WO2010035012A1 - Biological products - Google Patents

Abstract

A multivalent antibody fusion protein which comprises an immunoglobulin moiety, for example a Fab or Fab' fragment, with a first specificity for an antigen of interest, and further comprises two single domain antibodies (dAb) with specificity for a second antigen of interest, wherein the two single domain antibodies are linked by a disulfide bond. There is also provided particular dual specificity antibody fusion proteins comprising a Fab or Fab' fragment and one or more single domain antibodies which may be stabilised by a disulfide bond therebetween.

Description

BIOLOGICAL PRODUCTS

The present invention relates to new dual specificity antibody fusion proteins. Such antibodies comprise a first specificity to an antigen of interest, and a second specificity for a second antigen of interest, for example a serum carrier protein for use in extending their in vivo serum half-life. Methods for the production of such molecules and pharmaceutical compositions comprising them are also provided.

The high specificity and affinity of antibodies makes them ideal diagnostic and therapeutic agents, particularly for modulating protein:protein interactions. Advances in the field of recombinant antibody technology have resulted in the production of antibody fragments, such as Fv, Fab, Fab' and F(ab')₂ fragments and other antibody fragments. These smaller molecules retain the antigen binding activity of whole antibodies and can also exhibit improved tissue penetration and pharmacokinetic properties in comparison to whole immunoglobulin molecules. Indeed, antibody fragments are proving to be versatile therapeutic agents, as seen by the recent success of products such as ReoPro® and Lucentis®. Whilst such fragments appear to exhibit a number of advantages over whole immunoglobulins, they also suffer from an increased rate of clearance from serum since they lack the Fc domain that imparts a long lifetime in vivo (Medasan et al, 1997, J. Immunol. 158:2211-2217). Antibodies with dual specificity, i.e. which bind to two different antigens have been previously described (for reviews, see Segal et al., 1999, Curr. Opin. Immunol. 1 1 :558-562; Plϋckthun & Pack, 1997, Immunotechnology, 3:83-105; Fischer and Leger, 2007, Pathobiology, 74, 3-14). Dual specificity antibodies are also described in WO02/02773, US2007065440, US2006257406, US2006106203 and US2006280734. Previous approaches to making hetero-bispecific antibody-based molecules have generally employed chemical cross-linking or protein engineering techniques. Chemical cross-linking suffers from poor yields of hetero- and homo- dimer formation and the requirement for their subsequent chromatographic separation. Protein engineering approaches have either been highly elaborate (e.g. knobs-into- holes engineering; Ridgway et al., 1996, Protein Eng. 9(7):617-621) or have used molecules with inappropriate stability characteristics (e.g. diabodies, scFv). In some cases bispecific antibodies can also suffer from steric hindrance problems such that both antigens cannot bind simultaneously to each antibody arm.

Single variable domain antibodies also known as single domain antibodies or dAbs, correspond to the variable regions of either the heavy (VH) or light (VL) chain of an antibody. Murine single-domain antibodies were described by Ward et al., 1989, Nature, 341, 544-546. Human and 'camelised' human single domain antibodies have also been described (Holt et al., 2003, Trends in Biotechnology, 21, 484-490). Single domain antibodies have also been obtained from the camelids (camels and llamas) and cartilaginous fish (wobbegong and nurse sharks). These organisms have evolved high affinity single V-like domains (called VhH in camelids and V-NAR in sharks), mounted on an Fc-equivalent constant domain framework as an integral and crucial component of their immune system (see Holliger & Hudson, for a review; 2005, Nature Biotechnology, 23(9): 1 126-1 136).

Single domain antibody-enzyme fusions have been described in EP0368684. Single domain-effector group fusions have also been described in WO2004/058820 which comprise a single variable domain. Dual variable domain immunoglobulins have been described in WO2007/024715. Dual specific ligands comprising two single domain antibodies with differing specificities have been described in EP1517921. Means to improve the half-life of antibody fragments, such as Fv, Fab, Fab',

F(ab')₂ and other antibody fragments, are known. One approach has been to conjugate the fragment to polymer molecules. Thus, the short circulating half-life of Fab', F(ab')₂ fragments in animals has been improved by conjugation to polyethylene glycol (PEG; see, for example, WO98/25791, WO99/64460 and WO98/37200). Another approach has been to modify the antibody fragment by conjugation to an agent that interacts with the FcRn receptor (see, for example, WO97/34631). Yet another approach to extend half-life has been to use polypeptides that bind serum albumin (see, for example, Smith et al., 2001, Bioconjugate Chem. 12:750-756; EP0486525; US6267964; WO04/001064; WO02/076489; and WO01/45746). However, there still remains a need to produce antigen-binding immunoglobulin proteins that have a long in vivo half-life, as an alternative to those that have a long half life because they interact with the FcRn receptor, without being chemically modified by conjugation to PEG, or being conjugated to human serum albumin.

A variety of proteins exist in plasma and include thyroxine-binding protein, transthyretin, αl-acid glycoprotein, transferrin, fibrinogen and albumin, or a fragment of any thereof. Serum carrier proteins circulate within the body with half-lives measured in days, for example, 5 days for thyroxine-binding protein or 2 days for transthyretin (Bartalena & Robbins, 1993, Clinics in Lab. Med. 13:583-598), or 65 hours in the second phase of turnover of iodinated αl-acid glycoprotein (Bree et al., 1986, Clin. Pharmacokin. 1 1 :336-342). Data from Gitlin et al. (1964, J. Clin. Invest. 10:1938-1951) suggest that in pregnant women, the half-life of αl-acid glycoprotein is 3.8 days, 12 days for transferrin and 2.5 days for fibrinogen. Serum albumin is an abundant protein in both vascular and extravascular compartments with a half-life in man of about 19 days (Peters, 1985, Adv Protein Chem. 37:161-245). This is similar to the half-life of IgGl, which is about 21 days (Waldeman & Strober, 1969, Progr. Allergy, 13: 1-1 10).

The present invention provides improved dual specificity antibody fusion proteins which can be produced recombinantly and are capable of binding two antigens simultaneously, in particular two distinct/different antigens. Thus, the present invention provides dual specificity antibody fusion proteins which comprise an immunoglobulin moiety, for example a Fab or Fab' fragment, with a first specificity for an antigen of interest, and further comprise a single domain antibody (dAb) with specificity for a second antigen of interest, in particular where the first antigen and second antigen are different entities.

Multivalent as employed herein is intended to refer to an entity that has two or more binding sites, for example two or three binding sites such as two binding sites. Each binding site may bind the same epitope or different epitopes on the same antigen, or may bind different (distinct) antigens.

The present invention also provides dual specificity antibody fusion proteins which comprise an immunoglobulin moiety, for example a Fab or Fab' fragment, with a first specificity for an antigen of interest, and further comprise at least one single domain antibody with specificity for a second antigen of interest.

A dual specificity antibody fusion of the invention will be capable of selectively binding to two antigens of interest.

In one embodiment the first and second antigen are the same antigen. In one embodiment, an antigen of interest bound by the Fab or Fab' fragment may be a cell-associated protein, for example a cell surface protein on cells such as bacterial cells, yeast cells, T-cells, endothelial cells or tumour cells, or it may be a soluble protein. Antigens of interest may also be any medically relevant protein such as those proteins upregulated during disease or infection, for example receptors and/or their corresponding ligands. Particular examples of cell surface proteins include adhesion molecules, for example integrins such as βl integrins e.g. VLA-4, E- selectin, P selectin or L-selectin, CD2, CD3, CD4, CD5, CD7, CD8, CDl Ia, CDl Ib, CDl 8, CDl 9, CD20, CD23, CD25, CD33, CD38, CD40, CD45, CDW52, CD69, CD134 (OX40), ICOS, BCMP7, CD137, CD27L, CDCPl, DPCRl, DPCRl, dudulin2, FLJ20584, FLJ40787, HEK2, KIAA0634, KIAA0659, KIAA 1246, KIAA1455, LTBP2, LTK, MAL2, MRP2, nectin-like2, NKCCl, PTK7, RAIGl, TCAMl, SC6, BCMPlOl, BCMP84, BCMPl 1, DTD, carcinoembryonic antigen (CEA), human milk fat globulin (HMFGl and 2), MHC Class I and MHC Class II antigens, and VEGF, and where appropriate, receptors thereof. Soluble antigens include interleukins such as IL-I, IL-2, IL-3, IL-4, IL-5, IL-6,

IL-8, IL-12, IL-16 or IL-17, viral antigens for example respiratory syncytial virus or cytomegalovirus antigens, immunoglobulins, such as IgE, interferons such as interferon α, interferon β or interferon γ, tumour necrosis factor-α, tumor necrosis factor-β, colony stimulating factors such as G-CSF or GM-CSF, and platelet derived growth factors such as PDGF-α, and PDGF-β and where appropriate receptors thereof. Other antigens include bacterial cell surface antigens, bacterial toxins, viruses such as influenza, EBV, HepA, B and C, bioterrorism agents, radionuclides and heavy metals, and snake and spider venoms and toxins.

In one embodiment, the antibody fusion protein of the invention may be used to functionally alter the activity of the antigen of interest. For example, the antibody fusion protein may neutralize, antagonize or agonise the activity of said antigen, directly or indirectly.

In one embodiment, a second antigen of interest bound by the single domain antibody or antibodies in the dual specificity antibody fusion proteins of the invention may be a cell-associated protein, for example a cell surface protein on cells such as bacterial cells, yeast cells, T-cells, endothelial cells or tumour cells, or it may be a soluble protein. Antigens of interest may also be any medically relevant protein such as those proteins upregulated during disease or infection, for example receptors and/or their corresponding ligands. Particular examples of cell surface proteins include adhesion molecules, for example integrins such as βl integrins e.g. VLA-4, E- selectin, P selectin or L-selectin, CD2, CD3, CD4, CD5, CD7, CD8, CDl Ia, CDl Ib, CD18, CD19, CD20, CD23, CD25, CD33, CD38, CD40, CD45, CDW52, CD69, CD134 (OX40), ICOS, BCMP7, CD137, CD27L, CDCPl, DPCRl, DPCRl, dudulin2, FLJ20584, FLJ40787, HEK2, KIAA0634, KIAA0659, KIAA1246, KIAA1455, LTBP2, LTK, MAL2, MRP2, nectin-like2, NKCCl, PTK7, RAIGl, TCAMl, SC6, BCMPlOl, BCMP84, BCMPl 1, DTD, carcinoembryonic antigen (CEA), human milk fat globulin (HMFGl and 2), MHC Class I and MHC Class II antigens, and VEGF, and where appropriate, receptors thereof.

Soluble antigens include interleukins such as IL-I, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL- 12, IL- 16 or IL- 17, viral antigens for example respiratory syncytial virus or cytomegalovirus antigens, immunoglobulins, such as IgE, interferons such as interferon α, interferon β or interferon γ, tumour necrosis factor-α, tumor necrosis factor-β, colony stimulating factors such as G-CSF or GM-CSF, and platelet derived growth factors such as PDGF-α, and PDGF-β and where appropriate receptors thereof. Other antigens include bacterial cell surface antigens, bacterial toxins, viruses such as influenza, EBV, HepA, B and C, bioterrorism agents, radionuclides and heavy metals, and snake and spider venoms and toxins.

Other antigens which may be bound by the single domain antibody or antibodies include serum carrier proteins, polypeptides which enable cell-mediated effector function recruitment and nuclide chelator proteins.

Thus, in one example the present invention provides dual specificity antibody fusion proteins which comprise an immunoglobulin moiety with a first specificity for an antigen of interest, and further comprise a single domain antibody with specificity for a second protein, the latter providing the ability to recruit effector functions, such as complement pathway activation and/or effector cell recruitment. Further, fusion proteins of the present invention may be used to chelate radionuclides by virtue of a single domain antibody which binds to a nuclide chelator protein. Such fusion proteins are of use in imaging or radionuclide targeting approaches to therapy.

Accordingly, in one example there is provided an isolated dual specificity antibody fusion protein comprising an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to at least one dAb which has specificity for a recruitment polypeptide, said dAb providing the ability to recruit cell- mediated effector function(s), directly or indirectly, by binding to said recruitment polypeptide.

The recruitment of effector function may be direct in that effector function is associated with a cell, said cell bearing a recruitment molecule on its surface. Indirect recruitment may occur when binding of a dAb to a recruitment molecule causes release of, for example, a factor which in turn may directly or indirectly recruit effector function, or may be via activation of a signalling pathway. Examples include TNFα, IL2, IL6, IL8, ILl 7, IFNγ, histamine, CIq, opsonin and other members of the classical and alternative complement activation cascades, such as C2, C4, C3- convertase, and C5 to C9.

As used herein, 'a recruitment polypeptide' includes a FcγR such as FcγRI, FcγRII and FcγRIII, a complement pathway protein such as, but without limitation, CIq and C3, a CD marker protein (Cluster of Differentiation marker) such as, but without limitation, CD68, CDl 15, CDl 6, CD80, CD83, CD86, CD56, CD64, CD3, CD4, CD8, CD28, CD45, CD 19, CD20 and CD22. Further recruitment polypeptides which are CD marker proteins include CDl, CDId, CD2, CD5, CD8, CD9, CDlO, CDl 1, CDl Ia, CDl Ib, CDl Ic, CD13, CD14, CD15, CD16, CD18, CD19, CD20, CD21, CD22, CD23, CD24, CD25, CD26, CD27, CD28, CD29, CD30, CD31, CD32, CD33, CD34, CD35, CD36, CD37, CD38, CD40, CD43, CD44, CD45, CD46, CD49, CD49a, CD49b, CD49c, CD49d, CD52, CD53, CD54, CD55, CD56, CD58, CD59, CD61, CD62, D62E, CD62L, CD62P, CD63, CD64, CD66e, CD68, CD70, CD71, CD72, CD79, CD80, CD81, CD82, CD83, CD84, CD85, CD86, CD88, CD89, CD90, CD94, CD95, CD98, CD 106, CD 1 14, CD 1 16, CD 1 17, CD 1 18, CD 120, CD 122, CD130, CD131, CD132, CD133, CD134, CD135, CD137, CD138, CD141, CD142, CD143, CD146, CD147, CD151, CD152, CD153, CD154, CD155, CD162, CD164, CD169, CD184, CD206, CD209, CD257, CD278, CD281, CD282, CD283 and CD304, or a fragment of any thereof which retains the ability to recruit cell-mediated effector function either directly or indirectly. A recruitment polypeptide also includes immunoglobulin molecules such as IgGl, IgG2, IgG3, IgG4, IgE and IgA which possess effector function.

In one embodiment, the second protein for which the dAb has specificity is a complement pathway protein, with CIq being particularly preferred.

In a preferred embodiment, the second protein for which the dAb has specificity is a CD marker protein, with CD68, CD80, CD86, CD64, CD3, CD4, CD8 CD45, CDl 6 and CD35 being particularly preferred.

Accordingly also provided is an isolated dual specificity antibody fusion protein comprising an antibody fragment with specificity for an antigen of interest, said fragment being fused to at least one dAb which has specificity for a CD molecule selected from the group consisting of CD68, CD80, CD86, CD64, CD3, CD4, CD8 CD45, CD16 and CD35. In one embodiment the single domain antibody or antibodies provide an extended half-life to the immunoglobulin moiety with the first specificity.

