Efficient inhibition of human B-cell lymphoma xenografts with an anti-CD20 x anti-CD3 bispecific diabody

Loop CD20/CD19 CAR-T cells eradicate B-cell malignancies efficiently

CD19 chimeric antigen receptor (CAR) T cells have shown robust efficacy in relapsed and refractory acute lymphoblastic leukemia (R/R ALL), but compromising result in chronic lymphoblastic leukemia (CLL) and non-Hodgkin's lymphoma (NHL). CD19 relapse and the lack of CAR-T cell persistence which result in treatment failure are considerable obstacles to overcome. CAR-T targeting CD20 is an option for salvaging CD19 CAR-T failure. Previous studies have established variant structures of bispecific CAR-T which could avoid antigen-loss and immune escape. Here, we constructed tandem and loop CAR structures targeting both CD19 and CD20 antigen. Bispecific CAR-T cells could eliminate either CD19 or CD20 negative lymphoma cells, suggesting they exhibited dual antigen targeting of CD19 and CD20. By comparing the efficiency of four bispecific CAR modified T cells, it was found that loop2019 CAR was the best structure among them to eradicate lymphoma cell lines and patients' primary lymphoma or CLL cells in a very low dose in vitro and prolong the survival time dramatically in lymphoma xenograft mice model. These data highlighted the potential of loop2019 CAR-T in clinical treatment.

Induced CD20 Expression on B-Cell Malignant Cells Heightened the Cytotoxic Activity of Chimeric Antigen Receptor Engineered T Cells

CD20 is an effective immunotherapy target for CD20⁺ B-cell malignant cells. Monoclonal antibody, especially rituximab, has been a conventional strategy in the treatment of B-cell malignancies such as non-Hodgkin's lymphoma. However, treatment with monoclonal antibodies has not been enough to overcome the refractory/relapse problems. Chimeric antigen receptor engineered T (CAR-T) cells have exhibited excellent therapeutic effect on lymphocytic leukemia in recent years. In this study, a CD20-specific CAR was constructed and the cytotoxic efficacy of CD20 CAR-T cells on B-cell malignant cells was evaluated by CD107a degranulation, pro-inflammation cytokine production, and true lytic ability in vitro and in vivo. It was found that CD20 CAR-T cells possessed stronger cytotoxic ability against CD20 highly expressed cells. Furthermore, when histone deacetylase inhibitor was used to enhance the expression of CD20 antigen on the surface of B-cell malignant cells via inducing acetylation of H3K9 on CD20 promoter site, it revealed that the cytotoxicity of CD20 CAR-T cells against histone deacetylase inhibitor-treated B-cell malignant cells was significantly enhanced.

A bi-specific inhibitor targeting IL-17A and MMP-9 reduces invasion and motility in MDA-MB-231 cells

The cytokine IL-17A is associated with the progression of various cancers, but little is known about the molecular cross-talk between IL-17A and other tumor-promoting factors. Previous studies have shown that the IL-17A-mediated invasion of breast cancer cells can be inhibited by selective antagonists of the matrix metalloproteinase 9 (MMP-9), suggesting that the cross-talk between IL-17A and MMP-9 may promote cancer invasiveness and metastasis. Here, we present a novel strategy for developing cancer therapeutics, based on the simultaneous binding and inhibition of both IL-17A and MMP-9. To this end, we use a bi-specific heterodimeric fusion protein, comprising a natural inhibitor of MMPs (N-TIMP2) fused with an engineered extracellular domain (V3) of the IL-17A receptor. We show that, as compared with the mono-specific inhibitors of IL-17A (V3) and MMP-9 (N-TIMP2), the engineered bi-specific fusion protein inhibits both MMP-9 activation and IL-17A-induced cytokine secretion from fibroblasts and exhibits a synergistic inhibition of both the migration and invasion of breast cancer cells. Our findings demonstrate, for the first time, that dual targeting of inflammatory (IL-17A) and extracellular matrix remodeling (MMP) pathways can potentially be used as a novel therapeutic approach against cancer. Moreover, the platform developed here for generating the bi-specific IL-17A/MMP-9 inhibitor can be utilized for generating bi-specific inhibitors for other cytokines and MMPs.

