Regulators in US, EU now reviewing cemdisiran for treating gMG

Regulators in the U.S. and the European Union have agreed to review applications seeking approval of Regeneron Pharmaceuticals‘ cemdisiran to treat adults with generalized myasthenia gravis (gMG) who have self-reactive antibodies targeting the acetylcholine receptor (AChR) protein.

Further, the U.S. Food and Drug Administration (FDA) has granted the application priority review, which shortens the review period to six months from the standard 10 months, Regeneron announced in a company press release.

A decision is now expected by November in the U.S., and in the second half of 2027 in the EU. Regeneron is also planning to file an application for cemdisiran’s approval in Japan at the beginning of next year.

According to the company, the regulatory submissions are supported by results from NIMBLE (NCT05070858), a global Phase 3 clinical trial that tested the therapy candidate in more than 280 people with gMG. Data showed that six months of cemdisiran treatment significantly eased symptoms and reduced disease activity and severity in gMG patients.

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Regeneron stated that cemdisiran could be the first small interfering RNA (siRNA)-based therapy approved for gMG, as well as the only gMG medication administered via subcutaneous, or under-the-skin, injections four times per year.

siRNAs are molecules that regulate gene activity by targeting messenger RNA (mRNA), an intermediate molecule generated from DNA that’s used as a template in protein production.

Submissions supported by positive NIMBLE trial data

A chronic autoimmune disease, gMG is caused by self-reactive antibodies that target proteins, most commonly AChRs, involved in nerve-muscle communication. This disrupts communication between nerves and muscle cells, leading to symptoms such as muscle weakness and fatigue.

When gMG-driving antibodies bind to certain targets, particularly AChRs and lipoprotein receptor-related protein 4 (LRP4), they activate the complement pathway, a part of the immune system, further contributing to gMG-related damage.

Administered by subcutaneous injections, cemdisiran is a siRNA-based therapy that blocks complement activation by suppressing the production of the complement protein C5.

The NIMBLE study was designed to test cemdisiran alone or in combination with pozelimab — Regeneron’s antibody-based therapy designed to block C5 — in adults with gMG and antibodies against AChR or LRP4. Pozelimab is a subcutaneous therapy approved under the brand name Veopoz for an ultra-rare immune disease.

The trial recruited 288 adults with gMG who were randomly assigned to receive either cemdisiran once every three months, cemdisiran plus pozelimab once a month, pozelimab alone monthly, or a placebo once a month.

After six months of treatment, participants given cemdisiran alone experienced a mean 4.5-point score reduction in the Myasthenia Gravis-Activities of Daily Living (MG-ADL) scale and a 4.2-point score drop in the Quantitative MG score (QMG) scale.

The observed score changes in these standard gMG measures reflected improvements in daily functioning and reductions in disease severity that were greater than those seen with the cemdisiran/pozelimab combo or the placebo.

The superior benefits seen with cemdisiran occurred regardless of the fact that the therapy resulted in inferior complement activity suppression relative to the combo, the researchers noted.

Cemdisiran-based regimens were generally safe and well tolerated, with the most commonly reported adverse events in the cemdisiran group being upper respiratory tract infection.

After completing this part of the study, participants could enter its extension portion, in which all receive cemdisiran, alone or with pozelimab, for 28 weeks, or nearly seven months. Treatment may continue for another year in a subsequent open-label extension portion.