Accordingly, in one embodiment there is provided a dual specificity antibody fusion protein comprising an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to at least one single domain antibody which has specificity for a serum carrier protein, a circulating immunoglobulin molecule, or CD35/CR1, said single domain antibody providing an extended half-life to the antibody fragment with specificity for said antigen of interest by binding to said serum carrier protein, circulating immunoglobulin molecule or CD35/CR1. In one embodiment there is provided an isolated dual specificity antibody fusion protein comprising an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to at least one single domain antibody which has specificity for a serum carrier protein, a circulating immunoglobulin molecule, or CD35/CR1, said single domain antibody providing an extended half-life to the antibody fragment with specificity for said antigen of interest by binding to said serum carrier protein, circulating immunoglobulin molecule or CD35/CR1.

As used herein, 'serum carrier proteins' include thyroxine-binding protein, transthyretin, αl-acid glycoprotein, transferrin, fibrinogen and albumin, or a fragment of any thereof. As used herein, a 'circulating immunoglobulin molecule' includes IgGl, IgG2,

IgG3, IgG4, slgA, IgM and IgD, or a fragment of any thereof.

CD35/CR1 is a protein present on red blood cells which have a half life of 36 days (normal range of 28 to 47 days; Lanaro et al, 1971, Cancer, 28(3):658-661).

In a preferred embodiment, the second protein for which the dAb has specificity is a serum carrier protein, with a human serum carrier protein being particularly preferred. In a most preferred embodiment, the serum carrier protein is human serum albumin.

Accordingly provided is a dual specificity antibody fusion protein comprising an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to at least one single domain antibody which has specificity for human serum albumin.

In one embodiment the present invention provides an isolated dual specificity antibody fusion protein comprising an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to at least one single domain antibody which has specificity for human serum albumin.

In one embodiment, the antibody fragment with specificity for an antigen of interest is a Fab fragment. In another embodiment, the antibody fragment with specificity for an antigen of interest is a Fab' fragment.

Thus, in one most preferred embodiment, the antibody fusion proteins of the invention are translation fusion proteins, i.e. genetic fusions, the sequence of each of which is encoded by an expression vector. Alternatively, the antibody fusion protein components have been fused using chemical means, i.e. by chemical conjugation or chemical cross-linking. Such chemical means are known in the art.

In one example, the antibody fragments are Fab' fragments which possess a native or a modified hinge region. Where the antibody fragment for use in preparing a dual specificity antibody fusion protein of the invention is a Fab' fragment, said fragment is generally extended at the C-terminus of the heavy chain by one or more amino acids. Thus, an antibody fusion of the invention can comprise a Fab' fragment translation fused (or chemically fused) to a dAb, directly or via a linker. Further, examples of suitable antibody Fab' fragments include those described in WO2005003170 and WO2005003171.

In another example, the antibody fragments are Fab fragments. Thus, an antibody fusion of the invention can comprise a Fab fragment translation fused (or chemically fused) to a linker sequence which in turn is translation fused (or chemically fused) to a dAb. Preferably, the Fab fragment is a Fab fragment which terminates at the interchain cysteines, as described in WO2005/003169.

The antibody Fab or Fab' fragments of use in the present invention can be from any species but are preferably derived from a monoclonal antibody, a human antibody, or are humanised fragments. An antibody fragment for use in the present invention can be derived from any class (e.g. IgG, IgE, IgM, IgD or IgA) or subclass of immunoglobulin molecule and may be obtained from any species including for example mouse, rat, shark, rabbit, pig, hamster, camel, llama, goat or human.

In one embodiment, the antibody Fab or Fab' fragment is a monoclonal, fully human, humanized or chimeric antibody fragment. In one embodiment the antibody Fab or Fab' fragments are fully human or humanised. Monoclonal antibodies may be prepared by any method known in the art such as the hybridoma technique (Kohler & Milstein, Nature, 1975, 256, 495-497), the trioma technique, the human B-cell hybridoma technique (Kozbor et al, Immunology Today, 1983, 4, 72) and the EBV-hybridoma technique (Cole et al, "Monoclonal Antibodies and Cancer Therapy", pp. 77-96, Alan R. Liss, Inc., 1985). Antibodies for use in the invention may also be generated using single lymphocyte antibody methods by cloning and expressing immunoglobulin variable region cDNAs generated from single lymphocytes selected for the production of specific antibodies by, for example, the methods described by Babcook, J. et al., Proc. Natl. Acad. ScL USA, 1996, 93(15), 7843-7848, WO 92/02551 , WO2004/051268 and WO2004/106377.

Humanized antibodies are antibody molecules from non-human species having one or more complementarity determining regions (CDRs) from the non-human species and a framework region from a human immunoglobulin molecule (see, for example, US 5,585,089). The antibodies for use in the present invention can also be generated using various phage display methods known in the art and include those disclosed by Brinkman et al., J. Immunol. Methods, 1995, 182, 41-50; Ames et al., J. Immunol. Methods, 1995, 184, 177-186; Kettleborough et al. Eur. J. Immunol, 1994, 24, 952- 958; Persic et al., Gene, 1997 187, 9-18; and Burton et al., Advances in Immunology, 1994, 57, 191-280; WO 90/02809; WO 91/10737; WO 92/01047; WO 92/18619; WO 93/1 1236; WO 95/15982; and WO 95/20401 ; and US 5,698,426; 5,223,409; 5,403,484; 5,580,717; 5,427,908; 5,750,753; 5,821,047; 5,571,698; 5,427,908; 5,516,637; 5,780,225; 5,658,727; 5,733,743; and 5,969,108. Also, transgenic mice, or other organisms, including other mammals, may be used to generate humanized antibodies. Fully human antibodies are those antibodies in which the variable regions and the constant regions (where present) of both the heavy and the light chains are all of human origin, or substantially identical to sequences of human origin, not necessarily from the same antibody. Examples of fully human antibodies may include antibodies produced for example by the phage display methods described above and antibodies produced by mice in which the murine immunoglobulin variable and/or constant region genes have been replaced by their human counterparts eg. as described in general terms in EP0546073 Bl, US 5,545,806, US 5,569,825, US 5,625,126, US 5,633,425, US 5,661,016, US5,770,429, EP 0438474 Bl and EP0463151 Bl .

The antibody Fab or Fab' fragment starting material for use in the present invention may be obtained from any whole antibody, especially a whole monoclonal antibody, using any suitable enzymatic cleavage and/or digestion techniques, for example by treatment with pepsin. Alternatively, or in addition the antibody starting material may be prepared by the use of recombinant DNA techniques involving the manipulation and re-expression of DNA encoding antibody variable and/or constant regions. Standard molecular biology techniques may be used to modify, add or delete amino acids or domains as desired. Any alterations to the variable or constant regions are still encompassed by the terms 'variable' and 'constant' regions as used herein. The antibody fragment starting material may be obtained from any species including for example mouse, rat, rabbit, hamster, camel, llama, goat or human. Parts of the antibody fragment may be obtained from more than one species, for example the antibody fragments may be chimeric. In one example, the constant regions are from one species and the variable regions from another. The antibody fragment starting material may also be modified. In another example, the variable region of the antibody fragment has been created using recombinant DNA engineering techniques. Such engineered versions include those created for example from natural antibody variable regions by insertions, deletions or changes in or to the amino acid sequences of the natural antibodies. Particular examples of this type include those engineered variable region domains containing at least one CDR and, optionally, one or more framework amino acids from one antibody and the remainder of the variable region domain from a second antibody. The methods for creating and manufacturing these antibody fragments are well known in the art (see for example, Boss et al., US 4,816,397; Cabilly et al., US 6,331,415; Shrader et al., WO 92/02551 ; Ward et al., 1989, Nature, 341, 544; Orlandi et al., 1989, Proc.Natl.Acad.Sci. USA, 86, 3833; Riechmann et al., 1988, Nature, 322, 323; Bird et al, 1988, Science, 242, 423; Queen et al., US 5,585,089; Adair, WO91/09967; Mountain and Adair, 1992, Biotechnol. Genet. Eng. Rev, 10, 1-142; Verma et al., 1998, Journal of Immunological Methods, 216, 165-181).

In the present invention each single domain antibody fused to the Fab or Fab' fragment may linked directly or via a linker.

Linked directly are employed herein is intended to refer to the fact that the "last" amino acid of the Fab or Fab' is joined by a peptide bond to the "first" amino acid of the single domain antibody(or indeed vice versa)

Examples of suitable linker regions for linking a dAb to a Fab or Fab' include, but are not limited to, flexible linker sequences and rigid linker sequences. Flexible linker sequences include those disclosed in Huston ef α/.,1988, PNAS 85:5879-5883; Wright & Deonarain, MoI. Immunol., 2007, 44(11):2860-2869; Alfthan et al., Prot. Eng., 1995, 8(7):725-731 ; Lxxo et al, J. Biochem., 1995, 1 18(4):825-831 ; Tang et al., 1996, J. Biol. Chem. 271(26): 15682-15686; and Turner et al., 1997, JIMM 205, 42-54 (see Table 1 for representative examples).

Table 1. Flexible linker sequences

S) is optional in sequence3 and 45 to 48.

Examples of rigid linkers include the peptide sequences GAP AP AAP APA (SEQ ID NO:34), PPPP (SEQ ID NO:35) and PPP.

In one embodiment the peptide linker is an albumin binding peptide. Examples of albumin binding peptides are provided in WO 2007/106120 and include:

Table 2

In one embodiment, an antibody hinge sequence or part thereof is used as a linker, eg. the upper hinge sequence. Typically, antibody Fab' fragments for use in the present invention possess a native or a modified hinge region. Such hinge regions are used as a natural linker to the dAb moiety. The native hinge region is the hinge region normally associated with the C_HI domain of the antibody molecule. A modified hinge region is any hinge that differs in length and/or composition from the native hinge region. Such hinges can include hinge regions from any other species, such as human, mouse, rat, rabbit, hamster, camel, llama or goat hinge regions. Other modified hinge regions may comprise a complete hinge region derived from an antibody of a different class or subclass from that of the C_HI domain. Thus, for instance, a C_HI domain of class γl may be attached to a hinge region of class γ4. Alternatively, the modified hinge region may comprise part of a natural hinge or a repeating unit in which each unit in the repeat is derived from a natural hinge region. In a further alternative, the natural hinge region may be altered by converting one or more cysteine or other residues into neutral residues, such as alanine, or by converting suitably placed residues into cysteine residues. By such means the number of cysteine residues in the hinge region may be increased or decreased. In addition other characteristics of the hinge can be controlled, such as the distance of the hinge cysteine(s) from the light chain interchain cysteine, the distance between the cysteines of the hinge and the composition of other amino acids in the hinge that may affect properties of the hinge such as flexibility e.g. glycines may be incorporated into the hinge to increase rotational flexibility or prolines may be incorporated to reduce flexibility. Alternatively combinations of charged or hydrophobic residues may be incorporated into the hinge to confer multimerisation properties, see for example, Richter et al, 2001, Prot. Eng. 14(10):775-783 for use of charged or ionic tails, e.g., acidic tails as linkers and Kostelny et al., 1992, J. Immunol. 5(1):1547-1553 for leucine zipper sequences. Other modified hinge regions may be entirely synthetic and

RECTIFIED SHEET (RULE 91) ISA/EP may be designed to possess desired properties such as length, composition and flexibility.

A number of modified hinge regions have already been described for example, in US5,677,425, US6642356, WO9915549, WO2005003170, WO2005003169, WO2005003170, WO9825971 and WO2005003171 and these are incorporated herein by reference. Such hinges generally follow on from the CHl region, but may also be incorporated onto the end of constant region of a light chain kappa or lambda fragment; see Table 3 for examples. Table 3. Hin e linker se uences

Single variable domains also known as single domain antibodies or dAbs for use in the present invention can be generated using methods known in the art and include those disclosed in WO2005118642, Ward et al, 1989, Nature, 341, 544-546 and Holt et al., 2003, Trends in Biotechnology, 21, 484-490. In one embodiment a single domain antibody for use in present invention is a heavy chain variable domain (VH) or a light chain domain (VL). Each light chain domain may be either of the kappa or lambda subgroup. Methods for isolating VH and VL domains have been described in the art, see for example EP0368684 and Ward et al., supra. Such domains may be derived from any suitable species or antibody starting material. In one embodiment the single domain antibody may be derived from a rodent, a human or other species. In one embodiment the single domain antibody is humanised. In one embodiment the single domain antibody is derived from a phage display library, using the methods described in for example, WO2005/1 18642, Jespers et al., 2004, Nature Biotechnology, 22, 1 161 - 1 165 and Holt et al., 2003, Trends in Biotechnology, 21, 484-490. Preferably such single domain antibodies are fully human but may also be derived from other species. In one embodiment the single variable domain is chimeric in that the framework is human or substantially human in origin and the CDR(s) is/are of non-human origin. It will be appreciated that the sequence of the single domain antibody once isolated may be modified to improve the characteristics of the single domain antibody, for example solubility, as described in Holt et al., supra.

Substantially human as employed herein is intended to refer that the human character of the original material is retained, which may be relevant to immunogenicity. Substantially human material would include wherein one amino acid in the framework sequence is added deleted or replaced by another amino acid. In one embodiment the dAb is a human sequence obtained from scFv phage- display or from a transgenic Humouse™ or Velocimouse™ or a humanised rodent.

In one embodiment, the dAb is obtained from a human or humanised rodent, a camelid or a shark. Such a dAb will preferably be humanised. In one example the single domain antibody is a VHH domain based on camelid immunoglobulins as described in EP0656946. In one example, a camel or a llama is immunised with an antigen of interest and blood collected when the titre is appropriate. The gene encoding the dAb may be cloned by single cell PCR, or the B cell(s) encoding the dAb may be immortalised by EBV transformation, or by fusion to an immortal cell line.

As described herein above, the present invention provides dual specificity antibody fusion proteins comprising an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to at least one single domain antibody, directly or via a linker, which has specificity for a second antigen of interest.

Accordingly, in one embodiment, the antibody fragment, eg. Fab or Fab' fragment is fused at the N-terminus of the heavy or the light chain variable region to a dAb directly or via a linker. Alternatively, the antibody Fab or Fab' fragment is fused at the C-terminus of the heavy or light chain to a dAb directly or via a linker. In another embodiment the heavy and light chains of the antibody Fab or Fab' fragment are each fused at the C-terminus to a dAb directly or via a linker. The linkage can be a chemical conjugation but is most preferably a translation fusion, i.e. a genetic fusion where the sequence of each is encoded in sequence by an expression vector. Typically the N-terminus of the single domain antibody will be fused to the C- terminus of the heavy or light chain of the Fab or Fab' fragment, directly or via a linker, and where the single domain antibody is fused to the N-terminus of the Fab or Fab' it will be fused via its C-terminus, optionally via a linker.

In one embodiment the present invention provides a dual specificity antibody fusion protein comprising or consisting of an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to a single domain antibody at the N-terminus of the heavy or light chain which has specificity for a second antigen of interest.

In one embodiment the present invention provides a dual specificity antibody fusion protein comprising or consisting of an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to a single domain antibody at the C-terminus of the heavy or light chain which has specificity for a second antigen of interest.

In one embodiment the present invention provides a dual specificity antibody fusion protein comprising or consisting of an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to at least one single domain antibody at the C-terminus of the heavy or light chain which has specificity for a second antigen of interest.

