Development of ZW418, a biparatopic PTK7-targeting antibody-drug conjugate incorporating a novel pan-RAS inhibitor payload for the treatment of non-small cell lung cancer

Mutations in the RAS oncogene family occur in approximately 25-30% of lung adenocarcinomas and represent one of the most common oncogenic drivers in non-small cell lung cancer (NSCLC). These alterations lead to constitutive activation of downstream MAPK signaling, promoting tumor growth and therapeutic resistance. Protein tyrosine kinase 7 (PTK7) is prevalently overexpressed in NSCLC but has limited expression in normal tissue, making it an attractive therapeutic target for NSCLC.   Existing mutant-specific and pan-RAS inhibitors (RASi) have demonstrated clinical benefit in NSCLC but patients often experience on-target off-tumor toxicities and acquire resistance. These challenges may be improved upon by enhancing delivery of a RASi via an antibody drug conjugate (ADC) mechanism. We have developed ZW418, a biparatopic PTK7-targeting ADC  that leverages a cleavable linker designed to deliver a novel pan-RASi payload with optimized stability and bystander effect for the treatment of NSCLC.  A biparatopic antibody recognizing two non-overlapping epitopes on PTK7 was engineered and conjugated to a cleavable pan-RASi drug-linker. Binding affinity, internalization, spheroid penetration, and in vitro cytotoxicity were characterized across a panel of PTK7-expressing RAS-mutated cancer cell lines. Additional mechanistic evaluation of RAS inhibition was also performed in vitro. Pharmacokinetic properties were evaluated in non-tumor bearing mice, and antitumor activity was investigated in RAS-mutated cancer  xenograft models.    Across RAS-mutated cancer cell lines with varying PTK7 expression level, the biparatopic antibody demonstrated greater cell surface decoration, internalization, and spheroid penetration compared to cofetuzumab and other PTK7-targeted clinical benchmark antibodies.  ZW418 exhibited potent target-dependent cytotoxicity in vitro and demonstrated strong anti-tumor activity in multiple RAS-mutated cancer cell line derived xenograft models. The pan-RASi ADC platform showed encouraging tolerability in mice with no significant toxicity observed up to a dose of 200 mg/kg. Overall, the data supports the potential of ZW418 as a novel, highly differentiated therapeutic agent against PTK7-expressing RAS mutant cancers.