CA2149329C - Therapeutic application of chimeric and radiolabeled antibodies to human b lymphocyte restricted differentiation antigen for treatment of b cell lymphoma - Google Patents

Abstract

Disclosed herein are therapeutic treatment protocols designed for the treatment of B cell lymphoma. These protocols are based upon therapeutic strategies which include the use of administration of immunologically active mouse/human chimeric anti-CD20 antibodies, radiolabeled anti-CD20 antibodies, and cooperative strategies comprising the use of chimeric anti-CD20 antibodies and radiolabeled anti-CD20 antibodies.

Description

THERAPEUTIC APPLICATION OF CHIMERIC AND RADIOLABELED
ANTIBODIES TO HUMAN B LYMPHOCYTE RESTRICTED
DIFFERENTIATION ANTIGEN FOR TREATMENT OF B CELL LYMPHOMA

37 C.F.R. 1.74(d)/(e) Copyright Notice A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner does not object to the reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.

RELATED APPLICATIONS

This application is related to Canadian Patent Application No.

2,149,326.

A

~-TA$LE OF CONTENTS
A FIELD OF THE INVENTION

B. BACKGROUND OF THE INVENTION

C, STJMMARRY OF THE INVENTION D. BRIEF DESCRIPTION OF THE DRAWINGS

E. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS F. EXAMPLES

I. RADIOLABELED ANTI-CD20 ANTIBODY 2B8 A Anti-CD20 Monoclonal Antibody (Murine) Production ("2B8") B. Preparation of 2B8-MX-DTPA Conjugate i. MX-DTPA

ii. Preparation of 2B8 iii. Conjugation of 2B8 with MX-DTPA

iv. Determination of MX-DTPA Incorporation v. Immunoreactivity of 2B8-MX-DTPA

vi. Preparation of Indium-[1111-labeled 2B8-MX-DTPA ("I2B8") vii. Preparation of Yttrium-[90]-labeled 2B8-MX-DTPA ("Y2B8") C. Non-Human Animal Studies i. Distribution of Radiolabeled 2B8-MX-DTPA
ii. Tumor Localization of 12B8 iii. Biodistribution and Tumor Localization Studies with Radiolabeled 2B8-MX-DTPA

D. Human Studies i. 2B8 and 2B8-MX-DTPA: Immunohistology Studies with Human Tissues ii. Clinical Analysis of 12B8 (Imaging) and Y2B8 (Therapy) a. Phase IlII Clinical Trial: Single Dose Therapy Study =
b. Phase I/II Clinical Trial: Multiple Dose Therapy Study II. CHIMERIC ANTI-CD20 PRODUCTION 2 149 3 2 9-A Construction of Chimeric Anti-CD20 Immunoglobulin DNA
Expression Vectors B. Creation of Cliirne:=Ic Ani;i-GD2O Producing CI30 and d31"2/0 Transfectomas C. Determination of Immunological Activity of Chimeric Anti-CD20 Antibodies i. Human Clq Analysis ii. Complement Dependent Cell Lyses iii. Antibody Dependent Cellular Cytotoxicity Effector Assay III. DEPLETION OF B CELLS IN VIVO USING CHIMERIC ANTI-CD20 A Non-Human Primate Study B. Clinical Analysis of C2B8 i. Phase I/II Clinical Trial of C2B8: Single Dose Therapy Study ii. Phase I/II Clinical Trial of C2B8: Multiple Dose Therapy Study IV. COMBINATION THERAPY: C2B8 AND Y2B8 A Preparation of Y2B8 B. Preparation of C2B8 C. Results V. ALTERNATIVE THERAPY STRATEGIES
VI. DEPOSIT INFORMATION

G. SEQUENCE LISTING
H. CLAIMS

WO 94/11026 2149 3 2 9 PC'T/US93/10953 A. FIELD OF THE INVENTION

The references to be discussed throughout this document are set forth merely for the information described therein prior to thv filing datos of this dpcumant, and nothing herein is to be construed as an admission, either express or implied, that the references are "prior art" or that the inventors are not entitled to antedate such descriptions by virtue of prior inventions or priority based on earlier filed applications.

The present invention is directed to the treatment of B cell lymphoma using chimeric and radiolabeled antibodies to the B cell surface antigen Bp35 ("CD20").
B. BACKGROUND OF THE INVENTION

The immune system of vertebrates (for example, primates, which include humans, apes, monkeys, etc.) consists of a number of organs and cell types which have evolved to: accurately and specifically recognize foreign microorganisms ("antigen") which invade the vertebrate-host; specifically bind to such foreign microorganisms; and, eliminate/destroy such foreign microorganisms.

Lymphocytes, amongst others, are critical to the immune system. Lymphocytes are produced in the thymus, spleen and bone marrow (adult) and represent about 30% of the total white blood cells present in the circulatory system of humans (adult). There are two major sub-populations of lymphocytes: T cells and B
cells.
T cells are responsible for cell mediated immunity, while B cells are responsible for antibody production (humoral immunity). However, T cells and B cells can be considered as interdependent--in a typical immune response, T cells are activated when the T cell receptor binds to fragments of an antigen that are bound to major histocompatability complex ("MHC") glycoproteins on the suz-face of an antigen presenting cell; such activation causes release of biological mediators ("interleukins") which, in essence, stimulate B cells to differentiate and produce antibody ("immunoglobulins") against the antigen.

Each B cell within the host expresses a different antibody on its surface -thus, one B cell will express antibody specific for one antigen, while another B
cell will - express antibody specific for a different antigen. Accordingly, B cells are quite diverse, and this diversity is critical to the immune system. In humans, each B
cell can produce an enormous number of antibody molecules (ie about 107 to 108).
Such antibody production most typically ceases (or substantially decreases) when the foreign antigen has been neutralized. Occasionally, however, proliferation of a particular B cell will continue unabated; such proliferation can result in a cancer referred to as "B cell lymphoma."

T cells and B cells both comprise cell surface proteins which can be utilized as "markers" for differentiation and identification. One such human B cell marker is the human B lymphocyte-restricted differentiation antigen Bp35, referred to as "CD20." CD20 is expressed during early pre-B cell development and remains until plasma cell differentiation. Specifically, the CD20 molecule may regulate a step in the activation process which is required for cell cycle initiation and differentiation and is usually expressed at very high levels on neoplastic ("tumor") B cells. CD20, by definition, is present on both "normal" B cells as well as "malignant" B cells, ie those B cells whose unabated proliferation can lead to B cell lymphoma. Thus, the CD20 surface antigen has the potential of serving as a candidate for "targeting" of B cell lymphomas.

= In essence, such targeting can be generalized as follows: antibodies specific to the CD20 surface antigen of B cells are, eg injected into a patient. These anti-CD20 antibodies specifically bind to the CD20 cell surface antigen of (ostensibly) both normal and malignant B cells; the anti-CD20 antibody bound to the CD20 6 2 1 4 9 3 2 9 PC,'1'/US93/10953 surface antigen may lead to the destruction and depletion of neoplastic B
cells.
Additionally, chemical agents or radioactive labels having the potential to destroy the tumor can be conjugated to the anti-CD20 antibody such that the agent is specifically "delivered" ta,. e.g. the neoplastic B cells.
Irresppnti.ve of the approach, a primary goal is to destroy the tumor: the specific approach can be determined by the particular anti-CD20 antibody which is utilized and, thus, the available approaches to targeting the CD20 antigen can vary considerably.

For example, attempts at such targeting of CD20 surface antigen have been reported. Murine (mouse) monoclonal antibody 1F5 (an anti-CD20 antibody) was reportedly administered by continuous intravenous infusion to B cell lymphoma patients. Extremely high levels (>2 grams) of 1F5 were reportedly required to deplete circulating tumor cells, and the results were described as being "transient." Press et al., "Monoclonal Antibody 1F5 (Anti-CD20) Serotherapy of Human B-Cell Lymphomas." Blood 69/2:584-591 (1987). A potential problem with this approach is that non-human monoclonal antibodies (eg, murine monoclonal antibodies) typically lack human effector functionality, ie they are unable to, inter alia, mediate complement dependent lysis or lyse human target cells through antibody dependent cellular toxicity or Fc-receptor mediated phagocytosis. Furthermore, non-human monoclonal antibodies can be recognized by the human host as a foreign protein; therefore, repeated injections of such foreign antibodies can lead to the induction of immune responses leading to harmful hypersensitivity reactions. For murine-based monoclonal antibodies, this is often referred to as a Human Anti-Mouse Antibody response, or "HAMA"

response. Additionally, these "foreign" antibodies can be attacked by the immune system of the host such that they are, in effect, neutralized before they reach their target site.

~

WO 94/11026 2149.29 PCT/US93/10953 ~Lymphocytes and lymphoma cells are inherently sensitive to radiotherapy for several reasons: the local emission of ionizing radiation of radiolabeled antibodies may kill cells with or without the target antigen (eg, CD20) in close proximity to antibody bound to the antigen; penetrating radiation may obviatp the problem of limited access to the antibody in bulky or poorly vascularized tumors; and, the total amount of antibody required may be reduced. The radionuclide emits radioactive particles which can damage cellular DNA to the point where the cellular repair mechanisms are unable to allow the cell to continue living; therefore, if the target cells are tumors, the radioactive label beneficially kills the tumor cells. Radiolabeled antibodies, by definition, include the use of a radioactive substance which may require the need for precautions for both the patient (ie possible bone marrow transplantation) as well as the health care provider (ie the need to exercise a high degree of caution when working with the radioactivity).

Therefore, an approach at improving the ability of murine monoclonal antibodies to be effective in the treatment of B-cell disorders has been to conjugate a radioactive label or toxin to the antibody such that the label or toxin is localized at the tumor site. For example, the above-referenced IF5 antibody has been "labeled" with iodine-131 (" 131I") and was reportedly evaluated for biodistribution in two patients. See Eary, J.F. et al., "Imaging and Treatment of B-Cell Lymphoma" J. Nuc. Med. 31 /8:1257-1268 (1990); see also, Press, O.W. et al., "Treatment of Refractory Non-Hodgkin's Lymphoma with Radiolabeled MB-1 (Anti-CD37) Antibody" J. Clin. Onc. 7/8:1027-1038 (1989) (indication that one patient treated with 131I-labeled IF-5 achieved a "partial response");
Goldenberg, D.M. et al., "Targeting, Dosimetry and Radioimmunotherapy of B-Cell Lymphomas with Iodine-131-Labeled LL2 Monoclonal Antibody" J. Clili.. Onc.
9/4:548-564 (1991) (three of eight patients receiving multiple injections reported to have developed a HAMA response); Appelbaum, F.R. "Radiolabeled Monoclonal Antibodies in the Treatment of Non-Hodgkin's Lymphoma"

Hem. /Onc. Clinics of N.A. 5/5:1013-1025 (1991) (review article); Press, O.W.
et al "Radiolabeled-Antibody Therapy of B-Cell Lymphoma with Autologous Bone Marrow Support." New England Journal of Medicine 329 / 17: 1219-12223 (1993) (iodine-131 labeled anti-CD20 Fuitibody IF5 and B1); and Kaininski, M.G.
et al "Radioimmunotherapy of B-Cell Lymphoma with [1311] Anti-B1 (Anti-CD20) Antibody". NEJM329/7 (1993) (iodine-131 labeled anti-CD20 antibody B1;
hereinafter "Kaminski").

Toxins (ie chemotherapeutic agents such as doxorubicin or mitomycin C) have also been conjugated to antibodies. See, for example, PCT published application WO 92/07466 (published May 14, 1992).

"Chimeric" antibodies, ie antibodies which comprise portions from two or more different species (eg, mouse and human) have been developed as an alternative to "conjugated" antibodies. For example, Liu, A.Y. et al., "Production of a Mouse-Human Chimeric Monoclonal Antibody to CD20 with Potent Fc-Dependent Biologic Activity" J. Immun. 139/10:3521-3526 (1987), describes a mouse/human chimeric antibody directed against the CD20 antigen. See also, PCT Publication No. WO 88/04936. However, no information is provided as to the ability, efficacy or practicality of using such chimeric antibodies for the treatment of B cell disorders in the reference. It is noted that in vitro functional assays (eg complement dependent lysis ("CDC"); antibody dependent cellular cytotoxicity ("ADCC"), etc.) cannot inherently predict the in vivo capability of a chimeric antibody to destroy or deplete target cells expressing the specific antigen.
See, for example, Robinson, R.D. et al., "Chimeric mouse-human anti-carcinoma antibodies that mediate different anti-tumor cell biological activities,"
Hunz.
Antibod. Hybridomas 2:84-93 (1991) (chimeric mouse-human antibody having -~-undetectable ADCC activity). Therefore, the potential therapeutic efficacy of chimeric antibody can only truly be assessed by in vivo experimentation.

What is needed, and what would be a great advance in the art, are therapeutic approaches targeting the CD20 antigen for the treatment of B cell lymphomas in primates, including, but not limited to, humans.

C. SUMMARY OF THE INVENTION

Disclosed herein are therapeutic methods and uses designed for the treatment of B cell disorders, and in particular, B cell lymphomas. These protocols are based upon the administration of immunologically active chimeric anti-CD20 antibodies for the depletion of peripheral blood B cells, including B cells associated with lymphoma; administration of radiolabeled anti-CD20 antibodies for targeting localized and peripheral B cell associated tumors; and administration of chimeric anti-CD20 antibodies and radiolabeled anti-CD20 antibodies in a cooperative therapeutic strategy. Another aspect of the invention comprises commercial packages of such chimeric anti-CD20 antibodies and radiolabeled antibodies together with instructions for such uses.

In one aspect, the invention provides an isolated monoclonal antibody, wherein the antibody comprises a light chain variable region comprising amino acid. residues 23 to 128 of SEQ ID NO:4 and a heavy chain variable region comprising amino acid residues 20 to 140 of SEQ ID NO:6.
In another aspect, the invention provides an immunologically active chimeric anti-CD20 antibody, wherein the antibody possesses substantially the same B-cell depleting activity and has specificity to the same epitope of CD20 as an anti-CD20 antibody comprising the heavy chain and light chain polypeptides encoded by the heavy and light chain inserts in the vector nucleotide sequence shown in SEQ
ID NO:2.

In another aspect, the invention provides a host cell comprising nucleic acid sequences encoding the light chain and the heavy chain of an immunologically active chimeric anti-CD20 antibody, wherein the sequence encoding the light chain comprises a nucleotide sequence encoding amino acid residues 23 to 128 of SEQ ID NO:4, and the sequence encoding the heavy chain comprises a nucleotide sequence encoding amino acid residues 20 to 140 of SEQ ID
N0:6.

In another aspect, the invention provides a method of producing a chimeric anti-CD20 antibody comprising: (a) culturing a host cell as described above under conditions to produce the chimeric anti-CD20 antibody and. (b) harvesting the chimeric anti-CD20 antibody.

In another aspect, the invention provides a chimeric anti-CD20 antibody made as described above.
9a = 51490-1 D. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagrammatic representation of a tandem chimeric antibody expression vector useful in the production of immunologically active chimeric anti-CD20 antibodies ("TCAE8");

Figures 2A through 2F are the nucleic acid sequence of the vector of Figure 1;

Figures 3A through 3F are the nucleic acid sequence of the vector of Figure 1 further comprising murine light and heavy chain variable regions ("anti-CD20 in TCAE8") (also set forth as SEQ ID NO:2);
9b Figure 4 shows the nucleic acid (SEQ ID NO:3) and amino acid (SEQ ID NO:4) sequences (including CDR and fframework regions) of murine variable region light chain derived from murine anti-CD20 monoclonal antibody 2B8;

Figure 5 shows the nucleic acid (SEQ ID NO:5) and amino acid (SEQ ID NO:6) sequences (including CDR and framework regions) of murine variable region heavy chain derived from murine anti-CD20 monoclonal antibody 2B8;

Figure 6 are flow cytometry results evidencing binding of fluorescent-labeled human Clq to chimeric anti-CD20 antibody, including, as controls labeled Clq;
labeled Clq and murine anti-CD20 monoclonal antibody 2B8; and labeled Clq and human IgGl,k;

Figure 7 represents the results of complement related lysis comparing chimeric anti-CD20 antibody and murine anti-CD20 monoclonal antibody 2B8;

Figure 8 represents.the results of antibody mediated cellular cytotoxicity with in viuo human effector cells comparing chimeric anti-CD20 antibody and 2B8;

Figure 9A, 9B and 9C provide the results of non-human primate peripheral blood B lymphocyte depletion after irifusion of 0.4 mg/kg (A); 1.6 mg/kg (B); and 6.4 mg/kg (C) of immunologically active chimeric anti-CD20 antibody;

Figure 10 provides the results of, iizter alia, non-human primate peripheral blood B lymphocyte depletion after infusion of 0.01 mg/kg of immunologically active chimeric anti-CD20 antibody;

Figure 11 provides results of the tumoricidal impact of Y2B8 in a mouse xenographic model utilizing a B cell lymphoblastic tumor;

FiRura 12 providec results of tho tumoriaidsl ampact of C2BS in aTnousQ
xenographic model utilizing a B cell lymphoblasti.c tumor;

Figure 13 provides results of the tumoricidal impact of a combination of Y2B8 and C2B8 in a mouse xenographic model utilizing a B cell lymphoblastic tumor;
and Figures 14A and 14B provide results from a Phase I/II clinical analysis of evidencing B-cell population depletion over time for patients evidencing a partial remission of the disease (14A) and a minor remission of the disease (14B).

E. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Generally, antibodies are composed of two light chains and two heavy chain molecules; these chains form a general "Y" shape, with both light and heavy chains forming the arms of the Y and the heavy chains forming the base of the Y.

