Remission induction in non-Hodgkin lymphoma with reshaped human monoclonal antibody CAMPATH-1H

Development of humanized bispecific antibodies reactive with cytotoxic lymphocytes and tumor cells overexpressing the HER2 protooncogene

The HER2 protooncogene encodes a 185-kD transmembrane phosphoglycoproteins, human epidermal growth factor receptor 2 (p185HER2), whose amplified expression on the cell surface can lead to malignant transformation. Overexpression of HER2/p185HER2 is strongly correlated with progression of human ovarian and breast carcinomas. Recent studies have shown that human T cells can be targeted with bispecific antibody to react against human tumor cells in vitro. We have developed a bispecific F(ab')2 antibody molecule consisting of a humanized arm with a specificity to p185HER2 linked to another arm derived from a murine anti-CD3 monoclonal antibody that we have cloned from UCHT1 hybridoma. The antigen-binding loops for the anti-CD3 were installed in the context of human variable region framework residues, thus forming a fully humanized BsF(ab')2 fragment. Additional variants were produced by replacement of amino acid residues located in light chain complementarity determining region 2 and heavy chain framework region 3 of the humanized anti-CD3 arm. Flow cytometry analysis showed that the bispecific F(ab')2 molecules can bind specifically to cells overexpressing p185HER2 and to normal human peripheral blood mononuclear cells bearing the CD3 surface marker. In additional experiments, the presence of bispecific F(ab')2 caused up to fourfold enhancement in the cytotoxic activities of human T cells against tumor cells overexpressing p185HER2 as determined by a 51Cr release assay. These bispecific molecules have a potential use as therapeutic agents for the treatment of cancer.

High Level Escherichia coli Expression and Production of a Bivalent Humanized Antibody Fragment

Many clinical uses of antibodies will require large quantities of fragments which are bivalent and humanized. We therefore attempted to generate humanized F(ab')2 fragments by secretion from E. coli. Titers of 1-2 g l-1 of soluble and functional Fab' fragments have been routinely achieved as judged by antigen-binding ELISA. Surprisingly, this high expression level of Fab' in the periplasmic space of E. coli does not drive dimerization. However, we have developed a protocol to directly and efficiently recover Fab' with the single hinge cysteine in the free thiol state, allowing F(ab')2 formation by chemically-directed coupling in vitro. The E. coli derived humanized F(ab')2 fragment is indistinguishable from F(ab')2 derived from limited proteolysis of intact antibody in its binding affinity for the antigen, p185HER2, and anti-proliferative activity against the human breast tumor cell line, SK-BR-3, which over-expresses p185HER2. This system makes E. coli expression of bivalent antibody fragments for human therapy (or other uses) practical.

Rapid isolation of immunoglobulin variable genes from cell lysates of rat hybridomas by polymerase chain reaction

The isolation of the rearranged immunoglobulin genes from a hybridoma cell line, which is a prerequisite for the construction of a recombinant antibody, can easily be achieved by polymerase chain reaction. Here we demonstrate that this method, which was originally described for cloning murine immunoglobulin genes from cDNA, is also applicable for rat genes. We show that the procedure also works with crude cell lysates as starting material, thereby greatly reducing the time required for sample preparation. In addition we have sequenced the nonfunctional heavy chain variable gene of the fusion partner X63Ag8.653, which was readily amplified from our hybridoma cells, and whose sequence has been so far unknown.

The multichain interleukin-2 receptor: a target for immunotherapy

Activation of resting T-lymphocytes induces synthesis of interleukin-2 (IL-2) and expression of cell surface receptors for this lymphokine. In contrast to resting normal T-cells that do not express high-affinity IL-2 receptors (IL-2R), abnormal T-cells of patients with leukemia-lymphoma, certain autoimmune disorders, and individuals rejecting allografts express this receptor. Exploiting this difference in receptor expression, antibodies to the IL-2 receptor have been used effectively to treat patients with leukemia and lymphoma. One approach is to use monoclonal antibodies produced in mice; the disadvantage is that they are highly immunogenic. In an effort to reduce the immunogenicity of the mouse monoclonal antibodies, monoclonal-antibody-mediated therapy has been revolutionized by generating humanized antibodies produced by genetic engineering in which the molecule is human except for the antigen-combining regions, which are retained from the mouse. Further, to increase its cytotoxic effectiveness, the monoclonal antibody has been armed with toxins or radionuclides. Alternatively, IL-2 itself has been linked to a toxin to kill IL-2 receptor-bearing cells. Thus, IL-2 receptor-directed therapy provides a new method for treating certain neoplastic diseases and autoimmune disorders and for preventing allograft rejection.

