While Johnson & Johnson isn't the first to secure FDA approval for an FcRn-blocking antibody in myasthenia gravis, the New Jersey drugmaker is confident that a broad label will land its product an enviable market position in the long run.
The FDA on Wednesday approved J&J’s nipocalimab under the brand name Imaavy as a new treatment option for generalized myasthenia gravis (gMG). The green light, which J&J says covers the “broadest population of people living with gMG,” includes patients ages 12 and older who are anti-acetylcholine receptor (AChR) or anti-muscle-specific kinase (MuSK) antibody positive.
Anti-AChR and anti-MuSK antibody-positive people make up more than 90% of the total antibody-positive gMG population, J&J estimates. All told, the company figures gMG—which causes the communication between the body’s nerves and muscles to break down—affects around 700,000 people worldwide.
Imaavy works by blocking the protein FcRn, which is responsible for circulating the immunoglobulin G (IgG) antibodies that are known culprits in myriad autoimmune diseases. Imaavy is able to substantially reduce IgG levels, including harmful IgG autoantibodies, while sparing the body’s other immune functions, data have shown.
J&J, like others who have pursued the FcRn blockade route before it, believes IgG’s role in a range of diseases offers the chance for Imaavy to eventually expand into many different indications.
The FDA blessed Imaavy with an approval after reviewing data from J&J’s ongoing phase 3 Vivacity-MG3 study, which is testing Imaavy plus standard care against standard care and placebo in 199 adult patients with gMG, 153 of whom are antibody positive, J&J said in a press release.
In the study, the Imaavy arm displayed superior disease control through 24 weeks versus the control as measured by a gMG symptom scale. Those improvements translated to patients regaining essential daily functions like chewing, swallowing, speaking and breathing, J&J said.
What’s more, patients on Imaavy and standard care maintained those improvements out to 20 months in an open-label extension study, J&J added. The medication appears to work quickly, too, with J&J noting that Imaavy helped slash autoantibody levels by up to 75% from the first dose and throughout a 24-week monitoring period.
J&J is also running a phase 2/3 pediatric study in gMG dubbed Vibrance, in which Imaavy plus standard care met its primary endpoint by charting a 69% reduction from baseline in total serum igG over 24 weeks.
J&J did not mention in its release how soon it plans to launch Imaavy in the U.S., though the company did say that it’s rolling out a patient support program called Imaavy withMe designed to help people with commercial insurance access the treatment quickly and affordably.
J&J picked up Imaavy through its $6.5 billion takeover of Momenta Pharmaceuticals in 2020, with the FcRn blocker forming the cornerstone of the deal. J&J has since pinned blockbuster sales hopes on the drug, predicting that Imaavy could reach peak revenues in excess of $5 billion.
The analysts over at Evaluate, for their part, recently estimated that Imaavy will hit $1.2 billion in 2030 sales.
Coming market showdown
J&J will have its work cut out carving itself a niche in the FcRn space, which is currently dominated by Argenx and UCB.
Argenx first validated the FcRn blockade thesis with the FDA approval of its gMG med Vyvgart in late 2021. The company subsequently won a green light for a subcutaneous follow-on called Vyvgart Hytrulo, which has itself won an additional nod in chronic inflammatory demyelinating polyneuropathy (CIDP).
In early April, the company reported that the FDA had approved a prefilled syringe version of Vyvgart Hytrulo that will allow patients to administer the drug themselves at their homes.
Meanwhile, UCB scored a green light for its own FcRn-binding gMG treatment Rystiggo in June 2023. The approval made UCB’s drug the first for gMG approved to treat both AChR and MuSK antibody-positive patients.
UCB has also won approval for a second gMG drug dubbed Zilbrysq, which blocks the activity of the C5 complement protein rather than the FcRn protein. Unlike Rystiggo, Zilbrysq is only approved in patients who are AChR antibody positive.