Mersana Therapeutics (MRSN) Guggenheim SMID Cap Biotech Conference summary

Innovation and differentiation in ADC development

• Focus on novel scaffold linker payloads to minimize off-target toxicities like neutropenia and neuropathy, aiming for a more targeted approach in ADC therapies.

• Lead candidate targets B7-H4, with engineered improvements over existing platforms, eliminating key dose-limiting toxicities.

• Demonstrated efficacy in tumor types and patient settings where competitors face limitations due to cross-resistance or toxicity.

• Recent competitor withdrawals and study design changes have positioned the program as the most advanced auristatin ADC in the B7-H4 space.

Clinical data and efficacy highlights

• Phase I study included 130 patients, exploring a wide range of doses and schedules to optimize safety and efficacy.

• Achieved 23% confirmed response rate in B7-H4 positive patients across all tumor types and in TNBC post-topo, compared to 5% for chemotherapy.

• Most activity observed in B7-H4 positive patients, representing 40-50% of the population.

• Higher doses showed initial evidence of response but lacked confirmation; focus remains on intermediate dose expansion.

Safety profile and dose management

• Successfully eliminated neutropenia, neuropathy, and ocular toxicity at intermediate doses; reversible grade 3 AST elevations observed at highest doses.

• Albuminuria noted at higher doses, attributed to reversible podocytopathy without significant renal impairment or severe hypoalbuminemia.

• Protocol amended to allow treatment through albuminuria, aiming to maintain dose intensity.