UCB finally gets a win with the FDA, scoring approval for myasthenia gravis drug Rystiggo

This has been a second straight year of regulatory struggles in the United States for UCB with one of the those issues revolving around the FDA needing additional time to review its application for plaque psoriasis candidate bimekizumab.

That news hit on Monday but UCB got an instant lift on Tuesday as good news finally arrived from the FDA in the form of a green light for Rystiggo (rozanolixizumab-noli) for the rare autoimmune condition myasthenia gravis (gMG).

The subcutaneously administered monoclonal antibody becomes the first therapy approved to treat the two primary subsets of the disorder—those who are anti-acetylcholine receptor (AChR) or anti-muscle-specific tyrosine kinase (MuSK) antibody positive, though not the first drug for the disorder, with two therapies from AstraZeneca and argenx already on the market for gMG. 

In those with gMG, pathogenic IgG autoantibodies destroy the communication between nerves and muscles. The disorder can cause life-threatening weakness of muscles that control breathing, swallowing, chewing and talking. It can strike anyone at any age but is more frequently seen in young women and men aged 50 and older. Double vision and drooping eyelids are common initial symptoms.

Rystiggo works by binding to the neonatal Fc receptor, causing a reduction of circulating IgG.

The approval was backed by a phase 3 trial of 200 patients with the AChR or MuSK subsets of the disease. The study showed statistically significant improvements in eight gMG-specific outcomes including breathing, walking, talking and rising from a chair.

“People living with gMG often face treatment options that are broad-acting, and that have traditionally only offered symptomatic relief,” Vera Bril, a professor at the University of Toronto and lead investigator in the MycarinG study, said. “Rozanolixizumab-noli is a new treatment option, targeting one of the mechanisms of disease to provide symptom improvement.”

UCB expects Rystiggo to be available in the third quarter. It will charge a list price of $6,050 per vial, with dosage dependent on a patient's weight and administered depending on the prevalence of symptoms. The drug remains under review in Japan and Europe.

UCB has another candidate nearing approval in the indication. Complement factor C5 inhibitor zilucoplan, which was acquired in a $2.5 billion buyout of Ra Pharmaceuticals, has yielded positive phase 3 data in a study of patients with the AChR subset of gMG.

There is formidable competition in the gMG space as AstraZeneca won approval for Ultomiris in the indication last year. Just a week ago, argenx gained an FDA nod for Vyvgart Hytrulo.

Earlier this month, UCB gained approval in Europe for bimekizumab to treat two conditions—active psoriatic arthritis and active axial spondyloarthritis (axSpA). But on Monday came word of the FDA’s delay in a decision on the treatment in plaque psoriasis. In May of 2022, the U.S. regulator rejected UCB’s application because of inspection issues.

Last month, the FDA pinged UCB with a Form 483 after an inspection of its plant in Braine-l’Alleud, Belgium. The company said then that the issues would not affect its submission for bimekizumab.