Keros Therapeutics has halted dosing in two of the three treatment arms of a phase 2 trial of its pulmonary arterial hypertension (PAH) drug after receiving reports of fluid buildups around the heart.
The Lexington, Massachusetts-based biotech had been testing 1.5-mg/kg, 3-mg/kg and 4.5-mg/kg doses of the TGF-β inhibitor, called cibotercept, in the phase 2 TROPOS study. However, the biotech has voluntarily halted the two higher dose cohorts “based on a safety review due to the unanticipated observation of pericardial effusion adverse events in the trial.”
Pericardial effusion refers to an excessive buildup of fluid in the sac surrounding the heart, which is called the pericardium. The condition has a number of typical potential causes, including infection and injury.
The decision to continue with the 1.5-mg/kg dose cohort was made in consultation with the trial’s independent data monitoring committee, which completed a risk and benefit assessment of data from the fully enrolled trial, Keros said in a Dec. 12 release.
The biotech has notified the FDA and other regulators and is sticking with its plan to present top-line data from all three dose cohorts in the second quarter of 2025.
“We are working diligently to gain a better understanding of these unanticipated findings,” Keros CEO Jasbir Seehra, Ph.D., said in the release. “Above all, patient safety is our top priority when conducting any clinical trial. We will work with the investigators, the FDA and other relevant regulatory authorities to address this as quickly as possible.”
The company’s shares plunged 65% to $24.24 in premarket trading Thursday from a Friday closing price of $68.65.
Today’s news comes a week after Keros secured $200 million in upfront cash from Takeda for the ex-China rights to an activin inhibitor called elritercept that could potentially compete with Bristol Myers Squibb’s Reblozyl in blood cancer indications.