Alexion announced the publication of data from the phase 3 open-label extension of the REGAIN trial (ECU-MG-302) that assessed the long-term safety and efficacy of eculizumab (Soliris) for the treatment of adults with anti-acetylcholine receptor (AChR) antibody-positive refractory generalized myasthenia gravis (gMG). The data have been published in the journal Muscle & Nerve.

Of the 125 patients who completed the REGAIN (ECU-MG-301) study, 117 were enrolled in the open-label extension phase and administered eculizumab 1200mg every 2 weeks for a median 22.7 months. Results from the interim analysis showed that improvements seen in the first 6-month phase of the double-blinded REGAIN trial were sustained over 3 years in the areas of activities of daily living, muscle strength, functional ability, and quality of life.

In addition, patients who received placebo in REGAIN demonstrated rapid and significant improvement after starting eculizumab in the open-label extension phase (P <.0001). At interim data cutoff, >55% of patients in the open-label extension exhibited clinically meaningful response, as measured by the MG-Activities of Daily Living scale (MG-ADL). Moreover, 56% of patients experienced minimal manifestations or pharmacological remission.

Regarding safety, no cases of meningococcal infection were observed during the interim analysis period and the safety profile seen in REGAIN was further confirmed by data from the open-label extension. Headache and nasopharyngitis were the most common adverse events, as seen in 37.6% and 31.6% of patients, respectively. Compared with data 1 year prior to the start of REGAIN, patients in the open-label extension had a 75% reduction in exacerbations (P <.0001) and an 83% reduction in hospitalizations.

“These results confirm that treatment with eculizumab can provide anti-AChR antibody-positive gMG adult patients with tangible and durable clinical benefits and can help to reduce the burden of this devastating disease on patients and their families,” said Srikanth Muppidi, MD, Clinical Associate Professor, Department of Neurology and Neurosciences at Stanford University School of Medicine.

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Eculizumab, a monoclonal antibody, specifically binds to the complement protein C5 with high affinity, thereby inhibiting its cleavage to C5a and C5b and preventing the generation of the terminal complement complex C5b-9. The precise mechanism by which eculizumab exerts its therapeutic effect in gMG patients is unknown, but is presumed to involve reduction of terminal complement complex C5b-9 deposition at the neuromuscular junction.

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