Molecular Templates, Inc. announced that it has received clearance by the United States Food and Drug Administration (FDA) following review of its Investigational New Drug Application (IND) to proceed for clinical testing of its novel MT-8421 ETB program targeting CTLA-4 in patients with relapsed/refractory solid tumors previously exposed to checkpoint inhibitors. Preclinical data from MT-8421 showed that in a transgenic mouse model expressing human CTLA-4 and bearing syngeneic subcutaneous tumors, MT-8421 treatment depleted immune suppressive Tregs in the TME but not in the periphery. MT-8421 was well tolerated in a non-human GLP primate toxicology study and achieved serum levels well-above projected IC50 concentrations for Tregs in the TME.

MTEM expects to initiate a first-in-human phase I study with MT-8421 by mid-year 2023 at a starting dose of 32 mcg/kg.