and Fv4-IgG1-F1412 which are Fv4-IgG1-F1087 variants with improved FcRn binding in an acidic pH range.
  • FIG. 8 shows a concentration time course of the administered antigen-binding molecules in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1182, and Fv4-IgG1-F1181 which is an Fv4-IgG1-F1182 variant with improved FcRn binding in an acidic pH range.
  • FIG. 9 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1087, and Fv4-IgG1-F1180 and Fv4-IgG1-F1412 which are Fv4-IgG1-F1087 variants with improved FcRn binding in an acidic pH range.
  • FIG. 10 shows a time course of human IL-6 receptor concentration in the plasma of human FcRn transgenic mice administered with Fv4-IgG1, Fv4-IgG1-F1182, and Fv4-IgG1-F1181 which is an Fv4-IgG1-F1182 variant with improved FcRn binding in an acidic pH range.
  • FIG. 11 shows a time course of human IL-6 receptor concentration in the plasma of normal mice administered with Fv4-mIgG1, Fv4-mIgG1-mF44 which is an Fv4-mIgG1 variant with enhanced mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding, and Fv4-mIgG1-mF46 which is an Fv4-mIgG1 variant with further enhanced mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding.
  • FIG. 13 shows a time course of human IL-6 receptor concentration in the plasma of Fc receptor ⁇ chain-deficient mice administered with Fv4-mIgG1, Fv4-mIgG1-mF44 which is an Fv4-mIgG1 variant with enhanced mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding, and Fv4-mIgG1-mF46 which is an Fv4-mIgG1 variant with further enhanced mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding.
  • FIG. 14 shows a time course of human IL-6 receptor concentration in the plasma of Fc ⁇ RIIb-deficient mice administered with Fv4-mIgG1, Fv4-mIgG1-mF44 which is an Fv4-mIgG1 variant with enhanced mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding, and Fv4-mIgG1-mF46 which is an Fv4-mIgG1 variant with further enhanced mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding.
  • FIG. 15 shows a result of evaluating the platelet aggregation ability of the omalizumab-G1d-v3/IgE immune complex by platelet aggregation assay using platelets derived from donors with Fc ⁇ RIIa allotype (R/H).
  • FIG. 16 shows a result of evaluating the platelet aggregation ability of the omalizumab-G1d-v3/IgE immune complex by platelet aggregation assay using platelets derived from donors with Fc ⁇ RIIa allotype (H/H).
  • FIG. 18 shows a result of assessing the expression of active integrin on the membrane surface of washed platelets.
  • the black-filled area in the graph indicates a result of ADP stimulation after reaction with PBS.
  • the area that is not filled in the graph indicates a result of ADP stimulation after reaction with the immune complex.
  • FIG. 19 shows a graph in which the horizontal axis shows the relative value of Fc ⁇ RIIb-binding activity of each PD variant, and the vertical axis shows the relative value of Fc ⁇ RIIa type R-binding activity of each PD variant.
  • the value for the amount of binding of each PD variant to each Fc ⁇ R was divided by the value for the amount of binding of IL6R-F652/IL6R-L, which is a control antibody prior to introduction of the alteration (IL6R-F652, defined by SEQ ID NO: 61, is an antibody heavy chain comprising an altered Fc with substitution of Pro at position 238 (EU numbering) with Asp), to each Fc ⁇ R; and then the obtained value was multiplied by 100, and used as the relative binding activity value for each PD variant to each Fc ⁇ R.
  • the F652 plot in the figure shows the value for IL6R-F652/IL6R-L.
  • FIG. 20 shows a graph in which the vertical axis shows the relative value of Fc ⁇ RIIb-binding activity of variants produced by introducing each alteration into GpH7-B3 (SEQ ID NO: 63)/GpL16-k0 which does not have the P238D alteration, and the horizontal axis shows the relative value of Fc ⁇ RIIb-binding activity of variants produced by introducing each alteration into IL6R-F652 (SEQ ID NO: 61)/IL6R-L which has the P238D alteration.
  • Region B contains alterations that exhibit the effect of enhancing Fc ⁇ RIIb binding when introduced into GpH7-B3/GpL16-k0 which does not have P238D, but do not exhibit the effect of enhancing Fc ⁇ RIIb binding when introduced into IL6R-F652/IL6R-L which has P238D.
  • FIG. 22 shows an image of superimposing the crystal structure of the Fc(P238D)/Fc ⁇ RIIb extracellular region complex and the model structure of the Fc(WT)/Fc ⁇ RIIb extracellular region complex, with respect to the Fc ⁇ RIIb extracellular region and the Fc CH2 domain A by the least squares fitting based on the C ⁇ atom pair distances.
  • FIG. 23 shows comparison of the detailed structure around P238D after superimposing the crystal structure of the Fc(P238D)/Fc ⁇ RIIb extracellular region complex and the model structure of the Fc(WT)/Fc ⁇ RIIb extracellular region complex with respect to the only Fc CH2 domain A or the only Fc CH2 domain B by the least squares fitting based on the C ⁇ atom pair distances.
  • FIG. 24 shows that a hydrogen bond can be found between the main chain of Gly at position 237 (indicated by EU numbering) in Fc CH2 domain A, and Tyr at position 160 in Fc ⁇ RIIb in the crystal structure of the Fc(P238D)/Fc ⁇ RIIb extracellular region complex.
  • FIG. 25 shows that an electrostatic interaction can be found between Asp at position 270 (indicated by EU numbering) in Fc CH2 domain B, and Arg at position 131 in Fc ⁇ RIIb in the crystal structure of the Fc(P238D)/Fc ⁇ RIIb extracellular region complex.
  • FIG. 27 shows Glu at position 233 (indicated by EU numbering) in Fc Chain A and the surrounding residues in the extracellular region of Fc ⁇ RIIb in the crystal structure of the Fc(P238D)/Fc ⁇ RIIb extracellular region complex.
  • FIG. 28 shows Ala at position 330 (indicated by EU numbering) in Fc Chain A and the surrounding residues in the extracellular region of Fc ⁇ RIIb in the crystal structure of the Fc(P238D)/Fc ⁇ RIIb extracellular region complex.
  • FIG. 29 shows the structures of Pro at position 271 (EU numbering) of Fc Chain B after superimposing the crystal structures of the Fc(P238D)/Fc ⁇ RIIb extracellular region complex and the Fc(WT)/Fc ⁇ RIIIa extracellular region complex by the least squares fitting based on the C ⁇ atom pair distances with respect to Fc Chain B.
  • FIG. 30 shows an image of the Fc (P208)/Fc ⁇ RIIb extracellular region complex determined by X-ray crystal structure analysis.
  • domain A For each of the CH2 and CH3 domains in the Fc portion, those on the left side are referred to as domain A and those on the right side are referred to as domain B.
  • FIG. 31 shows comparison after superimposing the structures of Fc (P208)/Fc ⁇ RIIb extracellular region complex and Fc (WT)/Fc ⁇ RIIa extracellular region complex (PDB code: 3RY6) determined by X-ray crystal structure analysis with respect to the CH2 domain A of the Fc portion by the least squares fitting based on the C ⁇ atom pair distances.
  • the structure drawn with heavy line shows the Fc (P208)/Fc ⁇ RIIb extracellular region complex
  • the structure drawn with thin line indicates the structure of Fc (WT)/Fc ⁇ RIIa extracellular region complex. Only the CH2 domain A of the Fc portion is drawn for the Fc (WT)/Fc ⁇ RIIa extracellular region complex.
  • FIG. 32 shows in the X-ray crystal structure of the Fc (P208)/Fc ⁇ RIIb extracellular region complex, a detailed structure around Asp at position 237 (EU numbering) in the CH2 domain A of the Fc portion, which forms a hydrogen bond with Tyr at position 160 in Fc ⁇ RIIb at the main chain moiety.
  • FIG. 33 shows in the X-ray crystal structure of the Fc (P208)/Fc ⁇ RIIb extracellular region complex, the structure of amino acid residues around Asp at position 237 (EU numbering) in the CH2 domain A of the Fc portion, which forms a hydrogen bond with Tyr at position 160 in Fc ⁇ RIIb at the main chain moiety.
  • FIG. 34 shows comparison around the loop at positions 266 to 271 (EU numbering) after superimposing the X-ray crystal structures of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex shown in Example 10 and the Fc (P208)/Fc ⁇ RIIb extracellular region complex with respect to the CH2 domain B of the Fc portion by the least squares fitting based on the C ⁇ atom pair distances.
  • Fc (P208) has the H268D alteration at position 268 (EU numbering) and the P271G alteration at position 271 (EU numbering) in the loop.
  • FIG. 35 is a diagram showing the structure around Ser239 in the CH2 domain B of the Fc portion in the X-ray crystal structure of the Fc (P208)/Fc ⁇ RIIb extracellular region complex, along with the electron density with 2Fo-Fc coefficient determined by X-ray crystal structure analysis.
  • FIG. 36 shows comparison after superimposing the three-dimensional structures of the Fc (P208)/Fc ⁇ RIIaR extracellular region complex and Fc (P208)/Fc ⁇ RIIb extracellular region complex determined by X-ray crystal structure analysis by the least squares fitting based on the C ⁇ atom pair distances.
  • FIG. 37 shows comparison around Asp at position 237 (EU numbering) in the CH2 domain A of the Fc portion between the X-ray crystal structures of the Fc (P208)/Fc ⁇ RIIaR extracellular region complex and the Fc (P208)/Fc ⁇ RIIb extracellular region complex, along with the electron density with 2Fo-Fc coefficient determined by X-ray crystal structure analysis.
  • FIG. 38 shows comparison around Asp at position 237 (EU numbering) in the CH2 domain B of the Fc portion between the X-ray crystal structures of the Fc (P208)/Fc ⁇ RIIaR extracellular region complex and the Fc (P208)/Fc ⁇ RIIb extracellular region complex, along with the electron density with 2Fo-Fc coefficient determined by X-ray crystal structure analysis.
  • FIG. 39 shows comparison between the constant-region sequences of G1d and G4d.
  • the amino acids boxed with thick-frame indicate positions with different amino acid residues between G1d and G4d.
  • FIG. 40 shows the change in plasma antibody concentration of GA2-IgG1 and GA2-F1087 in normal mice.
  • FIG. 42 shows the change in plasma antibody concentration of 278-IgG1 and 278-F1087 in normal mice.
  • FIG. 43 shows the change in plasma hIgE (Asp6) concentration in C57BL/6J mice administered with 278-IgG1 and 278-F1087.
  • FIG. 44 shows a time course of anti-human IL-6 receptor mouse antibody concentration in the plasma of normal mice administered with Fv4-mIgG1 and Fv4-mIgG1-MB367 which is an Fv4-mIgG1 variant with enhanced mouse Fc ⁇ RIIb binding.
  • FIG. 45 shows a time course of soluble human IL-6 receptor concentration in the plasma of normal mice administered with Fv4-mIgG1 and Fv4-mIgG1-MB367 which is an Fv4-mIgG1 variant with enhanced mouse Fc ⁇ RIIb binding.
  • amino acids are described in one- or three-letter codes or both, for example, Ala/A, Leu/L, Arg/R, Lys/K, Asn/N, Met/M, Asp/D, Phe/F, Cys/C, Pro/P, Gln/Q, Ser/S, Glu/E, Thr/T, Gly/G, Trp/W, His/H, Tyr/Y, Ile/I, or Val/V.
  • amino acid alterations in the amino acid sequence of an antigen-binding molecule known methods such as site-directed mutagenesis methods (Kunkel et al. (Proc. Natl. Acad. Sci. USA (1985) 82, 488-492)) and overlap extension PCR may be appropriately employed. Additions, deletions, and/or substitutions of an amino acid are added appropriately by these known methods. Substituting amino acid residues means substituting an amino acid residue with another amino acid residue for the purpose of altering aspects such as the following (a) to (c):
  • Amino acid residues are classified into the following groups based on the properties of side chains included in their structures:
  • hydrophobic norleucine, Met, Ala, Val, Leu, and Ile
  • neutral hydrophilic Cys, Ser, Thr, Asn, and Gln
  • acidic Asp and Glu
  • basic His, Lys, and Arg
  • residues that affect the orientation of the chain Gly and Pro
  • aromatic Trp, Tyr, and Phe.
  • substitutions in the present invention may be conservative substitutions or non-conservative substitutions, or a combination of conservative and non-conservative substitutions.
  • substitutions in the present invention may be conservative substitutions or non-conservative substitutions, or a combination of conservative and non-conservative substitutions.
  • a plurality of known methods may be employed as amino acid alteration methods for substitution to non-native amino acids (Annu. Rev. Biophys. Biomol. Struct. (2006) 35, 225-249; and Proc. Natl. Acad. Sci. U.S.A. (2003) 100 (11), 6353-6357).
  • a cell-free translation system (Clover Direct (Protein Express)) containing a tRNA which has the non-native amino acid bound to a complementary amber suppressor tRNA of the UAG codon (amber codon), which is one of the stop codons, is suitably used.
  • an expression that uses one-letter amino-acid codes of the amino acid before alteration and the amino acid after the alteration before and after a number indicating a specific position, respectively, may be used appropriately as an expression for an amino acid alteration.
  • the alteration P238D which is used when substituting an amino acid of the Fc region included in an antibody constant region, expresses substitution of Pro at position 238 (according to EU numbering) with Asp. That is, the number shows the position of the amino acid according to EU numbering, the one-letter amino-acid code written before the number shows the amino acid before substitution, and the one-letter amino-acid code written after the number shows the amino acid after substitution.
  • the term “and/or” means a combination of the terms before and after the set phrase “and/or”, and includes every combination where “and” and “or” are suitably combined.
  • “the amino acids at positions 326, 328, and/or 428 are substituted” includes a variation of alterations of the following amino acids:
  • amino acid(s) at (a) position 326, (b) position 328, (c) position 428, (d) positions 326 and 328, (e) positions 326 and 428, (f) positions 328 and 428, and (g) positions 326, 328, and 428.
  • antigens are not particularly limited in their structure, as long as they comprise epitopes to which antigen-binding domains bind.
  • antigens can be inorganic or organic substances.
  • Antigens include, for example, the molecules below: 17-IA, 4-1BB, 4Dc, 6-keto-PGF1a, 8-iso-PGF2a, 8-oxo-dG, A1 adenosine receptor, A33, ACE, ACE-2, activin, activin A, activin AB, activin B, activin C, activin RIA, activin RIA ALK-2, activin RIB ALK-4, activin RITA, activin RIIB, ADAM, ADAM10, ADAM12, ADAM15, ADAM17/TACE, ADAMS, ADAMS, ADAMTS, ADAMTS4, ADAMTS5, addressin, aFGF, ALCAM, ALK, ALK-1, ALK-7, alpha-1-antitrypsin,
  • receptors are recited as examples of the above-mentioned antigens, when these receptors exist in soluble forms in biological fluids such as plasma, they can form complexes with the antigen-binding molecules of the present invention. Therefore, as long as the above-mentioned receptors exist in their soluble forms in biological fluids such as plasma, they may be used as antigens that may form complexes of the present invention by binding to an antigen-binding molecule of the present invention.
  • An example of a non-limiting embodiment of such a soluble receptor is soluble IL-6R, which is a protein consisting of the amino acids at positions 1 to 357 in the IL-6R polypeptide sequence of SEQ ID NO: 1 as described in Mullberg et al. (J. Immunol. (1994) 152 (10), 4958-4968).
  • Soluble antigens are recited as examples of the above-mentioned antigens, and the solutions in which the antigens exist are not limited. Soluble antigens may exist in biological fluids, or more specifically in all fluids filling the space between tissues and cells or vessels in organisms. In a non-limiting embodiment, the antigens to which antigen-binding molecules of the present invention bind may be present in extracellular fluids.
  • extracellular fluid is a general term for plasma, interstitial fluid, lymph, compact connective tissue, cerebrospinal fluid, spinal fluid, puncture fluid, synovial fluid, or such components in the bone and cartilage, alveolar fluid (bronchoalveolar lavage fluid), peritoneal fluid, pleural fluid, pericardial fluid, cyst fluid, aqueous humor (hydatoid), or such transcellular fluids (various fluids in the glandular cavities and fluids in the digestive tract cavity and other body cavity fluids produced as a result of active transport/secretory activities of cells).
  • alveolar fluid bronchoalveolar lavage fluid
  • peritoneal fluid pleural fluid
  • pericardial fluid cyst fluid
  • aqueous humor aqueous humor
  • Epitope means an antigenic determinant in an antigen, and refers to an antigen site to which the antigen-binding domain of an antigen-binding molecule disclosed herein binds.
  • the epitope can be defined according to its structure.
  • the epitope may be defined according to the antigen-binding activity of an antigen-binding molecule that recognizes the epitope.
  • the antigen is a peptide or polypeptide
  • the epitope can be specified by the amino acid residues forming the epitope.
  • the epitope is a sugar chain
  • the epitope can be specified by its specific sugar chain structure.
  • a linear epitope is an epitope that contains an epitope whose primary amino acid sequence is recognized. Such a linear epitope typically contains at least three and most commonly at least five, for example, about 8 to 10 or 6 to 20 amino acids in its specific sequence.
  • “conformational epitope” is an epitope in which the primary amino acid sequence containing the epitope is not the only determinant of the recognized epitope (for example, the primary amino acid sequence of a conformational epitope is not necessarily recognized by an epitope-defining antibody).
  • Conformational epitopes may contain a greater number of amino acids compared to linear epitopes.
  • a conformational epitope-recognizing antibody recognizes the three-dimensional structure of a peptide or protein. For example, when a protein molecule folds and forms a three-dimensional structure, amino acids and/or polypeptide main chains that form a conformational epitope become aligned, and the epitope is made recognizable by the antibody.
  • Methods for determining epitope conformations include, for example, X ray crystallography, two-dimensional nuclear magnetic resonance, site-specific spin labeling, and electron paramagnetic resonance, but are not limited thereto. See, for example, Epitope Mapping Protocols in Methods in Molecular Biology (1996), Vol. 66, Morris (ed.).
  • Examples of a method for assessing the epitope binding by a test antigen-binding molecule containing an IL-6R antigen-binding domain are described below. According to the examples below, methods for assessing the epitope binding by a test antigen-binding molecule containing an antigen-binding domain for an antigen other than IL-6R, can also be appropriately conducted.
  • test antigen-binding molecule containing an IL-6R antigen-binding domain recognizes a linear epitope in the IL-6R molecule can be confirmed for example as mentioned below.
  • a linear peptide comprising an amino acid sequence forming the extracellular domain of IL-6R is synthesized for the above purpose.
  • the peptide can be synthesized chemically, or obtained by genetic engineering techniques using a region encoding the amino acid sequence corresponding to the extracellular domain in an IL-6R cDNA represented by SEQ ID NO: 2. Then, a test antigen-binding molecule containing an IL-6R antigen-binding domain is assessed for its binding activity towards a linear peptide comprising the amino acid sequence forming the extracellular domain.
  • an immobilized linear peptide can be used as an antigen by ELISA to evaluate the binding activity of the antigen-binding molecule towards the peptide.
  • the binding activity towards a linear peptide can be assessed based on the level that the linear peptide inhibits the binding of the antigen-binding molecule to IL-6R-expressing cells. These tests can demonstrate the binding activity of the antigen-binding molecule towards the linear peptide.
  • test antigen-binding molecule containing an IL-6R antigen-binding domain recognizes a conformational epitope can be assessed as follows.
  • IL-6R-expressing cells are prepared for the above purpose.
  • a test antigen-binding molecule containing an IL-6R antigen-binding domain can be determined to recognize a conformational epitope when it strongly binds to IL-6R-expressing cells upon contact, but does not substantially bind to an immobilized linear peptide comprising an amino acid sequence forming the extracellular domain of IL-6R.
  • “not substantially bind” means that the binding activity is 80% or less, generally 50% or less, preferably 30% or less, and particularly preferably 15% or less compared to the binding activity towards cells expressing human IL-6R.
  • Methods for assaying the binding activity of a test antigen-binding molecule containing an IL-6R antigen-binding domain towards IL-6R-expressing cells include, for example, the methods described in Antibodies: A Laboratory Manual (Ed Harlow, David Lane, Cold Spring Harbor Laboratory (1988) 359-420). Specifically, the assessment can be performed based on the principle of ELISA or fluorescence activated cell sorting (FACS) using IL-6R-expressing cells as antigen.
  • FACS fluorescence activated cell sorting
  • the binding activity of a test antigen-binding molecule containing an IL-6R antigen-binding domain towards IL-6R-expressing cells can be assessed quantitatively by comparing the levels of signal generated by enzymatic reaction. Specifically, a test polypeptide complex is added to an ELISA plate onto which IL-6R-expressing cells are immobilized. Then, the test antigen-binding molecule bound to the cells is detected using an enzyme-labeled antibody that recognizes the test antigen-binding molecule.
  • a dilution series of a test antigen-binding molecule is prepared, and the antibody binding titer for IL-6R-expressing cells can be determined to compare the binding activity of the test antigen-binding molecule towards IL-6R-expressing cells.
  • test antigen-binding molecule The binding of a test antigen-binding molecule towards an antigen expressed on the surface of cells suspended in buffer or the like can be detected using a flow cytometer.
  • flow cytometers include, for example, the following devices:
  • FACSCaliburTM (all are trade names of BD Biosciences)
  • Preferable methods for assaying the binding activity of a test antigen-binding molecule containing an IL-6R antigen-binding domain towards an antigen include, for example, the following method. First, IL-6R-expressing cells are reacted with a test antigen-binding molecule, and then this is stained with an FITC-labeled secondary antibody that recognizes the antigen-binding molecule.
  • the test antigen-binding molecule is appropriately diluted with a suitable buffer to prepare the molecule at a desired concentration. For example, the molecule can be used at a concentration within the range of 10 ⁇ g/ml to 10 ng/ml. Then, the fluorescence intensity and cell count are determined using FACSCalibur (BD).
  • the fluorescence intensity obtained by analysis using the CELL QUEST Software (BD), i.e., the Geometric Mean value, reflects the quantity of antibody bound to cells. That is, the binding activity of a test antigen-binding molecule, which is represented by the quantity of the test antigen-binding molecule bound, can be determined by measuring the Geometric Mean value.
  • test antigen-binding molecule containing an IL-6R antigen-binding domain shares a common epitope with another antigen-binding molecule can be assessed based on the competition between the two molecules for the same epitope.
  • the competition between antigen-binding molecules can be detected by cross-blocking assay or the like.
  • the competitive ELISA assay is a preferred cross-blocking assay.
  • the IL-6R protein immobilized to the wells of a microtiter plate is pre-incubated in the presence or absence of a candidate competitor antigen-binding molecule, and then a test antigen-binding molecule is added thereto.
  • the quantity of test antigen-binding molecule bound to the IL-6R protein in the wells is indirectly correlated with the binding ability of a candidate competitor antigen-binding molecule that competes for the binding to the same epitope. That is, the greater the affinity of the competitor antigen-binding molecule for the same epitope, the lower the binding activity of the test antigen-binding molecule towards the IL-6R protein-coated wells.
  • the quantity of the test antigen-binding molecule bound to the wells via the IL-6R protein can be readily determined by labeling the antigen-binding molecule in advance.
  • a biotin-labeled antigen-binding molecule is measured using an avidin/peroxidase conjugate and appropriate substrate.
  • cross-blocking assay that uses enzyme labels such as peroxidase is called competitive ELISA assay.
  • the antigen-binding molecule can also be labeled with other labeling substances that enable detection or measurement. Specifically, radiolabels, fluorescent labels, and such are known.
  • the candidate competitor antigen-binding molecule can block the binding by a test antigen-binding molecule containing an IL-6R antigen-binding domain by at least 20%, preferably at least 20 to 50%, and more preferably at least 50% compared to the binding activity in a control experiment conducted in the absence of the competitor antigen-binding molecule complex
  • the test antigen-binding molecule is determined to substantially bind to the same epitope bound by the competitor antigen-binding molecule, or compete for the binding to the same epitope.
  • test and control antigen-binding molecules share a common epitope can be assessed by comparing the binding activities of the two antigen-binding molecules towards a peptide prepared by introducing amino acid mutations into the peptide forming the epitope.
  • the binding activities of test and control antigen-binding molecules towards a linear peptide into which a mutation is introduced are compared in the above ELISA format.
  • the binding activity towards the mutant peptide bound to a column can be determined by flowing test and control antigen-binding molecules in the column, and then quantifying the antigen-binding molecule eluted in the elution solution.
  • Methods for adsorbing a mutant peptide to a column for example, in the form of a GST fusion peptide, are known.
  • test and control antigen-binding molecules share a common epitope can be assessed by the following method.
  • IL-6R-expressing cells and cells expressing IL-6R with a mutation introduced into the epitope are prepared.
  • the test and control antigen-binding molecules are added to a cell suspension prepared by suspending these cells in an appropriate buffer such as PBS.
  • the cell suspensions are appropriately washed with a buffer, and an FITC-labeled antibody that recognizes the test and control antigen-binding molecules is added thereto.
  • the fluorescence intensity and number of cells stained with the labeled antibody are determined using FACSCalibur (BD).
  • the test and control antigen-binding molecules are appropriately diluted using a suitable buffer, and used at desired concentrations. For example, they may be used at a concentration within the range of 10 ⁇ g/ml to 10 ng/ml.
  • the fluorescence intensity determined by analysis using the CELL QUEST Software (BD), i.e., the Geometric Mean value reflects the quantity of labeled antibody bound to cells. That is, the binding activities of the test and control antigen-binding molecules, which are represented by the quantity of labeled antibody bound, can be determined by measuring the Geometric Mean value.
  • an antigen-binding molecule does “not substantially bind to cells expressing mutant IL-6R” can be assessed, for example, by the following method.
  • the test and control antigen-binding molecules bound to cells expressing mutant IL-6R are stained with a labeled antibody.
  • the fluorescence intensity of the cells is determined.
  • FACSCalibur is used for fluorescence detection by flow cytometry
  • the determined fluorescence intensity can be analyzed using the CELL QUEST Software.
  • the comparison value ( ⁇ Geo-Mean) can be calculated according to the following formula to determine the ratio of increase in fluorescence intensity as a result of the binding by the antigen-binding molecule.
  • the Geometric Mean comparison value ( ⁇ Geo-Mean value for the mutant IL-6R molecule) determined by the above analysis, which reflects the quantity of a test antigen-binding molecule bound to cells expressing mutant IL-6R, is compared to the ⁇ Geo-Mean comparison value that reflects the quantity of the test antigen-binding molecule bound to IL-6R-expressing cells.
  • concentrations of the test antigen-binding molecule used to determine the ⁇ Geo-Mean comparison values for IL-6R-expressing cells and cells expressing mutant IL-6R are particularly preferably adjusted to be equal or substantially equal.
  • An antigen-binding molecule that has been confirmed to recognize an epitope in IL-6R is used as a control antigen-binding molecule.
  • the test antigen-binding molecule for cells expressing mutant IL-6R is smaller than the ⁇ Geo-Mean comparison value of the test antigen-binding molecule for IL-6R-expressing cells by at least 80%, preferably 50%, more preferably 30%, and particularly preferably 15%, then the test antigen-binding molecule “does not substantially bind to cells expressing mutant IL-6R”.
  • the formula for determining the Geo-Mean (Geometric Mean) value is described in the CELL QUEST Software User's Guide (BD biosciences). When the comparison shows that the comparison values are substantially equivalent, the epitope for the test and control antigen-binding molecules can be determined to be the same.
  • an “antigen-binding domain” may be of any structure as long as it binds to an antigen of interest.
  • Such domains preferably include, for example:
  • a domain which is contained in the in vivo cell membrane protein Avimer (WO 2004/044011, WO 2005/040229); Adnectin containing the 10Fn3 domain which binds to the protein moiety of fibronectin, a glycoprotein expressed on cell membrane (WO 2002/032925); Affibody which is composed of a 58-amino acid three-helix bundle based on the scaffold of the IgG-binding domain of Protein A (WO 1995/001937); Designed Ankyrin Repeat proteins (DARPins) which are a region exposed on the molecular surface of ankyrin repeats (AR) having a structure in which a subunit consisting of a turn comprising 33 amino acid residues, two antiparallel helices, and a loop is repeatedly stacked (WO 2002/020565); Anticalins and such, which are domains consisting of four loops that support one side of a barrel structure composed of eight circularly
  • Preferred antigen-binding domains of the present invention include, for example, those having antibody heavy-chain and light-chain variable regions.
  • Preferred examples of antigen-binding domains include “single chain Fv (scFv)”, “single chain antibody”, “Fv”, “single chain Fv 2 (scFv2)”, “Fab”, and “F(ab′)2”.
  • the antigen-binding domains of antigen-binding molecules of the present invention can bind to an identical epitope.
  • Such epitope can be present, for example, in a protein comprising the amino acid sequence of SEQ ID NO: 1.
  • each of the antigen-binding domains of antigen-binding molecules of the present invention can bind to a different epitope.
  • the different epitope can be present in, for example, a protein comprising the amino acid sequence of SEQ ID NO: 1.
  • the term “specific” means that one of the molecules that specifically binds to does not substantially bind to molecules other than its single or plurality of binding partner molecule(s).
  • “does not substantially bind” refers to showing 80% or less, generally 50% or less, preferably 30% or less and particularly preferably 15% or less binding activity to molecules other than the binding partner molecules compared to the binding activity towards the partner molecule(s), as described in the above-mentioned section on binding activity.
  • “specific” is also used when an antigen-binding domain is specific to a particular epitope among multiple epitopes in an antigen. When an epitope bound by an antigen-binding domain is contained in multiple different antigens, antigen-binding molecules containing the antigen-binding domain can bind to various antigens that have the epitope.
  • a pharmaceutical composition comprising as an active ingredient an antigen-binding molecule having antigen-neutralizing activity
  • the antigen-binding molecule comprises (i) an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, (ii) an Fc ⁇ -binding domain having Fc ⁇ RIIb-selective binding activity, and (iii) an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition.
  • neutralizing activity refers to activity of inhibiting the biological activity of a ligand, such as viruses and toxins, having biological activity on cells.
  • substances having neutralizing activity refer to substances that bind to the ligand or the receptor to which the ligand binds, and inhibits the binding between the ligand and the receptor. Receptors blocked from binding with the ligand by the neutralizing activity will not be able to exhibit biological activity through this receptor.
  • the antigen-binding molecule is an antibody
  • such an antibody having neutralizing activity is generally called a neutralizing antibody.
  • Neutralizing activity of a test substance may be measured by comparing the biological activity in the presence of a ligand between when the test substance is present and absent.
  • major possible ligands for the IL-6 receptor preferably include IL-6 as shown in SEQ ID NO: 3.
  • the IL-6 receptor which is an I-type membrane protein with its amino terminus forming the extracellular domain, forms a hetero-tetramer with a gp130 receptor which has been induced to dimerize by IL-6 (Heinrich et al. (Biochem. J. (1998) 334, 297-314)). Formation of the heterotetramer activates Jak which is associated with the gp130 receptor. Jak undergoes autophosphorylation and phosphorylates the receptor.
  • the phosphorylation site of the receptor and Jak serves as a binding site for SH2-carrying molecules belonging to the Stat family such as Stat3; MAP kinase; PI3/Akt; and other SH2-carrying proteins and adapters.
  • Stat bound to the gp130 receptor is phosphorylated by Jak.
  • the phosphorylated Stat dimerizes and moves into the nucleus, and regulates the transcription of target genes. Jak or Stat can also be involved in signal cascades via receptors of other classes. Deregulated IL-6 signal cascades are observed in inflammation and pathological conditions of autoimmune diseases, and cancers such as prostate cancer and multiple myeloma.
  • Stat3 which may act as an oncogene is constitutively activated in many cancers.
  • Such intracellular signaling cascades are different for each cell type; therefore, appropriate target molecules can be determined for each target cell of interest, and are not limited to the above-mentioned factors.
  • Neutralization activity can be evaluated by measuring the activation of in vivo signaling.
  • the activation of in vivo signaling can be detected by using as an index the action of inducing the transcription of a target gene that exists downstream of the in vivo signaling cascade. Change in the transcription activity of the target gene can be detected by the principle of reporter assays.
  • a reporter gene such as green fluorescence protein (GFP) or luciferase is placed downstream of a promoter region or a transcription factor of the target gene, its reporter activity is measured, and thereby change in the transcription activity can be measured as the reporter activity.
  • GFP green fluorescence protein
  • kits for measuring the activation of in vivo signaling can be used appropriately (for example, Mercury Pathway Profiling Luciferase System (Clontech)).
  • the neutralization activity of antigen-binding molecules can be evaluated by measuring the proliferation activity of target cells.
  • the inhibitory effect on the proliferation of such cells based on the neutralizing activity of an anti-HB-EGF antibody can be suitably evaluated or measured by the following methods:
  • a method of measuring the incorporation of [ 3 H]-labeled thymidine added to the medium by viable cells as an index of DNA replication ability is used.
  • a dye exclusion method in which the ability of a cell to exclude a dye such as trypan blue from the cell is measured under the microscope, and the MTT method are used.
  • the latter method makes use of the ability of viable cells to convert MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), which is a tetrazolium salt, to a blue formazan product.
  • MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide
  • a test antibody is added as well as a ligand to the culture solution of a test cell, and after a certain period of time, the MTT solution is added to the culture solution, and this is left to stand for a while for incorporation of MTT into the cell.
  • MTT which is a yellow compound
  • succinate dehydrogenase in the mitochondria of the cell.
  • absorbance is measured and used as an index for the number of viable cells.
  • reagents such as MTS, XTT, WST-1, and WST-8 are also commercially available (Nacalai Tesque, and such) and can be suitably used.
  • a binding antibody which is of the same isotype as the anti-HB-EGF antibody but does not have the cell proliferation inhibitory activity can be used as a control antibody in the same manner as the anti-HB-EGF antibody, and the activity can be determined when the anti-HB-EGF antibody shows stronger cell proliferation inhibitory activity than the control antibody.
  • Cells that can be preferably used for evaluating the activity include, for example, cells promoted to proliferate by HB-EGF such as the ovarian cancer cell line RMG-1, and mouse Ba/F3 cells which have been transformed by a vector for expressing a gene encoding hEGFR/mG-CSFR, which is a fusion protein in which the extracellular domain of human EGFR is fused in frame with the intracellular domain of the mouse G-CSF receptor.
  • HB-EGF such as the ovarian cancer cell line RMG-1
  • mouse Ba/F3 cells which have been transformed by a vector for expressing a gene encoding hEGFR/mG-CSFR, which is a fusion protein in which the extracellular domain of human EGFR is fused in frame with the intracellular domain of the mouse G-CSF receptor.
  • antibody refers to a natural immunoglobulin or an immunoglobulin produced by partial or complete synthesis.
  • Antibodies can be isolated from natural sources such as naturally-occurring plasma and serum, or culture supernatants of antibody-producing hybridomas. Alternatively, antibodies can be partially or completely synthesized using techniques such as genetic recombination.
  • Preferred antibodies include, for example, antibodies of an immunoglobulin isotype or subclass belonging thereto.
  • Known human immunoglobulins include antibodies of the following nine classes (isotypes): IgG1, IgG2, IgG3, IgG4, IgA1, IgA2, IgD, IgE, and IgM.
  • antibodies of the present invention include IgG1, IgG2, IgG3, and IgG4.
  • a number of allotype sequences of human IgG1, human IgG2, human IgG3, and human IgG4 constant regions due to gene polymorphisms are described in “Sequences of proteins of immunological interest”, NIH Publication No. 91-3242. Any of such sequences may be used in the present invention.
  • the amino acid sequence at positions 356 to 358 as indicated by EU numbering may be DEL or EEM.
  • Several allotype sequences due to genetic polymorphisms have been described in “Sequences of proteins of immunological interest”, NIH Publication No. 91-3242 for the human IgK (Kappa) constant region and human Ig ⁇ , (Lambda) constant region, and any of the sequences may be used in the present invention.
  • Anti-IL-6R antibodies can be obtained as polyclonal or monoclonal antibodies using known methods.
