Study comparing key gMG treatment options finds similar efficacy

Six weeks of treatment with Rystiggo (rozanolixizumab-noli) appears as effective as Vyvgart (efgartigimod alfa-fcab) at easing symptoms of generalized myasthenia gravis (gMG), reducing its impact on daily life, and improving quality of life, according to an indirect comparison analysis of treatment options.

The analysis, based on data from three clinical trials that evaluated the treatments separately, also found that Rystiggo was associated with significantly greater muscle weakness reductions relative to intravenous immunoglobulin (IVIG) therapy.

“Without direct comparative evidence, these analyses provide additional context to inform treatment decisions for the management of gMG,” the researchers wrote. “These analyses suggest that FcRn inhibitors represent important targeted treatment options for gMG.”

The study, “Comparative Efficacy of Rozanolixizumab with Efgartigimod or Intravenous Immunoglobulin in Generalized Myasthenia Gravis Using Matching Adjusted Indirect Comparisons,” was published in Neurology and Therapy. The work was funded by UCB, the company that markets Rystiggo, and one of the study’s authors is an employee of the company.

gMG is caused when the immune system mistakenly produces self-reactive antibodies that disrupt communication between nerves and muscles, leading to MG symptoms such as muscle weakness and fatigue.

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Approved MG treatment options have expanded with the arrival of targeted therapies such as FcRn inhibitors, which work by blocking the FcRn protein and speeding the removal of antibodies, including those driving gMG, from the blood.

Rystiggo and Vyvgart are two FcRn inhibitors approved for gMG. Rystiggo is given through an under-the-skin (subcutaneous) infusion pump once weekly in six-week treatment cycles, while Vyvgart is administered directly into the bloodstream once a week in four-week treatment cycles.

However, “there are no head-to-head clinical studies directly comparing the efficacy of the FcRn inhibitors,” the researchers wrote.

IVIG is a treatment used off label for sudden periods of symptom worsening in gMG patients. It involves intravenous infusions of antibodies collected from healthy donors to help normalize the immune system activity.

A team of researchers set out to compare Rystiggo’s efficacy with that of Vyvgart or IVIG using data from three clinical studies identified through a literature review.

The Phase 3 MycarinG trial (NCT03971422), data from which supported Rystiggo’s approval, tested two doses of the treatment (7 or 10 mg/kg) against a placebo in 200 adults with gMG.

The Phase 3 ADAPT trial (NCT03669588) compared Vyvgart (10 mg/kg) with a placebo in 167 adults with gMG, most of whom had antibodies against the acetylcholine receptor (AChR) protein, the most common target of MG-driving antibodies. The findings supported Vyvgart’s initial approval for gMG patients positive for anti-AChR antibodies.

A third study, published in 2011, compared IVIG with plasma exchange, a blood-cleaning procedure used to remove self-reactive antibodies.

Before comparing treatment outcomes, researchers used statistical methods to account for differences in disease severity, duration, previous treatments, and other patient characteristics between the trial populations.

When the researchers compared outcomes at the end of each treatment’s initial dosing period — six weeks for Rystiggo and four weeks for Vyvgart — they found no significant differences across validated measures of disease severity, muscle weakness, disease’s impact on daily functioning, and quality of life relative to Vyvgart.

There were also no significant differences in the likelihood of achieving meaningful symptom improvements or reaching minimal symptom expression, a state in which symptoms have little impact on daily life.

In the separate comparison with IVIG, both Rystiggo doses were associated with significantly greater score reductions in the Quantitative Myasthenia Gravis (QMG) scale, which assesses muscle weakness through physical tests, after two and four weeks.

At two weeks, the additional score reductions compared with IVIG were 1.95 points with the lower dose and 1.99 points with the higher dose. By four weeks, these differences had increased to 3.4 and 3.99 points, respectively.

However, neither dose significantly increased the likelihood of achieving a clinically meaningful QMG score reduction of at least 3 points after two weeks, compared with IVIG. Results were generally consistent across additional analyses using different methods of matching patients.

Overall, “these results should be interpreted cautiously, considering the limitations of the included studies and the inherent constraints of indirect comparisons,” the researchers wrote, adding that the comparison between Rystiggo and IVIG was particularly limited by the absence of a common control group.

Still, “in the absence of direct head-to-head trials, these analyses provide contextual information for clinicians and suggest that FcRn inhibitors represent an important targeted treatment approach for gMG,” the researchers concluded.