In one embodiment the present invention provides a dual specificity antibody fusion protein comprising or consisting of an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to two single domain antibodies wherein each single domain antibody is fused in linear sequence to each other, optionally via a linker and the resulting single domain antibody fusion is fused to the C-terminus of the light chain or the heavy chain of the Fab or Fab' fragment. In one embodiment the present invention provides a dual specificity antibody fusion protein comprising or consisting of an antibody Fab or Fab' fragment with specificity for an antigen of interest, said fragment being fused to two single domain antibodies wherein one single domain antibody is fused to the C-terminus of the light chain of the Fab or Fab' fragment and the other single domain antibody is fused to the C-terminus of the heavy chain of the Fab or Fab' fragment, said single domain antibodies having specificity for a second antigen of interest.

In one embodiment where the heavy and light chains of the Fab or Fab' fragment each comprise a single domain antibody at the C-terminus the two single domain antibodies are identical i.e. have the same binding specificity for the same antigen. In one example, they bind the same epitope on the same antigen. For example the single domain antibodies may both be the same VH dAb, the same VHH dAb or the same VL dAb.

Preferably where the heavy and light chains of the Fab or Fab' fragment each comprise a single domain antibody at the C-terminus the two single domain antibodies are a complementary VH/VL pair which bind the antigen co-operatively i.e. they are a complementary VH/VL pair which have the same binding specificity. Typically they will be a VH/VL pair derived from the same antibody.

In one embodiment, where the dual specificity antibody fusion protein of the present invention comprises two single domain antibodies which are a complementary VH/VL pair, the VH single domain antibody is fused to the C-terminus of the heavy chain constant region (CHl) and the VL single domain antibody is fused to the C- terminus of the light chain constant region (C kappa or C lambda). In one embodiment, where the dual specificity antibody fusion protein of the present invention comprises two single domain antibodies which are a complementary VH/VL pair, the VL single domain antibody is fused to the C-terminus of the heavy chain constant region (CHl) and the VH single domain antibody is fused to the C- terminus of the light chain constant region (C kappa or C lambda). In one embodiment, where the dual specificity antibody fusion protein of the present invention comprises two single domain antibodies which are linked by one or more disulfide bonds for example two single domain antibodies which are a complementary VH/VL pair linked by one ore more (such as 1 or 2) disulfide bonds, such as the VH single domain antibody is fused to the C-terminus of the heavy chain constant region (CHl) and the VL single domain antibody is fused to the C-terminus of the light chain constant region (C kappa or C lambda). Alternatively the VL single domain antibody is fused to the C-terminus of the heavy chain constant region (CHl) and the VH single domain antibody is fused to the C-terminus of the light chain constant region (C kappa or C lambda).

The disulfide bond is thought to provide additional stabilisation to the construct, which may be advantageous.

In one or more embodiments the disulfide bond between the heavy and light chain such as between the CH domain and CL or CK domain is not present, for example because one or more cysteines which form the bond are replaced. Said one or more cysteines may be replaced with, for example serine.

In one or more embodiments an interchain disulfide bond between the heavy and light chain between the CH domain and CL or CK domain is present.

In one embodiment there is provided a F(ab)₂ fragment comprising one, two, three or four single domain antibodys, for example a two separate VH/VL pairs which may be directed to the same or different antigens.

In dual specificity fusion proteins of the present invention the single domain antibody or antibodies bind to a second antigen, different from that bound by the Fab or Fab' fragment component. In one example the dAbs for use in the present invention exhibit specificity for a complement pathway protein, a CD marker protein or an FcγR. In this case the dAb is preferably specific for a CD molecule. Most preferably, the dAb exhibits specificity for a CD molecule selected from the group consisting of CD68, CD80, CD86, CD64, CD3, CD4, CD8 CD45, CDl 6 and CD35. In a preferred example the dAbs for use in the present invention exhibit specificity for a serum carrier protein, a circulating immunoglobulin molecule, or CD35/CR1, the serum carrier protein preferably being a human serum carrier protein such as thyroxine-binding protein, transthyretin, αl-acid glycoprotein, transferrin, fibrinogen or serum albumin. Most preferably, the dAb exhibits specificity for human serum albumin. Thus, in one example, a rabbit, mouse, rat, camel or a llama is immunised with a serum carrier protein, a circulating immunoglobulin molecule, or CD35/CR1 (e.g. human serum albumin) and blood collected when the titre is appropriate. The gene encoding the dAb may be cloned by single cell PCR, or the B cell(s) encoding the dAb may be immortalised by EBV transformation, or by fusion to an immortal cell line. Alternatively the single domain antibody may be obtained by phage display as described herein above. In one embodiment the single domain antibody or antibodies bind human serum albumin. In one embodiment the single domain antibody or antibodies bind human serum albumin, murine serum albumin and rat serum albumin.

In one embodiment the single domain antibody which binds serum albumin is a dAb provided in WO2005/118642 (see for example figures 1 c and 1 d) or a VHH provided in WO2004/041862 or a humanised nanobody described in, for example table III of WO2006/122787.

In one embodiment a single domain antibody which binds human serum albumin for use in the present invention is a heavy chain VH single domain antibody which comprises at least one of a CDR having the sequence given in Figure 5 (e) SEQ ID NO:56 or Figure 5 (k) SEQ ID NO:62 for CDR-Hl, a CDR having the sequence given in Figure 5(f) SEQ ID NO:57 or Figure 5 (1) SEQ ID NO:63 for CDR-H2 and a CDR having the sequence given in Figure 5 (g) SEQ ID NO:58 or Figure 5 (m) SEQ ID NO:64 for CDR-H3. In another embodiment a single domain antibody which binds human serum albumin for use in the present invention is a heavy chain VH antibody, wherein at least two of CDR-Hl, CDR-H2 and CDR-H3 of the VH domain are selected from the following: the sequence given in SEQ ID NO:56 or SEQ ID NO:62 for CDR-Hl, the sequence given in SEQ ID NO:57 or SEQ ID NO:63 for CDR-H2 and the sequence given in SEQ ID NO:58 or SEQ ID NO:64 for CDR-H3. For example, the single domain antibody may comprise a VH domain wherein CDR-H 1 has the sequence given in SEQ ID NO:56 and CDR-H2 has the sequence given in SEQ ID NO:57. Alternatively, the single domain antibody may comprise a VH domain wherein CDR- Hl has the sequence given in SEQ ID NO: 56 and CDR-H3 has the sequence given in SEQ ID NO:58. For the avoidance of doubt, it is understood that all permutations are included.

In another embodiment a single domain antibody which binds human serum albumin for use in the present invention is a heavy chain VH single domain antibody, wherein the VH domain comprises the sequence given in SEQ ID NO: 56 for CDR- Hl, the sequence given in SEQ ID NO:57 for CDR-H2 and the sequence given in SEQ ID NO:58 for CDR-H3.

In another embodiment a single domain antibody which binds human serum albumin for use in the present invention is a heavy chain VH single domain antibody, wherein the VH domain comprises the sequence given in SEQ ID NO:62 for CDR- Hl, the sequence given in SEQ ID NO:63 for CDR-H2 and the sequence given in SEQ ID NO:64 for CDR-H3.

In one embodiment a single domain antibody which binds human serum albumin for use in the present invention is a humanised heavy chain VH single domain antibody, dAbHl, having the sequence given in Figure 5 (a) (SEQ ID NO:52). An example of a suitable CHl -dAbHl fusion comprising a G₄S linker is given in Figure 6 (SEQ ID NO:68). In one embodiment the single domain antibody which binds human serum albumin for use in the present invention is a humanised heavy chain VH single domain antibody, dAbH2, having the sequence given in Figure 5 (c) (SEQ ID NO:54). An example of a suitable CHl-dAbH2 fusion comprising a G₄S linker is given in Figure 6 (SEQ ID NO:69).

The residues in antibody variable domains are conventionally numbered according to a system devised by Kabat et al. This system is set forth in Kabat et al, 1987, in Sequences of Proteins of Immunological Interest, US Department of Health and Human Services, NIH, USA (hereafter "Kabat et al. (supra)"). This numbering system is used in the present specification except where otherwise indicated.

The Kabat residue designations do not always correspond directly with the linear numbering of the amino acid residues. The actual linear amino acid sequence may contain fewer or additional amino acids than in the strict Kabat numbering corresponding to a shortening of, or insertion into, a structural component, whether framework or complementarity determining region (CDR), of the basic variable domain structure. The correct Kabat numbering of residues may be determined for a given antibody by alignment of residues of homology in the sequence of the antibody with a "standard" Kabat numbered sequence.

The CDRs of the heavy chain variable domain are located at residues 31-35 (CDR-Hl ), residues 50-65 (CDR-H2) and residues 95-102 (CDR-H3) according to the Kabat numbering system. However, according to Chothia (Chothia, C. and Lesk, A.M. J. MoI. Biol., 196, 901-917 (1987)), the loop equivalent to CDR-Hl extends from residue 26 to residue 32. Thus 'CDR-Hl ', as used herein, comprises residues 26 to 35, as described by a combination of the Kabat numbering system and Chothia's topological loop definition.

The CDRs of the light chain variable domain are located at residues 24-34 (CDR-Ll), residues 50-56 (CDR-L2) and residues 89-97 (CDR-L3) according to the Kabat numbering system.

In one embodiment a single domain antibody which binds human serum albumin for use in the present invention is a light chain VL single domain antibody which comprises at least one of a CDR having the sequence given in Figure 5 (h) SEQ ID NO:59 or Figure 5 (n) SEQ ID NO:65 for CDR-Ll, a CDR having the sequence given in Figure 5(i) SEQ ID NO:60 or Figure 5 (o) SEQ ID NO:66 for CDR-L2 and a CDR having the sequence given in Figure 5 (j) SEQ ID NO:61 or Figure 5 (p) SEQ ID NO:67 for CDR-L3.

In another embodiment a single domain antibody which binds human serum albumin for use in the present invention is a light chain VL antibody, wherein at least two of CDR-Ll, CDR-L2 and CDR-L3 of the VL domain are selected from the following: the sequence given in SEQ ID NO:59 or SEQ ID NO:65 for CDR-Ll , the sequence given in SEQ ID NO:60 or SEQ ID NO:66 for CDR-L2 and the sequence given in SEQ ID NO:61 or SEQ ID NO:67 for CDR-L3. For example, the domain antibody may comprise a VL domain wherein CDR-Ll has the sequence given in SEQ ID NO:59 and CDR-L2 has the sequence given in SEQ ID NO:60. Alternatively, the domain antibody may comprise a VL domain wherein CDR-Ll has the sequence given in SEQ ID NO:59 and CDR-L3 has the sequence given in SEQ ID NO:61. For the avoidance of doubt, it is understood that all permutations are included.

In another embodiment a single domain antibody which binds human serum albumin for use in the present invention is a light chain VL domain antibody, wherein the VL domain comprises the sequence given in SEQ ID NO:59 for CDR-Ll, the sequence given in SEQ ID NO:60 for CDR-L2 and the sequence given in SEQ ID NO:61 for CDR-L3.

In another embodiment a single domain antibody which binds human serum albumin for use in the present invention is a light chain VL domain antibody, wherein the VL domain comprises the sequence given in SEQ ID NO:65 for CDR-Ll, the sequence given in SEQ ID NO:66 for CDR-L2 and the sequence given in SEQ ID NO:67 for CDR-L3.

In one embodiment a single domain antibody which binds human serum albumin for use in the present invention is a humanised light chain VL single domain antibody, dAbLl, having the sequence given in Figure 5 (b) (SEQ ID NO:53). An example of a suitable CHl-dAbLl fusion and a Ckl-dAbLl fusion both comprising a G₄S linker is given in Figure 6 (SEQ ID NO:70 and SEQ ID NO:72).

In one embodiment a single domain antibody which binds human serum albumin for use in the present invention is a humanised light chain VL single domain antibody, dAbL2, having the sequence given in Figure 5 (d) (SEQ ID NO:55). An example of a suitable CHl-dAbL2 fusion and a Ckl-dAbL2 fusion both comprising a G₄S linker is given in Figure 6 (SEQ ID NO:71 and SEQ ID NO:73).

In one embodiment where the heavy and light chains of the Fab or Fab' fragment each comprise a single domain antibody at the C-terminus and the two single domain antibodies are a complementary VH/VL pair which bind the antigen co-operatively as described herein above, the VH dAb is dAbHl (SEQ ID NO:52) and the VL dAb is dAbLl (SEQ ID NO:53).

In one embodiment where the heavy and light chains of the Fab or Fab' fragment each comprise a single domain antibody at the C-terminus the two single domain antibodies are a complementary VH/VL pair which bind the antigen co- operatively as described herein above, the VH dAb is dAbH2 (SEQ ID NO:54) and the VL dAb is dAbL2 (SEQ ID NO:55).

In another aspect, the present invention provides albumin binding antibodies or fragments thereof containing one or more of the CDRs provided herein above and in Figure 5 (e-p), in particular comprising a CDRHl with the sequence shown in SED ID NO. 56, a CDRH2 with the sequence shown in SED ID NO. 57, a CDRH3 with the sequence shown in SED ID NO. 58, a CDRLl with the sequence shown in SED ID NO. 59, a CDRL2 with the sequence shown in SED ID NO. 60, and/or a CDRL3 with the sequence shown in SED ID NO. 61. In one embodiment the albumin binding antibodies or fragments comprise a CDRHl with the sequence shown in SED ID NO. 62, a CDRH2 with the sequence shown in SED ID NO. 63, a CDRH3 with the sequence shown in SED ID NO. 64, a CDRLl with the sequence shown in SED ID NO. 65, a CDRL2 with the sequence shown in SED ID NO. 66, and/or a CDRL3 with the sequence shown in SED ID NO. 67. Said CDRs may be incorporated into any suitable antibody framework and into any suitable antibody format. Such antibodies include whole antibodies and functionally active fragments or derivatives thereof which may be, but are not limited to, monoclonal, humanised, fully human or chimeric antibodies. Accordingly, such albumin binding antibodies may comprise a complete antibody molecule having full length heavy and light chains or a fragment thereof and may be, but are not limited to Fab, modified Fab, Fab', F(ab')₂, Fv, single domain antibodies, scFv, bi, tri or tetra-valent antibodies, Bis-scFv, diabodies, triabodies, tetrabodies and epitope-binding fragments of any of the above (see for example Holliger and Hudson, 2005, Nature Biotech. 23(9): 1126-1136; Adair and Lawson, 2005, Drug Design Reviews - Online 2(3), 209-217). The methods for creating and manufacturing these antibody fragments are well known in the art (see for example Verma et al., 1998, Journal of Immunological Methods, 216, 165-181). Multi-valent antibodies may comprise multiple specificities or may be monospecific (see for example WO 92/22853 and WO05/113605). It will be appreciated that this aspect of the invention also extends to variants of these albumin binding antibodies.

It will be appreciated that such albumin binding antibodies, in particular single domain antibodies may be conjugated to any other antibody or protein or other molecule, as desired or used in any other suitable context. In one example the single domain antibodies dAbHl, dAbLl, dAbH2, dAbL2 as described above and shown in Figure 5 (a-d) may be incorporated into any suitable antibody format or used as single domain antibodies in any suitable context, such as a fusion or conjugate.

