Keros Therapeutics, Inc. (KROS) Halts PAH Drug Development After Safety Concerns in TROPOS Trial

Keros Therapeutics, Inc. (NASDAQ:KROS) has announced it will discontinue all development of cibotercept (KER-012) for pulmonary arterial hypertension (PAH) after topline data from the TROPOS Phase 2 trial revealed significant safety concerns.

The trial was halted early following a dose-dependent increase in pericardial effusions, a serious cardiac side effect, particularly at higher doses of 3.0 mg/kg and 4.5 mg/kg. In January 2025, all dosing, including lower-dose and placebo arms, was stopped as new adverse events emerged during ongoing safety reviews. The incidence and severity of pericardial effusions in the cibotercept arms exceeded those seen in placebo and were notably higher than rates reported in comparable studies of MRK’s Winrevair (sotatercept).

A picture of a pharma technician preparing an IV injection of a biopharmaceutical product.

Efficacy outcomes were also disappointing, with no clinically meaningful improvements observed in pulmonary vascular resistance or six-minute walk distance. No major safety signals for other adverse events, such as hemoglobin changes or bleeding, were detected. Due to the early termination, interpretation of the 24-week data is limited.

In response, Keros Therapeutics, Inc. (NASDAQ:KROS) will reduce its workforce by about 45%, leaving 85 full-time employees and aiming for $17 million in annualized cost savings.

Keros Therapeutics, Inc. (NASDAQ:KROS) will now explore strategic alternatives and reassess cibotercept’s potential in other indications.

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Disclosure: None.