Sustained Control with New mAb for Myasthenia Gravis

SAVANNAH, GEORGIA – The investigational monoclonal antibody nipocalimab (Johnson & Johnson) is associated with significant improvement in patients with generalized myasthenia gravis (gMG) over a 24-week period, according to topline results from the phase 3 VIVACITY-MG3 study.

The VIVACITY-MG3 trial is the first registrational study of a neonatal fragment crystallizable receptor (FcRn) blocker to show sustained efficacy through 6 months of fixed schedule dosing.

Lead investigator Tuan Vu, MD, professor of neurology at the University of South Florida in Tampa, presented the findings October 15 at American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) 2024. 

Autoantibody Depletion

FcRN plays a crucial role in the transport of immunoglobulin G. Blocking it can reduce circulating immunoglobulin G antibodies, including pathogenic gMG autoantibodies. 

The double-blind, placebo-controlled trial included 196 adults with a broad range of seropositive gMG – who account for approximately 95% of the gMG patient population – and 42 seronegative patients.

The mean age was 52 years, 92% were female, and 63% were White. The mean disease duration was about 8 years. Among seropositive patients, 87.6% were acetylcholine receptor autoantibody-positive (AChR+), 10.5% were muscle-specific kinase autoantibody-positive (MuSK+), and 2% were low-density lipoprotein receptor-related protein 4 antibody positive.

They were randomly assigned 1:1 to receive either nipocalimab IV plus standard of care, or placebo plus standard of care for 24 weeks. A total of 87 patients in the nipocalimab arm and 82 in the placebo arm completed the study.

The primary efficacy endpoint was the Myasthenia Gravis Activities of Daily Living (MG-ADL) score. Participants treated with nipocalimab demonstrated a statistically significant improvement of 4.70 points from baseline, compared to the 3.25-point improvement in those treated with placebo (P =.002). 

Clinically Meaningful Changes?

“For someone living with gMG, a 1 to 2-point improvement on MG-ADL may be the difference between normal eating and frequent choking on food, or shortness of breath at rest and being on a ventilator,” the drug’s manufacturer noted in a release. 

Secondary endpoints were also better in the nipocalimab group, compared to participants on placebo. Specifically, on the 13-item clinician assessed Quantitative Myasthenia Gravis disease severity score, patients who received nipocalimab had an average reduction of 4.86 points from baseline compared to a reduction of 2.05 points in the placebo arm (P 

Similarly, MG-ADL response (defined as ≥ 2-point improvement from baseline) was significantly greater in the nipocalimab versus placebo arms (68.8% vs 52.6%; P =.021).

Subgroup analysis revealed similar results for the different types of seropositive patients, but there was no statistically significant difference in results for seronegative patients treated with nipocalimab versus placebo.

“The drug was pretty well tolerated and there was little difference, other than more patients with muscle spasm in the nipocalimab group (12.2% vs 3.1%),” said Vu. 

In addition, peripheral edema occurred in 11.2% of the nipocalimab group and none of the placebo-treated patients. Cholesterol levels were also higher in the nipocalimab arm, but there were no cardiac side effects, he added.

Encouraging Findings

Commenting on the findings for Medscape Medical News, Neelam Goyal, MD, clinical professor of neurology and neurological sciences at Stanford University School of Medicine in Palo Alto, California, was encouraged.

“It’s a phase 3 trial, it’s positive, which is great, so it’ll be another drug on the market, another option for our patients,” she said. However, she cautioned, “their placebo arm did better than most placebos, so I think the delta is not as robust, but it was still statistically significant.” 

Goyal noted that, if approved, nipocalimab will be the third FcRn inhibitor in the MG field, preceded by efgartigimod (Vyvgart), which is approved for AChR antibody-positive disease, and rozanolixizumab-noli (Rystiggo) which is approved for both for AChR and MUSK antibody positive disease. 

“Its target of action is similar to the two drugs that are already on the market, but one thing that is unique about nipocalimab is that it is continuous dosing versus the other two medications that are given cyclically,” she said. 

“The reason that’s an upside, is that with cyclical dosing, patients have a return of symptoms. We treat, they get better, and then they get worse. That’s very disconcerting to patients. So, they want to be treated continuously.”

Additionally, she said there are some early data suggesting its safety in pregnancy.

Dr Vu disclosed he is the USF Site Principal Investigator for MG clinical trials sponsored by Alexion/ AstraZeneca Rare Disease, Amgen, argenx, Cartesian Therapeutics, COUR Pharmaceuticals, Dianthus Therapeutics, Immunovant, Johnson & Johnson, NMD Pharmaceuticals, Regeneron Pharmaceuticals, and UCB, and has served as a speaker for Alexion/AstraZeneca Rare Disease, argenx, and CSL Behring. He performs consulting work for Alexion/AstraZeneca Rare Disease, argenx, Dianthus Therapeutics, ImmunAbs, and UCB. 

Dr. Goyal disclosed consultant, advisory or grant support from argenx, UCB, Alexion, and Janssen. The study was funded by Janssen.