In one embodiment antibodies of this aspect of the invention comprise the sequence given in Figure 5(e) for CDR-Hl, the sequence given in Figure 5(f) for CDR-H2 and the sequence given in Figure 5(g) for CDR-H3.

In one embodiment antibodies of this aspect of the invention comprise the sequence given in Figure 5(k) for CDR-Hl, the sequence given in Figure 5(1) for CDR-H2 and the sequence given in Figure 5(m) for CDR-H3. In one embodiment antibodies of this aspect of the invention comprise the sequence given in Figure 5(h) for CDR-Ll, the sequence given in Figure 5(i) for CDR-L2 and the sequence given in Figure 5(j) for CDR-L3.

In one embodiment antibodies of this aspect of the invention comprise the sequence given in Figure 5(n) for CDR-Ll, the sequence given in Figure 5(o) for CDR-L2 and the sequence given in Figure 5(p) for CDR-L3. In the antibody formats below each of the sequences from the sequence listing herein may be located in the position corresponding to the natural position or a non- natural position. Natural position will be for the relevant sequence in the listing labelled CDRHl position Hl, for the relevant sequence in the listing labelled CDRH2 position H2, for the relevant sequence in the listing labelled CDRH3 position H3, for the relevant sequence in the listing labelled CDRLl position Ll, for the relevant sequence in the listing labelled CDRL2 position L2, and for the relevant sequence in the listing labelled CDRL3 position L3. Combinations thereof are also envisaged such as Hl and H2, Hl and H3, Hl and Ll, Hl and L2, Hl and L3, H2 and Ll, H2 and L2, H2 and L3, H2 and H3, H3 and Ll, H3 and L2, H3 and L3, Hl and H2 and H3, Hl and H2 and Ll, Hl and H2 and L2, Hl and H2 and L3, H2 and H3 and Ll , H2 and H3 and L2, H2 and H3 and L3, H3 and Ll and L2, H3 and Ll and L3, H3 and L2 and L3, Ll and L2 and L3, Hl and H2 and H3 and Ll , Hl and H2 and H3 and L2, Hl and H2 and H3 and L3, H2 and H3 and Ll and L2, H2 and H3 and Ll and L3, and H2 and H3 and L2 and L3, H3 and Ll and L2 and L3, Hl and H2 and H3 and Ll and L2, Hl and H2 and H3 and L2 and L3, Hl and H2 and H3 and Ll and L3, Ll and L2 and L3 and Hl and H2, Ll and L2 and L3 and H l and H3, L l and L2 and L3 and H2 and H3, Hl and H2 and H3 and Ll and L2 and L3.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1, 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 88 to 93.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 94to 99. In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1, 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 100 to 105.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 106 to 1 1 1.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 1 12 to 1 17.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 1 18 to 123.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 124 to 129. In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 130 to 135.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 136 to 141.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 142 to 147. In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 148 to 153.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1, 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 154 to 159.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 160 to 165.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 166 to 171.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1, 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 172 to 177. In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 178 to 183.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 184 to 189.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 190 to 195.

In one embodiment the antibody fusion protein of the disclosure comprises a sequence, for example 1 , 2, 3, 4, 5 or 6 sequence(s) selected from Sequence ID NO: 196 to 201.

In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID No: 202.

In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID No: 203. In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID Nos: 202 and 203.

In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID No: 204. In one embodiment the antibody fusion protein of the disclosure comprises

Sequence ID No: 205.

In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID Nos: 204 and 205.

In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID No: 206.

In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID No: 207.

In one embodiment the antibody fusion protein of the disclosure comprises Sequence ID No: 206 and 207. Where the single domain antibody or antibodies of the dual specificity fusion protein of the present invention bind to albumin the binding affinity of the single domain antibody for albumin will be sufficient to extend the half-life of the Fab or Fab' in vivo. It has been reported that an affinity for albumin of less than or equal to 2.5 μM affinity will extend half-life in vivo (Nguyen, A. et al (2006) Protein Engineering, Design & Selection, 19(7), 291-297). The single domain antibody molecules of the present invention preferably have a binding affinity suited to their purpose and the antigen to which they bind. In one example the single domain antibodies have a high binding affinity, for example picomolar. In one example the single domain antibodies have a binding affinity for antigen which is nanomolar or micromolar. Affinity may be measured using any suitable method known in the art, including BIAcore as described in the Examples herein using natural or recombinant antigen.

Preferably the single domain antibody molecules of the present invention which bind albumin have a binding affinity of about 2μM or better. In one embodiment the single domain antibody molecule of the present invention has a binding affinity of about 1 μM or better. In one embodiment the single domain antibody molecule of the present invention has a binding affinity of about 50OnM or better. In one embodiment the single domain antibody molecule of the present invention has a binding affinity of about 20OnM or better. In one embodiment the domain antibody molecule of the present invention has a binding affinity of about InM or better. It will be appreciated that the affinity of single domain antibodies provided by the present invention and known in the art may be altered using any suitable method known in the art. The present invention therefore also relates to variants of the domain antibody molecules of the present invention, which have an improved affinity for albumin. Such variants can be obtained by a number of affinity maturation protocols including mutating the CDRs (Yang et al, J. MoI. Biol., 254, 392-403, 1995), chain shuffling (Marks et al, Bio/Technology, K), 779-783, 1992), use of mutator strains of E. coli (Low et al, J. MoI. Biol., 250, 359-368, 1996), DNA shuffling (Patten et al., Curr. Opin. Biotechnol., 8, 724-733, 1997), phage display (Thompson et al, J. MoI. Biol., 256, 77-88, 1996) and sexual PCR (Crameri et al, Nature, 391., 288-291 , 1998). Vaughan et al {supra) discusses these methods of affinity maturation.

The single domain antibody or antibodies of the dual specificity fusion protein may be provided as monomers, dimmers or trimers, as required. The desired product may be obtained by adjusting the downstream processing steps the material is subjected to. In one embodiment the processed material is provided as a substantially homogenous monomer. In one embodiment the processed material is provided a substantially homogenous dimer. In one embodiment the processed material is provided as a substantially homogenous trimer.

The present invention also provides an isolated DNA sequence encoding a dual specificity antibody fusion protein of the present invention. The DNA sequences of the present invention may comprise synthetic DNA, for instance produced by chemical processing, cDNA, genomic DNA or any combination thereof.

DNA sequences which encode the dual specificity antibody fusion protein of the present invention can be obtained by methods well known to those skilled in the art. For example, DNA sequences coding for part or all of the antibody fragments, linkers and/or dAbs may be synthesised as desired from the determined DNA sequences or on the basis of the corresponding amino acid sequences.

Standard techniques of molecular biology may be used to prepare DNA sequences coding for the dual specificity antibody fusion protein of the present invention. Desired DNA sequences may be synthesised completely or in part using oligonucleotide synthesis techniques. Site-directed mutagenesis and polymerase chain reaction (PCR) techniques may be used as appropriate.

The present invention further relates to a cloning or expression vector comprising one or more DNA sequences of the present invention. Accordingly, provided is a cloning or expression vector comprising one or more DNA sequences encoding a dual specificity antibody fusion protein of the present invention. In one preferred embodiment, the cloning or expression vector comprises a single DNA sequence encoding the entire dual specificity antibody fusion protein. Thus, the cloning or expression vector comprises DNA encoded transcription units in sequence such that a translation fusion protein is produced.

Indeed, it will be understood by those skilled in the art that a fusion protein of the invention can have the dAb at the N-terminus or the C-terminus and thus, the dAb DNA encoded transcription unit will be first or last, respectively, within the DNA sequence encoding the translation fusion. Thus, a translation fusion may comprise an N-terminal dAb and a C-terminal Fab or Fab'. Further, a translation fusion may comprise an N-terminal Fab or Fab' and a C-terminal dAb. Figure 20 646Fv

CDRHl GIDLSNY AIN (SEQ ID NO: 222) CDRH2 IIWASGTTFYATWAKG (SEQ ID NO: 223) CDRH3 TVPGYSTAPYFDL (SEQ ID NO: 90) CDRLl QSSPSVWSDFLS (SEQ ID NO: 91) CDRL2 GASTLAS (SEQ ID NO: 92) CDRL3 GGGYSSISD TT (SEQ ID NO: 93)

647Fv

CDRHl GFTLSNNYWMC (SEQ ID NO: 94) CDRH2 CIYTGDGDTAYTSWAKG (SEQ ID NO:95) CDRH3 SGGSYYD YVFIL (SEQ ID NO: 96) CDRLl QASQSLGNRLA (SEQ ID NO: 97) CDRL2 RASTLAS (SEQ ID NO: 98) CDRL3 QCTYIGSKMGA (SEQ ID NO: 99)

648Fv is the same as a didAb of dAbH2, dAbL2

649Fv

CDRHl GFSFSGNYWIC (SEQ ID NO: 100) CDRH2 CIFTADGDTAYTSWAKG (SEQ ID NO: 101) CDRH3 SGGSAFDYVFIL (SEQ ID NO: 102) CDRLl QASQSIG NRLG (SEQ ID NO: 103) CDRL2 RASTLES (SEQ ID NO: 104) CDRL3 QCTYIGKLMGA (SEQ ED NO: 105)

645HeavyI50AFv

CDRH 1 GIDLSNYAIN (SEQ ID NO: 106)

CDRH2 AIWASGTTFYATWAKG (SEQ ID NO: 107)

CDRH3 TVPGYSTAPYFDL (SEQ ID NO : 108)

CDRLl QSSPSVWSNFLS (SEQ ID NO: 109)

CDRL2 EASKLTS (SEQ ID NO: 110)

CDRL3 GGGYSSISDTT (SEQ ID NO: 111)

RECTIFIED SHEET (RULE 91) ISA/EP used. Suitable mammalian host cells include NSO, CHO, myeloma or hybridoma cells. Accordingly in one embodiment the fusion protein of the present invention is expressed in E.coli. In another embodiment the fusion protein of the present invention is expressed in mammalian cells. The present invention also provides a process for the production of a dual specificity antibody fusion protein comprising culturing a host cell comprising a vector of the present invention under conditions suitable for the expression of protein from the DNA sequence encoding said dual specificity antibody fusion protein. The invention further provides methods for isolating the dual specificity antibody fusion protein.

On production, a dual specificity antibody fusion protein of the present invention may be purified, where necessary, using any suitable method known in the art. For example, but without limitation, chromatographic techniques such as ion exchange, size exclusion, protein G or hydrophobic interaction chromatography may be used.

The size of a dual specificity antibody fusion protein may be confirmed by conventional methods known in the art such as size exclusion chromatography and non-reducing SDS-PAGE. Such techniques can be used, for example to confirm that the protein has not dimerised and/or does not have a portion missing, e.g. the dAb portion. If dimers are detected and a homogenous monomeric product is required then the monomeric dual specificity antibody fusion protein may be purified away from the dimeric species using conventional chromatography techniques as described above.

Dual specificity antibody fusion proteins of the invention are useful in the treatment of diseases or disorders including inflammatory diseases and disorders, immune disease and disorders, fibrotic disorders and cancers.

The term "inflammatory disease" or "disorder" and "immune disease or disorder" includes rheumatoid arthritis, psoriatic arthritis, still's disease, Muckle Wells disease, psoriasis, Crohn's disease, ulcerative colitis, SLE (Systemic Lupus Erythematosus), asthma, allergic rhinitis, atopic dermatitis, multiple sclerosis, vasculitis, Type I diabetes mellitus, transplantation and graft-versus-host disease. The term "fibrotic disorder" includes idiopathic pulmonary fibrosis (IPF), systemic sclerosis (or scleroderma), kidney fibrosis, diabetic nephropathy, IgA nephropathy, hypertension, end-stage renal disease, peritoneal fibrosis (continuous ambulatory peritoneal dialysis), liver cirrhosis, age-related macular degeneration (ARMD), retinopathy, cardiac reactive fibrosis, scarring, keloids, burns, skin ulcers, angioplasty, coronary bypass surgery, arthroplasty and cataract surgery.

The term "cancer" includes a malignant new growth that arises from epithelium, found in skin or, more commonly, the lining of body organs, for example: breast, ovary, prostate, lung, kidney, pancreas, stomach, bladder or bowel. Cancers tend to infiltrate into adjacent tissue and spread (metastasise) to distant organs, for example: to bone, liver, lung or the brain.

Thus, according to a further aspect of the invention, there is provided a pharmaceutical composition which comprises an antibody fusion of the invention in association with one or more pharmaceutically acceptable carriers, excipients or diluents. Also provided is the use of an antibody fusion protein of the invention for the manufacture of a medicament for the treatment of a disease or disorder. Most preferably, the disease or disorder is an inflammatory disease or disorder.

Pharmaceutical compositions according to the invention may take a form suitable for oral, buccal, parenteral, subcutaneous, nasal, topical, ophthalmic or rectal administration, or a form suitable for administration by inhalation or insufflation.

Where appropriate, for example if the single domain antibody or antibodies of the antibody fusion protein bind to albumin, it may be desirable to pre-formulate the dual specificity fusion protein with human or recombinant serum albumin, using any suitable method known in the art.

Where the pharmaceutical formulation is a liquid, for example a solution or suspension then the formulation may further comprise albumin, for example human serum albumin, in particular recombinant albumin such as recombinant human serum albumin. Suitable amounts may be in the range of less than 2% w/w of the total formulation, in particular less than 1, 0.5, or 0.1% w/w. This may assist in stabilizing the antibody component in the formulation. The pharmaceutical composition may be lyophilized for reconstitution later, with an aqueous solvent.

In one embodiment there is provided a unit dose container, such as a vial, comprising a lyophilized "antibody" according to the invention. For oral administration, the pharmaceutical compositions may take the form of, for example, tablets, lozenges or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methyl cellulose); fillers (e.g. lactose, microcrystalline cellulose or calcium hydrogenphosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium glycollate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents, emulsifying agents, non-aqueous vehicles or preservatives. The preparations may also contain buffer salts, flavouring agents, colouring agents or sweetening agents, as appropriate. Preparations for oral administration may be suitably formulated to give controlled release of the active compound. For buccal administration, the compositions may take the form of tablets or lozenges formulated in conventional manner.

The bispecific antibodies of the invention may be formulated for parenteral administration by injection, e.g. by bolus injection or infusion. Formulations for injection may be presented in unit dosage form, e.g. in glass ampoules or multi-dose containers, e.g. glass vials. The compositions for injection may take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising, preserving and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile pyrogen-free water, before use.

In addition to the formulations described above, the bispecific antibodies of the invention may also be formulated as a depot preparation. Such long-acting formulations may be administered by implantation or by intramuscular injection. For nasal administration or administration by inhalation, the compounds according to the present invention may be conveniently delivered in the form of an aerosol spray presentation for pressurised packs or a nebuliser, with the use of a suitable propellant, e.g. dichlorodifluoromethane, fluorotrichloromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas or mixture of gases.

The compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack or dispensing device may be accompanied by instructions for administration.