T cell engaging bispecific antibody (T-BsAb): From technology to therapeutics

Harnessing the power of the human immune system to treat cancer is the essence of immunotherapy. Monoclonal antibodies engage the innate immune system to destroy targeted cells. For the last 30years, antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity have been the main mechanisms of anti-tumor action of unconjugated antibody drugs. Efforts to exploit the potentials of other immune cells, in particular T cells, culminated in the recent approval of two T cell engaging bispecific antibody (T-BsAb) drugs, thereby stimulating new efforts to accelerate similar platforms through preclinical and clinical trials. In this review, we have compiled the worldwide effort in exploring T cell engaging bispecific antibodies. Our special emphasis is on the lessons learned, with the hope to derive insights in this fast evolving field with tremendous clinical potential.

Redirecting T cells to hematological malignancies with bispecific antibodies

There is a need to improve outcomes for patients with recurrent and/or refractory hematological malignancies. Immunotherapy holds the promise to meet this need, because it does not rely on the cytotoxic mechanism of conventional therapies. Among different forms of immunotherapy, redirecting T cells to hematological malignancies with bispecific antibodies (BsAbs) is an attractive strategy. BsAbs are an "off-the-shelf" product that is easily scalable in contrast to adoptive T-cell therapies. Among these, the bispecific T-cell engager blinatumomab has emerged as the most successful BsAb to date. It consists of 2 single-chain variable fragments specific for CD19 present on B-cell malignancies and CD3 expressed on almost all T cells. Blinatumomab has shown potent antitumor activity as a single agent, particularly for acute lymphoblastic leukemia, resulting in its US Food and Drug Administration approval. However, although successful in inducing remissions, these are normally short-lived, with median response durations of <1 year. Nevertheless, the success of blinatumomab has reinvigorated the BsAb field, which is bustling with preclinical and clinical studies for not only B-cell-derived lymphoblastic leukemia and lymphoma but also acute myeloid leukemia and multiple myeloma. Here, we will review the successes and challenges of T-cell-targeted BsAbs for the immunotherapy of hematological malignancies with special focus on conducted clinical studies and strategies to improve their efficacy.

Treatment of Human B-Cell Lymphomas Using Minicircle DNA Vector Expressing Anti-CD3/CD20 in a Mouse Model

Bispecific antibodies (BsAbs), capable of directing T cells to kill specific cancer cells by transiently binding the two cell types, have emerged as one class of promising cancer immunotherapies. However, their wide clinical application might be hampered by two deficiencies: high cost and inconvenience in drug administration. This study presents concept-proving data that these problems could be bypassed by using an enhanced nonviral DNA vector minicircle (MC) to produce BsAb in vivo. It was found that the anti-CD3/CD20 produced from the minicircle (MC.CD20) could effectively mediate the T-cell killing of multiple CD20-positive human B-cell lymphoma cell lines in vitro. More importantly, it was demonstrated that delivery of 5 μg of MC.CD20 to mouse liver via hydrodynamic injection resulted in both the expression of a therapeutic level of anti-CD3/CD20 throughout the 32-day experiment and effective anticancer activity in a B-cell lymphoma xenograft mouse model. The data suggest that MC encoding the BsAbs may become an attractive cancer immunotherapy modality based on its excellent features of safety, efficacy, and convenience in both preparation and use, and its affordability once the delivery technology matures.

A tale of two specificities: bispecific antibodies for therapeutic and diagnostic applications

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Recombinant DNA technologies are leading the rapid expansion of bispecific antibody formats.

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The therapeutic potential of bispecific antibodies is being realized through creative design.

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Bispecific antibodies are potentially underutilized reagents for diagnostics.

Artificial manipulation of antibody genes has facilitated the production of several unique recombinant antibody formats, which have highly important therapeutic and biotechnological applications. Although bispecific antibodies (bsAbs) are not new, they are coming to the forefront as our knowledge of the potential efficacy of antibody-based therapeutics expands. The next generation of bsAbs is developing due to significant improvements in recombinant antibody technologies. This review focuses on recent advances with a particular focus on improvements in format and design that are contributing to the resurgence of bsAbs, and in particular, on innovative structures applicable to next generation point-of-care (POC) devices with applicability to low resource environments.