  • the anti-IL-6R antibodies preferably produced are monoclonal antibodies derived from mammals.
  • Such mammal-derived monoclonal antibodies include antibodies produced by hybridomas or host cells transformed with an expression vector carrying an antibody gene by genetic engineering techniques.
  • “Humanized antibodies” or “chimeric antibodies” are included in the monoclonal antibodies of the present invention.
  • Monoclonal antibody-producing hybridomas can be produced using known techniques, for example, as described below. Specifically, mammals are immunized by conventional immunization methods using an IL-6R protein as a sensitizing antigen. Resulting immune cells are fused with known parental cells by conventional cell fusion methods. Then, hybridomas producing an anti-IL-6R antibody can be selected by screening for monoclonal antibody-producing cells using conventional screening methods.
  • IL-6R gene whose nucleotide sequence is disclosed in SEQ ID NO: 2 can be expressed to produce an IL-6R protein shown in SEQ ID NO: 1, which will be used as a sensitizing antigen for antibody preparation. That is, a gene sequence encoding IL-6R is inserted into a known expression vector, and appropriate host cells are transformed with this vector. The desired human IL-6R protein is purified from the host cells or their culture supernatants by known methods.
  • soluble IL-6R In order to obtain soluble IL-6R from culture supernatants, for example, a protein consisting of the amino acids at positions 1 to 357 in the IL-6R polypeptide sequence of SEQ ID NO: 1, such as described in Mullberg et al. (J. Immunol. (1994) 152 (10), 4958-4968), is expressed as a soluble IL-6R, instead of the IL-6R protein of SEQ ID NO: 1. Purified native IL-6R protein can also be used as a sensitizing antigen.
  • the purified IL-6R protein can be used as a sensitizing antigen for immunization of mammals.
  • a partial IL-6R peptide may also be used as a sensitizing antigen.
  • a partial peptide can be prepared by chemical synthesis based on the amino acid sequence of human IL-6R, or by inserting a partial IL-6R gene into an expression vector for expression.
  • a partial peptide can be produced by degrading an IL-6R protein with a protease.
  • the length and region of the partial IL-6R peptide are not limited to particular embodiments. A preferred region can be arbitrarily selected from the amino acid sequence at amino acid positions 20 to 357 in the amino acid sequence of SEQ ID NO: 1.
  • the number of amino acids forming a peptide to be used as a sensitizing antigen is preferably at least five or more, six or more, or seven or more. More specifically, a peptide of 8 to 50 residues, more preferably 10 to 30 residues can be used as a sensitizing antigen.
  • a fusion protein prepared by fusing a desired partial polypeptide or peptide of the IL-6R protein with a different polypeptide.
  • antibody Fc fragments and peptide tags are preferably used to produce fusion proteins to be used as sensitizing antigens.
  • Vectors for expression of such fusion proteins can be constructed by fusing in frame genes encoding two or more desired polypeptide fragments and inserting the fusion gene into an expression vector as described above. Methods for producing fusion proteins are described in Molecular Cloning 2nd ed. (Sambrook, J et al., Molecular Cloning 2nd ed., 9.47-9.58 (1989) Cold Spring Harbor Lab. Press). Methods for preparing IL-6R to be used as a sensitizing antigen, and immunization methods using IL-6R are specifically described in WO 2003/000883, WO 2004/022754, WO 2006/006693, and such.
  • mammals to be immunized with the sensitizing antigen there is no particular limitation on the mammals to be immunized with the sensitizing antigen. However, it is preferable to select the mammals by considering their compatibility with the parent cells to be used for cell fusion. In general, rodents such as mice, rats, and hamsters, rabbits, and monkeys are preferably used.
  • the above animals are immunized with a sensitizing antigen by known methods.
  • Generally performed immunization methods include, for example, intraperitoneal or subcutaneous injection of a sensitizing antigen into mammals.
  • a sensitizing antigen is appropriately diluted with PBS (Phosphate-Buffered Saline), physiological saline, or the like.
  • a conventional adjuvant such as Freund's complete adjuvant is mixed with the antigen, and the mixture is emulsified.
  • the sensitizing antigen is administered to a mammal several times at 4- to 21-day intervals.
  • Appropriate carriers may be used in immunization with the sensitizing antigen.
  • sensitizing antigen peptide when a low-molecular-weight partial peptide is used as the sensitizing antigen, it is sometimes desirable to couple the sensitizing antigen peptide to a carrier protein such as albumin or keyhole limpet hemocyanin for immunization.
  • a carrier protein such as albumin or keyhole limpet hemocyanin for immunization.
  • hybridomas producing a desired antibody can be prepared using DNA immunization as mentioned below.
  • DNA immunization is an immunization method that confers immunostimulation by expressing a sensitizing antigen in an animal immunized as a result of administering a vector DNA constructed to allow expression of an antigen protein-encoding gene in the animal.
  • DNA immunization is expected to be superior in that:
  • a DNA expressing an IL-6R protein is administered to an animal to be immunized.
  • the IL-6R-encoding DNA can be synthesized by known methods such as PCR.
  • the obtained DNA is inserted into an appropriate expression vector, and then this is administered to an animal to be immunized.
  • Preferably used expression vectors include, for example, commercially-available expression vectors such as pcDNA3.1.
  • Vectors can be administered to an organism using conventional methods. For example, DNA immunization is performed by using a gene gun to introduce expression vector-coated gold particles into cells in the body of an animal to be immunized.
  • Antibodies that recognized IL-6R can also be produced by the methods described in WO 2003/104453.
  • IL-6R-binding antibody After immunizing a mammal as described above, an increase in the titer of an IL-6R-binding antibody is confirmed in the serum. Then, immune cells are collected from the mammal, and then subjected to cell fusion. In particular, splenocytes are preferably used as immune cells.
  • a mammalian myeloma cell is used as a cell to be fused with the above-mentioned immune cells.
  • the myeloma cells preferably comprise a suitable selection marker for screening.
  • a selection marker confers characteristics to cells for their survival (or death) under a specific culture condition.
  • Hypoxanthine-guanine phosphoribosyltransferase deficiency hereinafter abbreviated as HGPRT deficiency
  • TK deficiency thymidine kinase deficiency
  • HAT-sensitive cells cannot synthesize DNA in a HAT selection medium, and are thus killed. However, when the cells are fused with normal cells, they can continue DNA synthesis using the salvage pathway of the normal cells, and therefore they can grow even in the HAT selection medium.
  • HGPRT-deficient and TK-deficient cells can be selected in a medium containing 6-thioguanine, 8-azaguanine (hereinafter abbreviated as 8AG), or 5′-bromodeoxyuridine, respectively.
  • 8AG 8-azaguanine
  • 5′-bromodeoxyuridine 5′-bromodeoxyuridine
  • Normal cells are killed because they incorporate these pyrimidine analogs into their DNA.
  • cells that are deficient in these enzymes can survive in the selection medium, since they cannot incorporate these pyrimidine analogs.
  • a selection marker referred to as G418 resistance provided by the neomycin-resistant gene confers resistance to 2-deoxystreptamine antibiotics (gentamycin analogs).
  • gentamycin analogs gentamycin analogs.
  • myeloma cells that are suitable for cell fusion are known.
  • myeloma cells including the following cells can be preferably used:
  • Cell fusions between the immunocytes and myeloma cells are essentially carried out using known methods, for example, a method by Kohler and Milstein et al. (Methods Enzymol. (1981) 73: 3-46).
  • cell fusion can be carried out, for example, in a conventional culture medium in the presence of a cell fusion-promoting agent.
  • fusion-promoting agents include, for example, polyethylene glycol (PEG) and Sendai virus (HVJ).
  • PEG polyethylene glycol
  • HVJ Sendai virus
  • an auxiliary substance such as dimethyl sulfoxide is also added to improve fusion efficiency.
  • the ratio of immune cells to myeloma cells may be determined at one's own discretion, preferably, for example, one myeloma cell for every one to ten immunocytes.
  • Culture media to be used for cell fusions include, for example, media that are suitable for the growth of myeloma cell lines, such as RPMI1640 medium and MEM medium, and other conventional culture medium used for this type of cell culture.
  • serum supplements such as fetal calf serum (FCS) may be preferably added to the culture medium.
  • a PEG solution for example, the average molecular weight is about 1,000 to 6,000
  • a concentration of generally 30% to 60% w/v.
  • This is gently mixed to produce desired fusion cells (hybridomas).
  • an appropriate culture medium mentioned above is gradually added to the cells, and this is repeatedly centrifuged to remove the supernatant.
  • the hybridomas thus obtained can be selected by culture using a conventional selective medium, for example, HAT medium (a culture medium containing hypoxanthine, aminopterin, and thymidine).
  • HAT medium a culture medium containing hypoxanthine, aminopterin, and thymidine.
  • Cells other than the desired hybridomas can be killed by continuing culture in the above HAT medium for a sufficient period of time (typically, the period is several days to several weeks). Then, hybridomas producing the desired antibody are screened and singly cloned by conventional limiting dilution methods.
  • the hybridomas thus obtained can be selected using a selection medium based on the selection marker possessed by the myeloma used for cell fusion.
  • HGPRT- or TK-deficient cells can be selected by culture using the HAT medium (a culture medium containing hypoxanthine, aminopterin, and thymidine).
  • HAT medium a culture medium containing hypoxanthine, aminopterin, and thymidine.
  • Desired antibodies can be preferably selected and singly cloned by screening methods based on known antigen/antibody reaction.
  • an IL-6R-binding monoclonal antibody can bind to IL-6R expressed on the cell surface.
  • Such a monoclonal antibody can be screened by fluorescence activated cell sorting (FACS).
  • FACS is a system that assesses the binding of an antibody to cell surface by analyzing cells contacted with a fluorescent antibody using laser beam, and measuring the fluorescence emitted from individual cells.
  • IL-6R-expressing cells are first prepared.
  • Cells preferably used for screening are mammalian cells in which IL-6R is forcedly expressed.
  • the activity of an antibody to bind to cell-surface IL-6R can be selectively detected using non-transformed mammalian cells as host cells.
  • hybridomas producing an anti-IL-6R monoclonal antibody can be isolated by selecting hybridomas that produce an antibody which binds to cells forced to express IL-6R, but not to host cells.
  • the activity of an antibody to bind to immobilized IL-6R-expressing cells can be assessed based on the principle of ELISA.
  • IL-6R-expressing cells are immobilized to the wells of an ELISA plate.
  • Culture supernatants of hybridomas are contacted with the immobilized cells in the wells, and antibodies that bind to the immobilized cells are detected.
  • antibodies bound to the cells can be detected using an anti-mouse immunoglobulin antibody.
  • Hybridomas producing a desired antibody having the antigen-binding ability are selected by the above screening, and they can be cloned by a limiting dilution method or the like.
  • Monoclonal antibody-producing hybridomas thus prepared can be passaged in a conventional culture medium, and stored in liquid nitrogen for a long period.
  • the above hybridomas are cultured by a conventional method, and desired monoclonal antibodies can be prepared from the culture supernatants. Alternatively, the hybridomas are administered to and grown in compatible mammals, and monoclonal antibodies are prepared from the ascites.
  • the former method is suitable for preparing antibodies with high purity.
  • Antibodies encoded by antibody genes that are cloned from antibody-producing cells such as the above hybridomas can also be preferably used.
  • a cloned antibody gene is inserted into an appropriate vector, and this is introduced into a host to express the antibody encoded by the gene.
  • Methods for isolating antibody genes, inserting the genes into vectors, and transforming host cells have already been established, for example, by Vandamme et al. (Eur. J. Biochem. (1990) 192(3), 767-775). Methods for producing recombinant antibodies are also known as described below.
  • a cDNA encoding the variable region (V region) of an anti-IL-6R antibody is prepared from hybridoma cells expressing the anti-IL-6R antibody.
  • total RNA is first extracted from hybridomas. Methods used for extracting mRNAs from cells include, for example:
  • Extracted mRNAs can be purified using the mRNA Purification Kit (GE Healthcare Bioscience) or such. Alternatively, kits for extracting total mRNA directly from cells, such as the QuickPrep mRNA Purification Kit (GE Healthcare Bioscience), are also commercially available. mRNAs can be prepared from hybridomas using such kits. cDNAs encoding the antibody V region can be synthesized from the prepared mRNAs using a reverse transcriptase. cDNAs can be synthesized using the AMV Reverse Transcriptase First-strand cDNA Synthesis Kit (Seikagaku Co.) or such. Furthermore, the SMART RACE cDNA Amplification Kit (Clontech) and the PCR-based 5′-RACE method (Proc.
  • the cDNA fragment of interest is purified from the resulting PCR product, and then this is ligated to a vector DNA.
  • a recombinant vector is thus constructed, and introduced into E. coli or such. After colony selection, the desired recombinant vector can be prepared from the colony-forming E. coli . Then, whether the recombinant vector has the cDNA nucleotide sequence of interest is tested by a known method such as the dideoxy nucleotide chain termination method.
  • the 5′-RACE method which uses primers to amplify the variable region gene is conveniently used for isolating the gene encoding the variable region.
  • a 5′-RACE cDNA library is constructed by cDNA synthesis using RNAs extracted from hybridoma cells as a template.
  • a commercially available kit such as the SMART RACE cDNA Amplification Kit is appropriately used to synthesize the 5′-RACE cDNA library.
  • the antibody gene is amplified by PCR using the prepared 5′-RACE cDNA library as a template.
  • Primers for amplifying the mouse antibody gene can be designed based on known antibody gene sequences.
  • the nucleotide sequences of the primers vary depending on the immunoglobulin subclass. Therefore, it is preferable that the subclass is determined in advance using a commercially available kit such as the Iso Strip Mouse Monoclonal Antibody Isotyping Kit (Roche Diagnostics).
  • primers that allow amplification of genes encoding ⁇ 1, ⁇ 2a, ⁇ 2b, and ⁇ 3 heavy chains and ⁇ and ⁇ light chains are used to isolate mouse IgG-encoding genes.
  • a primer that anneals to a constant region site close to the variable region is used as a 3′-side primer to amplify an IgG variable region gene.
  • a primer attached to a 5′ RACE cDNA library construction kit is used as a 5′-side primer.
  • PCR products thus amplified are used to reshape immunoglobulins composed of a combination of heavy and light chains.
  • a desired antibody can be selected using the IL-6R-binding activity of a reshaped immunoglobulin as an indicator. For example, when the objective is to isolate an antibody against IL-6R, it is more preferred that the binding of the antibody to IL-6R is specific.
  • An IL-6R-binding antibody can be screened, for example, by the following steps:
  • Methods for detecting the binding of an antibody to IL-6R-expressing cells are known. Specifically, the binding of an antibody to IL-6R-expressing cells can be detected by the above-described techniques such as FACS Immobilized samples of IL-6R-expressing cells are appropriately used to assess the binding activity of an antibody.
  • Preferred antibody screening methods that use the binding activity as an indicator also include panning methods using phage vectors. Screening methods using phage vectors are advantageous when the antibody genes are isolated from heavy-chain and light-chain subclass libraries from a polyclonal antibody-expressing cell population. Genes encoding the heavy-chain and light-chain variable regions can be linked by an appropriate linker sequence to form a single-chain Fv (scFv). Phages presenting scFv on their surface can be produced by inserting a gene encoding scFv into a phage vector. The phages are contacted with an antigen of interest. Then, a DNA encoding scFv having the binding activity of interest can be isolated by collecting phages bound to the antigen. This process can be repeated as necessary to enrich scFv having the binding activity of interest.
  • scFv single-chain Fv
  • the cDNA is digested with restriction enzymes that recognize the restriction sites introduced into both ends of the cDNA.
  • Preferred restriction enzymes recognize and cleave a nucleotide sequence that occurs in the nucleotide sequence of the antibody gene at a low frequency.
  • a restriction site for an enzyme that produces a sticky end is preferably introduced into a vector to insert a single-copy digested fragment in the correct orientation.
  • the cDNA encoding the V region of the anti-IL-6R antibody is digested as described above, and this is inserted into an appropriate expression vector to construct an antibody expression vector.
  • a chimeric antibody means that the origin of the constant region is different from that of the variable region.
  • human-human allochimeric antibodies are included in the chimeric antibodies of the present invention.
  • a chimeric antibody expression vector can be constructed by inserting the above V region gene into an expression vector that already has the constant region. Specifically, for example, a recognition sequence for a restriction enzyme that excises the above V region gene can be appropriately placed on the 5′ side of an expression vector carrying a DNA encoding a desired antibody constant region.
  • a chimeric antibody expression vector is constructed by fusing in frame the two genes digested with the same combination of restriction enzymes.
  • antibody genes are inserted into an expression vector so that the genes are expressed under the control of an expression regulatory region.
  • the expression regulatory region for antibody expression includes, for example, enhancers and promoters.
  • an appropriate signal sequence may be attached to the amino terminus so that the expressed antibody is secreted to the outside of cells.
  • a peptide having the amino acid sequence MGWSCIILFLVATATGVHS (SEQ ID NO: 4) are used as a signal sequence.
  • other appropriate signal sequences may be attached.
  • the expressed polypeptide is cleaved at the carboxyl terminus of the above sequence, and the resulting polypeptide is secreted to the outside of cells as a mature polypeptide.
  • appropriate host cells are transformed with the expression vector, and recombinant cells expressing the anti-IL-6R antibody-encoding DNA are obtained.
  • DNAs encoding the antibody heavy chain (H chain) and light chain (L chain) are separately inserted into different expression vectors to express the antibody gene.
  • An antibody molecule having the H and L chains can be expressed by co-transfecting the same host cell with vectors into which the H-chain and L-chain genes are respectively inserted.
  • host cells can be transformed with a single expression vector into which DNAs encoding the H and L chains are inserted (see WO 1994/011523).
  • eukaryotic cells used as host cells include animal cells, plant cells, and fungal cells.
  • the animal cells include, for example, the following cells.
  • mammalian cells CHO (Chinese hamster ovary cell line), COS (Monkey kidney cell line), myeloma (Sp2/O, NS0, and such), BHK (baby hamster kidney cell line), Hela, Vero, HEK293 (human embryonic kidney cell line with sheared adenovirus (Ad)5 DNA), Freestyle293, PER.C6 cell (human embryonic retinal cell line transformed with the Adenovirus Type 5 (Ad5) E1A and E1B genes), and such (Current Protocols in Protein Science (May, 2001, Unit 5.9, Table 5.9.1)); (2) amphibian cells: Xenopus oocytes , or such; and (3) insect cells: sf9, sf21, Tn5, or such.
  • Nicotiana tabacum an antibody gene expression system using cells derived from the Nicotiana genus such as Nicotiana tabacum is known. Callus cultured cells can be appropriately used to transform plant cells.
  • antibody gene expression systems that utilize prokaryotic cells are also known.
  • E. coli cells E. coli cells, Bacillus subtilis cells, and such can suitably be utilized in the present invention.
  • Expression vectors carrying the antibody genes of interest are introduced into these cells by transfection.
  • the transfected cells are cultured in vitro, and the desired antibody can be prepared from the culture of transformed cells.
  • transgenic animals can also be used to produce a recombinant antibody. That is, the antibody can be obtained from an animal into which the gene encoding the antibody of interest is introduced.
  • the antibody gene can be constructed as a fusion gene by inserting in frame into a gene that encodes a protein produced specifically in milk. Goat ⁇ -casein or such can be used, for example, as the protein secreted in milk. DNA fragments containing the fused gene inserted with the antibody gene is injected into a goat embryo, and then this embryo is introduced into a female goat. Desired antibodies can be obtained as a protein fused with the milk protein from milk produced by the transgenic goat born from the embryo-recipient goat (or progeny thereof).
  • hormones can be administered to the transgenic goat as necessary (Ebert, K. M. et al., Bio/Technology (1994) 12 (7), 699-702).
  • an antigen-binding domain derived from a genetically recombinant antibody that has been artificially modified to reduce the heterologous antigenicity against human and such can be appropriately used as the antigen-binding domain of the antigen-binding molecule.
  • Such genetically recombinant antibodies include, for example, humanized antibodies. These modified antibodies are appropriately produced by known methods.
  • An antibody variable region used to produce the antigen-binding domain of an antigen-binding molecule described herein is generally formed by three complementarity-determining regions (CDRs) that are separated by four framework regions (FRs).
  • CDR is a region that substantially determines the binding specificity of an antibody.
  • the amino acid sequences of CDRs are highly diverse.
  • the FR-forming amino acid sequences often have high identity even among antibodies with different binding specificities. Therefore, generally, the binding specificity of a certain antibody can be introduced to another antibody by CDR grafting.
  • a humanized antibody is also called a reshaped human antibody.
  • humanized antibodies prepared by grafting the CDR of a non-human animal antibody such as a mouse antibody to a human antibody and such are known.
  • Common genetic engineering techniques for obtaining humanized antibodies are also known.
  • overlap extension PCR is known as a method for grafting a mouse antibody CDR to a human FR.
  • a nucleotide sequence encoding a mouse antibody CDR to be grafted is added to primers for synthesizing a human antibody FR. Primers are prepared for each of the four FRs.
  • a human FR that has high identity to a mouse FR is advantageous for maintaining the CDR function. That is, it is generally preferable to use a human FR comprising an amino acid sequence which has high identity to the amino acid sequence of the FR adjacent to the mouse CDR to be grafted.
  • Nucleotide sequences to be ligated are designed so that they will be connected to each other in frame. Human FRs are individually synthesized using the respective primers. As a result, products in which the mouse CDR-encoding DNA is attached to the individual FR-encoding DNAs are obtained. Nucleotide sequences encoding the mouse CDR of each product are designed so that they overlap with each other. Then, complementary strand synthesis reaction is conducted to anneal the overlapping CDR regions of the products synthesized using a human antibody gene as template. Human FRs are ligated via the mouse CDR sequences by this reaction.
  • the full length V region gene in which three CDRs and four FRs are ultimately ligated, is amplified using primers that anneal to its 5′- or 3′-end, which are added with suitable restriction enzyme recognition sequences.
  • An expression vector for humanized antibody can be produced by inserting the DNA obtained as described above and a DNA that encodes a human antibody C region into an expression vector so that they will ligate in frame. After the recombinant vector is transfected into a host to establish recombinant cells, the recombinant cells are cultured, and the DNA encoding the humanized antibody is expressed to produce the humanized antibody in the cell culture (see, European Patent Publication No. EP 239400 and International Patent Publication No. WO 1996/002576).
  • FRs that allow CDRs to form a favorable antigen-binding site when ligated through the CDRs.
  • Amino acid residues in FRs may be substituted as necessary, so that the CDRs of a reshaped human antibody form an appropriate antigen-binding site.
  • amino acid sequence mutations can be introduced into FRs by applying the PCR method used for grafting a mouse CDR into a human FR. More specifically, partial nucleotide sequence mutations can be introduced into primers that anneal to the FR.
  • Nucleotide sequence mutations are introduced into the FRs synthesized by using such primers. Mutant FR sequences having the desired characteristics can be selected by measuring and evaluating the activity of the amino acid-substituted mutant antibody to bind to the antigen by the above-mentioned method (Cancer Res. (1993) 53: 851-856).
  • desired human antibodies can be obtained by immunizing transgenic animals having the entire repertoire of human antibody genes (see WO 1993/012227; WO 1992/003918; WO 1994/002602; WO 1994/025585; WO 1996/034096; WO 1996/033735) by DNA immunization.
  • the V region of a human antibody is expressed as a single-chain antibody (scFv) on phage surface by the phage display method.
  • Phages expressing an scFv that binds to the antigen can be selected.
  • the DNA sequence encoding the human antibody V region that binds to the antigen can be determined by analyzing the genes of selected phages.
  • the DNA sequence of the scFv that binds to the antigen is determined.
  • An expression vector is prepared by fusing the V region sequence in frame with the C region sequence of a desired human antibody, and inserting this into an appropriate expression vector.
  • the expression vector is introduced into cells appropriate for expression such as those described above.
  • the human antibody can be produced by expressing the human antibody-encoding gene in the cells. These methods are already known (see WO 1992/001047; WO 1992/020791; WO 1993/006213; WO 1993/011236; WO 1993/019172; WO 1995/001438; WO 1995/015388).
  • amino acid positions assigned to antibody CDR and FR are specified according to Kabat numbering (Sequences of Proteins of Immunological Interest (National Institute of Health, Bethesda, Md., 1987 and 1991)).
  • Kabat numbering Sequences of Proteins of Immunological Interest (National Institute of Health, Bethesda, Md., 1987 and 1991)
  • variable region amino acids are indicated according to Kabat numbering system
  • constant region amino acids are indicated according to EU numbering system based on Kabat's amino acid positions.
  • the ion concentration refers to a metal ion concentration.
  • Metal ions refer to ions of group I elements except hydrogen such as alkaline metals and copper group elements, group II elements such as alkaline earth metals and zinc group elements, group III elements except boron, group IV elements except carbon and silicon, group VIII elements such as iron group and platinum group elements, elements belonging to subgroup A of groups V, VI, and VII, and metal elements such as antimony, bismuth, and polonium.
  • Metal atoms have the property of releasing valence electrons to become cations. This is referred to as ionization tendency. Metals with strong ionization tendency are deemed to be chemically active.
  • preferred metal ions include, for example, calcium ion.
  • Calcium ion is involved in modulation of many biological phenomena, including contraction of muscles such as skeletal, smooth, and cardiac muscles; activation of movement, phagocytosis, and the like of leukocytes; activation of shape change, secretion, and the like of platelets; activation of lymphocytes; activation of mast cells including secretion of histamine; cell responses mediated by catecholamine a receptor or acetylcholine receptor; exocytosis; release of transmitter substances from neuron terminals; and axoplasmic flow in neurons.
  • Known intracellular calcium ion receptors include troponin C, calmodulin, parvalbumin, and myosin light chain, which have several calcium ion-binding sites and are believed to be derived from a common origin in terms of molecular evolution.
  • calcium-binding motifs include, for example, cadherin domains, EF-hand of calmodulin, C2 domain of Protein kinase C, Gla domain of blood coagulation protein Factor IX, C-type lectins of asialoglycoprotein receptor and mannose-binding receptor, A domains of LDL receptors, annexin, thrombospondin type 3 domain, and EGF-like domains.
  • the conditions of calcium ion concentration include low calcium ion concentration conditions and high calcium ion concentration conditions.
  • the antigen-binding activity of an antigen-binding domain contained in the antigen-binding molecule of the present invention varies depending on calcium ion concentration conditions” means that the antigen-binding activity of an antigen-binding domain contained in the antigen-binding molecule varies due to the difference in the conditions between low and high calcium ion concentrations.
  • the antigen-binding activity of an antigen-binding domain may be higher under a high calcium ion concentration condition than under a low calcium ion concentration condition.
  • the antigen-binding activity of an antigen-binding domain may be, for example, higher under a low calcium ion concentration condition than under a high calcium ion concentration condition.
  • the high calcium ion concentration is not particularly limited to a specific value; however, the concentration may preferably be selected between 100 ⁇ M and 10 mM. In another embodiment, the concentration may be selected between 200 ⁇ M and 5 mM. In an alternative embodiment, the concentration may be selected between 400 ⁇ M and 3 mM. In still another embodiment, the concentration may be selected between 200 ⁇ M and 2 mM. Furthermore, the concentration may be selected between 400 ⁇ M and 1 mM. In particular, a concentration selected between 500 ⁇ M and 2.5 mM, which is close to the plasma (blood) concentration of calcium ion in vivo, is preferred.
  • the low calcium ion concentration is not particularly limited to a specific value; however, the concentration may preferably be selected between 0.1 ⁇ M and 30 ⁇ M. In another embodiment, the concentration may be selected between 0.2 ⁇ M and 20 ⁇ M. In still another embodiment, the concentration may be selected between 0.5 ⁇ M and 10 ⁇ M. In an alternative embodiment, the concentration may be selected between 1 ⁇ M and 5 ⁇ M. Furthermore, the concentration may be selected between 2 ⁇ M and 4 ⁇ M. In particular, a concentration selected between 1 ⁇ M and 5 ⁇ M, which is close to the concentration of ionized calcium in early endosomes in vivo, is preferred.
  • the antigen-binding activity is lower under a low calcium ion concentration condition than under a high calcium ion concentration condition.
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain of the present invention is weaker at a calcium ion concentration selected between 0.1 ⁇ M and 30 ⁇ M than at a calcium ion concentration selected between 100 ⁇ M and 10 mM.
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain of the present invention is weaker at a calcium ion concentration selected between 0.5 ⁇ M and 10 ⁇ M than at a calcium ion concentration selected between 200 ⁇ M and 5 mM.
  • the antigen-binding activity at the calcium ion concentration in the early endosome in vivo is weaker than that at the in vivo plasma calcium ion concentration; and specifically, it means that the antigen-binding activity of an antigen-binding molecule is weaker at a calcium ion concentration selected between 1 ⁇ M and 5 ⁇ M than at a calcium ion concentration selected between 500 ⁇ M and 2.5 mM.
  • Whether the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain is changed depending on metal ion concentrations can be determined, for example, by the use of known measurement methods such as those described in the section “Binding Activity” above. For example, in order to confirm that the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain becomes higher under a high calcium ion concentration condition than under a low calcium ion concentration condition, the antigen-binding activity of the domain or the molecule under low and high calcium ion concentration conditions is compared.
  • the expression “the antigen-binding activity is lower under a low calcium ion concentration condition than under a high calcium ion concentration condition” can also be expressed as “the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain is higher under a high calcium ion concentration condition than under a low calcium ion concentration condition”.
  • “the antigen-binding activity is lower under a low calcium ion concentration condition than under a high calcium ion concentration condition” is sometimes written as “the antigen-binding activity is weaker under a low calcium ion concentration condition than under a high calcium ion concentration condition”.
  • the antigen-binding activity under a low calcium ion concentration condition is reduced to be lower than that under a high calcium ion concentration condition” may be written as “the antigen-binding activity under a low calcium ion concentration condition is made weaker than that under a high calcium ion concentration condition”.
  • the conditions other than calcium ion concentration can be appropriately selected by those skilled in the art, and are not particularly limited.
  • the activity can be determined at 37° C. in HEPES buffer.
  • Biacore GE Healthcare
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain can be assessed by flowing the antigen as an analyte over a chip onto which the antigen-binding domain or antigen-binding molecule comprising the domain is immobilized.
  • the binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain to the membrane antigen can be assessed by flowing the antigen-binding domain or antigen-binding molecule comprising the domain as an analyte over a chip onto which the antigen is immobilized.
  • the ratio of the antigen-binding activity between low and high calcium ion concentration conditions is not particularly limited.
  • the ratio of the KD (dissociation constant) of the antigen-binding molecule for an antigen at a low calcium ion concentration condition with respect to the KD at a high calcium ion concentration condition i.e., the value of KD (3 ⁇ M Ca)/KD (2 mM Ca)
  • KD (3 ⁇ M Ca)/KD (2 mM Ca) is preferably 2 or more, more preferably 10 or more, and still more preferably 40 or more.
  • the upper limit of the KD (3 ⁇ M Ca)/KD (2 mM Ca) value is not particularly limited, and may be any value such as 400, 1000, or 10000 as long as the molecule can be produced by techniques known to those skilled in the art.
  • KD dissociation constant
  • apparent KD apparent dissociation constant
  • KD (dissociation constant) and apparent KD can be determined by methods known to those skilled in the art, for example, using Biacore (GE healthcare), Scatchard plot, or flow cytometer.
  • the dissociation rate constant (kd) can also be preferably used as an index to represent the ratio of the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain of the present invention between low and high calcium concentration conditions.
  • the ratio of the dissociation rate constant (kd) between low and high calcium concentration conditions i.e., the value of kd (low calcium concentration condition)/kd (high calcium concentration condition)
  • the value of kd (low calcium concentration condition)/kd (high calcium concentration condition) is preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, and yet more preferably 30 or more.
  • the upper limit of the Kd (low calcium concentration condition)/kd (high calcium concentration condition) value is not particularly limited, and can be any value such as 50, 100, or 200 as long as the molecule can be produced by techniques known to those skilled in the art.
  • kd dissociation rate constant
  • apparent kd apparent dissociation rate constant
  • the kd (dissociation rate constant) and apparent kd can be determined by methods known to those skilled in the art, for example, using Biacore (GE healthcare) or flow cytometer.
  • an antigen-binding domain or antigen-binding molecule of the present invention can be obtained from a library that is mainly composed of a plurality of antigen-binding molecules whose sequences are different from one another and whose antigen-binding domains have at least one amino acid residue that alters the antigen-binding activity of the antigen-binding molecules depending on ion concentrations.
  • the ion concentrations preferably include, for example, metal ion concentration and hydrogen ion concentration.
  • a “library” refers to a plurality of antigen-binding molecules or a plurality of fusion polypeptides containing antigen-binding molecules, or nucleic acids or polynucleotides encoding their sequences.
  • the sequences of a plurality of antigen-binding molecules or a plurality of fusion polypeptides containing antigen-binding molecules in a library are not identical, but are different from one another.
  • sequences are different from one another in the expression “a plurality of antigen-binding molecules whose sequences are different from one another” means that the sequences of antigen-binding molecules in a library are different from one another.
  • the number of sequences different from one another reflects the number of independent clones with different sequences, and may also be referred to as “library size”.
  • the library size of a conventional phage display library ranges from 10 6 to 10 12 .
  • the library size can be increased up to 10 14 by the use of known techniques such as ribosome display.
  • the actual number of phage particles used in panning selection of a phage library is in general 10-10000 times greater than the library size.
  • sequences are different from one another means that the sequences of independent antigen-binding molecules in a library, excluding library equivalents, are different from one another. More specifically, the above means that there are 10 6 to 10 14 antigen-binding molecules whose sequences are different from one another, preferably 10 7 to 10 12 molecules, more preferably 10 8 to 10 11 , and particularly preferably 10 8 to 10 10 whose sequences are different from one another.
  • the phrase “a plurality of” in the expression “a library mainly composed of a plurality of antigen-binding molecules” generally refers to, in the case of, for example, antigen-binding molecules, fusion polypeptides, polynucleotide molecules, vectors, or viruses of the present invention, a group of two or more types of the substance.
  • antigen-binding molecules fusion polypeptides, polynucleotide molecules, vectors, or viruses of the present invention
  • a group of two or more types of the substance For example, when two or more substances are different from one another in a particular characteristic, this means that there are two or more types of the substance.
  • Such examples may include, for example, mutant amino acids observed at specific amino acid positions in an amino acid sequence.
  • antigen-binding molecules of the present invention when there are two or more antigen-binding molecules of the present invention whose sequences are substantially the same or preferably the same except for flexible residues or except for particular mutant amino acids at hypervariable positions exposed on the surface, there is a plurality of antigen-binding molecules of the present invention.
  • polynucleotide molecules when there are two or more polynucleotide molecules whose sequences are substantially the same or preferably the same except for nucleotides encoding flexible residues or nucleotides encoding mutant amino acids of hypervariable positions exposed on the surface, there are a plurality of polynucleotide molecules in the present invention.
  • the phrase “mainly composed of” in the expression “a library mainly composed of a plurality of antigen-binding molecules” reflects the number of antigen-binding molecules whose antigen-binding activity varies depending on ion concentrations, among independent clones with different sequences in a library. Specifically, it is preferable that there are at least 10 4 antigen-binding molecules having such binding activity in a library. More preferably, antigen-binding domains of the present invention can be obtained from a library containing at least 10 5 antigen-binding molecules having such binding activity. Still more preferably, antigen-binding domains of the present invention can be obtained from a library containing at least 10 6 antigen-binding molecules having such binding activity.
  • antigen-binding domains of the present invention can be obtained from a library containing at least 10 7 antigen-binding molecules having such binding activity. Yet more preferably, antigen-binding domains of the present invention can be obtained from a library containing at least 10 8 antigen-binding molecules having such binding activity. Alternatively, this may also be preferably expressed as the ratio of the number of antigen-binding molecules whose antigen-binding activity varies depending on ion concentrations with respect to the number of independent clones having different sequences in a library.