Drug targeting with monoclonal antibodies. A review

Monoclonal antibodies have been widely used in attempts to target anti-neoplastic agents selectively to tumours. Problems associated with the use of monoclonal antibodies as the targeting moiety include lack of complete tumour selectivity, antigenic heterogeneity, tumour access and immunogenicity. Considerable effort in the targeting field is being expended in an attempt to reduce or overcome these problems. Attachment of monoclonal antibodies to low molecular weight cytotoxic drugs, protein toxins, radionuclides or enzymes capable of conversion of inactive prodrugs to cytotoxic drugs, has, despite these problems, resulted in conjugates which do have selective anti-tumour effects in animal models. The advantages and limitations of these different approaches are reviewed. It remains to be established in man if any of these approaches will result in significant therapeutic benefit in major solid tumours.

A chimeric mouse/human anti-IL-2 receptor antibody with enhanced biological activities

A chimeric mouse/human MAb against the human p55 IL-2R was constructed from Ig genes isolated from a mouse hybridoma cell line, designated AHT107. AHT107 binds to a different epitope on p55 than IL-2, and similar to observations made for other rodent anti-IL-2R antibodies that do not recognize the same or spatially related epitope as IL-2, murine AHT107 did not efficiently inhibit proliferation of T-lymphocytes in mitogen and MLR PBMC stimulation assays. In contrast, the chimeric AHT107 antibodies containing a human IgG-1 constant region had substantially more anti-proliferative activity than their murine IgG-I counterparts. Our results indicated that the human constant region of the chimeric antibodies interacted more efficiently than the murine constant region with effector components present in the PBMC cultures. This conclusion was supported by our observation that F(ab')2 generated from the chimeric antibodies did not efficiently inhibit proliferation in the PBMC assays, and the chimeric antibodies did not inhibit proliferation of an antigen specific, IL-2 dependent human T-cell clone stimulated in the absence of PBMC.

Immunorecognition of ganglioside epitopes: correlation between affinity and cytotoxicity of ganglioside antibodies

Cell-surface gangliosides have immunomodulatory effects that are presumed to play a role in tumour growth, progression, metastasis and therapy. To study the epitopes of gangliosides on human malignant melanomas and to search for monoclonal antibodies (Mabs) with superior immunological effector functions, 19 ganglioside antibodies were established. Specificity and affinity of nine antibodies of IgG3 isotype were evaluated by enzyme linked immunosorbent assay and thin layer chromatography with a panel of purified gangliosides. All antibodies recognised the ganglioside GD3, but their epitope specificity divided them into five groups. Their affinity constants for ganglioside GD3 ranged from 4.7 x 10(6) to 2.3 x 10(8), with 2 x 10(7) for Mab R-24. Two antibodies possessed a higher affinity for GD2 than for GD3. The functional properties of the antibodies were investigated in vitro. Differences in the degree of tumour lysis by complement fixation correlated with the affinity constants. Every ganglioside antibody differed in epitope recognition, affinity and cytotoxicity. Therefore some of these antibodies might even be more useful in the immunotherapy of malignant melanoma than Mab R-24.

Protein engineering of antibodies

This article reviews the technical advances in antibody engineering and the clinical applications of these molecules. Recombinant DNA technology facilitates the construction and expression of engineered antibodies. These novel molecules are designed to meet specific applications. Although genomic and cDNA cloning have been used widely in the past to isolate the relevant antibody V domains, at present, the PCR-based cloning is the preferred system. Bacterial and mammalian expression systems are used commonly for the production of antibodies, antibody fragments, and antibody fusion proteins. A range of chimeric antibodies with murine V domains joined to C regions from human and other species have been produced and found to exhibit the expected binding characteristics and effector functions. Humanized antibodies have been developed to minimize the HAMA response, and bifunctional immunoglobulins are being used in tumor therapy and diagnosis. Single chain antibodies and fusion proteins with antibody specificities jointed to nonimmunoglobulin sequences provide a source of antibody-like molecules with novel properties. The potential applications of minimal recognition units and antigenized antibodies are described. Combinatorial libraries produced in bacteriophage present an alternative to hybridomas for the production of antibodies with the desired antigen binding specificities. Future developments in this field are discussed also.

Humanized monoclonal antibody CAMPATH-1H: myeloma cell expression of genomic constructs, nucleotide sequence of cDNA constructs and comparison of effector mechanisms of myeloma and Chinese hamster ovary cell-derived material

Expression of CAMPATH-1H, a humanized MoAb directed against an abundant surface antigen on human lymphocytes, has been studied using transfected myeloma cells. As the site of chromosome integration of DNA transfected into a cell is random we investigated the feasibility and frequency of hitting a 'jackpot' site for expression after co-transfection with CAMPATH-1H heavy and light chain constructs in genomic context. A cell line generating 40 micrograms/ml of CAMPATH-1H in spent culture supernatant was achieved. The full nucleotide sequence of the CAMPATH-1H heavy and light chain cDNA clones is also shown, in addition a comparison of the effector mechanisms, antibody dependent cellular cytotoxicity and complement dependent cytotoxicity, of myeloma cell and Chinese hamster ovary (CHO) cell-derived CAMPATH-1H is reported.