Construction and humanization of a functional bispecific EGFR × CD16 diabody using a refolding system

We previously reported the construction and activity of a humanized, bispecific diabody (hEx3) that recruited T cells towards an epidermal growth factor receptor (EGFR) positive tumor. Herein, we describe the construction of a second functional, fully humanized, anti-EGFR bispecific diabody that recruits another subset of lymphocyte effectors, the natural killer cells, to EGFR-expressing tumor cells. After we confirmed that an anti-EGFR × anti-CD16 bispecific diabody (Ex16) consisting of a previously humanized anti-EGFR variable fragment (Fv) and a mouse anti-CD16 Fv had growth inhibitory activity, we designed a humanized anti-CD16 Fv to construct the fully humanized Ex16 (hEx16). However, the humanized form had lower activity for inhibition of cancer growth. To restore its growth inhibitory activity, we introduced mutations into the Vernier zone, which is located near the complementarity-determining regions and is involved in their binding activity. We efficiently prepared 15 different hEx16 mutants by expressing each chimeric single-chain component for hEx16 separately. We then used our in vitro refolding system to select the most functional mutant, which had a growth inhibitory effect comparable with that of the commercially available chimeric anti-EGFR antibody, cetuximab. Our refolding system could aid in the efficient optimization of other proteins with heterodimeric structure.

Efficient inhibition of human B-cell lymphoma in SCID mice by synergistic antitumor effect of human 4-1BB ligand/anti-CD20 fusion proteins and anti-CD3/anti-CD20 diabodies

Here we constructed and produced a recombinant human 4-1BB ligand (4-1BBL)/anti-CD20 fusion protein and examined its antitumor activity, alone and in combination with an anti-CD3/anti-CD20 bispecific diabody. The 4-1BBL/anti-CD20 fusion protein retained both the costimulatory activity of 4-1BBL on T cells and the tumor targeting ability of CD20 antibody on B cells. The fusion protein bound as efficiently to 4-1BB- and CD20-positive cells as its respective parental antibodies, and was capable of cross-linking human T lymphocytes and CD20-positive tumor cells. Combination treatment with 4-1BBL/anti-CD20 fusion protein and anti-CD3/anti-CD20 diabody led to significantly increased T-cell cytotoxicity to human B-lymphoma cells in vitro and drastically more potent tumor inhibitory activity in vivo in xenografted B-cell lymphoma in severe combined immunodeficiency disease mice. Mechanistic studies revealed that the combination treatment remarkably inhibited apoptosis of human peripheral blood lymphocytes, accompanied by upregulation of Bcl-XL and Bf1-1, perforin and granzyme B mRNA, and increased interleukin-2 production. Taken together, these results suggest that targeted delivery of 4-1BBL to the tumor site, when combined with anti-CD3/anti-CD20 diabody, could strongly potentiate the antitumor activity of the diabody, thus may have significant clinical application in the treatment of human CD20-positive B-cell malignancies.

Highly enhanced cytotoxicity of a dimeric bispecific diabody, the hEx3 tetrabody

We previously reported the utility for cancer immunotherapy of a humanized bispecific diabody (hEx3) that targets epidermal growth factor receptor and CD3. Here, we used dynamic and static light scattering measurements to show that the multimer fraction observed in hEx3 in solution is a monodisperse tetramer. The multimerization into tetramers increased the inhibition of cancer cell growth by the hEx3 diabody. Furthermore, 1:2 stoichiometric binding for both antigens was observed in a thermodynamic analysis, indicating that the tetramer has bivalent binding activity for each target, and the structure may be in a circular configuration, as is the case for the single-chain Fv tetrabody. In addition to enhanced cytotoxicity, the functional affinity and stability of the hEx3 tetrabody were superior to those of the hEx3 diabody. The increase in molecular weight is also expected to improve the pharmacokinetics of the bispecific diabody, making the hEx3 tetrabody attractive as a therapeutic antibody fragment for cancer immunotherapy.

Rituximab-mediated cell signaling and chemo/immuno-sensitization of drug-resistant B-NHL is independent of its Fc functions

PURPOSE

Rituximab [chimeric anti-CD20 monoclonal antibody], alone or combined with chemotherapy, is used in the treatment of non-Hodgkin's lymphoma (NHL). Rituximab binds to CD20 and inhibits intracellular survival/growth pathways leading to chemo/immunosensitization of tumor cells in vitro. The contribution of rituximab Fc-FcR interaction in signaling is not known. This study examined the role of Fc-FcR interactions in rituximab-induced signaling using rituximab (Fab')(2) fragments as well as rituximab devoid of the CH2 Fc-binding domain (CH2(-)).