  • antigen-binding domains of the present invention can be obtained from a library in which antigen-binding molecules having such binding activity account for 0.1% to 80%, preferably 0.5% to 60%, more preferably 1% to 40%, still more preferably 2% to 20%, and particularly preferably 4% to 10% of independent clones with different sequences in the library.
  • antigen-binding molecules having such binding activity account for 0.1% to 80%, preferably 0.5% to 60%, more preferably 1% to 40%, still more preferably 2% to 20%, and particularly preferably 4% to 10% of independent clones with different sequences in the library.
  • fusion polypeptides polynucleotide molecules, or vectors
  • similar expressions may be possible using the number of molecules or the ratio to the total number of molecules.
  • similar expressions may also be possible using the number of virions or the ratio to total number of virions.
  • Antigen-binding domains or antigen-binding molecules of the present invention to be screened by the above-described screening methods may be prepared in any manner.
  • the metal ion is calcium ion
  • preexisting antigen-binding domains or antigen-binding molecules preexisting libraries (phage library, etc.)
  • antibodies or libraries prepared from hybridomas obtained by immunizing animals or from B cells of immunized animals antibodies or libraries obtained by introducing amino acids capable of chelating calcium (for example, aspartic acid and glutamic acid) or unnatural amino acid mutations into the above-described antibodies or libraries (calcium-chelatable amino acids (such as aspartic acid and glutamic acid), libraries with increased content of unnatural amino acids, libraries prepared by introducing calcium-chelatable amino acids (such as aspartic acid and glutamic acid) or unnatural amino acid mutations at particular positions, or the like.
  • amino acids that alter the antigen-binding activity of antigen-binding molecules depending on ion concentrations as described above may be any types of amino acids as long as the amino acids form a calcium-binding motif Calcium-binding motifs are well known to those skilled in the art and have been described in details (for example, Springer et al. (Cell (2000) 102, 275-277); Kawasaki and Kretsinger (Protein Prof (1995) 2, 305-490); Moncrief et al. (J. Mol. Evol. (1990) 30, 522-562); Chauvaux et al. (Biochem. J. (1990) 265, 261-265); Bairoch and Cox (FEBS Lett.
  • any known calcium-binding motifs including type C lectins such as ASGPR, CD23, MBR, and DC-SIGN, can be included in antigen-binding molecules of the present invention.
  • Preferred examples of such preferred calcium-binding motifs also include, in addition to those described above, for example, the calcium-binding motif in the antigen-binding domain of SEQ ID NO: 5.
  • amino acids having metal-chelating activity may also be preferably used.
  • metal-chelating amino acids include, for example, serine (Ser (S)), threonine (Thr (T)), asparagine (Asn (N)), glutamine (Gln (Q)), aspartic acid (Asp (D)), and glutamic acid (Glu (E)).
  • Positions in the antigen-binding domains at which the above-described amino acids are contained are not particularly limited to particular positions, and may be any positions within the heavy chain variable region or light chain variable region that forms an antigen-binding domain, as long as they alter the antigen-binding activity of antigen-binding molecules depending on calcium ion concentrations.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose heavy chain antigen-binding domains contain amino acids that alter the antigen-binding activity of the antigen-binding molecules depending on calcium ion concentrations.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose heavy chain CDR3 domains contain the above-mentioned amino acids.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose heavy chain CDR3 domains contain the above-mentioned amino acids at positions 95, 96, 100a, and/or 101 as indicated according to the Kabat numbering system.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chain antigen-binding domains contain amino acids that alter the antigen-binding activity of antigen-binding molecules depending on calcium ion concentrations.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chain CDR1 domains contain the above-mentioned amino acids.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chain CDR1 domains contain the above-mentioned amino acids at positions 30, 31, and/or 32 as indicated according to the Kabat numbering system.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chain CDR2 domains contain the above-mentioned amino acid residues.
  • the present invention provides libraries mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chain CDR2 domains contain the above-mentioned amino acid residues at position 50 as indicated according to the Kabat numbering system.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chain CDR3 domains contain the above-mentioned amino acid residues.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chain CDR3 domains contain the above-mentioned amino acid residues at position 92 as indicated according to the Kabat numbering system.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and in which two or three CDRs selected from the above-described light chain CDR1, CDR2, and CDR3 contain the aforementioned amino acid residues.
  • antigen-binding domains of the present invention can be obtained from a library mainly composed of antigen-binding molecules whose sequences are different from one another and whose light chains contain the aforementioned amino acid residues at any one or more of positions 30, 31, 32, 50, and/or 92 as indicated according to the Kabat numbering system.
  • the framework sequences of the light chain and/or heavy chain variable region of an antigen-binding molecule preferably contain human germ line framework sequences.
  • the framework sequences are completely human sequences, it is expected that when such an antigen-binding molecule of the present invention is administered to humans (for example, to treat diseases), it induces little or no immunogenic response.
  • the phrase “containing a germ line sequence” in the present invention means that a part of the framework sequences in the present invention is identical to a part of any human germ line framework sequences.
  • the heavy chain FR2 sequence of an antigen-binding molecule in the present invention is a combination of heavy chain FR2 sequences of different human germ line framework sequences, such a molecule is also an antigen-binding molecule in the present invention “containing a germ line sequence”.
  • the frameworks include, for example, fully human framework region sequences currently known, which are included in the website of V-Base (http://vbase.mrc-cpe.cam.ac.uk/) or others. Those framework region sequences can be appropriately used as a germ line sequence contained in an antigen-binding molecule of the present invention.
  • the germ line sequences may be categorized according to their similarity (Tomlinson et al. (J. Mol. Biol. (1992) 227, 776-798); Williams and Winter (Eur. J. Immunol. (1993) 23, 1456-1461); Cox et al. (Nat. Genetics (1994) 7, 162-168)).
  • Appropriate germ line sequences can be selected from V ⁇ , which is grouped into seven subgroups; V ⁇ , which is grouped into ten subgroups; and VH, which is grouped into seven subgroups.
  • Fully human VH sequences preferably include, but are not limited to, for example, VH sequences of:
  • subgroup VH1 for example, VH1-2, VH1-3, VH1-8, VH1-18, VH1-24, VH1-45, VH1-46, VH1-58, and VH1-69); subgroup VH2 (for example, VH2-5, VH2-26, and VH2-70); subgroup VH3 (VH3-7, VH3-9, VH3-11, VH3-13, VH3-15, VH3-16, VH3-20, VH3-21, VH3-23, VH3-30, VH3-33, VH3-35, VH3-38, VH3-43, VH3-48, VH3-49, VH3-53, VH3-64, VH3-66, VH3-72, VH3-73, and VH3-74); subgroup VH4 (VH4-4, VH4-28, VH4-31, VH4-34, VH4-39, VH4-59, and VH4-61); subgroup VH5 (VH5-51); sub
  • Fully human V ⁇ sequences preferably include, but are not limited to, for example:
  • Fully human V ⁇ sequences preferably include, but are not limited to, for example:
  • V1-2 V1-3, V1-4, V1-5, V1-7, V1-9, V1-11, V1-13, V1-16, V1-17, V1-18, V1-19, V1-20, and V1-22, grouped into subgroup VL1; V2-1, V2-6, V2-7, V2-8, V2-11, V2-13, V2-14, V2-15, V2-17, and V2-19, grouped into subgroup VL1; V3-2, V3-3, and V3-4, grouped into subgroup VL3; V4-1, V4-2, V4-3, V4-4, and V4-6, grouped into subgroup VL4; and V5-1, V5-2, V5-4, and V5-6, grouped into subgroup VL5 (Kawasaki et al. (Genome Res. (1997) 7, 250-261)).
  • these framework sequences are different from one another at one or more amino acid residues.
  • These framework sequences can be used in combination with “at least one amino acid residue that alters the antigen-binding activity of an antigen-binding molecule depending on ion concentration conditions” in the present invention.
  • Other examples of the fully human frameworks used in combination with “at least one amino acid residue that alters the antigen-binding activity of an antigen-binding molecule depending on ion concentration conditions” in the present invention include, but are not limited to, for example, KOL, NEWM, REI, EU, TUR, TEI, LAY, and POM (for example, Kabat et al. (1991) supra; Wu et al. (J. Exp. Med. (1970) 132, 211-250)).
  • variable region-encoding genes may be selected from a group of commonly occurring functional germ line genes.
  • variable region sequences heavy or light chain variable region sequences, CDR sequences, or framework sequences contain amino acids that alter the antigen-binding activity of the antigen-binding molecules depending on calcium ion concentration conditions.
  • a library which contains a plurality of antigen-binding molecules of the present invention whose sequences are different from one another can be constructed by combining heavy chain variable regions prepared as a randomized variable region sequence library with a light chain variable region selected as a framework sequence originally containing at least one amino acid residue that alters the antigen-binding activity of the antigen-binding molecule depending on calcium ion concentration conditions.
  • a light chain variable region selected as a framework sequence originally containing at least one amino acid residue that alters the antigen-binding activity of the antigen-binding molecule depending on calcium ion concentration conditions As a non-limiting example, when the ion concentration is calcium ion concentration, such preferred libraries include, for example, those constructed by combining the light chain variable region sequence of SEQ ID NO: 5 (Vk5-2) and the heavy chain variable region produced as a randomized variable region sequence library.
  • a light chain variable region sequence selected as a framework region originally containing at least one amino acid residue that alters the antigen-binding activity of an antigen-binding domain or antigen-binding molecule as mentioned above can be design to contain various amino acid residues other than the above amino acid residues.
  • residues are referred to as flexible residues.
  • the number and position of flexible residues are not particularly limited as long as the antigen-binding activity of the antigen-binding domain or antigen-binding molecule of the present invention varies depending on ion concentrations.
  • the CDR sequences and/or FR sequences of the heavy chain and/or light chain may contain one or more flexible residues.
  • the ion concentration is calcium ion concentration
  • non-limiting examples of flexible residues to be introduced into the light chain variable region sequence of SEQ ID NO: 5 (Vk5-2) include the amino acid residues listed in Tables 1 or 2.
  • flexible residues refer to amino acid residue variations present at hypervariable positions at which several different amino acids are present on the light chain and heavy chain variable regions when the amino acid sequences of known and/or native antibodies or antigen-binding domains are compared.
  • Hypervariable positions are generally located in the CDR regions.
  • the data provided by Kabat, Sequences of Proteins of Immunological Interest (National Institute of Health Bethesda Md.) (1987 and 1991) is useful to determine hypervariable positions in known and/or native antibodies.
  • databases on the Internet http://vbase.mrc-cpe.cam.ac.uk/, http://www.bioinf.org.uk/abs/index.html
  • a certain amino acid position has preferably about 2 to about 20 possible amino acid residue variations, preferably about 3 to about 19, preferably about 4 to about 18, preferably 5 to 17, preferably 6 to 16, preferably 7 to 15, preferably 8 to 14, preferably 9 to 13, and preferably 10 to 12 possible amino acid residue variations
  • the position is hypervariable.
  • a certain amino acid position may have preferably at least about 2, preferably at least about 4, preferably at least about 6, preferably at least about 8, preferably about 10, and preferably about 12 amino acid residue variations.
  • a library containing a plurality of antigen-binding molecules of the present invention whose sequences are different from one another can be constructed by combining heavy chain variable regions produced as a randomized variable region sequence library with light chain variable regions into which at least one amino acid residue that alters the antigen-binding activity of antigen-binding molecules depending on ion concentrations as mentioned above is introduced.
  • non-limiting examples of such libraries preferably include, for example, libraries in which heavy chain variable regions produced as a randomized variable region sequence library are combined with light chain variable region sequences in which a particular residue(s) in a germ line sequence such as SEQ ID NO: 6 (Vk1), SEQ ID NO: 7 (Vk2), SEQ ID NO: 8 (Vk3), or SEQ ID NO: 9 (Vk4) has been substituted with at least one amino acid residue that alters the antigen-binding activity of an antigen-binding molecule depending on calcium ion concentrations.
  • Non-limiting examples of such amino acid residues include amino acid residues in light chain CDR1.
  • non-limiting examples of such amino acid residues include amino acid residues in light chain CDR2.
  • non-limiting examples of such amino acid residues also include amino acid residues in light chain CDR3.
  • Non-limiting examples of such amino acid residues contained in light chain CDR1 include those at positions 30, 31, and/or 32 in the CDR1 of light chain variable region as indicated by EU numbering.
  • non-limiting examples of such amino acid residues contained in light chain CDR2 include an amino acid residue at position 50 in the CDR2 of light chain variable region as indicated by Kabat numbering.
  • non-limiting examples of such amino acid residues contained in light chain CDR3 include an amino acid residue at position 92 in the CDR3 of light chain variable region as indicated by Kabat numbering.
  • amino acid residues can be contained alone or in combination as long as they form a calcium-binding motif and/or as long as the antigen-binding activity of an antigen-binding molecule varies depending on calcium ion concentrations.
  • troponin C calmodulin, parvalbumin, and myosin light chain, which have several calcium ion-binding sites and are believed to be derived from a common origin in terms of molecular evolution, are known
  • the light chain CDR1, CDR2, and/or CDR3 can be designed to have their binding motifs.
  • cadherin domains EF hand of calmodulin, C2 domain of Protein kinase C, Gla domain of blood coagulation protein Factor IX, C type lectins of asialoglycoprotein receptor and mannose-binding receptor, A domains of LDL receptors, annexin, thrombospondin type 3 domain, and EGF-like domains in an appropriate manner for the above purposes.
  • the sequences of the light chain variable regions can be designed to contain flexible residues in the same manner as described above.
  • the number and position of such flexible residues are not particularly limited to particular embodiments as long as the antigen-binding activity of antigen-binding molecules of the present invention varies depending on ion concentration conditions.
  • the CDR sequences and/or FR sequences of heavy chain and/or light chain can contain one or more flexible residues.
  • the ion concentration is calcium ion concentration
  • non-limiting examples of flexible residues to be introduced into the sequence of light chain variable region include the amino acid residues listed in Tables 1 and 2.
  • the preferred heavy chain variable regions to be combined include, for example, randomized variable region libraries.
  • Known methods are combined as appropriate to produce a randomized variable region library.
  • an immune library constructed based on antibody genes derived from lymphocytes of animals immunized with a specific antigen, patients with infections, persons with an elevated antibody titer in blood as a result of vaccination, cancer patients, or auto immune disease patients may be preferably used as a randomized variable region library.
  • a synthetic library produced by replacing the CDR sequences of V genes in genomic DNA or functional reshaped V genes with a set of synthetic oligonucleotides containing sequences encoding codon sets of an appropriate length can also be preferably used as a randomized variable region library.
  • sequence diversity is observed in the heavy chain CDR3 sequence, it is also possible to replace the CDR3 sequence only.
  • a criterion of giving rise to diversity in amino acids in the variable region of an antigen-binding molecule is that diversity is given to amino acid residues at surface-exposed positions in the antigen-binding molecule.
  • the surface-exposed position refers to a position that is considered to be able to be exposed on the surface and/or contacted with an antigen, based on structure, ensemble of structures, and/or modeled structure of an antigen-binding molecule. In general, such positions are CDRs. Preferably, surface-exposed positions are determined using coordinates from a three-dimensional model of an antigen-binding molecule using a computer program such as the InsightII program (Accelrys). Surface-exposed positions can be determined using algorithms known in the art (for example, Lee and Richards (J. Mol. Biol. (1971) 55, 379-400); Connolly (J. Appl. Cryst. (1983) 16, 548-558)).
  • Determination of surface-exposed positions can be performed using software suitable for protein modeling and three-dimensional structural information obtained from an antibody.
  • Software that can be used for these purposes preferably includes SYBYL Biopolymer Module software (Tripos Associates).
  • SYBYL Biopolymer Module software Tripos Associates
  • the “size” of a probe which is used in the calculation is set at about 1.4 Angstrom or smaller in radius.
  • Pacios Comput. Chem. (1994) 18 (4), 377-386; J. Mol. Model. (1995) 1, 46-53).
  • a naive library which is constructed from antibody genes derived from lymphocytes of healthy persons and whose repertoire consists of naive sequences, which are antibody sequences with no bias, can also be particularly preferably used as a randomized variable region library (Gejima et al. (Human Antibodies (2002) 11, 121-129); Cardoso et al. (Scand. J. Immunol. (2000) 51, 337-344)).
  • an amino acid sequence comprising a naive sequence refers to an amino acid sequence obtained from such a naive library.
  • an antigen-binding domain of the present invention can be obtained from a library containing a plurality of antigen-binding molecules of the present invention whose sequences are different from one another, prepared by combining light chain variable regions constructed as a randomized variable region sequence library with a heavy chain variable region selected as a framework sequence that originally contains “at least one amino acid residue that alters the antigen-binding activity of an antigen-binding molecule depending on ion concentration conditions”.
  • non-limiting examples of such libraries preferably include those constructed by combining light chain variable regions constructed as a randomized variable region sequence library with the sequence of heavy chain variable region of SEQ ID NO: 10 (6RL#9-IgG1) or SEQ ID NO: 11 (6KC4-1#85-IgG1).
  • a library can be constructed by selecting appropriate light chain variable regions from those having germ line sequences, instead of light chain variable regions constructed as a randomized variable region sequence library.
  • Such preferred libraries include, for example, those in which the sequence of heavy chain variable region of SEQ ID NO: 10 (6RL#9-IgG1) or SEQ ID NO: 11 (6KC4-1#85-IgG1) is combined with light chain variable regions having germ line sequences.
  • sequence of a heavy chain variable region selected as a framework sequence that originally contains “at least one amino acid residue that alters the antigen-binding activity of an antigen-binding molecule depending on ion concentration conditions” as mentioned above can be designed to contain flexible residues.
  • the number and position of the flexible residues are not particularly limited as long as the antigen-binding activity of an antigen-binding molecule of the present invention varies depending on ion concentration conditions.
  • the CDR and/or FR sequences of heavy chain and/or light chain can contain one or more flexible residues.
  • non-limiting examples of flexible residues to be introduced into the sequence of heavy chain variable region of SEQ ID NO: 10 include all amino acid residues of heavy chain CDR1 and CDR2 and the amino acid residues of the heavy chain CDR3 except those at position(s) 95, 96, and/or 100a.
  • non-limiting examples of flexible residues to be introduced into the sequence of heavy chain variable region of SEQ ID NO: 11 include all amino acid residues of heavy chain CDR1 and CDR2 and the amino acid residues of the heavy chain CDR3 except those at amino acid position(s) 95 and/or 101.
  • a library containing a plurality of antigen-binding molecules whose sequences are different from one another can be constructed by combining light chain variable regions constructed as a randomized variable region sequence library or light chain variable regions having germ line sequences with heavy chain variable regions into which “at least one amino acid residue that alters the antigen-binding activity of an antigen-binding molecule depending on ion concentration conditions” has been introduced as mentioned above.
  • non-limiting examples of such libraries preferably include those in which light chain variable regions constructed as a randomized variable region sequence library or light chain variable regions having germ line sequences are combined with the sequence of a heavy chain variable region in which a particular residue(s) has been substituted with at least one amino acid residue that alters the antigen-binding activity of an antigen-binding molecule depending on calcium ion concentration conditions.
  • Non-limiting examples of such amino acid residues include amino acid residues of the heavy chain CDR1. Further non-limiting examples of such amino acid residues include amino acid residues of the heavy chain CDR2. In addition, non-limiting examples of such amino acid residues also include amino acid residues of the heavy chain CDR3.
  • Non-limiting examples of such amino acid residues of heavy chain CDR3 include the amino acid(s) at position(s) 95, 96, 100a, and/or 101 in the CDR3 of heavy chain variable region as indicated by the Kabat numbering. Furthermore, these amino acid residues can be contained alone or in combination as long as they form a calcium-binding motif and/or the antigen-binding activity of an antigen-binding molecule varies depending on calcium ion concentration conditions.
  • the sequence of the heavy chain variable region can also be designed to contain flexible residues in the same manner as described above.
  • the number and position of flexible residues are not particularly limited as long as the antigen-binding activity of an antigen-binding molecule of the present invention varies depending on ion concentration conditions.
  • the heavy chain CDR and/or FR sequences may contain one or more flexible residues.
  • randomized variable region libraries can be preferably used as amino acid sequences of CDR1, CDR2, and/or CDR3 of the heavy chain variable region other than the amino acid residues that alter the antigen-binding activity of an antigen-binding molecule depending on ion concentration conditions.
  • germ line sequences are used as light chain variable regions, non-limiting examples of such sequences include those of SEQ ID NO: 6 (Vk1), SEQ ID NO: 7 (Vk2), SEQ ID NO: 8 (Vk3), and SEQ ID NO: 9 (Vk4).
  • amino acids that alter the antigen-binding activity of an antigen-binding molecule depending on calcium ion concentration conditions can be preferably used, as long as they form a calcium-binding motif.
  • amino acids include electron-donating amino acids.
  • electron-donating amino acids include serine, threonine, asparagine, glutamic acid, aspartic acid, and glutamic acid.
  • the condition of ion concentrations refers to the condition of hydrogen ion concentrations or pH conditions.
  • the concentration of proton i.e., the nucleus of hydrogen atom
  • pH is defined as ⁇ log 10aH+.
  • aH+ is nearly equal to the hydrogen ion strength.
  • the ionic product of water at 25° C.
  • pH conditions when pH condition is used as the ion concentration condition, pH conditions include conditions of high hydrogen ion concentration or low pHs, i.e., an acidic pH range condition, and conditions of low hydrogen ion concentration or high pHs, i.e., a neutral pH range condition.
  • the antigen-binding activity of an antigen-binding domain contained in the antigen-binding molecule of the present invention varies depending on pH condition means that the antigen-binding activity of an antigen-binding domain contained in an antigen-binding molecule varies due to the difference in conditions of a high hydrogen ion concentration or low pH (an acidic pH range) and a low hydrogen ion concentration or high pH (a neutral pH range).
  • neutral pH range is not limited to a specific value and is preferably selected from between pH 6.7 and pH 10.0.
  • the pH can be selected from between pH 6.7 and pH 9.5.
  • the pH can be selected from between pH 7.0 and pH 9.0.
  • the pH can be selected from between pH 7.0 and pH 8.0.
  • the preferred pH includes pH 7.4, which is close to the pH of plasma (blood) in vivo.
  • an acidic pH range is not limited to a specific value and is preferably selected from between pH 4.0 and pH 6.5.
  • the pH can be selected from between pH 4.5 and pH 6.5.
  • the pH can be selected from between pH 5.0 and pH 6.5.
  • the pH can be selected from between pH 5.5 and pH 6.5.
  • the preferred pH includes pH 5.8, which is close to the ionized calcium concentration in the early endosome in vivo.
  • the antigen-binding activity under a condition of a high hydrogen ion concentration or low pH (an acidic pH range) is lower than that under a condition of a low hydrogen ion concentration or high pH (a neutral pH range) means that the antigen-binding activity of antigen-binding domain or antigen-binding molecule comprising the domain of the present invention at a pH selected from between pH 4.0 and pH 6.5 is weaker than that at a pH selected from between pH 6.7 and pH 10.0; preferably means that the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain at a pH selected from between pH 4.5 and pH 6.5 is weaker than that at a pH selected from between pH 6.7 and pH 9.5; more preferably, means that the antigen-binding activity of an antigen-binding molecule at a pH selected from between pH 5.0 and pH 6.5 is weaker than that at a pH selected from between pH 7.0 and pH 9.0; still more preferably means
  • Whether the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain has changed by the pH condition can be determined, for example, by the use of known measurement methods such as those described in the section “Binding Activity” above.
  • the binding activity is measured under different pH conditions using the measurement methods described above.
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain is compared under the conditions of acidic pH range and neutral pH range to confirm that binding activity of the domain or the molecule changes to be higher under the condition of neutral pH range than that under the condition of acidic pH range.
  • the expression “the antigen-binding activity under a condition of high hydrogen ion concentration or low pH, i.e., under an acidic pH range condition, is lower than that under a condition of low hydrogen ion concentration or high pH, i.e., under a neutral pH range condition” can also be expressed as “the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain under a condition of low hydrogen ion concentration or high pH, i.e., under a neutral pH range condition, is higher than that under a condition of high hydrogen ion concentration or low pH, i.e., under an acidic pH range condition”.
  • the antigen-binding activity under a condition of high hydrogen ion concentration or low pH, i.e., under an acidic pH range condition is lower than that under a condition of low hydrogen ion concentration or high pH, i.e., under a neutral pH range condition
  • the antigen-binding activity under a condition of high hydrogen ion concentration or low pH, i.e., under an acidic pH range condition is weaker than the antigen-binding ability under a condition of low hydrogen ion concentration or high pH, i.e., under a neutral pH range condition”.
  • the antigen-binding activity under a condition of high hydrogen ion concentration or low pH, i.e., under an acidic pH range condition is reduced to be lower than that under a condition of low hydrogen ion concentration or high pH, i.e., under a neutral pH range condition
  • the antigen-binding activity under a condition of high hydrogen ion concentration or low pH, i.e., under an acidic pH range condition is reduced to be weaker than the antigen-binding ability under a condition of low hydrogen ion concentration or high pH, i.e., under a neutral pH range condition”.
  • the conditions other than hydrogen ion concentration or pH for measuring the antigen-binding activity may be suitably selected by those skilled in the art and are not particularly limited. Measurements can be carried out, for example, at 37° C. using HEPES buffer. Measurements can be carried out, for example, using Biacore (GE Healthcare).
  • the antigen is a soluble antigen
  • the antigen-binding activity of antigen-binding domain or antigen-binding molecule comprising the domain can be determined by assessing the binding activity to the soluble antigen by flowing the antigen as an analyte into a chip immobilized with the antigen-binding domain or the antigen-binding molecule comprising the domain.
  • the antigen is a membrane antigen
  • the binding activity to the membrane antigen can be assessed by flowing the antigen-binding domain or the antigen-binding molecule comprising the domain as an analyte into a chip immobilized with the antigen.
  • the ratio of the antigen-binding activity between that under a condition of high hydrogen ion concentration or low pH, i.e., under an acidic pH range condition, and under a condition of low hydrogen ion concentration or high pH, i.e., under a neutral pH range condition is not particularly limited, and the value of KD (pH 5.8)/KD (pH 7.4), which is the ratio of the dissociation constant (KD) for an antigen at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition to the KD at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition
  • the dissociation rate constant (kd) can be suitably used as an index for indicating the ratio of the antigen-binding activity of an antigen-binding domain or antigen-binding molecule comprising the domain of the present invention between that at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition and at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition.
  • the upper limit of kd (in an acidic pH range condition)/kd (in a neutral pH range condition) value is not particularly limited, and may be any value such as 50, 100, or 200, as long as the molecule can be produced by the techniques of those skilled in the art.
  • the dissociation rate constant (kd) can be used as the value for antigen-binding activity and when the antigen is a membrane antigen, the apparent dissociation rate constant (kd) can be used.
  • the dissociation rate constant (kd) and apparent dissociation rate constant (kd) can be determined by methods known to those skilled in the art, and Biacore (GE healthcare), flow cytometer, and such may be used.
  • Biacore GE healthcare
  • an antigen-binding domain or antigen-binding molecule whose antigen-binding activity at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition is lower than that at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition which is one embodiment provided by the present invention, can be obtained via screening of antigen-binding domains or antigen-binding molecules, comprising the following steps (a) to (c):
  • an antigen-binding domain or antigen-binding molecule whose antigen-binding activity at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition, is lower than that at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition which is one embodiment provided by the present invention, can be obtained via screening of antigen-binding domains or antigen-binding molecules, or a library thereof, comprising the following steps (a) to (c):
  • step (a) contacting an antigen-binding domain or antigen-binding molecule, or a library thereof, in a neutral pH range condition with an antigen; (b) placing in an acidic pH range condition the antigen-binding domain or antigen-binding molecule bound to the antigen in step (a); and (c) isolating the antigen-binding domain or antigen-binding molecule dissociated in step (b).
  • An antigen-binding domain or antigen-binding molecule whose antigen-binding activity at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition is lower than that at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition which is another embodiment provided by the present invention, can be obtained via screening of antigen-binding domains or antigen-binding molecules, or a library thereof, comprising the following steps (a) to (d):
  • step (a) contacting in an acidic pH range condition an antigen with a library of antigen-binding domains or antigen-binding molecules; (b) selecting the antigen-binding domain or antigen-binding molecule which does not bind to the antigen in step (a); (c) allowing the antigen-binding domain or antigen-binding molecule selected in step (b) to bind with the antigen in a neutral pH range condition; and (d) isolating the antigen-binding domain or antigen-binding molecule bound to the antigen in step (c).
  • step (a) contacting in a neutral pH range condition a library of antigen-binding domains or antigen-binding molecules with a column immobilized with an antigen; (b) eluting in an acidic pH range condition from the column the antigen-binding domain or antigen-binding molecule bound to the column in step (a); and (c) isolating the antigen-binding domain or antigen-binding molecule eluted in step (b).
  • step (a) allowing, in an acidic pH range condition, a library of antigen-binding domains or antigen-binding molecules to pass a column immobilized with an antigen; (b) collecting the antigen-binding domain or antigen-binding molecule eluted without binding to the column in step (a); (c) allowing the antigen-binding domain or antigen-binding molecule collected in step (b) to bind with the antigen in a neutral pH range condition; and (d) isolating the antigen-binding domain or antigen-binding molecule bound to the antigen in step (c).
  • step (a) contacting an antigen with a library of antigen-binding domains or antigen-binding molecules in a neutral pH range condition; (b) obtaining the antigen-binding domain or antigen-binding molecule bound to the antigen in step (a); (c) placing in an acidic pH range condition the antigen-binding domain or antigen-binding molecule obtained in step (b); and (d) isolating the antigen-binding domain or antigen-binding molecule whose antigen-binding activity in step (c) is weaker than the standard selected in step (b).
  • the present invention provides antigen-binding domains and antigen-binding molecules whose antigen-binding activity in an acidic pH range condition is lower than that in a neutral pH range condition, which are obtained by a screening method that further comprises the steps of repeating steps (a) to (c) or (a) to (d) in the above-described screening methods.
  • the number of times that steps (a) to (c) or (a) to (d) is repeated is not particularly limited; however, the number is 10 or less in general.
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule at a condition of a high hydrogen ion concentration or low pH, i.e., in an acidic pH range is not particularly limited, as long as it is the antigen-binding activity at a pH of between 4.0 and 6.5, and includes the antigen-binding activity at a pH of between 4.5 and 6.6 as the preferred pH.
  • the antigen-binding activity also includes that at a pH of between 5.0 and 6.5, and that at a pH of between 5.5 and 6.5 as another preferred pH.
  • the antigen-binding activity also includes that at the pH in the early endosome in vivo as the more preferred pH, and specifically, that at pH 5.8.
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule at a condition of a low hydrogen ion concentration or high pH, i.e., in a neutral pH range is not particularly limited, as long as it is the antigen-binding activity at a pH of between 6.7 and 10, and includes the antigen-binding activity at a pH of between 6.7 and 9.5 as the preferred pH.
  • the antigen-binding activity also includes that at a pH of between 7.0 and 9.5 and that at a pH of between 7.0 and 8.0 as another preferred pH.
  • the antigen-binding activity also includes that at the pH of plasma in vivo as the more preferred pH, and specifically, that at pH 7.4.
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule can be measured by methods known to those skilled in the art. Those skilled in the art can suitably determine conditions other than ionized calcium concentration.
  • the antigen-binding activity of an antigen-binding domain or antigen-binding molecule can be assessed based on the dissociation constant (KD), apparent dissociation constant (KD), dissociation rate constant (kd), apparent dissociation rate constant (kd), and such. These can be determined by methods known to those skilled in the art, for example, using Biacore (GE healthcare), Scatchard plot, or FACS.
  • the step of selecting an antigen-binding domain or antigen-binding molecule whose antigen-binding activity at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition, is higher than that at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition is synonymous with the step of selecting an antigen-binding domain or antigen-binding molecule whose antigen-binding activity at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition, is lower than that at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition.
  • the difference between the antigen-binding activity at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition, and that at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition is not particularly limited; however, the antigen-binding activity at a condition of low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition, is preferably twice or more, more preferably 10 times or more, and still more preferably 40 times or more than that at a condition of high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition.
  • the antigen-binding domain or antigen-binding molecule of the present invention to be screened by the above-described screening methods may be prepared in any manner.
  • conventional antigen-binding molecules conventional libraries (phage library, etc.), antibodies or libraries prepared from B cells of immunized animals or from hybridomas obtained by immunizing animals, antibodies or libraries (libraries with increased content of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids, libraries introduced with amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acid mutations at specific positions, etc.) obtained by introducing amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acid mutations into the above-described antibodies or libraries may be used.
  • Methods for obtaining an antigen-binding domain or antigen-binding molecule whose antigen-binding activity at a low hydrogen ion concentration or high pH, i.e., in a neutral pH range condition, is higher than that at a high hydrogen ion concentration or low pH, i.e., in an acidic pH range condition, from an antigen-binding domains or antigen-binding molecules prepared from hybridomas obtained by immunizing animals or from B cells of immunized animals preferably include, for example, the antigen-binding molecule or antigen-binding molecule in which at least one of the amino acids of the antigen-binding domain or antigen-binding molecule is substituted with an amino acid with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or an unnatural amino acid mutation, or the antigen-binding domain or antigen-binding molecule inserted with an amino acid with a side chain pKa of 4.0-8.0 (for example, his
  • the sites of introducing mutations of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids are not particularly limited, and may be any position as long as the antigen-binding activity in an acidic pH range becomes weaker than that in a neutral pH range (the value of KD (in an acidic pH range)/KD (in a neutral pH range) or kd (in an acidic pH range)/kd (in a neutral pH range) is increased) as compared to before substitution or insertion.
  • the antigen-binding molecule is an antibody
  • antibody variable region and CDRs are suitable.
  • Those skilled in the art can appropriately determine the number of amino acids to be substituted with or the number of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids to be inserted. It is possible to substitute with a single amino acid having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or a single unnatural amino acid; it is possible to insert a single amino acid having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or a single unnatural amino acid; it is possible to substitute with two or more amino acids having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or two or more unnatural amino acids; and it is possible to insert two or more amino acids having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or two or more unnatural amino acids; and it is possible to
  • amino acids having a side chain pKa of 4.0-8.0 for example, histidine and glutamic acid
  • amino acids having a side chain pKa of 4.0-8.0 for example, histidine and glutamic acid
  • substitution into or insertion of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids can performed randomly by methods such as histidine scanning, in which the alanine of alanine scanning known to those skilled in the art is replaced with histidine.
  • Antigen-binding molecules exhibiting a greater value of KD (in an acidic pH range)/KD (in a neutral pH range) or kd (in an acidic pH range)/kd (in a neutral pH range) as compared to before the mutation can be selected from antigen-binding domains or antibodies introduced with random insertions or substitution mutations of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids.
  • antigen-binding molecules containing the mutation into amino acids with a side chain pKa of 4.0-8.0 for example, histidine and glutamic acid
  • unnatural amino acids as described above and whose antigen-binding activity in an acidic pH range is lower than that in a neutral pH range
  • an antigen-binding molecule after the mutation with amino acids having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids has an antigen-binding activity comparable to that before the mutation with amino acids having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids” means that, when taking the antigen-binding activity of an antigen-binding molecule before the mutation with amino acids having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids as 100%, the antigen-binding activity of an antigen-binding molecule after the mutation with amino acids having a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids is at least 10% or more, preferably 50% or more, more preferably 80% or more, and still more preferably 90% or more.
  • the antigen-binding activity after the mutation of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids at pH 7.4 may be higher than that before the mutation of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids at pH 7.4.
  • the antigen-binding activity of an antigen-binding molecule is decreased due to insertion of or substitution into amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids
  • the antigen-binding activity can be made to be comparable to that before the insertion of or substitution into amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids, by introducing a substitution, deletion, addition, and/or insertion of one or more amino acids of the antigen-binding molecule.