Light and heavy chains are divided into domains of structural and functional homology. The variable domains of both the light ("VL") and the heavy ("VH") chains determine recognition and specificity. The constant region domains of light ("CL") and heavy ("CH") chains confer important biological properties, eg antibody chain association, secretion, transplacental mobility, Fc receptor binding complement binding, etc. The series of events leading to immunoglobulin gene expression in the antibody producing cells are complex.
The variable domain region gene sequences are located in separate germ line gene segments referred to as "VI-I," "D," and "Jl-I," or "VL" and "JL." These gene segments are joined by DNA i=earrangeinents to forin the complete V regions expressed in heavy and liglit chains, respectively. The rearranged, joiiied V

WO 94/11026 2 14 9 3 2 9 PCr/US93/10953 segments (VLJL and VH-D-JH) then encode the complete variable regions or antigen binding domains of light and heavy chains, respectively.

Serotherapy of human B cell lymphomas usiiig an anti-CD20 murine monoclonal antibody (1F5) has been described by Press et al., (69 Blood 584, 1987, supra.);
the reported therapeutic responses, unfortunately, were transient.
Additionally, 25% of the tested patients reportedly developed a human anti-mouse antibody (HAMA) response to the serotherapy. Press et al., suggest that these antibodies, conjugated to toxins or radioisotopes, might afford a more lasting clinical benefit than the unconjugated antibody.

Owing to the debilitating effects of B cell lymphoma and the very real need to provide viable treatment approaches to this disease, we have embarked upon different approaches having a particular antibody, 2B8, as the common link between the approaches. One such approach advantageously exploits the ability of mammalian systems to readily and efficiently recover peripheral blood B
cells;
using this approach, we seek to, in essence, purge or deplete B cells in peripheral blood and lymphatic tissue as a means of also removing B cell lymphomas. We accomplish this by utilization of, iiater alia, immunologically active, chimeric anti-CD20 antibodies. In another approach, we seek to target tumor cells for destruction with radioactive labels.

As used herein, the term "anti-CD20 antibody" is an antibody which specifically recognizes a cell surface non-glycosylated phosphoprotein of 35,000 Daltons, typically designated as the human B lymphocyte restricted differentiation antigen Bp35, commonly referred to as CD20. As used herein, the term "chimeric" when used in reference to anti-CD20 antibodies, encompasses antibodies which are most preferably derived using recombinant deoxyribonucleic acid techniques and wliich comprise both human (including lmmunologically "related" species, eg, chimpanzee) and non-human components: the constant region of the chimeric antibody is most preferably substantially identical to the constant region of a natural human antibody; the variable region of the chimeric antibody is most preferably derived from a non-human source and has the desired antigenic and specificity to the CD20 cell surface antigen. The non-human source can be any vertebrate source which can be used to generate antibodies to a human CD20 cell surface antigen or material comprising a human CD20 cell surface antigen. Such non-human source includes, but is not limited to, rodents (eg, rabbit, rat, mouse, etc.) and non-human primates (eg, Old World Monkey, Ape, etc.). Most preferably, the non-human component (variable region) is derived from a murine source. As used herein, the phrase "immunologically active" when used in reference to chimeric anti-CD20 antibodies, means a chimeric antibody which binds human Clq, mediates complement dependent lysis ("CDC") of human B lymphoid cell lines, and lyses human target cells through antibody dependent cellular cytotoxicity ("ADCC"). As used herein, the phrases "indirect labeling" and "indirect labeling approach" both mean that a chelating agent is covalently attached to an antibody and at least one radionuclide is inserted into the chelating agent.
Preferred chelating agents and radionuclides are set forth in Srivagtava, S.C. and Mase, R.C., "Progress in Research on Ligands, Nuclides and Techniques for Labeling Monoclonal . .Z'~

~..
ctntibodies," Nuc1. Med. Bio. 18/6: 589-603 (1991) ("Srivagtava"). A particularly preferred chelating agent is 1-isothiocycmatobenzyl-3-methyldiothelene triaminepent acetic acid ("MX-DTPA"); particularly preferred radionuclides for indirect labeling include indium [111] and yttrium [90]. As used herein, the phrases "direct labeling" and "direct labeling approach"
both mean that a radionuclide is covalently attached directly to an antibody (typically via an amino acid residue). Preferred radionuclides are provided in Srivagtava; a particularly preferred radionuclide for direct labeling is iodine [131]
covalently attached via tyrosine residues. The indirect labeling approach is particularly preferred.

The therapeutic approaches disclosed herein are based upon the ability of the immune system of primates to rapidly recover, or rejuvenate, peripheral blood B cells. Additionally, because the principal immune response of primates is occasioned by T cells, when the immune system has a peripheral blood B cell deficiency, the need for "extraordinary" precautions (i.e. patient isolation, etc.) is not necessary. As a result of these and other nuances of the immune systems of primates, our therapeutic approach to B cell disorders allows for the purging of peripheral blood B cells using immunologically active chimeric anti-CD20 antibodies.

Because peripheral blood B cell disorders, by definition, can indicate a necessity for access to the blood for treatment, the route of administration of the immunologically active chimeric anti-CD20 antibodies and radiolabeled anti-CD20 antibodies is preferably parenteral; as used herein, the term "parenteral"
includes intravenous, intramuscular, subcutaneous, rectal, vaginal or intraperitoneal administration. Of these, intravenous administration is most preferred.

The immunologically active chimeric anti-CD20 antibodies and radiolabeled anti-CD20 antibodies will typically be provided by standard technique within a pharmaceutically acceptable buffer, for example, sterile saline, sterile buffered water, propylene glycol, combination of the foregoing, etc. Methods for preparing parenterally administerable agents are described in Pharmaceutical Carriers & Formulations, Martin, Remington's Pharmaceutical Sciences, 15th Ed. (Mack Pub. Co., Eason, PA
1975).

14a .L1 WO 94/11026 2 ' 4(, 3 Z 9 PCr/US93/10953 The specific, therapeutically effective amount of immunologically active chimeric anti-CD20 antibodies useful to produce a unique therapeutic effect in any given patient can be determined by standard techniques well known to those of ordinary skill in the art.

Effective dosages (ie therapeutically effective amounts) of the immunologically active chimeric anti-CD20 antibodies range from about 0.001 to about 30 mg/kg body weight, more preferably from about 0.01 to about 25 mg/kg body weight, and most preferably from about 0.4 to about 20.0 mg/kg body weight. Other dosages are viable; factors influencing dosage include, but are not limited to, the severity of the disease; previous treatment approaches; overall health of the patient; other diseases present, etc: The skilled artisan is readily credited with assessing a particular patient and determining a suitable dosage that falls within the ranges, or if necessary, outside of the ranges.

Introduction of the immunologically active chimeric anti-CD20 antibodies in these dose ranges can be carried out as a single treatment or over a series of treatments. With respect to chimeric antibodies, it is preferred that such introduction be carried out over a series of treatments; this preferred approach is predicated upon the treatment methodology associated with this disease. While not wishing to be bound by any particular theory, because the immunologically active chimeric anti-CD20 antibodies are both immunologically active and bind to CD20, upon initial introduction of the immunologically active chimeric anti-CD20 antibodies to the individual, peripheral blood B cell depletion will begin;
we have observed a nearly complete depletion within about 24 hours post treatment infusion. Because of this, subsequent introduction(s) of the immunologically active chimeric anti-CD20 antibodies (or radiolabeled anti-CD20 antibodies) to the patient is presumed to: a) clear remaining peripheral blood B cells; b) begin B cell depletion from lymph nodes; c) begin B cell depletion -1.5-WO 94/11026 2 ~4 9 3 2 9 PCT/US93/10953 from other tissue sources, eg, bone marrow, tumor, etc. Stated again, by using repeated introductions of the immunologically active chimeric anti-CD20 antibodies, a series of events take place,,each event being viewed by us as important to effective treatment f the disQRae. The first "event" then, cen be viewed as principally directed to substantially depleting the patient's peripheral blood B cells; the subsequent "events" can be viewed as either principally directed to simultaneously or serially clearing remaining B cells from the system clearing lymph node B cells, or clearing other tissue B cells.

In effect, while a single dosage provides benefits and can be effectively utilized for disease treatment/management, a preferred treatment course can occur over several stages; most preferably, between about 0.4 and about 20 mg/kg body weight of the immunologically active chimeric anti-CD20 antibodies is introduced to the patient once a week for between about 2 to 10 weeks, most preferably for about 4 weeks.

With reference to the use of radiolabeled anti-CD20 antibodies, a preference is that the antibody is non-chimeric; this preference is predicted upon the significantly longer circulating half-life of chimeric antibodies vis-a-vis murine antibodies (ie with a longer circulating half-life, the radionuclide is present in the patient for extended periods). However, radiolabeled chimeric antibodies can be beneficially utilized with lower milli-Curries ("mCi") dosages used in conjunction with the chimeric antibody relative to the murine antibody. This scenario allows for a decrease in bone marrow toxicity to an acceptable level, while maintaining therapeutic utility.

A variety of radionuclides are applicable to the present invention and those skilled in the art are credited with the ability to readily determine which radionuclide is most appropriate under a variety of circumstances. For example, iodine (1311 is a well known radionuclide used for targeted immunotherapy.
:owever, the clinical usefulness of iodine 11311 can be limited by several factors including: eight-day physical half-life; dehalogenation of iodinated antibody both in the blood and at tumor sites; and emission characteristics (e.g. large gamma component) which can be suboptim3l for localized dose deposition in tumor.

With the advent of superior chelating agents, the opportunity for att:tching metal chelating groups to proteins has increased the opportunities to utilize other radionuclides such as indium (131] and yttrium (90]. Yttrium [90] provides :everal benefits for utilization in radioimmunotherapeutic applications: the hour half-life of yitrium [901 is long enough to allow antibody accumulation by tumor and, unlike eg iodine (131], yttrium 1901 is a pure beta emitter of high energy with no accompanying gamma irradiation in its decay, with a range in tissue of 100 to 1000 cell diameters. Furtherznore, the minimal amount of penetrating radiation allows for outpatient administration of yttriuin [90]-labeled antibodies. Furtherznore, internalization of labeled antibody is not required for cell killing, and the local emission of ionizing radiation should be lethal for adjacent tumor cells lacking the target antigen.

One non-therapeutic limitation to yttrium [90] is based upon the absence of significant gamma radiation making imaging therewith difncult. To avoid this problem, a diagnostic "imaging" radionuclide, such as indium [111], can be utilized for determining the location and relative size of a tumor prior to the administration of therapeutic does of yttrium (90]-labeled anti-CD20. Indium [III] is particularly preferred as the diagnostic radionuclide because:
between about 1 to about lOmCi can be safely administered without detectable toxicity;
and the imaging data is generally predictive of subsequent yttrium (90]-labeled antibody distribution. NIost imaging studies utilize 5mCi indium [111]-labeled antibody because this dose is both safe and has increased imaging eEilciency compared with lower doses, with optimal imaging occurz=ing at three to six days -1:-after antibody administration. See, for exainple, Murray J.L. , 26 J. Nuc.
Med.
3328 (1985) and Carraguillo, J.A. et al , 26 J. Nuc. Med. 67 (1985).

Effective ainpcle treatment dosages (ie theriapeiatically effective amounts) of yttrium [90] labeled anti-CD20 antibodies range.from between about 5 and about 75mCi, more preferably between about 10 and about 40mCi. Effective single treatment non-marrow ablative dosages of iodine [131] labeled anti-CD20 antibodies range from between about 5 and about 70mCi, more preferably between about 5 and about 40mCi. Effective single treatment ablative dosages (ie may require autologous bone marrow transplantation) of iodine [131]
labeled anti-CD20 antibodies range from between about 30 and about 600mCi, more preferably between about 50 and less than about 500mCi. In conjunction with a chimeric anti-CD20 antibody, owing to the longer circulating half life vis-a-vis murine antibodies, an effective single treatment non-marrow ablative dosages of iodine [131] labeled chimeric anti-CD20 antibodies range from between about 5 and about 40mCi, more preferably less than about 30mCi. Imaging criteria for, eg the indium [111] label, are typically less than about 5mCi.

With respect to radiolabeled anti-CD20 antibodies, therapy therewith can also occur using a single therapy treatment or using multiple treatments. Because of the radionuclide component, it is preferred that prior to treatment, peripheral stem cells ("PSC") or bone marrow ("BM") be "harvested" for patients experiencing potentially fatal bone marrow toxicity resulting from radiation.
BM
and/or PSC are harvested using standard techniques, and then purged and frozen for possible reinfusion. Additionally, it is most preferred that prior to treatment a diagnostic dosimetry study using a diagnostic labeled antibody (eg using indium [111]) be conducted on the patient, a purpose of which is to ensure that the. therapeutically labeled antibody (eg using yttrium [90]) will not become unnecessarily "concentrated" in any normal organ or tissue.

Chimeric mouse/human antibodies have been described. See, for examp:e.
Morrison, S.L. et al., PNAS 81:6851-6854 (November 1984); European Patent Publication No. 173494; Beulianne, C.L. et al., Nature 312:642 (December 1984);
Neubeiger, M.S. et al., Nature 314:268 (March 1985); European Patent Publication No. 125023; Tan et al., J. Immunol. 135:8564 (November 1955); Sun, L.K. et al., Hybridoma 511:517 (19E6); Sahagan et a1., J. Immunol. 137:.1066-1074 (1986). See generally, Muron, Vature 312:597 (December 1984); Dickson, Genetic Engineering News 5 l3 (March 1985); Marx, Science 229 455 (Aur _st 1985); and Morrison Science 229:1202-1207 (September 1985). Robinson et al., in PCT Publication Number WO 88/04936 describe a chimeric antibody wit'.~h& hum.-In constant region and murine variable region, having specificity to an epitope of CD20; the murine portion of the chirneric antibody of the Robinson references is derived from the 2H7 mouse monoclonal antibody (gamma 2b, kappa). While the reference notes that the described chimeric antibody is a "prime candidate"
for the treatment of B cell disorders, this statement can be viewed as no more thnn a suggestion to those in the art to determine whether or not this suggestion is accurate for this particular antibody, particularly because the reference lacks any data to support an assertion of therapeutic efiectiveness, and importantly, data using higher order mammals such as primates or humans.
Methodologies for generating chimeric antibodies are available to those in the art. For example, the light and heavy chains can be expressed separately, using, for example, immunoglobulin light chain and immunoglobulin heavy chains in separate plasmids. These can then be purified and assembled in uitro into complete antibodies; methodologies for accomplishing such assembly have been described. See, for example, Scharff, M., Harvey Lectures 69:125 (1974). In vitro reaction parameters for the formation of IgG antibodies from reduced isolated light and heavy chains have also been described. See, for example, Beychok, S., .19.

.:e11s of Immunoglobulin Synthesis, Academic Press, New York, p.
69, 1979. Co-expression of light and heavy chains in the same cells to achieve intracellular association and linkage of heavy and light chains into complete H2L2 IgG antibodies is also possible. Such co-expression can be accomplished using either the same or different plasmids in the same host cell.

Another approach, and one which is our most preferred approach for developing a chimeric non-human/human anti-CD20 antibody, is based upon utilization of an expression vector which includes, ab initio, DNA encoding heavy and light chain constant regions from a human source. Such a vector allows for inserting DNA
encoding non-human variable region such that a variety of non-human anti-CD20 antibodies can be generated, screened and analyzed for various characteristics (eg type of binding specificity, epitope binding regions, etc.); thereafter, cDNA
encoding the light and heavy chain variable regions from a preferred or desired anti-CD20 antibody can be incorporated into the vector. We refer to these types of vectors as-Tandem Chimeric Antibody Expression ("TCAE") vectors. A most preferred TCAE vector which was used to generate immunologically active chimeric anti-CD20 antibodies for therapeutic treatment of lymphomas is TCAE 8. TCAE 8 is a derivative of a vector owned by the assignee of this patent document, referred to as TCAE 5.2 the difference being that in TCAE 5.2, the translation -0~

initiation start site of the dominant selectable marker (neomycin phosphostransferase, "NEO") is a consensus Kozak sequence, while for TCAE 8, this region is a partially impaired consensus Kozak sequence. Details regarding the impact of the initiation start site of the dominant selectable marker of the TCAE vectors (also referred to as "ANEX vector") vis-a-vis protein expression are disclosed in detail elsewhere.

20a L'~

WO 94/11026 2149329 PC.'f/US93/10953 TCAE 8 comprises four (4) transcriptional cassettes, and these are in tandem order, ie a human immunoglobulin light chain absent a variable region; a human immunoglobulin heavy chain absent a variable region; DHFR; and NEO. Each transcri.ptional cassette contains its own eukaryotic promotor and polyadenylation region (reference is made to Figure 1 which is a diagramiliatic representation of the TCAE 8 vector). Specifically:

1) the CMV promoter/enhancer in front of the immunoglobulin heavy chain is a truncated version of the promoter/enhancer in front of the light chain, from the Nhe I site at -350 to the Sst I site at -16 (see, 41 Cell 521, 1985).

