Dive Brief:

• Regeneron has temporarily stopped enrolling new patients into trials of its experimental cancer drug odronextamab amid safety concerns raised by the Food and Drug Administration.

• The FDA put a partial clinical hold on the development program and asked Regeneron to revise its trial protocols to better control cases of cytokine release syndrome, a known side effect of cancer cell therapies in which the immune system overreacts and begins attacking the body.

• In a statement, Regeneron said it aims to resume patient enrollment in the first quarter of next year after submitting a revised trial plan to the FDA. The treatment is an important part of plans by Regeneron, best known for the eye drug Eylea, to become a major player in oncology.

Dive Insight:

The hold appears a setback, albeit possibly a temporary one, for Regeneron’s cancer drug pipeline.

Though the company has already won approval of its first cancer drug, Libtayo, it is looking to a new class of antibody drugs to build on that foundation. The company has two such “bispecific” cancer treatments, which use antibodies to bind to proteins on both tumor and immune cells, in mid-stage testing. Odronextamab, being developed for non-Hodgkin lymphoma, is one of them.

Odronextamab targets the CD20 protein expressed on certain cancer cells and the CD3 protein on immune cells. So do similar, competing drugs from Roche, Genmab and Xencor. Each are in early clinical trials for certain blood cancers.

Ordonextamab, as well as another bispecific antibody for multiple myeloma, are “the stars of Regeneron’s oncology pipeline,” SVB Leerink analyst Geoffrey Porges recently wrote, but each face “significant intra-category competition.”

Regeneron highlighted odronextamab’s promise as a top pipeline prospectat the American Society of Hematology’s virtual meeting earlier this month. At the time, the company said the majority of cytokine release syndrome events seen in patients were mild or moderate.

Yet the frequency of the events are an apparent concern for the agency, which wants Regeneron to amend its trial protocol in an effort to reduce instances of CRS. The drug has recorded “some of the higher rates of severe CRS” in its drug class, wrote RBC Capital Markets analyst Kennen MacKay, who favors Genmab’s program.

The decision affects two clinical trials of odronextamab: a Phase 1 study in patients with B-cell non-Hodgkin lymphomas, or B-NHL, and chronic lymphocytic leukemia, and a Phase 2 study in subtypes of B-NHL.

Patients who are currently benefiting from treatment can continue on odronextamab after renewing their participation consent, Regeneron said.

While the pause is “undoubtedly a negative” development for Regeneron, safety concerns had already dimmed prospects for the product, according to a note from Baird analyst Brian Skorney. “We don’t view this update as entirely shocking,” Skorney wrote.

Regeneron shares dropped by as much as 2.7% in early trading Tuesday.