EXPERIMENTAL DESIGN

Rituximab (CH2(-)) and rituximab (Fab')(2) were tested for their activity on B-NHL cell lines. Cell signaling and sensitization to chemotherapy and immunotherapy were examined. The in vitro studies were validated in mice bearing tumor xenografts.

RESULTS

Although the modified antibodies were defective in antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity functions, they retained all other biological activities such as inhibition of cell proliferation, induction of cell aggregation, and apoptosis induction. In addition, similar to rituximab, the modified antibodies inhibited the activity of cell survival/growth pathways and their associated transcription factors (e.g., NF-kappaB, YY1, SP-1), and signal transducers and activators of transcription 3 (STAT-3), and downregulated the expression of antiapoptotic gene products, such as Bcl-2/Bcl(xl), which regulate drug resistance. The modified antibodies, similar to rituximab, sensitized resistant B-NHL cells to both CDDP and Fas ligand-induced apoptosis. Furthermore, treatment of nude mice bearing Raji tumor cell xenografts with the combination of rituximab (Fab')(2) or rituximab and CDDP resulted in similar and significant inhibition of tumor growth.

CONCLUSION

These findings reveal that rituximab-mediated inhibition of intracellular signaling pathways and leading to chemo/immuno-sensitization of resistant B-NHL is Fc independent.

Bi20 (fBTA05), a novel trifunctional bispecific antibody (anti-CD20 x anti-CD3), mediates efficient killing of B-cell lymphoma cells even with very low CD20 expression levels

Trifunctional bispecific antibodies can efficiently mediate tumor cell killing by redirecting T cells and immune accessory cells to the tumor cell. Here, we describe the new trifunctional antibody, Bi20 (FBTA05, anti-CD20 x anti-CD3), that connects B cells and T cells via its variable regions and recruits FcgammaRI(+) accessory immune cells via its Fc region. Bi20 mediated efficient and specific lysis of B-cell lines and of B cells with low CD20 expression levels that were derived from CLL patients. Remarkably, T-cell activation and tumor cell killing occurred in an entirely autologous setting without additional effector cells in 5 of 8 samples. In comparison, rituximab, a chimeric monoclonal CD20 antibody, demonstrated a significantly lower B-cell eradication rate. Additionally, Bi20, but not rituximab, upregulated the activation markers CD25 and CD69 on both CD4(+) and CD8(+) T cells in the presence of accessory immune cells. CD14(+) accessory cells and the monocyte cell line THP-1 were activated via binding of the Fc region of Bi20, given that T cells were simultaneously engaged by the antibody. Bi20 induced a strong Th1 cytokine pattern characterized by high IFN-gamma and very low IL-4 secretion. In conclusion, Bi20 may offer new immunotherapeutic options for the treatment of B-cell lymphomas.

Humanization of the bispecific epidermal growth factor receptor x CD3 diabody and its efficacy as a potential clinical reagent

PURPOSE

Bispecific antibodies (BsAb) have been exploited as both cancer immunodiagnostics and cancer therapeutics and show promise in clinical trials of cancer imaging and therapy. For development of BsAbs as clinical reagents, we have focused on construction of small recombinant BsAbs, called bispecific diabodies. Here, we constructed and characterized a humanized bispecific diabody.

EXPERIMENTAL DESIGN

We have reported significant antitumor activity of an anti-epidermal growth factor receptor (EGFR) x anti-CD3 bispecific diabody (Ex3) in in vitro cytotoxicity assays and in vivo. We humanized the Ex3 diabody (hEx3) by grafting the complementarity-determining region and compared its biological properties with those of Ex3. We also tested its physiologic stability and ability to alter survival in xenografted mice.

RESULTS

The final yield of hEx3 was 10 times that of Ex3, and refolded hEx3 and Ex3 showed identical binding profiles in EGFR-positive cell lines and EGFR-transfected Chinese hamster ovary cells. hEx3 showed dose-dependent cytotoxicity to EGFR-positive cell lines, which could be specifically inhibited by parental monoclonal antibody IgGs against EGFR or CD3 antigens. The heterodimeric structure was retained in PBS for 6 months, and growth inhibition was maintained after incubation under physiologic conditions. Coadministration of hEx3 with T-LAK cells and interleukin-2 prolonged the survival of nude mice with human colon carcinoma.

CONCLUSIONS

The humanized diabody hEx3 is an attractive molecule for cancer therapy and may provide important insights into the development of EGFR-based cancer-targeting reagents.