2) a human immunoglobulin light chain constant region was derived via amplification of cDNA by a PCR reaction. In TCAE 8, this was the human immunoglobulin light chain kappa constant region (Kabat numbering, amino acids 108-214, allotype Km 3, (see, Kabat, E.A. "Sequences of proteins of immunological interest," NIH Publication, Fifth Ed. No. 91-3242, 1991)), and the human immunoglobulin heavy chain gamma 1 constant region (Kabat numbering amino acids 114-478, allotype Gmla, Gmlz). The light chain was isolated from normal human blood (IDEC Pharmaceuticals Corporation, La Jolla, CA); RNA therefrom was used to synthesize cDNA which was then amplified using PCR techniques (primers were derived vis-a-vis the consensus from Kabat). The heavy chain was isolated (using PCR techniques) from cDNA
prepared from RNA which was in turn derived from cells transfected with a human IgGl vector (see, 3 Prot. Eng. 531, 1990; vector pNy162). Two amino acids were changed in the isolated human IgG1 to match the consensus amino acid sequence from Kabat, to wit: amino acid 225 was changed from valine to alanine (GTT to GCA), and amino acid 287 was changed from methionine to lysine (ATG
to AAG);

3) The human immunoglobulin light and heavy chain cassettes contain svnthetic signal sequences for secretion of the immunoglobulin chains;

4) The human immunoglobulin light and heavy chain cassettes contain specific DNA restriction sites which allow for insertion of light dnd heavy immunoglobulin variable regions which maintain the transitional reading frame and do not alter the amino acids normally found in immunoglobulinchains;

5) The DHFR cassette contained its own eukaryotic promoter (mouse beta globin major promoter, "BETA") and polyadenylation region (bovine growth hormone polyadenylation, "BGH"); and 6) The NEO cassette contained its own eukaryotic promoter (BETA) and polyadenylation region (SV40 early polyadenylation, "SV").

lj With respect to the TCAE 8 vector and the NEO cassette, the Kozak region w1s 1 partially impaired consensus Kozak sequence (which included an upstream Cla I
site):

Clal -3= +1 C-GGAGCTTGG ATCGAT ccTct ATG Gtt (SEQ ID NO:7) (In the TCAE 5.2 vector, the change is between the ClaI and ATG regions, to wit:
ccAcc.) The complete sequence listing of TCAE 8 (including the specific components of the four transcriptional cassettes) is set forth in Figure 2 (SEQ. ID. NO. 1).

-'d2 As will be appreciated by those in the art, the TCAE vectors benefxcially allo-,v for substantially reducing the time in generating the immunologically active cliiineric anti-CD20 antibodies. Generation and isolation of non-human light and heavy chain variable regions, followed by incorporation thereof within the huinan light chain coi.lstant transcriptional cassette and human heavy chain constant tr. anscriptional cassette, allows for production of iznmunolodically active chimeric anti-CD20 antibodies.

We have derived a uiost preferred non-human variable region with specificity to the CD20 antigen using a murine source and hybridoma technology. Using pulymerase chain reaction ("PCR") techniques, the murine light and heavy variable regions were clotied directly into the TCAE 8 vector-this is the niost preferred route fur incorporation of the non-human variable region into the TCAE vectot=. This preference is principally predicated upon the efficiency of the PCR reactioir and the accuz-acy of iueic;rtion. However, other equivalent procedures for accoznpliat,ino this task are available. For eban-Aple, using TCAE

8 (or axi equivalent vector), the sequence of the variable region of a non-human aiiti-CD20 antibody can be obtained, followed by oligonucleotide synthesis of portions of the sequence or, if appropriate, the entire sequence; thereafter, the portions or the entire synthetic sequence can be inserted into the appropriate lucations within thf-, vector. Those skilled in the art are credited with the ability to accomplish this task.

Our most preferred immunologically active chimeric anti-CD20 antibodies were derived from utilization of TCAE 8 vector which included murine variable regions derived from monoclonal antibody to CD20; this antibody (to be discussed in detail, infra), is referred to as "2B8." The complete sequence of the variable regions obtained from 2B$ in TCAE 8("anti-CD20 in TCAE 8") is set f.ortli in Figure 3(SEQ. ID. NO. 2).

WO 94/11026 2149329 PC'I'/US93/10953 The host cell line utilized for protein expression is most preferably of mammalian origin; those skilled in the art are credited with ability to preferentially determine particular host cell lines which are beAt suited for the desired gene product to be expressed therein. Exemplary host cell lines include, but are not limited to, DG44 and DUXBII (Chinese Hamster Ovary lines, DHFR minus), HELA (human cervical carcinoma), CVI (monkey kidney line), COS (a derivative of CVI with SV40 T antigen), R1610 (Chinese hamster fibroblast) BALBC/3T3 (mouse fibroblast), HAK (hamster kidney line), SP2/O (mouse myeloma), P3x63-Ag3.653 (mouse myeloma), BFA-IcIBPT (bovine endothelial cells), RAJI (human lymphocyte) and 293 (human kidney). Host cell lines are typically available from commercial services, the American Tissue Culture Collection or from published literature.

Preferably the host cell line is either DG44 ("CHO") or SP2/O. See Urland, G.
et al., "Effect of gamma rays and the dihydrofolate reductase locus: deletions and inversions." Som. Cell & Mol. Gen. 12 / 6:555-566 (1986), and Shulman, M. et al., "A better cell line for making hybridomas secreting specific antibodies."
Nature 276:269 (1978), respectively. Most preferably, the host cell line is DG44.

Transfection of the plasmid into the host cell can be accomplished by any technique available to those in the art. These include, but are not limited to, transfection (including electrophoresis and electroporation), cell fusion with enveloped DNA, microinjection, and infection with intact virus. See, Ridgway, A.A.G. "Mammalian Expression Vectors." Chapter 24.2, pp. 470-472 Vectors, Rodriguez and Denhardt, Eds. (Butterworths, Boston, MA 1988). Most preferably, plasmid introduction into the host is via electroporation.

F. EXAMPLES 2 149 3 2 9 The following examples are not intended, nor are they to be construed, as limiting the invention. The examples are intended to evidence: dose-imaging using a radiolabeled anti-CD20 antibody ("I2B8"); radiolabeled anti-CD20 antibody ("Y2B8"); and immunologically active, chimeric anti-CD20 antibody ("C2B8") derived utilizing a specific vector ("TCAE 8") and variable regions derived from murine anti-CD20 monoclonal antibody ("2B8").

I. R.ADIOLABELED ANTI-CD20 ANTIBODY 2B8 A Anti-CD20 Monoclonal Antibody (Murine) Production ("2B8") BALB/C mice were repeatedly immunized with the human lymphoblastoid cell line SB (see, Adams, R.A. et al., "Direct implantation and serial transplantation of human acute lymphoblastic leukemia in hamsters, SB-2."

Can Res 28:1121-1125 (1968); this cell line is available from the American Tissue Culture Collection, Rockville, MD., under ATCC accession number ATCC CCL
120), with weekly injections over a period of 3-4 months. Mice evidencing high serum titers of anti-CD20 antibodies, as determined by inhibition of known CD20-specific antibodies (anti-CD20 antibodies utilized were Leu 16, Beckton Dickinson, San Jose, CA, Cat. No. 7670; and Bl, Coulter Corp., Hialeah, FL, Cat.
No. 6602201) were identified; the spleens of such mice were then removed.
Spleen cells were fused with the mouse myeloma SP2/0 in accordance with the protocol described in Einfeld, D.A. et al., (1988) EMBO 7:711 (SP2/0 has ATCC
accession no. ATCC CRL 8006).

Assays for CD20 specificity were accomplished by radioimmunoassay. Briefly, purified anti-CD20 Bl was radiolabeled with 1125 by the iodobead method as described in Valentine, M.A. et al., (1989) J. Biol. Chem. 264:11282. (1125 rZodium Iodide, ICN, Irvine, CA, Cat. No. 28665H). Hybridomas were screened by co-incubation of 0.05 ml of media from each of the fusion wells together*
with 0.05 ml of 1125 labeled anti-CD20 B1(10 ng) in 1% BSA, PBS (pH 7.4), and 0.5 ml of the same buffer containing 100,000 SB cells. After incubation for 1 hr at room temperature, the cells were harvested by transferring to 96 well titer plates (V&P Scientific, San Diego, CA), and washed thoroughly. Duplicate wells containing unlabeled anti-CD20 B1 and wells containing no inhibiting antibody were used as positive and negative controls, respectively. Wells containing greater than 50% inhibition were expanded and cloned. The antibody demonstrating the highest inhibition was derived from the cloned cell line designated herein as "2B8."

B. Preparation of 2B8-MX-DTPA Con,tugate i. IyLX-D.~Q

Carbon-14-labeled 1-isothiocyanatobenzyl-3-methyldiethylene triarninepentaacetic acid ("carbon-14 labeled MX-DTPA") was used as a chelating agent for conjugation of radiolabel to 2B8. Manipulations of MX-DTPA were conducted to maintain metal-free conditions, ie metal-free reagents were utilized and, when possible, polypropylene plastic containers (flasks, beakers, graduated cylinders, pipette tips) washed with AlconoX and rinsed with Milli-Q*water, were similarly utilized. MX-DTPA was obtained as a dry solid from Dr. Otto Gansow (National Institute of Health, Bethesda, MD) and stored desiccated at 4 C
(protected from light), with stock solutions being prepared in Milli-Q*water at a concentration of 2-5mM, with storage at -70 C. MX-DTPA was also obtained from Coulter Immunology (Hialeah, Florida) as the disodium salt in water and stored at -70 C.

*Trade-mark .26-ii. Preoaration of 2B8 Purified 2B8 was prerared for conjugation with MX-DTPA by transferring the antibody into met:::-free 50mM bicine-NaOff, pH 8.6, containing 150 m.M NaCI, using repetitive bu::er exchange with CENTRICON 30T' spin filters (30,000D, MWCO; Amicon). Generally, 50-200 EtL of protein (10 mg/nl) was added to the filter unit, followed by 2 mL of bicine buffzr. The filter was centrifuged at 4 C in a Sorvall* SS-34 rotor (6,000 rpm, 45 min.). Retentate volume was approximately 50-100 uL; this process was repeated twice using the same filter. Retentate was transfez: ed to a polypropylene 1.5 mL screw cap tube, assayed for protein, diluted to 10.0 mg/mL and stored at 4 C until utilized;

protein was similarly transferred into 50 mM sodium citrate, pH 5.5, containing 150 mM NaCl and 0.05% sodium azide, using the foregoing protocol.

iii. Coniueation of 2B8 with M-X-DTPA

Conjugation of 2B8 with iYtX-DTPA was performed in polypropylene tubes at ambient temperature. Frozen MX-DTPA stock solutions were thawed immediately prior to use. 50-200 mL of protein at 10 mg/mL were reacted with MX-DTPA at a molar ratio of MX-DTPA-to-2B8 of 4:1. Reactions were initiated by adding the Mx-DTPA stock solution and gently mixing; the conjugation was allowed to proceed overnight (14 to 20 hr), at ambient temperature. Unreacted ?vlX-DTPA was removed from the conjugate by dialysis or repetitive ultrafiltration, as described above in Example I.B.ii, into metal-free normal saline (0.9% w/v) containing 0.05% sodium azide. The protein concentration was adjusted to 10 mg/mL and stored at 4'C in a polypropylene tube until radiolabeled.

iv. Determination of MX-DTPA Incorporation MX-DTPA incorporation was deterinined by scintillation counting and comparing the value obtained with the purified conjugate to the specific *Trade-mark .27.

activity of the carbon-[14]-labeled MX-DTPA. For certain studies, in which non-radioactive MX-DTPA (Coulter Immunology) was utilized, MX-DTPA

incorporation was assessed by incubating, the conjugate with an excess of a radioactive carrier solution of yttrium-[90] af known concentration and specific activity.

A stock solution of yttrium chloride of known concentration was prepared in metal-free 0.05 N HCl to which carrier-free yttrium-[90] (chloride salt) was added. An aliquot of this solution was analyzed by liquid scintillation counting to determine an accurate specific activity for this reagent. A volume of the yttrium chloride reagent equal to 3-times the number of mols of chelate expected to be attached to the antibody, (typically 2 mol/mol antibody), was added to a polypropylene tube, and the pH adjusted to 4.0-4.5 with 2 M sodium acetate.
Conjugated antibody was subsequently added and the mixture incubated 15-30 min. at ambient temperature. The reaction was quenched by adding 20 mM
EDTA to a final concentration of 1 mM and the pH of the solution adjusted to approximately pH 6 with 2M sodium acetate.

After a 5 min. incubation, the entire volume was purified by high-performance, size-exclusion chromatography (described infra). The eluted protein-containing fractions were combined, the protein concentration determined, and an aliquot assayed for radioactivity. The chelate incorporation was calculated using the specific activity of the yttrium-[90] chloride preparation and the protein concentration.

v. Immunoreactivity of 2B8-MX-DTPA

The immunoreactivity of conjugated 2B8 was assessed using whole-cell ELISA. Mid-log phase SB cells were harvested from culture by centrifugation and washed two times with 1X HBSS. Cells were diluted to 1-2 X

106 cells/mL in HBSS and aliquoted into 96-well polystyrene microtiter plates at 50,000-100,000 cells/well. The plates were dried under vacuum for 2 h. at 40-45 C to fix the cells to the plastic; plates were stored dry at -20 C until utilized.
For assay, the plates were warmed to ambient temperature immediately before use, then blocked with 1X PBS, pH 7.2-7.4 containing 1% BSA (2 h). Samples for assay were diluted in 1X PBS/1% BSA, applied to plates and serially diluted (1:2) into the same buffer. After incubating plates for 1 h. at ambient temperature, the plates were washed three times with 1X PBS. Secondary antibody (goat anti-mouse IgG1-specific HRP conjugate 50 L) was added to wells (1:1500 dilution in 1X PBS/1% BSA) and incubated 1 h. at ambient temperature. Plates were washed four times with 1X PBS followed by the addition of ABTS substrate solution (50 mM sodium citrate, pH 4.5 containing 0.01% ATBS and 0.001%
H202). Plates were read at 405 nm after 15-30 min. incubation. Antigen-negative HSB cells were included in assays to monitor non-specific binding.

Immunoreactivity of the conjugate was calculated by plotting the absorbance values vs. the respective dilution factor and comparing these to values obtained using native antibody (representing 100% immunoreactivity) tested on the same plate; several values on the linear portion of the titration profile were compared and a mean value determined (data not shown).

vi. Preparation of Indium-[1111-Labeled 2B8-MX-DTPA ("12B8") Conjugates were radiolabeled with carrier-free indium-[111]. An aliquot of isotope (0.1-2 mCi/mg antibody) in 0.05 M HCL was transferred to a polypropylene tube and approximately one-teiith volume of metal-free 2 M HCl added. After incubation for 5 min., metal-free 2 M sodium acetate was added to adjust the solution to pH 4.0-4.4. Approximately 0.5 mg of 2B8-MX-DTPA was added from a stock solution of 10.0 mg/mL DTPA in normal saline, or 50 mM
sodium citrate/150 mM NaCl containing 0.05% sodium azide, and the solution gently mixed immediately. The pH solution was checked with pH paper to verify a value of 4.0-4.5 and the mixture incubated at ambient temperature for 15-30 min. Subsequently, the reaction was quenched by adding 20 mM EDTA to a final concentration of 1 mM and the reaction mixture was adjusted to approximately pH 6.0 using 2 M sodium acetate.

After a 5-10 min. incubation, uncomplexed radioisotope was removed by size-exclusion chromatography. The HPLC unit consisted of Waters iViodel 6000 ot-TosoHaas Ivlodel TSK-6110 solvent delivery system fitted, respectively, with a Waters U6K or Rheodyne 700 injection valve. Chromatographic separations were performed using a gel permeation column (BioRad SEC-250; 7.5 x 300 mnl or comparable TosoHaas column) and a SEC-250 guard column (7.5 x 100 mm).
The system was equipped with a fraction collector (Pharmacia Frac200) and a UV monitor fitted with a 280 nm filter (Pharmacia model UV-1). Samples were applied and eluted isocratically using 1X PBS, pH 7.4, at 1.0 mL/min flow rate.

One-half milliliter fractions were collected in glass tubes and aliquots of these counted in a gamma counter. The lower and upper windows were set to 100 and 500 KeV respectively.

The radioincorporation was calculated by summing the radioactivity associated with the eluted protein peak and dividing this number by the total radioactivity eluted from the column; this value was then expressed as a percentage (data not shown). In some cases, the radioincorporation was determined using instant thin-layer chromatography ("ITLC"). Radiolabeled conjugate was diluted 1:10 or 1:20 in 1X PBS containing or 1X PI3S/1 mM DTPA, then 1 L was spotted 1.5 cm from one end of a 1 x 5 cm strip of ITLC SG paper. The paper was developed by ascending chromatography using 10% ammonium acetate in methanol:water (1:1;v/v). The strip was dried, cut in half crosswise, and the radioactivity associated with each section determined by gamma counting. The radioactivity associated with the bottom half of the strip (protein-associated radioactivity) was *Trade-mark WO 94/11026 2 1 493, M PC'I'/US93/10953 expressed as a percentage of the total radioactivity, determined by summing the values for both top and bottom halves (data not shown).

Specific activities were determined by measuring the radioactivity of an appropriate aliquot of the radiolabeled conjugate. This value was corrected for the counter efficiency (typically 75%) and related to the protein concentration of the conjugate, previously determined by absorbance at 280 nm, and the resulting value expressed as mCi/mg protein.

For some experiments, 2B8-MX-DTPA was radiolabeled with indium [1111 following a protocol similar to the one described above but without purification by HPLC; this was referred to as the "mix-and-shoot" protocol.

vii. Preparation of Yttrium-f901-Labeled 2B8-MX-DTPA ("Y2B8") The same protocol described for the preparation of 12B8 was followed for the preparation of the yttrium-[90]-labeled 2B8-MX-DTPA ("Y2B8") conjugate except that 2 ng HCl was not utilized; all preparations of yttrium-labeled conjugates were purified by size-exclusion chromatography as described above.

C. Non-Human Animal Studies.

i. Biodistribution of Radiolabeled 2B8-MX-DTPA

12B8 was evaluated for tissue biodistribution in six-to-eight week old BALB/c mice. The radiolabeled conjugate was prepared using clinical-grade 2B8-MX-DTPA following the "mix and shoot" protocol described above. The specific activity of the conjugate was 2.3 mCi/mg and the conjugate was formulated in PBS, pH 7.4 containing 50mg/mL HSA. Mice were injected intravenously with 100 L of 12B8 (approximately 21 Ci) and groups of three mice were sacrificed by cervical dislocation at 0, 24, 48, and 72 hours. After WO 94/11026 2149 329 PC.'I/US93/10953 sacrifice, the tail, heart, lungs, liver, kidney, spleen, muscle, and femur were removed, washed and weighed; a sample of blood was also removed for analysis.
Radioactivity associated with each specimen was determined by gamma counting and the percent iWected doAw pcar gram tioaue Auboequwntly doterminwd. Na attempt was made to discount the activity contribution represented by the blood associated with individual organs.

