Regeneron has stopped enrolling patients in two trials evaluating its monoclonal antibody odronextamab, after the FDA issued a partial clinical hold.

The affected trials are phase 1 and phase 2 studies evaluating the drug for the treatment of  B-cell nonHodgkin lymphomas (B-NHL) and chronic lymphocytic leukemia, among various disease subtypes.

The FDA made the request after some participants developed symptoms of cytokine release syndrome (CRS), an inflammatory immune response. Symptoms of the syndrome may not show up for days or weeks following treatment.

Regeneron said it plans to submit an amended trial protocol to the FDA to mitigate the risk for CRS and hopes to resume enrollment early next year.