Human ovarian carcinoma lysis by cytotoxic T cells targeted by bispecific monoclonal antibodies: analysis of the antibody components

Development of Bispecific Antibody for Cancer Immunotherapy: Focus on T Cell Engaging Antibody

In the era of immunotherapeutic control of cancers, many advances in biotechnology, especially in Ab engineering, have provided multiple new candidates as therapeutic immuno-oncology modalities. Bispecific Abs (BsAbs) that recognize 2 different antigens in one molecule are promising drug candidates and have inspired an upsurge in research in both academia and the pharmaceutical industry. Among several BsAbs, T cell engaging BsAb (TCEB), a new class of therapeutic agents designed to simultaneously bind to T cells and tumor cells via tumor cell specific antigens in immunotherapy, is the most promising BsAb. Herein, we are providing an overview of the current status of the development of TCEBs. The diverse formats and characteristics of TCEBs, in addition to the functional mechanisms of BsAbs are discussed. Several aspects of a new TCEB-Blinatumomab-are reviewed, including the current clinical data, challenges of patient treatment, drawbacks regarding toxicities, and resistance of TCEB therapy. Development of the next generation of TCEBs is also discussed in addition to the comparison of TCEB with current chimeric antigen receptor-T therapy.

Greatest Hits-Innovative Technologies for High Throughput Identification of Bispecific Antibodies

Recent years have shown a tremendous increase and diversification in antibody-based therapeutics with advances in production techniques and formats. The plethora of currently investigated bi- to multi-specific antibody architectures can be harnessed to elicit a broad variety of specific modes of actions in oncology and immunology, spanning from enhanced selectivity to effector cell recruitment, all of which cannot be addressed by monospecific antibodies. Despite continuously growing efforts and methodologies, the identification of an optimal bispecific antibody as the best possible combination of two parental monospecific binders, however, remains challenging, due to tedious cloning and production, often resulting in undesired extended development times and increased expenses. Although automated high throughput screening approaches have matured for pharmaceutical small molecule development, it was only recently that protein bioconjugation technologies have been developed for the facile generation of bispecific antibodies in a 'plug and play' manner. In this review, we provide an overview of the most relevant methodologies for bispecific screening purposes-the DuoBody concept, paired light chain single cell production approaches, Sortase A and Transglutaminase, the SpyTag/SpyCatcher system, and inteins-and elaborate on the benefits as well as drawbacks of the different technologies.

Hybrid Antibodies in Cancer Diagnosis and Therapy

Monoclonal Antibodies (Mabs) represent a promising tool for cancer diagnosis and theraphy.

Administration of MAbs alone or conjugated to cytotoxic agents has been attempted but has significant limitations. Another potentially effective approach is the use of bispecific or bifunctional antibodies where the capacity to recognize the tumor cell and the toxic agent or lymphocyte activation molecule are united in one MAb. The hybrid molecule can be produced by chemical linkage between the two parentalantibodies, or alternatively by a biological approach that consists in the fusion of the two selected hybridomas. In the resulting quadroma cell the hybridoma immunoglobulin chains recombine randomly to form the bifunctional MAb.

In different in vitro and in vivo models, bifunctional MAbs against tumor and CDS at nanomolar concentration has been shown to promote tumor cell killing by cytotoxic T cells.

Specific localization of chemotherapeutic drugs in xenografted tumors has been demonstrated in mice pretreated with hybrid MAbs.

The advantages of the hybrid MAb approach are that it should reduce the MAb biodistribution problem and that it involves no chemical manipulation between the functional agent and the MAb molecules.

Purified anti-CD3 × anti-HER2 bispecific antibody potentiates cytokine-induced killer cells of poor spontaneous cytotoxicity against breast cancer cells

Background

Chemical crosslinking is the most straightforward method to produce bispecific antibodies (BsAb) for arming ex vivo activated cytotoxic T lymphocytes. However, heterogeneous polymers are produced by chemical crosslinking. Currently, it is not known under what circumstances or to what extent further purification is needed.

Results

In this study, we purified Traut’s Reagent-Sulfo-SMCC crosslinked anti-CD3 × anti-HER2 by size-exclusion column chromatography and compared the capacity of the crude and the purified forms of the BsAb in enhancing cytokine-induced killer (CIK) cell-mediated cytotoxicity in vitro. We found that the purified BsAb assisted CIK cells more efficiently than the crude form only when the spontaneous cytotoxicity of the CIK cells was relatively low; otherwise, the two forms performed almost identically.

Conclusions

For the CIK cells of low spontaneous cytotoxicity, purified BsAb is a more powerful substitute for crude BsAb in enhancing their killing efficacy. However, that purification of BsAb is not necessary for robust CIK cells. This phenomenon also corroborates that CIK-mediated cytotoxicity is highly dependent on cell contact.

Electronic supplementary material

The online version of this article (doi:10.1186/2045-3701-4-70) contains supplementary material, which is available to authorized users.

Bispecific antibodies engage T cells for antitumor immunotherapy

INTRODUCTION

Although considerable evidence supports the hypothesis that T cells play a critical role in the immune response against cancer, the ability to mount and sustain tumor-specific cellular responses in vivo remains a challenge. A strategy that harnesses the cytotoxic advantage of T cell therapy is the use of bispecific antibodies designed to engage and activate endogenous polyclonal T cell populations via the CD3 complex, but only in the presence of a tumor antigen. While antibody constructs with dual specificity were first described as anticancer therapeutics over 25 years ago, it was not until recently that one subclass of bispecific single-chain antibody, the bispecific T cell engager (BiTE), emerged as superior to previous iterations in achieving efficacy in animal models and early clinical trials.

AREAS COVERED

The evolution of bispecific antibodies in antitumor immunotherapy is reviewed and the greatest hurdles impeding their clinical translation are discussed, specifically in the context of immunoprivileged sites as is the case for intracerebral malignancy.

EXPERT OPINION

The BiTE platform has great potential in the treatment of malignant disease. Despite burgeoning interest in bispecific antibodies and permutations thereof, the issues of stability and cost-effective production persist as obstacles.

Locoregional immunotherapy in cancer patients: review of clinical studies

Many patients with invasive cancer have a compromised immune system. This immune dysfunction does appear to start at the site of the tumor. Locoregional immunotherapy is given to stimulate the immune system in order to kill tumor cells either indirectly via a specific or a non-specific way or directly via cell transfer therapy. Advantages to give this immunotherapy locoregionally in stead of systemically are a higher concentration of the immunomodulator at the site of the tumor, to attract or activate effector cells, and diminished toxicity. In this review we have summarised the clinical studies using loco-regional immunotherapy in patients with cancer. Only phase I and II studies were performed. Clinical responses were seen. No single locoregional treatment has become a standard therapy. Relatively few investigations were performed to estimate the influence on the locally effector mechanisms or immune dysfunction. In future clinical trials it is essential to get a better insight in these mechanisms.