In a separate protocol, aliquots of 2B8-MX-DTPA incubated at 4 C and 30 C for weeks were radiolabeled with indium-[111] to a specific activity of 2.1 mCi/mg 10 for both preparations. These conjugates were then used in biodistribution studies in mice as described above.

For dosimetry determinations, 2B8-MX-DTPA was radiolabeled with indium-[111] to a specific activity of 2.3 mCi/mg and approximately 1.1 Ci was injected into each of 20 BALB/c mice. Subsequently, groups of five mice each were sacrificed at 1, 24, 48 and 72 hours and their organs removed and prepared for analysis. In addition, portions of the skin, muscle and bone were removed and processed for analysis; the urine and feces were also collected and analyzed for the 24-72 hour time points.

Using a similar approach, 2B8-MX-DTPA was also radiolabeled with yttrium-[901 and its biological distribution evaluated in BALB/c mice over a 72-hour time period. Following purification by HPLC size exclusion chromatography, four groups of five mice each were injected intravenously with approximately 1 Ci of clinically-formulated conjugate (specific activity:12.2 mCi/mg); groups were subsequently sacrificed at 1, 24, 48 and 72 hours and their organs and tissues analyzed as described above. Radioactivity associated with each tissue specimen was determined by measuring bremstrahlung energy with a gamma scintillation counter. Activity values were subsequently expressed as percent injected dose WO 94/11026 2149329 PC'T/US93/10953 per gram tissue or percent injected dose per organ. While organs and other tissues were rinsed repeatedly to remove superficial blood, the organs were not perfused. Thus, organ activity values were not discounted for the activity oontribution raprQment4d by internally aoaociated blood, ii. Tumor Localization of 12B8 The localization of radiolabeled 2B8-MX-DTPA was determined in athymic mice bearing Ramos B cell tumors. Six-to-eight week old athyinic mice were injected subcutaneously (left-rear flank) with 0.1 mL of RPMI-1640 containing 1.2 X 107 Ramos tumor cells which had been previously adapted for growth in athymic mice. Tumors arose within two weeks and ranged in weight from 0.07 to 1.1 grams. Mice were injected intravenously with 100 L of indium-[1111-labeled 2B8-MX-DTPA (16.7 Ci) and groups of three mice were sacrificed by cervical dislocation at 0, 24, 48, and 72 hours. After sacrifice the tail, heart, lungs, liver, kidney, spleen, muscle, femur, and tumor were removed, washed, weighed; a sample of blood was also removed for analysis. Radioactivity associated with each specimen was determined by gamma counting and the percent injected dose per gram tissue determined.

iii. Biodistribution and Tumor Localization Studies with Radiolabeled 2B8-MX-DTPA .

Following the preliminary biodistribution experiment described above (Example I.B.viii.a.), conjugated 2B8 was radiolabeled with indium-[111]
to a specific activity of 2.3 mCi/mg and roughly 1.1 Ci was injected into each of twenty BALB/c mice to determine biodistribution of the radiolabeled material.
Subsequentially, groups of five mice each were sacrificed at 1, 24, 48 and 72 hours and their organs and a portion of the skin, inuscle and bone were removed and processed for analysis. In addition, the urine and feces were collected and analyzed for the 24-72 hour time-points. The level of radioactivity in the blood dropped from 40.3% of the injected dose per gram at 1 hour to 18.9% at 72 hours (data not shown). Values for the heart, kidney, muscle and spleen remained in the range of 0.7-9.8% throughout the experiment. Levels of radioactivity found in the lungs decreased from 14.2% at 1 hour to 7.6% at 72 hours; similarly the respective liver injected-dose per gram values were 10.3% and 9.9%. These data were used in determining radiation absorbed dose estimates 12B8 described below.

The biodistribution of yttrium-[90]-labeled conjugate, having a specific activity of 12.2 mCi/mg antibody, was evaluated in BALB/c mice. Radioincorporations of >90% were obtained and the radiolabeled antibody was purified by HPLC.
Tissue deposition of radioactivity was evaluated in the major organs, and the skin, muscle, bone, and urine and feces over 72 hours and expressed as percent injected dose/g tissue. Results (not shown) evidenced that while the levels of radioactivity associated with the blood dropped from approximately 39.2%

injected dose per gram at 1 hour to roughly 15.4% after 72 hours the levels of radioactivity associated with tail, heart, kidney, muscle and spleen remained fairly constant at 10.2% or less throughout the course of the experiment.
Importantly, the radioactivity associated with the bone ranged from 4.4% of the injected dose per gram bone at 1 hour to 3.2% at 72 hours. Taken together, these results suggest that little free yttrium was associated with the conjugate and that little free radiometal was released during the course of the study. These data were used in determining radiation absorbed dose estimates for Y2B8 described below.

For tumor localization studies, 2B8-MX-DTPA was prepared and radiolabeled with 111Indium to a specific activity of 2.7 mCi/mg. One hundred microliters of labeled conjugate (approximately 24 Ci) were subsequently injected into each of 12 athymic mice bearing Ramos B cell tumors. Tumors ranged in weight from 0.1 to 1.0 grams. At time points of 0, 24, 48, and 72 hours following injection, 50 WO 94/11026 2 149 3 2 g ~ PCT/US93/10953 L of blood was removed by retro-orbital puncture, the mice sacrificed by cervical dislocation, and the tail, heart, lungs, liver, kidney, spleen, muscle, femur, and tumor removed. After processirig and weighing the tissues, the radioactivity aseo6ated with aach tisaua specimen was determined using a gamma counter and the values expressed as percent injected dose per gram.

The results (not shown) evidenced that the tumor concentrations of the 111In-2B8-MX-DTPA increased steadily throughout the course of the experiment.
Thirteen percent of the injected dose was accumulated in the tumor after 72 hours. The blood levels, by contrast, dropped during the experiment from over 30% at time zero to 13% at 72 hours. All other tissues (except muscle) contained between 1.3 and 6.0% of the injected dose per gram tissue by the end of the experiment; muscle tissue contained approximately 13% of the injected dose per gram.

D. Human Studies i. 2B8 and 2B8-MX-DTPA: Immunohistologv Studies with Human Tissues The tissue reactivity of murine monoclonal antibody 2B8 was evaluated using a panel of 32 different human tissues fixed with acetone.
Antibody 2B8 reacts with the anti-CD20 antigen which had a very restricted pattern of tissue distribution, being observed only in a subset of cells in lymphoid tissues including those of hematopoietic origin.

In the lymph node, immunoreactivity was observed in a population of mature cortical B-lymphocytes as well as proliferating cells in the germinal centers.
Positive reactivity was also observed in the peripheral blood, B-cell areas of the tonsils, white pulp of the spleen, and with 40-70% of the medullary lymphocytes found in the thymus. Positive reactivity was also seen in the follicles of the lamina propria (Peyer's Patches) of the large intestines. Finally, aggregates or scattered lymphoid cells in the stroma of various organs, including the bladder, breast, cervix, esophagus, lung, parotid, prostate, small intestine, and stomach, were also iDoQitive with antibody 2B8 (data not shown).

All simple epithelial cells, as well as the stratified epithelia and epithelia of different organs, were found to be unreactive. Similarly, no reactivity was seen with neuroectodermal cells, including those in the brain, spinal cord and peripheral nerves. Mesenchymal elements, such as skeletal and smooth muscle cells, fibroblasts, endothelial cells, and polymorphonuclear inflammatory cells were also found to be negative (data not shown).

The tissue reactivity of the 2B8-MX-DTPA conjugate was evaluated using a panel of sixteen human tissues which had been fixed with acetone. As previously demonstrated with the native antibody (data not shown), the 2B8-MX-DTPA

conjugate recognized the CD20 antigen which exhibited a highly restricted pattern of distribution, being found only on a subset of cells of lymphoid origin.
In the lymph node, immunoreactivity was observed in the B cell population.
Strong reactivity was seen in the white pulp of the spleen and in the medullary lymphocytes of the thymus. Immunoreactivity was also observed in scattered lymphocytes in the bladder, heart, large intestines, liver, lung, and uterus, and was attributed to the presence of inflammatory cells present in these tissues.
As with the native antibody, no reactivity was observed with neuroectodermal cells or with mesenchymal elements (data not shown).

WO 94/11026 2149329 PCI'/US93/10953 ii. Clinical Analysis of 12B8 (Imaging) and Y2B8 (Therapv) a. Phase I/II Clinical Trial Single Dose Therapy Study A Phase I/II clinical analysis of 12B8 (imaging) followed by treatrnent with a Ainpde therapeutic dose of Y2B8 ie currently being conducted.
For the single-dose study, the following schema is being followed:

1. Peripheral Stem Cell (PSC) or Bone Marrow (BM) Harvest with Purging;
2. 12B8 Imaging;
3. Y2B8 Therapy (three Dose Levels); and 4. PSC or Autologous BM Transplantation (if necessary based upon absolute neutrophil count below 500/mm3 for three consecutive days or platelets below 20,000/mm3 with no evidence of marrow recovery on bone marrow examination).

The Dose Levels of Y2B8 are as follows:

Dose Level Dose (mCi) 1. 20 2. 30 3. 40 Three patients are to be treated at each of the dose levels for determination of a Maximum Tolerated Dose ("MTD").

Imaging (Dosimetry) Studies are conducted as follows: each patient is involved in two in vivo biodistribution studies using 12B8. In the first study, 2mg of (5mCi), is administered as an intravenous (i.v.) infusion over one hour; one week later 2B8 (ie unconjugated antibody) is administered by i.v. at a rate not to exceed 250mg/hr followed immediately by 2mg of 12B8 (5mCi) administered by i.v. over one hour. In both studies, immediately following the 12B8 infusion, each patient is imaged and imaging is repeated at time t = 14-18 hr (if indicated), t =

24 hr; t = 72 hr; and t = 96 hr (if indicated). Whole body average retention times for the indium (111] label are determined; such determinations are also made for recognizable organs or tumor lesions ("regions of interest").

II
WO 94/11026 PC'I/US93/10953 The regions of interest are compared to the whole body concentrations of the label; based upon this comparison, an estimate of the localization and concentration of Y2B8 can be determined using standard protocols. If the estimated cumulative dose of Y2138 is greater than eight (8) times the estimateci whole body dose, or if the estimated cumulative dose for the liver exceeds cGy, no treatment with Y2B8 should occur.

If the imaging studies are acceptible, either 0.0 or 1.0mg/kg patient body weight of 2B8 is administered by i.v. infusion at a rate not to exceed 250mg/h. This is followed by administration of Y2B8 (10,20 or 40mCi) at an i.v. infusion rate of 20mCi/hr.

b. Phase I/II Clinical Trial: Multiple Dose Therapy Study A Phase I/II clinical analysis of of Y2B8 is currently being conducted. For the multiple-dose study, the following schema is being followed:
1. PSC or BM Harvest;
2. 12B8 Imaging;
3. Y2B8 Therapy (three Dose Levels) for four doses or a total cumulative dose of 80mCi; and 4. PSC or Autologous BM Transplantation (based upon decision of medical practitioner).

The Dose Levels of Y2B8 are as follows:

Dose Level Dose (mCi) 1. 10 2. 15 3. 20 Three patients are to be treated at each of the dose levels for determination of an MTD.

Imaging (Dosimetry) Studies are conducted as follows: A preferred imaging dose for the unlabeled antibody (ie 2B8) will be determined with the first two patients.
The first two patients will receive 100mg of unlabeled 2B8 in 250cc of normal ealine over 4 hrs followed by 0,5mCi of 12B8 -- blood will be sampled for biodistribution data at times t =0, t = 10miti., t = 120 min., t = 24 hr, and t = 48 hr. Patients will be scanned with multiple regional gamma camera images at times t = 2 hr, t = 24 hr and t = 48 hr. After scanning at t = 48 hr, the patients will receive 250mg of 2B8 as described, followed by 4.5mCi of 12B8 -- blood and scanning will then follow as described. If 100mg of 2B8 produces superior imaging, then the next two patients will receive 50mg of 2B8 as described, followed by 0.5mCi of 12B8 followed 48 hrs later by 100mg 2B8 and then with 4.5mCi of 12B8. If 250mg of 2B8 produces superior imaging, then the next two patients will receive 250mg of 2B8 as described, followed by 0.5mCi of 12B8 followed 48 hrs later with 500mg 2B8 and then with 4.5mCi of 12B8. Subsequent patients will be treated with the lowest amount of 2B8 that provides optimal imaging. Optimal imaging will be defined by: (1) best effective imaging with the slowest disappearance of antibody; (2) best distribution minimizing compartmentalization in a single organ; and (3) best subjective resolution of the lesion (tumor/background comparison).

For the first four patients, the first therapeutic dose of Y2B8 will begin 14 days after the last dose of 12B8; for subsequent patients, the first therapeutic dose of Y2B8 will begin between two to seven days after the 12B8.

Prior to treatment with Y2B8, for the patients other than the first four, 2B8 will be administered as described, followed by i.v. infusion of Y2B8 over 5-10 min.
Blood will be sampled for biodistribution at times t = 0, t = 10min., t = 120 min., t = 24 hr and t = 48 hr. Patients will receive repetitive doses of Y2B8 (the saine dose administered as with the first dose) approximately every six to eight weeks for a maximum of four doses, or total cumulative dose of 80mCi. It is most preferred that patients not receive a subsequent dose of Y2B8 until the patients' WBC is greater than/equal to 3,000 and AGC is greater than/equal to 100,000.

Following completion of the three-dose level study, an MTD will be defined.
Additional patients will then be enrolled in the study and these will receive the MTD.

II. CHIMERIC ANTI-CD20 ANTIBODY PRODUCTION ("C2B8") A. Construction of Chimeric Anti-CD20 Immunoglobulin DNA Expression Vector RNA was isolated from the 2B8 mouse hybridoma cell (as described in Chomczynki, P. et al., "Single step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction." Anal. Biochem. 162:156-159 (1987)).
and cDNA was prepared therefrom. The mouse immunoglobulin light chain variable region DNA was isolated from the cDNA by polymerase chain reaction using a set of DNA primers with homology to mouse light chain signal sequences at the 5' end and mouse light chain J region at the 3' end. Primer sequences were as follows:

1. VL Sense (SEQ. ID. NO. 8) 5' ATC AC -AT T CTC ACC ATG GAT TTT CAG GTG CAG
ATT ATC AGC TTC 3' (The underlined portion is a Bgl II site; the above-lined portion is the start codon.) 2. VL Antisense (SEQ. ID. NO. 9) 5' TGC AGC ATC CGTACG TTT GAT TTC CAG CT~ 3 (The underlined portion is a Bsi WI site.) See, Figures 1 and 2 for the corresponding Bgl II and Bsi WI sites in TCAE 8, and Figure 3 for the corresponding sites in anti-CD20 in TCAE 8.

These resulting DNA fragment were cloned directly into the TCAE 8 vector in front of the human kappa light chain constant domain and sequenced. The determined DNA sequence for the murine variable region light chain is set forth in Figure 4 (SEQ. ID. NO. 3); see also Figure 3, nucleotides 978 through 1362.
Figure 4 further provides the amino acid sequence from this murine variable region, and the CDR and framework regions (SEQ ID NO:4). The mouse light chain variable region from 2B8 is in the mouse kappa VI family. See Kabat, supra.

The mouse heavy chain variable region was similarly isolated and cloned in front of the human IgGl constant domains. Primers were as follows:

1. VK Sense (SEQ. ID. NO. 10) 5' GCG GCT CCC ACGCGT GTC CTG TCC CAG 3' (The underlined portion is an Mlu I site.) 2. VH Antisense (SEQ. ID. NO. 11) 5' GG(G/C) TGT TGT GCTAGC TG(A/C) (A/G)GA GAC
(G/A)GT GA 3' (The underlined portion is an \ne I site.) See, Figures 1 and 2 for corresponding iMlu I and Nhe I sites in TCAE 8, and Figure 3 for corresponding sites in anti-CD20 in 'I'CAD, 8.

The sequence for this mouse heavy chain is set forth in Figure 5 (SEQ. ID. NO.
5); see also Figure 3, nucleotide 2401 through 2820. Figure 5 also provides the amino acid sequence from this murine variable region, and the CDR and framework regions (SEQ ID NO:6). The mouse heavy chain variable region from 2B8 is in the mouse VH 2B family. See Kabat, supra.

B. Creation of Chimeric Anti-CD20 Producing CHO and SP210 Transfectomas Chinese hamster ovary ("CHO") cells DG44 were grown in SSFM II minus hypoxanthine and thymidine media (Gibco, Grand Island, NY, Form No.,91-0456PK); SP2/0 mouse myeloma cells were grown in Dulbecco's Modified Eagles Medium media ("DMEM") (Irvine Scientific, Santa Ana, Ca., Cat. No. 9024) with 5% fetal bovine serum and 20 ml/L glutamine added. Four million cells were electroporated with either 25 g CHO or 50 g SP2/0 plasmid DNA that had been restricted with Not I using a BTX 600 electroporation system (BTX, San Diego, CA) in 0.4 ml disposable cuvettes. Conditions were either 210 volts for CHO or 180 volts for SP2/0, 400 microfaradays, 13 ohms. Each electroporation was plated into six 96 well dishes (about 7,000 cells/well). Dishes were fed with media containing G418 (GENETICIN, Gibco, Cat. No. 860-1811) at 400 g/ml active compound for CHO (media further included 50 M hypoxanthine and 8 M thymidine) or 800 g/ml for SP2/0, two days following electroporation and thereafter 2 or 3 days until colonies arose. Supernatant from colonies was assayed for the presence of chimeric immunoglobulin via an ELISA specific for human antibody. Colonies producing the highest amount of immunoglobulin WO 94/11026 PCr/US93/10953 ~j 2 were expandedq 4md p(~lated3 9into 996 well plates containing media plus methotrexate (25 nM for SP2/0 and 5nM for CHO) and fed every two or three days. Supernatants were assayed as above and colonies producing the highest amount of immunoglobulin were examined, Chimeric anti-CD20 antibody was purified from supernatant using protein A affinity chromatography.