Novel antibodies as anticancer agents

In recent years antibodies, whether generated by traditional hybridoma technology or by recombinant DNA strategies, have evolved from Paul Ehrlich's 'magic bullets' to a modern age 'guided missile'. In the recent years of immunologic research, we are witnessing development in the fields of antigen screening and protein engineering in order to create specific anticancer remedies. The developments in the field of recombinant DNA, protein engineering and cancer biology have let us gain insight into many cancer-related mechanisms. Moreover, novel techniques have facilitated tools allowing unique distinction between malignantly transformed cells, and regular ones. This understanding has paved the way for the rational design of a new age of pharmaceuticals: monoclonal antibodies and their fragments. Antibodies can select antigens on both a specific and a high-affinity account, and further implementation of these qualities is used to target cancer cells by specifically identifying exogenous antigens of cancer cell populations. The structure of the antibody provides plasticity resonating from its functional sites. This review will screen some of the many novel antibodies and antibody-based approaches that are being currently developed for clinical applications as the new generation of anticancer agents.

Bispecific Antibodies: Molecules That Enable Novel Therapeutic Strategies

Bispecific antibodies are unique in the sense that they can bind simultaneously two different antigens. This property enables the development of therapeutic strategies that are not possible with conventional monoclonal antibodies. The large panel of imaginative bispecific antibody formats that has been developed reflects the strong interest for these molecules. Although in many cases the manufacturing of clinical grade material remains challenging, several bispecific antibody formats are currently in clinical trials.

Single variable domain-IgG fusion. A novel recombinant approach to Fc domain-containing bispecific antibodies

Both laboratory and early clinical studies to date have demonstrated that bispecific antibodies (BsAb) may have potentially significant application in cancer therapy. The clinical development of BsAb as therapeutics has been hampered, however, by the difficulty in preparing the materials in sufficient quantity and quality by traditional methods. In recent years, a variety of recombinant methods has been developed for efficient production of BsAb, both as antibody fragments and as full-length IgG-like molecules. Here we describe a novel recombinant approach for the production of an Fc domain-containing, IgG-like tetravalent BsAb, with two antigen-binding sites to each of its target antigens, by genetically fusing a single variable domain antibody to the N terminus of the light chain of a functional IgG antibody of different specificity. A model BsAb was constructed using a single variable domain antibody to mouse platelet-derived growth factor receptor alpha and a conventional IgG antibody to mouse vascular endothelial growth factor receptor 2. The BsAb was expressed in mammalian cells and purified to homogeneity by one-step protein A affinity chromatography. Furthermore, the BsAb retains the antigen binding specificity and the receptor neutralizing activity of both of its parent antibodies. This design and expression of Fc domain-containing, IgG-like BsAb should be applicable to the construction of similar BsAb from antibodies recognizing any pair of antigens.

Recombinant approaches to IgG-like bispecific antibodies

One of the major obstacles in the development of bispecific antibodies (BsAb) has been the difficulty of producing the materials in sufficient quality and quantity by traditional technologies, such as the hybrid hybridoma and chemical conjugation methods. In contrast to the rapid and significant progress in the development of recombinant BsAb fragments (such as diabody and tandem single chain Fv), the successful design and production of full length IgG-like BsAb has been limited. Compared to smaller fragments, IgG-like BsAb have long serum half-life and are capable of supporting secondary immune functions, such as antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity. The development of IgG-like BsAb as therapeutic agents will depend heavily on our research progress in the design of recombinant BsAb constructs (or formats) and production efficiency. This review will focus on recent advances in various recombinant approaches to the engineering and production of IgG-like BsAb.

Recombinant bispecific antibodies for cancer therapy

Bispecific antibodies can serve as mediators to retarget effector mechanisms to disease-associated sites. Studies over the past two decades have revealed the potentials but also the limitations of conventional bispecific antibodies. The development of recombinant antibody formats has opened up the possibility of generating bispecific molecules with improved properties. This review summarizes recent developments in the field of recombinant bispecific antibodies and discusses further requirements for clinical development.