Diagnosis of persistent ovarian carcinoma with three-step immunoscintigraphy

The diagnosis of recurrent ovarian carcinoma is usually determined at surgical re-exploration since the main non-invasive diagnostic tests have low accuracy. It would be desirable to have a high accuracy non-invasive diagnostic procedure. With this aim, we have assessed the utility of three-step immunoscintigraphy. Thirty patients were intravenously injected with biotinylated monoclonal antibodies MOv18 and B72.3, followed by avidin-streptavidin injection and finally by 111In-biotin. Tumour recurrences were imaged 2 h post radioactivity injection. All patients underwent surgical re-exploration 3-4 days after immunoscintigraphy; the presence of tumour in the area of immunoscintigraphic uptake was evaluated in the biopsied material. Twenty-one patients studied were true-positive, five were true-negative, four were false-positive and none was false-negative. The diagnostic accuracy, positive predictive value and negative predictive value were 87%, 84% and 100% respectively. If these findings are confirmed in a larger number of patients, we expect immunoscintigraphy to be introduced as a cost-effective procedure in the follow-up of patients who have received surgery for ovarian carcinoma, since it promises to reliably identify patients who do not require surgical re-exploration, and guide biopsies when they are indicated.

Comparison of IgE and IgG antibody-dependent cytotoxicity in vitro and in a SCID mouse xenograft model of ovarian carcinoma

Allergic reactions are mediated by IgE antibodies bound to high-affinity receptors on mast cells in peripheral tissues and are characterized by their immediacy and hypersensitivity. These properties could also be advantageous in immunotherapy against cancer growth in peripheral tissues. We have constructed chimeric IgE and IgG1 antibodies with murine V regions and human C regions corresponding to the MOv18 monoclonal antibody against the human ovarian tumor-associated antigen, folate binding protein. The antibodies exhibited the expected binding affinities for antigen and Fc receptors, and effector activities with human basophils and platelets in vitro. The protective activities of MOv18-IgE and MOv18-IgG1 were compared in a SCID mouse xenograft model of ovarian carcinoma. The beneficial effects of MOv18-IgE were greater and of longer duration than those of MOv18-IgG1. Our results suggest that the allergic reaction could be harnessed for the suppression of ovarian tumors.

Bispecific antibodies for treatment of cancer in experimental animal models and man

Immunotherapy is a powerful anti-cancer treatment modality. However, despite numerous encouraging results obtained in pre-clinical studies, a definite breakthrough towards an established clinical treatment modality has as yet not occurred. Antibodies against tumor antigens have been shown to localise at the site of the tumor, but inadequate triggering of immune effector mechanisms have thwarted clinical efficacy thus far. Cellular immunotherapy has been hampered by limitations such as lack of specificity, down-regulation of major histocompatibility complex (MHC)-expression or Fas ligand up-regulation on tumor cells. This review focuses on the use of bispecific antibodies (BsAbs) for immunotherapy of cancer. Using BsAbs, it is possible to take advantage of the highly specific binding characteristics of antibodies and combine these with the powerful effector functions of cytotoxic immune effector cells. BsAbs share two different, monoclonal antibody-derived, antigen-recognizing moieties within one molecule. By dual binding, BsAbs reactive with a trigger molecule on an immune effector cell on the one hand and a surface antigen on a tumor target cell on the other are thus able to functionally focus the lytic activity of the immune effector cell towards the target cell. Over the last few years, the concept of BsAb-mediated tumor cell killing has been studied extensively both in preclinical models and in a number of phase I clinical trials. Promising pre-clinical results have been reported using tumor models in which diverse immune effector cell populations have been used. Despite this pre-clinical in vivo efficacy, the first clinical trials indicate that we are still not in a position to successfully treat human malignancies. This review discusses the production of BsAbs, the choice of trigger molecules in combination with potential effector cells and the preclinical models that have led to the current use of BsAbs in experimental clinical trials. It has become clear that appropriate immune cell activation and establishing a favourable effector-to-target cell ratio will have direct impact on the efficacy of the therapeutic approaches using BsAbs. New directions are discussed, i.e. finding appropriate dosage schemes by which immune effector cells become redirected without inducing hyporesponsiveness, defining possibilities for combining different immune effector cell populations and creating an in situ tumor environment that allows maximal tumoricidal activity

Local but no systemic immunomodulation by intraperitoneal treatment of advanced ovarian cancer with autologous T lymphocytes re-targeted by a bi-specific monoclonal antibody

We have reported a 27% overall anti-tumor response using i.p. immunotherapy of advanced ovarian carcinoma with autologous, ex vivo expanded, T lymphocytes re-targeted with bi-specific monoclonal antibody OC/TR, combined with soluble OC/TR and low-dose recombinant interleukin-2 (IL-2). This treatment had no effect on extraperitoneal disease. Therefore we studied in 13 patients whether this immunotherapeutic protocol resulted only in local or also in systemic immunomodulation. The phenotype of the ex vivo expanded lymphocytes was mainly CD3+, 4-, 8+, 16-, 56-. Their OC/TR-re-targeted cytolytic activity against Igrov-1 ovarian-carcinoma cells was approximately as high in responders as in non-responders. Following most therapeutic cycles, the immunophenotype of lymphocytes recovered from the peritoneal fluid was similar to that of the infused T cells (i.e., mainly CD3+, 4-, 8+) and they were coated with OC/TR. However, cytolytic activity of the recovered lymphocytes against Igrov- 1 cells was low in direct assays, and only slightly increased after additional in vitro re-targeting with OC/TR. Systemically, the i.p. immunotherapy resulted in a transient lymphopenia lasting for about 7 days, low (i.e., 5 to 13 ng/ml) serum concentrations of free, functional OC/TR, and very weak coating of circulating T lymphocytes with OC/TR. These peripheral-blood T lymphocytes did not exert OC/TR-re-targeted cytolytic activity. Thus, locoregional OC/TR-re-targeted cellular immunotherapy resulted in substantial local immunomodulation and anti-tumor effects but virtually no systemic immunomodulation.

Comparison of three different methods for radiolabelling human activated T lymphocytes

One approach in the treatment of ovarian cancer patients involves the infusion of autologous T lymphocytes coupled with a bispecific monoclonal antibody MOv18/anti-CD3 (biMAb OC/TR), which recognizes a 38-kDa glycoprotein expressed on ovarian carcinomas and the CD3 T cell receptor. However, little is known about the in vivo biodistribution of injected activated lymphocytes, information that could be obtained by scintigraphic imaging of radiolabelled T cells in order to visualize the migratory pattern. We compared the efficiency, stability and toxicity of technetium-99m hexamethylpropylene amine oxime (HMPAO), indium-111 oxine and fluorine-18 2-fluoro-2-deoxy-d-glucose (FDG) in radiolabelling activated lymphocytes targeted with biMAb OC/TR. The mean labelling efficiencies of 111In-oxine and 18F-FDG using 2.5x10(8) lymphocytes (68% and 64%, respectively) were more than twice that of 99mTc-HMPAO (31%). Retention of the radionuclide in the cell was highest in the case of 111In-oxine labelling (less than 25% of the initial cell-bound activity released after 240 min, as compared with 44% of the 99mTc label in the same period and 45% of 18F radionuclide released after 150 min). None of the three radiolabelling reagents induced any significant alteration in cell viability or immunophenotype. However, both 111In-oxine and 18F-FDG induced a loss of cytotoxic activity of lymphocytes against the ovarian carcinoma cell line IGROV1, and all three radiolabelling reagents caused a significant reduction in the proliferative ability of labelled lymphocytes compared to controls, with cell death occurring after 8-9 days. Radiolabelling with the more stable 111In-oxine reagent using a higher number of lymphocytes (1.4x10(9)) but the same total activity (around 55.5 MBq) resulted in improved labelled T cell viability and proliferative ability, although the mean labelling efficiency decreased (35.8%). Together the data suggest that 111In-oxine at low activity per cell is the most appropriate reagent for radiolabelling activated retargeted T lymphocytes useful for in vivo biodistribution studies.

