M1231

M1231 is a first-in-class bispecific antibody-drug conjugate (ADC) designed to target two cancer-associated antigens—mucin 1 (MUC1) and epidermal growth factor receptor (EGFR)—which are frequently overexpressed in various solid tumors. The drug consists of a bispecific antibody that binds both MUC1 and EGFR on tumor cells and is conjugated to a cytotoxic payload related to hemiasterlin, which acts as a microtubule inhibitor. Upon binding to its targets on the tumor cell surface, the ADC is internalized and releases its cytotoxic agent inside the cell, leading to disruption of microtubules and subsequent cell death. Developed using Sutro Biopharma’s XpressCF+ technology in collaboration with Merck KGaA (EMD Serono), this therapy aimed for increased selectivity by requiring co-expression of both antigens for optimal activity. Clinical development was focused on advanced solid tumors including non-small cell lung cancer and esophageal cancer.