Preparation and characterization of a chimeric CD19 monoclonal antibody

FMC63 is an IgG2a mouse monoclonal antibody belonging to the CD19 cluster. CD19 antibodies react with a 95kDa protein expressed by cells of the B lymphocyte lineage, from pre-B cells to mature B lymphocytes. CD19 antibodies have been suggested as candidates for immunological attack on leukaemic and lymphoma cells of the B lineage because the antigen is restricted to the B lineage. With the potential use of FMC63 in immunotherapy in mind, we have produced a mouse-human chimera in which the genes coding for the VDJ region of the heavy chain and the VJ region of the light chain derive from the FMC63 mouse hybridoma, while the C region genes code for human IgG1. The genes have been transfected back into a mouse myeloma line, which secretes low levels of immunoglobulin. (Ig). This Ig was purified and biotinylated in order to determine the specificity of the antibody. The chimeric antibody has a reaction profile concordant with the original FMC63 antibody, but has the properties of a human IgG1, including the ability to fix human complement. However, the antibody is not cytotoxic in vitro in the presence of complement or cells capable of mediating antibody-dependent cellular cytotoxicity. Possible reasons for this and ways of using the antibody are discussed.

A prospective randomised trial of cyclosporin and methotrexate versus cyclosporin, methotrexate and prednisolone for prevention of graft-versus-host disease after HLA-identical sibling marrow transplantation for haematological malignancy

A prospective randomised trial was performed in patients given HLA-identical sibling bone marrow transplants for haematological malignancy comparing the combination of cyclosporin and methotrexate (CM) (n = 20) with the combination of cyclosporin, methotrexate and prednisolone (CMP) (n = 21) as prophylaxis for graft-versus-host disease (GVHD). There was no significant differences between the two arms for the incidence of acute GVHD grades I-IV, acute GVHD grades II-IV, chronic GVHD, interstitial pneumonitis, relapse, survival and disease-free survival. The actuarial incidence of acute GVHD grades II-IV in the CMP group was 10% and in the CM group 15% (ns). The incidence of leukaemic relapse in good risk patients was 42% in the CMP group and 40% in the CM group (ns), although the majority of these relapses were cytogenetic relapses only in patients with chronic myeloid leukaemia. The incidence of acute GVHD grades II-IV in both arms of the current trial was significantly lower than in our previous trial comparing cyclosporin and methotrexate as single agents. Leukaemic relapse is now the principal cause of treatment failure in this patient population. We conclude that prednisolone should not be included as part of the prophylactic GVHD regime and that further improvement in therapeutic outcome is dependent upon better control of the underlying malignancy.

A humanized monovalent CD3 antibody which can activate homologous complement

The rat monoclonal antibody (mAb) YTH12.5, specific for the CD3 antigen complex on human T cells has been modified in order to improve its efficacy in human therapy. With the aim of rendering it less immunogenic, it has been humanized using the method of framework grafting. During this process sequence analysis of the YTH12.5 VL gene indicated that it was of the lambda subclass, however, it was markedly dissimilar from previously published rat and mouse V lambda gene sequences and may represent a new V lambda gene family. The humanization of this light chain represents the first successful reshaping of a lambda light chain V region. To improve the effector function of the antibody we have created a monovalent form (1 Fab, 1 Fc) using a novel method involving the introduction of an N-terminally truncated human IgG1 heavy chain gene into cells producing the humanized CD3 mAb. Comparison of the mono- and bivalent humanized mAb in a complement-mediated cell lysis assay revealed that the monovalent antibody mediated lysis of human T cell blasts whereas the bivalent form did not. The availability of a humanized, complement-fixing CD3 mAb may improve opportunities for human therapy, in the management of organ rejection, autoimmunity and the treatment of T cell lymphoma.

Lymphokine receptor-directed therapy: a model for immune intervention in leukemia, autoimmunity, and immunodeficiency

Activation of resting T cells induces the synthesis of interleukin-2 (IL-2) and expression of its high-affinity receptor that involves both a 55-kDa IL-2 binding peptide identified by the anti-Tac monoclonal antibody and a 75-kDa IL-2 binding peptide associated in a receptor complex. The IL-2 receptor is proving to be an extraordinarily important therapeutic target since it is expressed by the abnormal T cells in patients with certain lymphoid malignancies or autoimmune disorders and in individuals rejecting allografts whereas it is not expressed by normal resting cells. IL-2 receptor directed monoclonal antibodies, genetically engineered humanized antibodies, and antibodies armed with toxins or radionuclides represent novel therapeutic agents for these clinical conditions.

Current applications of monoclonal antibodies for the therapy of hematopoietic cancers

Recent trials of monoclonal antibodies in patients with leukemias or lymphomas have demonstrated the remarkable potency of these agents to kill tumor cells specifically and safely. New molecular biological and radiochemical techniques are also allowing rapid inroads into the remaining obstacles to this mode of therapy.