For topical administration the compounds according to the present invention may be conveniently formulated in a suitable ointment containing the active component suspended or dissolved in one or more pharmaceutically acceptable carriers. Particular carriers include, for example, mineral oil, liquid petroleum, propylene glycol, polyoxyethylene, polyoxypropylene, emulsifying wax and water. Alternatively, the compounds according to the present invention may be formulated in a suitable lotion containing the active component suspended or dissolved in one or more pharmaceutically acceptable carriers. Particular carriers include, for example, mineral oil, sorbitan monostearate, polysorbate 60, cetyl esters wax, cetearyl alcohol, benzyl alcohol, 2-octyldodecanol and water.

In one embodiment the formulation is provided as a formulation for topical administrations including inhalation. Suitable inhalable preparations include inhalable powders, metering aerosols containing propellant gases or inhalable solutions free from propellant gases. Inhalable powders according to the disclosure containing the active substance may consist solely of the abovementioned active substances or of a mixture of the abovementioned active substances with physiologically acceptable excipient. These inhalable powders may include monosaccharides (e.g. glucose or arabinose), disaccharides (e.g. lactose, saccharose, maltose), oligo- and polysaccharides (e.g. dextranes), polyalcohols (e.g. sorbitol, mannitol, xylitol), salts (e.g. sodium chloride, calcium carbonate) or mixtures of these with one another. Mono- or disaccharides are suitably used, the use of lactose or glucose, particularly but not exclusively in the form of their hydrates. Particles for deposition in the lung require a particle size less than 10 microns, such as 1-9 microns for example from 0.1 to 5 μm, in particular from 1 to 5 μm. The particle size of the active ingredient (such as the antibody or fragment) is of primary importance.

The propellent gases which can be used to prepare the inhalable aerosols are known in the art. Suitable propellent gases are selected from among hydrocarbons such as n-propane, n-butane or isobutane and halohydrocarbons such as chlorinated and/or fluorinated derivatives of methane, ethane, propane, butane, cyclopropane or cyclobutane. The abovementioned propellent gases may be used on their own or in mixtures thereof. Particularly suitable propellent gases are halogenated alkane derivatives selected from among TG 1 1, TG 12, TG 134a and TG227. Of the abovementioned halogenated hydrocarbons, TG 134a (1,1,1,2-tetrafluoroethane) and TG227 (1,1,1,2,3,3,3-heptafluoropropane) and mixtures thereof are particularly suitable. The propellent-gas-containing inhalable aerosols may also contain other ingredients such as cosolvents, stabilisers, surface-active agents (surfactants), antioxidants, lubricants and means for adjusting the pH. All these ingredients are known in the art.

The propellant-gas-containing inhalable aerosols according to the invention may contain up to 5 % by weight of active substance. Aerosols according to the invention contain, for example, 0.002 to 5 % by weight, 0.01 to 3 % by weight, 0.015 to 2 % by weight, 0.1 to 2 % by weight, 0.5 to 2 % by weight or 0.5 to 1 % by weight of active ingredient.

Alternatively topical administrations to the lung may also be by administration of a liquid solution or suspension formulation, for example employing a device such as a nebulizer, for example, a nebulizer connected to a compressor (e.g., the Pari LC- Jet Plus(R) nebulizer connected to a Pari Master(R) compressor manufactured by Pari Respiratory Equipment, Inc., Richmond, Va.).

The antibody formats of the invention can be delivered dispersed in a solvent, e.g., in the form of a solution or a suspension. It can be suspended in an appropriate physiological solution, e.g., saline or other pharmacologically acceptable solvent or a buffered solution. Buffered solutions known in the art may contain 0.05 mg to 0.15 mg disodium edetate, 8.0 mg to 9.0 mg NaCl, 0.15 mg to 0.25 mg polysorbate, 0.25 mg to 0.30 mg anhydrous citric acid, and 0.45 mg to 0.55 mg sodium citrate per 1 ml of water so as to achieve a pH of about 4.0 to 5.0. A suspension can employ, for example, lyophilised antibody. The therapeutic suspensions or solution formulations can also contain one or more excipients. Excipients are well known in the art and include buffers (e.g., citrate buffer, phosphate buffer, acetate buffer and bicarbonate buffer), amino acids, urea, alcohols, ascorbic acid, phospholipids, proteins (e.g., serum albumin), EDTA, sodium chloride, liposomes, mannitol, sorbitol, and glycerol. Solutions or suspensions can be encapsulated in liposomes or biodegradable microspheres. The formulation will generally be provided in a substantially sterile form employing sterile manufacture processes.

This may include production and sterilization by filtration of the buffered solvent/solution used for the for the formulation, aseptic suspension of the antibody in the sterile buffered solvent solution, and dispensing of the formulation into sterile receptacles by methods familiar to those of ordinary skill in the art.

Nebulizable formulation according to the present disclosure may be provided, for example, as single dose units (e.g., sealed plastic containers or vials) packed in foil envelopes. Each vial contains a unit dose in a volume, e.g., 2 ml, of solvent/solution buffer.

The antibodies formats of the present disclosure are thought to be suitable for delivery via nebulisation.

For ophthalmic administration the compounds according to the present invention may be conveniently formulated as microionized suspensions in isotonic, pH-adjusted sterile saline, either with or without a preservative such as a bactericidal or fungicidal agent, for example phenylmercuric nitrate, benzylalkonium chloride or chlorhexidine acetate. Alternatively, for ophthalmic administration compounds may be formulated in an ointment such as petrolatum. For rectal administration the compounds according to the present invention may be conveniently formulated as suppositories. These can be prepared by mixing the active component with a suitable non-irritating excipient which is solid at room temperature but liquid at rectal temperature and so will melt in the rectum to release the active component. Such materials include, for example, cocoa butter, beeswax and polyethylene glycols.

The quantity of a compound of the invention required for the prophylaxis or treatment of a particular condition will vary depending on the compound chosen and the condition of the patient to be treated. In general, however, daily dosages may range from around 10 ng/kg to 1000 mg/kg, typically from 100 ng/kg to 100 mg/kg, e.g. around 0.01 mg/kg to 40 mg/kg body weight for oral or buccal administration, from around 10 ng/kg to 50 mg/kg body weight for parenteral administration, and from around 0.05 mg to around 1000 mg, e.g. from around 0.5 mg to around 1000 mg, for nasal administration or administration by inhalation or insufflation.

Preferred features of each embodiment of the invention are as for each of the other embodiments mutatis mutandis. All publications, including but not limited to patents and patent applications cited in this specification are herein incorporated by reference as if each individual publication were specifically and individually indicated to be incorporated by reference herein as though fully set forth.

Comprising in the context of the present specification is intended to meaning including. Where technically appropriate embodiments of the invention may be combined.

Embodiments are described herein as comprising certain features/elements. The disclosure also extends to separate embodiments consisting or consisting essentially of said features/elements. The invention will now be described with reference to the following examples, which are merely illustrative and should not in any way be construed as limiting the scope of the present invention.

List of Figures: Figure 1 : Diagrammatic representation of Fab-dAbs where the dAb is at the C- terminus

Figure 2A: Diagrammatic representation of Fab-didAbs

Figure 2B: Diagrammatic representation of Fab-didAbs with additional disulfide stabilisation between the dAbs. Figure 3 : SDS PAGE analysis of FabA-dAbL3 (CK-SG₄SE) ( 1 ) and FabA-dAbL3 (CK-G[APAPA]₂) (2).

Figure 4: Western blot analysis of FabA-dAbL3 (CK-SG₄SE) (1) and FabA-dAbL3 (CK-G[APAPA]₂) (2). Figure 4a: SDS PAGE of FabB-didAbs Lane M = SeeBlue markers

Lanes 1 & 2 = IgG control Lane 3 = FabB

Lane 4 = FabB-didAb, -dAbLl (CK-G4Sx2) & dAbHl (CHl-G4Sx2) Lane 5 = FabB-didAb, -dAbL2 (CK-G4Sx2) & dAbH2 (CHl-G4Sx2) Figure 5: Sequences of domain antibodies dAbHl , dAbH2, dAbLl and dAbL2 and the CDRs derived from each of those antibodies.

Figure 6: FabB-dAb constructs comprising FabB heavy or light chain variable domain fused to a domain antibody.

Figure 7 Fab'A heavy and light chain sequences and FabA heavy chain sequence.. Figure 8a, 8b & 8c Murinised Fab-didAb amino acid sequences.

Figure 8a shows the amino acid sequence of CDRs in various murine dAbs. Figure 8b shows the amino acid sequence of mFabD-mdidAb: dAbLl (CK-G4Sx2) dAbHl (CH l -G4Sx2) dAbL2(CK-G4Sx2) & dAbH2(CHl -G4Sx2) Figure 8c shows the amino acid sequence of mFabD-mdidAb: dAbLl(CK-G4Sx2) & dAbH 1 (CH 1 -G4Sx2)mFabC-mdAbH 1 dAbL2(CK-G4Sx2) & dAbH2(CHl-G4Sx2 Figure 9 shows SDS PAGE of FabB-didAbs Lanes 1 & 4 are Fab'B

Lanes 2 & 5 are FabB-didAb, -dAbLl(CK-G4Sx2) & -dAbH 1 (CH l-G4Sx2) Lanes 3 & 6 are FabB-didAb, -dAbL2(CK-G4Sx2) & -dAbH2(CHl-G4Sx2) Figure 10 shows a diagrammatic representation of a Thermofluor thermal stability assay.

Figure 1 1 shows a plot of HAS-FITC signal/HAS-FITC mixes bound to activated mouse T cells.

Figure 12 shows a plot of an aggregation stability assay. Figure 13 shows in vivo concentration profiles over time after subcutaneous and intravenous dosing

Figure 14A, B and C show certain CD4+ cell and CD8+ cell readouts Figure 15 shows SDS-PAGE analysis of FabB-645Fv Figure 16 shows size exclusion analysis of FabB-645Fv Figure 17 shows thermograms of FabB-645Fv with various linker lengths. Figure 18 shows SDS-PAGE analysis of certain FabB constructs

Figure 19 shows size exclusion analysis of various FabB-645Fv constructs Figures 20 to 24 show sequences for certain formats.

KEY -645Fv equates to didAbLland Hl (the linker used for each dAB will be the same unless indicated otherwise). 648Fv equates to didAbL2 and H2 (the linker used for each dAB will be the same unless indicated otherwise).

-645dsFv equates to didAbLland Hl (the linker used for each dAB will be the same unless indicated otherwise) wherein Ll and Hl are stabilised by a disulfide bond. -648dsFv equates to didAbL2and H2 (the linker used for each dAB will be the same unless indicated otherwise) wherein L2 and H3 are stabilised by a disulfide bond. FabΔ are Fabs which lack the interchain cysteine bond (ie between CH and

CL or CK)

Experimental:

Abbreviations: unless the context indicates otherwise "m" as a pre-fix is intended to refer to murine.

Unless the context indicates otherwise "h" as a pre-fix is intended to refer to human. Fab A, Fab B, Fab C and Fab D components may be provided below in different formats.

EXAMPLE 1. Production of a dAb specific for human serum albumin

An in-frame DNA encoded transcription unit encoding a dAb with specificity for human serum albumin was produced using recombinant DNA technology.

Where desired an in-frame DNA encoded transcription unit encoding a dAb with specificity for a recruitment protein can be produced using recombinant DNA technology.

EXAMPLE 2. Production of antibody fragment

For fusion of a dAb to the C-terminus of the light chain, DNA was synthesised encoding a human kappa light chain constant region (with the Km3 allotype of the kappa constant region), a peptide linker and a dAb and cloned as a SacI-PvuII restriction fragment into the UCB-Celltech in-house expression vector pTTOD(Fab) (a derivative of pTTO-1 , described in Popplewell et al., Methods MoI. Biol. 2005;

308: 17-30) which contains DNA encoding the human gamma- 1 CHl constant region. This gave rise to a dicistronic gene arrangement consisting of the gene for the humanised light chain fused via a linker to a dAb followed by the gene for the humanised heavy chain Fab fragment, both under the control of the tac promoter. Also encoded is a unique BspEl site upstream of the Gly4Ser linker, or an Ascl site upstream of the Ala-Pro-rich linker.

For fusion of a dAb the C-terminus of the heavy chain, DNA was synthesised encoding a human CHl fragment (of the γl isotype) followed by a linker encoding sequence and a dAb. This was subcloned as an Apal-EcoRI restriction fragment into the UCB-Celltech in-house expression vector pTTOD(Fab) (a derivative of pTTO-1, described in Popplewell et al., above) which contains DNA encoding the human gamma- 1 CHl constant region. This gave rise to a dicistronic gene arrangement consisting of the gene for the humanised light chain a non-coding intergenic sequence and followed by a heavy chain fused via a linker to a dAb, both under the control of the tac promoter. The recombinant expression plasmid was transformed into the E. coli strain W31 10 in which expression is induced by addition of IPTG. Expression experiments were performed at small scale initially (5ml culture volumes) with addition of 20OuM IPTG at OD(600nm) of approx. 0.5, cells were harvested 2 hours post induction and extracted overnight at 30⁰C in Tris/EDTA. Clarified extracts were used for affinity analysis by Biacore. Constructs giving promising expression yields and activities were selected for fermentation. Methods applicable to the following Examples

In the following examples the antibody chain to which the dAb is fused is denoted either as CK or LC for the cKappa light chain and as CHl or HC for the heavy chain constant domain, CH 1.

Construction of FabA-dAb fusion plasmids for expression in E.coli

Fab-dAb fusion proteins were constructed by fusing dAbL3 or dAbH4 to the C- terminus of the constant region of either the light or heavy chain of FabA. A flexible (SGGGGSE (SEQ ID NOrI)) or a rigid (G(APAPA)₂ (SEQ ID NO: 34)) linker was used to link the dAb to the cKappa region (SEQ ID NO:75) whereas the linker DKTHTS (SEQ ID NO:2) was used to link the dAb to the CHI region (SEQ ID NO:76). The DNA sequence coding for the constant region-dAb fusion was manufactured synthetically as fragments to enable sub-cloning into the FabA sequence of the in-house pTTOD vector.

Light chain-dAb fusions were constructed by sub-cloning the Sacl-Apal fragment of the synthesized genes, encoding a C-terminal cKappa fused to either dAbL3 or dAbH4 via either a (SGGGGSE (SEQ ID NO: I)) or a rigid (G(APAPA)₂ (SEQ ID NO: 34)) linker, into the corresponding sites of a plasmid capable of expressing FabA. Heavy chain-dAb fusions were constructed by sub-cloning the Apal-EcoRl fragment of the synthesised genes, encoding a C-terminal CHI fused to either dAbL3 or dAbH4 via a DKTHTS linker, into the corresponding sites of a plasmid capable of expressing FabA. Fab' A is derived from an IL-I beta binding antibody, the heavy and light chain sequences of which are provided in SEQ ID NOs:74 and 75 respectively as shown in Figure 7. In Fab'A where the light chain has a dAb attached, the hinge of the heavy chain was altered to DKTHTS even where no dAb is attached to the heavy chain (SEQ ID NO:76). FabA comprises the same light chain sequence (SEQ ID NO:75) and a truncated heavy chain sequence which terminates at the interchain cysteine (SEQ ID NO:77). dAbL3 and dAbH4 are light and heavy chain domain antibodies respectively which bind human serum albumin.

Construction of FabA-didAb fusion plasmids for expression in E.coli FabA-didAb with dAbL3 or dAbH4 on both light and heavy chains were constructed by sub-cloning the Apal-EcoRl fragment coding for CHl-dAb fusions into the existing Fab-dAb plasmids where the dAb is fused to the light chain via the flexible linker.