Bispecific single-chain diabody-mediated killing of endoglin-positive endothelial cells by cytotoxic T lymphocytes

We present a novel vascular tumor therapy approach based on lysing endothelial cells by cytotoxic T lymphocytes (CTLs). Retargeting of CTLs is achieved by a recombinant bispecific antibody molecule (bispecific single-chain diabody) directed against human endoglin (CD105, EDG) and the T-cell coreceptor CD3 (scDb EDGCD3). Bacterially expressed scDb EDGCD3 was able to bind to endoglin-expressing endothelial cells as well as CD3-expressing T lymphocytes. The single-chain diabody mediated killing of endothelial cells (HUVEC, HMEC) by activated cytotoxic T lymphocytes at picomolar concentrations, and cells not expressing endoglin were not affected. Because endoglin is up-regulated in the vasculature of many solid tumors, this antibody molecule should be capable of lysing tumor endothelial cells and thus destroying the vascular bed of the tumor.

The effect of variable domain orientation and arrangement on the antigen-binding activity of a recombinant human bispecific diabody

In recent years a variety of recombinant methods have been developed for efficient production of bispecific antibodies (BsAb) in various formats. Bispecific diabody (bDAb), a 55-60 kDa molecule comprising two non-covalently associated cross-over single chain Fv (scFv) polypeptides, represents one of the most promising as well the most straightforward approaches to BsAb production. Here we constructed a bDAb, using two human scFv, 11F8 and A12, directed against the epidermal growth factor receptor (EGFR) and the insulin-like growth factor receptor (IGFR), respectively, as the building blocks. A total of 8 scFv and diabody constructs were prepared comprising the same two variable heavy (V(H)) and variable light (V(L)) chain domains but arranged in different orientations. V(H)/V(L) orientation, i.e., V(H)-linker-V(L) or V(L)-linker-V(H), showed significant effects on the expression and antigen-binding activity of scFv and monospecific diabody of both 11F8 and A12. Further, only 2 out of the 4 possible V(H)/V(L) orientations/arrangements in bDAb construction yielded active products that retain binding activity to both EGFR and IGFR. Both active bDAb preparations retained their original antigen-binding activity after incubation at 37 degrees C in mouse serum for up to 7 days, indicating excellent stability of the constructs. Taken together, our results underscore the importance of identifying/selecting optimal V(H)/V(L) orientation/arrangement for efficient production of active bDAb.

Redirected T-cell cytotoxicity to epithelial cell adhesion molecule-overexpressing adenocarcinomas by a novel recombinant antibody, E3Bi, in vitro and in an animal model

BACKGROUND

To redirect cytotoxic T cells to target a broad range of adenocarcinomas, the authors constructed a novel, recombinant, bispecific antibody, E3Bi, directed at the tumor-associated antigen, epithelial cell adhesion molecule (EpCAM), and the CD3 receptor on T cells.

METHODS

T cells were prepared from healthy blood donors. The cytotoxicity of activated T cells (ATC) redirected to tumor cells by E3Bi was measured with in vitro (51)Cr release assays. In vivo studies were performed in a severe combined immunodeficient (SCID)/Beige mouse xenograft model. Tumor-bearing mice were treated with low doses (1 mg/kg) or high doses (10 mg/kg) of E3Bi along with ATC (2 x 10(9) cells/kg), and treatment efficacy was evaluated both by ex vivo tumor cell survival assay after in vivo treatments and by in vivo tumor growth delay studies.

RESULTS

In vitro, targeting the EpCAM-overexpressing human tumor cell lines with E3Bi increased specific cytotoxicity of ATC by > 70% at an effector-to-target ratio of 2.5 (P < 0.001); this cytotoxicity was abolished competitively in the presence of an anti-EpCAM monoclonal antibody. In contrast, E3Bi did not enhance ATC cytotoxicity toward the low EpCAM-expressing tumor cell line. In ex vivo tumor cytotoxicity assays, a significant reduction in tumor cell survival (40% with low-dose E3Bi; 90% with high-dose E3Bi) was observed in E3Bi/ATC-treated mice compared with control mice that were treated with ATC only. In addition, SCID/Beige mice xenografted with LS174T tumors demonstrated a significant tumor growth delay (P = 0.0139) after receiving E3Bi/ATC/interleukin 2 (IL-2) compared with mice that received ATC/IL-2 alone.

CONCLUSIONS

E3Bi specifically and very efficiently redirected T cells to destroy EpCAM-overexpressing tumors both in vitro and in an animal model. These results suggest a therapeutic utility for E3Bi in the treatment of adenocarcinomas.

