Last year, Johnson & Johnson arrived late to the party with Imaavy as the third FcRn blocker approved since 2021 to treat patients with generalized myasthenia gravis (gMG).
But J&J has hopes for the monoclonal antibody in several other indications, including one rare disease in which it appears to be setting the pace—warm autoimmune hemolytic anemia (wAIHA).
On Thursday, the company unveiled data from a pivotal phase 2/3 trial which could pave the way for a label expansion for Imaavy.
In the Energy study, Imaavy worked quickly and elicited a statistically significant durable red blood-cell count response in patients with wAIHA, a life-threatening disorder which has no approved therapies. There is an urgent unmet need in the indication, where patients to rely on corticosteroids and immunosuppressive therapies which do not address the underlying cause of the disorder, according to J&J.
The trial, which included 115 participants who were randomized 1:1:1 to receive two different doses of Imaavy or placebo, showed that three times as many patients who were infused with a 30 mg/kg dose of Imaavy achieved durable hemoglobin (Hgb) levels versus those on placebo after 24 weeks.
The primary endpoint of the study was defined as an increase from baseline in Hgb of at least 2 g/dL and an Hgb concentration of at least 10 g/dL for at least 28 days without the need for rescue therapy or alterations in background treatment. Nearly two-thirds of treated patients achieved both of these targets by Week 24, J&J said.
“Achieving hemoglobin improvements this quickly and at this scale is important in clinical practice, as it could help improve the debilitating fatigue that people living with warm autoimmune hemolytic anemia experience,” Bruno Fattizzo, M.D., of the Department of Oncology and Hematology-Oncology at the University of Milan, Italy, said in a release.
Changes in patient-reported fatigue were seen as early as Week 2 in the trail and sustained throughout the treatment period, which was a key secondary endpoint. Another secondary objective, reductions in steroid use, also was achieved, J&J said. Imaavy also demonstrated a safety profile consistent with its use in gMG.
J&J has already submitted for approval in the indication at the 30 mg/kg dose, gaining an FDA priority review designation in April, becoming the first to do so in the indication.
The key to Imaavy’s effectiveness in the indication is its “immunoselective approach,” according to J&J’s Disease Area Leader for Autotibody and Rheumatology, Leonard Dragone, M.D., Ph.D.
Imaavy “targets the underlying autoantibodies driving disease while preserving key immune functions, which is important for people living with this disease who frequently suffer with comorbid conditions,” he said in the release.
J&J acquired Imaavy in its $6.5 billion buyout of Momenta Pharmaceuticals in 2020. The company has tabbed the treatment with peak sales potential of $5 billion or more and is investigating its use in a host of autoimmune disorders including Sjogren’s disease, hemolytic disease of the fetus and newborn and fetal neonatal alloimmune thrombocytopenia. Each of the programs are in phase 3 testing and have received FDA fast-track designation.
J&J also has advanced Imaavy to phase 3 in chronic inflammatory demyelinating polyneuropathy and to phase 2 in systemic lupus erythematosus and idiopathic inflammatory myopathy.
Last year, after coming up short in a phase 2a trial, the company bailed on its attempt to advance Imaavy as a combo agent in rheumatoid arthritis.
Beating J&J to the finish line with FcRn blockers to treat gMG were argenx, which gained its approval for Vyvgart in 2021 and reported its sales at $4.2 billion in 2025, and UCB, which scored an FDA nod for Rystiggo in 2023 and reported its 2025 sales at 332 million euros ($375 million).
J&J has yet to divulge sales of Imaavy, which it launched in April of last year, with the broadest label in the indication.