Construction of FabB-dAb fusion plasmids for expression in mammalian cells The FabB-dAbs, FabB-dAbHl (CHl-G₄Sx2), FabB-dAbH2 (CHl-G₄Sx2), FabB- dAbLl (CHl-G₄Sx2), FabB-dAbL2 (CHl-G₄Sx2) were all assembled by PCR then cloned into a mammalian expression vector under the control of the HCMV-MIE promoter and SV40E polyA sequence. These were paired with a similar vector containing the FabB light chain for expression in mammalian cells (see below).

FabB is derived from an antibody which bids a cell surface co-stimulatory molecule. dAbHl, dAbH2, dAbLl and dAbL2 were obtained as described in Example 3.

Mammalian expression of FabB-dAbs and didAbs

HEK293 cells were transfected with the heavy and light chain plasmids using Invitrogen's 293fectin transfection reagent according to the manufacturer's instructions. Briefly, 2μg heavy chain plasmid + 2μg light chain plasmid was incubated with lOμl 293fectin + 340μl Optimem media for 20mins at RT. The mixture was then added to 5x10⁶ HEK293 cells in suspension and incubated for 4 days with shaking at 37⁰C.

Biacore

Binding affinities and kinetic parameters for the interactions of Fab-dAb constructs were determined by surface plasmon resonance (SPR) conducted on a Biacore TlOO using CM5 sensor chips and HBS-EP (1OmM HEPES (pH7.4), 15OmM NaCl, 3mM EDTA, 0.05% v/v surfactant P20) running buffer. Fab-dAb samples were captured to the sensor chip surface using either a human F(ab')₂-specific goat Fab (Jackson ImmunoResearch, 109-006-097) or an in-house generated anti human CH 1 monoclonal antibody. Covalent immobilisation of the capture antibody was achieved by standard amine coupling chemistry.

Each assay cycle consisted of firstly capturing the Fab-dAb using a 1 min injection, before an association phase consisting of a 3 min injection of antigen, after which dissociation was monitored for 5 min. After each cycle, the capture surface was regenerated with 2 x 1 min injections of 4OmM HCl followed by 30s of 5mM NaOH.

The flow rates used were lOμl/min for capture, 30μl/min for association and dissociation phases, and lOμl/min for regeneration.

For kinetic assays, a titration of antigen (for human serum albumin typically 62.5nM- 2μM, for IL-lβ 1.25-4OnM) was performed, a blank flow-cell was used for reference subtraction and buffer-blank injections were included to subtract instrument noise and drift.

Kinetic parameters were determined by simultaneous global-fitting of the resulting sensorgrams to a standard 1 : 1 binding model using Biacore TlOO Evaluation software. In order to test for simultaneous binding, 3 min injections of either separate 5μM HSA or 10OnM IL- lβ, or a mixed solution of 5μM HSA and 10OnM IL- lβ were injected over the captured Fab-dAb.

Fab-dAb Purification from E.coli Periplasmic extraction

E.coli pellets containing the Fab-dAbs within the periplasm were re-suspended in original culture volume with 10OmM Tris/HCl, 1OmM EDTA pH 7.4. These suspensions were then incubated at 4⁰C for 16 hours at 250rpm. The re-suspended pellets were centrifuged at 10000xg for 1 hour at 4⁰C. The supernatants were removed and 0.45μm filtered. Protein-G capture

The Fab-dAbs were captured from the filtered supernatant by Protein-G chromatography. Briefly the supernatants were applied, with a 20 minute residence time, to a Gammabind Plus Sepharose (GE Healthcare) column equilibrated in 2OmM phosphate, 15OmM NaCl pH7.1. The column was washed with 2OmM phosphate, 15OmM NaCl pH7.1 and the bound material eluted with 0.1M glycine/HCl pH2.8. The elution peak was collected and pH adjusted to ~pH5 with IM sodium acetate. The pH adjusted elutions were concentrated and diafiltered into 5OmM sodium acetate pH4.5 using a 10k MWCO membrane.

Ion Exchange

The Fab-dAbs were further purified by cation exchange chromatography at pH4.5 with a NaCl elution gradient. Briefly the diafiltered Protein-G eluates were applied to a Sourcel5S (GE Healthcare) column equilibrated in 5OmM sodium acetate pH4.5. The column was washed with 5OmM sodium acetate pH4.5 and the bound material eluted with a 20 column volume linear gradient from 0 to IM NaCl in 5OmM sodium acetate pH4.5. Third column volume fractions were collected through out the gradient. The fractions were analysed by A280 and SDS-PAGE and relevant fractions pooled.

Gel filtration

If required the Fab-dAbs were further purified by gel filtration. Briefly the FabA- dAbL3 (CK-SG₄SE) pooled ion exchange elution fractions were applied to a Superdex200 (GE Healthcare) column equilibrated in 5OmM sodium acetate, 125mM

NaCl pH 5.0 and eluted with an isocratic gradient of 5OmM sodium acetate, 125mM

NaCl pH 5.0. 1/120 column volume fractions were collected through out the gradient.

The fractions were analysed by A280 and SDS-PAGE and relevant fractions pooled.

For Fab-dAbs that did not undergo gel filtration, the pooled ion exchange elution fractions were concentrated and diafiltered into 5OmM sodium acetate, 125mM NaCl pH 5.0 using a 10k MWCO membrane. SDS-PAGE

Samples were diluted with water where required and then to lOμl was added lOμL 2X sample running buffer. For non-reduced samples, 2μL of 10OmM NEM was added at this point, for reduced samples 2μL of 1OX reducing agent was added. The sample were vortexed, incubated at 85⁰C for 5 mins, cooled and centrifuged at 12500 rpm for 30secs. The prepared samples were loaded on to a 4-20% acrylamine Tris/Glycine SDS gel and run for lOOmins at 125 V. The gels were either transferred onto PVDF membranes for Western blotting or stained with Coomassie Blue protein stain.

Western Blotting

Gels were transferred to PVDF membranes in 12mM Tris, 96mM glycine pH8.3 for 16 hours at 150mA. The PVDF membrane was block for lhr with 2% Marvel™ in PBS + 0.1% Tween20 (Blocking buffer) anti-light chain HRP-rabbit anti-human kappa light chains, 1/5000 dilution in blocking buffer for lhr. anti-heavy chain mouse anti-human heavy chain, 1/7000 dilution in blocking buffer for lhr. Followed by HRP-goat anti-mouse, 1/2000 dilution in blocking buffer for lhr. anti-His tag rabbit anti-Hisό, 1/1000 dilution in blocking buffer for lhr. Followed by HRP-goat anti-rabbit IgG, 1/1000 dilution in blocking buffer for lhr.

All blots were washed 6 times with 100ml PBS + 0.1% Tween20 for 10 minutes per wash. The blots were developed with either ECL reagent for lmin before being exposed to Amersham Hyperfilm, or metal enhanced DAB reagent for 20-30 minutes followed by water.

High temperature reverse phase HPLC

Samples (2μg) were analysed on a 2.1mm C8 Poroshell column at 80⁰C, with a flow rate of 2ml/min and a gradient of 18-38% B over 4mins. A = 0.1 % TFA in H₂O B = 0.065% TFA in 80:20 IPA:MeOH. Detection is by absorption at 214nm.

ELISA

The yields of Fab-dAb were measured using a sandwich ELISA. Briefly, the Fab- dAb was captured with an anti-CHI antibody then revealed with an anti-kappa-HRP.

FACS

Samples (mFabD-didAb's) were incubated with 5μg/ml FITC (fluorescein isothiocyanate) labelled HSA for 45 min. The sample/HSA-FITC incubations were then added to activated mouse CD4+ T-cells and incubated for a further 45 min. The cells were washed with PBS and the cell associated fluorescence measured by FACS (fluorescence activated cell sorting). EXAMPLE 3 Generating anti-albumin antibodies

Vi lop rabbits were immunised with recombinant chromapure human serum albumin (purchased from Jackson). Rabbits received 3 immunisations of lOOug HSA protein subcutaneously, the first immunisation in complete Freunds adjuvant and subsequent immunisations in incomplete Freunds. Antibodies 1 and 2, 646, 647, and 649 which bind human, mouse and rat serum albumin were isolated using the methods described in WO04/051268. Genes for the heavy chain variable domain (VH) and light chain variable domain (VL) of antibodies 1 and 2 were isolated and sequenced following cloning via reverse transcription PCR.

The light chain grafted sequences were sub-cloned into the rabbit light chain expression vector pVRbcK which contains the DNA encoding the rabbit C-Kappa constant region. The heavy chain grafted sequences were sub-cloned into the rabbit heavy chain expression vector pVRbHFab, which contains the DNA encoding the rabbit Fab' heavy chain constant region. Plasmids were co-transfected into CHO cells and the antibodies produced screened for albumin binding and affinity (Table 1). Transfections of CHO cells were performed using the Lipofectamine™ 2000 procedure according to manufacturer's instructions (InVitrogen, catalogue No. 1 1668).

Generating Humanised domain antibodies dAbLl, dAbHl, dAbL2 and dAbH2

Humanised VL and VH regions were designed using human V-region acceptor frameworks and donor residues in the framework regions. One grafted VL region (Ll (SEQ ID NO:53) and L2 (SEQ ID NO:55)) and one VH region (Hl (SEQ ID NO:52) and H2 (SEQ ID NO:54)) were designed for each of antibodies 1 and 2 respectively and genes were built by oligonucleotide assembly and PCR mutagenesis. The grafted domain antibodies and their CDRs are shown in Figure 5.

Table 1: Affinities of anti-albumin antibodies

EXAMPLE 4: Analysis of FabB-dAbs expressed in mammalian cells

FabB-dAb constructs were produced as described in the methods and the supernatants from the tranfected HEK293 cells containing the FabB-dAbs were tested directly in BIAcore.

Kinetic analysis was conducted to assess the interaction of HSA with FabB-dAb constructs. These consisted of either dAbLl, dAbH2 or dAbL3 fused to the C- terminus of CHl of FabB (See Figure 6). The FabB-dAbLl has a higher affinity for HSA , K_D = 17OnM, than FabB-dAbL3, K_D = 392nM. The FabB-dAbH2 was shown to possess the poorest affinity towards HSA, K_D - 1074nM, see Table 2.

Table 2

Affinity and kinetic parameters determined for the binding of HSA to FabBs fused to dAbLl, dAbH2 or dAbL3. The data shown are mean values ± SEM. (For FabB- dAbLl and FabB-dAbH2 n=4. For FabB-dAbL3 n=2).

SDS-PAGE and western blotting of the FabB-dAb proteins confirmed that the FabB- dAbs produced were of the expected size.

EXAMPLE 5: Analysis of FabB-didAbs expressed in mammalian cells

FabB-didAb constructs were produced as described in the methods and the supernatants from the tranfected HEK293 cells containing the didAbs tested directly in BIAcore.

Further analysis was performed using didAb constructs in which single dAbs were fused to both heavy and light C-termini of Fab. Constructs in which the didAb was derived from a natural heavy and light variable domain pairing showed a marked improvement in affinity compared to the single dAb alone (table 2 and 3). The didAb fusion consisting of two identical dAbLls showed no improvement in affinity over that seen for the single dAbLl (data not shown). Table 3

Affinity and kinetic parameters determined for the binding of HSA to FabBs fused to both dAbLl & dAbHl or dAbL2 & dAbH2.

SDS-PAGE of the FabB-didAb proteins confirmed that the FabB-didAbs expressed well and were of the expected size (See Figure 4a). Note this SDS PAGE gel is total protein expressed by the cell.

EXAMPLE 6 Analysis of purified FabA-d Abs

Plasmids for expression of the Fab-dAbs, Fab'A-dAbL3 (CK-SG₄SE) Fab'A-dAbL3 (CK-G[APAPA]₂) in E.coli were constructed as described in the methods. The Fab- dAbs were expressed into the periplasm of the E.coli and purified to homogeneity as described in the methods. The purity of the Fab-dAbs were assessed by high temperature reverse phase HPLC, SDS-PAGE and Western blotting. The Fab-dAbs were also assessed for antigen binding by Biacore.

High temperature reverse phase HPLC

High temperature reverse phase HPLC as performed as described in the methods gave quantitative analysis of all species contained in FabA-dAbL3 (CK-SG₄SE) and FabA- dAbL3 (CK-G[APAPA]₂). The percentage of each species present is shown in table 4. Table 4: uantification of s ecies resent in Fab-dAb batches

SDS-PAGE

Fab-dAb samples were prepared under non-reduced and reduced conditions and run on a gel as described in the methods. The gel was Coomassie stained. The banding profile of both Fab-dAb samples, Fab'A-dAbL3 (CK-SG₄SE) and Fab'A-dAbL3 (CK-G[APAPA]₂), corresponds well to the profile observed by high temperature reverse phase HPLC (figure 3).

Western Blot

Fab-dAb samples were subjected to non-reduced SDS-PAGE followed by western blot analysis with anti-light chain and anti-heavy chain antibodies as described in the methods. This confirmed that the dAb was on the light chain of the Fab and that the heavy chain was unmodified in both samples (figure 4). It also demonstrates that all bands detected by coomassie stained, non-reduced SDS PAGE are Fab-dAb related products.

Biacore

Kinetic analysis by SPR as described in the methods was used to assess the binding of human serum albumin to Fab'A-dAbL3 (CK-SG₄SE) and Fab'A-dAbL3 (CK- G[APAPA]₂). The results in table 5 demonstrate that both constructs are able to bind human serum albumin with a similar affinity (K_D) of approximately lμM.

Table 5

Further kinetic analysis demonstrated that all the fusion constructs retained the interaction characteristics of the original FabA towards IL- lβ, table 6, with only minor differences seen in the kinetic and affinity parameters.

Table 6

The potential for each construct to bind simultaneously to both human serum albumin and the IL- lβ antigen was assessed by capturing each construct to the sensor chip surface, before performing either separate 3 min injections of 5μM human serum albumin or 10OnM IL- lβ, or a mixed solution of both 5μM human serum albumin and 10OnM IL- lβ. For each Fab-dAb construct the response seen for the combined HSA/IL-l β solution was almost identical to the sum of the responses of the independent injections, see table 7. This shows that the Fab-dAbs are capable of simultaneous binding to both IL- lβ and human serum albumin, and that binding of either IL- lβ or human serum albumin does not inhibit the interaction of the other. The original FabA bound only to IL- l β, with negligible binding to human serum albumin.

Table 7

The table above shows the binding response (RU) seen for each construct after separate injections of HSA or IL- lβ, or injection of premixed HSA and IL-I β. In each case the final concentration was 5μM for HSA and 10OnM for IL- lβ. The sum of the individual HSA and IL-I β responses is shown in parentheses.

EXAMPLE 7 FabA didAbs Expression of FabA-did Abs in E.coli

FabA-dAbs and FabA-didAb fusions terminating with a C-terminal histidine tag (HIS6 tag) were expressed in Escherichia coli. After periplasmic extraction, dAb fusion proteins were purified via the C-terminal His6 tag. Fab expression was analysed by Western blotting of a non-reduced gel with anti-CHI and anti-cKappa antibodies. FabA-dAb and FabA-didAb were expressed as full-length proteins and were shown to react to both antibody detection reagents.

