Antibody-based therapy has revitalized the world of cancer therapeutics since rituximab was first approved for the treatment of Non-Hodgkin’s Lymphoma. Monoclonal antibodies against cancer antigens have been successful strategies for only a handful of cancer types due to many reasons including lack of antibody specificity and complex nature of tumor milieu which interfere with antibody efficacy. Polyspecific antibodies are promising class of anti-cancer agents which can be directed at multiple tumor antigens to eradicate tumor cells more precisely and effectively. They may overcome some of these limitations and have already changed treatment landscape for some malignancies such as B cell acute lymphoblastic leukemia. Pre-clinical studies and early phase clinical trials have demonstrated that this approach may be an effective strategy even for solid tumors. This review focuses on the development of bispecific and trispecific antibody therapy for the treatment of solid tumor malignancies and highlights the potential they hold for future therapies to come.

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Trastuzumab is a monoclonal antibody targeted against the HER2 tyrosine kinase receptor. Although trastuzumab is a very active agent in HER2-overexpressing breast cancer, the majority of patients with metastatic HER2-overexpressing breast cancer who initially respond to trastuzumab develop resistance within 1 year of initiation of treatment and, in the adjuvant setting, progress despite trastuzumab-based therapy. The antibody-drug conjugate trastuzumab-DM1 (T-DM1) was designed to combine the biological activity of trastuzumab with the targeted delivery of a highly potent antimicrotubule agent, DM1 (N-methyl-N-[3-mercapto-1-oxopropyl]-l-alanine ester of maytansinol), a maytansine derivative, to HER2-overexpressing breast cancer cells. T-DM1 is the first antibody-drug conjugate with a nonreducible thioether linker in clinical trials. Phase I and II clinical trials of T-DM1 as a single agent and in combination with paclitaxel, docetaxel and pertuzumab have shown clinical activity and a favorable safety profile in patients with HER2-positive metastatic breast cancer. Two randomized phase III trials of T-DM1 are awaiting final results; the EMILIA trial is evaluating T-DM1 compared with lapatinib plus capecitabine, and early positive results have been reported. The MARIANNE trial is evaluating T-DM1 plus placebo versus T-DM1 plus pertuzumab versus trastuzumab plus a taxane. Here, we summarize evidence from clinical studies and discuss the potential clinical implications of T-DM1.

Although platinum based therapy has improved short term survival of patients with metastatic ovarian cancer, the majority of patients continue to relapse and eventually die of their disease. Currently, a plethora of agents are in development, but how to combine them to enhance efficacy remains largely empiric. We have used short in vitro culture of defined cell lines with application of promising agents and analysis for cell death using a MTT assay to identify potentially useful combinations. Using median effect analysis, curve shift analysis and apoptosis assays, we can identify when agents are synergistic or antagonistic when applied together. Up to three agents can be studied in combination. Using three cell lines: SK-OV3, CaOV-3, and ES-2 (a clear cell tumor), we have identified that panobinostat (LBH-589), a broad histone deacetylase inhibitor in clinical trials, demonstrates global synergy with gemcitabine, with paclitaxel, and additive to synergistic effects with 5'DFUR. The triplet of panobinostat, doxorubicin, and carboplatin is especially synergistic in these cell lines. These effects are cytotoxic and not cytostatic. As all these agents are used clinically, we have identified combinations which warrant further investigation.