Imaging and therapy with monoclonal antibodies in non-hematopoietic tumors

Although radiolabelled monoclonal antibodies are useful in tumor imaging, in our opinion their most important role is in the evaluation of the capacity of newly developed monoclonal antibodies to localize in tumors specifically. Intravenous injections of monoclonal antibody fragments, labelled with beta-emitting radionuclides, can completely eradicate large human colon carcinoma xenografts in nude mice whereas this is not achieved by unconjugated monoclonal antibodies. New strategies are being developed to make radioimmunotherapy applicable to carcinoma patients.

Reshaping a human monoclonal antibody to inhibit human respiratory syncytial virus infection in vivo

We transferred the complementarity determining regions from a murine monoclonal antibody that neutralizes infection by respiratory syncytial virus (RSV) to a human IgG1 monoclonal antibody. The resulting reshaped human antibody lost affinity for RSV, but an additional alteration to one of the framework regions restored binding affinity and specificity. This second generation reshaped human monoclonal antibody cross-reacted with all clinical isolates of RSV tested and both prevented disease and cured mice even when administered four days after infection. We expect the antibody will prove useful in the management of this major childhood disease.

Chemotherapy and immunotherapy of colorectal cancer

More than 50% of the patients with large bowel cancer develop disseminated disease and invariably succumb. Adjuvant chemotherapy with 5-FU and levamisole have been shown to be more efficient than 5-FU alone or in combination with cytostatics. The combination of 5-FU, leukovorin and methotrexate induces prolonged survival with a good quality of life in metastatic colorectal cancer (CRC). During the last decade tumor immunotherapy has been an alternative facilitated by isolation and large scale production of cytokines and monoclonal antibodies. The mouse monoclonal antibody (MAb) 17-1A recognizes a tumor-associated antigen (TAA), present in high concentrations on the surface of gastrointestinal tumor cells. Injections of MAb 17-1A in patients with metastatic CRC induced generation of anti-idiotypic (ab2) in 90% and anti-anti-idiotypic (ab3) antibodies in 47% of the treated patients. The development of ab3 correlated significantly with survival (mean 80 weeks) while ab3- patients survive only 38 weeks. One of 52 patients treated with MAb 17-1A is a complete remission after 66 months, 3 had minor regression and 6 had a stable disease (19% RR). Based on in vitro findings showing increased antibody-dependent cellular cytotoxicity (ADCC) by the combination of granulocyte-macrophage colony stimulating factor (GM-CSF) and MAb 17-1A, 16 CRC patients have been treated with subcutaneously injections of GM-CSF for 10 days and intravenous infusions of MAb 17-1A at day 3. Two of 16 are in CR, 1 in MR and 3 in SD (37.5% RR). Minor side-effects were registered. A further development of immunotherapy of CRC might imply vaccination by injection of specific human anti-idiotypic antibodies (ab2) which mimics the nominal antigen, in order to induce a specific immunity.

Characterization of the CAMPATH-1 (CDw52) antigen: biochemical analysis and cDNA cloning reveal an unusually small peptide backbone

The CAMPATH-1 (CDw52) antigen has been purified from human spleen. The antigenic epitope is heat stable but sensitive to mild alkali treatment. Experiments with phosphatidylinositol-specific phospholipase C indicate that it is anchored by a glycosylphosphatidylinositol (GPI) anchor. An N-terminal sequence of 11 amino acids was determined, followed by an abrupt stop. Using short overlapping mixed oligonucleotide primers, cDNA synthesized from the mRNA of a human B cell line was amplified by the polymerase chain reaction. The product was used to isolate cDNA clones and the full amino acid sequence of the CAMPATH-1 antigen was deduced. It consists of 37 amino acid residues plus a 24-residue signal peptide. It has all the features expected for a GPI-anchored membrane protein except that the predicted mature protein is remarkably short, comprising no more than 18 residues and possibly as few as 12 (depending on the GPI linkage site). Potential attachment sites for carbohydrate are present and it is shown that the antigen contains N-linked oligosaccharide(s). This structure accounts for the known properties of the antigen, though the exact reasons why it is such a good target for cell lysis in vitro and in vivo are not yet clear.

Monoclonal antibody therapy for the induction of transplantation tolerance

There are three ways in which monoclonal antibodies could be used to facilitate the induction of tolerance to foreign tissues after organ transplantation. First, depleting monoclonal antibodies could be directed against the T cells responsible, thereby reducing their number and acting to non-specifically immunosuppress the patient. This is generally not sufficient to allow tolerance induction in the T cells which repopulate the periphery. Second, depleting monoclonal antibodies could be used to remove donor passenger leukocytes and antigen-presenting cells from the donor organ, which may both reduce immunogenicity and increase the chance of tolerance induction. Third, non-depleting, but functionally blocking, monoclonal antibodies to T cell molecules such as CD4 and CD8 can allow the specific induction of transplantation tolerance in mouse models, an approach which might be applicable to man, not only for organ transplantation, but also in the treatment of autoimmune diseases. These three approaches are, in time, likely to complement each other in clinical practice. Monoclonal antibodies can be tailored to each approach by choosing appropriate specificities and isotypes, and further refinements can be made where necessary by making monovalent or humanised antibodies. The application of each of these approaches to clinical therapy is described.

