Myasthenia Gravis Complement Drugs Range From About 4 Doses a Year to 365, and Cemdisiran Has an FDA Decision Due in November 2026

Someone taking Zilbrysq for generalized myasthenia gravis, the form with weakness beyond the eye muscles, gives themselves 365 injections a year. A person on Ultomiris sits for 6 or 7 infusions in that same year. Both medicines block the same immune system protein, called C5, and both are approved for the same group of adults.

Two more C5 medicines are now with regulators, and they stretch that gap further. Cemdisiran was given once every 12 weeks in its main trial, and the FDA is due to decide on it in November 2026. Gefurulimab is a weekly self-injection that AstraZeneca says is under review in the US, with no decision date made public.

For you or for someone you help care for, the natural worry is whether fewer doses means a weaker medicine. The trials behind these 5 drugs do not show that. Their results overlap, as the chart further down shows. No study has tested one of these medicines directly against another, though.

What Do Complement Drugs Do in Myasthenia Gravis?

Complement drugs stop one part of the immune system from damaging the place where a nerve meets a muscle. In most people with generalized myasthenia gravis, antibodies stick to the acetylcholine receptor, the muscle's docking point for nerve signals. The National Institute of Neurological Disorders and Stroke says complement activation contributes to how those antibodies injure that junction.

Complement is a chain of blood proteins that normally helps kill bacteria. C5 is the link where the chain's final attack begins, because C5 splits into 2 pieces and one of them starts a structure called the membrane attack complex. A 2025 review in the journal Cells describes that complex as the route by which complement harms the junction in this disease.

That biology fits with how these medicines are approved, which is only for people who test positive for acetylcholine receptor antibodies. AstraZeneca puts that group at 85% of people with generalized myasthenia gravis. The same Cells review calls complement's role negligible in the form of the disease driven by MuSK antibodies.

The 5 drugs reach C5 in different ways, which explains their different schedules. Soliris and Ultomiris are lab-made antibodies that latch onto C5 in the blood, and Zilbrysq is a much smaller molecule that is injected every day. Gefurulimab is a small antibody fragment called a nanobody. The European Medicines Agency says it also binds a blood protein called albumin, which makes it last longer in the body and allows dosing once a week. Cemdisiran takes another route, because it is a small interfering RNA, a short strand of genetic material that tells the body to make less C5.

The yearly count runs from about 4 doses with cemdisiran to 365 with Zilbrysq, with Ultomiris at 6 or 7, Soliris at 26 and gefurulimab at 52. Trial Friend counted these from each FDA label's dosing schedule for the approved drugs and from the published trial schedules for the other 2. The inputs were checked on November 13, 2026.

Those counts hide some time that matters to a working week. Both infusion labels tell staff to watch the patient for at least 1 hour after each infusion ends. A Soliris infusion runs 35 minutes in adults, so 26 visits add up to at least 41 hours a year in the chair, by our arithmetic, before any travel. For Ultomiris, the label's minimum infusion time is about 42 minutes for someone weighing 60 to under 100 kilograms. That comes to at least 10 to 12 hours a year on the same basis.

Two details in the table are easy to misread. Regeneron describes cemdisiran as given under the skin, but its releases do not say whether patients would inject it themselves or receive it at a clinic. Gefurulimab's dose depends on body weight and comes in 300mg pens or syringes in Europe, and the agency's summary does not say how many of those make 1 weekly dose.

Does Dosing Less Often Mean a Weaker Myasthenia Gravis Drug?

The trial results do not show that a longer gap between doses means less benefit in generalized myasthenia gravis. Each of the 5 main trials measured the same thing, a score called MG-ADL, against a placebo, a look-alike treatment with no medicine in it. All 5 results sit in overlapping ranges, including the result for cemdisiran, the least frequent.

MG-ADL stands for Myasthenia Gravis Activities of Daily Living. The Zilbrysq label describes it as a rating of 8 everyday functions that the disease tends to affect. Each one is scored from 0 for normal to 3 for loss of that ability, which gives a total from 0 to 24. Higher scores mean more trouble, so a drop is an improvement. A 2011 study that tested the scale found that a 2-point drop for one patient usually meant their doctor also saw them as better.

In their main trials, cemdisiran, Ultomiris, Soliris, gefurulimab and Zilbrysq each improved the MG-ADL score by 1.6 to 2.3 points more than placebo. Each figure is an average, not a median, and the line through it is the 95% confidence interval. When those lines overlap as much as these do, the trials cannot tell the drugs apart. The yellow band from 1.0 to 2.4 points is this site's own reading of the 5 intervals as published, and it marks the stretch all of them share.

Several differences between the trials make a ranking unsafe even without the overlap. Zilbrysq's result was measured at 12 weeks, cemdisiran's at 24 and the other 3 at 26. The Soliris trial enrolled people whose disease had not responded to 2 or more immune-suppressing treatments. It also took people who had failed 1 such treatment and needed regular IVIg or plasma exchange, which are antibody infusions and blood-filtering sessions used for flares. People on placebo also improved by different amounts, from 1.4 points in the Ultomiris trial to 2.6 in the gefurulimab trial.

