Merck & Co has paused patient enrolment in two trials of Keytruda to allow investigators to explore reports of deaths among patients taking the PD-1 inhibitor.
The two phase III studies are testing Keytruda (pembrolizumab) in combination with other drugs in patients with blood cancer, and showed an imbalance in the number of deaths between the groups.
Patients already enrolled will continue on treatment while the investigation plays out, said Merck (known as MSD outside North America). The two trials – KEYNOTE-183 and KEYNOTE-185 – involve combinations of Keytruda with Celgene’s Pomalyst (pomalidomide) and Revlimid (lenalidomide), two drugs that are widely-used in myeloma treatment.
“The pause is to allow for additional information to be collected to better understand more reports of death in the Keytruda groups,” said Merck in a statement, noting that other trials of its flagship immuno-oncology treatment are continuing unchanged.
The company is not speculating on what might be behind the signal, but will be hoping it is not linked to any interaction with the established myeloma therapies as this could be an obstacle to extending the use of its drug into haematological malignancies. Earlier this year Keytruda was approved for classical Hodgkin lymphoma (cHL) – its first non-solid tumour indication – and expanding into blood cancers is a key target for Merck.
Such is the importance attached to Keytruda to the company that its shares slipped by around 1.25% yesterday on the suspension, which comes against a series of positive developments for the drug including a landmark first approval for microsatellite instability-high (MSI-H) solid tumours.
Keytruda made $1.4bn for Merck last year adding another $584m to that tally in the first three months of this year. It is chasing market leader Opdivo (nivolumab) from Bristol-Myers Squibb, which brought in $3.77bn and $1.13bn, respectively.