Monoclonal antibodies in diagnosis and therapy

Monoclonal antibodies have been applied clinically to the diagnosis and therapy of an array of human disorders, including cancer and infectious diseases, and have been used for the modulation of immune responses. Effective therapy using unmodified monoclonal antibodies has, however, been elusive. Recently, monoclonal antibody-mediated therapy has been revolutionized by advances such as the definition of cell-surface structures on abnormal cells as targets for effective monoclonal antibody action, genetic engineering to create less immunogenic and more effective monoclonal antibodies, and the arming of such antibodies with toxins or radionuclides to enhance their effector function.

Humanized antibodies for therapy

Protein engineering has made it possible to combine the binding sites of murine antibodies with human antibody regions. Antibodies constructed in this way have important advantages for therapy.

Reshaping a therapeutic CD4 antibody

An immunosuppressive rat antibody (Campath-9) against human CD4 has been reshaped for use in the management of autoimmunity and the prevention of graft rejection. Two different forms of the reshaped antibody were produced that derive their heavy chain variable region framework sequences from the human myeloma proteins KOL or NEW. When compared to a chimeric form of the CD4 antibody, the avidity of the KOL-based reshaped antibody was only slightly reduced, whereas that of the NEW-based reshaped antibody was very poor. The successful reshaping to the KOL-based framework was by a procedure involving the grafting of human framework sequences onto the cloned rodent variable region by in vitro mutagenesis.

Production of site-selected neutralizing human monoclonal antibodies against the third variable domain of the human immunodeficiency virus type 1 envelope glycoprotein

Cell lines secreting IgG1 human monoclonal antibodies (mAb) to the envelope glycoprotein, gp120, of human immunodeficiency virus (HIV) have been produced by transformation of peripheral blood cells from HIV-infected individuals and by fusion of transformed cells to a human-mouse heteromyeloma cell line (SHM-D33). Two human mAbs were site-selected by means of a 23-mer synthetic peptide spanning a portion of the third variable domain of gp120 from the MN strain of HIV. The two heterohybridomas produce three times more IgG than do their parent lymphoblastoid cell lines. The specificities of these mAbs have been mapped to sequences near the tip of the disulfide loop of the gp120 third variable domain, Lys-Arg-Ile-His-Ile and His-Ile-Gly-Pro-Gly-Arg, respectively. The mAbs have dissociation constants of 3.7 x 10(-6) M and 8.3 x 10(-7) M, neutralize HIVMN in vitro at nanogram levels, and bear the characteristics of antibodies associated with protective immunity in vivo.

Anti-Tac-H, a humanized antibody to the interleukin 2 receptor, prolongs primate cardiac allograft survival

High-affinity interleukin 2 receptors (IL-2Rs) are expressed by T cells activated in response to foreign histocompatibility antigens but not by normal resting T cells. To exploit this difference in IL-2R expression, anti-Tac-M, a murine monoclonal antibody specific for the IL-2R alpha chain, was used to inhibit organ allograft rejection. However, the use of murine anti-Tac as an immunosuppressive agent was limited by neutralization by human anti-murine antibodies and by weak recruitment of effector functions. To circumvent these difficulties, a humanized antibody to the IL-2R, anti-Tac-H, was prepared. This molecule is human with the exception of the hypervariable segments, which are retained from the mouse. In vivo survival of anti-Tac-H is 2.5-fold longer than simultaneously administered anti-Tac-M (terminal t1/2, 103 hr vs. 38 hr). In addition, anti-Tac-H is less immunogenic than anti-Tac-M when administered to cynomolgus monkeys undergoing heterotopic cardiac allografting. Specifically, all monkeys treated with anti-Tac-M developed measurable anti-anti-Tac-M levels by day 15 (mean onset, 11 days). In contrast, none of the animals receiving anti-Tac-H produced measurable antibodies to this monoclonal antibody before day 33. Finally, there was a prolongation of graft survival in the cynomolgus heterotopic cardiac allograft model in animals receiving anti-Tac. In animals that received anti-Tac-M, the allograft survival was prolonged compared to that of the control group (mean survival, 14 +/- 1.98 days compared to 9.2 +/- 0.48 days; P less than 0.025). Graft survival was further prolonged by anti-Tac-H with a mean survival of 20.0 +/- 0.55 days (compared to controls, P less than 0.001; compared to anti-Tac-M, P less than 0.02). There was no toxicity attributable to the administration of either form of anti-Tac. Thus, anti-Tac-H significantly prolonged allograft survival in primates, without toxic side effects, and may be of value as an adjunct to standard immunosuppressive therapy in humans.