Purified chimeric anti-CD20 was analyzed by electrophoresis in polyacrylamide gels and estimated to be greater than about 95% pure. Affinity and specificity of the chimeric antibody was determined based upon 2B8. Chimeric anti-CD20 antibody tested in direct and competitive binding assays, when compared to murine anti-CD20 monoclonal antibody 2B8, evidenced comparable affinity and specificity on a number of CD20 positive B cells lines (data not presented).
The apparent affinity constant ("Kap") of the chimeric antibody was determined by direct binding of 1125 radiolabeled chimeric anti-CD20 and compared to radiolabeled 2B8 by Scatchard plot; estimated Kap for CHO produced chimeric anti-CD20 was 5.2 x 10-9 M and for SP2/0 produced antibody, 7.4x10-9M. The estimated Kap for 2B8 was 3.5 x 10-9 M. Direct competition by radioimmunoassay was utilized to confirm both the specificity and retention of immunoreactivity of the chimeric antibody by comparing its ability to effectively compete with 2B8. Substantially equivalent amounts of chimeric anti-CD20 and 2B8 antibodies were required to produce 50% inhibition of binding to CD20 antigens on B cells (data not presented), ie there was a minimal loss of inhibiting activity of the anti-CD20 antibodies, presumably due to chimerization.

The results of Example II.B indicate, inter alia, that chimeric anti-CD20 antibodies were generated from CHO and SP2/0 transfectomas using the TCAE 8 vectors, and these chimeric antibodies had substantially the same specificity and binding capability as murine anti-CD20 monoclonal antibody 2B8.

WO 94/11026 2, 49 3 2 9 PC'I'/US93/10953 C. Determination of Immunological Activitv of Chimeric Anti-CD20 Antibodies i. Human C1!g Analysis Chimeric anti-CD20 antibodies produced by both CHO and SP2/0 cell lines were evaluated !br human Clq biuding in a flow cytometry asaa,y using fluorescein labeled Clq (Clq was obtained from Quidel, Mira Mesa, CA, Prod.
No. A400 and FITC label from Sigma, St. Louis MO, Prod. No. F-7250; FITC.
Labeling of Clq was accomplished in accordance with the protocol described in Selected Methods In Cellular Immunology, Michell & Shiigi, Ed. (W.H. Freeman & Co., San Francisco, CA, 1980, p. 292). Analytical results were derived using a Becton Dickinson FACScanTM flow cytometer (fluorescein measured over a range of 515-545 nm). Equivalent amounts of chimeric anti-CD20 antibody, human IgGl,K myeloma protein (Binding Site, San Diego, Ca, Prod. No. BP078), and 2B8 were incubated with an equivalent number of CD20-positive SB cells, followed by a wash step with FACS buffer (.2% BSA in PBS, pH 7.4,.02% sodium azide) to remove unattached antibody, followed by incubation with FITC labeled Clq. Following a 30-60 min. incubation, cells were again washed. The three conditions, including FITC-labeled Clq as a control, were analyzed on the FACScanTM following manufacturing instructions. Results are presented in Figure 6.

As the results of Figure 6 evidence, a significant increase in fluorescence was observed only for the chimeric anti-CD20 antibody condition; ie only SB cells with adherent chimeric anti-CD20 antibody were Clq positive, while the other conditions produced the same pattern as the control.
ii. Complement Dependent Cell L,vses Chimeric anti-CD20 antibodies were analyzed for their ability to lyse lymphoma cell lines in the presence of human serum (complement source).
CD20 positive SB cells were labeled with 51Cr by admixing 100g Ci of 51Cr with lx';p SB ce:ls for 1 hr at 37 C; labeled SB cells were then incubated in the pre:ence of equivalent amounts of human complement and equivalent amounts (0-50 g/ml) of either chimeric anti-CD20 antibodies or 2B8 for 4 hr at 37'C
(see, Brunner, K.T. et al., "Quantitative assay of the lytic action of immune lymphoid cells on 51Cr-labeled allogeneic target cells in vitro." Immunology 1=:181-189 (1968). Results are presented in Figure 7.

The results of Figure 7 indicate, inter alia, that chimeric anti-CD20 antibodies produced si:nificant lysis (49%) under these conditions.

iii. Antibodv Dependent Cellular CvtQtoxicitv EfFector Assay For this study, CD20 positive cells (SB) and CD20 negative cells (T
cell leukemia line HSB; see, Adams, Richard, "Formal Discussion," Can. Res.
27:2479-2482 (1967); ATCC deposit no. ATCC CCL 120.1) were utilized; both were labeled Nvith 51Cr. Analysis was conducted following the protocol described in Brunner, K.T. et al., "Quantitative assay of the lytic action of immune lymphoid cells on 51Cr-labeled a]]ogeneic target cells in vitro; inhibition by isoantibody and drugs." Immunology 14:181-189 (1968); a substantial chimeric anti-CD20 antibody dependent cell mediated lysis of CD20 positive SB target cells ( s1Cr-labeled) at the end of a 4 hr, 37 C incubation, was observed and this effect was observed for both CHO and SP2/0 produced antibody (effector cells were human peripheral lymphocytes; ratio of effector cells:target was 100:1).
Efficient lysis of tasget cells was obtained at 3.9 g/ml. In contrast, under the same conditions, the murine anti-CD20 monoclonal antibody 2B8 had a statistically insignificant effect, and CD20 negative HSB cells were not lysed.
Results are presented in Figure 8.

The results of Example II indicate, i,zter alia, that the chimeric anti-CD20 antibodies of Example I were immunologically active.

.y!j.

WO 94/11026 PC'T/US93/10953 III. DEPLETION OF B CELLS IN VIVO USING CHIMERIC ANTI-CD20 A IV .- rim.n.n. Prim.a .- 4t .dy Three separate non-human primate studies were conducted. For convenience, these are referred to herein as "Chimeric Anti-CD20: CHO &
SP2/0;" "Chimeric Anti-CD20: CHO;" and "High Dosage Chimeric Anti-CD20."
Conditions were as follows:

Chimeric Anti-CD20: CHO & SP2/0 Six cynomolgus monkeys ranging in weight from 4.5 to 7 kilograms (White Sands Research Center, Alamogordo, NM) were divided into three groups of two monkeys each. Both animals of each group received the same dose of immunologically active chimeric anti-CD20 antibody. One animal in each group received purified antibody produced by the CHO transfectoma; the other received antibody produced by the SP2/0 transfectoma. The three groups received antibody dosages corresponding to 0.1 mg/kg, 0.4 mg/kg, and 1.6 mg/kg each day for four (4) consecutive days. The chimeric immunologically active anti-CD20 antibody, which was admixed with sterile saline, was administered by intravenous infusion; blood samples were drawn prior to each infusion.
Additional blood samples were drawn beginning 24 hrs after the last injection (T=O) and thereafter on days 1, 3, 7, 14 and 28; blood samples were also taken thereafter at biweekly intervals until completion of the study at day 90.

Approximately 5 ml of whole blood from each animal was centrifuged at 2000 RPM for 5 min. Plasma was removed for assay of soluble chimeric anti-CD20 antibody levels. The pellet (containing peripheral blood leukocytes and red blood cells) was resuspended in fetal calf serum for fluorescent-labeled antibody analysis (see, "Fluorescent Antibody Labeling of Lymphoid Cell Population,"
infra.).

Chimeric Anti-CD20: CHO
Six cynomolgus monkeys ranging in weight from 4 to 6 kilograms (White Sands) were divided into three groups of two monkeys each. All animals were injected with immunologically active chimeric anti-CD20 antibodies produced from the CHO transfectoma (in sterile saline). The three groups were separated as follows: subgroup 1 received daily intravenous injections of 0.01 mg/kg of the antibody over a four (4) day period; subgroup 2 received daily intravenous injections of 0.4 mg/kg of the antibody over a four (4) day period; subgroup 3 received a single intravenous injection of 6.4 mg/kg of the antibody. For all three subgroups, a blood sample was obtained prior to initiation of treatment;
additionally, blood samples were also drawn at T=O, 1, 3, 7, 14 and 28 days following the last injection, as described above, and these samples were processed for fluorescent labeled antibody analysis (see, "Fluorescent Antibody Labeling," infra.). In addition to peripheral blood B cell quantitation, lymph node biopsies were taken at days 7, 14 and 28 following the last injection, and a single cell preparation stained for quantitation of lymphocyte populations by flow cytometry.

High Dosage Chimeric Anti-CD20 Two cynomolgus monkeys (White Sands) were infused with 16.8 mg/kg of the immunologically active chimeric anti-CD20 antibodies from the CHO

transfectomas (in sterile saline) weekly over a period of four consecutive weeks.
At the conclusion of the treatment, both animals were anesthetized for removal of bone marrow; lymph node biopsies were also taken. Both sets of tissue were stained for the presence of B lymphocytes using Leu 16 by flow cytometry following the protocol described in Ling, N.R. et al., "B-cell and plasma cell WO 94/11026 2 149 3 2 9 ' PCT/US93/10953 antigens." Leucocyte Typing III White Cell Differentiations Antigens, A.J.
McMichael, Ed. (Oxford University Press, Oxford UK, 1987), p. 302.
Fluorescent Antibody Labeling of Lymphoid Cell Population After removal of plasma, leukocytes were washed twice with Hanks Balanced Salt Solution ("HBSS") and resuspended in a plasma equivalent volume of fetal bovine serum (heat inactivated at 56 C for 30 min.). A 0.1 ml volume of the cell preparation was distributed to each of six (6), 15 ml conical centrifuge tubes Fluorescein labeled monoclonal antibodies with specificity for the human lymphocyte surface markers CD2 (AMAC, Westbrook, ME), CD20 (Becton Dickinson) and human IgM (Binding Site, San Diego, CA) were added to 3 of the tubes for identifying T and B lymphocyte populations. All reagents had previously tested positive to the corresponding monkey lymphocyte antigens.
Chimeric anti-CD20 antibody bound to monkey B cell surface CD20 was measured in the fourth tube using polyclonal goat anti-human IgG coupled with phycoerythrin (AMAC). This reagent was pre-adsorbed on a monkey Ig-sepharose column to prevent cross-reactivity to monkey Ig, thus allowing specific detection and quantitation of chimeric anti-CD20 antibody bound to cells. A
fifth tube included both anti-IgM and anti-human IgG reagents for double stained B

cell population. A sixth sample was included with no reagents for determination of autofluorescence. Cells were incubated with fluorescent antibodies for 30 min., washed and fixed with 0.5 ml of fixation buffer (0.15 M NaCI, 1%
paraformaldehyde, pH7.4) and analyzed on a Becton Dickinson FACScanT"f instrument. Lymphocyte populations were initially identified by forward versus right angle light scatter in a dot-plot bitmap with unlabeled leucocytes. The total lymphocyte population was then isolated by gating out all other events.
Subsequent fluorescence measurements reflected only gated lymphocyte specific events.

WO 94/11026 2 149329 PCI'/US93/10953 Depletion of Peripheral Blood B Lymphocytes No observable difference could be ascertained between the efficacy of CHO and SP2/0 produced antibodies in depleting B cells in vivo, although a slight increase in B cell rQcAvorv baqinning aftor day 7 far monkeye iniected with chimeric anti-CD20 antibodies derived from CHO transfectomas at dosage levels 1.6 mg/kg and 6.4 mg/kg was observed and for the monkey injected with SP2/0 producing antibody at the 0.4 mg/kg dose level. Figures 9A, B and C provide the results derived from the chimeric anti-CD20:CHO & SP2/0 study, with Figure 9A
directed to the 0.4 mg/kg dose level; Figure 9B directed to the 1.6 mg/kg dose level; and Figure 9C directed to the 6.4 mg/kg dose level.

As is evident from Figure 9, there was a dramatic decrease (>95%) in peripheral B cell levels after the therapeutic treatment across all tested dose ranges, and these levels were maintained up to seven (7) days post infusion; after this period, B cell recovery began, and, the time of recovery initiation was independent of dosage levels.

In the Chimeric Anti-CD20:CHO study, a 10-fold lower antibody dosage concentration (0.01 mg/kg) over a period of four daily injections (0.04 mg/kg total) was utilized. Figure 10 provides the results of this study. This dosage depleted the peripheral blood B cell population to approximately 50% of normal levels estimated with either the anti-surface IgM or the Leu 16 antibody. The results also indicate that saturation of the CD20 antigen on the B lymphocyte population was not achieved with immunologically active chimeric anti-CD20 antibody at this dose concentration over this period of time for non-human primates; B lymphocytes coated with the antibody were detected in the blood samples during the initial three days following therapeutic treatment.
However, by day 7, antibody coated cells were undetectable.

Table I summarizes the results of single and multiple doses of immunologically active chimeric anti-CD20 antibody on the peripheral blood populations; single dose condition was 6.4 mg/kg; multiple dose condition was 0.4 mg/kg over four (4) consecutive days (these results were derived from the monkeys described above).

TABLE I

Mon e Dose Dav CD2 Anti-Hu IgG
A 0.4 mg/kg Prebleed 81.5 -(4 danoa) 0 86.5 0.2 7 85.5 0.0 21 93.3 -28 85.5 -B 0.4 mg/kg Prebleed 81.7 -(4 doses) 0 94.6 0.1 7 92.2 0.1 21 84.9 -28 84.1 -C 6.4 mg/kg Prebleed 77.7 0.0 (1 dose) 7 85.7 0.1 21 86.7 -28 76.7 -D 6.4 mg/kg Prebleed 85.7 0.1 (1 dose) 7 94.7 0.1 21 85.2 -28 85.9 -Anti-Hu IgG+
Monkev Anti-Hu IgM* Leu-16 % B Cell Depletion A - 9.4 0 0.3 0.0 97 0.1 1.2 99 - 2.1 78 - 4.1 66 B - 14.8 0 0.2 0.1 99 0.1 0.1 99 - 6.9 53 - 8.7 41 C 0.2 17.0 0 0.1 0.0 99 - 14.7 15 - 8.1 62 D 0.1 14.4 0 0.2 0.0 99 - 9.2 46 - 6.7 53 *Double staining population which indicates extent of chimeric anti-CD20 coated B cells.

2149.329 The data summarized in Table I indicates that depletion of B cells in peripheral blood under conditions of antibody excess occurred rapidly and effectively, regardless of single or multiple dosage levels. Additionally, depletion was observed for at least seven (7) days following the last injection, with partial B cell recovery observed by day 21.

Table II summarizes the effect of immunologically active, chimeric anti-CD20 antibodies on cell populations of lymph nodes using the treatment regimen of Table I(4 daily doses of 0.4 mg/kg; 1 dose of 6.4 mg/kg); comparative values for normal lymph nodes (control monkey, axillary and inguinal) and normal bone marrow (two monkeys) are also provided.

//

W0 94/11026 2 149 329 PC'1'/US93/10953 TABLE II
CELL POPULATIONS OF LYMPH NODES

Monkey Dose Dav CD2 Anti-Hu IgM
A 0.4 mg/kg 7 66.9 -(4 doses) 14 76.9 19.6 28 61.6 19.7 B 0.4 mg/kg 7 59.4 -(4 doses) 14 83.2 9.9 28 84.1 15.7 C 6.4 mg/kg 7 75.5 -(1 dose) 14 74.1 17.9 28 66.9 23.1 D 6.4 mg/kg 7 83.8 -(1 dose) 14 74.1 17.9 28 84.1 12.8 TABLE II (continued) Anti-Hu IgG +
on e Anti-Hu IgM Leu-16 % B Lym hoc e De letion A 7.4 40.1 1 0.8 22.6 44 - 26.0 36 B 29.9 52.2 0 0.7 14.5 64 - 14.6 64 C 22.3 35.2 13 1.1 23.9 41 - 21.4 47 D 12.5 19.7 51 0.2 8.7 78 - 12.9 68 TABLE II (continued) Anti-Hu IgG+ % B Lymphocyte C',D2 Anti-Hu I~M Anti-Hu IgM Leu-16 Depletion Normal Lymph Nodes Control 1 Axillary 55.4 25.0 - 41.4 NA
Inguinal 52.1 31.2 - 39.5 NA
Normal Bone Marrow Control 2 65.3 19.0 - 11.4 NA
Control 3 29.8 28.0 - 16.6 NA

The results of Table II evidence effective depletion of B lymphocytes for both treatment regimens. Table II further indicates that for the non-human primates, complete saturation of the B cells in the lymphatic tissue with immunologically active, chimeric anti-CD20 antibody was not achieved; additionally, antibody coated cells were observed seven (7) days after treatment, followed by a marked depletion of lymph node B cells, observed on day 14.

Based upon this data, the single High Dosage Chimeric Anti-CD20 study referenced above was conducted, principally with an eye toward pharmacology/toxicology determination. Ie this study was conducted to evaluate any toxicity associated with the administration of the chimeric antibody, as well as the efficacy of B cell depletion from peripheral blood lymph nodes and bone marrow. Additionally, because the data of Table II indicates that for that study, the majority of lymph node B cells were depleted between 7 and 14 days following treatment, a weekly dosing regimen might evidence more efficacious results. Table III summarizes the results of the High Dosage Chimeric Anti-CD20 study.

