[Mechanism of action and clinical trial results of a new drug for amyotrophic lateral sclerosis (ALS), Mecobalamin (Rozebalamin®) for intramuscular injection, 25 mg].

Abstract

Amyotrophic lateral sclerosis (ALS) is a progressive, intractable neurodegenerative disease characterized by generalized muscle atrophy and weakness, dysarthria, dysphagia, and respiratory muscle paralysis. Respiratory dysfunction due to muscle weakness is the primary cause of death; without mechanical ventilation, death typically occurs within 2 to 5 years after onset. Mecobalamin, an active form of vitamin B₁₂, is thought to suppress homocysteine-induced neuronal cell death in ALS by acting as a coenzyme for methionine synthase, which catalyzes the conversion of homocysteine to methionine. Since the 1990s, research on neurodegenerative diseases supported by Japan's Ministry of Health, Labour and Welfare has suggested that high-dose mecobalamin may confer clinical benefits in ALS. This led to the initiation of clinical development. A Phase II/III double-blind, placebo-controlled comparative trial was conducted, but did not meet its primary endpoint. Based on these trial findings, an investigator-initiated Phase III placebo-controlled, double-blind comparative trial was conducted primarily at Tokushima University Hospital, targeting patients who developed ALS within one year before starting the trial. The trial demonstrated the efficacy of high-dose mecobalamin in slowing the decline in the Revised ALS Functional Rating Scale total score, which was the primary endpoint. Safety was also confirmed. Based on these results, mecobalamin received regulatory approval in September 2024 for the indication "slowing the progression of functional impairment in ALS." It is expected to offer a new treatment option for patients with ALS.