Humanized antibodies for antiviral therapy

Antibody therapy holds great promise for the treatment of cancer, autoimmune disorders, and viral infections. Murine monoclonal antibodies are relatively easy to produce but are severely restricted for therapeutic use by their immunogenicity in humans. Production of human monoclonal antibodies has been problematic. Humanized antibodies can be generated by introducing the six hypervariable regions from the heavy and light chains of a murine antibody into a human framework sequence and combining it with human constant regions. We humanized, with the aid of computer modeling, two murine monoclonal antibodies against herpes simplex virus gB and gD glycoproteins. The binding, virus neutralization, and cell protection results all indicate that both humanized antibodies have retained the binding activities and the biological properties of the murine monoclonal antibodies.

Man-made antibodies

Monoclonal antibodies can now be genetically engineered and endowed with new properties. In the future, gene technology could enable antigen-binding fragments to be made by exploiting repertoires of variable domain genes derived from immunized animals and expressed in bacteria. How readily can this approach be extended to production of 'in vitro' repertoires of variable domain genes, and obviate the immunization of animals?

Initial experience with treatment of human B cell lymphoma with anti-CD19 monoclonal antibody

Six patients with progressive B cell non-Hodgkin's lymphoma have been treated with an IgG2a mouse monoclonal antibody (mAb) against the B cell differentiation antigen CD19, with total doses varying from 225 mg to 1000 mg. Free mAb was detected in the serum after doses of 15-30 mg. After the mAb infusions the number of circulating tumour cells was temporarily reduced, but in some cases antibody-coated cells remained in the circulation for several days. mAb penetrated to extravascular tumour sites; in general higher doses were required to saturate cells in the lymph nodes than to sensitize tumour cells in the bone marrow. mAb doses of up to 250 mg were given i.v. over 4 h without major toxicity. One patient twice achieved a partial remission after two periods of mAb treatment with an 8-month interval; the second remission lasted for 9 months. One patient showed a minor response. None of the patients made antibodies against the mouse immunoglobulin. Serum immunoglobulin levels were followed as a measure of the function of the normal B cell compartment; no significant changes were seen up to 6 months after mAb treatment.

New therapeutic modalities for cancer

A review is given on new biological approaches to cancer therapy based on knowledge concerning interferons, interleukins. LAK-cells, tumour-infiltrating lymphocytes, tumour necrosis factor, colony-stimulating factors, monoclonal antibodies and oncogenes. There are many potential permutations for the application of biological therapy for cancer. One of the most important developments has been the increased understanding of the molecular mechanisms of malignancy through which biological manipulation can be tailored to an individual tumour. Although current clinical studies are not demonstrating high response rates they may well be analogous to the advances seen with chemotherapy in its early days. As yet only relatively small numbers of patients have had access to, or been suitable for, treatment. With further refinements in production, administration, and an increase in the specificity of treatment, the possibility of curing metastatic solid tumours may become a reality.

Construction and characterization of a functional chimeric murine-human antibody directed against human fibrin fragment-D dimer

Fibrin-directed monoclonal antibodies may be clinically useful for in vitro thrombus imaging and for the targeting of fibrinolytic agents to blood clots. One such murine monoclonal antibody, (mAb-15C5), raised against the fragment-D dimer epitope of cross-linked human fibrin, was previously characterized [Holvoet, P., Stassen, J. M., Hashimoto, Y., Spriggs, D., Devos, P. & Collen, D. (1989) Thromb. Haemostasis 61, 307-313] has recently been cloned and expressed [Vandamme, A.-M., Bulens, F., Bernar, H., Nelles, L., Lijnen, H. R. & Collen, D. (1990) Eur. J. Biochem. 192, 767-775]. In order to reduce the immunogenicity of the murine mAb-15C5 in man, we have now constructed a murine--human chimera of mAb-15C5, by substituting the cDNA sequences encoding the constant regions of the murine kappa light chain and gamma 1 heavy chain by the corresponding human genomic sequences. Both chimeric murine--human Ig chains were cloned into two separately selectable expression vectors, which were contransfected into Chinese hamster ovary (CHO) cells. Murine--human chimeric mAb-15C5 (mAb-15C5Hu) was purified from the conditioned medium of selected cell lines by chromatography on Zn-chelating Sepharose, protein-A-Sepharose and on insolubilized antigen (fragment-D dimer), with a final yield of 29 micrograms/l and a recovery of 33%. SDS/PAGE without reduction revealed a homogeneous band with a mobility similar to that of natural mAb-15C5, whereas after reduction, both the heavy and the light chains had slightly slower mobilities than their natural counterparts. Expression in the presence of tunicamycin suggested that the differences in gamma 1-chain mobility were due to different N-glycosylation patterns. Immunoblotting of proteins from SDS gels showed immunological reactivity of recombinant mAb-15C5Hu with goat anti-(human IgG) IgG and of recombinant and natural murine mAb-15C5 with goat anti-(mouse IgG) IgG. Competitive binding revealed a comparable affinity of recombinant murine mAb-15C5, recombinant mAb-15C5Hu and natural mAb-15C5, for fragment-D dimer, indicating that recombinant mAb-15C5Hu was obtained in a functionally intact form. Thus, mAb-15C5Hu may constitute a useful alternative to mAb-15C5 for in vivo use in man.

