High-Dose Vitamin B12 Shows Promise in Slowing Early ALS Progression

This multicenter, double-blind, placebo-controlled phase 3 randomized clinical trial assessed whether ultrahigh-dose methylcobalamin (50 mg intramuscularly, twice weekly) could slow the clinical progression in patients with early-stage amyotrophic lateral sclerosis (ALS) who have a moderate rate of progression.

Study Design

Population: The study included 130 patients diagnosed with ALS within 1 year of symptom onset. These patients had a documented early decline on the Revised ALS Functional Rating Scale (ALSFRS-R) during a 12-week observation period, indicating moderate progression.
Intervention: Participants received either intramuscular ultrahigh-dose methylcobalamin (50 mg) or a placebo twice weekly for 16 weeks.
Primary Outcome: The main outcome measured was the change in ALSFRS-R total score from baseline to week 16.

Key Results

Functional decline slowed: Patients who received methylcobalamin experienced a smaller decrease in ALSFRS-R score compared to those on placebo (-2.66 vs -4.63). This resulted in an absolute difference of approximately 1.97 points in favor of methylcobalamin (P=.01).
Relative reduction: This corresponds to an approximate 43% relative reduction in functional decline over the 16 weeks.
Safety: The rates of adverse events were similar between the treatment and placebo groups. Ultrahigh-dose methylcobalamin was generally safe and well tolerated.
Combined therapy: In the subgroup of patients also receiving riluzole, the combined treatment showed greater differences in ALSFRS-R decline, suggesting a potential additive benefit.

Mechanistic Notes

Methylcobalamin, a form of vitamin B12, functions as a coenzyme in homocysteine metabolism. Elevated homocysteine is neurotoxic and linked to motor neuron damage. The treatment lowered plasma homocysteine levels, although changes in homocysteine were not directly correlated with functional scores.

Clinical Implications

Disease modification in early ALS: The data suggests that ultrahigh-dose methylcobalamin can slow the progression of motor dysfunction when started early in the disease course.
Treatment strategy: Due to the heterogeneity of ALS progression, early identification and patient stratification are crucial for optimizing therapeutic impact.
Safety profile: The safety results over the 16-week period were acceptable, which is promising given the limited treatment options beyond riluzole and edaravone.

Bottom Line

In patients with early-stage ALS and moderate progression, ultrahigh-dose methylcobalamin significantly slowed functional decline over 16 weeks and was well tolerated, indicating its potential as a disease-modifying therapy for this population.