  • the present invention also includes antigen-binding molecules whose binding activity has been adjusted to be comparable by substitution, deletion, addition, and/or insertion of one or more amino acids after substitution or insertion of amino acids with a side chain pKa of 4.0-8.0 (for example, histidine and glutamic acid) or unnatural amino acids.
  • a library containing multiple antigen-binding domains or antigen-binding molecules of the present invention whose sequences are different from one another can also be constructed by combining heavy chain variable regions, produced as a randomized variable region sequence library, with light chain variable regions introduced with “at least one amino acid residue that changes the antigen-binding activity of antigen-binding domain or antigen-binding molecule depending on the hydrogen ion concentration condition”.
  • amino acid residues include, but are not limited to, for example, amino acid residues contained in the light chain CDR1.
  • the amino acid residues also include, but are not limited to, for example, amino acid residues contained in the light chain CDR2.
  • amino acid residues also include, but are not limited to, for example, amino acid residues contained in the light chain CDR3.
  • amino acid residues contained in the light chain CDR1 include, but are not limited to, for example, amino acid residue(s) of position(s) 24, 27, 28, 31, 32, and/or 34 according to Kabat numbering in the CDR1 of light chain variable region.
  • amino acid residues contained in the light chain CDR2 include, but are not limited to, for example, amino acid residue(s) of position(s) 50, 51, 52, 53, 54, 55, and/or 56 according to Kabat numbering in the CDR2 of light chain variable region.
  • amino acid residues in the light chain CDR3 include, but are not limited to, for example, amino acid residues of position(s) 89, 90, 91, 92, 93, 94, and/or 95A according to Kabat numbering in the CDR3 of light chain variable region.
  • amino acid residues can be contained alone or can be contained in combination of two or more amino acids as long as they allow the change in the antigen-binding activity of an antigen-binding molecule depending on the hydrogen ion concentration condition.
  • the heavy chain variable region produced as a randomized variable region sequence library is combined with the above-described light chain variable region introduced with “at least one amino acid residue that changes the antigen-binding activity of an antigen-binding molecule depending on the hydrogen ion concentration condition”, it is possible to design so that the flexible residues are contained in the sequence of the light chain variable region in the same manner as described above.
  • the number and position of the flexible residues are not particularly limited to a specific embodiment, as long as the antigen-binding activity of antigen-binding domain or antigen-binding molecule of the present invention changes depending on the hydrogen ion concentration condition.
  • the CDR and/or FR sequences of heavy chain and/or light chain can contain one or more flexible residues.
  • flexible residues to be introduced into the sequences of the light chain variable regions include, but are not limited to, for example, the amino acid residues listed in Tables 3 and 4.
  • amino acid sequences of light chain variable regions other than the flexible residues and amino acid residues that change the antigen-binding activity of an antigen-binding domain or antigen-binding molecule depending on the hydrogen ion concentration condition suitably include, but are not limited to, germ line sequences such as Vk1 (SEQ ID NO: 6), Vk2 (SEQ ID NO: 7), Vk3 (SEQ ID NO: 8), and Vk4 (SEQ ID NO: 9).
  • amino acid residues may be suitably used as the above-described amino acid residues that change the antigen-binding activity of an antigen-binding domain or antigen-binding molecule depending on the hydrogen ion concentration conditions.
  • amino acid residues include amino acids with a side chain pKa of 4.0-8.0.
  • Such electron-releasing amino acids preferably include, for example, naturally occurring amino acids such as histidine and glutamic acid, as well as unnatural amino acids such as histidine analogs (US2009/0035836), m-NO2-Tyr (pKa 7.45), 3,5-Br2-Tyr (pKa 7.21), and 3,5-I2-Tyr (pKa 7.38) (Bioorg. Med. Chem. (2003) 11 (17), 3761-3768).
  • Particularly preferred amino acid residues include, for example, amino acids with a side chain pKa of 6.0-7.0.
  • Such electron-releasing amino acid residues preferably include, for example, histidine.
  • the preferred heavy chain variable region that is used in combination includes, for example, randomized variable region libraries.
  • Known methods are appropriately combined as a method for producing a randomized variable region library.
  • an immune library constructed based on antibody genes derived from animals immunized with specific antigens, patients with infection or persons with an elevated antibody titer in blood as a result of vaccination, cancer patients, or lymphocytes of autoimmune diseases may be suitably used as a randomized variable region library.
  • a synthetic library in which the CDR sequences of V genes from genomic DNA or functional reconstructed V genes are replaced with a set of synthetic oligonucleotides containing the sequences encoding codon sets of an appropriate length can also be suitably used as a randomized variable region library.
  • the CDR3 sequence alone may be replaced because variety in the gene sequence of heavy chain CDR3 is observed.
  • the basis for giving rise to amino acid variations in the variable region of an antigen-binding molecule is to generate variations of amino acid residues of surface-exposed positions of the antigen-binding molecule.
  • the surface-exposed position refers to a position where an amino acid is exposed on the surface and/or contacted with an antigen based on the conformation, structural ensemble, and/or modeled structure of an antigen-binding molecule, and in general, such positions are the CDRs.
  • the surface-exposed positions are preferably determined using the coordinates derived from a three-dimensional model of the antigen-binding molecule using computer programs such as InsightII program (Accelrys).
  • the surface-exposed positions can be determined using algorithms known in the art (for example, Lee and Richards (J. Mol. Biol. (1971) 55, 379-400); Connolly (J. Appl. Cryst. (1983) 16, 548-558)).
  • the surface-exposed positions can be determined based on the information on the three dimensional structure of antibodies using software suitable for protein modeling.
  • Software which is suitably used for this purpose includes the SYBYL biopolymer module software (Tripos Associates).
  • the “size” of probe for use in computation is generally or preferably set at about 1.4 angstrom or less in radius.
  • Pacios Comput. Chem. (1994) 18 (4), 377-386; and J. Mol. Model. (1995) 1, 46-53).
  • a naive library constructed from antibody genes derived from lymphocytes of healthy persons and consisting of naive sequences, which are unbiased repertoire of antibody sequences can also be particularly suitably used as a randomized variable region library (Gejima et al. (Human Antibodies (2002) 11, 121-129); and Cardoso et al. (Scand. J. Immunol. (2000) 51, 337-344)).
  • human FcRn is structurally similar to polypeptides of major histocompatibility complex (MHC) class I, exhibiting 22% to 29% sequence identity to class I MHC molecules (Ghetie et al., Immunol. Today (1997) 18 (12): 592-598).
  • FcRn is expressed as a heterodimer consisting of soluble ⁇ or light chain ( ⁇ 2 microglobulin) complexed with transmembrane ⁇ or heavy chain.
  • FcRn ⁇ chain comprises three extracellular domains ( ⁇ 1, ⁇ 2, and ⁇ 3) and its short cytoplasmic domain anchors the protein onto the cell surface. ⁇ 1 and ⁇ 2 domains interact with the FcRn-binding domain of the antibody Fc region (Raghavan et al., Immunity (1994) 1: 303-315).
  • FcRn is expressed in maternal placenta and york sac of mammals, and is involved in mother-to-fetus IgG transfer. In addition, in neonatal small intestine of rodents, where FcRn is expressed, FcRn is involved in transfer of maternal IgG across brush border epithelium from ingested colostrum or milk. FcRn is expressed in a variety of other tissues and endothelial cell systems of various species. FcRn is also expressed in adult human endothelia, muscular blood vessels, and hepatic sinusoidal capillaries.
  • FcRn is believed to play a role in maintaining the plasma IgG concentration by mediating recycling of IgG to serum upon binding to IgG Typically, binding of FcRn to IgG molecules is strictly pH dependent. The optimal binding is observed in an acidic pH range below 7.0.
  • Human FcRn whose precursor is a polypeptide having the signal sequence of SEQ ID NO: 12 (the polypeptide with the signal sequence is shown in SEQ ID NO: 13) forms a complex with human ⁇ 2-microglobulin in vivo. Soluble human FcRn complexed with ⁇ 2-microglobulin is produced by using conventional recombinant expression techniques. FcRn-binding domain of the present invention can be assessed for their binding activity to such a soluble human FcRn complexed with ⁇ 2-microglobulin.
  • human FcRn refers to a form capable of binding to an FcRn-binding domain of the present invention. Examples include a complex between human FcRn and human ⁇ 2-microglobulin.
  • the binding activity of an FcRn-binding domain contained in an antigen-binding molecule provided by the present invention to FcRn, human FcRn in particular can be measured by methods known to those skilled in the art, as described in the section “Binding Activity” above. Those skilled in the art can appropriately determine the conditions other than pH.
  • the binding activity of antigen-binding domain or antigen-binding molecule comprising the domain to human FcRn can be assessed based on the dissociation constant (KD), apparent dissociation constant (KD), dissociation rate (kd), apparent dissociation rate (kd), and such. These can be measured by methods known to those skilled in the art. For example, Biacore (GE healthcare), Scatchard plot, or flow cytometer may be used.
  • conditions other than the pH are not particularly limited, and can be appropriately selected by those skilled in the art. Measurements can be carried out, for example, at a condition of 37° C. using MES buffer, as described in WO 2009/125825.
  • the human FcRn-binding activity of an FcRn-binding domain or antigen-binding molecule comprising the domain of the present invention can be measured by methods known to those skilled in the art, and may be measured by using, for example, Biacore (GE Healthcare) or such.
  • the binding activity of an FcRn-binding domain or antigen-binding molecule comprising the domain of the present invention to human FcRn can be assessed by flowing, as an analyte, human FcRn, or an FcRn-binding domain or antigen-binding molecule comprising the domain into a chip immobilized with an FcRn-binding domain or antigen-binding molecule comprising the domain, or human FcRn.
  • the acidic pH range presented as the condition for having binding activity between FcRn and an antigen-binding molecule of the present invention or FcRn-binding domain in the molecule generally refers to pH 4.0 to pH 6.5. Preferably it refers to pH 5.5 to pH 6.5, and particularly preferably it refers to pH 5.8 to pH 6.0 which is close to the pH in an early endosome in vivo.
  • the neutral pH range presented as the condition for having binding activity between FcRn and an antigen-binding molecule of the present invention or an FcRn-binding domain included in such a molecule generally refers to pH 6.7 to pH 10.0.
  • Neutral pH range is preferably a range indicated by any pH value from pH 7.0 to pH 8.0, and is preferably selected from pH 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, and 8.0, and is particularly preferably pH 7.4 which is close to the pH in plasma (in blood) in vivo.
  • pH 7.0 can be used instead of pH 7.4.
  • binding affinity between a human FcRn and human FcRn-binding domain or antigen-binding molecule comprising the domain may be assessed at any temperature from 10° C. to 50° C.
  • a temperature from 15° C. to 40° C. is used to determine the binding affinity between a human FcRn and human FcRn-binding domain or antigen-binding molecule comprising the domain.
  • any temperature from 20° C. to 35° C. such as any one of 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, and 35° C. is also equally used to determine the binding affinity between a human FcRn-binding domain or antigen-binding molecule comprising the domain and human FcRn.
  • a temperature of 25° C. is a non-limiting example of an embodiment of the present invention.
  • Antigen-binding molecules of the present invention have an FcRn-binding domain having an activity to bind to FcRn under an acidic pH range condition.
  • the FcRn-binding domain is not particularly limited as long as the antigen-binding molecules have an FcRn-binding activity in an acidic pH range, and it may be a domain that has direct or indirect binding activity to FcRn.
  • Preferred examples of such an FcRn-binding domain include the Fc region of IgG immunoglobulin, albumin, albumin domain 3, anti-FcRn antibody described in Christianson et al.
  • anti-FcRn peptide described in WO 2007/098420 anti-FcRn scaffold molecule, and such which have an activity to directly bind to FcRn, or molecules that bind to IgG or albumin, and such that have an activity to indirectly bind to FcRn.
  • the domain already has FcRn-binding activity in an acidic pH range, it may preferably be used as it is. If the domain does not have or has weak FcRn-binding activity in an acidic pH range, amino acids constituting an FcRn-binding domain in the antigen-binding molecule may be altered to confer FcRn-binding activity.
  • amino acids may be altered in a domain already having FcRn-binding activity in an acidic pH range to increase the FcRn-binding activity in an acidic pH range.
  • the alteration of interest can be identified by comparing the FcRn-binding activities in an acidic pH range before and after the amino acid alteration.
  • An Fc region contains the amino acid sequence derived from the heavy chain constant region of an antibody.
  • An Fc region is a portion of the heavy chain constant region of an antibody, starting from the N terminal end of the hinge region, which corresponds to the papain cleavage site at an amino acid around position 216 according to the EU numbering system, and contains the hinge, CH2, and CH3 domains. While the Fc region may be obtained from human IgG1, it is not limited to a particular subclass of IgG. Examples of such a non-limiting embodiment of the Fc region include the Fc regions of human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or IgG4 (SEQ ID NO: 17).
  • an Fc region of a human IgG immunoglobulin is used as the FcRn-binding domain having binding activity to FcRn under an acidic pH range condition.
  • An Fc region originally having FcRn-binding activity under an acidic pH range condition may be used as it is for this domain, and examples of such Fc regions include Fc regions of human IgGs (IgG1, IgG2, IgG3, or IgG4, and variants thereof).
  • Fc regions having desired FcRn-binding activity may be obtained by altering amino acids of the Fc region.
  • Fc regions having desired or enhanced FcRn-binding activity under an acidic pH range condition may be suitably obtained by altering amino acids in the Fc region.
  • Amino acid alterations of an Fc region that results in such desired binding activity may be determined by comparing the FcRn-binding activity under an acidic pH range condition before and after the amino acid alteration.
  • amino acid alterations may be determined by methods described in the above-mentioned section “Binding activity of an FcRn-binding domain or antigen-binding molecule comprising the domain to FcRn, human FcRn in particular”.
  • Fc regions (starting Fc regions) of an IgG-type immunoglobulin for alteration include, for example, those of human IgGs (IgG1, IgG2, IgG3, and IgG4, and variants thereof).
  • the origin of starting Fc regions is not limited, and they may be obtained from human or any nonhuman organisms.
  • Such organisms preferably include mice, rats, guinea pigs, hamsters, gerbils, cats, rabbits, dogs, goats, sheep, bovines, horses, camels and organisms selected from nonhuman primates.
  • starting Fc regions can also be obtained from cynomolgus monkeys, marmosets, rhesus monkeys, chimpanzees, or humans.
  • Starting Fc regions can be obtained preferably from human IgG1; however, they are not limited to any particular IgG subclass. This means that an Fc region represented by human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or IgG4 (SEQ ID NO: 17) can be used appropriately as a starting Fc region, and herein also means that an Fc region of an arbitrary IgG class or subclass derived from any organisms described above can be preferably used as a starting Fc region.
  • alterations include those with one or more mutations, for example, mutations by substitution of different amino acid residues for amino acids of starting Fc regions, by insertion of one or more amino acid residues into starting Fc regions, or by deletion of one or more amino acids from starting Fc region.
  • the amino acid sequences of altered Fc regions comprise at least a part of the amino acid sequence of a non-native Fc region. Such variants necessarily have sequence identity or similarity less than 100% to their starting Fc region.
  • the variants have amino acid sequence identity or similarity about 75% to less than 100%, more preferably about 80% to less than 100%, even more preferably about 85% to less than 100%, still more preferably about 90% to less than 100%, and most preferably about 95% to less than 100% to the amino acid sequence of their starting Fc region.
  • at least one amino acid is different between a modified Fc region of the present invention and its starting Fc region.
  • Amino acid difference between a modified Fc region of the present invention and its starting Fc region can also be preferably specified based on amino acid differences at above-described particular amino acid positions according to EU numbering.
  • the Fc region has an FcRn-binding activity under an acidic pH range condition or can increase the human FcRn-binding activity under an acidic pH range condition
  • amino acids at any position may be modified into other amino acids.
  • the antigen-binding molecule of the present invention contains the Fc region of human IgG1 as the FcRn-binding domain
  • the resulting Fc region contains a modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting human IgG1 Fc region.
  • Amino acids that allow such modification include, for example, amino acid(s) at position(s) 252, 254, 256, 309, 311, 315, 433, and/or 434 according to EU numbering, and their combination amino acid(s) at position(s) 253, 310, 435, and/or 426 as described in WO 1997/034631.
  • Favorable examples include amino acid(s) at position(s) 238, 252, 253, 254, 255, 256, 265, 272, 286, 288, 303, 305, 307, 309, 311, 312, 317, 340, 356, 360, 362, 376, 378, 380, 382, 386, 388, 400, 413, 415, 424, 433, 434, 435, 436, 439, and/or 447 as indicated by EU numbering as described in WO 2000/042072.
  • amino acids that allow such modification include, amino acid(s) at position(s) 251, 252, 254, 255, 256, 308, 309, 311, 312, 385, 386, 387, 389, 428, 433, 434, and/or 436 according to EU numbering as described in WO 2002/060919.
  • amino acids that allow such modification include, for example, amino acid(s) at position(s) 250, 314, and 428 according to EU numbering as described in WO2004/092219.
  • amino acids that allow such modification include amino acid(s) at position(s) 238, 244, 245, 249, 252, 256, 257, 258, 260, 262, 270, 272, 279, 283, 285, 286, 288, 293, 307, 311, 312, 316, 317, 318, 332, 339, 341, 343, 375, 376, 377, 378, 380, 382, 423, 427, 430, 431, 434, 436, 438, 440, and/or 442 as described in WO 2006/020114.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 includes at least one or more amino acid modifications selected from the group consisting of:
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding in an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including Ile for the amino acid at position 308, Pro for the amino acid at position 309, and/or Glu for the amino acid at position 311 according to EU numbering.
  • Another non-limiting embodiment of this modification may include Thr for the amino acid at position 308, Pro for the amino acid at position 309, Leu for the amino acid at position 311, Ala for the amino acid at position 312, and/or Ala for the amino acid at position 314.
  • another non-limiting embodiment of this modification may include Ile or Thr for the amino acid at position 308, Pro for the amino acid at position 309, Glu, Leu, or Ser for the amino acid at position 311, Ala for the amino acid at position 312, and/or Ala or Leu for the amino acid at position 314.
  • Another non-limiting embodiment of this modification may include Thr for the amino acid at position 308, Pro for the amino acid at position 309, Ser for the amino acid at position 311, Asp for the amino acid at position 312, and/or Leu for the amino acid at position 314.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including Leu for the amino acid at position 251, Tyr for the amino acid at position 252, Ser or Thr for the amino acid at position 254, Arg for the amino acid at position 255, and/or Glu for the amino acid at position 256 according to EU numbering.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including Leu, Met, Phe, Ser, or Thr for the amino acid at position 428, Arg, Gln, His, Ile, Lys, Pro, or Ser for the amino acid at position 433, His, Phe, or Tyr for the amino acid at position 434, and/or Arg, Asn, His, Lys, Met, or Thr for the amino acid at position 436 according to EU numbering.
  • Another non-limiting embodiment of this modification may include His or Met for the amino acid at position 428, and/or His or Met for the amino acid at position 434.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including Arg for the amino acid at position 385, Thr for the amino acid at position 386, Arg for the amino acid at position 387, and/or Pro for the amino acid at position 389 according to EU numbering.
  • Another non-limiting embodiment of this modification may include Asp for the amino acid at position 385, Pro for the amino acid at position 386, and/or Ser for the amino acid at position 389.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 include at least one or more amino acid modifications selected from the group consisting of:
  • Gln or Glu for the amino acid at position 250; and Leu or Phe for the amino acid at position 428 according to EU numbering.
  • the number of amino acids to be modified is not particularly limited; and amino acid may be modified at only one site or amino acids may be modified at two sites.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including Gln for the amino acid at position 250, and/or Leu or Phe for the amino acid at position 428 according to EU numbering.
  • Another non-limiting embodiment of this modification may include Glu for the amino acid at position 250, and/or Leu or Phe for the amino acid at position 428.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 include at least two or more amino acid modifications selected from the group consisting of:
  • the number of amino acids to be modified is not particularly limited; and amino acid may be modified at only two sites or amino acids may be modified at three or more sites.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including Gln for the amino acid at position 307, and Ala or Ser for the amino acid at position 434 according to EU numbering.
  • Another non-limiting embodiment of this modification may include Pro for the amino acid at position 308, and Ala for the amino acid at position 434.
  • another non-limiting embodiment of this modification may include Tyr for the amino acid at position 252, and Ala for the amino acid at position 434.
  • a different non-limiting embodiment of this modification may include Val for the amino acid at position 378, and Ala for the amino acid at position 434.
  • Another different non-limiting embodiment of this modification may include Leu for the amino acid at position 428, and Ala for the amino acid at position 434.
  • Another different non-limiting embodiment of this modification may include Ala for the amino acid at position 434, and Ile for the amino acid at position 436.
  • another non-limiting embodiment of this modification may include Pro for the amino acid at position 308, and Tyr for the amino acid at position 434.
  • another non-limiting embodiment of this modification may include Gln for the amino acid at position 307, and Ile for the amino acid at position 436.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including any one of Gln for the amino acid at position 307, Ala for the amino acid at position 380, and Ser for the amino acid at position 434 according to EU numbering.
  • Another non-limiting embodiment of this modification may include Gln for the amino acid at position 307, Ala for the amino acid at position 380, and Ala for the amino acid at position 434.
  • another non-limiting embodiment of this modification may include Tyr for the amino acid at position 252, Pro for the amino acid at position 308, and Tyr for the amino acid at position 434.
  • a different non-limiting embodiment of this modification may include Asp for the amino acid at position 251, Gln for the amino acid at position 307, and His for the amino acid at position 434.
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 include modification of at least two or more amino acids selected from the group consisting of:
  • a non-limiting embodiment of the modification that results in the effect of enhancing FcRn binding under an acidic pH range condition as compared to the binding activity of the starting Fc region of human IgG1 may be modifications including Ile for the amino acid at position 257, and Ile for the amino acid at position 311 according to EU numbering. Another non-limiting embodiment of this modification may include Ile for the amino acid at position 257, and His for the amino acid at position 434. Another non-limiting embodiment of this modification may include Val for the amino acid at position 376, and His for the amino acid at position 434.
  • Fc ⁇ receptor refers to a receptor capable of binding to the Fc region of monoclonal IgG1, IgG2, IgG3, or IgG4 antibodies, and includes all members belonging to the family of proteins substantially encoded by an Fc ⁇ receptor gene.
  • the family includes Fc ⁇ RI (CD64) including isoforms Fc ⁇ RIa, Fc ⁇ RIb and Fc ⁇ RIc; Fc ⁇ RII (CD32) including isoforms Fc ⁇ RIIa (including allotype H131 and R131), Fc ⁇ RIIb (including Fc ⁇ RIIb-1 and Fc ⁇ RIIb-2), and Fc ⁇ RIIc; and Fc ⁇ RIII (CD16) including isoform Fc ⁇ RIIIa (including allotype V158 and F158) and Fc ⁇ RIIIb (including allotype Fc ⁇ RIIIb-NA1 and Fc ⁇ RIIIb-NA2); as well as all unidentified human Fc ⁇ Rs, Fc ⁇ R isoforms, and allotypes thereof.
  • Fc ⁇ receptor is not limited to these examples.
  • Fc ⁇ R includes those derived from humans, mice, rats, rabbits, and monkeys.
  • Fc ⁇ R may be derived from any organism.
  • Mouse Fc ⁇ R includes, without being limited to, Fc ⁇ RI (CD64), Fc ⁇ RII (CD32), Fc ⁇ RIII (CD16), and Fc ⁇ RIII-2 (Fc ⁇ RIV, CD16-2), as well as all unidentified mouse Fc ⁇ Rs, Fc ⁇ R isoforms, and allotypes thereof.
  • Such preferred Fc ⁇ receptors include, for example, human Fc ⁇ RI (CD64), Fc ⁇ RIIa (CD32), Fc ⁇ RIIb (CD32), Fc ⁇ RIIIa (CD16), and/or Fc ⁇ RIIIb (CD16).
  • the polynucleotide sequence and amino acid sequence of Fc ⁇ RI are shown in SEQ ID NOs: 18 (NM — 000566.3) and 19 (NP — 000557.1), respectively; the polynucleotide sequence and amino acid sequence of Fc ⁇ RIIa are shown in SEQ ID NOs: 20 (BC020823.1) and 21 (AAH20823.1), respectively; the polynucleotide sequence and amino acid sequence of Fc ⁇ RIIb are shown in SEQ ID NOs: 22 (BC146678.1) and 23 (AAI46679.1), respectively; the polynucleotide sequence and amino acid sequence of Fc ⁇ RIIIa are shown in SEQ ID NOs: 24 (BC033678.1) and 25 (AAH33678.1), respectively; and the polynucleotide sequence and amino acid sequence of Fc ⁇ RIIIb are shown in SEQ ID NOs: 26 (BC128562.1) and 27 (AAI28563.1), respectively (RefSeq accession number is shown in each parent
  • an Fc ⁇ receptor has binding activity to the Fc region of a monoclonal IgG1, IgG2, IgG3, or IgG4 antibody can be assessed by ALPHA screen (Amplified Luminescent Proximity Homogeneous Assay), surface plasmon resonance (SPR)-based BIACORE method, and others (Proc. Natl. Acad. Sci. USA (2006) 103(11), 4005-4010), in addition to the above-described FACS and ELISA formats.
  • ALPHA screen Aminescent Proximity Homogeneous Assay
  • SPR surface plasmon resonance
  • Fc ⁇ RI CD64 including Fc ⁇ RIa, Fc ⁇ RIb, and Fc ⁇ RIc
  • Fc ⁇ RIII CD16
  • ⁇ chain that binds to the Fc portion of IgG is associated with common ⁇ chain having ITAM responsible for transduction of intracellular activation signal.
  • the cytoplasmic domain of Fc ⁇ RII CD32 including isoforms Fc ⁇ RIIa (including allotypes H131 and R131) and Fc ⁇ RIIc contains ITAM.
  • Fc ⁇ receptors having the ability to transduce the activation signal as described above are also referred to as activating Fc ⁇ receptors.
  • the intracytoplasmic domain of Fc ⁇ RIIb contains ITIM responsible for transduction of inhibitory signals.
  • the crosslinking between Fc ⁇ RIIb and B cell receptor (BCR) on B cells suppresses the activation signal from BCR, which results in suppression of antibody production via BCR.
  • BCR B cell receptor
  • the crosslinking of Fc ⁇ RIII and Fc ⁇ RIIb on macrophages suppresses the phagocytic activity and inflammatory cytokine production.
  • Fc ⁇ receptors having the ability to transduce the inhibitory signal as described above are also referred to as inhibitory Fc ⁇ receptors.
  • an Fc ⁇ R-binding domain which is included in an antigen-binding molecule of the present invention, to any of the human Fc ⁇ receptors, Fc ⁇ RI, Fc ⁇ RIIa, Fc ⁇ RIIb, Fc ⁇ RIIIa, and/or Fc ⁇ RIIIb, can be confirmed by the above-described FACS and ELISA format, as well as ALPHA Screen (Amplified Luminescent Proximity Homogeneous Assay), a BIACORE method using the surface plasmon resonance (SPR) phenomena, and such (Proc. Natl. Acad. Sci. USA (2006) 103 (11), 4005-4010).
  • ALPHA screen is performed by the ALPHA technology based on the principle described below using two types of beads: donor and acceptor beads.
  • a luminescent signal is detected only when molecules linked to the donor beads interact biologically with molecules linked to the acceptor beads and when the two beads are located in close proximity.
  • the photosensitizer in a donor bead converts oxygen around the bead into excited singlet oxygen.
  • the singlet oxygen diffuses around the donor beads and reaches the acceptor beads located in close proximity, a chemiluminescent reaction within the acceptor beads is induced. This reaction ultimately results in light emission. If molecules linked to the donor beads do not interact with molecules linked to the acceptor beads, the singlet oxygen produced by donor beads do not reach the acceptor beads and chemiluminescent reaction does not occur.
  • a biotin-labeled antigen-binding molecule comprising Fc ⁇ R-binding domain is immobilized to the donor beads and glutathione S-transferase (GST)-tagged Fc ⁇ receptor is immobilized to the acceptor beads.
  • GST glutathione S-transferase
  • Fc ⁇ receptor interacts with an antigen-binding molecule comprising a wild-type Fc ⁇ R-binding domain, inducing a signal of 520 to 620 nm as a result.
  • the antigen-binding molecule having a non-tagged altered Fc ⁇ R-binding domain competes with the antigen-binding molecule comprising a native Fc ⁇ R-binding domain for the interaction with Fc ⁇ receptor.
  • the relative binding affinity can be determined by quantifying the reduction of fluorescence as a result of competition.
  • Methods for biotinylating the antigen-binding molecules such as antibodies using Sulfo-NHS-biotin or the like are known.
  • Appropriate methods for adding the GST tag to an Fc ⁇ receptor include methods that involve fusing polypeptides encoding Fc ⁇ and GST in-frame, expressing the fused gene using cells introduced with a vector to which the gene is operably linked, and then purifying using a glutathione column.
  • the induced signal can be preferably analyzed, for example, by fitting to a one-site competition model based on nonlinear regression analysis using software such as GRAPHPAD PRISM (GraphPad; San Diego).
  • One of the substances for observing their interaction is immobilized as a ligand onto the gold thin layer of a sensor chip.
  • SPR signal When light is shed on the rear surface of the sensor chip so that total reflection occurs at the interface between the gold thin layer and glass, the intensity of reflected light is partially reduced at a certain site (SPR signal).
  • the other substance for observing their interaction is injected as an analyte onto the surface of the sensor chip.
  • the mass of immobilized ligand molecule increases when the analyte binds to the ligand. This alters the refraction index of solvent on the surface of the sensor chip.
  • the change in refraction index causes a positional shift of SPR signal (conversely, the dissociation shifts the signal back to the original position).
  • Binding activities of the Fc ⁇ R-binding domain included in the antigen-binding molecule of the present invention towards any of the human Fc ⁇ receptors, Fc ⁇ RI, Fc ⁇ RIIa, Fc ⁇ RIIb, Fc ⁇ RIIIa, and/or Fc ⁇ RIIIb, can be determined from the amount of binding and KD value for each of the human Fc ⁇ receptors calculated using the Biacore system according to the examples described above.
  • the amount of binding of the various Fc ⁇ Rs to the polypeptides is also represented by values obtained by determining the difference in the RU values of sensorgrams that changed before and after interaction of various Fc ⁇ Rs as the analyte with each polypeptide, and dividing them by differences in the RU values of sensorgrams that changed before and after capturing polypeptides to the sensor chips.
  • An acidic pH range condition or neutral pH range condition may be suitably used for the pH conditions to measure the Fc ⁇ receptor-binding activity of the Fc ⁇ R-binding domain included in the antigen-binding molecule of the present invention or an antigen-binding molecule containing the domain.
  • a neutral pH range as a condition to measure the Fc ⁇ receptor-binding activity of the Fc ⁇ R-binding domain of the present invention or an antigen-binding molecule containing the domain generally refers to pH 6.7 to pH 10.0.
  • an acidic pH range as a condition for the Fc ⁇ R-binding domain of the present invention or an antigen-binding molecule containing the domain to have Fc ⁇ receptor-binding activity generally refers to pH 4.0 to pH 6.5.
  • the binding affinity between the Fc ⁇ R-binding domain or an antigen-binding molecule containing the domain and a human Fc ⁇ receptor can be evaluated at any temperature between 10° C. and 50° C.
  • a temperature between 15° C. and 40° C. is used to determine the binding affinity between the Fc ⁇ R-binding domain or an antigen-binding molecule containing the domain and an Fc ⁇ receptor. More preferably, any temperature between 20° C. and 35° C.
  • any one of 20° C., 21° C., 22° C., 23° C., 24° C., 25° C., 26° C., 27° C., 28° C., 29° C., 30° C., 31° C., 32° C., 33° C., 34° C., and 35° C. can be used in a similar manner to determine the binding affinity between the Fc ⁇ R-binding domain or an antigen-binding molecule containing the domain and an Fc ⁇ receptor.
  • a temperature of 25° C. is a non-limiting example in an embodiment of the present invention.
  • An antigen-binding molecule of the present invention comprises an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition, and an Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor (hereinafter also referred to as a selective Fc ⁇ R-binding domain).
  • Preferred examples of the Fc ⁇ R-binding domain include Fc regions of IgG-type immunoglobulins, Fc ⁇ R-binding domains of IgG-type immunoglobulins, anti-Fc ⁇ R antibodies, and anti-Fc ⁇ R scaffold molecules.
  • a domain originally having Fc ⁇ R-binding activity may be suitably used as it is for the domain.
  • Fc ⁇ R-binding activity can be conferred by altering amino acids forming the Fc ⁇ R-binding domain in the antigen-binding molecule.
  • Fc ⁇ R-binding activity can be increased by altering amino acids in the domain originally having Fc ⁇ R-binding activity.
  • the amino acid alterations of the Fc ⁇ R-binding domain that results in such desired binding activity may be discovered by comparing the Fc ⁇ R-binding activity before and after the amino acid alteration.
  • Fc ⁇ R-binding domains is, for example, the Fc ⁇ R-binding domain included in the Fc region of human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or IgG4 (SEQ ID NO: 17).
  • the Fc region of an IgG antibody is used as the FcRn-binding domain having FcRn-binding activity under an acidic pH range condition
  • the Fc ⁇ R-binding domain included in the Fc region may be used as the Fc ⁇ R-binding domain.
  • an Fc ⁇ R-binding domain of the present invention has selective binding activity can be confirmed by comparing binding activities to the respective Fc ⁇ receptors, determined by the method described in the above-mentioned section on binding activity to Fc ⁇ receptors.
  • An Fc ⁇ R-binding domain with higher binding activity to inhibitory Fc ⁇ receptors than to activating Fc ⁇ receptors may be used as the selective Fc ⁇ R-binding domain included in the antigen-binding molecule provided by the present invention.
  • an Fc ⁇ R-binding domain with higher binding activity to Fc ⁇ RIIb (including Fc ⁇ RIIb-1 and Fc ⁇ RIIb-2) than to an activating Fc ⁇ receptor selected from the group consisting of Fc ⁇ RI (CD64) including Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIII (CD16) including isoforms Fc ⁇ RIIIa (including allotypes V158 and F158) and Fc ⁇ RIIIb (including allotypes Fc ⁇ RIIIb-NA1 and Fc ⁇ RIIIb-NA2), and Fc ⁇ RII (CD32) including isoforms Fc ⁇ RIIa and Fc ⁇ RIIc (including allotypes H131 and R131) may be used as a selective Fc ⁇ R-binding domain included in an antigen-binding molecule provided by the present invention.
  • an Fc ⁇ R-binding domain with higher binding activity to Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2 than to Fc ⁇ RIa, Fc ⁇ RIb, and Fc ⁇ RIc Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131, and/or Fc ⁇ RIIc may be used as a selective Fc ⁇ R-binding domain included in an antigen-binding molecule provided by the present invention.
  • Whether an Fc ⁇ R-binding domain to be tested has selective binding activity to Fc ⁇ receptors can be determined by comparing the value (ratio) obtained by dividing the KD values of the Fc ⁇ R-binding domain for Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131, and/or Fc ⁇ RIIc by the KD values for Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2, wherein the KD values are determined by the method described in the above-mentioned section on binding activity to Fc ⁇ receptors, or more specifically, by comparing the Fc ⁇ R selectivity indices shown in Equation 1.
  • Fc ⁇ R selectivity index KD value for activating Fc ⁇ R/ KD value for inhibitory Fc ⁇ R [Equation 1]
  • activating Fc ⁇ R refers to Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131, and/or Fc ⁇ RIIc, and inhibitory Fc ⁇ R refers to Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2.
  • the activating Fc ⁇ R and inhibitory Fc ⁇ R used for the KD value measurements may be selected from any combination, in a non-limiting embodiment, a value (ratio) obtained by dividing the KD value for Fc ⁇ RIIa including allotype H131 by the KD value for Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2 may be used.
