Ultra-high dose methylcobalamin and other emerging therapies for amyotrophic lateral sclerosis

Recent development in understanding the pathophysiology of amyotrophic lateral sclerosis (ALS) has led to increasing number of promising test drugs in the pipeline along with the existing ones. We will review these agents focusing on ultra-high dose methylcobalamin, which is pending approval in Japan. Clinical trial design best suited for ALS will also be discussed.

The most recent phase 3 trial (JETALS) of ultra-high dose methylcobalamin demonstrated significant slowing of ALSFRSR changes (0.5/month), with marked reduction of serum homocysteine levels in the initial double-blind period. The post hoc analysis of the previous phase 2/3 study (E761 trial; Eisai) showed that it prolonged survival of ALS patients, if started within 1 year of onset, but the previous studies suggested its efficacy even in later stages, depending upon the rate of progression. Phase 3 trial of AMX0035 or Relyvrio on the other hand showed negative results despite the promising phase 2 data. The latter did not adjust the disease progression rate before entry.

Ultra-high dose methylcobalamin is not a vitamin supplement but a novel disease-modifying therapy for ALS, and it emphasizes homocysteine as a key factor in the disease process. Clinical trial design must include entering patients early and with similar rates of progression using pretrial observation periods for meaningful results, since ALS is a chronologically heterogenous condition with similar phenotypes.