Synthesis and Biological Evaluation of a Carbamate-Containing Tubulysin Antibody-Drug Conjugate.

Antibody-drug conjugates (ADCs) use antibodies to deliver cytotoxic payloads directly into tumor cells via specifically binding to the target cell surface antigens. ADCs can enhance the anti-tumor effects of antibodies, and increase the delivery of cytotoxic payloads to cancer cells with a better therapeutic index. An ADC was prepared with a potent carbamate-containing tubulysin analogue attached to an anti-mesothelin antibody via a Cit-Val dipeptide linker. An aniline functionality in the tubulysin analogue was created to provide a site of linker attachment via an amide bond that would be stable in systemic circulation. Upon ADC internalization into antigen-positive cancer cells, the Cit-Val dipeptide linker was cleaved by lysosomal proteases, and the drug was released inside the tumor cells. The naturally occurring acetate of tubulysin was modified to a carbamate to reduce acetate hydrolysis of the ADC in circulation and to increase the hydrophilicity of the drug. The ADC bearing the monoclonal anti-mesothelin antibody and the carbamate-containing tubulysin was highly potent and immunologically specific to H226 human lung carcinoma cells in vitro, and efficacious at well-tolerated doses in a mesothelin-positive OVCAR3 ovarian cancer xenograft mouse model.

BMS-936564/MDX-1338: a fully human anti-CXCR4 antibody induces apoptosis in vitro and shows antitumor activity in vivo in hematologic malignancies.

PURPOSE: CXCR4 has been identified as a prognostic marker for acute myeloid leukemia (AML) and other malignancies. We describe the development and characterization of a fully human antibody to CXCR4 and its application for therapy of AML, non-Hodgkin lymphoma (NHL), chronic lymphoid leukemia (CLL), and multiple myeloma. EXPERIMENTAL DESIGN: Human transgenic mice were immunized with CXCR4-expressing cells, and antibodies reactive with CXCR4 were analyzed for apoptosis induction and ability to interfere with CXCL12-induced migration and calcium flux. In vivo efficacy was determined in multiple AML, NHL, and multiple myeloma xenograft tumors in severe combined immunodeficient mice. RESULTS: BMS-936564/MDX-1338 is a fully human IgG(4) monoclonal antibody that specifically recognizes human CXCR4. In vitro studies show that MDX-1338 binds to CXCR4-expressing cells with low nanomolar affinity, blocks CXCL12 binding to CXCR4-expressing cells, and inhibits CXCL12-induced migration and calcium flux with low nanomolar EC(50) values. When given as monotherapy, MDX-1338 exhibits antitumor activity in established tumors including AML, NHL, and multiple myeloma xenograft models. In addition, we show that MDX-1338 induced apoptosis on a panel of cell lines and propose that antibody-induced apoptosis is one of the mechanisms of tumor growth inhibition. CONCLUSIONS: BMS-936564/MDX-1338 is a potent CXCR4 antagonist which is efficacious as monotherapy in tumor-bearing mice and is currently in phase I for the treatment of relapsed/refractory AML, NHL, CLL, and multiple myeloma.