  • the Fc ⁇ R selectivity indices have values of, 1.2 or greater, 1.3 or greater, 1.4 or greater, 1.5 or greater, 1.6 or greater, 1.7 or greater, 1.8 or greater, 1.9 or greater, 2 or greater, 3 or greater, 5 or greater, 6 or greater, 7 or greater, 8 or greater, 9 or greater, 10 or greater, 15 or greater, 20 or greater, 25 or greater, 30 or greater, 35 or greater, 40 or greater, 45 or greater, 50 or greater, 55 or greater, 60 or greater, 65 or greater, 70 or greater, 75 or greater, 80 or greater, 85 or greater, 90 or greater, 95 or greater, 100 or greater, 110 or greater, 120 or greater, 130 or greater, 140 or greater, 150 or greater, 160 or greater, 170 or greater, 180 or greater, 190 or greater, 200 or greater, 210 or greater, 220 or greater, 230 or greater, 240 or greater, 250 or greater, 260 or greater, 270 or greater, 280 or greater, 290 or greater, 300 or greater, 310 or greater,
  • a non-limiting embodiment of the selective Fc ⁇ R-binding domain in an antigen-binding molecule of the present invention includes, for example, Fc regions produced by modifying the Fc ⁇ R-binding domain included in an Fc region presented as human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or IgG4 (SEQ ID NO: 17).
  • An example of a method for producing the modified Fc regions includes the method described in the above-mentioned section on amino acid alterations.
  • Fc regions include an Fc region in which amino acid at position 238 (EU numbering) is Asp or an Fc region in which amino acid at position 328 (EU numbering) is Glu in a human IgG (IgG1, IgG2, IgG3, or IgG4).
  • Fc regions containing a selective Fc ⁇ R-binding domain which are included in the antigen-binding molecules of the present invention and antigen-binding molecules containing such an Fc region may also be Fc regions and antigen-binding molecules containing such an Fc region which maintains or shows reduced binding activity to activating Fc ⁇ R (Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131, and/or Fc ⁇ RIIc) when compared to an Fc region presented as human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or IgG4 (SEQ
  • the degree of the aforementioned reduction in binding activity to activating Fc ⁇ R of an Fc region containing a selective Fc ⁇ R-binding domain included in an antigen-binding molecule of the present invention, and an antigen-binding molecule containing such an Fc region is, for example, 99% or less, 98% or less, 97% or less, 96% or less, 95% or less, 94% or less, 93% or less, 92% or less, 91% or less, 90% or less, 88% or less, 86% or less, 84% or less, 82% or less, 80% or less, 78% or less, 76% or less, 74% or less, 72% or less, 70% or less, 68% or less, 66% or less, 64% or less, 62% or less, 60% or less, 58% or less, 56% or less, 54% or less, 52% or less, 50% or less, 45% or less, 40%
  • the Fc regions containing a selective Fc ⁇ R-binding domain and antigen-binding molecules containing such an Fc region may also be Fc regions and antigen-binding molecules containing such an Fc region which shows enhanced binding activity to inhibitory Fc ⁇ R (Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2) when compared to an Fc region presented as human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or IgG4 (SEQ ID NO: 17) (hereinafter referred to as a wild-type Fc region) and an antigen-binding molecule containing such a wild-type Fc region.
  • a wild-type Fc region an antigen-binding molecule containing such a wild-type Fc region
  • the degree of the aforementioned enhancement in binding activity to inhibitory Fc ⁇ R of an Fc region containing a selective Fc ⁇ R-binding domain included in an antigen-binding molecule of the present invention and an antigen-binding molecule containing such an Fc region is, for example, 101% or greater, 102% or greater, 103% or greater, 104% or greater, 105% or greater, 106% or greater, 107% or greater, 108% or greater, 109% or greater, 110% or greater, 112% or greater, 114% or greater, 116% or greater, 118% or greater, 120% or greater, 122% or greater, 124% or greater, 126% or greater, 128% or greater, 130% or greater, 132% or greater, 134% or greater, 136% or greater, 138% or greater, 140% or greater, 142% or greater, 144% or greater, 146% or greater, 148% or greater, 150% or greater, 155% or
  • the Fc region containing a selective Fc ⁇ R-binding domain included in an antigen-binding molecule of the present invention and the antigen-binding molecule containing such an Fc region may be an Fc region and an antigen-binding molecule containing such an Fc region which maintains or shows reduced binding activity to activating Fc ⁇ R (Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131, and/or Fc ⁇ RIIc) when compared to an Fc region presented as human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or Ig
  • the Fc region containing a selective Fc ⁇ R-binding domain included in an antigen-binding molecule of the present invention and the antigen-binding molecule containing such an Fc region may be an Fc region and an antigen-binding molecule containing such an Fc region with higher degree of enhancement of binding activity to an inhibitory Fc ⁇ receptor (Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2) than to an activating Fc ⁇ receptor (Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131), when compared to an Fc region presented as human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO
  • At least another alteration to the Fc region may be added to the Fc region in which amino acid at position 238 (EU numbering) is Asp and the Fc region in which amino acid at position 328 (EU numbering) is Glu, by the embodiments and such described in the aforementioned section on amino acid alterations.
  • additional alterations may also be added.
  • the additional alterations can be selected from any of substitutions, deletions, and modifications of an amino acid, and combinations thereof. For example, alterations that enhance binding activity to Fc ⁇ RIIb while maintaining or reducing binding activity to Fc ⁇ RIIa (H type) and Fc ⁇ RIIa (R type) may be added. Addition of such alterations improves binding selectivity to Fc ⁇ RIIb over Fc ⁇ RIIa.
  • alterations that improve binding selectivity to Fc ⁇ RIIb over Fc ⁇ RIIa (R type) is favorable, and alterations that improve binding selectivity to Fc ⁇ RIIb over Fc ⁇ RIIa (H type) is more favorable.
  • preferred amino acid substitutions for such alterations include: an alteration by substituting Gly at position 237 (EU numbering) with Trp; an alteration by substituting Gly at position 237 (EU numbering) with Phe; an alteration by substituting Pro at position 238 (EU numbering) with Phe; an alteration by substituting Asn at position 325 (EU numbering) with Met; an alteration by substituting Ser at position 267 (EU numbering) with Ile; an alteration by substituting Leu at position 328 (EU numbering) with Asp; an alteration by substituting Ser at position 267 (EU numbering) with Val; an alteration by substituting Leu at position 328 (EU numbering) with Trp; an alteration by substituting Ser at position 267 (EU numbering) with Trp;
  • the above-mentioned alteration may be at one position, or alterations at two or more positions may be combined.
  • Favorable examples of such alterations are those described in Tables 13 to 14, Tables 16 to 23, and Tables 25 to 27.
  • Fc region produced by altering the Fc ⁇ R-binding domain included in the Fc region presented as human IgG1 (SEQ ID NO: 14), IgG2 (SEQ ID NO: 15), IgG3 (SEQ ID NO: 16), or IgG4 (SEQ ID NO: 17) can be given as an example of another non-limiting embodiment of the selective Fc ⁇ R-binding domain included in the antigen-binding molecules of the present invention.
  • a method for producing the modified Fc regions is, for example, the method described in the above-mentioned section on amino acid alterations.
  • Fc regions include an Fc region in which amino acid at position 238 (EU numbering) is Asp and amino acid at position at 271 (EU numbering) is Gly in a human IgG (IgG1, IgG2, IgG3, or IgG4).
  • An Fc region in which amino acid at position 238 (EU numbering) is Asp and amino acid at position at 271 (EU numbering) is Gly in a human IgG (IgG1, IgG2, IgG3, or IgG4), and antigen-binding molecules containing such an Fc region show higher binding activity to Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2 than to Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131, and/or Fc ⁇ RIIc.
  • At least another alteration to the Fc region may be added to the Fc region in which amino acid at position 238 (EU numbering) is Asp and the amino acid at position 271 (EU numbering) is Gly, by the embodiments and such described in the aforementioned section on amino acid alterations.
  • additional alterations may also be added.
  • the additional alterations can be selected from any of substitutions, deletions, and modifications of an amino acid, and combinations thereof.
  • alterations that maintain or reduce binding activity to activating Fc ⁇ receptors can be added.
  • Fc ⁇ RIa, Fc ⁇ RIb, Fc ⁇ RIc, Fc ⁇ RIIIa including allotype V158, Fc ⁇ RIIIa including allotype F158, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA1, Fc ⁇ RIIIb including allotype Fc ⁇ RIIIb-NA2, Fc ⁇ RIIa including allotype H131, Fc ⁇ RIIa including allotype R131 can be added.
  • Alterations that enhance binding activity to inhibitory Fc ⁇ receptors (Fc ⁇ RIIb-1 and/or Fc ⁇ RIIb-2) while maintaining or reducing binding activity to Fc ⁇ RIIa (H type) and Fc ⁇ RIIa (R type) may be added.
  • An example of a non-limiting embodiment of the altered Fc region comprising a selective Fc ⁇ R-binding domain includes an altered Fc region in which at least one or more amino acid selected from the group consisting of those at positions 233, 234, 237, 264, 265, 266, 267, 268, 269, 272, 274, 296, 326, 327, 330, 331, 332, 333, 355, 356, 358, 396, 409, and 419 (EU numbering) are substituted in the Fc region in which amino acid at position 238 (EU numbering) is Asp and amino acid at position 271 (EU numbering) is Gly in a human IgG (IgG1, IgG2, IgG3, or IgG4).
  • EU numbering amino acid selected from the group consisting of those at positions 233, 234, 237, 264, 265, 266, 267, 268, 269, 272, 274, 296, 326, 327, 330, 331, 332, 333, 355, 356, 358, 3
  • an example of a non-limiting embodiment of the altered Fc region comprising a selective Fc ⁇ R-binding domain is an altered Fc region comprising any one or more of
  • an antigen-binding molecule is used in the broadest sense to refer to a molecule comprising an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition, and an Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor (a selective Fc ⁇ R-binding domain).
  • the antigen-binding molecules include various types of molecules as long as they exhibit antigen-binding activity.
  • Antibodies are examples of molecules in which an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition, and an Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor (a selective Fc ⁇ R-binding domain) are linked together.
  • Antibodies may include single monoclonal antibodies (including agonistic antibodies and antagonistic antibodies), human antibodies, humanized antibodies, chimeric antibodies, and such. Alternatively, when used as antibody fragments, they preferably include antigen-binding domains and antigen-binding fragments (for example, Fab, F(ab′)2, scFv, and Fv).
  • an antigen-binding molecule of the present invention may contain at least some portions of an Fc region that mediates the binding to FcRn and binding to Fc ⁇ receptor and/or complement receptor.
  • the antigen-binding molecule includes, for example, antibodies and Fc fusion proteins.
  • a fusion protein refers to a chimeric polypeptide comprising a polypeptide having a first amino acid sequence that is linked to a polypeptide having a second amino acid sequence that would not naturally link in nature.
  • a fusion protein may comprise the amino acid sequence of at least a portion of an Fc region (for example, a portion of an Fc region responsible for the binding to FcRn, a portion of an Fc region responsible for the binding to Fc ⁇ receptor, or a portion of an Fc region responsible for the binding to complement) and a non-immunoglobulin polypeptide containing, for example, the amino acid sequence of the ligand-binding domain of a receptor or a receptor-binding domain of a ligand.
  • the amino acid sequences may be present in separate proteins that are transported together to a fusion protein, or generally may be present in a single protein; however, they are included in a new rearrangement in a fusion polypeptide. Fusion proteins can be produced, for example, by chemical synthesis, or by genetic recombination techniques to express a polynucleotide encoding peptide regions in a desired arrangement.
  • Respective domains of the present invention such as the antigen-binding domain, the FcRn-binding domain having FcRn-binding activity under an acidic pH range condition, and the Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor (selective Fc ⁇ R-binding domain), can be linked together via linkers or directly via polypeptide bonds.
  • the linkers comprise arbitrary peptide linkers that can be introduced by genetic engineering, synthetic linkers, and linkers disclosed in, for example, Protein Engineering (1996) 9(3), 299-305. However, peptide linkers are preferred in the present invention.
  • the length of the peptide linkers is not particularly limited, and can be suitably selected by those skilled in the art according to the purpose. The length is preferably five amino acids or more (without particular limitation, the upper limit is generally 30 amino acids or less, preferably 20 amino acids or less), and particularly preferably 15 amino acids.
  • such peptide linkers preferably include:
  • Synthetic linkers (chemical crosslinking agents) is routinely used to crosslink peptides, and for example: N-hydroxy succinimide (NHS), disuccinimidyl suberate (DSS), bis(sulfosuccinimidyl) suberate (BS3), dithiobis(succinimidyl propionate) (DSP), dithiobis(sulfosuccinimidyl propionate) (DTSSP), ethylene glycol bis(succinimidyl succinate) (EGS), ethylene glycol bis(sulfosuccinimidyl succinate) (sulfo-EGS), disuccinimidyl tartrate (DST), disulfosuccinimidyl tartrate (sulfo-DST), bis[2-(succinimidoxycarbonyloxy)ethyl]sulfone (BSOCOES), and bis[2-(sulfosuccinimidoxycarbonyloxy)eth
  • linkers for linking the respective domains may all be of the same type, or may be of different types.
  • linkers with peptide tags such as His tag, HA tag, myc tag, and FLAG tag may also be suitably used.
  • linkers with peptide tags such as His tag, HA tag, myc tag, and FLAG tag may also be suitably used.
  • hydrogen bonding, disulfide bonding, covalent bonding, ionic interaction, and properties of binding with each other as a result of combination thereof may be suitably used.
  • the affinity between CH1 and CL of antibody may be used, and Fc regions originating from the above-described bispecific antibodies may also be used for hetero Fc region association.
  • disulfide bonds formed between domains may also be suitably used.
  • polynucleotides encoding the domains are linked in frame.
  • Known methods for linking polynucleotides in frame include techniques such as ligation of restriction fragments, fusion PCR, and overlapping PCR. Such methods can be appropriately used alone or in combination to produce the antigen-binding molecules of the present invention.
  • the terms “linked” and “fused”, or “linkage” and “fusion” are used interchangeably. These terms mean that two or more elements or components such as polypeptides are linked together to form a single structure by any means including the above-described chemical linking means and recombination techniques.
  • linking in frame means linking two or more units of reading frames to form a longer continuous reading frame while maintaining the correct reading frames of the polypeptides.
  • an antibody which is an antigen-binding molecule of the present invention where the antigen-binding domain is linked in frame via peptide bonds without a linker to an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition and the Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor (selective Fc ⁇ R-binding domain), may be used as a preferred antigen-binding molecule of the present application. Examples of non-limiting multiple embodiments of the antigen-binding molecule of the present invention including the antibody structure are shown below:
  • an antibody which comprises F(ab′)2 comprising two variable regions and having antigen-binding activity that varies depending on ion concentration conditions and an Fc region having FcRn-binding activity under an acidic pH range condition and selective binding activity to an Fc ⁇ receptor;
  • variable region having FcRn-binding activity that varies depending on pH conditions can be used preferably as the variable region having FcRn-binding activity under an acidic pH range condition.
  • the antibody is released from FcRn at the cell surface when the antibody bound to FcRn in the acidic endosome is transported to the cell surface and can be easily recycled into the plasma.
  • bispecific antibodies are antibodies comprising two types of variable regions that bind specifically to different epitopes.
  • IgG-type bispecific antibodies can be secreted from a hybrid hybridoma (quadroma) produced by fusing two types of hybridomas that produce IgG antibodies (Milstein et al., Nature (1983) 305, 537-540).
  • bispecific antibody When a bispecific antibody is produced by using recombination techniques such as those described in the above-mentioned section on antibodies, one may adopt a method that introduces genes encoding heavy chains containing the two types of variable regions of interest into cells to co-express them.
  • such a co-expression method will produce a mixture of (i) a combination of a pair of heavy chains in which one of the heavy chains contains a variable region that binds to a first epitope and the other heavy chain contains a variable region that binds to a second epitope, (ii) a combination of a pair of heavy chains which include only heavy chains containing a variable region that binds to the first epitope, and (iii) a combination of a pair of heavy chains which include only heavy chains containing a variable region that binds to the second epitope, which are present at a molecular ratio of 2:1:1. It is difficult to purify antigen-binding molecules containing the desired combination of heavy chains from the mixture of three types of heavy chain combinations.
  • bispecific antibodies comprising the hetero combination of heavy chains can be preferentially secreted by altering the CH3 domain that constitutes a heavy chain using appropriate amino acid substitutions.
  • it is a method of enhancing heterogeneous heavy chain formation and inhibiting homogeneous heavy chain formation by substituting amino acid side chain in one heavy chain CH3 domain with a bulker side chain (knob (meaning “projection”)) while substituting amino acid side chain in the other heavy chain CH3 domain with a smaller side chain (hole (meaning “void”)) so that the “knob” is placed in the “hole”
  • a bulker side chain knob (meaning “projection”)
  • hole meaning “void”
  • bispecific antibodies include those in which a means for regulating polypeptide association or association to form heteromeric multimers constituted by polypeptides is applied to the association of heavy chains.
  • a means for regulating polypeptide association or association to form heteromeric multimers constituted by polypeptides is applied to the association of heavy chains.
  • two polypeptides constituting an Fc region derived from a bispecific antibody described above can be suitably used as the Fc region contained in an antigen-binding molecule. More specifically, two polypeptides constituting an Fc region may be suitably used, in which, of the amino acid sequence of one of the polypeptides, the amino acid at position 349 as indicated by EU numbering is Cys and the amino acid at position 366 is Trp, and of the amino acid sequence of the other of the polypeptides, the amino acid at position 356 as indicated by EU numbering is Cys, the amino acid at position 366 is Ser, the amino acid at position 368 is Ala, and the amino acid at position 407 is Val.
  • two polypeptides constituting an Fc region in which, of the amino acid sequence of one of the polypeptides, the amino acid at position 409 according to EU numbering is Asp, and of the amino acid sequence of the other of the polypeptides, the amino acid at position 399 according to EU numbering is Lys, may be suitably used as the Fc region.
  • the amino acid at position 409 may be Glu instead of Asp
  • the amino acid at position 399 may be Arg instead of Lys.
  • Asp may suitably be added as amino acid at position 360 or Asp may suitably be added as amino acid at position 392.
  • two polypeptides constituting an Fc region in which, of the amino acid sequence of one of the polypeptides, the amino acid at position 370 according to EU numbering is Glu, and of the amino acid sequence of the other of the polypeptides, the amino acid at position 357 according to EU numbering is Lys, may be suitably used as the Fc region.
  • two polypeptides constituting an Fc region in which, of the amino acid sequence of one of the polypeptides, the amino acid at position 439 according to EU numbering is Glu, and of the amino acid sequence of the other of the polypeptides, the amino acid at position 356 according to EU numbering is Lys, may be suitably used as the Fc region.
  • any of the embodiments indicated below, in which the above have been combined, may be suitably used as the Fc region:
  • two polypeptides constituting an Fc region in which, of the amino acid sequence of one of the polypeptides, the amino acid at position 356 according to EU numbering is Lys, and of the amino acid sequence of the other of the polypeptides, the amino acid at position 435 according to EU numbering is Arg and the amino acid at position 439 is Glu, may also be suitably used.
  • two polypeptides constituting an Fc region in which, of the amino acid sequence of one of the polypeptides, the amino acid at position 356 according to EU numbering is Lys and the amino acid at position 357 is Lys, and of the amino acid sequence of the other of the polypeptides, the amino acid at position 370 according to EU numbering is Glu, the amino acid at position 435 is Arg, and the amino acid at position 439 is Glu, may also be suitably used.
  • the CrossMab technology which is known as a technology for associating heterologous light chains, in which a light chain forming a variable region that binds to a first epitope and a light chain forming a variable region that binds to a second epitope are respectively associated with a heavy chain forming a variable region that binds to the first epitope and a heavy chain forming a variable region that binds to the second epitope
  • a light chain forming a variable region that binds to a first epitope and a heavy chain forming a variable region that binds to the second epitope may also be used to produce the antigen-binding molecules provided by the present invention.
  • the “ability to eliminate antigens in plasma” refers to the ability to eliminate from the plasma antigens that are present in the plasma when the antigen-binding molecules are administered in vivo or when the antigen-binding molecules are secreted in vivo.
  • “ability of antigen-binding molecules to eliminate antigens in plasma is increased” means that when the antigen-binding molecules are administered, the rate of antigen elimination from plasma is accelerated as compared to when an antigen-binding molecule comprising an antigen-binding domain whose antigen-binding activity does not vary depending on ion concentrations, an antigen-binding molecule comprising an FcRn-binding domain without FcRn-binding activity under an acidic pH range condition, or an antigen-binding molecule comprising an Fc ⁇ receptor-binding domain without selective binding activity to an Fc ⁇ receptor is administered.
  • Whether or not the ability of an antigen-binding molecule to eliminate antigens in the plasma increased can be determined, for example, by administering soluble antigens and the antigen-binding molecule in vivo, and then measuring the plasma concentration of the soluble antigen after administration.
  • the concentration of the soluble antigens in the plasma is decreased after administration of the soluble antigens and the antigen-binding molecules comprising an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions, the FcRn-binding domain having FcRn-binding activity under an acidic pH range condition, and an Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor (a selective Fc ⁇ R-binding domain)
  • the ability of the antigen-binding molecules to eliminate antigens in the plasma is judged to be increased.
  • the soluble antigen may be an antigen that is bound to an antigen-binding molecule or an antigen that is not bound to an antigen-binding molecule in the plasma, and its concentration can be determined as a “plasma concentration of the antigen bound to the antigen-binding molecule” or as a “plasma concentration of the antigen not bound to the antigen-binding molecule”, respectively (the latter is synonymous with “free antigen concentration in plasma”).
  • the “total antigen concentration in plasma” means the sum of concentrations of the antigen-binding molecule-bound antigen and the antigen not bound by an antigen-binding molecule, or the “free antigen concentration in plasma” which is the concentration of the antigen not bound by an antigen-binding molecule.
  • the soluble antigen concentration can be determined as the “total antigen concentration in plasma”.
  • Various methods for measuring the “total antigen concentration in plasma” or the “free antigen concentration in plasma” are well known in the art as described hereinafter.
  • “enhancement of pharmacokinetics”, “improvement of pharmacokinetics”, and “superior pharmacokinetics” can be restated as “enhancement of plasma (blood) retention”, “improvement of plasma (blood) retention”, “superior plasma (blood) retention”, and “prolonged plasma (blood) retention”. These terms are synonymous.
  • “improvement of pharmacokinetics” means not only prolongation of the period until elimination from the plasma (for example, until the antigen-binding molecule is degraded intracellularly or the like and cannot return to the plasma) after administration of the antigen-binding molecule to humans, or non-human animals such as mice, rats, monkeys, rabbits, and dogs, but also prolongation of the plasma retention of the antigen-binding molecule in a form that allows antigen binding (for example, in an antigen-free form of the antigen-binding molecule) during the period of administration to elimination due to degradation.
  • Human IgG having native Fc region can bind to FcRn from non-human animals.
  • mouse can be preferably used to be administered in order to confirm the property of the antigen-binding molecule of the invention since human IgG having native Fc region can bind to mouse FcRn stronger than to human FcRn (Int Immunol. (2001) 13(12): 1551-1559).
  • mouse in which its native FcRn genes are disrupted and a transgene for human FcRn gene is harbored to be expressed can also be preferably used to be administered in order to confirm the property of the antigen-binding molecule of the invention described hereinafter.
  • “improvement of pharmacokinetics” also includes prolongation of the period until elimination due to degradation of the antigen-binding molecule not bound to antigens (the antigen-free form of antigen-binding molecule).
  • the antigen-binding molecule in plasma cannot bind to a new antigen if the antigen-binding molecule has already bound to an antigen.
  • the longer the period that the antigen-binding molecule is not bound to an antigen the longer the period that it can bind to a new antigen (the higher the chance of binding to another antigen).
  • the plasma concentration of the antigen-free form of antigen-binding molecule can be increased and the period that the antigen is bound to the antigen-binding molecule can be prolonged by accelerating the antigen elimination from the plasma by administration of the antigen-binding molecule.
  • “improvement of the pharmacokinetics of antigen-binding molecule” in the present invention includes the improvement of a pharmacokinetic parameter of the antigen-free form of the antigen-binding molecule (any of prolongation of the half-life in plasma, prolongation of mean retention time in plasma, and impairment of plasma clearance), prolongation of the period that the antigen is bound to the antigen-binding molecule after administration of the antigen-binding molecule, and acceleration of antigen-binding molecule-mediated antigen elimination from the plasma.
  • the improvement of pharmacokinetics of antigen-binding molecule can be assessed by determining any one of the parameters, half-life in plasma, mean plasma retention time, and plasma clearance for the antigen-binding molecule or the antigen-free form thereof (“Pharmacokinetics: Enshu-niyoru Rikai (Understanding through practice)” Nanzando).
  • the plasma concentration of the antigen-binding molecule or antigen-free form thereof is determined after administration of the antigen-binding molecule to mice, rats, monkeys, rabbits, dogs, or humans. Then, each parameter is determined.
  • the plasma half-life or mean plasma retention time is prolonged, the pharmacokinetics of the antigen-binding molecule can be judged to be improved.
  • the parameters can be determined by methods known to those skilled in the art.
  • the parameters can be appropriately assessed, for example, by noncompartmental analysis using the pharmacokinetics analysis software WinNonlin (Pharsight) according to the appended instruction manual.
  • the plasma concentration of antigen-free antigen-binding molecule can be determined by methods known to those skilled in the art, for example, using the assay method described in Clin Pharmacol. 2008 April; 48 (4): 406-417.
  • “improvement of pharmacokinetics” also includes prolongation of the period that an antigen is bound to an antigen-binding molecule after administration of the antigen-binding molecule. Whether the period that an antigen is bound to the antigen-binding molecule after administration of the antigen-binding molecule is prolonged can be assessed by determining the plasma concentration of free antigen. The prolongation can be judged based on the determined plasma concentration of free antigen or the time period required for an increase in the ratio of free antigen concentration to the total antigen concentration.
  • the plasma concentration of free antigen not bound to the antigen-binding molecule or the ratio of free antigen concentration to the total concentration can be determined by methods known to those skilled in the art, for example, by the method used in Pharm Res. 2006 January; 23 (1): 95-103.
  • an antigen exhibits a particular function in vivo
  • whether the antigen is bound to an antigen-binding molecule that neutralizes the antigen function can be assessed by testing whether the antigen function is neutralized. Whether the antigen function is neutralized can be assessed by assaying an in vivo marker that reflects the antigen function.
  • Whether the antigen is bound to an antigen-binding molecule that activates the antigen function (agonistic molecule) can be assessed by assaying an in vivo marker that reflects the antigen function.
  • Determination of the plasma concentration of free antigen and ratio of the amount of free antigen in plasma to the amount of total antigen in plasma, in vivo marker assay, and such measurements are not particularly limited; however, the assays are preferably carried out after a certain period of time has passed after administration of the antigen-binding molecule.
  • the period after administration of the antigen-binding molecule is not particularly limited; those skilled in the art can determine the appropriate period depending on the properties and the like of the administered antigen-binding molecule.
  • Such periods include, for example, one day after administration of the antigen-binding molecule, three days after administration of the antigen-binding molecule, seven days after administration of the antigen-binding molecule, 14 days after administration of the antigen-binding molecule, and 28 days after administration of the antigen-binding molecule.
  • the concept “plasma antigen concentration” comprises both “total antigen concentration in plasma” which is the sum of antigen-binding molecule bound antigen and non-bound antigen concentration or “free antigen concentration in plasma” which is antigen-binding molecule non-bound antigen concentration.
  • the total antigen concentration in the plasma can be lowered by administration, as antigen-binding molecule, of the antigen-binding molecule of the present invention by 2-fold, 5-fold, 10-fold, 20-fold, 50-fold, 100-fold, 200-fold, 500-fold, 1,000-fold, or even higher as compared to administration of an antigen-binding molecule containing an antigen-binding domain whose antigen-binding activity is ion concentration-independent or an antigen-binding molecule containing an Fc region with an impaired Fc ⁇ R-binding activity, or compared to when the antigen-binding domain molecule of the present invention is not administered.
  • Molar antigen/antigen-binding molecule ratio can be calculated as shown below:
  • A Molar antigen concentration at each time point value
  • B Molar antigen-binding molecule concentration at each time point value
  • Molar antigen/antigen-binding molecule ratio can be calculated as described above.
  • a 2-fold, 5-fold, 10-fold, 20-fold, 50-fold, 100-fold, 200-fold, 500-fold, 1,000-fold or even greater reduction of molar antigen/antigen-binding molecule ratio can be achieved by administration of an antigen-binding molecule of the present invention as compared to when an antigen-binding molecule comprising an antigen-binding domain whose antigen-binding activity does not vary depending on ion concentrations, an antigen-binding molecule comprising an FcRn-binding domain without FcRn-binding activity under an acidic pH range condition, or an antigen-binding molecule comprising an Fc ⁇ receptor-binding domain without selective binding activity to an Fc ⁇ receptor is administered as the antigen-binding molecule.
  • an antigen-binding molecule comprising an antigen-binding domain whose antigen-binding activity does not vary depending on ion concentrations, an antigen-binding molecule comprising an FcRn-binding domain without FcRn-binding activity under an acidic pH range condition, or an antigen-binding molecule comprising an Fc ⁇ receptor-binding domain without selective binding activity to an Fc ⁇ receptor is used as a reference antigen-binding molecule to be compared with the antigen-binding molecules of the present invention.
  • mixture of antigen-binding molecule and antigen is administered to the mouse.
  • infusion pump containing antigen solution is implanted to the mouse to achieve constant plasma antigen concentration, and then antigen-binding molecule is injected to the mouse.
  • Test antigen-binding molecule is administered at same dosage. Total antigen concentration in plasma, free antigen concentration in plasma and plasma antigen-binding molecule concentration is measured at appropriate time point using method known to those skilled in the art.
  • an antigen-binding molecule when an antigen-binding molecule does not cross-react with a mouse counterpart antigen, total antigen concentration in plasma or decrease in antigen/antibody mole ratio can be assessed by either the antigen-antibody simultaneous injection model or the steady-state antigen injection model using the conventionally used C57BL/6J mice (Charles River Japan).
  • the antigen-binding molecule can simply be injected to conventionally used C57BL/6J mice (Charles River Japan) to carry out the assessment.
  • mice In the co-injection model, a mixture of the antigen-binding molecule and antigen is administered to mice.
  • an infusion pump filled with an antigen solution is embedded into mice to achieve a constant plasma antigen concentration, and then the antigen-binding molecule is injected into the mice.
  • Test antigen-binding molecules are administered at the same dose.
  • the total antigen concentration in plasma, free antigen concentration in plasma, and antigen-binding molecule concentration in plasma are measured at appropriate time points using methods known to those skilled in the art.
  • Total or free antigen concentration in plasma and molar antigen/antigen-binding molecule ratio can be measured at 2, 4, 7, 14, 28, 56, or 84 days after administration to evaluate the long-term effect of the present invention.
  • a long term plasma antigen concentration is determined by measuring total or free antigen concentration in plasma and molar antigen/antigen-binding molecule ratio at 2, 4, 7, 14, 28, 56, or 84 days after administration of an antigen-binding molecule in order to evaluate the property of the antigen-binding molecule of the present invention.
  • Whether the reduction of plasma antigen concentration or molar antigen/antigen-binding molecule ratio is achieved by antigen-binding molecule described in the present invention can be determined by the evaluation of the reduction at any one or more of the time points described above.
  • Total or free antigen concentration in plasma and molar antigen/antigen-binding molecule ratio can be measured at 15 minutes, 1, 2, 4, 8, 12, or 24 hours after administration to evaluate the short-term effect of the present invention.
  • a short term plasma antigen concentration is determined by measuring total or free antigen concentration in plasma and molar antigen/antigen-binding molecule ratio at 15 minutes, 1, 2, 4, 8, 12, or 24 hours after administration of an antigen-binding molecule in order to evaluate the property of the antigen-binding molecule of the present invention.
  • Route of administration of an antigen-binding molecule of the present invention can be selected from intradermal, intravenous, intravitreal, subcutaneous, intraperitoneal, parenteral and intramuscular injection.
  • the plasma retention in human is difficult to determine, it may be predicted based on the plasma retention in mice (for example, normal mice, human antigen-expressing transgenic mice, human FcRn-expressing transgenic mice) or monkeys (for example, cynomolgus monkeys).
  • the improvement of the pharmacokinetics and prolonged plasma retention of an antigen-binding molecule in the present invention means improvement of any pharmacokinetic parameter (any of prolongation of the half-life in plasma, prolongation of mean retention time in plasma, reduction of plasma clearance, and bioavailability) after in vivo administration of the antigen-binding molecule, or an increase in the concentration of the antigen-binding molecule in the plasma in an appropriate time after administration. It may be determined by measuring any parameter such as half-life in plasma, mean retention time in plasma, plasma clearance, and bioavailability of the antigen-binding molecule (Pharmacokinetics: Enshu-niyoru Rikai (Understanding through practice), (Nanzando)).
  • mice normal mice and human FcRn transgenic mice
  • rats, monkeys, rabbits, dogs, humans, and so on the concentration of the antigen-binding molecule in the plasma is determined and each of the parameters is calculated
  • the pharmacokinetics of the antigen-binding molecule can be judged to be improved when the plasma half-life or mean retention time in the plasma is prolonged.
  • These parameters can be determined by methods known to those skilled in the art. For example, the parameters can be appropriately assessed by non-compartmental analysis using pharmacokinetics analysis software WinNonlin (Pharsight) according to the attached instruction manual.
  • Fc ⁇ Rs Four types of Fc ⁇ Rs, Fc ⁇ RI, Fc ⁇ RIIb, Fc ⁇ RIII, and Fc ⁇ RIV, have been identified in mice. In humans as well, as corresponding Fc ⁇ Rs, Fc ⁇ RI, Fc ⁇ RIIa, Fc ⁇ RIIb, Fc ⁇ RIIIa, Fc ⁇ RIIIa, and Fc ⁇ RIIIb have been identified. Fc ⁇ RIIb which is considered to be the only inhibitory type among these Fc ⁇ Rs is conserved in both humans and mice.
  • Fc ⁇ Rs except for Fc ⁇ RIIIb, transmit activation signals via the immunoreceptor tyrosine-based activating motif (ITAM), whereas Fc ⁇ RIIb transmits inhibitory signals via the immunoreceptor tyrosine-based inhibitory motif (ITIM) present inside the cells (Nat. Rev. Immunol. (2008) 8, 34-47).
  • ITAM immunoreceptor tyrosine-based activating motif
  • ITIM immunoreceptor tyrosine-based inhibitory motif
  • Fc ⁇ RIIb1 and Fc ⁇ RIIb2 have been reported as splicing variants of Fc ⁇ RIIb. In both humans and mice, Fc ⁇ RIIb1 has a longer intracellular domain than Fc ⁇ RIIb2. Fc ⁇ RIIb1 has been confirmed to be expressed in B cells, and Fc ⁇ RIIb2 has been confirmed to be expressed in macrophages, mast cells, dendritic cells, basophils, neutrophils, and eosinophils (J. Clin. Immunol. (2005) 25 (1), 1-18).
  • Fc ⁇ RIIb is considered to regulate humoral immunity in mice as in humans.
  • Fc ⁇ RIIb1 and Fc ⁇ RIIb2 exist as splicing variants of Fc ⁇ RIIb, but it is reported that the latter is mainly involved in the endocytosis of an immune complex of an antibody and antigen (J. Immunol. (1994), 152 574-585; Science (1992) 256, 1808-1812; Cell (1989) 58, 317-327).
  • mouse Fc ⁇ RIIb2 has been reported to be incorporated into a clathrin-coated pit and endocytosed (Cell (1989) 58, 317-327). Furthermore, it has been reported that a dileucine motif is necessary for Fc ⁇ RIIb2-mediated endocytosis, and the dileucine motif is conserved in both humans and mice (EMBO J. (1994) 13 (13), 2963-2969). From these, Fc ⁇ RIIb2 may have an endocytotic ability in humans as in mice.
