M3T01 (anti-FasL) Shows 60% Stable Disease and Clean Early Safety in Refractory Solid Tumors

M3T01 is a fully human IgG4/kappa monoclonal antibody that blocks Fas ligand (FasL), aiming to prevent FasL-mediated apoptosis of tumor-reactive T cells and potentially improve intratumoral T-cell infiltration. In an ongoing first-in-human Phase I 3+3 dose-escalation trial in unresectable/metastatic treatment-refractory solid tumors (NCT06719362), 10 patients have been treated (100–400mg IV q3w) as monotherapy: any-grade TRAEs occurred in 50% with one Grade 3 immune thrombocytopenia (10%), no Grade 4–5 TRAEs, no discontinuations, no DLTs, and MTD not reached; PK appeared ~dose-proportional and transient ADA had no exposure impact. Best response was stable disease in 6/10 (60%) with tumor regression noted in 3/10 (30%) (including shrinkage of some liver metastases in refractory GEJ adenocarcinoma), but no confirmed PR/CR reported so far—broadly in line with what you’d expect from many early, unselected IO-enabled Phase I monotherapy datasets where objective responses are often infrequent unless a biomarker-selected or highly IO-sensitive subset is enriched.