Overview of monoclonal antibodies in the diagnosis and therapy of cancer

Monoclonal antibodies initially offered the promise of a cure for cancer as "magic bullets" but this hope was quickly diminished as the complexities of the host-tumor relationship were realized. We have acquired a tremendous amount of practical experience since the first cancer patient was treated with a MAb nearly 10 years ago. This experience, combined with recent advances in recombinant DNA technology, has endowed us with a rich variety of opportunities to exploit in the diagnosis and treatment of malignancies. If recent preclinical research studies are clinically applicable and the antitumor responses seen in initial clinical trials can be optimized and confirmed, the next decade will likely be host to remarkable advances in the diagnosis and treatment of cancer with MAbs.

High Level Expression of the Humanized Monoclonal Antibody CAMPATH-1H in Chinese Hamster Ovary Cells

We have cloned the light and heavy chain cDNAs for the humanized monoclonal antibody Campath-1H and expressed them in Chinese hamster ovary (CHO) cells using a dihydrofolate reductase (dhfr) amplification procedure. Each cDNA was positioned under control of the strong human beta-actin promoter/polyadenylation signals and used to evaluate alternative vector design and amplification procedures. By employing a dual selection co-transfection strategy, initial transformants accumulated antibody levels of 0.5 micrograms/ml after 4 days continuous culture. When subjected to successive rounds of selection in medium containing stepwise increments in methotrexate (MTX), stable cell lines were obtained that secreted up to 200 micrograms/ml of Campath-1H during the same period. This reflects a productivity of 100 micrograms/10(6) cells/day and demonstrates the potential of engineering CHO cells for the production of recombinant antibodies.

New approaches for antirheumatic therapy

New approaches for antirheumatic therapy are firmly based on current knowledge of immunopathogenic processes. Specific immunotherapy is directed at the treatment of the disease per se and not the production of generalized immunosuppression with its unwanted side-effects. The three targets against which specific immunotherapy is directed are the T cell receptor, the HLA antigen linked to the disease and the antigenic peptide involved in the initiation and/or persistence of the disease. Therapies directed against lymphokines, monokines and cytokines produced during the chronic immune-mediated inflammation are also being developed but they may be unsuccessful not only because of the great redundancy inbuilt into the inflammatory response but also because they would produce too general a response with possibilities of harmful side-effects. Specific immunotherapy at present is largely through the use of monoclonal antibodies directed against a variety of T cell membrane antigens such as CD4, CD7 and the interleukin 2 receptor. A possible therapy is monoclonal antibodies, directed against the HLA molecule involved in the aetiopathogenesis of disease. The use of disease-causing T cell lines or clones as vaccines or therapeutic agents has solid experimental support and studies are in progress in patients with rheumatoid arthritis using T cell lines grown from synovial fluid aspirates. If successful, such therapy could be modified to the use of short peptide fragments from the relevant T cell receptor. T cells recognize antigenic peptides presented on the surface of antigen-presenting cells within a groove formed by the HLA molecule. Displacement of disease-inducing antigenic peptides by engineered 'neutral' peptides could offer a very precise form of immunotherapy. Many of these approaches are based on the hypothesis that transient but effective switching-off of the disease process may allow immunoregulatory circuits, as yet poorly defined, to come into play to permanently cure the disease. Many such therapies are in the offing. It may be that they have to be used in various combinations in order to achieve cure. For this complex and time-consuming task to attain that desired consummation, co-operative interaction between many clinicians, basic scientists and patients will be required. It is to that cooperation that we dedicate this chapter on new approaches for antirheumatic therapy.

Immunoglobulin V regions of a bactericidal anti-Neisseria meningitidis outer membrane protein monoclonal antibody

C6 is a potentially therapeutic murine monoclonal antibody that recognizes the class 1 outer membrane protein of Neisseria meningitidis. C6 specifically immunoblots this antigen and augments in vitro killing of N. meningitidis bacteria. We describe a general method of obtaining the heavy and light chain variable-region sequence from immunoglobulin-secreting cells. The method uses mixed polymerase chain reaction (PCR) primers designed from the 5' end of the framework 1 (FR1) sequences of the heavy and light chains, and 3'-end primers for constant-region conserved sequences. The method has been applied to the cloning and sequencing of the variable region of C6 to construct a humanized monoclonal antibody. Rapid amplification and sequencing of variable regions by this general method have multiple applications in the study of the immune response to infectious diseases.