WO 94/11026 2 14 9329 PC'T/US93/10953 TABLE III
CELL POPULATIONS OF LYMPH NODES AND BONE MARROW
Lymphocyte Populations (%) Mnu1 x CQ2 CDA48 SUTOU~
Inguinal Lvmph Node E 90.0 5.3 4.8 6.5 22 F 91.0 6.3 5.6 6.3 22 G 89.9 5.0 3.7 5.8 36 H 85.4 12.3 1.7 1.8 36 Bone Marrow E 46.7 4.3 2.6 2.8 22 F 41.8 3.0 2.1 2.2 22 G 35.3 0.8 1.4 1.4 36 H 25.6 4.4 4.3 4.4 36 aIndicates population stained with Leu 16.

bIndicates double staining population, positive for surface IgM cells and chimeric antibody coated cells.

cIndicates total population staining for chimeric antibody including double staining surface IgM positive cells and single staining (surface IgM negative) cells.

dDays after injection of final 16.8 mg/kg dose.

Both animals evaluated at 22 days post treatment cessation contained less than 5% B cells, as compared to 40% in control lymph nodes (see, Table II, supra).
Similarly, in the bone marrow of animals treated with chimeric anti-CD20 antibody, the levels of CD20 positive cells were less than 3% as compared to 15% in the normal animals (see, Table II, supra). In the animals evaluated at days post treatment cessation, one of the animals (H) had approximately 12% B
cells in the lymph node and 4.4% B cells in bone marrow, while the other (G) had WO 94/11026 2 14g 3 2 g PCT/US93/10953 approximately 5% B cells in the lymph node and 0.8% in the bone marrow--the data is indicative of significant B cell depletion.

Tha s=aoulti+ af rstAmp1Q iII.A indiaatw, inter alia, that low doAvq of immunologically active, chimeric anti-CD20 leads to long-term peripheral blood B cell depletion in primates. The data also indicates that significant depletion of B cell populations was achieved in peripheral lymph nodes and bone marrow when repetitive high doses of the antibody were administered. Continued follow -up on the test animals has indicated that even with such severe depletion of peripheral B lymphocytes during the first week of treatment, no adverse health effects have been observed. Furthermore, as recovery of B cell population was observed, a conclusion to be drawn is that the pluripotent stem cells of these primates were not adversely affected by the treatment.

B. Clinical Analysis of C2B8 i. Phase I/II Clinical Trial of C2B8: Single Dose Therapy Study Fifteen patients having histologically documented relapsed B cell lymphoma have been treated with C2B8 in a Phase I/II Clinical Trial. Each patient received a single dose of C2B8 in a dose-escalating study; there were three patients per dose: 10mg/m2; 50mg/m2; 100mg/m2; 250mg/m2 and 500mg/m2. Treatment was by i.v. infusion through an 0.22 micron in-line filter with C2B8 being diluted in a final volume of 250cc or a maximal concentration of 1mg/ml of normal saline. Initial rate was 50cc/hr for the first hour; if no toxicity was seen, dose rate was able to be escalated to a maximum of 200cc/hr.

Toxicity (as indicated by the clinician) ranged from "none", to "fever" to "moderate" (two patients) to "severe" (one patient); all patients completed the therapy treatment. Peripheral Blood Lymphocytes were analyzed to determine, inter alia, the impact of C2B8 on T-cells and B-cells. Consistently for al I

wo 94/11026 2 1 4 9 3 2 9 PCr/US93/10953 patients, Peripheral Blood B Lymphocytes were depleted after infusion with C2B8 and such depletion was maintained for in excess of two weeks.

One patient (receiving 100ma/2 of C288) pvidenoed a Partial ResBonAQ to the C2B8 treatment (reduction of greater than 50% in the sum of the products of the perpendicular diameters of all measurable indicator lesions lasting greater than four weeks, during which no new lesions may appear and no existing lesions may enlarge); at least one other patient (receiving 500mg/m2) evidenced a Minor Response to the C2B8 treatment (reduction of less than 50% but at least 25% in the sum of the products of the two longest perpendicular diameters of all ' measurable indicator lesions). For presentational efficiency, results of the PBLs are set forth in Figure 14; data for the patient evidencing a PR is set forth in Figure 14A; for the patient evidencing an MR, data is set forth in Figure 14B.
In Figure 14, the following are applicable: -m- = Lymphocytes; -& = CD3+ cells (T cells); -Ac- = CD20+ cells; -S- = CD19+ cells; -9- = Kappa; -J!e~lr =
lambda;
and -*- = C2B8. As evidenced, the B cell markers CD20 and CD19, Kappa and Lambda, were depleted for a period in excess of two weeks; while there was a slight, initial reduction in T-cell counts, these returned to an approximate base-line level in a relatively rapid time-frame.

ii. Phase I/II Clinical Trial of C2B8: Multiple Dose Therap,v Study Patients having histologically confirmed B cell lymphoma with measurable progressive disease are eligible for this study which is separated into two parts: in Phase I, consisting of a dose escalation to characterize dose limiting toxicities and determination of biologically active tolerated dose level, groups of three patients will receive weekly i.v. infusions of C2B8 for a total of four (4) separate infusions. Cumulative dose at each of the three levels will be as follows: 500ing/m2 (125mg/m2/infusion); 1000mg/m2 (250mg/m2/infusion);

wO 94/11026 2149 3 2 9 PCT/US93/10953 1500mg/m2 (375mg/m2/infusion. A biologically active tolerated dose is defined, and will be determined, as the lowest dose with both tolerable toxicity and adequate activity); in Phase II, additional patients will receive the biologically active tolerated dose with an emphasis on determining the activity of the four doses of C2B8.

IV. COMBINATION THERAPY: C2B8 AND Y2B8 A combination therapeutic approach using C2B8 and Y2B8 was investigated in a mouse xenographic model (nu/nu mice, female, approximately 10 weeks old) utilizing a B cell lymphoblastic tumor (Ramos tumor cells). For comparative purposes, additional mice were also treated with C2B8 and Y2B8.
Ramos tumor cells (ATCC, CRL 1596) were maintained in culture using RPMI-1640 supplemented with 10% fetal calf serum and glutamine at 37 C and 5%
C02. Tumors were initiated in nine female nude mice approximately 7-10 weeks old by subcutaneous injection of 1.7 x 106 Ramos cells in a volume of 0.10m1 (HBSS) using a lcc syringe fitted with 25g needle. All animals were manipulated in a laminar flow hood and all cages, bedding, food and water were autoclaved. Tumor cells were passaged by excising tumors and passing these through a 40 mesh screen; cells were washed twice with 1X HBSS (50m1) by centrifugation (1300RPM), resuspended in IX HBSS to 10 x 106 cells/ml, and frozen at -70 C until used.

For the experimental conditions, cells from several frozen lots were thawed, pelleted by centrifugation (1300RPM) and washed twice with 1X HBSS. Cells were then resuspended to approximately 2.0 x 106 cells/ml. Approximately 9 to 12 mice were injected with 0.10ml of the cell suspension (s.c.) using a lcc syringe fitted with a 25g needle; injections were made on the animal's left side, WO 94/11026 2 1 49 3 2 9 PCI'/US93/10953 approximately mid-region. Tumors developed in approximately two weeks.
Tumors were excised and processed as described above. Study mice were injected as described above with 1.67 x 106 cells in 0.10ml HBSS.

Based on preliminary dosing experiments, it was determined that 200mg of C2B8 and 100 Ci of Y2B8 would be utilized for the study. Ninety female nu/nu mice (approximately 10 weeks old) were injected with the tumor cells.
Approximately ten days later, 24 mice were assigned to four study groups (six mice/group) while attempting to maintain a comparable tumor size distribution in each group (average tumor size, expressed as a product of length x width of the tumor, was approximately 80mm2). The following groups were treated as indicated via tail-vain injections using a 100 1 Hamilton syringe fitted with a 25g needle:

A. Normal Saline B. Y2B8 (100 Ci) C. C2B8 (200 g); and D. Y2B8 (100 Ci) + C2B8 (200 g) Groups tested with C2B8 were given a second C2B8 injection (2004g/mouse) seven days after the initial injection. Tumor measurements were made every two or three days using a caliper.

Preparation of treatment materials were in accordance with the following protocols:

A. Preparation of Y2B8 Yttrium-[90) chloride (6mCi) was transformed to a polypropylene tube and adjusted to pH 4.1-4.4 using metal free 2M sodium acetate. 2B8-MX-DTPA

(0.3mg in normal saline; see above for preparation of 2B8-MX-DTPA) was added WO 94/11026 ; 2 149 3 29 PCT/US93/10953 and gently mixed by vortexing. After 15 min. incubation, the reaction was quenched by adding 0.05 x volume 20mM EDTA and 0.05X volume 2M sodium acetate. Radioactivity concentration was determined by diluting 5.O 1 of the reactian mixture in 2,6m1 1 x PES eontainina 75ma/ml HSA and ].:nM DTPA
("formulation buffer"); counting was accomplished by adding 10.0111 to 20m1 of' EcolumeTM scintillation cocktail. The remainder of the reactive mixture was added to 3.0ml formulation buffer, sterile filtered and stored at 2-8 C until used.
Specific activity (14mCi/mg at time of injection) was calculated using the radioactivity concentration and the calculated protein concentration based upon the amount of antibody added to the reaction mixture. Protein-associated radioactivity was determined using instant thin-layer chromatography.
Radioincorporation was 95%. Y2B8 was diluted in formulation buffer immediately before use and sterile-filtered (final radioactivity concentration was 1.0mCi/ml).

B. Preparation of C2B8 C2B8 was prepared as described above. C2B8 was provided as a sterile reagent in normal saline at 5.0mg/ml. Prior to injection, the C2B8 was diluted in normal saline to 2.0mg/ml and sterile filtered.

C. Results Following treatment, tumor size was expressed as a product of length and width, and measurements were taken on the days indicated in Figure 11 (Y2B8 vs. Saline); Figure 12 (C2B8 vs. Saline); and Figure 13 (Y2B8 + C2B8 vs.
Saline).
Standard error was also determined.

As indicated in Figure 13, the combination of Y2B8 and C2B8 exhibited tumoricidal effects comparable to the effects evidenced by either Y2B8 oi=
C2B8.

V. AI.TERNATIVE THERAPY STRATEGIES

PJternative therapeutic strategies recognized in view of the foregoing examples are evident. One such s:rategy ernploys the use of a therapeutic dose of C2BS followed within about one week with a combination of either 2B8 and radioabeled 2B8 (eC Y2BS); or 2B8, C2B8 and, eo Y2B8; or C2B8 and, eg Y2B8.
P~ additional strategy is utilization of radiolabeled C2B8 -- such a strategy allows for utilization of the benefits of the immunologically active portion of C2B8 plus those benefits associated with a radiolabel. Preferred radiolabels include yttrium-910 given the larger circulating half-life of C2B8 versus the murine antibody 2B8. Because of the ability of C2B8 to deplete B-cells, and the benefits to be derived from the use of a radiolabel, a preferred alternative strategy is to treat the patient with C2B8 (either with a single dose or multiple doses) such that most, if not all, peripheral B cells have been depleted. This would then be followed with the use of radiolabeled 2B8; because of the depletion of peripheral B cells, the radiolabeled 2B8 stands an increased chance of targeting tumor cells. Iodine [131] labeled 2B8 is preferably utilized, given the types of results reported in the literature with this label (see Kaminski). An alternative preference involves the use of a radiolabeled 2B8 (or C2B8) first in an effort to increase the permeability of a tumor, followed by single or multiple treatments with C2B8; the intent of this strategy is to increase the chances of the C2B8 in getting both outside and inside the tumor mass. A further strategy involved the use of chemotherapeutic agents in combination with C2B8. These strategies include so-called "staggered" treatments, ie, treatment with chemotherapeutic agent, followed by treatn7ent with C2B8, followed by a repetition of this protocol. Alternatively, initial treatment with a single or multiple doses of C2B8, thereafter followed with chemotherapeutic treaternent, is viable. Preferred chemotherapeutic agents include, but are not limited to:

.~~.

cyclophosphamide; doxorubicin; vincristine; and prednisone, See Armitage, J.O. et al., Cancer 50:1695 (1982).

The foregoing alternative therapy strategies are not intended to be limiting, but rather are presented as being representative.
VI. DEPOSIT INFORMATION

Anti-CD20 in TCAE 8 (transformed in E. coli for purposes of deposit) was deposited with the American Type Culture Collection (ATCC), 12301 Parklawn Drive, Rockville, Maryland, 20852, under the provisions of the Budapest Treaty for the International Recognition of the Deposit of Microorganismsm for the Purpose of Patent Procedure ("Budapest Treaty"). The microorganisms was tested by the ATCC on November 9, 1992, and determined to be viable on that date. The ATCC has assigned this microorganism for the following ATCC deposit number: ATCC 69119 (anti-CD20 in TCAE 8). Hybridoma 2B8 was deposited with the ATCC on June 22, 1993 under the provisions of the Budapest Treaty. The viability of the culture was determined on June 25, 1993 and the ATCC has assigned this hybridoma the following ATCC deposit number: HB
11388.

. . , SEQUENCE LISTING
<110> Biogen Idec Inc.
Anderson, Darrell R.
Rastetter, William H.
Hanna, Nabil Leonard, John E.
Newman, Roland Reff, Mitchell <120> THERAPEUTIC APPLICATION OF CHIMERIC AND RADIOLABELED ANTIBODIES
TO HUMAN B LYMPHOCYTE RESTRICTED DIFFERENTIATION ANTIGEN FOR
TREATMENT OF B CELL LYMPHOMA