  • Fc ⁇ RIIb1 has an inserted sequence in its intracellular domain that is not found in Fc ⁇ RIIb2. It is considered that this sequence inhibits the uptake of Fc ⁇ RIIb1 into a clathrin-coated pit, and as a result endocytosis is inhibited (J. Cell. Biol. (1992) 116, 875-888; J. Cell. Biol. (1989) 109, 3291-3302).
  • Fc ⁇ RIIb1 has an insertion sequence at a site similar to that of Fc ⁇ RIIb2 as in mice; therefore, difference in the endocytotic ability between Fc ⁇ RIIb1 and Fc ⁇ RIIb2 is presumed to be caused by a similar mechanism. Furthermore, in both humans and mice, approximately 40% of immune complexes on the cell surface is reported to be taken up into the cell in 20 minutes (Mol. Immunol. (2011) 49, 329-337; Science (1992) 256, 1808-1812). Therefore, in humans as well, Fc ⁇ RIIb2 is presumed to uptake immune complexes into cells at rates similar to those in mice.
  • Fc ⁇ RIIb is the only one that has ITIM inside the cell in both humans and mice among the Fc ⁇ R family and the distribution of expressing cells are the same, it is presumed that its function in immune control is similar. Furthermore, considering the fact that immune complexes are taken up into cells at similar rates in humans and mice, antigen elimination effects of antibodies mediated by Fc ⁇ RIIb in humans may be predictable using mice.
  • Antigen-binding molecules mF44 and mF46 have properties of binding to soluble antigens in a pH-dependent manner, and have enhanced affinity to mouse Fc ⁇ RIIb and Fc ⁇ RIII compared to mIgG1 which is an antigen-binding molecule having the property of binding to a soluble antigen in a pH-dependent manner. Indeed, it is shown in Example 5 that antigen clearance increased when mF44 or mF46 was administered to normal mice compared to when mIgG1 was administered.
  • Example 6 Furthermore, in the later-described Example 6, a similar experiment was carried out using Fc receptor ⁇ chain-deficient mice. It has been reported that Fc ⁇ Rs other than Fc ⁇ RIIb are expressed only in the co-presence of a gamma chain in mice. Thus, only Fc ⁇ RIIb is expressed in the Fc receptor ⁇ chain-deficient mice.
  • Administration of mF44 or mF46, which are antigen-binding molecules having the property of binding to soluble antigens in a pH-dependent manner, to Fc receptor ⁇ chain-deficient mice enables assessment of antigen elimination-acceleration effects when Fc ⁇ RIIb-binding is selectively enhanced.
  • Example 6 From the results of Example 6, when mF44 or mF46 (which are antigen-binding molecules having the property of binding to soluble antigens in a pH-dependent manner) was administered to Fc receptor ⁇ chain-deficient mice, antigen clearance was shown to increase compared to when mIgG1 (which is an antigen-binding molecule having the property of binding to soluble antigens in a pH-dependent manner) was administered to the mice. Furthermore, the results of Example 6 shows that when administered to Fc receptor ⁇ chain-deficient mice, mF44 or mF46 cause similar degrees of antigen elimination as when administered to normal mice.
  • Example 6 a similar experiment was performed using Fc ⁇ RIII-deficient mice. Since mIgG1, mF44, and mF46 bind only to Fc ⁇ RIIb and Fc ⁇ RIII among the mFc ⁇ Rs, administration of the antibodies to Fc ⁇ RIII-deficient mice enables assessment of antigen elimination-accelerating effects when Fc ⁇ RIIb-binding is selectively enhanced.
  • the results of Example 6 indicate that when mF44 or mF46 was administered to Fc ⁇ RIII-deficient mice, antigen clearance was increased compared to when mIgG1 was administered to the mice antigen clearance. Furthermore, the results of Example 6 showed that when administered to Fc ⁇ RIII-deficient mice, mF44 and mF46 cause similar degrees of antigen elimination as when administered to Fc receptor ⁇ chain-deficient mice and when administered to normal mice.
  • Fv4-IgG1 is an antibody that results from conferring to a humanized anti-IL-6 receptor antibody H54/L28-IgG1 the activity to bind to the antigen in a pH-dependent manner, i.e., altering the variable region to confer the property to bind to an antigen at pH 7.4 and dissociate from the antigen at pH 5.8.
  • WO 2009/125825 showed that the elimination of soluble human IL-6 receptor is greatly accelerated in mice co-administered with Fv4 IgG1 and soluble human IL-6 receptor as the antigen as compared to mice co-administered with H54/L28-IgG1 and the antigen.
  • heavy-chain H54-IgG1 and light-chain L28-CK included in H54/L28-IgG1 are shown in SEQ ID NO: 36 and SEQ ID NO: 37, respectively; and heavy chain VH3-IgG1 and light-chain VL3-CK included in Fv4-IgG1 are shown in SEQ ID NO: 38 and SEQ ID NO: 39, respectively.
  • the dissociated soluble human IL-6 receptor is degraded in the lysosome, elimination of the soluble human IL-6 receptor can be greatly accelerated, and the antibody Fv4-IgG1 which binds to the soluble human IL-6 receptor in a pH-dependent manner is recycled to the plasma after binding to FcRn in the endosome. Since the recycled antibody can bind to a soluble human IL-6 receptor again, binding to the antigen (soluble human IL-6 receptor) and recycling to the plasma via FcRn are repeated. As a result, a single antibody molecule can repeatedly bind to the soluble human IL-6 receptor multiple times ( FIG. 1 ).
  • plasma concentration of the soluble antigen can be reduced greatly by administration of an antigen-binding molecule with enhanced Fc ⁇ R-binding activity of the Fc ⁇ receptor-binding domain included in the antigen-binding molecule which comprises an antigen-binding domain in which antigen-binding activity changes depending on the ion concentration condition such as pH, an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition, and an Fc ⁇ receptor-binding domain.
  • an antigen-binding molecule with enhanced binding to Fc ⁇ Rs which comprises an antigen-binding domain in which antigen-binding activity changes depending on the ion-concentration condition such as pH and an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition
  • an antigen-binding domain with enhanced binding to Fc ⁇ Rs which comprises an antigen-binding domain in which antigen-binding activity changes depending on the ion-concentration condition such as pH and an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition
  • an antigen-binding molecule such as Fv4-IgG1 comprising an antigen-binding domain in which antigen-binding activity changes depending on the ion-concentration condition may be able to bind repeatedly to the antigen multiple times, but the effect of dissociating the soluble antigen in the endosome to accelerate the antigen elimination from plasma may be dependent on the rate of uptake of the complex of the antigen and antigen-binding molecule into the endosome.
  • the antigen-binding molecules with enhanced binding activities to various Fc ⁇ Rs which comprise an antigen-binding domain in which antigen-binding activity changes depending on the ion-concentration condition, are actively taken up into cells by binding to various Fc ⁇ Rs expressed on the cell membrane, and can circulate in the plasma again by recycling via binding between FcRn and the FcRn-binding domain in the molecule having binding activity to FcRn under an acidic pH range condition.
  • the effect of accelerating elimination of soluble antigens in plasma may be more pronounced than that of antigen-binding molecules whose binding activities to various Fc ⁇ Rs are not enhanced.
  • Fc ⁇ R-binding activities of antibodies that bind to membrane antigens have an important role in cytotoxic activity of the antibodies. Therefore, when cytotoxic activity is necessary for an antibody to be used as a pharmaceutical, a human IgG1 isotype which has high Fc ⁇ R-binding activity is used, and the technique of enhancing the Fc ⁇ R-binding activities of the antibody to enhance the cytotoxic activity of the antibody is widely utilized.
  • the concentration of soluble antigens in the plasma was found to be greatly reduced in individuals administered with antigen-binding molecules with enhanced Fc ⁇ R-binding activities and comprising an antigen-binding domain whose binding activity to soluble antigens changes depending on the ion concentration condition. More specifically, by combining an FcRn-binding domain having an FcRn-binding activity under an acidic pH range condition and an antigen-binding domain whose binding to soluble antigens changes depending on the ion concentration condition, which are domains included in antigen-binding molecules targeting soluble antigens, an advantage of enhancing binding to Fc ⁇ R was found for the first time.
  • An example of a non-limiting embodiment of the use of an antigen-binding molecule for the method of eliminating the antigens from plasma includes use of the antigen-binding molecule for a so-called ex vivo method of eliminating the antigens from plasma, which comprises contacting the antigen-binding molecule of the present invention with plasma isolated from subjects to allow forming immune complexes, and allowing the immune complexes to contact cells expressing Fc ⁇ receptors and FcRn.
  • the speed of antigen elimination from the plasma can also be promoted by substituting/combining a method for administering antigen-binding molecules in vivo with a so-called ex vivo method, in which the plasma containing antigen-binding molecules and antigens that bind to the antigen-binding molecules is temporarily taken out of the body and then contacted with cells expressing FcRn and Fc ⁇ receptors for a certain period of time, and the plasma containing extracellularly recycled (or re-secreted or re-circulated) antigen-binding molecules that are not bound to antigen is returned to the body.
  • an example of a non-limiting embodiment of the use of an antigen-binding molecule in the method provided by the present invention for eliminating antigens from plasma includes use of the antigen-binding molecule in a so-called ex vivo method for eliminating antigens from the plasma, which includes contacting an immune complex present in the plasma isolated from a subject to whom the antigen-binding molecules of the present invention are administered with cells expressing FcRn and Fc ⁇ receptors.
  • Whether or not the antigen is eliminated from plasma can be confirmed, for example, by assessing whether or not the rate of antigen elimination in plasma is accelerated as compared to when an antigen-binding molecule comprising an antigen-binding domain whose antigen-binding activity does not vary depending on ion concentrations, an antigen-binding molecule comprising an FcRn-binding domain without FcRn-binding activity under an acidic pH range condition, or an antigen-binding molecule comprising an Fc ⁇ receptor-binding domain without selective binding activity to an Fc ⁇ receptor is used as a control instead of an antigen-binding molecule of the present invention.
  • the present invention provides a method for producing an antigen-binding molecule having the function of eliminating antigens in plasma, wherein the method comprises the steps of (a) to (e) below:
  • step (a) obtaining an antigen-binding domain whose antigen-binding activity varies depending on ion concentration conditions; (b) obtaining a gene encoding the antigen-binding domain selected in step (a); (c) operably linking the gene obtained in step (b) with a gene encoding an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition and an Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor; (d) culturing host cells containing the gene operably linked in step (c); and (e) isolating an antigen-binding molecule from the culture solution obtained in step (d).
  • the polynucleotide after isolating a polynucleotide encoding an antigen-binding domain whose binding activity changes depending on the condition selected as described above, the polynucleotide is inserted into an appropriate expression vector.
  • the antigen-binding domain is an antibody variable region
  • the cDNA is digested with restriction enzymes that recognize the restriction sites inserted at the two ends of the cDNA.
  • the restriction enzymes recognize and digest a nucleotide sequence that appears at a low frequency in the nucleotide sequence composing the gene of the antigen-binding molecule.
  • restriction enzymes that provide cohesive ends are preferably inserted to insert a single copy of a digested fragment into the vector in the correct orientation.
  • the cDNA encoding a variable region of an antigen-binding molecule digested as described above is inserted into an appropriate expression vector to obtain an expression vector for the antigen-binding molecule of the present invention.
  • the polynucleotide encoding an antigen-binding domain obtained as described above is operably linked to the gene encoding an FcRn-binding domain having FcRn-binding activity under an acidic pH range condition and an Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor, which are described in the sections “FcRn-binding domain having FcRn-binding activity under an acidic pH range condition” and “Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor”, respectively.
  • the genes can be directly linked in-frame, or the polynucleotides encoding each domain may be linked in-frame via linkers. In addition to each of the above-mentioned domains, it may be operably linked with a gene encoding the Fc ⁇ R-binding domain described in the above-mentioned section “Fc ⁇ R-binding domain”.
  • a polynucleotide encoding an antibody Fc region may be used appropriately as the above-mentioned “FcRn-binding domain having FcRn-binding activity under an acidic pH range condition and Fc ⁇ receptor-binding domain having selective binding activity to an Fc ⁇ receptor”.
  • Fc regions whose “FcRn-binding activity under an acidic pH range condition” and “selective binding activity to an Fc ⁇ receptor” are appropriately modified through modification of the polynucleotides may also be used.
  • a polynucleotide encoding the antigen-binding molecule is inserted in a manner operably linked to a regulatory sequence into an expression vector. Regulatory sequences include, for example, enhancers and promoters.
  • an appropriate signal sequence may be linked to the amino terminus so that the expressed antigen-binding molecule is secreted to the outside of the cells.
  • signal sequence for example, a peptide having the amino acid sequence MGWSCIILFLVATATGVHS (SEQ ID NO: 4) is used; however, it is also possible to link other appropriate signal sequences.
  • the expressed polypeptide is cleaved at the carboxyl terminus of the above-described sequence, and the cleaved polypeptide is secreted as a mature polypeptide to the outside of cells. Then, appropriate host cells are transformed with this expression vector so that recombinant cells expressing the polynucleotide encoding the antigen-binding molecule of interest can be obtained.
  • the antigen-binding molecules of the present invention can be produced from the recombinant cells by following the methods described above in the section on antibodies.
  • operably linked means that the nucleic acid has a functional relationship with another nucleic acid sequence.
  • a DNA encoding a presequence or a secretory leader is operably linked to a DNA encoding a certain polypeptide if it is to be expressed as a precursor protein involved in the secretion of the polypeptide.
  • a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the coding sequence.
  • a ribosome binding site is operably linked to a coding sequence if it is in a position that facilitates translation.
  • “operably linked” means that the linked DNA sequences are contiguous, and in the case of a secretory leader, it means that the linked DNA sequences are contiguous and in a reading frame. However, enhancers do not have to be contiguous. Linking is accomplished by ligation at suitable restriction sites. If such sites do not exist, synthetic oligonucleotide adaptors or linkers are used in accordance with conventional practice. Furthermore, linked nucleic acids may be produced by the above-mentioned overlap extension PCR technique.
  • a variant of the polynucleotide is inserted into an appropriate expression vector.
  • Such variants preferably include those prepared via humanization based on the polynucleotide sequence encoding an antigen-binding molecule of the present invention obtained by screening as a randomized variable region library a synthetic library or an immune library constructed originating from nonhuman animals. The same methods as described above for producing above-described humanized antibodies can be used as a method for producing humanized antigen-binding molecule variants.
  • such variants preferably include those obtained by introducing an alteration that increases the antigen affinity (affinity maturation) of an antigen-binding molecule of the present invention into an isolated polynucleotide sequence for the molecule obtained by screening using a synthetic library or a naive library as a randomized variable region library.
  • affinity maturation an alteration that increases the antigen affinity (affinity maturation) of an antigen-binding molecule of the present invention into an isolated polynucleotide sequence for the molecule obtained by screening using a synthetic library or a naive library as a randomized variable region library.
  • affinity maturation including CDR mutagenesis (Yang et al. (J. Mol. Biol. (1995) 254, 392-403)), chain shuffling (Marks et al. (Bio/Technology (1992) 10, 779-783)), use of E. coli mutant strains (Low et al. (J. Mol. Biol.
  • polynucleotides encoding antigen-binding molecules which have a heavy chain where a polynucleotide encoding an Fc region modified to have an amino acid mutation as described above is linked in frame to a polynucleotide encoding the above-described antigen-binding domain whose binding activity varies depending on a selected condition.
  • the present invention provides methods for producing antigen-binding molecules, comprising collecting the antigen-binding molecules from culture media of cells introduced with vectors in which a polynucleotide encoding an Fc region is operably linked in frame to a polynucleotide encoding an antigen-binding domain whose binding activity varies depending on ion concentration condition.
  • the present invention also provides methods for producing antigen-binding molecules, comprising collecting the antigen-binding molecules from culture media of cells introduced with vectors constructed by operably linking a polynucleotide encoding an antigen-binding domain whose binding activity varies depending on ion concentration condition to a polynucleotide encoding an Fc region which is in advance operably linked to a vector.
  • antigen-binding molecules of the present invention are administered to each group of non-human animals such as mice at an appropriate age in month.
  • antigen-binding molecule may be systemically or locally administered by intravenous injection, intramuscular injection, intraperitoneal injection, subcutaneous injection, intracranial injection, or such, as compositions in the dosage form for injections, transnasal administration, transpulmonary administration, or transdermal administration.
  • Spectroscopic methods such as nuclear magnetic resonance (NMR) or mass spectrometry (MS) analyses including SELDI(-TOF), MALDI(-TOF), 1D gel-based analysis, 2D gel-based analysis, liquid chromatography (for example, high-pressure liquid chromatography (HPLC) or low-pressure liquid chromatography (LPLC)), thin layer chromatography, and LC-MS-based techniques may be used to measure the concentrations.
  • suitable LCMS techniques include ICAT (registered trademark) (Applied Biosystems) and iTRAQ (registered trademark) (Applied Biosystems).
  • a method for detecting antigen fragments that have been produced by further digestion of a targeted antigen by an appropriate enzyme may also be employed when appropriate.
  • the antigen concentration may be measured by a direct or indirect detection method. More specifically, the antigen may be detected directly or indirectly via interaction with a ligand or ligands such as enzymes, binding, receptors or transport proteins, antibodies, peptides, aptamers or oligonucleotides, or any synthetic chemical receptors or compounds that can bind specifically to the antigen.
  • the ligand can be modified with a detectable label such as a luminescent label, fluorescent label, or radioactive label, and/or an affinity tag.
  • An immunological method may be given as such an example.
  • a preferred measurement method may be, for example, an immunological method that uses an antibody that binds to an epitope present in the antigen.
  • an immunological method include enzyme immunoassay (ELISA, EIA), fluoroimmunoassay (FIA), radioimmunoassay (RIA), luminescence immunoassay (LIA), enzyme antibody technique, fluorescent antibody technique, immunochromatography method, immunoturbidimetry, latex turbidimetry, and latex agglutination measurement method.
  • ELISA, EIA enzyme immunoassay
  • FIA fluoroimmunoassay
  • RIA radioimmunoassay
  • LIA luminescence immunoassay
  • enzyme antibody technique fluorescent antibody technique
  • immunochromatography method immunoturbidimetry
  • latex turbidimetry latex turbidimetry
  • latex agglutination measurement method enzyme immunoassay
  • measurements in these immunological methods may be carried out manually by hand or using a device such as
  • a first antibody immobilized onto a carrier is allowed to react simultaneously or sequentially with a biological sample and a second antibody modified by a labeling substance.
  • the above-mentioned reaction leads to formation of a complex comprising the first antibody immobilized onto a carrier, the antigen, and a second antibody modified by a labeling substance, and quantification of the labeling substance linked to the second antibody included in this complex enables measurement of the amount (concentration) of the antigen included in the biological sample.
  • a microplate onto which a first antibody is immobilized, serially diluted biological samples, a secondary antibody modified by an enzyme such as HRP, washing buffer, and a solution containing a substrate to which an enzyme such as HRP reacts are preferably used.
  • a substrate is allowed to react under an optimal condition with the enzyme which modifies the secondary antibody, and the amount of the enzyme reaction product can be determined by an optical method.
  • an optical waveguide onto which a first antibody is immobilized, serially diluted biological samples, a secondary antibody modified by a fluorescent substance, and washing buffer are preferably used.
  • the intensity of the fluorescence emitted by the fluorescent substance through irradiation of excitation light onto the fluorescent substance modifying the secondary antibody may be measured.
  • radioimmunoassay the amount of radiation emitted by the radioactive substance is measured.
  • luminescence immunoassay the amount of luminescence emitted by the luminescent reaction system is measured.
  • immunoturbidimetry latex turbidimetry, latex agglutination measurement method, and such, transmitted light or scattered light is measured by the end-point method or the rate method.
  • an instrument such as an analyzer may be used when appropriate.
  • the present invention relates to pharmaceutical compositions comprising antigen-binding molecules of the present invention, antigen-binding molecules produced by alteration methods of the present invention, or antigen-binding molecules produced by production methods of the present invention.
  • Antigen-binding molecules of the present invention or antigen-binding molecules produced by production methods of the present invention are useful as pharmaceutical compositions since they, when administered, have the strong effect to reduce the plasma antigen concentration as compared to typical antigen-binding molecules, and exhibit the improved in vivo immune response, pharmacokinetics, and others in animals administered with the molecules.
  • the pharmaceutical compositions of the present invention may comprise pharmaceutically acceptable carriers.
  • compositions generally refer to agents for treating or preventing, or testing/diagnosing diseases.
  • compositions of the present invention can be formulated by methods known to those skilled in the art. For example, they can be used parenterally, in the form of injections of sterile solutions or suspensions including water or other pharmaceutically acceptable liquid.
  • such compositions can be formulated by mixing in the form of unit dose required in the generally approved medicine manufacturing practice, by appropriately combining with pharmacologically acceptable carriers or media, specifically with sterile water, physiological saline, vegetable oil, emulsifier, suspension, surfactant, stabilizer, flavoring agent, excipient, vehicle, preservative, binder, or such.
  • the amount of active ingredient is adjusted to obtain an appropriate amount in a pre-determined range.
  • Sterile compositions for injection can be formulated using vehicles such as distilled water for injection, according to standard formulation practice.
  • Aqueous solutions for injection include, for example, physiological saline and isotonic solutions containing dextrose or other adjuvants (for example, D-sorbitol, D-mannose, D-mannitol, and sodium chloride).
  • dextrose or other adjuvants for example, D-sorbitol, D-mannose, D-mannitol, and sodium chloride.
  • solubilizers for example, alcohols (ethanol and such), polyalcohols (propylene glycol, polyethylene glycol, and such), non-ionic surfactants (polysorbate 80TM, HCO-50, and such).
  • Oils include sesame oil and soybean oils.
  • Benzyl benzoate and/or benzyl alcohol can be used in combination as solubilizers. It is also possible to combine buffers (for example, phosphate buffer and sodium acetate buffer), soothing agents (for example, procaine hydrochloride), stabilizers (for example, benzyl alcohol and phenol), and/or antioxidants. Appropriate ampules are filled with the prepared injections.
  • compositions of the present invention are preferably administered parenterally.
  • the compositions in the dosage form for injections, transnasal administration, transpulmonary administration, or transdermal administration are administered.
  • they can be administered systemically or locally by intravenous injection, intramuscular injection, intraperitoneal injection, subcutaneous injection, or such.
  • Administration methods can be appropriately selected in consideration of the patient's age and symptoms.
  • the dose of a pharmaceutical composition containing an antigen-binding molecule can be, for example, from 0.0001 mg to 1000 mg/kg for each administration. Alternatively, the dose can be, for example, from 0.001 to 100000 mg per patient.
  • the present invention is not limited by the numeric values described above.
  • the doses and administration methods vary depending on the patient's weight, age, symptoms, and such. Those skilled in the art can set appropriate doses and administration methods in consideration of the factors described above.
  • kits for use in the methods of the present invention which comprise at least an antigen-binding molecule of the present invention.
  • pharmaceutically acceptable carriers, media, instruction manuals describing the using method, and such may be packaged into the kits.
  • the present invention relates to pharmaceutical agents for eliminating, from the plasma, complexes containing two or more antigenic binding units and two or more antigen-binding molecules present in the plasma, which contain as an active ingredient the antigen-binding molecules of the present invention or the antigen-binding molecules produced by the production methods of the present invention.
  • the present invention relates to methods for treating a disease, which includes administering to subjects (patients, human subjects, etc.) the antigen-binding molecules of the present invention or the antigen-binding molecules produced by the production methods of the present invention.
  • a disease includes cancer and inflammatory diseases.
  • the present invention also relates to use of the antigen-binding molecules of the present invention or the antigen-binding molecules produced by the production methods of the present invention in the manufacture of a pharmaceutical agent for eliminating from the plasma complexes containing two or more antigenic binding units and two or more antigen-binding molecules present in the plasma.
  • the present invention further relates to use of the antigen-binding molecules of the present invention or the antigen-binding molecules produced by the production methods of the present invention for eliminating, from the plasma, complexes containing two or more antigenic binding units and two or more antigen-binding molecules present in the plasma.
  • the present invention relates to antigen-binding molecules of the present invention and antigen-binding molecules produced by the production methods of present invention for use in the methods of the present invention.
  • Amino acids contained in the amino acid sequences of the present invention may be post-translationally modified (for example, the modification of an N-terminal glutamine into a pyroglutamic acid by pyroglutamylation is well-known to those skilled in the art). Naturally, such post-translationally modified amino acids are included in the amino acid sequences in the present invention.
  • H54/L28-IgG1 which comprises H54-IgG1 (SEQ ID NO: 36) and L28-CK (SEQ ID NO: 37) described in WO2009/125825 is a humanized anti-IL-6 receptor antibody.
  • Fv4-IgG1 which comprises VH3-IgG1 (SEQ ID NO: 38) and VL3-CK (SEQ ID NO: 39) is a humanized anti-IL-6 receptor antibody resulting from conferring, to H54/L28-IgG1, the property of binding to soluble human IL-6 receptor in a pH-dependent manner (which binds at pH 7.4 and dissociates at pH 5.8).
  • the in vivo mouse test described in WO2009/125825 demonstrated that, in the group administered with a mixture of Fv4-IgG1 and soluble human IL-6 receptor as the antigen, the elimination of soluble human IL-6 receptor from plasma was significantly accelerated as compared to the group administered with a mixture of H54/L28-IgG1 and soluble human IL-6 receptor as the antigen.
  • the soluble human IL-6 receptor bound to H54/L28-IgG1, which is an antibody that binds to a soluble human IL-6 receptor, is, together with the antibody, recycled to plasma by FcRn.
  • Fv4-IgG1 which is an antibody that binds to a soluble human IL-6 receptor in a pH dependent manner, dissociates soluble human IL-6 receptor under the acidic condition in the endosome.
  • the dissociated soluble human IL-6 receptor is degraded in the lysosomes, thus this enables considerable acceleration of the elimination of soluble human IL-6 receptor.
  • Fv4-IgG1 which is an antibody that binds to a soluble human IL-6 receptor in a pH dependent manner
  • FcRn an antibody that binds to a soluble human IL-6 receptor in a pH dependent manner
  • the recycled antibody can bind to soluble human IL-6 receptor again, the antibody repeatedly binds to the antigen (soluble human IL-6 receptor) and is recycled by FcRn to the plasma. It is thought that, as a result, a single antibody molecule can bind repeatedly several times to soluble human IL-6 receptor ( FIG. 1 ).
  • VH3-IgG1-F1022 (SEQ ID NO: 40), an antigen-binding molecule with enhanced mouse Fc ⁇ R binding, was prepared by substituting Asp for Lys at position 326 (EU numbering) and Tyr for Leu at position 328 (EU numbering) in VH3-IgG1.
  • Fv4-IgG1-F1022 containing VH3-IgG1-F1022 as the heavy chain and VL3-CK as the light chain was produced using the method described in Reference Example 1.
  • VH3-IgG1-F760 (SEQ ID NO: 41), an antigen-binding molecule without mouse Fc ⁇ R binding, was prepared by substituting Arg for Leu at position 235 and Lys for Ser at position 239 (EU numbering) in VH3-IgG1.
  • VH3/L(WT)-IgG1, VH3/L(WT)-IgG1-F1022, and VH3/L(WT)-IgG1-F760 which contain VH3-IgG1, VH3-IgG1-F1022, and VH3-IgG1-F760 as the heavy chain, and L(WT)-CK (SEQ ID NO: 42) as the light chain, were produced using the method described in Reference Example 1. These antibodies were kinetically analyzed for their mouse Fc ⁇ R binding as described below.
  • mouse Fc ⁇ Rs The binding of antibodies to mouse Fc ⁇ RI, Fc ⁇ RIIb, Fc ⁇ RIII, and Fc ⁇ RIV (hereinafter, referred to as mouse Fc ⁇ Rs) (R & D systems, SinoBiological, or prepared by the method described in Reference Example 2) was kinetically analyzed using Biacore T100 and T200 (GE Healthcare). An appropriate amount of protein L (ACTIGEN or BioVision) was immobilized onto a Sensor chip CM4 (GE Healthcare) by an amino coupling method, and antibodies of interest were captured thereto. Then, diluted solutions of mouse Fc ⁇ Rs and a running buffer as a blank were injected, and the mouse Fc ⁇ Rs were allowed to interact with antibodies captured onto the sensor chip.
  • the running buffer used was 20 mmol/l ACES, 150 mmol/l NaCl, 0.05% (w/v) Tween20, pH 7.4. This buffer was also used to dilute the mouse Fc ⁇ Rs.
  • the sensor chip was regenerated using 10 mmol/1 glycine-HCl, pH 1.5. All measurements were carried out at 25° C.
  • the binding rate constant ka (l/Ms) and dissociation rate constant kd (l/s), which are kinetic parameters, were calculated from the sensorgrams obtained by the measurement.
  • KD (M) of each antibody for human Fc ⁇ R was calculated based on the values. Each parameter was calculated using Biacore T100 or T200 Evaluation Software (GE Healthcare).
  • VH3/L (WT)-IgG1-F1022 was demonstrated to have increased binding activity to mFc ⁇ RI, mFc ⁇ RII, and mFc ⁇ RIII as compared to VH3/L (WT)-IgG1.
  • VH3/L (WT)-IgG1-F760 the binding to the various mouse Fc ⁇ Rs was undetectable, demonstrating that VH3/L (WT)-IgG1-F760 lacks the binding activity to the various mouse Fc ⁇ Rs.
  • VH3/L (WT)-IgG1, VH3/L (WT)-IgG1-F1022, and VH3/L (WT)-IgG1-F760 are shown as IgG1, F1022, and F760, respectively.
  • Fv4-IgG1 with low fucose content (hereinafter, abbreviated as Fv4-IgG1-Fuc) was produced by expressing Fv4-IgG1 using fucose transporter gene-deficient CHO cells (WO 2006/067913) as host cells according to the method described in Reference Example 1. It has been reported that, of the mFc ⁇ Rs (mouse Fc ⁇ receptors), antibodies with low fucose content have selectively increased Fc ⁇ RIV-binding activity (Science, 2005, 310 (5753) 1510-1512).
  • H54/L28-IgG1 which is an anti-human IL-6 receptor antibody
  • Fv4-IgG1 having the property of binding to human IL-6 receptor in a pH-dependent manner were produced by the method described in Reference Example 1.
  • In vivo infusion tests were carried out using the produced H54/L28-IgG1 and Fv4-IgG1 by the method described below.
  • an anti-mouse CD4 monoclonal antibody (prepared by a known method) was administered once at 20 mg/kg into the caudal vein. Then, an infusion pump containing 92.8 ⁇ g/ml soluble human IL-6 receptor was subcutaneously implanted on the back of the mice. Three days after implantation of the infusion pump, an anti-human IL-6 receptor antibody was administered once at 1 mg/kg into the caudal vein. The blood was collected from the mice 15 minutes, seven hours, one day, two days, four days, and seven days after administration of the anti-human IL-6 receptor antibody. Immediately, the collected blood was centrifuged at 15,000 rpm and 4° C. for 15 minutes to prepare plasma. The isolated plasma was stored in a freezer set at ⁇ 20° C. or below until use.
  • hsIL-6R soluble human IL-6 receptor concentrations in mouse plasma were determined by an electrochemiluminescent method.
  • hsIL-6R soluble human IL-6 receptor standard curve samples prepared at 2000, 1000, 500, 250, 125, 62.5, and 31.25 pg/ml and assay samples of mouse plasma diluted 50 times or more were mixed with Monoclonal Anti-human IL-6R Antibody (R&D), Biotinylated Anti-human IL-6 R Antibody (R&D), Tocilizumab, which had been ruthenated with SULFO-TAG NHS Ester (Meso Scale Discovery). The mixtures were incubated at 37° C. overnight.
  • Tocilizumab was prepared at a final concentration of 333 ⁇ g/ml. Then, the reaction mixtures were aliquoted in an MA400 PR Streptavidin Plate (Meso Scale Discovery). The solution reacted at room temperature for one hour was washed out, and then Read Buffer T ( ⁇ 4) (Meso Scale Discovery) was aliquoted Immediately thereafter, the measurement was carried out using SECTOR PR 400 Reader (Meso Scale Discovery). The concentration of hsIL-6R soluble human IL-6 receptor was determined based on the response of the standard curve using analysis software SOFTmax PRO (Molecular Devices).
  • FIG. 2 A time course of the monitored human IL-6 receptor concentration is shown in FIG. 2 .
  • Fv4-IgG1 that binds to human IL-6 receptor in a pH-dependent manner could reduce the human IL-6 receptor concentration, but could not reduce it below the baseline without antibody administration. That is, the administered antibody which binds to an antigen in a pH-dependent manner could not reduce the antigen concentration in plasma below the level prior to antibody administration.
  • Fv4-IgG1 which is a pH-dependent human IL-6 receptor-binding antibody
  • a animal model in which the soluble human IL-6 receptor concentration is maintained constant in plasma was created by implanting an infusion pump (MINI-OSMOTIC PUMP MODEL2004, alzet) containing soluble human IL-6 receptor under the skin on the back of human FcRn transgenic mice (B6.mFcRn ⁇ / ⁇ .hFcRn Tg line 32+/+ mouse, Jackson Laboratories, Methods Mol Biol. (2010) 602, 93-104).
  • an anti-human IL-6 receptor antibody was administered simultaneously with Sanglopor (CSL Behring) which is a human immunoglobulin preparation, to assess the in vivo dynamics of the soluble human IL-6 receptor after antibody administration.
  • an anti-mouse CD4 monoclonal antibody (prepared by a known method) was administered once at 20 mg/kg into the caudal vein. Then, an infusion pump containing 92.8 ⁇ g/ml soluble human IL-6 receptor was subcutaneously implanted on the back of the mice. Three days after implantation of the infusion pump, an anti-human IL-6 receptor antibody and Sanglopor were administered once at 1 mg/kg and 1000 mg/kg, respectively, into the caudal vein. The blood was collected from the mice 15 minutes, seven hours, one day, two days, four days, seven days, 14 days, and 21 days after administration of the anti-human IL-6 receptor antibody.
  • the blood was collected from the mice 15 minutes, seven hours, one day, two days, three days, seven days, 14 days, and 21 days after administration of the anti-human IL-6 receptor antibody. Immediately, the collected blood was centrifuged at 15,000 rpm and 4° C. for 15 minutes to prepare the plasma. The isolated plasma was stored in a freezer set at ⁇ 20° C. or below until use.
  • the hsIL-6R soluble human IL-6 receptor concentrations in mouse plasma were determined by the same electrochemiluminescent method as described in (2-1-2).
  • the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG1-F1022 with enhanced mouse Fc ⁇ R binding was considerably reduced as compared to the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG1.
  • the concentration was confirmed to be decreased below the baseline human IL-6 receptor concentration without antibody administration.
  • the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG1-F1022 was reduced down to about 1/100 three days after administration as compared to the case of Fv4-IgG1 administration.
  • mice administered with Fv4-IgG1 the human IL-6 receptor concentration in plasma was reduced in mice administered with Fv4-IgG1-Fuc which has sugar chains with low fucose content and with increased mouse Fc ⁇ R IV-binding activity.
  • the human IL-6 receptor concentration in the plasma of mice administered with Fv4-IgG1-Fuc was reduced down to about 1 ⁇ 2 seven days after administration as compared to the case of Fv4-IgG1 administration.
  • the above finding demonstrates that, by administering to mice a pH-dependent antigen-binding molecule that binds to human IL-6 receptor in a pH-dependent manner and whose Fc ⁇ R binding has been enhanced, the soluble antigen concentration in the plasma of the mice can be reduced.
  • methods for enhancing the Fc ⁇ R binding are not particularly limited to introduction of amino acid alterations. It was demonstrated that such enhancement can be achieved, for example, by using a human IgG Fc region to which a sugar chain with low fucose content is linked at position 297 (EU numbering); however, the effect of Fv4-IgG1-Fuc to reduce antigen concentration was smaller than Fv4-F1022.
