By Fineline Cube 
US-based Regeneron Pharmaceuticals Inc. (NASDAQ: REGN) on Aug 27, 2025 disclosed that its investigational monotherapy, cemdisiran, achieved both primary and key secondary endpoints in the Phase III NIMBLE trial for adults with generalized myasthenia gravis (gMG).
What is Cemdisiran?
- Mechanism: Small interfering RNA (siRNA) that lowers circulating complement factor 5 (C5).
- Efficacy: Monotherapy produced an average 74 % inhibition of complement activity; the cemdi‑poze combination (cemdisiran + C5 antibody pozelimab) achieved nearly 99 % inhibition.
Trial Design
- Population: Adults with symptomatic anti‑acetylcholine receptor (anti‑AChR) positive gMG.
- Standard Care: Patients received investigator‑discretion immunosuppressants.
- Endpoints: Primary endpoints focused on overall clinical improvement; key secondary endpoints assessed daily functional activities at 24 weeks.
Key Findings
- Monotherapy: Demonstrated superior improvements across all gMG‑specific outcomes at week 24.
- Combination Therapy: Also met primary and key secondary endpoints with a higher complement inhibition rate.
- Safety: No new safety signals; adverse event profile consistent with previous studies.
Implications for gMG Treatment
- First siRNA Therapy: Cemdisiran represents a novel therapeutic modality for gMG, potentially offering a more targeted approach than existing immunosuppressants.
- Patient Convenience: The high complement inhibition with a single drug could streamline treatment regimens.
- Regulatory Path: Positive Phase III results support accelerated development for regulatory submissions in the U.S. and EU.-Fineline Info & Tech