Keros pulls study of Winrevair rival after safety signal
Keros Therapeutics has abandoned a phase 2 trial of its drug candidate for pulmonary arterial hypertension (PAH), cibotacept, after seeing evidence of potentially serious cardiovascular side effects.
Shares in the company were down nearly 20% in pre-market trading at the time of writing as investors digested the announcement and tried to gauge its significance for the drug, which is a potential rival to MSD's fast-growing PAH therapy Winrevair (sotatercept).
The action affects the TROPOS trial of cibotacept (KER-012), an activin signalling inhibitor that works in a similar way to Winrevair, which was approved last year in the US, becoming the first drug cleared by the FDA thought to address the underlying mechanism behind PAH, rather than its symptoms.
MSD's product has seen rapid take-up since launch, with third-quarter sales reaching $149 million – well ahead of analyst expectations – and putting it on course to meet the company's projections of more than $3 billion in peak annual sales.
In its statement, Keros said that it is voluntarily stopping all dosing in TROPOS "based on the ongoing safety review due to new observations of pericardial effusion," a condition in which excess fluid builds up around the heart. It can lead to serious complications, including compression of the heart chambers, known as cardiac tamponade, that in severe cases can be life-threatening.
The company revealed last month that it had halted two dose cohorts in TROPOS – 3.0mg/kg and 4.5mg/kg – but has now extended that to the remaining 1.5mg/kg arm.
At the time, the company's shares lost more than two-thirds of their value, reversing strong gains made by the stock over the last few months, fuelled by positive results for myelodysplastic syndrome and myelofibrosis therapy elritercept and a $1.1 billion licensing deal for that drug with Takeda.
"While we are disappointed in this new development, patient safety is always our top priority," said the Lexington, Massachusetts biotech's chief executive, Jasbir Seehra.
He added: "We continue to work with the investigators, the […] FDA, and other relevant regulatory authorities, and we look forward to analysing and presenting TROPOS topline clinical data in the future."
Keros noted that patients will be monitored through the end-of-trial visits and it expects to provide topline data from the study in the second quarter of 2025.