  • IgG antibodies that are non-specifically incorporated into cells return to the cell surface by binding to FcRn under the acidic condition in the endosome, and then dissociate from FcRn under the neutral condition in plasma.
  • an antibody that neutralizes the function of a soluble antigen by binding to the antigen is administered to mice in which the concentration of the soluble antigen is maintained constant in plasma, the soluble antigen in plasma forms a complex with the antibody administered.
  • the soluble antigen incorporated into cells while remaining as the complex is thought to be recycled, in a state bound to the antibody, to the plasma together with the antibody, because the Fc region of the antibody binds to FcRn under the acidic condition in the endosome.
  • the antibody against the soluble antigen is an antibody that binds to the antigen in a pH-dependent manner (i.e., an antibody that dissociates the soluble antigen under the acidic condition in the endosome)
  • the soluble antigen that is non-specifically incorporated into cells while remaining as a complex with the antibody is dissociated from the antibody in the endosome and degraded in the lysosome in the cell; thus, the soluble antigen is not recycled to the plasma. That is, it is thought that Fv4-IgG1 incorporated as a complex with the soluble antigen into cells can dissociate the soluble antigen in the endosome and thus accelerate the elimination of the soluble antigen.
  • antigen-binding molecules such as Fv4-IgG1, which contain an antigen-binding domain whose antigen-binding activity is altered depending on the ion concentration, are thought to be capable of binding to antigens repeatedly several times.
  • the effect to accelerate the elimination of soluble antigens from the plasma by dissociating them in the endosome is thought to depend on the rate of incorporation of the antigen/antigen-binding molecule complex into the endosome.
  • An antigen-binding molecule that contains an antigen-binding domain whose binding activity to various Fc ⁇ Rs has been increased and whose antigen-binding activity is altered depending on the condition of ion concentration, is actively incorporated into cells by binding to various Fc ⁇ Rs expressed on the cell membrane, and can be shuttled back to plasma by recycling via the binding between FcRn and the FcRn-binding domain comprised in the molecule, which has FcRn-binding activity under an acidic pH range condition.
  • the Fc ⁇ R-binding activity of an antibody that binds to a membrane antigen plays an important role in the cytotoxic activity of the antibody.
  • a human IgG1 isotype with strong Fc ⁇ R-binding activity is used.
  • techniques to enhance the cytotoxic activity of such antibodies by increasing the Fc ⁇ R-binding activity of the antibodies are used commonly in the art.
  • the present inventors revealed for the first time the benefit of the enhancement of Fc ⁇ R binding by combining an FcRn-binding domain that has FcRn-binding activity under an acidic pH range condition with an antigen-binding domain whose soluble antigen binding is altered depending on the ion concentration condition, comprised in an antigen-binding molecule targeted to a soluble antigen.
  • a reported method for improving the retention of IgG antibody in plasma is to improve the FcRn binding under an acidic pH range condition. It is thought that, when the FcRn binding under an acidic pH range condition is improved by introducing an amino acid substitution into the Fc region of an IgG antibody, this increases the recycling efficiency from the endosome to plasma, resulting in an improvement of the plasma retention of the IgG antibody.
  • VH3-IgG1-F1093 (SEQ ID NO: 43) with a substitution of Leu for Met at position 428 and Ser for Asn at position 434 (EU numbering) in VH3-IgG1-F1022 was prepared to improve the pharmacodynamics of Fv4-IgG1-F1022 that was demonstrated to produce, when administered, the effect of significantly reducing the soluble antigen concentration in plasma, as described in Example 2.
  • Fv4-IgG1-F1093 comprising VH3-IgG1-F1093 as the heavy chain and VL3-CK as the light chain was constructed using the method described in Reference Example 1.
  • Anti-human IL-6 receptor antibody concentrations in mouse plasma were determined by the ELISA method.
  • an anti-Human IgG ( ⁇ -chain specific) F(ab′)2 Fragment of Antibody (SIGMA) was aliquoted in a Nunc-Immuno Plate, MaxiSoup (Nalge nunc International). The plate was allowed to stand at 4° C. overnight to prepare a plate immobilized with the anti-human IgG. Standard curve samples containing an anti-human IL-6 receptor antibody (concentration in plasma: 0.8, 0.4, 0.2, 0.1, 0.05, 0.025, and 0.0125 ⁇ g/ml) and assay samples of mouse plasma diluted 100 times or more were prepared.
  • the chromogenic reaction of the reaction solution was performed using as a substrate TMB One Component HRP Microwell Substrate (BioFX Laboratories). After terminating the reaction with 1N sulfuric acid (Showa Chemical), the absorbance at 450 nm of the reaction solution of each well was measured with a microplate reader. Antibody concentrations in mouse plasma were determined based on the absorbance of the standard curve using the analysis software SOFTmax PRO (Molecular Devices).
  • the time course of the soluble human IL-6 receptor concentration in the plasma of the Fv4-IgG1-F1022-administered group was equivalent to that of the Fv4-IgG1-F1093-administered group, up to three days after antibody administration.
  • the soluble human IL-6 receptor concentration in plasma was reduced as much as about 100 times in both of the Fv4-IgG1-F1022 and Fv4-IgG1-F1093-administered groups.
  • the soluble human IL-6 receptor concentration in plasma was observed to be elevated in the Fv4-IgG1-F1022-administered group as compared to on day three after administration.
  • an increase in the plasma concentration of soluble human IL-6 receptor was not observed, showing that the effect to reduce the soluble human IL-6 receptor concentration was sustained in this administration group.
  • Fv4-IgG1-F1093 when administered, reduced the soluble human IL-6 receptor concentration in the plasma of the administered individual down to about 1/100 as compared to Fv4-IgG1, and in addition, it sustained this condition for a long period.
  • Fv4-IgG1-F1093 was demonstrated to be a highly excellent antigen-binding molecule.
  • the phenomenon observed herein can be explained as follows. Fv4-IgG1-F1022 in which the Fc ⁇ R-binding activity of Fv4-IgG1 has been increased under a neutral pH range condition is thought to be incorporated in a large amount mainly into cells expressing Fc ⁇ R on the cell membrane.
  • the incorporated antibody is transferred into the endosome, and by binding to FcRn in the endosome, the antibody is recycled to the plasma.
  • the FcRn-binding activity of the antibody is not high enough under the condition at acidic pH in the endosome, the antibody incorporated into the endosome is thought to be incapable of sufficient recycling.
  • a possible reason for the reduced plasma retention of Fv4-IgG1-F1022 relative to Fv4-IgG1 would be that the FcRn-binding activity under an acidic pH range condition is insufficient for sufficient recycling of the endosome-incorporated antibody to the plasma by FcRn binding, and the antibody that was not recycled was degraded in the lysosome.
  • Fv4-IgG1-F1022 Fv4-IgG1-F1093 resulting from the enhancement of the human FcRn-binding activity of Fv4-IgG1-F1022 under an acidic pH range condition is thought to be incorporated in a large amount mainly into cells expressing Fc ⁇ R on the cell membrane. An antibody incorporated and transferred into the endosome is recycled to the plasma by binding to FcRn in the endosome. Since its human FcRn-binding activity under an acidic pH range condition is enhanced, Fv4-IgG1-F1093 is thought to have sufficient FcRn-binding activity in the endosome.
  • the phenomenon observed herein can be explained as follows.
  • an antibody without pH-dependent antigen binding is non-specifically incorporated into cells.
  • Antigens that remain to be bound to the antibody are recycled to the plasma in the same extent as the antibody.
  • the extent of recycling to the plasma in a living organism administered with the antibody is higher than that of an antibody without increased FcRn-binding activity, and this results in an increased extent of recycling of antigens bound to the antigen to the plasma in the living organism.
  • the plasma concentration of the antigen to which the antibody binds is thought to be also increased in the living organism.
  • an antibody that binds to an antigen in a pH-dependent manner and which has increased Fc ⁇ R-binding activity is mainly incorporated into cells expressing Fc ⁇ R on the cell membrane, and this reduces the plasma retention. Furthermore, after being incorporated into the cells while bound to the antibody, the antigen is dissociated from the antibody in the endosome and then degraded in the lysosome, resulting in a decrease of the antigen concentration in plasma in the living organism.
  • the FcRn-binding activity is increased under an acidic pH range condition, the antibody retention in plasma, even if worsened due to increased Fc ⁇ R-binding activity, is improved by an increase in the rate of recycling by FcRn.
  • the antigen bound to the antibody that binds to the antigen in a pH-dependent manner is dissociated from the antibody in the endosome and directly degraded in the lysosome, it is not thought that the antigen concentration is increased in the plasma. Furthermore, the improved plasma retention of the antibody administered to the living organism is thought to allow the antigen elimination effect of the antibody to be sustained, and the antigen concentration to be maintained low for a longer period.
  • the antigen concentration in plasma was significantly reduced in the group administered with Fv4-IgG1-F1022 with enhanced mouse Fc ⁇ R binding.
  • the reduced plasma retention observed in the Fv4-IgG1-F1022-administered group was markedly improved by increasing the human FcRn-binding activity of Fv4-IgG1-F1022 under an acidic pH range condition.
  • the effect of eliminating soluble antigens from plasma by enhancing mouse Fc ⁇ R binding and the effect of improving the plasma retention of an antibody by enhancing the human FcRn binding activity under an acidic pH range condition were further assessed as described below.
  • VH3-IgG1-F1087 (SEQ ID NO: 44) resulting from substituting Asp for Lys at position 326 (EU numbering) in VH3-IgG1, and VH3-IgG1-F1182 (SEQ ID NO: 45) resulting from substituting Asp for Ser at position 239 and Glu for Ile at position 332 (EU numbering) in VH3-IgG1, were prepared as antigen-binding molecules with enhanced mouse Fc ⁇ R binding.
  • Fv4-IgG1-F1087 that contains VH3-IgG1-F1087 as the heavy chain and VL3-CK as the light chain
  • Fv4-IgG1-F1182 that contains VH3-IgG1-F1182 as the heavy chain and VL3-CK as the light chain
  • VH3/L (WT)-IgG1-F1087 and VH3/L (WT)-IgG1-F1182 which contain VH3-IgG1-F1087 and VH3-IgG1-F1182 as the heavy chain, respectively, and L (WT)-CK (SEQ ID NO: 42) as the light chain, were prepared by the method described in Reference Example 1.
  • These antibodies, and VH3/L (WT)-IgG1-F1022 and VH3/L (WT)-IgG1 were assessed for their mouse Fc ⁇ R-binding activity by the method described in Reference Example 2. The result is shown in Table 7.
  • VH3/L (WT)-IgG1, VH3/L (WT)-IgG1-F1022, VH3/L (WT)-IgG1-F1087, and VH3/L (WT)-IgG1-F1182 are shown as IgG1, F1022, F1087, and F1182, respectively.
  • mice F1182 administration to reduce the plasma concentration of soluble human IL-6 receptor were small in the group administered with F1182 in vivo which has considerably increased binding activity to mouse Fc ⁇ RI and mouse Fc ⁇ RIV (as well as several-fold enhanced binding to mouse Fc ⁇ RII and mouse Fc ⁇ RIII). It was thought from these results that the mouse Fc ⁇ Rs that more significantly contribute by an effect that efficiently decreases the antigen concentration in the plasma of mice administered with a pH-dependent antigen-binding antibody, are mouse Fc ⁇ RII and/or mouse Fc ⁇ RIII. Specifically, it is thought that the plasma antigen concentration can be more efficiently reduced in vivo by administering into a living organism a pH-dependent antigen-binding antibody with enhanced binding to mouse Fc ⁇ RII and/or mouse Fc ⁇ RIII.
  • Example 3 when compared to human FcRn transgenic mice administered with Fv4-IgG1-F1022, the plasma retention of an antibody is markedly improved in human FcRn transgenic mice administered with Fv4-IgG1-F1093 resulting from increasing the human FcRn-binding activity under an acidic pH range condition of Fv4-IgG1-F1022 in which the mouse Fc ⁇ R-binding activity has been increased.
  • VH3-IgG1-F1180 (SEQ ID NO: 46) and VH3-IgG1-F1181 (SEQ ID NO: 47) were prepared by substituting Leu for Met at position 428 and Ser for Asn at position 434 (EU numbering) in the heavy chains VH3-IgG1-F1087 and VH3-IgG1-F1182, in order to increase their human FcRn-binding activity of Fv4-IgG1-F1087 and Fv4-IgG1-F1182 under an acidic pH range condition.
  • VH3-IgG1-F1412 (SEQ ID NO: 48) was prepared by substituting Ala for Asn at position 434 (EU numbering) in the heavy chain VH3-IgG1-F1087, in order to increase the human FcRn-binding activity of Fv4-IgG1-F1087 under an acidic pH range condition.
  • the results on the soluble IL-6 receptor concentrations in the plasma of the mouse groups administered with Fv4-IgG1-F1182, Fv4-IgG1-F1181, and Fv4-IgG1 are shown in FIG. 10 .
  • the plasma antibody concentrations in the mouse groups were measured by the method described in Example 3.
  • the plasma retention of antibodies was improved in both groups of mice administered with Fv4-IgG1-F1180 and Fv4-IgG1-F1412 resulting from increasing the human FcRn-binding activity of Fv4-IgG1-F1087 in an acidic pH range, and surprisingly, the plasma retention was improved up to a level comparable to that of the mouse groups administered with Fv4-IgG1. Furthermore, the sustainability of the effect of reducing the soluble IL-6 receptor concentration in plasma was improved by the improvement of the plasma antibody retention in the groups of administered mice.
  • the soluble IL-6 receptor concentrations in plasma 14 days and 21 days after administration of Fv4-IgG1-F1180 and Fv4-IgG1-F1412 were significantly reduced as compared to the concentrations 14 days and 21 days after administration of Fv4-IgG1-F1087.
  • alteration for enhancing human FcRn-binding activity under an acidic pH range condition could be accomplished by the method that substitutes Ala for Asn at position 434 (EU numbering), in addition to the method that substitutes Leu for Met at position 428 (EU numbering) and Ser for Asn at position 434 (EU numbering). Therefore, alterations used for enhancing human FcRn-binding activity under an acidic pH range condition are not particularly limited, and the method that substitutes Leu for Met at position 428 (EU numbering) and Ser for Asn at position 434 (EU numbering) in an IgG antibody (Nat. Biotechnol.
  • antigen-binding molecules that have increased human FcRn-binding activity under an acidic pH range condition but do not have the binding to the rheumatoid factor can be produced by introducing into the site of the Fc region an alteration that reduces the rheumatoid factor-binding activity alone without reducing the FcRn-binding activity under an acidic pH range condition.
  • Such alterations used for reducing the rheumatoid factor-binding activity include alterations at positions 248-257, 305-314, 342-352, 380-386, 388, 414-421, 423, 425-437, 439, and 441-444 (EU numbering), preferably those at positions 387, 422, 424, 426, 433, 436, 438, and 440 (EU numbering), and particularly preferably, an alteration that substitutes Glu or Ser for Val at position 422, an alteration that substitutes Arg for Ser at position 424, an alteration that substitutes Asp for His at position 433, an alteration that substitutes Thr for Tyr at position 436, an alteration that substitutes Arg or Lys for Gln at position 438, and an alteration that substitutes Glu or Asp for Ser at position 440 (EU numbering). These alterations may be used alone or in combination.
  • N-type glycosylation sequences include Asn-Xxx-Ser/Thr (Xxx represents an arbitrary amino acid other than Pro). This sequence can be introduced into the Fc region to add an N-type sugar chain, and the binding to RF can be inhibited by the steric hindrance of the N-type sugar chain.
  • Alterations used for adding an N-type sugar chain preferably include an alteration that substitutes Asn for Lys at position 248, an alteration that substitutes Asn for Ser at position 424, an alteration that substitutes Asn for Tyr at position 436 and Thr for Gln at position 438, and an alteration that substitutes of Asn for Qln at position 438, according to EU numbering, particularly preferably an alteration that substitutes Asn for Ser at position 424 (EU numbering).
  • VH3-mIgG1 For a mouse IgG1 antibody having the property of binding to human IL-6 receptor in a pH-dependent manner, the heavy chain VH3-mIgG1 (SEQ ID NO: 49) and the light chain VL3-mk1 (SEQ ID NO: 50) were constructed using the method described in Reference Example 1. Meanwhile, to increase the mouse Fc ⁇ R-binding activity of VH3-mIgG1, VH3-mIgG1-mF44 (SEQ ID NO: 51) was produced by substituting Asp for Ala at position 327 (EU numbering).
  • VH3-mIgG1-mF46 (SEQ ID NO: 52) was produced by substituting Asp for Ser at position 239 and Asp for Ala at position 327, according to EU numbering, in VH3-mIgG1.
  • Fv4-mIgG1, Fv4-mIgG1-mF44, and Fv4-mIgG1-mF46 which contain VH3-mIgG1, VH3-mIgG1-mF44, and VH3-mIgG1-mF46, respectively, as the heavy chain, and VL3-mk1 as the light chain, were prepared using the method described in Reference Example 1.
  • VH3/L (WT)-mIgG1, VH3/L (WT)-mIgG1-mF44, and VH3/L (WT)-mIgG1-mF46 which contain VH3-mIgG1, VH3-mIgG1-mF44, and VH3-mIgG1-mF46, respectively, as the heavy chain, and L (WT)-CK (SEQ ID NO: 42) as the light chain, were prepared by the method described in Reference Example 1. These antibodies were assessed for their mouse Fc ⁇ R-binding activity by the method described in Reference Example 2. The result is shown in Table 9.
  • VH3/L (WT)-mIgG1, VH3/L (WT)-mIgG1-mF44, and VH3/L (WT)-mIgG1-mF46 are shown as mIgG1, mF44, and mF46, respectively.
  • Example 4 The assessment result of Example 4 showing that VH3/L (WT)-mIgG1 having the Fc region of native mouse IgG1 antibody only binds to mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII but not to mouse Fc ⁇ RI and mouse Fc ⁇ RIV, suggests that mouse Fc ⁇ Rs important for the reduction of antigen concentration are mouse Fc ⁇ RII and/or mouse Fc ⁇ RIII.
  • VH3/L (WT)-mIgG-mF44 and VH3/L (WT)-mIgG1-mF46 introduced with an alteration that is thought to increase the Fc ⁇ R-binding activity of VH3/L (WT)-mIgG1 was demonstrated to have increased binding activity to both of mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII.
  • an infusion pump containing 92.8 ⁇ g/ml soluble human IL-6 receptor was subcutaneously implanted on the back of the mice.
  • the anti-human IL-6 receptor antibody was administered once at 1 mg/kg into the caudal vein.
  • the blood was collected from the mice 15 minutes, seven hours, one day, two days, four days, seven days, 14 days (or 15 days), and 21 days (or 22 days) after administration of the anti-human IL-6 receptor antibody.
  • the collected blood was centrifuged at 15,000 rpm and 4° C. for 15 minutes to prepare the plasma.
  • the isolated plasma was stored in a freezer set at ⁇ 20° C. or below until use.
  • the soluble human IL-6 receptor concentrations in plasma were determined by the method described in (2-1-2). The result is shown in FIG. 11 .
  • mice administered with mF44 and mF46 introduced with an alteration to increase the binding activity of mIgG1 (native mouse IgG1) to mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII the plasma IL-6 receptor concentration was markedly reduced as compared to mice administered with mIgG1.
  • the plasma IL-6 receptor concentration in the mF44-administered group was reduced by about 6 times as compared to the plasma IL-6 receptor concentration in the group without antibody administration, and about 10 times as compared to the mIgG1-administered group.
  • the plasma IL-6 receptor concentration in the mF46-administered group was markedly reduced by about 30 times as compared to the plasma IL-6 receptor concentration in the group without antibody administration, and about 50 times as compared to the mIgG1-administered group.
  • the effect can be assessed in the same manner regardless of whether the Fc region contained in an antibody originates from human or mouse IgG1.
  • the assessment can be achieved for an Fc region of any animal species, such as any of human IgG1, human IgG2, human IgG3, human IgG4, mouse IgG1, mouse IgG2a, mouse IgG2b, mouse IgG3, rat IgG, monkey IgG, and rabbit IgG, as long as the binding activity to the Fc ⁇ R of the animal species to be administered has been increased.
  • Fc ⁇ RIII-deficient mice (B6.129P2-FcgrR3tm1Sjv/J mouse, Jackson Laboratories) express mouse Fc ⁇ RI, mouse Fc ⁇ RIIb, and mouse Fc ⁇ RIV, but not mouse Fc ⁇ RIII. Meanwhile, Fc receptor ⁇ chain-deficient mice (Fcer1g mouse, Taconic, Cell (1994) 76, 519-529) express mouse Fc ⁇ RIIb alone, but not mouse Fc ⁇ RI, mouse Fc ⁇ RIII, and mouse Fc ⁇ RIV.
  • Example 5 it was demonstrated that mF44 and mF46 with increased Fc ⁇ R-binding activity of native mouse IgG1 show selectively enhanced binding to mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII. It was conceived that, using the selectively increased binding activity of the antibodies, the condition under which an antibody with selectively enhanced mouse Fc ⁇ RIIb binding is administered can be mimicked by administering mF44 and mF46 to mouse Fc ⁇ RIII-deficient mice or Fc receptor ⁇ chain-deficient mice which do not express mouse Fc ⁇ RIII.
  • the effect to eliminate soluble IL-6 receptor from plasma in Fc ⁇ RIII-deficient mice administered with the anti-human IL-6 receptor antibody Fv4-mIgG1, Fv4-mIgG1-mF44, or Fv4-mIgG1-mF46 was assessed by the same method described in Example 5.
  • the soluble human IL-6 receptor concentrations in the plasma of the mice were determined by the method described in Example (2-1-2). The result is shown in FIG. 12 .
  • the plasma IL-6 receptor concentrations in Fc ⁇ RIII-deficient mice administered with mF44 and mF46 which mimic the condition under which the mouse Fc ⁇ RIIb-binding activity of mIgG1 (native mouse IgG1) is selectively increased, were markedly reduced as compared to the plasma IL-6 receptor concentration in mice administered with mIgG1.
  • the plasma IL-6 receptor concentration of the mF44-administered group was reduced by about three times as compared to that of the mIgG1-administered group and the accumulation of antibody concentration due to antibody administration was suppressed.
  • the plasma IL-6 receptor concentration of the mF46-administered group was markedly reduced by about six times as compared to the plasma IL-6 receptor concentration of the group without antibody administration, and about 25 times as compared to the plasma IL-6 receptor concentration of the mIgG1-administered group.
  • This result shows that, as the mouse Fc ⁇ RIIb-binding activity of an anti-human IL-6 receptor antibody that binds to the antigen in a pH-dependent manner is greater, the IL-6 receptor concentration can be reduced more in the plasma of mice administered with the antibody.
  • the soluble human IL-6 receptor concentrations in the plasma of the mice were determined by the method described in Example (2-1-2). The result is shown in FIG. 13 .
  • the plasma IL-6 receptor concentration in Fc receptor ⁇ chain-deficient mice administered with mF44 and mF46 which mimic the condition resulting from the selective increase in the mouse Fc ⁇ RIIb-binding activity of mIgG1 (native mouse IgG1), was demonstrated to be markedly reduced as compared to the plasma IL-6 receptor concentration in Fc receptor ⁇ chain-deficient mice administered with mIgG1.
  • the plasma IL-6 receptor concentration in the mF44-administered group was reduced to about three times that in the mIgG1-administered group, and the accumulation of antigen concentration due to antibody administration was suppressed. Meanwhile, on day three after administration, the plasma IL-6 receptor concentration in the mF46-administered group was markedly reduced by about five times as compared to that in the group without antibody administration, and about 15 times as compared to that in the mIgG1-administered group.
  • Fc ⁇ RIIb-deficient mice (Fcgr2b (Fc ⁇ RII) mouse, Taconic) (Nature (1996) 379 (6563), 346-349) express mouse Fc ⁇ RI, mouse Fc ⁇ RIII, and mouse Fc ⁇ RIV, but not mouse Fc ⁇ RIIb.
  • Fcgr2b Fc ⁇ RII
  • Taconic Nature (1996) 379 (6563), 346-349
  • mouse Fc ⁇ RI, mouse Fc ⁇ RIII, and mouse Fc ⁇ RIV but not mouse Fc ⁇ RIIb.
  • mF44 and mF46 resulting from increasing the Fc ⁇ R-binding activity of native mouse IgG1 show selectively enhanced binding to mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII.
  • the soluble antigen concentration was reduced in the plasma of Fc ⁇ RIII-deficient mice, which mimic the condition of administration of an antibody with selectively increased mouse Fc ⁇ RIIb-binding activity. Meanwhile, whether the soluble antigen concentration is reduced in the plasma of Fc ⁇ RIIb-deficient mice, which mimic the condition of administration of an antibody with selectively increased mouse Fc ⁇ RIII-binding activity, was assessed by the test described below.
  • the soluble human IL-6 receptor concentrations in plasma were determined by the method described in Example (2-1-2). The result is shown in FIG. 14 .
  • mice that express mouse Fc ⁇ RIIb but not mouse Fc ⁇ RIII i.e., Fc ⁇ RIII-deficient mice and Fc receptor ⁇ chain-deficient mice
  • the elimination of soluble IL-6 receptor from plasma was also accelerated markedly in the mice.
  • mice that express mouse Fc ⁇ RIII but not mouse Fc ⁇ RIIb i.e., Fc ⁇ RII-deficient mice
  • the elimination of soluble IL-6 receptor from plasma was not remarkably accelerated in the mice.
  • the antibodies mF44 and mF46 in which the binding activity of mIgG1 (native mouse IgG1) to mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII is increased, are incorporated into Fc ⁇ R-expressing cells mainly by mouse Fc ⁇ RIIb, and thus the soluble antigen in the plasma that binds to the antibodies is eliminated. Meanwhile, the Fc ⁇ RIII-mediated incorporation of antibody/antigen complexes into Fc ⁇ R-expressing cells is thought not to significantly contribute to the elimination of the soluble antigen from plasma.
  • Example 4 the plasma concentration of soluble IL-6 receptor was markedly reduced in mice administered with Fv4-IgG1-F1087 having increased binding activity to mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII, in particular. Meanwhile, the effect to eliminate soluble IL-6 receptor from the plasma of mice administered with Fv4-IgG1-F1182 with increased binding activity to mouse Fc ⁇ RI and mouse Fc ⁇ RIV, in particular, was smaller than that of Fv4-IgG1-F1087.
  • mice administered with Fv4-IgG1-Fuc whose mouse Fc ⁇ RIV-binding activity has been considerably increased by having sugar chains with low fucose content (Science (2005) 310 (5753), 1510-1512)
  • the plasma concentration of soluble IL-6 receptor was reduced as compared to that in mice administered with Fv4-IgG1; however, the reduction effect was as small as about twice.
  • mouse Fc ⁇ RIV-mediated incorporation of antibodies into Fc ⁇ R-expressing cells is thought not to significantly contribute to the elimination of soluble antigens from plasma.
  • mouse Fc ⁇ RIIb plays a major role in antibody incorporation into Fc ⁇ R-expressing cells in mice.
  • mutations to be introduced into the mouse Fc ⁇ R-binding domain particularly preferably include, but are not limited to, mutations that enhance the binding to mouse Fc ⁇ RIIb.
  • the Fc ⁇ RIIb-binding activity of the antibodies to be administered is more preferably increased to accelerate the elimination of soluble antigens from the plasma of a living organism by administering to it antigen-binding molecules that bind to soluble antigens in a pH-dependent manner and have increased Fc ⁇ R binding activity.
  • antigen-binding molecules that bind to soluble antigens in a pH-dependent manner and have increased Fc ⁇ RIIb-binding activity can accelerate the elimination of the soluble antigens from plasma and effectively reduce the plasma concentration of soluble antigens, and thus, the antigen-binding molecules were revealed to show a very effective action.
  • antigens can be efficiently eliminated from the plasma of the living organism by administering antibodies with selectively increased Fc ⁇ RIIb-binding activity to the living organism. Furthermore, the administration of antibodies containing an Fc region with selectively increased Fc ⁇ RIIb-binding activity is thought to be preferred from the viewpoint of safety and side effects in the living organism administered with such antibodies.
  • mouse Fc ⁇ RIIb binding and mouse Fc ⁇ RIII binding are both enhanced in mF44 and mF46, and thus the binding enhancement is not selective for mouse Fc ⁇ RIIb. Since the homology between mouse Fc ⁇ RIIb and mouse Fc ⁇ RIII is high, it would be difficult to find an alteration that enhances the mouse Fc ⁇ RIIb-selective binding while distinguishing the two. Moreover, there is no previous report on Fc regions with selectively enhanced mouse Fc ⁇ RIIb binding. Also, the homology between human Fc ⁇ RIIb and human Fc ⁇ RIIa (the two allotypes, 131Arg and 131His) is also known to be high.
  • Antibodies containing an Fc region introduced with an existing alteration that enhances the human Fc ⁇ RIIb binding were analyzed for their affinity for human Fc ⁇ RIa, R-type and H-type Fc ⁇ RIIa, Fc ⁇ RIIb, and Fc ⁇ RIIIa by the following procedure.
  • An H chain was constructed to have, as the antibody H chain variable region, the antibody variable region IL6R-H (SEQ ID NO: 53) against human interleukin 6 receptor which is disclosed in WO2009/125825, and as the antibody H chain constant region, IL6R-G1d (SEQ ID NO: 54) that has G1d resulting from removing the C-terminal Gly and Lys from human IgG1.
  • IL6R-G1d-v3 (SEQ ID NO: 55) was constructed by altering the Fc region of IL6R-G1d by the substitution of Glu for Ser at position 267 (EU numbering) and Phe for Leu at position 328 (EU numbering), as described in Seung et al., (Mol. Immunol. (2008) 45, 3926-3933).
  • IL6R-L (SEQ ID NO: 56) which is the L chain of anti-human interleukin 6 receptor antibody was used as a common antibody L chain, and expressed in combination with respective H chains according to the method described in Reference Example 1, and the resulting antibodies were purified.
  • IgG1 and IgG1-v3 antibodies containing IL6R-G1d and IL6R-G1d-v3 as the heavy chain are referred to as IgG1 and IgG1-v3, respectively.
  • a sensorgram obtained as a result of the measurement was analyzed using 1:1 Langmuir binding model with Biacore Evaluation Software, and binding rate constant ka (L/mol/s) and dissociation rate constant kd (l/s) were calculated, and the dissociation constant KD (mol/l) was calculated from these values.
  • the KD values of IgG1 and IgG1-v3 to each Fc ⁇ R are shown in Table 11, while the relative KD values of IgG1-v3, which are obtained by dividing KD of IgG1 to each Fc ⁇ R by KD of IgG1-v3 to each Fc ⁇ R, are shown in Table 12.
  • the antibody comprising as the light chain omalizumab_VL-CK (SEQ ID NO: 58) and omalizumab_VH-G1d (SEQ ID NO: 57) that contains the heavy chain variable region of hIgG1 antibody (human IgG1 constant region) that binds to IgE and the G1d heavy chain constant region, was constructed using the method described in Reference Example 1. Furthermore, omalizumab_VH-G1d-v3 (SEQ ID NO: 59) was constructed by substituting Glu for Ser at position 267 and Phe for Leu at position 328 (EU numbering) in omalizumab_VH-G1d.
  • Omalizumab-G1d-v3 which contains omalizumab_VH-G1d-v3 as the heavy chain and omalizumab_VL-CK as the light chain, was prepared using the method described in Reference Example 1. This antibody was assessed for the platelet aggregatory ability.
  • Platelet aggregation was assayed using the platelet aggregometer HEMA TRACER 712 (LMS Co.). First, about 50 ml of whole blood was collected at a fixed amount into 4.5-ml evacuated blood collection tubes containing 0.5 ml of 3.8% sodium citrate, and this was centrifuged at 200 g for 15 minutes. The resultant supernatant was collected and used as platelet-rich plasma (PRP).
  • LMS Co. platelet aggregometer HEMA TRACER 712
  • buffer A 137 mM NaCl, 2.7 mM KCl, 12 mM NaHCO 3 , 0.42 mM NaH 2 PO 4 , 2 mM MgCl 2 , 5 mM HEPES, 5.55 mM dextrose, 1.5 U/ml apyrase, 0.35% BSA
  • buffer B 137 mM NaCl, 2.7 mM KCl, 12 mM NaHCO 3 , 0.42 mM NaH 2 PO 4 , 2 mM MgCl 2 , 5 mM HEPES, 5.55 mM dextrose, 2 mM CaCl 2 , 0.35% BSA).
  • washed platelets at a density of about 300,000/ ⁇ l.
  • 156 ⁇ l of the washed platelets was aliquoted into assay cuvettes containing a stir bar in the platelet aggregometer. The platelets were stirred at 1000 rpm with the stir bar in the cuvettes maintained at 37.0° C. in the platelet aggregometer.
  • ADP adenosine diphosphate
  • FIGS. 15 and 16 The result of platelet aggregation for each donor with an Fc ⁇ RIIa polymorphic form (H/H or R/H) obtained from the above assay is shown in FIGS. 15 and 16 . From the result in FIG. 15 , it is shown that platelet aggregation is enhanced when the immune complex is added to the platelets of a donor with the Fc ⁇ RIIa polymorphic form (R/H). Meanwhile, as shown in FIG. 16 , platelet aggregation was not enhanced when the immune complex is added to the platelets of a donor with the Fc ⁇ RIIa polymorphic form (H/H).
  • platelet activation was assessed using activation markers.
  • Platelet activation can be measured based on the increased expression of an activation marker such as CD62p (p-selectin) or active integrin on the platelet membrane surface.
  • an activation marker such as CD62p (p-selectin) or active integrin on the platelet membrane surface.
  • 2.3 ⁇ l of the immune complex was added to 7.7 ⁇ l of the washed platelets prepared by the method described above. After five minutes of reaction at room temperature, activation was induced by adding ADP at a final concentration of 30 ⁇ M, and whether the immune complex enhances the ADP-dependent activation was assessed.
  • Staining was performed by adding, to each post-reaction sample, PE-labeled anti-CD62 antibody (BECTON DICKINSON), PerCP-labeled anti-CD61 antibody, and FITC-labeled PAC-1 antibody (BD bioscience). Fluorescence intensity for each stain was measured using a flow cytometer (FACS CantoII, BD bioscience).
  • the risk of developing thrombosis due to platelet aggregation can be increased when an antibody containing an Fc region introduced with an existing alteration that enhances the binding to existing human Fc ⁇ RIIb is administered to humans having R-type Fc ⁇ RIIa. It was shown that the antigen-binding molecules containing an Fc region of the present invention that enhances the Fc ⁇ RIIb binding more selectively not only improves the antigen retention in plasma, but also possibly solves the above problems. Thus, the usefulness of the antigen-binding molecules of the present invention is obvious.
  • IL6R-F11 (SEQ ID NO: 60) was produced by introducing an alteration of substituting Met at position 252 (EU numbering) with Tyr and an alteration of substituting Asn at position 434 (EU numbering) with Tyr in IL6R-G1d (SEQ ID NO: 54) which was used as the antibody H chain. Furthermore, IL6R-F652 (SEQ ID NO: 61) was prepared by introducing an alteration of substituting Pro at position 238 (EU numbering) with Asp into IL6R-F11.
  • Expression plasmids containing an antibody H chain sequence were prepared for each of the antibody H chain sequences produced by substituting the region near the residue at position 238 (EU numbering) (positions 234 to 237, and 239 (EU numbering)) in L6R-F652 each with 18 amino acids excluding the original amino acids and Cysteine.
  • IL6R-L SEQ ID NO: 56
  • PD variants Interactions of each PD variant with Fc ⁇ RIIa type R and Fc ⁇ RIIb were comprehensively evaluated by the method of Reference Example 2.
  • a figure that shows the results of analyzing the interaction with the respective Fc ⁇ Rs was produced according to the following method.
  • the horizontal axis shows relative values of the Fc ⁇ RIIb-binding activity of each PD variant
  • the vertical axis shows relative values of the Fc ⁇ RIIa type R-binding activity values of each PD variant ( FIG. 19 ).
