Regeneron Pharmaceuticals has paused new enrolment of patients in two of its trials analysing experimental drug, odronextamab, for treating B-cell non-Hodgkin lymphomas (B-NHL).

Odronextamab is a CD20xCD3 bispecific antibody.

The move comes after the US Food and Drug Administration (FDA) put a partial clinical hold on the trials.

The FDA sought amendments in trial protocols in order to further lower the incidence of over Grade 3 cytokine release syndrome (CRS) during step-up dosing.

According to the US National Cancer Institute, the syndrome is caused by a large, rapid release of immune substances called cytokines.

This may happen after treatment with some cancer therapies and can become severe or fatal.

The syndrome has various symptoms such as fever, headache and troubled breathing, Reuters reported.

If given re-consent, participants who have been enrolled to the trial and are deriving clinical benefit from odronextamab may continue the therapy, Regeneron said.

The FDA clinical hold will impact a Phase I monotherapy trial analysing odronextamab in cancer patients with B-NHL and chronic lymphocytic leukaemia.

In addition, another Phase II monotherapy trial evaluating the drug in various subtypes of B-NHL will pause enrolment.

The company intends to submit a protocol amendment to the FDA in the first quarter of next year in order to restart patient enrolment.

In November, Regeneron Pharmaceuticals put a hold on enrolling patients requiring high-flow oxygen or mechanical ventilation in the trial of REGN-COV2, an antibody cocktail therapy for treating hospitalised patients with Covid-19.

The pause follows an independent data monitoring committee (IDMC) recommendation based on a potential safety signal and an unfavourable risk / benefit profile at this time.