Analysis of FabA-didAbs expressed in E.coli

Further analysis was conducted to characterise the binding of HSA to FabA constructs to which one or more dAbs were fused. Binding assays were performed on a variety of constructs in which dAbL3 or dAbH4 fused to either the light or heavy chain of the FabA (see Table 8 for details of the constructs and summary of the binding data). Although constructs carrying only dAbH4, on either the light or heavy chain, were seen to bind HSA with comparatively poor affinity (~9μM and 3μM respectively), higher affinity binding was observed for constructs carrying dAbL3, either as a single fusion (on either light or heavy chain) or partnered with a second dAb (dAbL3 or dAbH4) on the opposing chain.

Table 8

Affinity and kinetic parameters determined for the binding of HSA to FabAs carrying dAbL3 or dAbH4 on either light chain (LC) or heavy chain (HC) or both as indicated. No binding (nb) of HSA to the original FabA was detected. The interaction kinetics for the binding of HSA to the FabA with (dAbH4 on HC) or (dAbH4 on LC), were too rapid to determine, therefore affinity (KD) was determined from steady-state binding.

EXAMPLE 8

Expression and purification of FabB-didAbs

Mammalian expression Prior to transfection CHO-XE cells were washed in Earls Balanced Salts Solution (EBSS), pelleted and resuspended in EBSS at 2x10⁸ cells/ml. Heavy and light chain plasmids were added to the cells at a total concentration of 400ug. Optimised electrical parameters for 800μl cells/DNA mix on the in-house electroporator were used for transfection. Transfected cells were directly transferred to 1 L CD-CHO media supplied with glutamax, HT and antimycotic antibiotic solution. Cells were incubated, shaking at 37°C for 24 hours and then shifted to 32°C. Sodium Butyrate 3mM was added on day 4. Supernatants were harvested on day 14 by centrifugation at 1500xg to remove cells. Expression levels were determined by ELISA.

Mammalian expression supernatant concentration

The mammalian supernatants containing ~55μg/ml of FabB-didAb as assessed by ELISA were concentrated from 1.8L to 200ml using a Minisette concentrator fitted with a 1OkDa molecular weight cut off polyethersulphone (PES) membrane. Protein-G purification

The concentrated supernatants were applied to a Gammabind Plus Sepharose (GE Healthcare) column equilibrated in 2OmM phosphate, 15OmM NaCl pH7.1. The column was washed with 2OmM phosphate, 15OmM NaCl pH7.1 and the bound material eluted with 0.1M glycine/HCl pH2.7. The elution peak was collected and pH adjusted to ~pH7 with 2M Tris/HCl pH8.8. The pH adjusted elutions were concentrated to lmg/ml and diafiltered into 2OmM phosphate, 15OmM NaCl pH7.1 using a 1OkD molecular weight cut off PES membrane.

SDS-PAGE

Samples were diluted with water where required and then to 26μl was added 10μL 4X LDS sample running buffer. For non-reduced samples, 4μL of 10OmM NEM was added and for reduced samples 4μL of 1OX reducing agent was added. The samples were vortexed, incubated at 85⁰C for 5 mins, cooled and centrifuged at 12500 rpm for 30secs. The prepared samples were loaded on to a 4-20% acrylamine Tris/Glycine SDS gel and run for 1 lOmins at 125V. The gels were stained with Coomassie Blue protein stain.

ELISA The yields of Fab-didAb were measured using a sandwich ELISA. Briefly, the Fab- didAb was captured with an anti-CHI antibody then revealed with an anti-kappa- HRP.

SDS-PAGE FabB and FabB-didAb samples were prepared under non-reduced and reduced conditions and separated on a gel and stained as described in the methods. See Figure 9.

EXAMPLE 9 Thermofluor thermal stability assay on FabB-Fv

Samples (l μl of sample at ~lmg/ml, 8μl of PBS and l μl of 30x stock of Sypro orange fluorescent dye) were run in quadruplicate in 384 well plates. The plate is heated from 20-99⁰C using a 7900HT fast real-time PCR system and the fluorescence (excitation at 490nm, emission at 530nm) measured. The results are shown in Table D and Figure 10. Table 9

EXAMPLE 10

Aggregation stability assay of FabB-Fv

Samples at lmg/ml in PBS were incubated at 25⁰C with vortexing at 1400rpm. The absorbance is measured at 595nm. This absorbance is due to light scattered by particles and can be correlated with sample aggregation. Both FabB-645Fv (G₄Sx2) and FabB-648Fv (G₄Sx2) are as resistant to aggregation as FabB alone. They are all more resistant to aggregation than the IgG control. (Figure 12)

EXAMPLE Il pH dependency of Fab-Fv binding to HSA

Binding affinities for the interactions of Fab-Fv constructs with HSA were determined as described in the methods except that the running buffers at pH5.0, 5.5, 6.0 and 7.0 were created by mixing 4OmM citric acid, 15OmM NaCl, 3mM EDTA, 0.05% v/v surfactant P20 and 8OmM disodium hydrogen phosphate, 15OmM NaCl, 3mM EDTA, 0.05% v/v surfactant P20 to give the desired pH.

The affinity of FabB-645Fv (G₄Sx2) for HSA is unaffected by pH from 7.4 (standard assay pH) to 5.0. The affinity of FabB-648Fv (G₄Sx2) for HSA is affected by pH and there is approximately a 10 fold loss in affinity between pH7.4 and pH5.0. Table 10

EXAMPLE 12

In vivo murine PK of FabB-Fv The pharmacokinetics of FabB-645Fv (G₄Sx2) and FabB-648Fv (G₄Sx2) in male BALB/c mouse were determined following a single administration at 10mg/kg either subcutaneously (sc) or intravenously (iv). Six mice were dosed for each construct and route of administration. Serial blood samples (30 μL) were collected from the tail vein at the following time points: 1, 4, 8, 24, 48, 72, 102 and 168 hours following subcutaneous administration and 30 minutes, 1, 8, 24, 48, 72, 96 and 168 hours following intravenous administration. The collected blood was dispensed into a Sarstedt microvette CB300Z with clot activator for serum separation, and left at room temperature for at least 20 minutes. The microvette was then centrifuged at 20⁰C at 10,000 rpm for 5 minutes. Serum was removed and stored frozen prior to analysis. The concentration of FabB-645Fv (G₄SX2) or FabB-648Fv (G₄SX2) in serum samples was assessed by ELISA. Briefly Nunc Maxisorb Immunomodule Plates were coated with hOX40-Fc in PBS and blocked with 1% BSA in PBS. Serum samples and standards were diluted in 1% BSA in PBS and applied to the plate for 1 hour. The plate was washed with PBS and the revealing antibody of goat anti-human kappa HRP conjugate applied in 1% BSA in PBS for 1 hour. The plate was washed and then developed with TMB substrate followed by stopping with 2.5M sulphuric acid. The absorbance at 630nm wash measured and the concentrations determined from the standard curve. Both FabB-645Fv (G₄Sx2) and FabB-648Fv (G₄Sx2) have extended half-life in plasma, Figure 13. The half-lives for FabB-645Fv (G₄Sx2) are 71 h sc and 62h iv and for FabB-648Fv (G₄Sx2) are 25h sc and 30h iv.

EXAMPLE 13 In vivo efficacy study of FabB-Fv

A study to investigate if FabB-645Fv and FabB-648Fv are efficacious in vivo was undertaken. Briefly this involved steady state dosing in HuSCID mice and the read out was the prevention of T cell engraftment. CB 17 SCID mice were dosed with a loading dose subcutaneously on day -2 of 2.475mg/kg FabB-645Fv or FabB-648Fv or FabB-PEG40k or PBS. On every subsequent day up to and including day 10 they were dosed with a maintenance dose subcutaneously of 0.75mg/kg FabB-645Fv or FabB-648Fv or FabB-PEG40k or PBS. Each dosing group consisted of 9-10 mice. On day -1 all the mice were treated with 0.87mg/mouse of rat anti-murine TM-βl antibody to abrogate natural killer cell activity. On day 0 all the mice received an inter peritoneal injection of 8x10⁶ human peripheral blood mononuclear cells. On day 14 the mice are sacrificed and the blood, spleen and a peritoneal lavage were taken. The samples were analysed by FACS for CD4⁺ and CD8⁺ T cells. The data sets were analysed by one way Anova with Dunnett's post test comparison. All the test constructs FabB-645Fv, FabB-648Fv and FabB-PEG40k were equally efficacious in all the compartments tested, i.e. blood peritoneum and spleen. Figures 14A, B and C.

EXAMPLE 14

FabB-645Fv mutations to change the affinity of 645Fv for albumin Point mutations were introduced into selected residues in the CDRs of the heavy chain of the 645Fv portion of FabB-645dsFv (S3xG₄S) by mutagenic PCR. For example I50A is a replacement of He 50 with Ala. The various mutations are given in Table 11 below. The affinity of the Fab-645Fv mutants for human albumin was assessed by BIAcore as described in the methods. All the mutations had either unchanged or reduced affinity for human albumin. Table 11

EXAMPLE 15

1-5 Gly4Ser linker length between Fab and Fv

Construction of FabB-645Fv fusion plasmids for expression in mammalian cells The FabB-645Fv's with either a SGGGGS, SGGGGSGGGGS, SGGGGSGGGGSGGGGS, SGGGGSGGGGSGGGGSGGGGS or SGGGGSGGGGSGGGGSGGGGSGGGGS linker between the C-termini of the Fab and the N-termini of the Fv were assembled by PCR then cloned into a mammalian expression vectors under the control of the HCMV-MIE promoter and SV40E polyA sequence. The relevant heavy and light chain plasmids were paired for expression in mammalian cells.

Mammalian expression of FabB-645Fv (I-5XG₄S)

HEK293 cells were transfected with the heavy and light chain plasmids using Invitrogen's 293fectin transfection reagent according to the manufacturer's instructions. Briefly, 24μg heavy chain plasmid + 24μg light chain plasmid was incubated with 120μl 293fectin + 4080μl Optimem media for 20mins at RT. The mixture was then added to 6OxIO⁶ HEK293 cells in 6OmL suspension and incubated for 4 days with shaking at 37°C. All the constructs were equally well expressed. Protein-G purification

The mammalian expression suspensions were clarified by centrifugation and the supernatants were concentrated to ~1.8mL using 1OkDa molecular weight cut off centrifugation concentrators. The concentrated supernatants were centrifuged at 16000xg for 10 min to remove any precipitate and then 1.5mL was loaded onto ImI HiTrap Protein-G columns (GE Healthcare) at lml/min. The columns were washed with 2OmM phosphate, 4OmM NaCl pH7.4 and bound material eluted with 0.1 M glycine/HCl pH2.7. The elution peak (2mL) was collected and pH adjusted to ~pH5 with 250μL of IM sodium acetate. The pH adjusted elutions were diafiltered into 2OmM phosphate, 15OmM NaCl pH7.1 using 1OkDa molecular weight cut off centrifugation concentrators and concentrated to ~250μL. All the constructs had similar purification profiles and the final concentrations were 0.5-1. lmg/ml.

Affinity of FabB-645Fv (l-5xG₄S) for albumin

The affinities of the purified FabB-645Fv (l-5xG₄S) constructs for human and mouse albumin were determined as described in the Methods. The different linker lengths of the Fv of 1 to 5 xGly4Ser between the C-termini of the Fab and the N-termini of the Fv had no affect on the affinity of the 645Fv for either human or mouse albumin.

Table 12

SDS-PAGE analysis of purified FabB-645Fv (l-5xG₄S)

FabB-645Fv (l-5xG₄S) samples were prepared under non-reduced and reduced conditions and separated on a gel and stained as described in the methods. See Figure 15.

Size exclusion analysis of purified FabB-645Fv (1-SxG₄S)

FabB-645Fv (l -5xG₄S) samples were analysed for size on a Superdex200 10/300GL Tricorn column (GE Healthcare) developed with an isocratic gradient of 2OmM phosphate 15OmM NaCl pH7.4 at lml/min.

A linker length between the C-termini of the Fab and the N-termini of the Fv of either IxG₄S or 2xG₄S reduces the amount of monomer FabB-645Fv whilst increasing the amount of dimer and higher multimers. The amount of monomer is least for the IxG₄S linker length. A linker length between the C-termini of the Fab and the N- termini of the Fv of either 3xG₄S, 4xG₄S or 5xG₄S increased the amount of monomer FabB-645Fv whilst decreasing the amount of dimer and higher multimers with the levels being similar for all three linker lengths. Figure 16.

Table 13

Thermofluor thermal stability analysis of purified FabB-645Fv (1-5XG₄S)

Samples (l μl of sample at ~lmg/ml, 8μl of PBS and l μl of 3Ox stock of Sypro orange fluorescent dye) were run in quadruplicate in 384 well plates. The plate is heated from 20-99⁰C using a 7900HT fast real-time PCR system and the fluorescence (excitation at 490nm, emission at 530nm) measured. The results are shown in Table 14 and Figure 17.

EXAMPLE 16

Disulphide stabilisation of the Fv in a Fab-Fv

FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S), FabΔB-645dsFv (2xG₄S) and

FabΔB-648dsFv (2xG₄S) fusion plasmids for expression in mammalian cells

Point mutations were introduced into the FabB-645Fv (2xG₄S) and FabB-648Fv (2xG₄S) DNA sequences at selected residues in the framework region of both the heavy chain and the light chain of the Fv by mutagenic PCR. The mutations introduced to create an interchain disulphide bond between the heavy and light chains of the Fv were heavy chain G44C and light chain GlOOC. As well as adding the cysteins to create the interchain disulphide bond in the Fv, the natural interchain disulphide between the heavy chain and light chain of the Fab was removed by mutagenic PCR by changing the cysteines to serines. Fvs that contain an interchain disulphide bond were termed dsFv, Fabs that lack an interchain disulphide bond were termed FabΔ. The DNA for all these constructs was then cloned into a mammalian expression vectors under the control of the HCMV-MIE promoter and SV40E polyA sequence. The relevant heavy and light chain plasmids were paired for expression in mammalian cells.

Mammalian expression of FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S), FabΔB-645dsFv (2xG₄S) and FabΔB-648dsFv (2xG₄S) HEK293 cells were transfected with the heavy and light chain plasmids using Invitrogen's 293fectin transfection reagent according to the manufacturer's instructions. Briefly, 24μg heavy chain plasmid + 24μg light chain plasmid was incubated with 120μl 293fectin + 4080μl Optimem media for 20mins at RT. The mixture was then added to 60x10 HEK293 cells in 6OmL suspension and incubated for 4 days with shaking at 37°C. All the constructs were equally well expressed.

Protein-G purification of FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S), FabΔB-645dsFv (2xG₄S) and FabΔB-648dsFv (2xG₄S) The mammalian expression suspensions were clarified by centrifugation and the supernatants were concentrated to ~1.8mL using 1OkDa molecular weight cut off centrifugation concentrators. The concentrated supernatants were centrifuged at 16000xg for 10 min to remove any precipitate and then 1.5mL was loaded onto ImI HiTrap Protein-G columns (GE Healthcare) at lml/min. The columns were washed with 2OmM phosphate, 4OmM NaCl pH7.4 and bound material eluted with 0.1 M glycine/HCl pH2.7. The elution peak (2mL) was collected and pH adjusted to ~pH5 with 250μL of IM sodium acetate. The pH adjusted elutions were diafiltered into 2OmM phosphate, 15OmM NaCl pH7.1 using 1OkDa molecular weight cut off centrifugation concentrators and concentrated to ~250μL. All the constructs had similar purification profiles and the final concentrations were 0.5-0.8mg/ml.