Generation of chimeric bispecific G250/anti-CD3 monoclonal antibody, a tool to combat renal cell carcinoma

The monoclonal antibody (MAb) G250 binds to a tumour-associated antigen, expressed in renal cell carcinoma (RCC), which has been demonstrated to be a suitable target for antibody-mediated immunotherapy. A bispecific antibody having both G250 and anti-CD3 specificity can cross-link G250 antigen-expressing RCC target cells with T cells and can mediate lysis of such targets. Therapy studies with murine antibodies are limited by immune responses to the antibodies injected (HAMA response), which can be decreased by using chimeric antibodies. We generated a chimeric bispecific G250/anti CD3 MAb by transfecting chimeric genes of heavy and light chains for both the G250 MAb and the anti-CD3 MAb into a myeloma cell line. Cytotoxicity assays revealed that the chimeric bispecific MAb was capable of mediating lysis of RCC cell lines by cloned human CD8+T cells or by IL-2-stimulated peripheral blood lymphocytes (PBLs). Lysis mediated by the MAb was specific for target cells that expressed the G250 antigen and was effective at concentrations as low as 0.01 microgram ml-1. The chimeric bispecific G250/anti-CD3 MAb produced may be an effective adjuvant to the currently used IL-2-based therapy of advanced renal cell arcinoma.

Bifunctional antibody retargeting in vivo-activated T lymphocytes: simplifying clinical application

For antitumor x anti-CD3 bifunctional antibody (BFA) therapy to be clinically relevant in solid tumors, activated lymphocytes must be present within tumors. Toward that end, three uniquely different in vivo activation approaches were investigated in a p97 human antigen expressing syngeneic murine melanoma model. beta-Glucan (200 micrograms), staphylococcal enterotoxin B (SEB) (50 micrograms), and F(ab')2 BFA (10 micrograms) were tested for their ability to activate lymphocytes, neutralize pulmonary metastases, and treat established tumors. Systemic activation, measured as the ability of splenocytes to lyse tumor cells in vitro in the presence of BFA, was enhanced by the in vivo administration of SEB but not by beta-glucan or F(ab')2 BFA. Despite lacking a systemic effect, F(ab')2 BFA increased both direct and BFA-mediated cytotoxicity in fresh tumor infiltrating lymphocytes. beta-Glucan did not increase systemic or intratumor T cell activation. However, it significantly enhanced the ability of splenocytes to lyse NK-sensitive YAC-1 cells. When tested in a pulmonary metastases model, all three forms of immune modulation combined with F(ab')2 BFA significantly reduced the number of metastases. BFA were more effective at tumor neutralization when combined with SEB compared with adoptively transferred, in vitro-activated splenocytes. These studies demonstrate that immune modulators when combined with F(ab')2 BFA can provide effective antitumor therapy. Several clinical obstacles may be overcome by the application of these reagents.

Bispecific antibody targeted T cell therapy of ovarian cancer: clinical results and future directions

The high frequency of relapse after induction chemotherapy in advanced ovarian carcinoma patients calls for new therapeutic modalities. Retargeted T cell-mediated lysis can be achieved using the bispecific antibody (BsmAb) OCTR, directed to CD3 on T cells and to the folate receptor on ovarian carcinoma cells. Twenty-eight patients with limited intraperitoneal disease after first-line therapy entered a phase II study. They received two i.p. 5 day cycles of activated PBMC retargeted with OCTR. Despite unfavorable tumor characteristics, 7 of 26 patients (27%) showed complete or partial intraperitoneal responses with strict surgicopathologic evaluation. In most cases, the disease relapsed outside the peritoneal cavity, and in 1 case complete intraperitoneal response was accompanied by progression in retroperitoneal lymph nodes. The morbidity was mild to moderate and transient. Combination of i.v. and i.p. administration of OCTR-retargeted lymphocytes will possibly lead to extraperitoneal cure. Ongoing clinical studies indicate that the i.v. infusion of up to 8 x 10(8) OCTR-retargeted T lymphocytes does not induce a higher toxicity than the i.p. treatment. To avoid PBMC preactivation, new approaches for delivering accessory signals are under investigation. Preliminary results indicate that nonactivated PBMC retargeted by OCTR in the presence of an anti-CD28 monoclonal antibody (mAb) are able to significantly inhibit tumor growth.

Inhibition of bispecific monoclonal antibody (bsAb)-targeted cytolysis by human anti-mouse antibodies in ovarian carcinoma patients treated with bsAb-targeted activated T-lymphocytes

T lymphocytes of 8 patients with ovarian cancer were targeted to the tumor cells using F(ab')2 fragments of a bispecific monoclonal antibody (bsAb), specific for CD3 (a component of the T lymphocyte receptor for antigen) and for the folate receptor MOv18 (overexpressed by ovarian carcinoma cells) as part of a phase I/II study. Phase I (days 0 to 3) consisted of increasing intraperitoneal (i.p.) numbers (10(6)-10(9)) of bsAb-targeted T lymphocytes plus low-dose interleukin-2 (IL-2). Phase II (days 6 to 13, and 27 to 33) consisted of daily i.p. infusions of 10(9) targeted T lymphocytes, 2 mg soluble bsAb, and low-dose IL-2. Using enzyme-linked immunosorbent assays (ELISA), human anti-mouse antibodies (HAMA) were detected in all patients: in the serum from day 13 onwards and in the peritoneal fluid from day 20 onwards. A significant proportion of the HAMA appeared to be directed against the idiotypes of the bsAb specific for CD3 and MOv18, as suggested by (1) the clearly higher ELISA titers against OC/TR bsAb as compared to those against a monoclonal antibody (MAb) with unrelated specificity, and (2) failure to abrogate the capacity of peritoneal fluid containing HAMA to block the binding of OC/TR bsAb to MOv18+ or CD3+ cells by absorption of human anti-mouse IgG-framework antibodies in peritoneal fluid to immobilized mouse IgG. The OC/TR-targeted cytolysis of the MOv18+ ovarian carcinoma cell line Igrov-I by autologous T lymphocytes was inhibited by peritoneal fluid samples containing relatively high HAMA titers. Such inhibitory activity was never detected at the start of phase II, but coincided with the last series of i.p. infusions of targeted T lymphocytes in 2 patients.

