OMass Secures $310 Million Series C, Backing CAH Drug Into Phase 2

OMass Therapeutics has raised $310 million in a Series C round to support a pipeline led by OMS1620, a small molecule in development for congenital adrenal hyperplasia, or CAH. The company said the new capital will fund plans to take OMS1620 through Phase 2 testing in CAH and ACTH-dependent Cushing's syndrome, while also supporting earlier-stage assets.

That is a large financing for a private company built around a rare-disease endocrine program, but the size reflects more than a single asset. It gives OMass room to fund a clinical read on its lead program while keeping other platform-derived programs moving, a structure that can matter in markets where investors have become more selective about single-asset risk.

The clinical strategy

CAH is an inherited disorder in which patients lack an enzyme the adrenal glands need to produce key hormones. The resulting hormonal imbalance can lead to low levels of sodium affecting the brain and kidneys, as well as dehydration and adrenal crisis, a life-threatening complication tied to lack of the hormone cortisol from the adrenal glands.

Standard treatment for CAH is high doses of glucocorticoids, which are synthetic versions of cortisol. The source notes that those required high doses introduce a range of side effects, which is the opening OMass is targeting with OMS1620.

OMS1620 is designed to block the melanocortin-2, or MC2, receptor in the adrenal glands. OMass says that approach is intended to decrease the production of hormones that drive the hormonal imbalance in CAH. The company also says the drug is designed to stay bound to the target receptor longer and maintain activity in the presence of rising hormone levels that stimulate adrenal glands to produce more cortisol. According to OMass, those properties could allow more CAH patients to reach hormone levels closer to normal while taking glucocorticoids.

The strategic distinction is important because OMass is not entering an untouched market. It is arguing that receptor-level control in the adrenal gland could offer a differentiated way to manage the disease burden created by current therapy, rather than simply adding another version of the same mechanism.

The commercial picture

The only currently available CAH drug cited in the source is Crenessity, a Neurocrine Biosciences product approved by the FDA in 2024. That oral small molecule is designed to block CRFR1 to inhibit the pituitary gland's secretion of adrenocorticotropic hormone, or ACTH, which in turn reduces production of other hormones involved in the hormonal imbalance in CAH.

Neurocrine reported $301.2 million in 2025 sales for Crenessity. That figure gives OMass investors a concrete commercial reference point: CAH may be a rare disease, but the market has already shown it can support meaningful revenue for an oral small molecule with a clear role in treatment.

Competition is also building. Vertex Pharmaceuticals is pursuing the same market with atumelnant, described in the source as a small molecule inhibitor of ACTH that came through Vertex's recently closed $10 billion acquisition of Crinetics Pharmaceuticals. For OMass, that means the path forward depends not just on proving OMS1620 works, but on showing why an MC2 receptor blocker should occupy a distinct position against both a marketed CRFR1 blocker and an ACTH-focused competitor.

The financing and what it signals

The Series C was announced on Oct. 15 and was co-led by new investors Bain Capital Life Sciences, Forbion, and Novo Holdings. Other participants were Janus Henderson Investors, SV Health Investors, Jefferson Life Sciences, and existing backers Syncona, Oxford Science Enterprises, GV, Northpond Ventures, Sanofi Ventures, British Business Bank, and University of Oxford.

Beyond OMS1620, OMass said the financing will support earlier-stage assets, including a potential first-in-class SLC15A4 inhibitor in development for lupus and other diseases associated with interferon overproduction and pathogenic B-cell activation.

The broader signal is that investors are still willing to commit very large sums where a company can pair a clinically defined lead program with a mechanism-based pipeline. In CAH specifically, OMass is raising into a category that already has one FDA-approved drug and another serious entrant, which suggests backers believe differentiation by target biology may still create room for another contender rather than shutting the window after the first approval.