  • FIG. 20 shows relative values for the Fc ⁇ RIIb-binding activity obtained by additionally introducing the above eleven alterations into a variant carrying the P238D alteration, and relative values for the Fc ⁇ RIIb-binding activity of a variant obtained by introducing the alterations into an Fc that does not contain the P238D.
  • These eleven alterations enhanced the amount of Fc ⁇ RIIb binding compared with before introduction when they were further introduced into the P238D variant.
  • the effect of lowering Fc ⁇ RIIb binding was observed for eight of those alterations except G237F, G237W, and S239D, when they were introduced into the variant that does not contain P238D (data not shown).
  • KD (IIaR)/KD (IIb) and KD (IIaH)/KD (I %) in the table respectively show the value obtained by dividing the KD value of each variant for Fc ⁇ RIIaR by the KD value of each variant for Fc ⁇ RIIb, and the value obtained by dividing the KD value of each variant for Fc ⁇ RIIaH by the KD value of each variant for Fc ⁇ RIIb.
  • KD (IIb) of the parent polypeptide/KD (IIb) of the variant refers to a value obtained by dividing the KD value of the parent polypeptide for Fc ⁇ RIIb by the KD value of each variant for Fc ⁇ RIIb.
  • Table 14 shows KD values for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of each variant/KD values for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide.
  • parent polypeptide refers to a variant which has IL6R-F11 (SEQ ID NO: 60) as the H chain. It was determined that due to weak binding of Fc ⁇ R to IgG, it was impossible to accurately analyze by kinetic analysis, and thus the gray-filled cells in Table 14 show values calculated by using Equation 2 of Reference Example 2.
  • Table 14 shows that all variants improved their affinity for Fc ⁇ RIIb in comparison with IL6R-F11, and the range of improvement was 1.9 fold to 5.0 fold.
  • the ratio of KD value of each variant for Fc ⁇ RIIaR/KD value of each variant for Fc ⁇ RIIb, and the ratio of KD value of each variant for Fc ⁇ RIIaH/KD value of each variant for Fc ⁇ RIIb represent an Fc ⁇ RIIb-binding activity relative to the Fc ⁇ RIIaR-binding activity and Fc ⁇ RIIaH-binding activity, respectively. That is, these values show the degree of binding selectivity of each variant for Fc ⁇ RIIb, and a larger value indicates a higher binding selectivity for Fc ⁇ RIIb.
  • the ratio of KD value for Fc ⁇ RIIaR/KD value for Fc ⁇ RIIb and the ratio of KD value for Fc ⁇ RIIaH/KD value for Fc ⁇ RIIb are both 0.7, and accordingly all variants in Table 14 showed improvement of binding selectivity for Fc ⁇ RIIb in comparison with the parent polypeptide.
  • the KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of a variant/KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide is 1 or more, this means that the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of a variant has equivalent or reduced binding compared with the binding by the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide.
  • Fc (P238D) an IgG1 Fc containing the P238D mutation
  • Fc (WT) the extracellular region of Fc ⁇ RIIb
  • the three-dimensional structure of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex was determined by X-ray crystal structure analysis at 2.6 ⁇ resolution. The structure obtained as a result of this analysis is shown in FIG. 21 .
  • the Fc ⁇ RIIb extracellular region is bound between two Fc CH2 domains, and this was similar to the three-dimensional structures of complexes formed between Fc (WT) and the respective extracellular region of Fc ⁇ RIIIa, Fc ⁇ RIIIb, or Fc ⁇ RIIa analyzed so far.
  • Pro at position 238 (EU numbering) is originally located inside Fc (WT), forming a hydrophobic core with residues around position 238.
  • Fc Fc
  • the amino acid residue at position 238 (EU numbering) changes its orientation to face the solvent region, and this may have caused this change in the loop structure near the amino acid residue at position 238.
  • this loop is not far from the hinge region crosslinked by S—S bonds, its structural change will not be limited to a local change, and will affect the relative positioning between the FcCH2 domain A and domain B.
  • the interatomic interactions between Fc ⁇ RIIb and Fc CH2 domain B were assumed to have been changed. Therefore, predicted effects could not be observed when alterations that improve selectivity and binding activity towards Fc ⁇ RIIb in a naturally-occurring IgG were combined with an Fc containing the P238D alteration.
  • Fc ⁇ RIIa type H which is one of the allotypes of Fc ⁇ RIIa
  • the residue corresponding to Arg at position 131 of Fc ⁇ RIIb is His, and therefore cannot form this electrostatic interaction. This can explain why the Fc (P238D)-binding activity is lowered in Fc ⁇ RIIa type H compared with Fc ⁇ RIIa type R.
  • An Fc containing the P238D alteration was prepared as follows. First, Cys at position 220 (EU numbering) of hIL6R-IgG1-v1 (SEQ ID NO: 62) was substituted with Ser. Then, genetic sequence of Fc (P238D) from Glu at position 236 (EU numbering) to its C terminal was cloned by PCR. Using this cloned genetic sequence, production of expression vectors, and expression and purification of Fc (P238D) were carried out according to the method of Reference Example 1. Cys at position 220 (EU numbering) forms a disulfide bond with Cys of the L chain in general IgG1. The L chain is not co-expressed when Fc alone is prepared, and therefore, the Cys residue was substituted with Ser to avoid formation of unnecessary disulfide bonds.
  • the Fc ⁇ RIIb extracellular region was prepared according to the method of Reference Example 2.
  • Endo F1 Protein Science (1996) 5: 2617-2622 expressed and purified from Escherichia coli as a glutathione S-transferase fusion protein was added. This was allowed to remain at room temperature for three days in 0.1 M Bis-Tris buffer at pH 6.5, and the N-linked sugar chains were cleaved, except for N-acetylglucosamine directly bound to Asn of the Fc ⁇ RIIb extracellular region.
  • the Fc ⁇ RIIb extracellular region sample subjected to sugar chain cleavage treatment which was concentrated by ultrafiltration with 5000 MWCO, was purified by gel filtration chromatography (Superdex200 10/300) using a column equilibrated in 20 mM HEPS at pH 7.5 containing 0.05 M NaCl. Furthermore, to the obtained carbohydrate-cleaved Fc ⁇ RIIb extracellular region fraction, Fc (P238D) was added so that the molar ratio of the Fc ⁇ RIIb extracellular region would be present in slight excess.
  • the mixture concentrated by ultrafiltration with 10,000 MWCO was purified by gel filtration chromatography (Superdex200 10/300) using a column equilibrated in 20 mM HEPS at pH 7.5 containing 0.05 M NaCl.
  • Gel filtration chromatography Superdex200 10/300
  • Xia2 program CCP4 Software Suite
  • XDS Package Walfgang Kabsch
  • Scala CCP4 Software Suite
  • diffraction intensity data of the crystal up to 2.46 ⁇ resolution was obtained.
  • Crystal structure of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex was determined by the molecular replacement method using the program Phaser (CCP4 Software Suite). From the size of the obtained crystal lattice and the molecular weight of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex, the number of complexes in the asymmetric unit was predicted to be one. From the structural coordinates of PDB code: 3SGJ which is the crystal structure of the Fc (WT)/Fc ⁇ RIIIa extracellular region complex, the amino acid residue portions of the A chain positions 239-340 and the B chain positions 239-340 were taken out as separate coordinates, and they were set respectively as models for searching the Fc CH2 domains.
  • the amino acid residue portions of the A chain positions 341-444 and the B chain positions 341-443 were taken out as a single set of coordinates from the same structural coordinates of PDB code: 3SGJ; and this was set as a model for searching the Fc CH3 domains. Finally, from the structural coordinates of PDB code: 2FCB which is a crystal structure of the Fc ⁇ RIIb extracellular region, the amino acid residue portions of the A chain positions 6-178 was taken out and set as a model for searching the Fc ⁇ RIIb extracellular region.
  • each search model in the crystal lattice were determined in the order of Fc CH3 domain, Fc ⁇ RIIb extracellular region, and Fc CH2 domain, based on the rotation function and translation function to obtain the initial model for the crystal structure of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex.
  • the crystallographic reliability factor, R value became 40.4%
  • the Free R value became 41.9% to diffraction intensity data from 25 ⁇ to 3.0 ⁇ at this point.
  • variants were constructed by comprehensively introducing alterations into sites on the altered Fc having substitution of Pro at position 238 (EU numbering) with Asp that were predicted to affect interaction with Fc ⁇ RIIb (residues of positions 233, 240, 241, 263, 265, 266, 267, 268, 271, 273, 295, 296, 298, 300, 323, 325, 326, 327, 328, 330, 332, and 334 (EU numbering)), and whether combinations of alterations that further enhance Fc ⁇ RIIb binding in addition to the P238D alteration can be obtained, was examined.
  • EU numbering Pro at position 238
  • IL6R-B3 (SEQ ID NO: 63) was produced by introducing into IL6R-G1d (SEQ ID NO: 54), the alteration produced by substituting Lys at position 439 (EU numbering) with Glu.
  • IL6R-BF648 was produced by introducing into IL6R-B3, the alteration produced by substituting Pro at position 238 (EU numbering) with Asp.
  • IL6R-L SEQ ID NO: 56
  • a figure was produced according to the following method to show the results of analyzing the interactions with the respective Fc ⁇ Rs.
  • the value for the amount of binding of each variant to each Fc ⁇ R was divided by the value for the amount of binding of the pre-altered control antibody (IL6R-BF648/IL6R-L, alteration by substituting Pro at position 238 (EU numbering) with Asp) to each Fc ⁇ R, and the obtained was then multiplied by 100 and shown as the relative binding activity value of each variant to each Fc ⁇ R.
  • the horizontal axis shows the relative binding activity value of each variant to Fc ⁇ RIIb
  • the vertical axis shows the relative binding activity value of each variant to Fc ⁇ RIIa type R ( FIG. 26 ).
  • KD (IIaR)/KD (IIb) and KD (IIaH)/KD (IIb) in the table respectively represent the value obtained by dividing the KD value of each variant for Fc ⁇ RIIaR by the KD value of each variant for Fc ⁇ RIIb, and the value obtained by dividing the KD value of each variant for Fc ⁇ RIIaH by the KD value of each variant for Fc ⁇ RIIb.
  • KD (IIb) of the parent polypeptide/KD (IIb) of the altered polypeptide refers to the value obtained by dividing the KD value of the parent polypeptide for Fc ⁇ RIIb by the KD value of each variant for Fc ⁇ RIIb.
  • the KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of each variant/KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide are shown in Table 17.
  • parent polypeptide refers to the variant which has IL6R-B3 (SEQ ID NO: 63) as the H chain. It was determined that due to weak binding of Fc ⁇ R to IgG, it was impossible to accurately analyze by kinetic analysis, and thus the gray-filled cells in Table 17 show values calculated by using Equation 2 of Reference Example 2.
  • Table 17 shows that in comparison with IL6R-B3, all variants showed improvement of affinity for Fc ⁇ RIIb, and the range of improvement was 2.1 fold to 9.7 fold.
  • the ratio of KD value of each variant for Fc ⁇ RIIaR/KD value of each variant for Fc ⁇ RIIb, and the ratio of KD value of each variant for Fc ⁇ RIIaH/KD value of each variant for Fc ⁇ RIIb represent an Fc ⁇ RIIb-binding activity relative to the Fc ⁇ RIIaR-binding activity and Fc ⁇ RIIaH-binding activity, respectively. That is, these values show the degree of binding selectivity of each variant for Fc ⁇ RIIb, and a greater value indicates a higher binding selectivity for Fc ⁇ RIIb.
  • the KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of a variant/KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide is 1 or more, this means that the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of a variant has equivalent or decreased binding compared with the binding by the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide.
  • FIG. 27 shows the crystal structure of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex.
  • the H chain positioned on the left side is Fc Chain A
  • the H chain positioned on the right side is Fc Chain B.
  • the site at position 233 (EU numbering) in Fc Chain A is located near Lys at position 113 of Fc ⁇ RIIb.
  • the E233 side chain is in a condition of considerably high mobility, and its electron density is not well observed.
  • FIG. 28 shows the surrounding near the site at position 330 (EU numbering) in the structure of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex.
  • This figure shows that the surrounding around the site at position 330 (EU numbering) of Fc Chain A of Fc (P238D) is a hydrophilic environment composed of Ser at position 85, Glu at position 86, Lys at position 163, and such of Fc ⁇ RIIb. Therefore, the alteration produced by substituting Ala at position 330 (EU numbering) with Lys or Arg is speculated to contribute to strengthening the interaction with Ser at position 85 or Glu at position 86 in Fc ⁇ RIIb.
  • FIG. 29 depicts the structures of Pro at position 271 (EU numbering) of Fc Chain B after superimposing the crystal structures of the Fc (P238D)/Fc ⁇ RIIb extracellular region complex and the Fc (WT)/Fc ⁇ RIIIa extracellular region complex by the least squares fitting based on the C ⁇ atom pair distances with respect to Fc Chain B. These two structures match well, but have different three-dimensional structures of Pro at position 271 (EU numbering).
  • Table 18-2 is a continuation table of Table 18-1.
  • KD (IIaR)/KD (IIb) and KD (IIaH)/KD (IIb) in the table respectively represent the value obtained by dividing the KD value of the variant for Fc ⁇ RIIaR by the KD value of the variant for Fc ⁇ RIIb, and the value obtained by dividing the KD value of the variant for Fc ⁇ RIIaH by the KD value of each variant for Fc ⁇ RIIb.
  • KD (IIb) of the parent polypeptide/KD (IIb) of the altered polypeptide refers to the value obtained by dividing the KD value of the parent polypeptide for Fc ⁇ RIIb by the KD value of each variant for Fc ⁇ RIIb.
  • the KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of each variant/KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide are shown in Tables 19-1 and 19-2.
  • parent polypeptide refers to the variant which has IL6R-B3 (SEQ ID NO: 63) as the H chain. It was determined that due to weak binding of Fc ⁇ R to IgG, it was impossible to accurately analyze by kinetic analysis, and thus the values of gray-filled cells in Tables 19-1 and 19-2 show values calculated by using Equation 2 of Reference Example 2.
  • Tables 19-1 and 19-2 show that in comparison with IL6R-B3, all variants showed improvement of affinity for Fc ⁇ RIIb, and the range of improvement was 3.0 fold to 99.0 fold.
  • the ratio of KD value of each variant for Fc ⁇ RIIaR/KD value of each variant for Fc ⁇ RIIb, and the ratio of KD value of each variant for Fc ⁇ RIIaH/KD value of each variant for Fc ⁇ RIIb represent an Fc ⁇ RIIb-binding activity relative to the Fc ⁇ RIIaR-binding activity and Fc ⁇ RIIaH-binding activity, respectively.
  • the KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of a variant/KD value for the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide is 1 or more, this means that the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of a variant has equivalent or decreased binding compared with the binding by the stronger of the Fc ⁇ RIIaR- and Fc ⁇ RIIaH-binding activities of the parent polypeptide.
  • Table 19-2 is a continuation table of Table 19-1.
  • the present inventors when enhancing the Fc ⁇ RIIb binding, it is preferable that the Fc ⁇ RIIb binding is enhanced while maximally suppressing the binding to other activating Fc ⁇ Rs.
  • the present inventors additionally produced variants with enhanced Fc ⁇ RIIb binding or improved selectivity to Fc ⁇ RIIb by combining alterations that enhance the Fc ⁇ RIIb binding or improving the selectivity to Fc ⁇ RIIb.
  • the alterations described in Examples 9, 11, and 12 which were found to be effective when combined with alteration P238D, were combined with one another, on the basis of the P238D alteration which showed the excellent effect to enhance the Fc ⁇ RIIb binding and to improve the selectivity to Fc ⁇ RIIb.
  • Variants were produced by combining the Fc regions of IL6R-G1d (SEQ ID NO: 54) and IL6R-B3 (SEQ ID NO: 63) with alterations E233D, L234Y, G237D, S267Q, H268D, P271G, Y296D, K326D, K326A, A330R, and A330K described in Examples 9, 11, and 12 which were found to be effective when combined with alteration P238D.
  • IL6R-L SEQ ID NO: 56
  • antibodies comprising the above-described variants in the heavy chain were expressed and purified according to the method described in Reference Example 1.
  • KD of each variant to each Fc ⁇ R is shown in Table 20.
  • “Alteration” refers to an alteration introduced into IL6R-B3 (SEQ ID NO: 63).
  • IL6R-B3/IL6R-L which is used as the template to produce each variant is indicated by asterisk (*).
  • “KD (IIaR)/KD (IIb)” in the table shows the value obtained by dividing the KD of each variant for Fc ⁇ RIIaR by the KD of each variant for Fc ⁇ RIIb. The greater the value, the higher the selectivity to Fc ⁇ RIIb.
  • KD (I %) of parent polypeptide/KD (I %) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for Fc ⁇ RIIb by the KD value of each variant for Fc ⁇ RIIb.
  • KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for Fc ⁇ RIIaR by the KD value of each variant for Fc ⁇ RIIaR.
  • Table 20 the numeral in the gray-filled cells indicates that the binding of Fc ⁇ R to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:
  • the binding of IL6R-B3/IL6R-L to Fc ⁇ R was comparable to the binding of IL6R-G1d/IL6R-L to Fc ⁇ R.
  • the comparison of the binding of each variant to each Fc ⁇ R with that of IL6R-B3/IL6R-L prior to introduction of the alteration is assumed to be equivalent to the comparison of the binding of each variant to each Fc ⁇ R with the binding to each Fc ⁇ R by IL6R-G1d/IL6R-L containing the sequence of native human IgG1.
  • each variant to each Fc ⁇ R will be compared to that to each Fc ⁇ R by IL6R-B3/IL6R-L prior to introduction of the alteration.
  • Table 20 shows that all the variants have increased Fc ⁇ RIIb binding activity as compared to IL6R-B3 prior to introduction of the alteration.
  • IL6R-BP230/IL6R-L As shown in Example 13, the Fc ⁇ RIIb binding of variant IL6R-BP230/IL6R-L, whose Fc ⁇ RIIb binding was enhanced most, was enhanced to about 150 times as compared to IL6R-B3/IL6R-L prior to introduction of the alteration, while the enhancement of its Fc ⁇ RIIaR binding was suppressed to an extent of about 1.9 times.
  • IL6R-BP230/IL6R-L is a variant excellent in both Fc ⁇ RIIb binding and selectivity.
  • the present inventors sought a possibility to create more preferable variants with further enhanced Fc ⁇ RIIb binding while suppressing the Fc ⁇ RIIaR binding as possible.
  • the extracellular regions of Fc ⁇ RIIa and Fc ⁇ RIIb are 93% identical in amino acid sequence, and thus they have very high homology.
  • Fc native IgG1
  • Fc ⁇ RIIaR the extracellular region of Fc ⁇ RIIaR
  • the present inventors conceived that, in order to further enhance the Fc ⁇ RIIb-binding activity of the Fc region, and to improve the selectivity of the Fc regions between the binding to Fc ⁇ RIIb and Fc ⁇ RIIaR binding, it was important to clarify subtle differences between Fc region-Fc ⁇ RIIb interaction and Fc region-Fc ⁇ RIIaR interaction by analyzing not only the three-dimensional structure of the complex of the Fc region with enhanced Fc ⁇ RIIb binding and the extracellular region of Fc ⁇ RIIb but also the three-dimensional structure of the complex of the Fc region with enhanced Fc ⁇ RIIb binding and the extracellular region of Fc ⁇ RIIaR.
  • the present inventors analyzed the X-ray crystal structure of the complex of the extracellular region of Fc ⁇ RIIb or Fc ⁇ RIIaR and Fc (P208) resulting from eliminating the K439E alteration from the Fc region of IL6R-BP208/IL6R-L created as described in Example 12, which was the variant used as the base in producing IL6R-BP230/IL6R-L.
  • Fc (P208) was prepared as described below. First, IL6R-P208 was produced by substituting Lys for Glu at position 439 (EU numbering) in IL6R-BP208, as is in the case of the sequence of native human IgG1. Then, the gene sequence of Fc (P208), which was cloned by PCR from Glu at position 216 (EU numbering) to the C terminus using as a template a DNA encoding a variant with a substitution of Ser for Cys at position 220 (EU numbering), was cloned. Expression vector construction, expression, and purification were achieved according to the method described in Reference Example 1.
  • Cys at position 220 (EU numbering) in ordinary IgG1 forms a disulfide bond to a Cys in the L chain.
  • the L chain is not co-expressed.
  • Cys at position 220 was substituted by Ser to avoid unnecessary disulfide bond formation.
  • the extracellular region of Fc ⁇ RIIb was prepared according to the method described in Reference Example 2.
  • the sample of the extracellular region of Fc ⁇ RIIb subjected to the sugar chain cleavage treatment was concentrated with a 5000MWCO ultrafiltration filter, and purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 20 mM HEPES (pH7.5)/0.1 M NaCl. Furthermore, to the purified Fc ⁇ RIIb extracellular region fraction with its sugar chains cleaved, Fc (P208) was added so that the molar ratio of the Fc ⁇ RIIb extracellular region would be present in slight excess.
  • the mixture concentrated by ultrafiltration with 10,000 MWCO was purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 25 mM HEPES (pH 7.5), 0.1 M NaCl.
  • the purified fraction prepared as described above was used as a sample of Fc (P208)/Fc ⁇ RIIb extracellular region complex in the subsequent assessment.
  • a sample of Fc (P208)/Fc ⁇ RIIb extracellular region complex concentrated to about 10 mg/ml with a 10000 MWCO ultrafiltration filter was crystallized using the hanging drop vapor diffusion method in combination with the seeding method.
  • VDXm plate (Hampton Research) was used for crystallization.
  • the crystallization drops were added with 0.15 ⁇ l of a diluted solution prepared from the seed solution and allowed to stand at 20° C. in sealed reservoir wells. This yielded plate-like crystals.
  • a single crystal of Fc (P208)/Fc ⁇ RIIb extracellular region complex prepared as described above was soaked into a solution of 0.1 M Bis-Tris (pH 6.5), 24% (w/v) PEG3350, 0.2 M potassium phosphate dibasic, 20% (v/v) ethylene glycol. Then, the single crystal was fished out of the solution using a pin with attached tiny nylon loop, and frozen in liquid nitrogen. X-ray diffraction data of the single crystal was collected at Spring-8 BL32XU. During the measurement, the crystal was constantly placed in a nitrogen stream at ⁇ 178° C. to maintain in a frozen state.
  • a total of 300 X-ray diffraction images from the single crystal were collected using CCD detector MX-225HE (RAYONIX) attached to a beam line with rotating the single crystal 0.6° at a time.
  • lattice constant determination, diffraction spot indexing, and diffraction data processing were performed using programs Xia2 (J. Appl. Cryst. (2010) 43, 186-190), XDS Package (Acta Cryst. (2010) D66, 125-132) and Scala (Acta Cryst. (2006) D62, 72-82).
  • the diffraction intensity data of the single crystal up to 2.81 ⁇ resolution was obtained.
  • Fc (P208)/Fc ⁇ RIIb extracellular region complex was determined by a molecular replacement method using program Phaser (J. Appl. Cryst. (2007) 40, 658-674).
  • the number of complexes in an asymmetrical unit was estimated to be one from the size of the obtained crystal lattice and the molecular weight of Fc (P208)/Fc ⁇ RIIb extracellular region complex.
  • amino acid residue portions of the A chain positions 239-340 and the B chain positions 239-340 which were taken out as a separate coordinate from the structural coordinate of PDB code: 3SGJ for the crystal structure of Fc (WT)/Fc ⁇ RIIIa extracellular region complex, were used respectively as models for searching the CH2 domain of the Fc region.
  • amino acid residue portions of the A chain positions 341-444 and the B chain positions 341-443 which were taken out as a single coordinate from the structural coordinate of PDB code: 3SGJ, were used as a model for searching the CH3 domain of the Fc region.
  • amino acid residue portions of the A chain positions 6-178 which were taken out from the structural coordinate of PDB code: 2FCB for the crystal structure of the extracellular region of Fc ⁇ RIIb, were used as a model for searching Fc (P208).
  • the present inventors tried to determine the orientations and positions of the respective search models of the CH3 domain of the Fc region, the extracellular region of Fc ⁇ RIIb, and the CH2 domain of the Fc region in the crystal lattices based on the rotation function and translation function, but failed to determine the position of one of the CH2 domains.
  • the position of the last CH2 domain A was determined based on an electron density map that was calculated based on the phase determined from the remaining three parts.
  • the present inventors obtained an initial model for the crystal structure of the complex of Fc (P208)/Fc ⁇ RIIb extracellular region.
  • the crystallographic reliability factor R value of the structural model for the data of diffracted intensity at 25 to 3.0 ⁇ was 42.6% and Free R value was 43.7% after rigid body refinement of the obtained initial structural model which moves the two CH2 domains and two CH3 domains of the Fc region, and the extracellular region of Fc ⁇ RIIb.
  • structural model refinement was achieved by repeating structural refinement using program REFMAC5 (Acta Cryst. (2011) D67, 355-367) followed by revision of the structural model performed using program Coot (Acta Cryst. (2010) D66, 486-501) with reference to the electron density maps where the coefficients 2Fo-Fc and Fo-Fc were calculated using experimentally determined structural factor Fo, structural factor Fc region calculated according to the structural model, and the phases calculated according to the structural model.
  • REFMAC5 Acta Cryst. (2011) D67, 355-367
  • Coot Acta Cryst. (2010) D66, 486-501
  • the coefficients 2Fo-Fc and Fo-Fc were calculated using experimentally determined structural factor Fo, structural factor Fc region calculated according to the structural model, and the phases calculated according to the structural model.
  • the three-dimensional structure of the complex of Fc (P208)/Fc ⁇ RIIb extracellular region was determined at a resolution of 2.81 ⁇ by structure analysis.
  • the structure obtained by the analysis is shown in FIG. 30 .
  • Fc ⁇ RIIb extracellular region was revealed to be bound between the two CH2 domains of the Fc region, which resembles the three-dimensional structures of the previously analyzed complexes of Fc (WT), which is the Fc of native IgG, and each of the extracellular regions of Fc ⁇ RIIIa (Proc. Natl. Acad. Sci. USA (2011) 108, 12669-126674), Fc ⁇ RIIIb (Nature (2000) 400, 267-273; J. Biol. Chem. (2011) 276, 16469-16477), and Fc ⁇ RIIa (J. Immunol. (2011) 187 (6), 3208-3217).
  • Ser at position 239 was found as a candidate for the site to introduce alteration. As shown in FIG. 35 , Ser at position 239 (EU numbering) in the CH2 domain B is present at the position toward which Lys at position 117 in Fc ⁇ RIIb extends most naturally in structure. However, since the electron density was not observed for Lys at position 117 in Fc ⁇ RIIb by the analysis described above, the Lys has no definite structure. In this situation, Lys117 is likely to have only a limited effect on the interaction with Fc (P208).
  • the loop structure may become unstable due to loss of the hydrogen bond to the main chain of Gly at position 236 (EU numbering).
  • the alteration may result in electrostatic repulsion to Asp at position 265 (EU numbering) in close proximity, leading to further destabilization of the loop structure.
  • the energy for the destabilization corresponds to loss of free energy for the Fc ⁇ RIIb binding, which may result in reduction in the binding activity.
  • the extracellular region of Fc ⁇ RIIaR was prepared according to the method described in Reference Example 2.
  • the sample was further added with 0.07 mg of the above-described Endo F1, 7.5 ⁇ l of the above-described Endo F2, and 7.5 ⁇ l of the above-described Endo F3, and was incubated for three days to cleave off N-type sugar chains except N-acetylglucosamine directly linked to the Asn in the sample of the extracellular region of Fc ⁇ RIIaR.
  • the sample of the extracellular region of Fc ⁇ RIIaR concentrated with a 10000 MWCO ultrafiltration filter and subjected to the above-described sugar chain cleavage treatment was purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 25 mM HEPES (pH 7), 0.1 M NaCl.
  • Fc P208 was added so that the molar ratio of the Fc ⁇ RIIb extracellular region would be present in slight excess.
  • the mixture concentrated by ultrafiltration with 10,000 MWCO was purified by chromatography with a gel filtration column (Superdex200 10/300) equilibrated with 25 mM HEPES (pH 7), 0.1 M NaCl.
  • the purified fraction prepared as described above was used as a sample of Fc (P208)/Fc ⁇ RIIaR type extracellular region complex in the subsequent assessment.
  • a sample of Fc (P208)/Fc ⁇ RIIa R type extracellular region complex concentrated to about 10 mg/ml with a 10000 MWCO ultrafiltration filter was crystallized using the sitting drop vapor diffusion method.
  • a single crystal of Fc (P208)/Fc ⁇ RIIaR extracellular region complex prepared as described above was soaked into a solution of 0.1 M Bis-Tris (pH 7.5)), 27.5% (w/v) PEG3350, 0.2 M ammonium sulfate, 20% (v/v) glycerol. Then, the crystal was fished out of the solution using a pin with attached tiny nylon loop, and frozen in liquid nitrogen.
  • X-ray diffraction data of the single crystal was collected at synchrotron radiation facility Photon Factory BL-17A in the High Energy Accelerator Research Organization. The crystal was constantly placed in a nitrogen stream at ⁇ 178° C. to maintain in a frozen state during the measurement.
  • a total of 225 X-ray diffraction images from the single crystal were collected using CCD detector Quantum 315r (ADSC) equipped to the beam line with rotating the single crystal at 0.6° at a time.
  • ADSC CCD detector Quantum 315r
  • lattice constant determination, diffraction spot indexing, and diffraction data processing were performed using programs Xia2 (J. Appl. Cryst. (2010) 43, 186-190), XDS Package (Acta Cryst. (2010) D66, 125-132), and Scala (Acta Cryst. (2006) D62, 72-82).
  • diffraction intensity data up to 2.87 ⁇ resolution was obtained.
  • Fc (P208)/Fc ⁇ RIIaR type extracellular region complex was determined by a molecular replacement method using program Phaser (J. Appl. Cryst. (2007) 40, 658-674).
  • the number of complexes in an asymmetrical unit was estimated to be one from the size of the obtained crystal lattice and the molecular weight of Fc (P208)/Fc ⁇ RIIaR extracellular region complex.
  • structural model refinement was achieved by repeating structural refinement using program REFMAC5 (Acta Cryst. (2011) D67, 355-367) followed by revision of the structural model performed using program Coot (Acta Cryst. (2010) D66, 486-501) with reference to the electron density maps where the coefficients Fo-Fc and 2Fo-Fc were calculated using experimentally determined structural factor Fo, structural factor Fc calculated according to the model, and the phases calculated according to the model.
  • the three-dimensional structure of the complex of Fc (P208)/Fc ⁇ RIIaR extracellular region was determined at a resolution of 2.87 ⁇ by structure analysis.
  • a comparison of the crystal structure between the complex of Fc (P208)/Fc ⁇ RIIaR type extracellular region and the complex of Fc (P208)/Fc ⁇ RIIb extracellular region described in Example (14-1) detected almost no difference at the level of overall structure ( FIG. 36 ), reflecting the very high amino acid identity between the two Fc ⁇ receptors.
  • the amino acid residue at position 160 in Fc ⁇ RIIaR is not Tyr but Phe.
  • Tyr at position 160 (EU numbering) in Fc ⁇ RIIb interacts with the main chain of Asp at position 237 (EU numbering) in domain A of P208. Meanwhile, the side chain of Asp at position 237 (EU numbering) is located close to Ile at position 332, Glu at position 333, and Lys at position 334 (EU numbering) in the molecule without forming any particularly significant interaction.
  • the present inventors also assessed whether the interaction with Tyr at position 160 in Fc ⁇ RIIb can be enhanced through stabilization of the loop structure at positions 266 to 271 (EU numbering) due to increased interaction with the side chain of Asp at position 237 (EU numbering) by substituting hydrophilic amino acid residues at the positions described above.
  • Variants of IL6R-BP230/IL6R-L prepared as described in Example 13 were produced by introducing with each of the alterations H268E, I332T, I332S, 1332E, I332K, E333K, E333R, E333S, E333T, K334S, K334T, and K334E.
  • IL6R-L (SEQ ID NO: 56) was used as the antibody L chain.
  • Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each Fc ⁇ R (Fc ⁇ RIa, Fc ⁇ RIIaH, Fc ⁇ RIIaR, FcgRIIb, or FcgRIIIaV) by the method described in Reference Example 2.
  • KD of each variant to each Fc ⁇ R is shown in Table 21.
  • “alteration” refers to an alteration introduced into IL6R-BP3 (SEQ ID NO: 63).
  • IL6R-B3/IL6R-L which is used as the template to produce IL6R-BP230 is indicated by asterisk (*).
  • KD (IIb) of parent polypeptide/KD (IIb) of altered polypeptide in the table shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for Fc ⁇ RIIb by the KD value of each variant for Fc ⁇ RIIb.
  • KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for Fc ⁇ R IIaR by the KD value of each variant for Fc ⁇ R IIaR.
  • KD (IIaR)/KD (IIb) shows the value obtained by dividing the KD of each variant for Fc ⁇ RIIaR by the KD of the variant for Fc ⁇ RIIb. The greater the value, the higher the selectivity to Fc ⁇ RIIb.
  • Table 21 the numeral in the gray-filled cells indicates that the binding of Fc ⁇ R to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:
  • the Fc ⁇ RIIb selectivity of IL6R-BP391/IL6R-L introduced with the I332T alteration was reduced while its Fc ⁇ RIIb-binding activity was increased as compared to IL6R-BP230/IL6R-L.
  • IL6R-BP267 was constructed as a template in comprehensive introduction of alterations by introducing alterations E233D, G237D, P238D, H268E, and P271G into IL6R-B3 (SEQ ID NO: 63).
  • IL6R-L (SEQ ID NO: 56) was used as the antibody L chain.
  • Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each Fc ⁇ R (Fc ⁇ RIa, Fc ⁇ RIIaH, Fc ⁇ RIIaR, FcgRIIb, or FcgRIIIaV) by the method described in Reference Example 2.
  • IL6R-L SEQ ID NO: 56
  • Antibodies containing the light chain of IL6R-L and the above-described heavy chain variants were expressed and purified according to the method described in Reference Example 1. The purified antibodies were assessed for their binding to each Fc ⁇ R (Fc ⁇ RIa, Fc ⁇ RIIaH, Fc ⁇ RIIaR, Fc ⁇ RIIb, or Fc ⁇ RIIIaV) by the method described in Reference Example 2.
  • the KD value of each variant to each Fc ⁇ R is shown in Table 22.
  • “alteration” refers to an alteration introduced into IL6R-B3, which was used as a template.
  • IL6R-B3/IL6R-L which is used as the template to produce IL6R-BP267 is indicated by asterisk (*).
  • KD (I %) of parent polypeptide/KD (I %) of altered polypeptide shows the value obtained by dividing the KD value of IL6R-B3/IL6R-L for Fc ⁇ RIIb by the KD value of each variant for Fc ⁇ RIIb.
  • KD (IIaR) of parent polypeptide/KD (IIaR) of altered polypeptide shows the value obtained by dividing the KD of IL6R-B3/IL6R-L for Fc ⁇ RIIaR by the KD of each variant for Fc ⁇ R IIaR.
  • KD (IIaR)/KD (I %) shows the value obtained by dividing the KD value of each variant for Fc ⁇ RIIaR by the KD value of the variant for Fc ⁇ RIIb. The greater the value, the higher the selectivity to Fc ⁇ RIIb.
  • Table 22 the numeral in the gray-filled cells indicates that the binding of Fc ⁇ R to IgG was concluded to be too weak to analyze correctly by kinetic analysis and thus was calculated using:
  • KD (IIaR)/KD (IIb) values of variants resulting from adding the S267A, S267G, E272M, E272Q, D265E, E272D, E272N, V266L, E272I, and E272F alterations, respectively, to IL6R-BP267/IL6R-L were increased as compared to that of IL6R-BP267/IL6R-L prior to addition of alteration.

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