Eculizumab Shows Promising Results in Adolescents With Myasthenia Gravis

Eculizumab effectively alleviates symptoms in adolescents with refractory generalized myasthenia gravis, which causes weakness in muscles after periods of activity.

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Eculizumab effectively alleviates symptoms in adolescents with refractory generalized myasthenia gravis, according to research published in Pediatric Neurology. The treatment demonstrated significant clinical benefits and a favorable safety profile over a 26-week period.¹

Myasthenia gravis causes weakness in muscles after periods of activity that tends to improve after a period of rest. The degree of weakness care vary and be as severe as to be a life-threatening condition.²

Statistically significant improvements were seen in both primary and secondary end points in adolescents receiving eculizumab. The change in the Quantitative Myasthenia Gravis total score from baseline to week 26 (primary end point) saw least-squares mean changes of –5.8 (SE 1.2; P = 0.0004). Myasthenia Gravis-Activities of Daily Living total score (secondary end point) saw least-squares mean changes from baseline of –2.3 (SE 0.6; P = 0.0017).

"Overall, the primary and all secondary efficacy endpoint analyses met statistical significance from the first assessment and were sustained throughout," the authors wrote. Other secondary end points included Myasthenia Gravis Foundation of America postintervention status, EuroQol 5-Dimensions (Youth) score, and Neurological Quality-of-Life Pediatric Fatigue questionnaire score.

The study was a phase 3, open-label, multicenter study, which included 11 adolescents aged 12 to 17 years (mean age 14.8 years) who were anti-acetylcholine receptor (AChR) antibody–positive and had not responded adequately to previous treatments for myasthenia gravis. The participants received eculizumab in weekly induction doses (1 to 2 doses of 600 mg or 4 doses of 900 mg) followed by maintenance doses (300 to 1200 mg) every 2 weeks for up to 26 weeks, based on the participant's body weight. During the study, participants were allowed to continue their existing therapy with acetylcholinesterase inhibitors, maintenance IVIG, and immunosuppressants.

"Only 3 patients reduced their requirement for corticosteroids by the end of week 26," the authors wrote. "However, the additional significant clinically meaningful improvements achieved with eculizumab provided important benefit to these patients even if other additional therapies could not be discontinued."

Ten participants completed the primary evaluation period and entered the ongoing 208-week extension period. The study reported that eculizumab was generally well tolerated, with the most common adverse events being headache and nasopharyngitis. Three patients experienced serious adverse events, including worsening of MG, MG crisis, and peritonsillar abscess. "There were no deaths or meningococcal infections, and no clinically meaningful findings with regard to abnormal laboratory results, electrocardiogram findings, physical examination, and vital signs." No patients developed anti-eculizumab antibodies.

Pharmacokinetic and pharmacodynamic analyses showed that "Eculizumab serum concentrations followed anticipated behavior, with concentrations above the therapeutic threshold of 116 µg/mL in all samples except 2 (one at week 1 pre-dose and one at week 12 pre-dose) during the primary evaluation period," and free C5 concentrations were below the therapeutic response threshold of 0.5 µg/mL at all time points in all patients during the primary evaluation period, indicative of complete terminal complement inhibition, which was sustained throughout 26 weeks in all patients.

"Findings were consistent with those previously demonstrated in adult patients in the phase 3 REGAIN study, in which eculizumab was well tolerated during the 26-week placebo-controlled period," the authors wrote.

The phase 3, randomized, double-blind, placebo-controlled REGAIN study of adults with AChR Ab–positive refractory generalized myasthenia gravis also demonstrated statistically significant improvements in functional ability, muscle strength, and quality of life compared with placebo.³ Despite the open-label design of the current study, the rapid clinical benefits observed in adolescents were significant and consistent with the known pharmacokinetic and pharmacodynamic profile of eculizumab in adults.

References

1. Brandsema JF, Ginsberg M, Hoshino H, et al. Eculizumab in adolescent patients with refractory generalized myasthenia gravis: a phase 3, open-label, multicenter study. Pediatr Neurol. 2024;156:198-207. doi:10.1016/j.pediatrneurol.2024.04.020

2. Boston Children's Hospital. Myasthenia gravis. Accessed June 18, 2024. https://www.childrenshospital.org/conditions/myasthenia-gravis

3. Howard JF Jr, Utsugisawa K, Benatar M, et al. Safety and efficacy of eculizumab in anti-acetylcholine receptor antibody-positive refractory generalised myasthenia gravis (REGAIN): a phase 3, randomised, double-blind, placebo-controlled, multicentre study [published correction appears in Lancet Neurol. 2017;16(12):954]. Lancet Neurol. 2017;16(12):976-986. doi:10.1016/S1474-4422(17)30369-1