Affinity of FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S), FabΔB-645dsFv (2xG₄S) and FabΔB-648dsFv (2xG₄S) for albumin

The affinities of the purified FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S) FabΔB- 645dsFv (2XG₄S), FabΔB-648dsFv (2xG₄S) constructs for human and mouse albumin were determined as described in the Methods. The disulphide stabilisation of the Fv had no affect or slightly increased the affinity of the Fv for both human or mouse albumin.

Table 15

SDS-PAGE analysis of purified FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S),

FabΔB-645dsFv (2xG₄S) and FabΔB-648dsFv (2xG₄S)

Purified FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S) FabΔB-645dsFv (2xG₄S),

FabΔB-648dsFv (2xG₄S) samples were prepared under non-reduced and reduced conditions and separated on a gel and stained as described in the methods. See Figure

18.

Size exclusion analysis of purified FabB-645dsFv (2xG₄S), FabB-648dsFv

(2xG₄S), FabΔB-645dsFv (2xG₄S) and FabΔB-648dsFv (2xG₄S)

Purified FabB-645dsFv (2xG₄S), FabB-648dsFv (2xG₄S) FabΔB-645dsFv (2xG₄S),

FabΔB-648dsFv (2xG₄S) samples were analysed for size on a Superdex200 10/300GL

Tricorn column (GE Healthcare) developed with an isocratic gradient of 2OmM phosphate 15OmM NaCl pH7.4 at lml/min.

The introduction of an interchain disulphide bond into the Fv of either a 645Fv or

648Fv increased the amount of monomer Fab-Fv species compared with the Fab-Fv in which the Fv did not have an inter chain disulphide. The removal of the natural interchain disulphide bond from the Fab part of a Fab-Fv had only a small effect on the amount of monomer species present. Figure 19.

Table 16

Thermofluor thermal stability analysis of purified FabB-645dsFv (2xG₄S), FabB- 648dsFv (2xG₄S), FabΔB-645dsFv (2xG₄S) and FabΔB-648dsFv (2xG₄S) Samples (l μl of sample at ~lmg/ml, 8μl of PBS and l μl of 30x stock of Sypro orange fluorescent dye) were run in quadruplicate in 384 well plates. The plate is heated from 20-99⁰C using a 7900HT fast real-time PCR system and the fluorescence (excitation at 490nm, emission at 530nm) measured.

The introduction of an interchain disulphide bond into the Fv part of a Fab-Fv of either a 645Fv or 648Fv increased the thermal stability of the Fv compared with the Fab-Fv in which the Fv did not have an inter chain disulphide. The removal of the natural interchain disulphide bond from the Fab part of a Fab-Fv decreased the thermal stability of the Fab part of the Fab-Fv

Table 17

n.d. = not determined. The analysis software was unable to resolve this inflection point.

Biacore Method For FabD Binding affinities and kinetic parameters for the interactions of Fab-dAb and Fab- didAb constructs were determined by surface plasmon resonance (SPR) conducted on a Biacore TlOO using CM5 sensor chips and HBS-EP (1OmM HEPES (pH7.4), 15OmM NaCl, 3mM EDTA, 0.05% v/v surfactant P20) running buffer. Human Fab samples were captured to the sensor chip surface using either a human F(ab')₂- specific goat Fab (Jackson ImmunoResearch, 109-006-097) or an in-house generated anti human CHl monoclonal antibody. Murine Fab samples were captured using a murine F(ab')2-specific goat Fab (Jackson ImmunoResearch, 1 15-006-072). Covalent immobilisation of the capture antibody was achieved by standard amine coupling chemistry.

Each assay cycle consisted of firstly capturing the Fab-dAb or Fab-didAb construct using a 1 min injection, before an association phase consisting of a 3 min injection of antigen, after which dissociation was monitored for 5 min. After each cycle, the capture surface was regenerated with 2 x 1 min injections of 4OmM HCl followed by 30s of 5mM NaOH. The flow rates used were lOμl/min for capture, 30μl/min for association and dissociation phases, and lOμl/min for regeneration. For kinetic assays, a titration of antigen (for human or mouse serum albumin typically 62.5nM-2μM, for IL- l β 1.25-4OnM, for cell surface receptor D 20-1.25nM) was performed, a blank flow-cell was used for reference subtraction and buffer-blank injections were included to subtract instrument noise and drift.

Kinetic parameters were determined by simultaneous global-fitting of the resulting sensorgrams to a standard 1 : 1 binding model using Biacore TlOO Evaluation software. In order to test for simultaneous binding, 3 min injections of either separate 5μM HSA or 10OnM IL- lβ, or a mixed solution of 5μM HSA and 10OnM IL- lβ were injected over the captured Fab-dAb. Simultaneous binding of albumin and cell surface receptor D was assessed in the same manner using final concentrations of 2μM HSA or MSA and 2OnM murine cell surface receptor D.

EXAMPLE 17

Mammalian expression of mFabC-mdidAbs and mFabD-mdidAbs

HEK293 cells were transfected with the heavy and light chain plasmids using Invitrogen's 293fectin transfection reagent according to the manufacturer's instructions. Briefly, 2μg heavy chain plasmid + 2μg light chain plasmid was incubated with lOμl 293fectin + 340μl Optimem media for 20mins at RT. The mixture was then added to 5x10⁶ HEK293 cells in suspension and incubated for 6 days with shaking at 37°C.

ELISA

The yields of mFab-mdidAb were measured using a sandwich ELISA. Briefly, the mFab-mdidAb was captured with an anti-CHI antibody then revealed with an anti- kappa-HRP. Table 18

EXAMPLE 18

Further kinetic analysis was conducted to assess the interactions of serum albumin and human OX40 to the purified FabB-didAb, -dAbLl(CK-G4Sx2) & -dAbH 1(CHl- G4Sx2) and FabB-didAb, -dAbL2(CK-G4Sx2) & -dAbH2(CHl -G4Sx2) fusions (Table 19). Both FabB-didAb, -dAbLl(CK-G4Sx2) & -dAbH 1 (CH l-G4Sx2) and FabB-didAb, -dAbL2(CK-G4Sx2) & -dAbH2(CHl-G4Sx2) retained the affinity for human OX40 of the original FabB (Table 20).

The potential for the FabB-didAb, -dAbL 1 (CK-G4Sx2) & -dAbH 1 (CH 1 -G4Sx2) and FabB-didAb, -dAbL2(CK-G4Sx2) & -dAbH2(CHl-G4Sx2) constructs to bind simultaneously to both human or mouse serum albumin and human OX40 was assessed by capturing each Fab-didAb construct to the sensor chip surface, before performing either separate 3 min injections of 2μM albumin (human or mouse) or 5OnM human OX40, or a mixed solution of both 2μM albumin and 5OnM OX40. HSA binding was seen for both Fab-didAb constructs. For each Fab-didAb construct the response seen for the combined albumin/OX40 solution was almost identical to the sum of the responses of the independent injections (summarised in table 21). This shows that the Fab-didAbs are capable of simultaneous binding to both OX40 and serum albumin. The original FabB bound only OX40, with no significant binding to either human or mouse albumin.

Table 19

Affinity and kinetic parameters determined for HSA and MSA binding to Fab-didAb fusions.

Table 20

Affinity and kinetic parameters for hOX40-Fc binding to FabB and FabB-didAb fusions. Table 21

The table above shows the binding response (RU) seen for each construct after separate injections of HSA or MSA or hOX40-Fc, or injection of premixed albumin and hOX40-Fc. In each case the final concentration was 2μM albumin HSA and 5OnM hOX40-Fc. The sum of the individual albumin and hOX40-Fc responses is shown in parentheses.

EXAMPLE 19 Further kinetic analysis was conducted to assess the interactions of serum albumin and murine cell surface receptor D to mFabD-mdidAb, -mdAbLl(CK-G₄Sx2) & mdAbHl(CHl-G₄Sx2) and mFabD-mdidAb, -mdAbL2(CK-G₄Sx2) & mdAbH2(CHl-G₄Sx2) (Table 22). Both mFabD-mdidAbs showed relatively high affinity binding to HSA (K_D = 2.78nM and 8.97nM respectively). mFabD-mdidAb, mdAbL2(CK-G₄Sx2) & mdAbH2(CHl-G₄Sx2) also bound MSA with a similar affinity (K_D = 22nM), however no binding to MSA was seen for mFabD-mdidAb, - mdAbLl(CK-G₄Sx2) & mdAbHl(CHl-G₄Sx2). Both mFabD-mdidAbs retained the affinity for murine cell surface receptor Dof the original mFabD (Table 23).

The potential for mFabD-mdidAb, -mdAbLl(CK-G₄Sx2) & mdAbHl(CHl-G₄Sx2) and mFabD-mdidAb, -mdAbL2(CK-G₄Sx2) & mdAbH2(CHl-G₄Sx2) to bind simultaneously to both human or mouse serum albumin and murine cell surface receptor D was assessed by capturing each mFab-mdidAb construct to the sensor chip surface, before performing either separate 3 min injections of 2μM albumin (human or mouse) or 2OnM murine cell surface receptor D, or a mixed solution of both 2μM albumin and 2OnM cell surface receptor D. Again HSA binding was seen for both mFab-mdidAb constructs whereas only mFabD-mdidAb, -mdAbL2(CK-G₄Sx2) & mdAbH2(CHl-G₄Sx2) bound MSA. For each mFab-mdidAb construct the response seen for the combined albumin/ cell surface receptor D solution was almost identical to the sum of the responses of the independent injections (summarised in table 24). This shows that the mFab-mdidAbs are capable of simultaneous binding to both cell surface receptor D and serum albumin. The original mFabD bound only cell surface receptor D, with no significant binding to either human or mouse albumin.

Table 22

Affinity and kinetic parameters determined for HSA and MSA binding to mFabD- mdidAb, -mdAbLl(CK-G4Sx2) & mdAbHl(CHl-G4Sx2) and mFabD-mdidAb, -mdAbL2(CK-G4Sx2) & mdAbH2(CHl-G4Sx2). Table 23

Affinity and kinetic parameters for murine cell surface receptor D-Fc binding to mFabD, mFabD-mdidAb, -mdAbL 1 (CK-G₄Sx2) & mdAbH 1 (CH 1 -G₄Sx2) and mFabD-mdidAb, -mdAbL2(CK-G₄Sx2) & mdAbH2(CHl-G₄Sx2).

Table 24

The table above shows the binding response (RU) seen for each construct after separate injections of HSA or MSA or murine cell surface receptor D-Fc, or injection of premixed albumin and murine cell surface receptor D-Fc. In each case the final concentration was 2μM albumin HSA and 2OnM murine cell surface receptor D-Fc. The sum of the individual albumin and murine cell surface receptor D-Fc responses is shown in parentheses.

EXAMPLE 20

Further analysis was conducted to assess the simultaneous interaction of mFabD- mdidAb, -mdAbL 1 (CK-G₄Sx2) & mdAbH 1 (CH 1 -G₄Sx2) or mFabD-mdidAb, - mdAbL2(CK-G₄Sx2) & mdAbH2(CHl-G₄Sx2) with serum albumin and murine cell surface receptor D expressed on the cell surface. Both mFabD-mdidAbs were capable of binding FITC labelled HSA and cell surface receptor X expressed on the cell surface of activated murine T-cells simultaneously (figure 11). mFabD was capable of binding cell surface receptor X expressed on the cell surface of activated murine T- cells, data not shown, but did not bind FITC labelled HSA.

Claims

CLAIMS:

1. A multivalent antibody fusion protein which comprises an immunoglobulin moiety, for example a Fab or Fab' fragment, with a first specificity for an antigen of interest, and further comprises two single domain antibodies (dAb) with specificity for a second antigen of interest, wherein the two single domain antibodies are linked by a disulfide bond.

2. A multivalent antibody fusion protein according to claim 1, wherein the first antigen and second antigen are different entities.

3. A multivalent antibody fusion protein according to claim 1 or 2, wherein the two single domain antibodies are a V_H/V_L pair.

4. A multivalent antibody fusion protein according to claim 4, wherein the V_H dAb is directly or indirectly connected to the Fab or Fab' heavy chain.

5. A multivalent antibody fusion protein according to claim 4 or 5, wherein the V_L dAb is directly or indirectly connected to the Fab or Fab' light chain heavy chain.

6. A multivalent antibody fusion protein according to claim 4, wherein the V_H dAb is directly or indirectly connected to the Fab or Fab' light chain.

7. A multivalent antibody fusion protein according to claim 4 or 6, wherein the V_L dAb is directly or indirectly connected to the Fab or Fab' heavy chain.

8. A multivalent antibody fusion protein according to any one of claims 1 to 7, wherein the second antigen is albumin.

9. A multivalent antibody fusion protein according to claim 8, wherein the albumin is human serum albumin.

10. A dual specificity antibody fusion protein comprising an immunoglobulin moiety, for example a Fab or Fab' fragment, with a first specificity for an antigen of interest, and further comprises a single domain antibodies (dAb) with specificity for a second antigen of interest, which binds human serum albumin and wherein said single domain antibodies is a heavy chain VH single domain antibody which comprises at least one of a CDR having the sequence given in Figure 5 (e) SEQ ID NO:56 or Figure 5 (k) SEQ ID NO:62 for CDR-Hl, a CDR having the sequence given in Figure 5(f) SEQ ID NO:57 or Figure 5 (1) SEQ ID NO:63 for CDR-H2 and a CDR having the sequence given in Figure 5 (g) SEQ ID NO:58 or Figure 5 (m) SEQ ID NO:64 for CDR-H3.

1 1. A dual specificity antibody fusion protein comprising an immunoglobulin moiety, for example a Fab or Fab' fragment, with a first specificity for an antigen of interest, and further comprises a single domain antibodies (dAb) with specificity for a second antigen of interest, which binds human serum albumin and wherein said single domain antibodie is a light chain VL single domain antibody which comprises at least one of a CDR having the sequence given in Figure 5 (h) SEQ ID NO:59 or Figure 5 (n) SEQ ID NO:65 for CDR-Ll, a CDR having the sequence given in Figure 5(i) SEQ ID NO:60 or Figure 5 (o) SEQ ID NO:66 for CDR-L2 and a CDR having the sequence given in Figure 5 (J) SEQ ID NO:61 or Figure 5 (p) SEQ ID NO:67 for CDR-L3.

12. A dual specificity antibody fusion protein comprising an immunoglobulin moiety, for example a Fab or Fab' fragment, with a first specificity for an antigen of interest, and further comprises a single domain antibodies (dAb) with specificity for a second antigen of interest, which binds human serum albumin and wherein said single domain antibody comprises 1, 2, 3, 4, 5 or 6 CDRs selected from CDRHl with the sequence shown in SED ID NO. 56, a CDRH2 with the sequence shown in SED ID NO. 57, a CDRH3 with the sequence shown in SED ID NO. 58, a CDRLl with the sequence shown in SED ID NO. 59, a CDRL2 with the sequence shown in SED ID NO. 60, and a CDRL3 with the sequence shown in SED ID NO. 61.