Mersana Therapeutics: Emi-Le Expansion Data Expected in H2 2025, $15M GSK Milestone Achieved

Mersana Therapeutics expects to report initial expansion data for Emi-Le in H2 2025. The company has achieved a $15M milestone with GSK. Emi-Le is a Dolasynthen ADC targeting B7-H4, with recent oral presentations at ASCO 2025 and ESMO Breast Cancer 2025. Enrollment in expansion cohorts is strong.

Mersana Therapeutics, Inc. (MRSN) expects to report initial expansion data for its Dolasynthen ADC, Emi-Le, in the second half of 2025. The company has recently achieved a $15 million milestone with GlaxoSmithKline (GSK) [1]. Emi-Le is designed to target B7-H4 and has shown encouraging clinical activity in patients with triple-negative breast cancer (TNBC) post-topoisomerase-1 inhibitor treatment and those with adenoid cystic carcinoma type 1 (ACC-1). The company presented Emi-Le data at the American Society of Clinical Oncology (ASCO) 2025 and the European Society for Medical Oncology (ESMO) Breast Cancer 2025 conferences [2].

Enrollment in Emi-Le's Phase 1 dose expansion cohorts remains strong, with over 45 patients enrolled across two dosing regimens. The company is on track to report initial clinical data from these expansion cohorts later this year. Martin H. Huber, President, CEO, and Director of Mersana, highlighted the progress made in enrolling patients and the company's focus on TNBC patients who have previously received a topo-1 ADC [1].

The company's financial results for the second quarter of 2025 included a $77 million cash position and net cash used in operating activities of $22.6 million. Collaboration revenue for the quarter was $3.1 million, reflecting higher revenue from Johnson & Johnson (J&J) and Merck KGaA collaborations, partially offset by reduced revenue from GSK. Research and development expenses were $16.2 million, with general and administrative expenses declining to $7.4 million [1].

Mersana's strategic focus remains centered on TNBC and breast cancer, with no new expansion into other tumor types. The company is projecting its capital resources to support its current operating plan commitments into mid-2026, with no assumptions for additional milestone payments or collaboration proceeds. The company noted the evolving treatment landscape in TNBC and the potential for Emi-Le to address a growing post-topo-1 patient population if approved [1].

References:
[1] https://seekingalpha.com/news/4484786-mersana-targets-reporting-initial-emi-le-expansion-data-in-h2-2025-while-achieving-15m-gsk
[2] https://www.biospace.com/press-releases/mersana-therapeutics-provides-business-update-and-announces-second-quarter-2025-financial-results