<130> 51490-1 <140> CA 2,149,329 <141> 1993-11-13 <160> 11 <170> PatentIn version 3.2 <210> 1 <211> 8540 <212> DNA
<213> Artificial <220>
<223> vector <400> 1 gacgtcgcgg ccgctctagg cctccaaaaa agcctcctca ctacttctgg aatagctcag 60 aggccgaggc ggcctcggcc tctgcataaa taaaaaaaat tagtcagcca tgcatggggc 120 ggagaatggg cggaactggg cggagttagg ggcgggatgg gcggagttag gggcgggact 180 atggttgctg actaattgag atgcatgctt tgcatacttc tgcctgctgg ggagcctggg 240 gactttccac acctggttgc tgactaattg agatgcatgc tttgcatact tctgcctgct 300 ggggagcctg gggactttcc acaccctaac tgacacacat tccacagaat taattcccct 360 agttattaat agtaatcaat tacggggtca ttagttcata gcccatatat ggagttccgc 420 gttacataac ttacggtaaa tggcccgcct ggctgaccgc ccaacgaccc ccgcccattg 480 acgtcaataa tgacgtatgt tcccatagta acgccaatag ggactttcca ttgacgtcaa 540 tgggtggact atttacggta aactgcccac ttggcagtac atcaagtgta tcatatgcca 600 agtacgcccc ctattgacgt caatgacggt aaatggcccg cctggcatta tgcccagtac 660 atgaccttat gggactttcc tacttggcag tacatctacg tattagtcat cgctattacc 720 atggtgatgc ggttttggca gtacatcaat gggcgtggat agcggtttga ctcacgggga 780 tttccaagtc tccaccccat tgacgtcaat gggagtttgt tttggcacca aaatcaacgg 840 gactttccaa aatgtcgtaa caactccgcc ccattgacgc aaatgggcgg taggcgtgta 900 cggtgggagg tctatataag cagagctggg tacgtgaacc gtcagatcgc ctggagacgc 960 catcacagat ctctcaccat gagggtcccc gctcagctcc tggggctcct gctgctctgg 1020 ctcccaggtg cacgatgtga tggtaccaag gtggaaatca aacgtacggt ggctgcacca 1080 tctgtcttca tcttcccgcc atctgatgag cagttgaaat ctggaactgc ctctgttgtg 1140 tgcctgctga ataacttcta tcccagagag gccaaagtac agtggaaggt ggataacgcc 1200 ctccaatcgg gtaactccca ggagagtgtc acagagcagg acagcaagga cagcacctac 1260 agcctcagca gcaccctgac gctgagcaaa gcagactacg agaaacacaa agtctacgcc 1320 tgcgaagtca cccatcaggg cctgagctcg cccgtcacaa agagcttcaa caggggagag 1380 tgttgaattc agatccgtta acggttacca actacctaga ctggattcgt gacaacatgc 1440 ggccgtgata tctacgtatg atcagcctcg actgtgcctt ctagttgcca gccatctgtt 1500 gtttgcccct cccccgtgcc ttccttgacc ctggaaggtg ccactcccac tgtcctttcc 1560 taataaaatg aggaaattgc atcgcattgt ctgagtaggt gtcattctat tctggggggt 1620 ggggtggggc aggacagcaa gggggaggat tgggaagaca atagcaggca tgctggggat 1680 gcggtgggct ctatggaacc agctggggct cgacagctat gccaagtacg ccccctattg 1740 acgtcaatga cggtaaatgg cccgcctggc attatgccca gtacatgacc ttatgggact 1800 ttcctacttg gcagtacatc tacgtattag tcatcgctat taccatggtg atgcggtttt 1860 ggcagtacat caatgggcgt ggatagcggt ttgactcacg gggatttcca agtctccacc 1920 ccattgacgt caatgggagt ttgttttggc accaaaatca acgggacttt ccaaaatgtc 1980 gtaacaactc cgccccattg acgcaaatgg gcggtaggcg tgtacggtgg gaggtctata 2040 taagcagagc tgggtacgtc ctcacattca gtgatcagca ctgaacacag acccgtcgac 2100 atgggttgga gcctcatctt gctcttcctt gtcgctgttg ctacgcgtgt cgctagcacc 2160 aagggcccat cggtcttccc cctggcaccc tcctccaaga gcacctctgg gggcacagcg 2220 gccctgggct gcctggtcaa ggactacttc cccgaaccgg tgacggtgtc gtggaactca 2280 ggcgccctga ccagcggcgt gcacaccttc ccggctgtcc tacagtcctc aggactctac 2340 tccctcagca gcgtggtgac cgtgccctcc agcagcttgg gcacccagac ctacatctgc 2400 aacgtgaatc acaagcccag caacaccaag gtggacaaga aagcagagcc caaatcttgt 2460 gacaaaactc acacatgccc accgtgccca gcacctgaac tcctgggggg accgtcagtc 2520 ttcctcttcc ccccaaaacc caaggacacc ctcatgatct cccggacccc tgaggtcaca 2580 tgcgtggtgg tggacgtgag ccacgaagac cctgaggtca agttcaactg gtacgtggac 2640 ggcgtggagg tgcataatgc caagacaaag ccgcgggagg agcagtacaa cagcacgtac 2700 cgtgtggtca gcgtcctcac cgtcctgcac caggactggc tgaatggcaa ggactacaag 2760 tgcaaggtct ccaacaaagc cctcccagcc cccatcgaga aaaccatctc caaagccaaa 2820 gggcagcccc gagaaccaca ggtgtacacc ctgcccccat cccgggatga gctgaccagg 2880 aaccaggtca gcctgacctg cctggtcaaa ggcttctatc ccagcgacat cgccgtggag 2940 tgggagagca atgggcagcc ggagaacaac tacaagacca cgcctcccgt gctggactcc 3000 gacggctcct tcttcctcta cagcaagctc accgtggaca agagcaggtg gcagcagggg 3060 aacgtcttct catgctccgt gatgcatgag gctctgcaca accactacac gcagaagagc 3120 ctctccctgt ctccgggtaa atgaggatcc gttaacggtt accaactacc tagactggat 3180 tcgtgacaac atgcggccgt gatatctacg tatgatcagc ctcgactgtg ccttctagtt 3240 gccagccatc tgttgtttgc ccctcccccg tgccttcctt gaccctggaa ggtgccactc 3300 ccactgtcct ttcctaataa aatgaggaaa ttgcatcgca ttgtctgagt aggtgtcatt 3360 ctattctggg gggtggggtg gggcaggaca gcaaggggga ggattgggaa gacaatagca 3420 ggcatgctgg ggatgcggtg ggctctatgg aaccagctgg ggctcgacag cgctggatct 3480 cccgatcccc agctttgctt ctcaatttct tatttgcata atgagaaaaa aaggaaaatt 3540 aattttaaca ccaattcagt agttgattga gcaaatgcgt tgccaaaaag gatgctttag 3600 agacagtgtt ctctgcacag ataaggacaa acattattca gagggagtac ccagagctga 3660 gactcctaag ccagtgagtg gcacagcatt ctagggagaa atatgcttgt catcaccgaa 3720 gcctgattcc gtagagccac accttggtaa gggccaatct gctcacacag gatagagagg 3780 gcaggagcca gggcagagca tataaggtga ggtaggatca gttgctcctc acatttgctt 3840 ctgacatagt tgtgttggga gcttggatag cttggacagc tcagggctgc gatttcgcgc 3900 caaacttgac ggcaatccta gcgtgaaggc tggtaggatt ttatccccgc tgccatcatg 3960 gttcgaccat tgaactgcat cgtcgccgtg tcccaaaata tggggattgg caagaacgga 4020 gacctaccct ggcctccgct caggaacgag ttcaagtact tccaaagaat gaccacaacc 4080 tcttcagtgg aaggtaaaca gaatctggtg attatgggta ggaaaacctg gttctccatt 4140 cctgagaaca atcgaccttt aaaggacaga attaatatag ttctcagtag agaactcaaa 4200 gaaccaccac gaggagctca ttttcttgcc aaaagtttgg atgatgcctt aagacttatt 4260 gaacaaccgg aattggcaag taaagtagac atggtttgga tagtcggagg cagttctgtt 4320 taccaggaag ccatgaatca accaggccac cttagactct ttgtgacaag gatcatgcag 4380 gaatttgaaa gtgacacgtt tttcccagaa attgatttgg ggaaatataa acttctccca 4440 gaatacccag gcgtcctctc tgaggtccag gaggaaaaag gcatcaagta taagtttgaa 4500 gtctacgaga agaaagacta acaggaagat gctttcaagt tctctgctcc cctcctaaag 4560 tcatgcattt ttataagacc atgggacttt tgctggcttt agatcagcct cgactgtgcc 4620 ttctagttgc cagccatctg ttgtttgccc ctcccccgtg ccttccttga ccctggaagg 4680 tgccactccc actgtccttt cctaataaaa tgaggaaatt gcatcgcatt gtctgagtag 4740 gtgtcattct attctggggg gtggggtggg gcaggacagc aagggggagg attgggaaga 4800 caatagcagg catgctgggg atgcggtggg ctctatggaa ccagctgggg ctcgagctac 4860 tagctttgct tctcaatttc ttatttgcat aatgagaaaa aaaggaaaat taattttaac 4920 accaattcag tagttgattg agcaaatgcg ttgccaaaaa ggatgcttta gagacagtgt 4980 tctctgcaca gataaggaca aacattattc agagggagta cccagagctg agactcctaa 5040 gccagtgagt ggcacagcat tctagggaga aatatgcttg tcatcaccga agcctgattc 5100 cgtagagcca caccttggta agggccaatc tgctcacaca ggatagagag ggcaggagcc 5160 agggcagagc atataaggtg aggtaggatc agttgctcct cacatttgct tctgacatag 5220 ttgtgttggg agcttggatc gatcctctat ggttgaacaa gatggattgc acgcaggttc 5280 tccggccgct tgggtggaga ggctattcgg ctatgactgg gcacaacaga caatcggctg 5340 ctctgatgcc gccgtgttcc ggctgtcagc gcaggggcgc ccggttcttt ttgtcaagac 5400 cgacctgtcc ggtgccctga atgaactgca ggacgaggca gcgcggctat cgtggctggc 5460 cacgacgggc gttccttgcg cagctgtgct cgacgttgtc actgaagcgg gaagggactg 5520 gctgctattg ggcgaagtgc cggggcagga tctcctgtca tctcaccttg ctcctgccga 5580 gaaagtatcc atcatggctg atgcaatgcg gcggctgcat acgcttgatc cggctacctg 5640 cccattcgac caccaagcga aacatcgcat cgagcgagca cgtactcgga tggaagccgg 5700 tcttgtcgat caggatgatc tggacgaaga gcatcagggg ctcgcgccag ccgaactgtt 5760 cgccaggctc aaggcgcgca tgcccgacgg cgaggatctc gtcgtgaccc atggcgatgc 5820 ctgcttgccg aatatcatgg tggaaaatgg ccgcttttct ggattcatcg actgtggccg 5880 gctgggtgtg gcggaccgct atcaggacat agcgttggct acccgtgata ttgctgaaga 5940 gcttggcggc gaatgggctg accgcttcct cgtgctttac ggtatcgccg ctcccgattc 6000 gcagcgcatc gccttctatc gccttcttga cgagttcttc tgagcgggac tctggggttc 6060 gaaatgaccg accaagcgac gcccaacctg ccatcacgag atttcgattc caccgccgcc 6120 ttctatgaaa ggttgggctt cggaatcgtt ttccgggacg ccggctggat gatcctccag 6180 cgcggggatc tcatgctgga gttcttcgcc caccccaact tgtttattgc agcttataat 6240 ggttacaaat aaagcaatag catcacaaat ttcacaaata aagcattttt ttcactgcat 6300 tctagttgtg gtttgtccaa actcatcaat ctatcttatc atgtctggat cgcggccgcg 6360 atcccgtcga gagcttggcg taatcatggt catagctgtt tcctgtgtga aattgttatc 6420 cgctcacaat tccacacaac atacgagccg gaagcataaa gtgtaaagcc tggggtgcct 6480 aatgagtgag ctaactcaca ttaattgcgt tgcgctcact gcccgctttc cagtcgggaa 6540 acctgtcgtg ccagctgcat taatgaatcg gccaacgcgc ggggagaggc ggtttgcgta 6600 ttgggcgctc ttccgcttcc tcgctcactg actcgctgcg ctcggtcgtt cggctgcggc 6660 gagcggtatc agctcactca aaggcggtaa tacggttatc cacagaatca ggggataacg 6720 caggaaagaa catgtgagca aaaggccagc aaaaggccag gaaccgtaaa aaggccgcgt 6780 tgctggcgtt tttccatagg ctccgccccc ctgacgagca tcacaaaaat cgacgctcaa 6840 gtcagaggtg gcgaaacccg acaggactat aaagatacca ggcgtttccc cctggaagct 6900 ccctcgtgcg ctctcctgtt ccgaccctgc cgcttaccgg atacctgtcc gcctttctcc 6960 cttcgggaag cgtggcgctt tctcaatgct cacgctgtag gtatctcagt tcggtgtagg 7020 tcgttcgctc caagctgggc tgtgtgcacg aaccccccgt tcagcccgac cgctgcgcct 7080 tatccggtaa ctatcgtctt gagtccaacc cggtaagaca cgacttatcg ccactggcag 7140 cagccactgg taacaggatt agcagagcga ggtatgtagg cggtgctaca gagttcttga 7200 agtggtggcc taactacggc tacactagaa ggacagtatt tggtatctgc gctctgctga 7260 agccagttac cttcggaaaa agagttggta gctcttgatc cggcaaacaa accaccgctg 7320 gtagcggtgg tttttttgtt tgcaagcagc agattacgcg cagaaaaaaa ggatctcaag 7380 aagatccttt gatcttttct acggggtctg acgctcagtg gaacgaaaac tcacgttaag 7440 ggattttggt catgagatta tcaaaaagga tcttcaccta gatcctttta aattaaaaat 7500 gaagttttaa atcaatctaa agtatatatg agtaaacttg gtctgacagt taccaatgct 7560 taatcagtga ggcacctatc tcagcgatct gtctatttcg ttcatccata gttgcctgac 7620 tccccgtcgt gtagataact acgatacggg agggcttacc atctggcccc agtgctgcaa 7680 tgataccgcg agacccacgc tcaccggctc cagatttatc agcaataaac cagccagccg 7740 gaagggccga gcgcagaagt ggtcctgcaa ctttatccgc ctccatccag tctattaatt 7800 gttgccggga agctagagta agtagttcgc cagttaatag tttgcgcaac gttgttgcca 7860 ttgctacagg catcgtggtg tcacgctcgt cgtttggtat ggcttcattc agctccggtt 7920 cccaacgatc aaggcgagtt acatgatccc ccatgttgtg caaaaaagcg gttagctcct 7980 tcggtcctcc gatcgttgtc agaagtaagt tggccgcagt gttatcactc atggttatgg 8040 cagcactgca taattctctt actgtcatgc catccgtaag atgcttttct gtgactggtg 8100 agtactcaac caagtcattc tgagaatagt gtatgcggcg accgagttgc tcttgcccgg 8160 cgtcaatacg ggataatacc gcgccacata gcagaacttt aaaagtgctc atcattggaa 8220 aacgttcttc ggggcgaaaa ctctcaagga tcttaccgct gttgagatcc agttcgatgt 8280 aacccactcg tgcacccaac tgatcttcag catcttttac tttcaccagc gtttctgggt 8340 gagcaaaaac aggaaggcaa aatgccgcaa aaaagggaat aagggcgaca cggaaatgtt 8400 gaatactcat actcttcctt tttcaatatt attgaagcat ttatcagggt tattgtctca 8460 tgagcggata catatttgaa tgtatttaga aaaataaaca aataggggtt ccgcgcacat 8520 ttccccgaaa agtgccacct 8540 <210> 2 <211> 9209 <212> DNA
<213> Artificial <220>
<223> vector with chimeric antibody sequence <400> 2 gacgtcgcgg ccgctctagg cctccaaaaa agcctcctca ctacttctgg aatagctcag 60 aggccgaggc ggcctcggcc tctgcataaa taaaaaaaat tagtcagcca tgcatggggc 120 ggagaatggg cggaactggg cggagttagg ggcgggatgg gcggagttag gggcgggact 180 atggttgctg actaattgag atgcatgctt tgcatacttc tgcctgctgg ggagcctggg 240 gactttccac acctggttgc tgactaattg agatgcatgc tttgcatact tctgcctgct 300 ggggagcctg gggactttcc acaccctaac tgacacacat tccacagaat taattcccct 360 agttattaat agtaatcaat tacggggtca ttagttcata gcccatatat ggagttccgc 420 gttacataac ttacggtaaa tggcccgcct ggctgaccgc ccaacgaccc ccgcccattg 480 acgtcaataa tgacgtatgt tcccatagta acgccaatag ggactttcca ttgacgtcaa 540 tgggtggact atttacggta aactgcccac ttggcagtac atcaagtgta tcatatgcca 600 agtacgcccc ctattgacgt caatgacggt aaatggcccg cctggcatta tgcccagtac 660 atgaccttat gggactttcc tacttggcag tacatctacg tattagtcat cgctattacc 720 atggtgatgc ggttttggca gtacatcaat gggcgtggat accggtttga ctcacgcgga 780 tttccaagtc tccaccccat tgacgtcaat gggagtttgt tttggcacca aaatcaacgg 840 gactttccaa aatgtcgtaa caactccgcc ccattgacgc aaatgggcgg taggcgtgta 900 cggtgggagg tctatataag cagagctggg tacgtgaacc gtcagatcgc ctggagacgc 960 catcacagat ctctcactat ggattttcag gtgcagatta tcagcttcct gctaatcagt 1020 gcttcagtca taatgtccag aggacaaatt gttctctccc agtctccagc aatcctgtct 1080 gcatctccag gggagaaggt cacaatgact tgcagggcca gctcaagtgt aagttacatc 1140 cactggttcc agcagaagcc aggatcctcc cccaaaccct ggatttatgc cacatccaac 1200 ctggcttctg gagtccctgt tcgcttcagt ggcagtgggt ctgggacttc ttactctctc 1260 acaatcagca gagtggaggc tgaagatgct gccacttatt actgccagca gtggactagt 1320 aacccaccca cgttcggagg ggggaccaag ctggaaatca aacgtacggt ggctgcacca 1380 tctgtcttca tcttcccgcc atctgatgag cagttgaaat ctggaactgc ctctgttgtg 1440 tgcctgctga ataacttcta tcccagagag gccaaagtac agtggaaggt ggataacgcc 1500 ctccaatcgg gtaactccca ggagagtgtc acagagcagg acagcaagga cagcacctac 1560 agcctcagca gcaccctgac gctgagcaaa gcagactacg agaaacacaa agtctacgcc 1620 tgcgaagtca cccatcaggg cctgagctcg cccgtcacaa agagcttcaa caggggagag 1680 tgttgaattc agatccgtta acggttacca actacctaga ctggattcgt gacaacatgc 1740 ggccgtgata tctacgtatg atcagcctcg actgtgcctt ctagttgcca gccatctgtt 1800 gtttgcccct cccccgtgcc ttccttgacc ctggaaggtg ccactcccac tgtcctttcc 1860 taataaaatg aggaaattgc atcgcattgt ctgagtaggt gtcattctat tctggggggt 1920 ggggtggggc aggacagcaa gggggaggat tgggaagaca atagcaggca tgctggggat 1980 gcggtgggct ctatggaacc agctggggct cgacagctat gccaagtacg ccccctattg 2040 acgtcaatga cggtaaatgg cccgcctggc attatgccca gtacatgacc ttatgggact 2100 ttcctacttg gcagtacatc tacgtattag tcatcgctat taccatggtg atgcggtttt 2160 ggcagtacat caatgggcgt ggatagcggt ttgactcacg gggatttcca agtctccacc 2220 ccattgacgt caatgggagt ttgttttggc accaaaatca acgggacttt ccaaaatgtc 2280 gtaacaactc cgccccattg acgcaaatgg gcggtaggcg tgtacggtgg gaggtctata 2340 taagcagagc tgggtacgtc ctcacattca gtgatcagca ctgaacacag acccgtcgac 2400 atgggttgga gcctcatctt gctcttcctt gtcgctgttg ctacgcgtgt cctgtcccag 2460 gtacaactgc agcagcctgg ggctgagctg gtgaagcctg gggcctcagt gaagatgtcc 2520 tgcaaggctt ctggctacac atttaccagt tacaatatgc actgggtaaa acagacacct 2580 ggtcggggcc tggaatggat tggagctatt tatcccggaa atggtgatac ttcctacaat 2640 cagaagttca aaggcaaggc cacattgact gcagacaaat cctccagcac agcctacatg 2700 cagctcagca gcctgacatc tgaggactct gcggtctatt actgtgcaag atcgacttac 2760 tacggcggtg actggtactt caatgtctgg ggcgcaggga ccacggtcac cgtctctgca 2820 gctagcacca agggcccatc ggtcttcccc ctggcaccct cctccaagag cacctctggg 2880 ggcacagcgg ccctgggctg cctggtcaag gactacttcc ccgaaccggt gacggtgtcg 2940 tggaactcag gcgccctgac cagcggcgtg cacaccttcc cggctgtcct acagtcctca 3000 ggactctact ccctcagcag cgtggtgacc gtgccctcca gcagcttggg cacccagacc 3060 tacatctgca acgtgaatca caagcccagc aacaccaagg tggacaagaa agcagagccc 3120 aaatcttgtg acaaaactca cacatgccca ccgtgcccag cacctgaact cctgggggga 3180 ccgtcagtct tcctcttccc cccaaaaccc aaggacaccc tcatgatctc ccggacccct 3240 gaggtcacat gcgtggtggt ggacgtgagc cacgaagacc ctgaggtcaa gttcaactgg 3300 tacgtggacg gcgtggaggt gcataatgcc aagacaaagc cgcgggagga gcagtacaac 3360 agcacgtacc gtgtggtcag cgtcctcacc gtcctgcacc aggactggct gaatggcaag 3420 gagtacaagt gcaaggtctc caacaaagcc ctcccagccc ccatcgagaa aaccatctcc 3480 aaagccaaag ggcagccccg agaaccacag gtgtacaccc tgcccccatc ccgggatgag 3540 ctgaccaaga accaggtcag cctgacctgc ctggtcaaag gcttctatcc cagcgacatc 3600 gccgtggagt gggagagcaa tgggcagccg gagaacaact acaagaccac gcctcccgtg 3660 ctggactccg acggctcctt cttcctctac agcaagctca ccgtggacaa gagcaggtgg 3720 cagcagggga acgtcttctc atgctccgtg atgcatgagg ctctgcacaa ccactacacg 3780 cagaagagcc tctccctgtc tccgggtaaa tgaggatccg ttaacggtta ccaactacct 3840 agactggatt cgtgacaaca tgcggccgtg atatctacgt atgatcagcc tcgactgtgc 3900 cttctagttg ccagccatct gttgtttgcc cctcccccgt gccttccttg accctggaag 3960 gtgccactcc cactgtcctt tcctaataaa atgaggaaat tgcatcgcat tgtctgagta 4020 ggtgtcattc tattctgggg ggtggggtgg ggcaggacag caagggggag gattgggaag 4080 acaatagcag gcatgctggg gatgcggtgg gctctatgga accagctggg gctcgacagc 4140 gctggatctc ccgatcccca gctttgcttc tcaatttctt atttgcataa tgagaaaaaa 4200 aggaaaatta attttaacac caattcagta gttgattgag caaatgcgtt gccaaaaagg 4260 atgctttaga gacagtgttc tctgcacaga taaggacaaa cattattcag agggagtacc 4320 cagagctgag actcctaagc cagtgagtgg cacagcattc tagggagaaa tatgcttgtc 4380 atcaccgaag cctgattccg tagagccaca ccttggtaag ggccaatctg ctcacacagg 4440 atagagaggg caggagccag ggcagagcat ataaggtgag gtaggatcag ttgctcctca 4500 . ,.

