NEW YORK (REUTERS) - Regeneron Pharmaceuticals Inc said on Monday (Dec 14) it was pausing patient enrolment in two trials testing its experimental lymphoma drug, after the US health regulator requested changes in trial protocols.

Participants benefiting from the drug, odronextamab, may continue treatment, the drugmaker said, if they give their consent.

The US Food and Drugs Administration (FDA) had placed the trials on partial clinical hold and asked the company to change protocols to reduce the occurrence of an inflammatory response called cytokine release syndrome in patients, according to Regeneron.

The syndrome, caused by a large, rapid release of immune substances called cytokines, may occur after treatment with some types of cancer therapies and can sometimes be severe or fatal.

It has different symptoms including fever, headache and troubled breathing, according to the National Cancer Institute.

The company said FDA's decision impacts an early-stage trial testing odronextamab in cancer patients with B-cell non-Hodgkin lymphomas (B-NHL) and chronic lymphocytic leukemia.

Another mid-stage trial testing the drug in sub-types of B-NHL will also pause enrollment, Regeneron said.

It said it planned to submit the details of changed protocols to the FDA with the goal of resuming patient enrolment early in the first quarter of 2021.