NeuroVoices: Ali Habib, MD, on Cemdisiran and the Phase 3 NIMBLE Trial Data in Myasthenia Gravis

Cemdisiran (Regeneron) is an investigational complement C5-directed small interfering RNA that takes a fundamentally different approach to C5 inhibition than existing therapies. Rather than blocking C5 activity in the periphery, cemdisiran acts at the liver, where C5 is synthesized before entering circulation, with the goal of limiting production at the source. The drug is being evaluated in the phase 3 NIMBLE trial (NCT05070858) alongside pozelimab, another investigational C5 inhibitor, in a four-arm study enrolling adults with acetylcholine receptor antibody-positive generalized myasthenia gravis (gMG).

Ali Habib, MD, Professor of Neurology and Program Director of the Neuromuscular Medicine Fellowship at UC Irvine, was a presenting author on a NIMBLE hospitalization analysis at the recently concluded 2026 American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM) Annual Meeting in Orlando, Florida. Overall, the exploratory analysis found that fewer patients on cemdisiran experienced MG-related hospitalization during the 24-week double-blind period compared with placebo, 3.8% versus 15.3%, and no cemdisiran-treated patients experienced impending or myasthenic crisis requiring hospitalization.

In a new iteration of NeuroVoices, Habib explains what sets cemdisiran apart mechanistically from other C5 inhibitors, reviews the NIMBLE trial design and primary efficacy and safety findings, and shares his perspective on how the expanding treatment options in gMG are changing what clinicians and patients can realistically aim for.

NeurologyLive: For our clinical audience, provide a little bit of background on the mechanism and rationale behind cemdisiran.

Ali Habib, MD: Cemdisiran is a unique molecule being tested in the myasthenia gravis field. What’s different about cemdisiran is not the target it’s impacting, which is complement C5, but rather the way it’s targeting it. Cemdisiran is a small interfering RNA, and it acts at the liver. The liver is the site where C5 is produced and put into circulation before getting into tissues. The idea here is to limit that production at the source, and that’s what makes this approach novel compared to the other therapies that have already been used in myasthenia gravis targeting C5 inhibition.

Before we talk about the actual data, give a little bit of a snapshot of the NIMBLE trial and its design.

In myasthenia gravis, we’ve long recognized the distinction between acetylcholine receptor and MuSK antibody myasthenia. We’ve also known that MuSK myasthenia involves a different type of IgG that does not activate complement, so complement activation is not a major driver in MuSK disease. In acetylcholine receptor antibody disease, complement activation has been well documented, and that’s the main target here.

What’s also notable about this trial is that it tested two approaches to complement inhibition simultaneously. Cemdisiran is one of those therapies. The other investigational product was pozelimab, which is more along the lines of other complement inhibitors, blocking complement C5 activation in the periphery rather than at the liver. The trial was a four-arm study where patients were randomized one to one to one to one to receive either cemdisiran monotherapy, pozelimab monotherapy, the combination of cemdisiran and pozelimab, or placebo.

The randomized double-blind period was 24 weeks, and the primary outcome measure was change from baseline in the MG-ADL score at week 24. The primary analysis population was patients with acetylcholine receptor antibody-positive generalized myasthenia gravis, and there were also patients with LRP4 antibody-positive gMG included in the study. The population enrolled was broadly reflective of the general myasthenia gravis population and similar to those enrolled in other recent trials in the field.

What did the results show from an efficacy and safety perspective?

On efficacy, the primary outcome measure was the change from baseline in the MG-ADL score at week 24. When we look at the treatment response in the cemdisiran group versus placebo, there was greater improvement in the cemdisiran group, with a placebo-adjusted difference of 2.3 points. As those in the field will know, this is both a statistically significant and clinically meaningful change, meaning patients would actually notice an improvement in their symptom burden with this therapy.

On the safety side, cemdisiran was very well tolerated, with most adverse events being mild to moderate in severity. Importantly, none of those led to discontinuation of cemdisiran therapy. The most common side effect was infections, and the proportion of patients experiencing that in the double-blind period was similar to the placebo arm. With cemdisiran blocking complement activity, one of the biggest concerns is meningococcal infection. Patients were required to be vaccinated prior to starting therapy, and during the double-blind period, there were no incidences of meningococcal infection. That’s an important safety observation from the trial.

With so many options now available in gMG, how do we continue to optimize and personalize treatment for patients going forward?

As I’ve been calling it, we now have an embarrassment of riches when it comes to therapeutic options, and that’s fantastic because it has challenged us to raise the bar for outcomes. The conversation is no longer just about preventing myasthenic crisis or disease exacerbations. It’s really about returning patients to a higher quality of life, allowing them to engage in activities that are meaningful to them and continue to be productive in their careers and their lives.

One of the biggest changes over time is that we’ve had effective therapies, but they’ve taken time to show benefit, and there have been long-term safety concerns. The growing armamentarium has allowed us to achieve faster onset of action, potentially deeper disease activity, and more durable responses over time. What cemdisiran brings to the table is those factors, along with a very favorable dosing schedule. Whereas a lot of our newer therapies require more frequent periodic dosing, cemdisiran is dosed once every 12 weeks, which translates to about four treatments a year. We haven’t hit that mark in most of our other downstream therapies. It’s a great time to be in the neuromuscular and autoimmune field right now, and with cemdisiran, we’re hoping to have positive news in November.

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