Bispecific monoclonal antibody therapy of B-cell malignancy

Bispecific monoclonal antibodies (bsAbs) that recognize CD3 with one arm and a tumor associated antigen with the other arm can retarget T-cells toward tumor cells in an MHC independent manner, thereby combining the specificity of monoclonal antibodies with the power of the cellular immune system. B-cell malignancies are particularly attractive as targets for anti-CD3-based bsAb therapy because of their sensitivity to other forms of antibody therapy, and the extent to which B-cells and T-cells communicate at the molecular level. BsAbs that recognize CD3 and a number of antigens on malignant B-cells have been shown in vitro to be capable of retargeting T-cells. In animal models of B-cell malignancy, bsAb can eliminate tumor loads that are resistant to unmodified monoclonal antibody therapy. Ongoing early clinical trials in advanced B-cell lymphoma indicate CD3-based bsAbs have significant biologic effects, and suggest they have anti-tumor activity as well. A number of significant questions relating to bsAb therapy of B-cell malignancies remain. It is unclear what role both endogenously produced and exogenously administered cytokines are likely to play. Further exploration of whether bsAb can induce T-cells to target to tumor will also be required before the true promise of this novel form of immunotherapy can be determined.

Purification of bispecific F(ab')2 from murine trinoma OC/TR with specificity for CD3 and ovarian cancer

A study was made of the stability of the murine bispecific trinoma OC/TR with respect to secretion of both types of parental heavy and light chains. OC/TR is a cell line producing bispecific antibody that reacts with the CD3 antigen on T cells and the folate-binding receptor--frequently found to be overexpressed on ovarian carcinoma cells. Of the 10 different IgG combinations theoretically possible with 2 heavy and 2 light chains, 6 combinations were secreted. Subclones varied considerably in relative production of the two parental heavy and light chains. A detailed analysis was made of the binding characteristics and retargeting activity of each of the IgGs produced. From a clone producing a relatively high quantity of bispecific IgG, a large-scale production was initiated. The purification of clinical grade bispecific F(ab')2 from harvest fluids is described. The yield from this purification process was found to be comparable to the yield of bispecific F(ab')2 after chemical cross-linking of two different Fab'.

Cure of xenografted human tumors by bispecific monoclonal antibodies and human T cells

Tumor immunotherapy should increase both the number of T cells that kill the tumor and the likelihood that those cells are activated at the tumor site. Bispecific monoclonal antibodies (Bi-mAbs) were designed that bound to a Hodgkin's tumor-associated antigen (CD30) on the tumor and to either CD3 or CD28 on the T cell. Immunodeficient mice were cured of established human tumors when mice were treated with both the CD3-CD30 and the CD28-CD30 Bi-mAbs and then given human peripheral blood lymphocytes that had been incubated with the CD3-CD30 Bi-mAb and cells that expressed CD30. The enrichment of human T cells within the tumor and the fact that established tumors can be cured may indicate in situ activation of both the T cell receptor and the costimulatory pathway.

Expression and characterization of a chimeric bispecific antibody against fibrin and against urokinase-type plasminogen activator

We have produced a chimeric bispecific antibody that has dual specificity of human fibrin and urokinase-type plasminogen activator (u-PA). Complementary DNAs for variable regions of both anti-fibrin and anti-u-PA antibodies were cloned from two murine hybridomas secreting respective antibodies using polymerase chain reaction (PCR) techniques, and joined to cDNAs for human constant regions to form chimeric antibody genes. Both of two expression vectors for chimeric anti-fibrin and chimeric anti-u-PA antibodies were sequentially introduced into Chinese hamster ovary cells, and stable transfectants secreting the chimeric bispecific antibody were obtained. The highest producer transfectant (SULF/C2-30) secreted high level (about 40 micrograms ml-1) of total chimeric IgG and about 2% of the IgG had the bispecific activity of binding with both antigens. The chimeric bispecific antibody was purified by a combination of affinity chromatographies employing antigen-coupled columns and hydroxyapatite high-performance liquid chromatography. The purified chimeric bispecific antibody significantly enhanced the thrombolytic potency of single chain u-PA in an in vitro clot lysis assay as well as the original murine bispecific antibody.

Analysis of production, purification, and cytolytic potential of bi-specific antibodies reactive with ovarian-carcinoma-associated antigens and the T-cell antigen CD3

OV-TL3 and MOv 18 MAbs, due to their restricted specificity, have been successfully used to visualize ovarian cancer in patients and might therefore be used to develop therapies for ovarian cancer. The bi-specific MAbs alpha T3/OC2 and alpha OC/TR (both being combinations of MOv18 and alpha CD3) have been shown to lyse ovarian tumor cells in vitro. To evaluate the relative merits of MOv18/CD3 and OV-TL 3/CD3, the present study was undertaken in which the bi-specific MAbs alpha T3/OC2 and alpha OC/TR, and a newly developed bi-specific MAb, OV-TL 3/CD3, were highly purified and compared for specificity, stability, purification and cytolytic potential. The dual specificity of the hybrid-hybridoma supernatants was analyzed by immunohistochemistry, and by testing bi-specific MAb-mediated cytotoxicity against relevant target cells in the presence of effector cells. Stability testing of bi-specific MAb-producing hybridomas showed that, after sub-cloning, clones stably produced up to 40% bi-specific MAb even after prolonged in vitro culture. The purification of the bi-specific fractions was performed with protein A and by ion-exchange high-pressure liquid chromatography, depending on the sub-class combination of the bi-specific MAb. The purified bi-specific MAbs were tested for their ability to mediate target-cell lysis with the use of cytotoxic T-cell clones and activated peripheral-blood lymphocytes. The purified alpha T3/OC2, alpha OC/TR, and OV-TL3/CD3 were all able to mediate highly specific lysis of various ovarian-carcinoma cell lines. No correlation was found between the level of antigen expression and bi-specific MAb-mediated cytolysis.

CD30-antigen-specific targeting and activation of T cells via murine bispecific monoclonal antibodies against CD3 and CD28: potential use for the treatment of Hodgkin's lymphoma

Cross-linking of specific tumor antigens with the T-cell-associated CD3 and CD28 antigens can increase IL-2 secretion, proliferation and antigen-specific cytotoxicity in resting T cells. This cross-linking can be achieved effectively by bispecific monoclonal antibodies (BiMAb) with specificity for both the tumor antigen and CD3 or CD28 antigen, respectively. To take advantage of the enhanced activation of CD3 pre-activated T cells by additional activation via the CD28 antigen, BiMAb OKT3/HRS-3 with reactivity to both CD3 and the Hodgkin's-lymphoma-associated CD30 antigen and the BiMAb 15E8/HRS-3 with reactivity to both CD28 and CD30 antigen were generated by hybridoma fusion. Resting T cells, represented by Jurkat cells (CD3+/CD28+) were specifically activated to produce IL-2 by co-cultivation with an EBV-transformed B-cell line (LAZ509, CD30+/CD19+) only in the presence of the CD30/CD28 cross-linking BiMAb and an additional cross-linking anti-CD3/CD19 BiMAb (OKT3/6A4). Neither the cross-linking BiMAbs alone nor any combination of the monospecific parental MAbs induced a comparable IL-2 production by Jurkat cells in the presence of LAZ509. In addition, using a combination of these BiMAbs, an antigen-dependent cytotoxicity was induced by targeting APC-depleted peripheral blood lymphocytes to CD30+ L540 cells. T cells, previously specifically activated by CD3/CD30 in the presence of CD30 antigen, were cytotoxic to CD30+ cell lines only after incubation with BiMAb anti-CD28/CD30. Neither of the BiMAbs nor any of the parental antibodies induced a comparable effect. Our results indicate that such BiMAbs may offer a new approach for specific immunotherapy of Hodgkin's lymphoma, which takes advantage of cytokine secretion and cytotoxicity of activated T cells.

