Keros Plummets 74% After Unexpected Side Effects 'Shock' Its Lead Drug

Keros Therapeutics (KROS) stock plummeted 74% on Thursday, December 12, 2024, after the company announced it had voluntarily halted dosing in two treatment arms of its Phase 2 TROPOS trial due to unanticipated adverse pericardial effusion events. The setback has raised concerns about the safety and efficacy of the company's lead drug, cibotercept, and its potential to regain investor interest.

The TROPOS trial, a randomized, double-blind, placebo-controlled, global Phase 2 clinical trial, was evaluating cibotercept in combination with background therapy in patients with pulmonary arterial hypertension (PAH). The primary objective of the trial was to evaluate the effect of cibotercept on pulmonary hemodynamics compared to placebo in participants on background PAH therapy. However, the unanticipated observation of pericardial effusion adverse events led to the voluntary halt in dosing for the 3.0 mg/kg and 4.5 mg/kg treatment arms.

Keros Therapeutics, a clinical-stage biopharmaceutical company focused on developing and commercializing novel therapeutics to treat a wide range of patients with disorders linked to dysfunctional signaling of the transforming growth factor-beta (TGF-β) family of proteins, has stated that patient safety is its top priority. The company is working diligently to investigate and address the matter and expects to provide additional information when there is a material update.

The halt in dosing for higher doses of cibotercept has significant implications for the drug's timeline and potential approval. The unanticipated pericardial effusion adverse events have led to a voluntary pause in the 3.0 mg/kg and 4.5 mg/kg treatment arms, while the 1.5 mg/kg arm continues. This setback may delay the presentation of topline data, originally expected in Q2 2025, as the company works to investigate and address the issue. The halt also raises questions about the drug's safety profile and could impact regulatory approval timelines.

Financially, Keros Therapeutics' stock has plummeted 74%, reflecting investor concerns about the drug's future and the company's financial projections. The halt in dosing for higher doses may lead to revised financial projections, potentially impacting the company's market capitalization and valuation.



To regain investor trust and address the safety concerns raised by the unexpected side effects in the TROPOS trial, Keros Therapeutics will need to work diligently to investigate the issue, collaborate with regulators, and continue collecting data from all treatment arms. The company expects to present topline data in the second quarter of 2025, providing a clearer picture of the drug's safety and efficacy. Additionally, Keros will likely enhance its communication strategy to keep investors informed and reassure them of its commitment to patient safety and the development of its lead drug, cibotercept.



In conclusion, the halt in dosing for higher doses of cibotercept in the TROPOS trial has significant implications for the drug's timeline and potential approval, as well as the company's financial projections. Keros Therapeutics will need to address the safety concerns and work to regain investor trust to maintain its position in the biopharmaceutical industry. As the company continues to investigate the issue and collect data, investors will be watching closely to see how the situation unfolds and the potential impact on the company's future prospects.