FILE PHOTO - A view shows the U.S. Food and Drug Administration (FDA) headquarters in Silver Spring, Maryland August 14, 2012. REUTERS/Jason Reed/File Photo

(Reuters) - The U.S. Food and Drug Administration has placed a partial hold on three clinical trials testing Bristol-Myers Squibb’s immunotherapy Opdivo in combination with other medicines for multiple myeloma due to risks seen in similar studies involving a rival drug, the company said on Wednesday.

Patients with relapsed multiple myeloma taking part in the trials who were experiencing clinical benefit will be allowed to continue treatment, but no new patients will be enrolled for now, Bristol Myers said.

The FDA in July placed a hold on three Merck & Co multiple myeloma trials testing its Keytruda along with other standard medicines for the blood cancer following reports of more deaths in patients who received Keytruda than in the control arms of the studies.

Opdivo and Keytruda belong to a high-profile new class of drugs called PD-1 inhibitors that work by blocking a mechanism tumors use to hide from the immune system, allowing it to detect and attack cancer.

“The FDA determined data currently available from non-Opdivo studies indicate the risks of PD-1/PD-L1 treatment plus pomalidomide or lenalidomide and possibly PD-1/PD-L1 treatments alone or with other combinations outweigh potential benefit for patients with multiple myeloma,” Bristol-Myers said on its website.

Lenalidomide and pomalidomide are the widely used Celgene Corp multiple myeloma treatments Revlimid and Pomalyst.

“BMS remains steadfast in our commitment to improve outcomes for patients with multiple myeloma, and will work closely with the FDA to address concerns,” the company said in a statement.