Cellular immunotherapy after allogeneic stem cell transplantation in hematologic malignancies

PURPOSE OF REVIEW

The chimeric state after allogeneic stem cell transplantation provides an ideal platform for adoptive immunotherapy of hematologic malignancies using donor-derived cells. The present review aims to summarize recent results of the transfusion of donor-derived cells with regard to the diseases treated, the cells used for treatment, and the origin of these cells.

RECENT FINDINGS

The transfusion of donor lymphocytes has been studied widely, not only in patients with recurrent disease, persistent disease, and mixed chimerism but also in a variety of hematologic malignancies. Donors of lymphocytes and hematopoietic stem cells have been HLA-identical siblings, HLA-matched unrelated donors, and HLA-different haploidentical family members. A variety of cells have been used for adoptive immunotherapy, including plain lymphocytes, selected T cells, T cell lines, and T cell clones. The possible therapies have been expanded by natural killer cells and natural killer T cells as well as antibodies directing the effector cells toward the malignancy.

SUMMARY

Adoptive immunotherapy in chimeras has become not only a routine form of treatment of recurrent hematologic malignancy but also a prophylactic measure in high-risk leukemia and lymphoma.

Efficient inhibition of multidrug-resistant human tumors with a recombinant bispecific anti-P-glycoprotein × anti-CD3 diabody

Overexpressing of P-glycoprotein (Pgp) has been shown to be responsible for cancer resistance to multiple chemotherapeutic agents. Immunotherapy with biological agents, such as bispecific antibodies (BsAbs), may represent a promising approach to overcome the emergence of drug resistance. Here we constructed a recombinant BsAb, a diabody, with specificities to both CD3 on human T-lymphocyte and Pgp on cancer cells. The diabody was produced in Escherichia coli in a soluble functional form and purified by an affinity chromatography with a yield of >4 mg/l culture medium in shaker flask. The diabody binds to both CD3 on T-lymphocytes and Pgp on multidrug-resistant (MDR) tumor cells with affinities that are comparable to its respective parental single chain Fv molecules. In the presence of activated human peripheral blood lymphocytes (PBLs), the diabody mediates effectively the lysis of the Pgp-overexpressing human leukemia K562/A02 and epidermoid carcinoma KBv(200) cells, but is much less potent in mediating the lysis of the parent K562 and KB cells. Further, the diabody localized selectively within the K562/A02 xenografts in mice. When combined with activated PBL, the diabody significantly inhibited the growth of K562/A02 and KBv(200), but had no effect on K562 and KB xenografts. In contrast, treatment with doxorubicin, a standard chemotherapeutic agent, only inhibited the growth of K562 and KB, but had no effect on K562/A02 and KBv(200) xenografts. Taken together, our results suggest that the anti-Pgp x anti-CD3 diabody may have a great potential in the treatment of various MDR cancers.

Recombinant antibodies for cancer diagnosis and therapy

Recombinant antibodies currently represent over 30% of biopharmaceuticals in clinical trials, highlighted by the recent Food and Drug Administration (FDA) approvals of Zevalin(TM) (ibritumomab-tiuxetan; IDEC Pharmaceuticals, San Dieago, CA, USA) for cancer radioimmunotherapy and Humira(TM) (adalimumab; Abbott Laboratories, IL, USA) for rheumatoid arthritis. Together, these FDA approvals have excited the biotechnology industry, particularly since sales of recombinant antibodies are increasing rapidly to a predicted US dollar 4 billion per annum worldwide in 2003. To date, 10 engineered therapeutic antibodies have gained FDA approval and many others are in Phase III trials. Many recent FDA-approved antibodies are simple molecular designs that have taken 10 years to be developed into effective therapeutic reagents. Emerging new technologies have created a vast range of recombinant, antibody-based reagents, which specifically target clinical biomarkers of disease. Radiolabelling of antibodies has increased their potential for cancer imaging and targeting. Recombinant antibodies have also been reduced in size and rebuilt into multivalent molecules for higher affinity. In addition, antibodies have been fused with many molecules, including toxins, enzymes, drugs and viruses, for prodrug therapy, cancer treatment and gene delivery. Recombinant antibody technology has enabled clever manipulations in the construction of complex in vitro libraries for the selection of high-affinity reagents against refractory targets. Furthermore, innovative affinity maturation methods have been developed which enable rapid selection of extremely high-affinity reagents. This review focuses on developments in the last 12 months and describes the latest developments in the design, production and clinical use of recombinant antibodies for cancer diagnosis and therapy.