Reflection contrast microscopy of ultrathin sections in immunocytochemical localization studies: a versatile technique bridging electron microscopy with light microscopy

Reflection contrast microscopy (RCM) of ultrathin sections was recently introduced as a sensitive technique for visualization with enhanced definition in immunogold histochemistry. Experience of using RCM as a major tool in immunocytochemical research in different fields is summarized, e.g. oncology, nephrology and embryology. The sensitive visualization of immunocytochemical labels, gold particles or peroxidase-diaminobenzidine deposits in or on ultrathin sections, by RCM instead of electron microscopy is demonstrated. RCM of ultrathin sections is an adequate light microscopical alternative for immunoelectron microscopy, since an overview of both label and tissue is obtained with a high image definition and high contrast of label. In the studies presented, RCM is shown to provide a better gradation in staining intensity and staining pattern than other light microscopical methods. Moreover, a precise localization of multiple labels is obtained with this method. Besides the applications shown, ultrathin section visualization by RCM is very useful for correlative light- and electron microscopical studies of fine structures. Commercially available fluorescence microscopes can be adapted for proper RCM functioning; an adaptation scheme and list of microscopes tested is provided.

Cell retargeting by bispecific monoclonal antibodies. Evidence of bypass of intratumor susceptibility to cell lysis in human melanoma

Intratumor heterogeneity for susceptibility to cytotoxic T lymphocytes (CTL)-mediated lysis represents a major obstacle to cancer adoptive immunotherapy. To overcome the heterogeneity observed in terms of susceptibility of target cells to cell-mediated lysis, in this study we used two purified bispecific monoclonal antibodies (bsmAbs) that recognize molecules expressed by cytotoxic effector cells (CD3 and IgG Fc receptorial molecules), as well as one high molecular weight melanoma-associated antigen (HMW-MAA). The ability of these reagents to enhance or induce a relevant in vitro cytotoxic activity by a CTL clone (CTL 49) isolated from PBL of a melanoma patient was tested on a large panel of autologous and allogeneic melanoma cell lines and clones. Functional studies revealed that the CTL 49 clone lysed all the HMW-MAA+ tumor lines in the presence of bsmAbs and that these reagents affected the target lysis in a cooperative fashion. The effectiveness of bsmAbs in overcoming the heterogeneous susceptibility of human melanoma cells to cell-mediated lysis may find practical implications in cancer adoptive immunotherapy.

Retargeting of human lymphocytes against human ovarian carcinoma cells by bispecific antibodies: from laboratory to clinic

We have selected a monoclonal antibody (MOv18) reactive with ovarian carcinoma, which exhibits a restricted tumor specificity, a high affinity constant and which recognizes a 38-kDa glycoprotein homogeneously expressed on the cell surface of 90% of human ovarian carcinomas. Localization studies with radiolabelled MOv18 showed that MOv18 could specifically reach ovarian carcinoma cells growing in the peritoneal cavity of nu/nu mice. MOv18 did not mediate antibody-dependent cellular cytotoxicity via Fc and could not be used as a carrier for toxins due to poor internalization of the antigen-antibody complex. Bispecific F(ab')2 antibodies made with MOv18 and an antibody reactive with CD3 were able to redirect the cytotoxicity of peripheral blood lymphocytes (PBL) against ovarian carcinoma cells both in vitro and in vivo in an animal model. The treatment of athymic mice bearing a human ovarian carcinoma intraperitoneally, with human PBL coated with the bispecific F(ab')2, significantly prolonged survival of the animals compared with tumour-bearing untreated and control mice treated with PBL alone. Four ovarian cancer patients have been treated with autologous lymphocytes coated with this bispecific F(ab')2 in a phase I clinical trial. No serious side-effects were observed but patients developed human anti-murine antibodies mainly directed against the idiotype of MOv18. We have now begun phase II clinical trials in ovarian cancer patients.

In vitro anti-tumor activity of anti-c-erbB-2 x anti-CD3 epsilon bifunctional monoclonal antibody

With the aim of developing an effective cancer immunotherapy for common epithelial cancer, a new class of bifunctional antibody (BFA) was developed; one arm of this BFA recognized c-erbB-2 gene product, and the other arm recognized CD3 epsilon, a T-cell specific surface antigen. Application of this BFA with human peripheral blood lymphocytes exhibited specific anti-tumor activity in vitro on a breast tumor cell line, ZR-75-1, which expressed abundant c-erbB-2 gene product on its cell surface. These results indicate that BFA recognizing an oncogene product on cell surface is a potential new agent for cancer immunotherapy.

Membrane association and shedding of the GPI-anchored Ca-MOv18 antigen in human ovary carcinoma cells

The antigen recognized by the MOv18 MAb (Ca-MOv18) was recently shown to be a glycosylphosphatidylinositol (GPI)-linked protein. In this report we show that GPI-anchorage is not limited to IGROVI cells nor to other ovary carcinoma cell lines, but Ca-MOv18 was also found to be sensitive to phosphatidylinositol-specific phospholipase C (PI-PLC) treatment on fresh ovarian cancer cells. Furthermore, we found a heterogeneous sensitivity of Ca-MOv18 to PI-PLC cleavage, not only among the different cells studied but also in different experiments performed on the same cell line, during extended periods of time in culture. Sensitivity to PI-PLC cleavage was determined by immunofluorescence on live cells and by double-determinant radioimmunoassay of the antigen released in the supernatant. The specificity of the PI-PLC cleavage was demonstrated as follows: (a) TX114 solubilized Ca-MOv18 shifts from the detergent to the aqueous phase after treatment with PI-PLC; (b) on membrane preparations, PI-PLC specifically released a fraction of the antigen, which is distinct from the weakly associated form released by high-salt treatment; (c) Ca-MOv18 from IGROVI expressed the cross-reacting determinant (CRD), which is characteristic of GPI-linked molecules. The absence of CRD expression on the spontaneously released protein and the possibility of artificially inducing antigen shedding during the resynthesis of Ca-MOv18 which follows bacterial PI-PLC treatment are interesting points which need to be further investigated in order to understand the physiology of the Ca-MOv18 tumor antigen.