catttgcttc tgacatagtt gtgttgggag cttggatagc ttggacagct cagggctgcg 4560 atttcgcgcc aaacttgacg gcaatcctag cgtgaaggct ggtaggattt tatccccgct 4620 gccatcatgg ttcgaccatt gaactgcatc gtcgccgtgt cccaaaatat ggggattggc 4680 aagaacggag acctaccctg gcctccgctc aggaacgagt tcaagtactt ccaaagaatg 4740 accacaacct cttcagtgga aggtaaacag aatctggtga ttatgggtag gaaaacctgg 4800 ttctccattc ctgagaagaa tcgaccttta aaggacagaa ttaatatagt tctcagtaga 4860 gaactcaaag aaccaccacg aggagctcat tttcttgcca aaagtttgga tgatgcctta 4920 agacttattg aacaaccgga attggcaagt aaagtagaca tggtttggat agtcggaggc 4980 agttctgttt accaggaagc catgaatcaa ccaggccacc ttagactctt tgtgacaagg 5040 atcatgcagg aatttgaaag tgacacgttt ttcccagaaa ttgatttggg gaaatataaa 5100 cttctcccag aatacccagg cgtcctctct gaggtccagg aggaaaaagg catcaagtat 5160 aagtttgaag tctacgagaa gaaagactaa caggaagatg ctttcaagtt ctctgctccc 5220 ctcctaaagc tatgcatttt tataagacca tgggactttt gctggcttta gatcagcctc 5280 gactgtgcct tctagttgcc agccatctgt tgtttgcccc tcccccgtgc cttccttgac 5340 cctggaaggt gccactccca ctgtcctttc ctaataaaat gaggaaattg catcgcattg 5400 tctgagtagg tgtcattcta ttctgggggg tggggtgggg caggacagca agggggagga 5460 ttgggaagac aatagcaggc atgctgggga tgcggtgggc tctatggaac cagctggggc 5520 tcgagctact agctttgctt ctcaatttct tatttgcata atgagaaaaa aaggaaaatt 5580 aattttaaca ccaattcagt agttgattga gcaaatgcgt tgccaaaaag gatgctttag 5640 agacagtgtt ctctgcacag ataaggacaa acattattca gagggagtac ccagagctga 5700 gactcctaag ccagtgagtg gcacagcatt ctagggagaa atatgcttgt catcaccgaa 5760 gcctgattcc gtagagccac accttggtaa gggccaatct gctcacacag gatagagagg 5820 gcaggagcca gggcagagca tataaggtga ggtaggatca gttgctcctc acatttgctt 5880 ctgacatagt tgtgttggga gcttggatcg atcctctatg gttgaacaag atggattgca 5940 cgcaggttct ccggccgctt gggtggagag gctattcggc tatgactggg cacaacagac 6000 aatcggctgc tctgatgccg ccgtgttccg gctgtcagcg caggggcgcc cggttctttt 6060 tgtcaagacc gacctgtccg gtgccctgaa tgaactgcag gacgaggcag cgcggctatc 6120 gtggctggcc acgacgggcg ttccttgcgc agctgtgctc gacgttgtca ctgaagcggg 6180 aagggactgg ctgctattgg gcgaagtgcc ggggcaggat ctcctgtcat ctcaccttgc 6240 tcctgccgag aaagtatcca tcatggctga tgcaatgcgg cggctgcata cgcttgatcc 6300 . ..

ggctacctgc ccattcgacc accaagcgaa acatcgcatc gagcgagcac gtactcggat 6360 ggaagccggt cttgtcgatc aggatgatct ggacgaagag catcaggggc tcgcgccagc 6420 cgaactgttc gccaggctca aggcgcgcat gcccgacggc gaggatctcg tcgtgaccca 6480 tggcgatgcc tgcttgccga atatcatggt ggaaaatggc cgcttttctg gattcatcga 6540 ctgtggccgg ctgggtgtgg cggaccgcta tcaggacata gcgttggcta cccgtgatat 6600 tgctgaagag cttggcggcg aatgggctga ccgcttcctc gtgctttacg gtatcgccgc 6660 tcccgattcg cagcgcatcg ccttctatcg ccttcttgac gagttcttct gagcgggact 6720 ctggggttcg aaatgaccga ccaagcgacg cccaacctgc catcacgaga tttcgattcc 6780 accgccgcct tctatgaaag gttgggcttc ggaatcgttt tccgggacgc cggctggatg 6840 atcctccagc gcggggatct catgctggag ttcttcgccc accccaactt gtttattgca 6900 gcttataatg gttacaaata aagcaatagc atcacaaatt tcacaaataa agcatttttt 6960 tcactgcatt ctagttgtgg tttgtccaaa ctcatcaatc tatcttatca tgtctggatc 7020 gcggccgcga tcccgtcgag agcttggcgt aatcatggtc atagctgttt cctgtgtgaa 7080 attgttatcc gctcacaatt ccacacaaca tacgagccgg aagcataaag tgtaaagcct 7140 ggggtgccta atgagtgagc taactcacat taattgcgtt gcgctcactg cccgctttcc 7200 agtcgggaaa cctgtcgtgc cagctgcatt aatgaatcgg ccaacgcgcg gggagaggcg 7260 gtttgcgtat tgggcgctct tccgcttcct cgctcactga ctcgctgcgc tcggtcgttc 7320 ggctgcggcg agcggtatca gctcactcaa aggcggtaat acggttatcc acagaatcag 7380 gggataacgc aggaaagaac atgtgagcaa aaggccagca aaaggccagg aaccgtaaaa 7440 aggccgcgtt gctggcgttt ttccataggc tccgcccccc tgacgagcat cacaaaaatc 7500 gacgctcaag tcagaggtgg cgaaacccga caggactata aagataccag gcgtttcccc 7560 ctggaagctc cctcgtgcgc tctcctgttc cgaccctgcc gcttaccgga tacctgtccg 7620 cctttctccc ttcgggaagc gtggcgcttt ctcaatgctc acgctgtagg tatctcagtt 7680 cggtgtaggt cgttcgctcc aagctgggct gtgtgcacga accccccgtt cagcccgacc 7740 gctgcgcctt atccggtaac tatcgtcttg agtccaaccc ggtaagacac gacttatcgc 7800 cactggcagc agccactggt aacaggatta gcagagcgag gtatgtaggc ggtgctacag 7860 agttcttgaa gtggtggcct aactacggct acactagaag gacagtattt ggtatctgcg 7920 ctctgctgaa gccagttacc ttcggaaaaa gagttggtag ctcttgatcc ggcaaacaaa 7980 ccaccgctgg tagcggtggt ttttttgttt gcaagcagca gattacgcgc agaaaaaaag 8040 gatctcaaga agatcctttg atcttttcta cggggtctga cgctcagtgg aacgaaaact 8100 cacgttaagg gattttggtc atgagattat caaaaaggat cttcacctag atccttttaa 8160 attaaaaatg aagttttaaa tcaatctaaa gtatatatga gtaaacttgg tctgacagtt 8220 accaatgctt aatcagtgag gcacctatct cagcgatctg tctatttcgt tcatccatag 8280 ttgcctgact ccccgtcgtg tagataacta cgatacggga gggcttacca tctggcccca 8340 gtgctgcaat gataccgcga gacccacgct caccggctcc agatttatca gcaataaacc 8400 agccagccgg aagggccgag cgcagaagtg gtcctgcaac tttatccgcc tccatccagt 8460 ctattaattg ttgccgggaa gctagagtaa gtagttcgcc agttaatagt ttgcgcaacg 8520 ttgttgccat tgctacaggc atcgtggtgt cacgctcgtc gtttggtatg gcttcattca 8580 gctccggttc ccaacgatca aggcgagtta catgatcccc catgttgtgc aaaaaagcgg 8640 ttagctcctt cggtcctccg atcgttgtca gaagtaagtt ggccgcagtg ttatcactca 8700 tggttatggc agcactgcat aattctctta ctgtcatgcc atccgtaaga tgcttttctg 8760 tgactggtga gtactcaacc aagtcattct gagaatagtg tatgcggcga ccgagttgct 8820 cttgcccggc gtcaatacgg gataataccg cgccacatag cagaacttta aaagtgctca 8880 tcattggaaa acgttcttcg gggcgaaaac tctcaaggat cttaccgctg ttgagatcca 8940 gttcgatgta acccactcgt gcacccaact gatcttcagc atcttttact ttcaccagcg 9000 tttctgggtg agcaaaaaca ggaaggcaaa atgccgcaaa aaagggaata agggcgacac 9060 ggaaatgttg aatactcata ctcttccttt ttcaatatta ttgaagcatt tatcagggtt 9120 attgtctcat gagcggatac atatttgaat gtatttagaa aaataaacaa ataggggttc 9180 cgcgcacatt tccccgaaaa gtgccacct 9209 <210> 3 <211> 384 <212> DNA
<213> Mus musculus <400> 3 atggattttc aggtgcagat tatcagcttc ctgctaatca gtgcttcagt cataatgtcc 60 agagggcaaa ttgttctctc ccagtctcca gcaatcctgt ctgcatctcc aggggagaag 120 gtcacaatga cttgcagggc cagcctgtct gcatctccag gggagaaggt cacaatgact 180 tgcagggcca gccccaaacc ctggatttat gccacatcca acctggcttc tggagtccct 240 gttcgcttca gtggcagtgg gtctgggact tcttactctc tcacaatcag cagagtggag 300 gctgaagatg ctgccactta ttactgccag cagtggacta gtaacccacc cacgttcgga 360 ggggggacca agctggaaat caaa 384 <210> 4 <211> 128 <212> PRT
<213> Mus musculus <400> 4 Met Asp Phe Gln Val Gln Ile Ile Ser Phe Leu Leu Ile Ser Ala Ser Val Ile Met Ser Arg Gly Gln Ile Val Leu Ser Gln Ser Pro Ala Ile Leu Ser Ala Ser Pro Gly Glu Lys Val Thr Met Thr Cys Arg Ala Ser Ser Ser Val Ser Tyr Ile His Trp Phe Gln Gin Lys Pro Gly Ser Ser Pro Lys Pro Trp Ile Tyr Ala Thr Ser Asn Leu Ala Ser Gly Val Pro Val Arg Phe Ser Gly Ser Gly Ser Gly Thr Ser Tyr Ser Leu Thr Ile Ser Arg Val Glu Ala Glu Asp Ala Ala Thr Tyr Tyr Cys Gln Gln Trp Thr Ser Asn Pro Pro Thr Phe Gly Gly Gly Thr Lys Leu Glu Ile Lys <210> 5 <211> 420 <212> DNA
<213> Mus musculus <400> 5 atgggttgga gcctcatctt gctcttcctt gtcgctgttg ctacgcgtgt cctgtcccag 60 gtacaactgc agcagcctgg ggctgagctg gtgaagcctg gggcctcagt gaagatgtcc 120 tgcaaggctt ctggctacac atttaccagt tacaatatgc actgggtaaa acagacacct 180 ggtcggggcc tggaatggat tggagctatt tatcccggaa atggtgatac ttcctacaat 240 cagaagttca aaggcaaggc cacattgact gcagacaaat cctccagcac agcctacatg 300 cagctcagca gcctgacatc tgaggactct gcggtctatt actgtgcaag atcgacttac 360 tacggcggtg actggtactt caatgtctgg ggcgcaggga ccacggtcac cgtctctgca 420 <210> 6 <211> 140 <212> PRT
<213> Mus musculus <400> 6 Met Gly Trp Ser Leu Ile Leu Leu Phe Leu Val Ala Val Ala Thr Arg . . , Val Leu Ser Gln Val Gln Leu Gln Gln Pro Gly Ala Glu Leu Val Lys Pro Gly Ala Ser Val Lys Met Ser Cys Lys Ala Ser Gly Tyr Thr Phe Thr Ser Tyr Asn Met His Trp Val Lys Gln Thr Pro Gly Arg Gly Leu Glu Trp Ile Gly Ala Ile Tyr Pro Gly Asn Gly Asp Thr Ser Tyr Asn Gln Lys Phe Lys Gly Lys Ala Thr Leu Thr Ala Asp Lys Ser Ser Ser Thr Ala Tyr Met Gln Leu Ser Ser Leu Thr Ser Glu Asp Ser Ala Val Tyr Tyr Cys Ala Arg Ser Thr Tyr Tyr Gly Gly Asp Trp Tyr Phe Asn Val Trp Gly Ala Gly Thr Thr Val Thr Val Ser Ala <210> 7 <211> 27 <212> DNA
<213> Artificial <220>
<223> impaired Kozak sequence and restriction enzyme site <400> 7 gggagcttgg atcgatcctc tatggtt 27 <210> 8 <211> 47 <212> DNA
<213> Artificial <220>
<223> PCR Primer <400> 8 atcacagatc tctcaccatg gattttcagg tgcagattat cagcttc 47 <210> 9 <211> 30 <212> DNA
<213> Artificial <220>
<223> PCR Primer <400> 9 tgcagcatcc gtacgtttga tttccagctt 30 <210> 10 <211> 27 <212> DNA
<213> Artificial <220>
<223> PCR Primer <400> 10 gcggctccca cgcgtgtcct gtcccag 27 <210> 11 <211> 29 <212> DNA
<213> Artificial <220>
<223> PCR Primer <220>
<221> miscfeature <222> (1) ._(29) <223> s is g or c <220>
<221> miscfeature <222> (1) ._(29) <223> m is a or c <220>
<221> miscfeature <222> (1) ._(29) <223> r is g or a <400> 11 ggstgttgtg ctagctgmrg agacrgtga 29

Claims (18)

CLAIMS:

1. An isolated monoclonal antibody, wherein the antibody comprises a light chain variable region comprising amino acid residues 23 to 128 of SEQ ID NO:4 and a heavy chain variable region comprising amino acid residues 20 to 140 of SEQ ID NO:6.

2. A monoclonal antibody according to claim 1, wherein the antibody is an immunologically active chimeric antibody further comprising human constant regions.

3. A monoclonal antibody according to claim 2, wherein the heavy chain constant region is a human gamma 1 heavy chain constant region.

4. A monoclonal antibody according to claim 3, wherein the light chain constant region is a human kappa light chain constant region.

5. A monoclonal antibody according to claim 4, wherein the kappa light chain and gamma 1 heavy chain have the amino acid sequences encoded by the heavy and light chain inserts in the vector nucleotide sequence shown in SEQ
ID NO:2.

6. A monoclonal antibody according to claim 1, wherein the antibody is a murine antibody.

7. A monoclonal antibody according to claim 6, wherein the antibody is obtainable from a hybridoma deposited under American Type Culture Collection (ATCC) No. HB 11388.

8. An immunologically active chimeric anti-CD20 antibody, wherein the antibody possesses substantially the same B-cell depleting activity and has specificity to the same epitope of CD20 as an anti-CD20 antibody comprising the heavy chain and light chain polypeptides encoded by the heavy and light chain inserts in the vector nucleotide sequence shown in SEQ ID NO:2.

9. A monoclonal antibody according to any one of claims 1 to 8, further comprising a chelating agent for conjugating a radiolabel to the antibody.

10. A monoclonal antibody according to any one of claims 1 to 9, further comprising a radiolabel.

11. A monoclonal antibody according to claim 10, wherein the radiolabel is selected from yttrium-90, indium-111, and iodine-131.

12. A monoclonal antibody according to claim 11, wherein the radiolabel is yttrium-90.

13. A host cell comprising nucleic acid sequences encoding the light chain and the heavy chain of an immunologically active chimeric anti-CD20 antibody, wherein the sequence encoding the light chain comprises a nucleotide sequence encoding amino acid residues 23 to 128 of SEQ ID
NO:4, and the sequence encoding the heavy chain comprises a nucleotide sequence encoding amino acid residues 20 to 140 of SEQ ID NO:6.

14. A host cell according to claim 13, wherein the host cell is a mammalian host cell.

15. A host cell according to claim 14, wherein the host cell is a CHO cell or SP2/0 cell.

16. A host cell according to claim 15, wherein the host cell is a DG44 cell.

17. A method of producing a chimeric anti-CD20 antibody comprising:

(a) culturing a host cell according to any one of claims 13 to 16 under conditions to produce the chimeric anti-CD20 antibody and (b) harvesting the chimeric anti-CD20 antibody.

18. A chimeric anti-CD20 antibody made according to the method of claim 17.