On Thursday, Keros Therapeutics, Inc. ( KROS ) voluntarily halted dosing in the 3.0 mg/kg and 4.5 mg/kg treatment arms in the ongoing TROPOS trial Phase 2 trial of cibotercept (KER-012) in combination with background therapy in pulmonary arterial hypertension patients.

The move is based on a safety review, as the trial unanticipatedly observed adverse pericardial effusion events.

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Pericardial effusion is when too much fluid builds up in the sac around the heart, called the pericardium. This fluid can pressure the heart, making it difficult to function properly.

The TROPOS trial is fully enrolled, and dosing in the 1.5 mg/kg treatment arm remains ongoing following completion of a risk and benefit assessment of the data from the ongoing trial that was conducted by the independent Data Monitoring Committee (DMC) followed by a select group of unblinded individuals at Keros.

The decision to halt the dosing in 3.0 mg/kg and 4.5 mg/kg treatment arms and continue dosing in the 1.5 mg/kg treatment arm was made in consultation with the independent DMC for the trial.

The company intends to continue ongoing safety and efficacy data collection for all treatment arms in the trial.

The company continues to expect to present topline data from all treatment arms in this trial in the second quarter of 2025.

Price Action: KROS stock is down 74.1% at $17.80 during the premarket session at last check Thursday.

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