Bifunctional antibodies and their potential clinical applications

Bifunctional antibodies are monovalent, bispecific, antibody-derived molecules. They have been produced by both chemical and biological means. They are thought to have several advantages over monoclonal antibodies in both immunotherapy and immunodiagnosis. Bifunctional antibodies have been shown to be efficient in the targeting of drugs, toxins, radiolabelled haptens and effector cells on to diseased tissues, primarily cancer cells. In addition, bifunctional antibodies have been used to develop novel immunoassays. The full potential of bifunctional antibodies has yet to be realised.

Enhancement of the lytic activity of cloned human CD8 tumour-infiltrating lymphocytes by bispecific monoclonal antibodies

We have isolated tumour-infiltrating lymphocytes (TIL) clones from a patient with renal cell cancer. The cloning frequency and the effector function were measured. No difference in cloning frequency (r2 = 0.97, frequency = 1:13) was observed between TIL expanded with allogeneic versus autologous feeder cells. Sixty-four clones expanded with autologous feeder cells and 37 clones expanded with allogeneic feeder cells were assayed for cytolytic activity on an autologous primary renal cell carcinoma (RCC) culture, an allogeneic RCC line, and on the K562 and Daudi cell lines. Most of these clones were also phenotyped. Although TIL clones expressing cytotoxic activity for RCC lines could be generated with both feeder cell preparations, none of the clones tested showed specificity for cells from autologous primary RCC cultures. However, in the presence of relevant bispecific MoAbs (alpha OC/TR) all CD8+ TIL clones tested could be induced to lyse autologous RCC cultures. Furthermore, the cytolytic activity of all CD8+ clones tested against allogeneic RCC lines could be induced or further enhanced by alpha OC/TR or CD3/G250 bispecific MoAbs. In contrast, none of the CD4+ clones tested showed lytic activity. Quantitatively the cytotoxic response in the presence of alpha OC/TR or CD3/G250 of CD8+ TIL clones against G250+ and MOv18+ cell lines appears to be associated with the level of antigen expression on the target cells. Our results suggest that: (i) expansion of TIL with allogeneic or autologous feeder cells does not effect the lytic profile of the clones; (ii) the use of bispecific MoAbs may overcome a lack of specificity of cytotoxic T lymphocytes.

Effects of HC antibody in autologous tumor-specific cytotoxicity by human melanoma tumor-infiltrating lymphocytes

Heteroconjugate (HC) antibody has a potential use in cancer biotherapy because of its ability to mimic antigenic specificity and induce cytotoxicity in the activated lymphocytes against various tumor cells. This study investigated the effects of HC antibody (anti-CD3 MAb x anti-p97 melanoma cell MAb) in autologous tumor-specific cytotoxicity by interleukin-2 (IL-2)-activated melanoma tumor-infiltrating lymphocytes (TILs). HC antibody significantly augmented p97pos uncultured autologous tumor cell lysis mediated by effector TILs or cytotoxic T lymphocyte (CTL) clones derived from TIL. It did not significantly increase p97mix autologous tumor-cell lysis and slightly inhibited the lysis only at higher E:T ratios and higher concentrations (greater than or equal to 100 ng/ml). It inhibited p97neg autologous tumor-cell lysis. HC antibody respectively induced potent lysis of p97pos or modest lysis of p97mix tumor cells by allogeneic effector TILs as well as PBMC. In contrast, parental anti-CD3 MAb primarily suppressed the autologous tumor-specific cytotoxicity, and did not induce lysis of uncultured melanoma cells, regardless of differences in expression of p97 antigens on tumor cells. Although parental anti-p97 MAb did not augment or suppress the autologous tumor-specific cytotoxicity, it completely abrogated HC antibody-mediated augmentation of p97pos autologous tumor cell lysis by effector TILs. Anti-class-I MAb, but not anti-DR MAb, suppressed the autologous tumor-specific cytotoxicity, but failed to block HC antibody-mediated augmentation of p97pos autologous tumor-cell lysis. These results suggest that the levels of p97 antigen expression largely influenced HC antibody-mediated modulation of TIL cytotoxicity against uncultured autologous tumor cells.

Localization of monoclonal antibody G250 and bispecific monoclonal antibody CD3/G250 in human renal-cell carcinoma xenografts: relative effects of size and affinity

A study was made of the relative effects of size and binding strength of various forms of the monoclonal antibody (MAb) G250, reacting with primary and metastatic human renal-cell carcinoma (RCC), on the localization in human RCC xenografts in nude mice. Preferential tumor localization was demonstrated after injection of 125I-labelled intact IgG, with increasing tumor/non-tumor ratios in time. Approximately 27.4% of the injected dose/gram (%ID/g) was localized in the xenograft 24 hr post-injection. A control MAb did not preferentially localize in xenografts. With F(ab')2 fragments, higher tumor/blood ratios were obtained, although a lower percentage of injected dose per gram was bound to the tumor, 24 and 48 hr post-injection. Using a bispecific MAb CD3/G250 F(ab')2 fragment, which reacts with CD3 on human T lymphocytes and binds monovalently to RCC, an enhanced accumulation in tumor tissue was also observed. The %ID/g tumor obtained with bispecific CD3/G250 F(ab')2 was comparable with %ID/g tumor found with G250 F(ab')2. The 10-fold lower binding affinity to RCC compared with intact IgG or F(ab')2 had only marginal effects on %ID/g tumor. These results show that MAb G250 preferentially localizes to RCC xenografts. Because injection of F(ab')2 fragments resulted in higher tumor/non-tumor ratios, G250 F(ab')2 may therefore be more suitable for diagnostic evaluation of RCC in patients. The tumor uptake is more dependent on size than on affinity. Furthermore, the data obtained with bispecific MAb CD3/G250 F(ab')2 support the hypothesis that this bispecific MAb may be able to target cytotoxic T lymphocytes to RCC in humans to mediate destruction of RCC.

Radioimmunoscintigraphy of ovarian cancer with the MOv18 monoclonal antibody

The monoclonal antibody (Mab) 131I-MOv18 was administered to 30 patients with ovarian carcinoma intravenously (n = 20) and intraperitoneally (n = 10). After intraperitoneal administration, higher tumour uptake (mean values 1.3% vs. 0.8%) and a better tumour/background ratio (mean values 2.8 vs. 1.9) than after intravenous injection were obtained. Moreover, after intraperitoneal administration the uptake in non-affected organs, such as liver and spleen, was lower. However, occasionally the favourable results of the intraperitoneal route were cancelled by persistent pelvic non-specific accumulations of 131I-MOv18. The possibility to change the biodistribution pattern in the latter cases with peritoneal washing was evaluated. 3 patients were submitted to this procedure and an improvement in the radiotracer biodistribution was obtained in 1 case. With regard to tumour detection, the average sensitivity (73%) showed a significant difference from the sensitivities for abdominal (61%) and pelvic lesions (90%). No false positive results were noted.