“A once-weekly, self-administered C5 treatment option would offer patients greater convenience and independence”

Kelly Gwathmey, MD, Virginia Commonwealth University, principal investigator of the PREVAIL trial, in an AstraZeneca release, July 24, 2025

One finding from the cemdisiran trial deserves a plain statement. Regeneron reported that cemdisiran alone blocked complement activity by an average of 74%, while its combination with an antibody called pozelimab blocked nearly 99%. The combination did not show a larger benefit on MG-ADL, with 1.7 points over placebo against 2.3 for cemdisiran alone, and the trial did not test the 2 against each other. Why partial blocking performed that well is an open question that the trial was not built to answer.

Where Cemdisiran and Gefurulimab Stand With the FDA

Cemdisiran has an FDA target date in November 2026, and gefurulimab is under US review without a public date. Neither had a US decision that could be found in company releases as of November 13, 2026. The cemdisiran decision page and the gefurulimab decision page on Trial Friend's FDA calendar carry the live status.

Cemdisiran, From Regeneron

Regeneron said on June 22, 2026 that the FDA had accepted its application under priority review, a faster FDA timeline. The company used a voucher, a pass that buys that faster review, to get it. The company gave the target only as November 2026, without a day. Its chief executive, Leonard Schleifer, repeated the timing when the company reported earnings on October 30th.

“We expect an FDA decision for cemdisiran in generalized myasthenia gravis next month”

Leonard S. Schleifer, MD, PhD, Regeneron, third quarter 2026 results release, October 30, 2026

The evidence is the NIMBLE trial, published in The Lancet in 2026. In the cemdisiran group, the most common side effect was a cold-like infection of the nose and throat, seen in 12% of patients against 11% on placebo. The paper reports no serious infections in that group during the 24 weeks, and none from meningococcal bacteria, the infection the approved C5 drugs carry a warning about. Everyone had to be vaccinated against those bacteria to join.

The Lancet paper also reports 2 deaths after the 24-week comparison had ended, during the trial's longer follow-up. In its August 2025 release, Regeneron said 1 was a case of pneumonia in the cemdisiran group and 1 was septic shock, a severe reaction to infection, in the combination group. The company said both patients were also taking other immune-suppressing medicines. According to the paper, the study doctor judged 1 of the 2 deaths related to treatment and the company did not.

Much of what a patient would want to know is still missing. Regeneron has announced no brand name and no price. Whether a cemdisiran label would carry the vaccine rules and safety program that the approved C5 drugs carry will be known only when the FDA acts.

Gefurulimab, From AstraZeneca

Gefurulimab, from AstraZeneca, is further along outside the US. The European Medicines Agency's expert committee recommended approval on September 17, 2026 under the brand name Klygefa. AstraZeneca's results report for the first 9 months of 2026 also lists an approval in Japan. The company's September release says applications are under review in the US and China, and it gives no FDA date.

The PREVAIL trial, published in JAMA Neurology, assigned 260 adults by chance to weekly gefurulimab or placebo for 26 weeks. Improvement on MG-ADL appeared within 1 week, according to the paper. Its authors listed injection site reactions, headache, back pain and cold symptoms as the most common side effects, and they reported no meningococcal infections.

The Meningococcal Vaccines Every Approved Myasthenia Gravis C5 Drug Requires

Soliris, Ultomiris and Zilbrysq all carry the FDA's strongest label warning, a boxed warning for serious meningococcal infections. The labels say complement inhibitors raise the risk of serious infections from meningococcal bacteria, which can cause meningitis. For a family, the vaccine step that follows from this warning usually decides how soon treatment can start.

Each label calls for meningococcal vaccines at least 2 weeks before the first dose. When treatment cannot wait that long, the labels tell prescribers to give antibiotics and vaccinate as soon as possible. Each drug is also dispensed only through an FDA safety program called a REMS, in which the prescriber enrolls and the pharmacy or infusion site is certified.

Zilbrysq adds a step the other 2 do not have. Its label asks for a starting blood test of 2 pancreas enzymes, amylase and lipase, because of a warning about pancreatitis, an inflammation of the pancreas. Our guide to a specialty prescription that has not been filled explains how steps like these can hold up a first shipment.

Three Myasthenia Gravis Situations Where the Schedule Changes the Conversation

Dose counts matter differently depending on a person's week, and 3 common situations show how. Consider first a person who lives 2 hours from the nearest infusion center. For that person the difference between Soliris and Ultomiris is about 20 fewer round trips a year. A self-injected drug removes the infusion trips, and the Zilbrysq label allows storage at room temperature for up to 3 months.

A second situation is hand weakness, which myasthenia gravis itself can cause on a bad day. The Zilbrysq label says injections into the upper outer arm should be given by a caregiver. UCB announced on October 16, 2026 that the FDA had approved a Zilbrysq autoinjector, and the company expects it to be available in the first quarter of 2027.

The third involves people who also receive plasma exchange or IVIg when symptoms flare. Those treatments lower the amount of Soliris or Ultomiris in the blood, so both labels call for an extra dose afterward. Someone in that position may have more infusions in a year than the table shows.

None of this says which medicine suits a particular person, and a neurologist weighs far more than the calendar. Bringing the table above to an appointment is one way to start that conversation. Cost questions have their own page, where help paying for myasthenia gravis medicines lists each drugmaker's program. Our earlier comparison of every approved myasthenia gravis drug covers the medicines that work in other ways.

Cemdisiran, Gefurulimab and C5 Drug Questions People Ask