PF-08046876, a differentiated integrin beta-6 antibody-drug conjugate delivering a potent camptothecin payload optimized for bystander effect and reduced drug efflux

Integrins represent a large family of cell surface receptors that exist as heterodimers with essential roles in key biological processes such as cellular adhesion, motility, and cytokinesis. Among them, integrin beta-6 (IB6), which exclusively dimerizes with integrin alpha-v, has emerged as a clinically relevant target due to its restricted expression in normal adult epithelial tissues and elevated levels in solid tumors. High expression of IB6 is correlated with poor prognosis across multiple solid tumor types. PF-08046876 is an investigational antibody-drug conjugate (ADC) consisting of the anti-IB6 monoclonal antibody conjugated to a camptothecin-class topoisomerase I (TOP1) inhibitor, AMDCPT, using a traceless enzyme-cleavable glucuronide linker. The AMDCPT payload has been optimized for differentiation from other TOP1 inhibitors with improved potency, enhanced bystander activity, and reduced susceptibility to multidrug resistance (MDR) efflux mechanisms. PF-08046876 leverages the same antibody backbone from sigvotatug vedotin (SV) and binds IB6 without cross-reactivity to other alpha-v integrin complexes. In preclinical studies, PF-08046876 has demonstrated significant antitumor activity both in vitro and in vivo across multiple tumor models with IB6 expression, including non-small cell lung (NSCLC), head and neck squamous cell (HNSCC), urothelial (UC), pancreatic (PDAC), and esophageal (ESCA) carcinomas. These findings support further clinical development of PF-08046876 as a promising therapeutic candidate for the treatment of IB6-expressing solid tumors.