Molecular Templates Announces FDA Acceptance of IND Application for a PD-L1-Targeted Engineered Toxin Body Enabled With Proprietary Antigen Seeding Technology

Molecular Templates, Inc. recently announced the US FDA has accepted its Investigational New Drug (IND) application for MT-6402, a next-generation ETB targeting PD-L1 that is enabled with MTEM’s antigen seeding technology (AST). ETBs enabled with AST have dual mechanisms of action that include the enzymatic destruction of ribosomes and the delivery of viral class I antigens into the targeted tumor to be processed and presented on its cell surface to induce an antigen specific immune response. MTEM expects to start dosing enrolled subjects in a first-in-human Phase 1 study in relapsed/refractory patients with PD-L1-positive solid tumors in 2Q21.

The Phase 1 study is planned as a multi-center, open-label, dose escalation and dose expansion trial in the US and outside of the US. Patients with confirmed PD-L1 expressing tumors or confirmed PD-L1 expression in the tumor microenvironment will be eligible to screen for enrollment in the clinical trial. Following determination of the maximum tolerated dose (MTD) or recommended Phase 2 dose, expansion cohorts are planned to study MT-6402 as a monotherapy in tumor-specific and tumor-agnostic cohorts.

“We are excited to be advancing MT-6402, a third generation ETB, into the clinic for the treatment of patients with PD-L1-positive cancers. MT-6402 utilizes both our proprietary de-immunized toxin scaffold and antigen seeding technology,” said Eric Poma, PhD, CEO and CSO of Molecular Templates. “The PD-1/PD-L1 axis is central to many tumors and targeting that axis with a new mechanism of action has an opportunity to provide meaningful benefit to patients. We look forward to providing an update on the Phase 1 study by year-end 2021.”

MT-6402 is an ETB consisting of a single chain variable fragment (scFv) with affinity for PD-L1, fused to the enzymatically active de-immunized Shiga-like toxin-A subunit (SLTA) and a class I antigen derived from the human cytomegalovirus (HCMV) pp65 protein. MT-6402 was designed to induce potent anti-tumor effects via PD-L1 targeting through multiple mechanisms that may overcome the limitations of the PD-L1 antibodies. In MTEM’s preclinical studies, MT-6402 was found to specifically bind and kill both tumor and immune PD-L1 expressing cells in a manner consistent with SLTA mediated cellular cytotoxicity through ribosomal inactivation, independent of checkpoint inhibition. Additionally, MT-6402 alters the immunophenotype of targeted cells by delivering foreign class I antigen from CMV for presentation in complex with MHC class I, which may provoke a CMV-specific immune response against the targeted cells. Third, MT-6402 may rehabilitate the tumor microenvironment (TME) and allow for immune recognition of tumors by destroying PD-L1-expressing immune cells in the TME through ribosomal inactivation.

Molecular Templates is a clinical-stage company focused on the discovery and development of targeted biologic therapeutics. Our proprietary drug platform technology, known as engineered toxin bodies, or ETBs, leverages the resident biology of a genetically engineered form of Shiga-like Toxin A subunit to create novel therapies with potent and differentiated mechanisms of action for cancer and other serious diseases.