Johnson & Johnson's (J&J) human neonatal Fc receptor (FcRn)-blocking monoclonal antibody Imaavy (nipocalimab-aahu) has received US Food and Drug Administration (FDA) approval for treating generalised myasthenia gravis (gMG), a chronic autoantibody condition.

The approval comes after the agency’s priority review designation, which provides a new treatment alternative for the adult and paediatric population aged 12 and above who are positive for anti-acetylcholine receptor (AChR) or anti-muscle-specific kinase (MuSK) antibodies.

Imaavy’s approval is based on data from the pivotal Vivacity-MG3 trial.

It demonstrated that the antibody with standard of care (SOC) significantly improved disease control over 24 weeks against placebo plus SOC, as assessed by the Myasthenia Gravis-Activities of Daily Living score.

This improvement allowed subjects to regain essential daily functions such as swallowing, speaking, breathing and chewing.

Subjects maintained these improvements for up to 20 months of follow-up in the ongoing open-label extension study.

The antibody rapidly and sustainably reduces immunoglobulin G (IgG) levels, a root cause of gMG, in both adult and paediatric pivotal trials.

In the ongoing Phase II/III Vibrance paediatric trial, it has reported a 69% decrease in total serum IgG over 24 weeks.

The safety profile is consistent across the Vivacity-MG3 and the ongoing Vibrance-MG trials, with comparable tolerability observed in both age groups.

Regulatory bodies worldwide are reviewing health authority submissions for the approval of the antibody in the treatment of gMG.

The antibody is tailored to decrease levels of the circulating IgG antibodies that cause gMG, without affecting other adaptive and innate immune functions.

Johnson & Johnson innovative medicine global immunology therapeutic area head David Lee stated: “This approval is the result of years of scientific commitment, collaboration and determination for our nipocalimab programme, and we’re proud to bring this new treatment option to patients living with anti-AChR or anti-MuSK antibody positive gMG.”

In March 2025, Johnson & Johnson innovative medicine announced a $55bn investment over the next four years to expand its US footprint.