FDA approves Klygefa, a once-a-week shot people with myasthenia gravis can give themselves at home

The Food and Drug Administration on Friday approved Klygefa, a weekly shot that patients or caregivers can inject at home, for adults with generalized myasthenia gravis who test positive for antibodies against the acetylcholine receptor, according to the FDA label and FDA approval records.  The drug, also called gefurulimab, is made by Alexion, part of AstraZeneca.

What myasthenia gravis is

Myasthenia gravis is an autoimmune disease, meaning the body’s defenses attack its own tissue.  Antibodies block signals from nerves to muscles, causing drooping eyelids, double vision, trouble swallowing or speaking and weak arms and legs, and sometimes breathing trouble, the National Institute of Neurological Disorders and Stroke says.

The weakness usually gets worse with activity and better with rest, and it often starts in the eyes, MedlinePlus, the National Library of Medicine’s health site, says.  About 15% to 20% of patients have at least one myasthenic crisis, when breathing muscles weaken so much that a person needs a ventilator, an emergency, NINDS says.  There is no cure, but most people with the disease live a normal life span.

How many people have it and who gets it

About 20 in every 100,000 people worldwide, or roughly 1 in 5,000, have myasthenia gravis, MedlinePlus says, and that share has been rising as doctors diagnose it earlier and patients live longer.  At that rate, Santa Clara County, with nearly 2 million residents, would have roughly 400 people with the disease, by our arithmetic.

It can strike at any age and in people of every race and ethnic group, but it is most often diagnosed in women younger than 40 and men older than 60, NINDS says.  It is not contagious and usually not inherited, though about 3% to 5% of patients have relatives with it or another autoimmune disease, MedlinePlus says.  About 75% of patients have an enlarged, overactive thymus, an immune gland behind the breastbone, which sometimes grows tumors that are usually not cancer.

Existing treatments include pills that boost nerve signals to muscles, surgery to remove the thymus, drugs that suppress the immune system and complement blockers like eculizumab, NINDS says.  Klygefa joins that last group as a shot patients can give themselves at home.

How it works and what the trial found

Klygefa blocks a protein called C5 in the complement system, a part of the immune system that damages the nerve-muscle connection in this disease.  It comes in a prefilled autoinjector pen.  In a 26-week trial of 260 adults, scores on a 24-point daily-living scale improved by 4.2 points on the drug versus 2.6 on a placebo, and 65.5% of drug patients improved by at least 3 points, compared with 52.2% on placebo, the label says.  Injection-site reactions were the most common side effect.

Safety rules

Like other C5 blockers, Klygefa carries a boxed warning, the FDA’s strongest, for serious and possibly fatal meningococcal infections.  Patients must be vaccinated at least two weeks before starting, and doctors must enroll in a restricted program to prescribe it.  People with the disease can ask their neurologist whether they qualify.  A price was not in the records reviewed.

Source:  FDA prescribing information for Klygefa, Nov. 2026; Drugs@FDA, BLA 761488; National Institute of Neurological Disorders and Stroke; Medscape, April 27, 2026; MedlinePlus Genetics, Myasthenia gravis.