US regulators have placed on clinical hold three studies testing the immunotherapy Keytruda in combination with other therapies for multiple myeloma because of patient deaths.

KEYNOTE-183 is testing Celgene’s Imnovid (pomalidomide) and low-dose dexamethasone with or without Keytruda (pembrolizumab) in refractory or relapsed and refractory multiple myeloma, while KEYNOTE-185 is assessing a combination of Celgene’s Revlimid (lenalidomide) and low-dose dexamethasone with the PD-1 inhibitor in newly diagnosed and treatment naïve patients with the blood cancer.

Both have been placed on a full clinical hold after a review of data by the Data Monitoring Committee found more deaths in the Keytruda arms of these trials, which led to the pause in new patient enrolment announced last month to allow for the collection of more data to better understand the observation.

Cohort 1 of the KEYNOTE-023 study, which is looking at Keytruda plus Revlimid and dexamethasone in multiple myeloma patients who previously received treatment with an immunomodulatory therapy, has been placed on partial clinical hold.

The US Food and Drug Administration has now determined that the data available indicate that the risks of Keytruda in combination with these drugs outweigh any potential benefit for patients with multiple myeloma, and thus all patients in these studies will discontinue investigational treatment with the drug.

Other trials involving Keytruda are not affected by the decision, the company stressed.

Keytruda was first approved in the US in 2014 for the treatment of advanced or unresectable melanoma. The PD-1 inhibitor has also been approved across a number of other indications, across lung cancer, head and neck cancer, classical Hodgkin Lymphoma, urothelial carcinoma and Microsatellite Instability-High (MSI-H) cancer.