Use of combination of monoclonal antibodies directed against three distinct epitopes of a tumor-associated antigen: analysis of cell binding and internalization

Three monoclonal antibodies (MAbs), MOv17, MOv18 and MOv19 with tumor-restricted specificity for human ovarian carcinoma, were tested alone or in double combination with the aim of analyzing their binding and internalization behavior on different in vitro cell lines. Biochemical studies indicated that the 3 MAbs were directed against 3 epitopes of the same 38 kDa surface molecule. By immuno-electron-microscopy they exhibited a different internalization behavior since MOv17 induced evident endocytosis through coated vesicles, whereas MOv18 gave rise to occasional uncoated vesicles and MOv19 was completely unable to promote internalization of the relevant molecule. When tested 2 by 2 there was a binding synergy in one of the 9 possible combinations (125I-labelled MOv18 and unlabelled MOv19), but no change in the internalization behavior. The binding synergy, which was highly reproducible, was temperature-dependent and was also evident on glutaraldehyde-fixed cells. A metabolism involvement is therefore unlikely. This could be attributed to an easier accessibility of the CaMOv18 due to a conformational change of the molecule after MOv19 MAb binding.

Bispecific monoclonal antibodies directed to CD16 and to a tumor-associated antigen induce target-cell lysis by resting NK cells and by a subset of NK clones

CD16 surface antigens represent activatory molecules in CD3-16+ NK cells. In order to target NK cells against relatively NK-resistant ovarian carcinomas, we used an anti-CD16 monoclonal antibody (MAb) (VD4), together with an anti-ovarian carcinoma-associated antigen (MOV19), to construct biMAbs. To this end, hybrid hybridomas were generated by fusing a TK-deficient VD4 hybridoma mutant with a HGPRT-deficient MOV19 hybrid. Supernatants from hybrid hybridomas that had been selected in HAT medium were screened for their ability to induce a CD3-16+ NK clone to lyse an MOV19+ ovarian carcinoma cell line in a 4-hr 51Cr-release assay. The NMB.45 hybrid hybridoma secreted a biMAb which triggered lysis of MOV19+ but not of MOV19- target cells. Some degree of target cell lysis was also observed with MOV19 MAb (due to ADCC mechanisms), while the VD4 MAb was ineffective. HPLC fractionation of MAbs secreted by the hybrid hybridoma made it possible to identify 4 different peaks, one of which appeared to contain functional biMAb molecules. HPLC-purified biMAb (100 ng/ml) induced resting PBL to lyse the "NK-resistant" IGROVI ovarian carcinoma cell line. Fresh MOV19+ tumor cells were also lysed, although with lower efficiency. When IL-2-activated lymphocytes were used as a source of effectors, biMAb caused only minor increases in the IL-2-induced cytolytic activity. Further analyses of the effect of biMAb were performed at the clonal level. Among CD3-16+ NK cell clones, a clear enhancing effect could be observed only in GL183+ but not in GL183- clones. In CD3+ cytotoxic clones a triggering effect could be detected in one out of 4 TCR gamma/delta+ clones but not in TCR alpha/beta+ clones.

Augmentation of interleukin-2-induced activation of human melanoma tumor-infiltrating lymphocytes by heteroconjugate antibody

Heteroconjugate (HC) antibody (anti-CD3 mAb x anti-p97 melanoma mAb) or monomeric anti-CD3 mAb by itself did not induce proliferation of uncultured melanoma tumor-infiltrating lymphocytes (TILs). They also failed to induce IL-2 production in uncultured TILs, although anti-CD3 mAb, but not HC antibody, stimulated IL-2 production in peripheral blood mononuclear cells (PBMCs). Sequential treatment of uncultured TILs from p97-antigen-positive (p97+) melanomas with HC antibody, followed by washing and incubation with interleukin-2 (IL-2), induced significantly higher proliferation than incubation with IL-2 alone. HC antibody pretreatment led to significantly greater results than with anti-CD3 mAb at a 1 ng/ml level in IL-2-induced proliferation of TILs from p97+ melanomas, similar to those with anti-CD3 mAb at a level of 100 ng/ml. HC antibody (1 ng/ml) pretreatment did not enhance IL-2-induced proliferation of either TILs from p97- melanomas or PBMCs, while anti-CD3 mAb enhanced the proliferation of TILs from some p97- melanomas and PBMCs. Regardless of the pretreatment of uncultured TILs with HC antibody or anti-CD3 mAb, IL-2-activated TILs were cytotoxic primarily only to autologous tumor cells, and their phenotypes remained the same. Thus, HC antibody can augment IL-2-induced activation of TILs only from p97+ melanomas, without altering their pattern of cytotoxicity or phenotype. The findings were consistent with observations at the clonal level. In contrast to anti-CD3 mAb, HC pretreatment of uncultured TILs from only p97+ melanoma prior to limiting-dilution analysis increased the number of proliferating TIL clones, including autologous tumor-specific cytotoxic T lymphocyte clones. These results suggest that use of HC antibody in vivo would be more advantageous than anti-CD3 mAb, with regard to augmentation of IL-2-induced TIL activation.

Preclinical pharmacokinetics and localization studies of the radioiodinated anti-ovarian carcinoma MAb MOv18

The in vivo behavior of the monoclonal antibody (MAb) MOv18, with a restricted specificity for human ovarian carcinoma was analyzed on normal and tumor-bearing animals. The pharmacokinetics of the iodine-labeled MAb carried out in BALB/c mice fits an open two-compartment model. The t1/2 alpha was found not to be influenced by the different iodine isotopes used (125I vs 131I) and by the time between labeling procedures and administration. The t1/2 beta were found to be longer after i.p. than i.v. administration and influenced by the time lapse between preparation and administration. A radiolocalization study was carried out in CD1 nu/nu mice bearing i.p. xenotransplant of the human ovarian carcinoma cell line IGROV1. Tumor/non tumor ratios were higher when the time between administration and sacrifice was short and, for 131I-MOv18, with a short interval between labeling and injection. Even if longer half lives were obtained using 125I-MOv18 and i.p. administration a fairly rapid decrease in the values of the percentage of the injected dose per gram of tumor during the time was noted. These data indicate that this MAb could be considered a good candidate for radiotherapeutic approaches.

Bispecific-monoclonal-antibody-directed lysis of ovarian carcinoma cells by activated human T lymphocytes

Two different bispecific hybrid antibodies were established by fusing a hybridoma producing monoclonal antibody (mAb) against the pancarcinoma antigen KS1/4 with either of the two hybridomas OKT3 and 9.3, secreting antibodies reactive with the T cell determinants CD3 and CD28, respectively. The KS1/4 antibody reacts with a 40-kDa cell-surface glycoprotein antigen that is expressed on the surface of a variety of adenocarcinoma cells, including ovarian carcinoma. The ability of the bispecific antibodies 9.3 x KS1/4 and OKT3 x KS1/4 to direct peripheral blood mononuclear cells (PBMC) specifically against OVCAR-3 ovarian carcinoma target cells was measured in a 4-h 51Cr-release assay. The bispecific antibodies were four to six times more potent in killing the OVCAR-3 target cells when compared to their parental antibodies either alone or in combination. A dose-dependent response was observed in the 10-10,000 ng/ml range. The specificity of the targeting was demonstrated by the complete inhibition of cytotoxic activity following pre-incubation of tumor target cells with the parental mAb and by the lack of killing of KS1/4-negative target cell lines. An evaluation of the efficacy of PBMC from ovarian cancer patients as effector cells revealed that their specific cytotoxicity against OVCAR-3 cells was enhanced severalfold by bispecific antibodies as compared to parental antibodies. Furthermore, stimulation of PBMC with immobilized CD3 and interleukin-2 for 4 days resulted in an enhanced directed killing of human ovarian carcinoma cells by human T effector cells and the bispecific antibodies.

