Keros’ stock plummeted more than 70% premarket Thursday and Truist Securities analysts predict it will remain under pressure until the safety concerns for cibotercept are resolved.
A week after signing a big deal with Takeda, Keros Therapeutics on Thursday ran into a safety roadblock in the development of its hypertension drug candidate cibotercept.
Keros is currently running the Phase II TROPOS trial for cibotercept, a modified activin receptor fusion protein the biotech is advancing for pulmonary arterial hypertension (PAH). TROPOS is testing three dose levels of cibotercept—1.5 mg/kg, 3 mg/kg and 4.5 mg/kg—in adult patients who are on background therapy.
On Thursday, however, Keros reported that it had detected “unanticipated” cases of pericardial effusion in the study, a complication that is characterized as the abnormal accumulation of fluid around the heart. If it becomes excessive, the fluid build-up can interrupt with the normal beating of the heart. It is yet unclear if the instances of pericardial effusion are linked to the study drug.
Because of this safety signal, Keros has suspended dosing in the 3-mg/kg and 4.5-mg/kg dose arms of the TROPOS trial. Meanwhile, in consultation with an independent data monitoring committee, the biotech will continue treating patients in the 1.5-mg/kg group and will continue to collect safety and efficacy data from all treatment arms in the trial. TROPOS is fully enrolled.
Keros is down more than 70% in pre-market trading Thursday at $19.40, from $68.65 at Wednesday’s close.
“Patient safety is our top priority,” CEO Jasbir Seehra said in a statement, adding that the biotech is “working diligently to gain a better understanding of these unanticipated findings.” Keros has already informed study investigators and the FDA regarding the safety findings.
In a flash note to investors, Truist Securities analysts said they expect Keros’ stock to be “under pressure until the safety concerns are resolved, and we see data in 2Q2025.”
Thursday’s news comes after Keros received $200 million upfront from Takeda last week in return for the worldwide right to develop, manufacture and commercialize elritercept, an investigational activin inhibitor being trialed for anemia in blood cancers. Under this deal, Keros is also entitled to receive up to $1.1 billion in milestones, plus tiered net royalties.
Elritercept is currently in Phase II development for myelofibrosis and in very low-, low-, or intermediate-risk myelodysplastic syndromes (MDS). According to a federal clinical trials database, a Phase III study for elritercept in MDS is set to begin by the end of the year.
“Following the recent partnership for elritercept with Takeda, the PAH program was [Keros’] lead program and also where majority of the value seems to be reflected,” the Truist analysts wrote. Keros expects a topline readout from TROPOS in the second quarter of 2025.
