Keros Therapeutics Inc ( KROS ) released topline data from the TROPOS Phase 2 trial of cibotercept (KER-012) in combination with background therapy in patients with pulmonary arterial hypertension (PAH) on Wednesday.

In December 2024, the company voluntarily halted the 3.0 mg/kg and 4.5 mg/kg treatment arms based on observing pericardial effusions at those dose levels.

Furthermore, in January 2025, the company halted all dosing in the trial, including the 1.5 mg/kg and placebo treatment arms, based on the ongoing safety review due to new observations of pericardial effusion adverse events.

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Following the early termination of the trial, patients continued to be monitored through their end-of-trial visits.

Following the analysis of all available safety and efficacy data from the TROPOS trial, the company has decided to discontinue all development of cibotercept in PAH.

In a corporate presentation, the company noted a higher incidence in cibotercept arms relative to placebo and a higher incidence rate and severity in the 3.0 and 4.5 mg/kg arms than the 1.5 mg/kg arm.

The background rate of pericardial effusions in this trial was higher than in randomized, controlled trials of Merck & Company, Inc.’s Winrevair (sotatercept).

Keros said the ability to interpret 24-week data is limited due to incomplete treatment duration and trial visit participation.

A dose-dependent signal for pericardial effusions was observed for cibotercept in this PAH population.

During the treatment duration in the analysis from this data cutoff, no major signal for hemoglobin increases, thrombocytopenia, bleeding events, or telangiectasias was observed relative to the placebo.

No clinically meaningful improvement in pulmonary vascular resistance (PVR) or 6-minute walk distance (6MWD) was observed.

The company plans to further evaluate the appropriate development strategy for cibotercept, if any, in other indications following the completion of the strategic alternative review process.

Keros has decided to reduce the company’s headcount by approximately 45%, after which the company will have 85 full-time employees. The company expects to realize average annualized cost savings of approximately $17 million.

Price Action: KROS stock is trading lower by 4.78% to $13.94 at last check Thursday.

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