Bifunctional antibodies: concept, production and applications

Immunoglobulins, or antibodies, are monospecific, bivalent antigen-binding molecules. Bifunctional antibodies are bispecific, with each arm binding to a different antigen, and may be produced by biological or chemical methods. Biological production involves the fusion of two monoclonal antibody-producing hybridomas or of an immunised spleen cell and a hybridoma. The resulting hybrid hybridomas (quadromas or triomas) secrete a mixture of parenteral monoclonal antibodies and bifunctional antibody. In chemical production, the parental monoclonal antibodies can be 'chopped up and reconstituted' to produce the bifunctional antibody only. Bifunctional antibodies have a variety of potential uses. They were originally proposed as an aid to cancer chemotherapy where one of the arms of the antibody would bind to a tumour marker and the other to a drug, toxin, or cytotoxic cell. Functional agents can thus be target directly onto tumour cells, accumulating with higher density, yet with reduced side effects for the patient. Further applications have been proposed involving enzyme immobilization and novel immunoassay techniques. This review describes developments that have taken place in bifunctional antibody technology to date.

Interleukin-2. The experience of the Rotterdam Cancer Institute; Daniel den Hoed Kliniek

Between October 1987 and October 1989 we have treated 110 patients with advanced solid tumors with recombinant interleukin-2 (rIL2) based immunotherapy. In renal cell cancer we have studied rIL2 alone, rIL2 combined with rIL2 activated lymphocytes (LAK), and in an ongoing study rIL2 and LAK and alpha-interferon (alpha IFN). There is suggestive evidence of increasingly good results in these consecutive studies. In melanoma the combination of rIL2 and chemotherapy was investigated, followed by an ongoing study of rIL2 and alpha IFN. In these studies rIL2 has been administered as a continuous intravenous infusion of 18 x 10(6) International Units/m2/day for 5 days (18 x 10(6) IU = 3 x 10(6) Cetus Units = 6.9 Biological Response Modifiers Program (BRMP) Units). Patients with non-small cell lung cancer are entered in a phase I-II study of rIL2 and alpha IFN. The rIL2 administration differs from the above mentioned schedule in that rIL2 is given at a maximum dose of 6 x 10(6) IU/m2/day for 28 days on an outpatient basis. In a phase I study we have searched for the maximum tolerated dose of a daily time 4 schedule of rIL2. In the second part of this study a daily time 4 schedule, every week for 4 weeks is being investigated. Finally, we are investigating the safety and efficacy of local regional administration of rIL2 in patients with head and neck cancer, mesothelioma, and liver metastasis of colorectal cancer.

Gene transfer by retrovirus-derived shuttle vectors in the generation of murine bispecific monoclonal antibodies

The present study reports on the use of gene transfer by retrovirus-derived shuttle vectors in the generation of hybrid hybridomas secreting bispecific monoclonal antibodies. neo- and dhfr- genes were infected into distinct murine hybridomas, thus conferring a dominant resistance trait to geneticin (G418) and to methotrexate. The vectors employed were replication-deficient and dependent on complementation by a helper virus provided by the irradiated packaging lines. After cocultivation with the relevant packaging cell lines, stable hybridoma lines expressing the selectable markers were easily obtained and were then suitable for conventional somatic fusion. This high-efficiency method was used to generate two bispecific monoclonal antibodies simultaneously targeting molecules expressed on cytotoxic cells (i.e., T lymphocytes and natural killer cells) against a human melanoma-associated antigen.

Biodistribution and plasma survival in mice of anti-melanoma monoclonal antibody cross-linked to OKT3

Anti-melanoma monoclonal antibody XMMME-001 was cross-linked to anti-CD3 monoclonal antibody OKT3 with succinimidyl 3(2-pyridyldithio)propionate (SPDP), and 2-iminothiolane. The dimer heteroconjugate was purified by HPLC gel filtration, labeled with 131I, and 10 micrograms was injected into each of 24 BALB/c mice. The dimeric heteroconjugate's blood survival in sequentially bled mice (n = 3) and its biodistribution in organs of sacrificed mice (n = 21) were studied. In plasma, the heteroconjugate showed an alpha phase with a half-life of 4 h, and a beta phase with a half-life of about 18 h. Electrophoretic analysis of labeled heteroconjugate in plasma showed that the half-life of disulfide bonds linking the monoclonal antibodies was approximately 7-8 h. Radioactive heteroconjugate accumulated primarily in the liver; significant uptake was also seen in white blood cells and spleen. Very little radioactivity accumulated in kidney, lung, or colon. As a comparison, SPDP-derivatized anti-melanoma antibody was studied by the same methods. It showed an average alpha-phase half-life of 12.5 h; its maximum accumulation in liver or white blood cells was less than 30% of that of the heteroconjugate. Very low levels accumulated in other tissues. The results imply that the shorter half-life in plasma of the heteroconjugate is primarily determined by clearance due to its larger size and conformation, not the lability of cross-linking disulfide bonds.

Bispecific antibodies reactive with the multidrug-resistance-related glycoprotein and CD3 induce lysis of multidrug-resistant tumor cells

We describe the lysis of multidrug-resistant (MDR) tumor cells by various lymphocytic effector cells, retargeted with bispecific antibodies (heteroconjugates). The Ab-heteroconjugate used was prepared by chemically cross-linking the OKT3 monoclonal antibody (MAb) reactive with CD3 antigen on T lymphocytes, with the MRK16 MAb, which recognizes the MDR-associated P-glycoprotein. Cloned TCR alpha beta/CD3+ T lymphocytes, OKT3-activated peripheral-blood mononuclear cells and peripheral-blood mononuclear blood lymphocytes, stimulated with allogeneic irradiated cells in a mixed lymphocyte culture, could be induced to lyse MDR ovarian tumor cells in the presence of Ab-heteroconjugate CD3/MRK16, whereas the drug-sensitive parental tumor cells lacking the P-glycoprotein were not lysed by these retargeted effector cells. Cloned TCR gamma delta/CD3+ T lymphocytes showed a high MHC-unrestricted lysis of MDR tumor cells. Addition of Ab-heteroconjugate CD3/MRK16 could therefore not enhance target-cell lysis. Melanoma tumor cells transfected with the mdr-I gene which codes for the P-glycoprotein were also efficiently lysed by Ab-heteroconjugate retargeted cloned TCR alpha beta/CD3+ T cells. Tumor cell lines derived from organs known to express the P-glycoprotein also were lysable by the retargeted effector cells.