OMass Therapeutics raised an oversubscribed $310 million Series C round to advance its endocrinology and immunology pipeline toward later-stage development. The financing will primarily support OMS1620, a melanocortin-2 (MC2) receptor antagonist being studied for congenital adrenal hyperplasia (CAH) and ACTH-dependent Cushing’s syndrome. Company plans also include early clinical work on an additional candidate, SLC15A4, aimed at lupus and other interferon-linked conditions. OMass said the program approach for OMS1620 is designed to extend receptor residency time to sustain activity as endogenous ACTH rises—targeting androgen normalization for more CAH patients while remaining on physiologic glucocorticoid dosing. The round was co-led by Bain Capital Life Sciences, Forbion, and Novo Holdings, with additional new participation from Janus Henderson Investors, SV Health Investors, and Jefferson Life Sciences. Existing backers—including Syncona, Oxford Science Enterprises, GV, Northpond Ventures, and Sanofi Ventures—also took part. For investors and rare disease developers, the funding is notable both for the ticket size and for backing a receptor-residency strategy in endocrinology—an area that has seen mounting demand for durable disease control with fewer dosing complications.