Abstract 2659: MT-4019: a de-immunized engineered toxin body targeting CD38 for multiple myeloma
Authors: Robinson Garrett L. , Rajagopalan Sangeetha , Brieschke Brigitte , Neill Jane , Erdman Jennifer , Flores Rodney , Liu Jensing , Higgins Jack P. , Willert Erin K. 
Published: July 2017

Abstract
Molecular Templates is developing engineered toxin bodies (ETBs), potent recombinant immunotoxins that combine the specificity of an antibody fragment with the powerful direct cytotoxicity of the Shiga-like toxin A subunit (SLTA). ETBs can induce their own internalization, route through the cell in a predictable manner, enzymatically and irreversibly destroy ribosomes to shutdown protein synthesis and induce apoptosis of tumor cells. This mechanism of action is distinct from that of other therapeutics, making ETBs an attractive treatment for patients who have become resistant to chemotherapy and other treatments. Safety and efficacy in refractory non-Hodgkin’s lymphoma patients has been observed in a phase I study with Molecular Template’s first-generation CD20-targeting compound, MT-3724.
CD38 is a surface receptor that is highly expressed on malignant plasma cells. CD38 is a clinically validated target of monoclonal antibodies for treatment of multiple myeloma and is known to persist after failure of antibody treatment. MT-4019 is a CD38-targeted next-generation ETB, utilizing a modified SLTA. The SLTA subunit of the next-generation ETB scaffold has been modified through proprietary genetic engineering to systematically and comprehensively reduce B cell and CD4+T cell epitopes, as well as to dampen the innate response by decreasing binding to TLR-4. This de-immunized next-generation scaffold retains the potency and specificity of an ETB containing an unmodified SLTA. Pre-clinical studies in rodents and non-human primate models have demonstrated the tolerability of MT-4019, along with a decreased anti-drug antibody response. Additionally, in the non-human primate model, MT-4019 showed reduced neutrophil and monocyte activation as compared to an ETB with an unmodified SLTA subunit, indicating that SLTA modification also exhibits a diminished innate immune response.
Molecular Template’s ETB technology has resulted in potent, targeted therapeutic agents that have a unique mechanism of action in the field of oncology. MT-3724, a first-generation CD20-targeted ETB, has shown promising clinical results in the refractory setting for non-Hodgkin’s lymphoma. The next-generation scaffold, as exemplified in the CD38-targeted MT-4019, retains potent and specific direct cell kill activities, and additionally reduces the innate and adaptive immune response to the therapeutic. MT-4019 is a promising lead and is under further development to enable clinical studies in multiple myeloma.
Citation Format: Garrett L. Robinson, Sangeetha Rajagopalan, Brigitte Brieschke, Jane Neill, Jennifer Erdman, Rodney Flores, Jensing Liu, Jack P. Higgins, Erin K. Willert. MT-4019: a de-immunized engineered toxin body targeting CD38 for multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2659. doi:10.1158/1538-7445.AM2017-2659