Monoclonal antibodies specific for human IgE-producing B cells: a potential therapeutic for IgE-mediated allergic diseases

Monoclonal antibodies (MAbs) specific for surface antigens of lymphocytes are being used to target and deplete tumorous or normal lymphocytes in vivo. Here, we report evidence for the existence of antigenic epitopes on IgE that are accessible on IgE-secreting B cells but not on other cells bearing IgE. Among 42 murine MAbs specific for human IgE, two were shown by fluorescence flow cytometric analyses to bind to IgE-secreting cell lines but not to IgE bound to high-affinity IgE.Fc receptors (Fc epsilon RI) on basophils or low-affinity IgE receptors (Fc epsilon RII) on other cell types. Neither could they induce histamine release from basophils of various donors even under very permissive conditions. These antibodies may be useful for targeting IgE-secreting B cells in patients suffering from IgE-mediated allergies.

A novel human leucocyte surface membrane antigen defined by murine monoclonal antibody

A murine monoclonal antibody has been produced which identifies a novel human leucocyte differentiation antigen. The antibody, designated WM-66, of IgM subclass, was cytolytic with human complement. WM-66 was shown to react with virtually all normal T and B lymphocytes from peripheral blood and lymphoid tissues, as well as blood monocytes and approximately 40% of bone marrow mononuclear cells. The antibody also bound to the majority of cases of chronic B-cell malignancies, including chronic lymphatic leukaemia and non-Hodgkin's lymphoma, but not to cases of acute leukaemia or to the majority of leukaemic and lymphoblastoid cell lines. WM-66 also reacted with epithelium of bronchus and salivary gland ducts. A single band of relative molecular mass 65,000 Daltons was immunoprecipitated from membrane extracts of normal lymphocytes and the B-cell line Daudi. Treatment of a number of WM-66-negative B-cell lines with neuraminidase resulted in WM-66 binding, indicating that the antigen exists in a covert form masked by sialic acid residues on a wider spectrum of cell types than was initially apparent. The reactivity pattern of WM-66 indicates that it recognises a previously undescribed surface membrane molecule with broad non-lineage-specific distribution on leucocytes. This has recently been confirmed at the Fourth International Workshop on Human Leucocyte Differentiation Antigens. Although the biological function of the molecule recognised by WM-66 is unknown, the lytic properties of the antibody suggest a possible in vivo therapeutic role as an immunosuppressant or for treatment of lymphoid malignancy.

Systemic radiotherapy--the new frontier

The present day use of systemically administered isotopes and conjugated isotopic combinations are reviewed. Administration of 131Iodine in thyroid cancer led to a 97% local control and 50% complete remission of pulmonary metastases. Specificity directed isotopic therapy (metabolic, hormonal, and antibody) is discussed and includes factors such as tumor physiology and isotopic linkage. The clinical results and new knowledge being gained in Hodgkin's disease, non-Hodgkin's, colorectal, hepatoma, intrahepatic biliary and gliomatous cancers are reviewed. The dose response relationship to tumor remission is demonstrated in Hodgkin's treated with 131I antiferritin (40% partial remission) and more recently 90Yttrium antiferritin (50% complete response). Varied routes of administration, the problem of anti-antibody and bone marrow transplantation are discussed. Finally, the challenge to radiobiologists, physicists, chemists, immunologists, nuclear radiologists, and radiation oncologists is emphasized by definition of the new laboratory and clinical approaches being developed in systemic radiation therapy.

A simple method for measuring patient anti-globulin responses against isotypic or idiotypic determinants

A simple inhibition of capture enzyme-linked immunosorbent assay (IOC-ELISA) was developed which permitted the independent measurement of anti-idiotypic and anti-isotypic antiglobulins in serum samples from patients receiving therapeutic monoclonal antibodies.

A phase II trial of murine monoclonal antibody 17-1A and interferon-gamma: clinical and immunological data

A group of 15 patients with metastatic colorectal adenocarcinoma received a combination of interferon gamma (0.1 mg/m2, days 1-15) and the murine monoclonal antibody 17-1A (400 mg, days 5, 7, 9 and 12). The treatment was tolerated with minimal toxicity. Of the 14 evaluable patients, 13 developed human antibody to murine 17-1A, with 11 patients demonstrating antibody to the variable region of 17-1A (anti-idiotype). Antibody to the variable region was inhibited by 17-1A but not by mouse immunoglobulin. Sera from patients with substantial anti-idiotype reactivity were capable of inhibiting the binding of murine 17-1A to antigen expressing LS174-T cells thus indicating the presence of antibody directed against the 17-1A combining site (mirror-image anti-idiotype). The median survival of the whole group was 56 weeks and there was no correlation between clinical response/survival and the development of anti-idiotype antibody.