Regeneron Reports Positive Result in gMG Study

Rare Daily Staff

Regeneron Pharmaceuticals said its experimental therapy cemdisiran met the primary endpoints and key secondary endpoints in a phase 3 trial for adults with generalized myasthenia gravis, a rare autoimmune disease that causes muscle weakness.

Cemdisiran monotherapy, dosed subcutaneously every three months, showed a 2.3-point placebo-adjusted improvement in the Myasthenia Gravis Activities of Daily Living total score in its phase 3 NIMBLE trial.

The trial also assessed a combination of cemdisiran and pozelimab, a C5 antibody. This combination, which resulted in nearly 99 percent inhibition of complement activity, also met the primary and key secondary endpoints, though cemdisiran monotherapy was numerically better across these endpoints.

Regeneron said it expects to apply to the U.S. Food and Drug Administration for approval to market cemdisiran monotherapy in the first quarter of 2026, pending discussions with the agency.

Myasthenia gravis is a rare and chronic autoimmune disease that results when abnormal antibodies activate the complement system, including C5, disrupting communication between nerves and muscles and causing debilitating and potentially life-threatening muscle weakness. Initial manifestations are usually ocular, but about 85 percent of patients experience additional progression of the disease, which is known as generalized myasthenia gravis, or gMG. For these patients, the disease affects muscles throughout the body, resulting in extreme fatigue, and difficulties with facial expression, speech, swallowing, and mobility. Treatment-related challenges—including frequent hospital visits, inconsistent symptom control, and lack of durable treatment effects—can further affect quality of life and long-term disease management.

Cemdisiran is an siRNA that reduces circulating levels of complement factor 5, or C5, and, as monotherapy in this trial, was associated with an average of 74 percent inhibition of complement activity.

“The NIMBLE trial results underscore the potential for cemdisiran to offer a best-in-class profile for those suffering with myasthenia gravis, providing robust efficacy with convenient quarterly subcutaneous administration,” said George Yancopoulos, board co-chair, president, and chief scientific officer at Regeneron. “The potential for best-in-class efficacy with less than complete complement blockade with cemdisiran monotherapy may also provide a more favorable safety profile. These exciting results highlight the transformative potential of our siRNA and genetic medicines pipeline to deliver paradigm-changing therapies for patients.”

Photo: George Yancopoulos, board co-chair, president, and chief scientific officer at Regeneron