Rozebalamin (mecobalamin)

A modified form of vitamin B12 studied for its potential to slow disease progression in ALS by protecting motor neurons from damage. Approved in Japan in 2024.

Rozebalamin is mecobalamin, a form of vitamin B12 that the body can use directly, given at doses far above normal vitamin B12 levels. How this ultra high dose slows ALS is not fully known.

In the Japanese trial, side effects judged related to the drug occurred in 7.7% of people taking rozebalamin (5 of 65) and 1.6% on placebo (1 of 64), according to Eisai. Constipation, injection site pain, fever, a change on a heart rhythm test (QT prolongation) and rash were each reported^[1].

The approved dose in Japan is 50 mg of mecobalamin injected into a muscle twice a week. The product is supplied as 25 mg vials^[1]. Treatment continues as long as the doctor believes it's helping.

Mecobalamin is currently in phase 3 clinical trials for Amyotrophic Lateral Sclerosis. It has not yet received FDA approval.

Rozebalamin is a high-dose, bioactive form of vitamin B12 (mecobalamin) given by injection, but it is not the same as over-the-counter B12 supplements. The approved dose in Japan, 50 mg twice a week by injection into a muscle, is thousands of times higher than typical supplement doses. At these pharmacological concentrations, rozebalamin may have neuroprotective effects beyond what dietary B12 provides. Standard oral B12 supplements cannot achieve these tissue levels.

No. Rozebalamin was approved in Japan in September 2024 for ALS and is not approved by the FDA. Eisai has not announced a US filing. Patients in the U.S. cannot obtain it through standard prescriptions.

No. Over-the-counter B12 supplements cannot replicate what rozebalamin does. The drug is delivered by intramuscular injection at doses far exceeding what oral supplements can achieve in nerve tissue. The specific formulation and route of administration are critical to reaching therapeutic concentrations in the nervous system. Taking oral B12 supplements, even at high doses, will not produce the same effect.

The JETALS Phase 3 trial randomized 130 people in the early stage of ALS in Japan. Over 16 weeks, people receiving rozebalamin had about 43% less decline in the ALSFRS-R function score than those on placebo, a difference of about 2 points. The results were published in JAMA Neurology in 2022 and led to Japanese approval in September 2024.

They work through completely different mechanisms. Riluzole reduces glutamate toxicity, while rozebalamin provides neuroprotection through its role as a bioactive B12 derivative. Riluzole is available worldwide, while rozebalamin is currently only approved in Japan.

Rozebalamin is given as an intramuscular injection (into the muscle) twice per week, at 50 mg per dose in Japan. The treatment schedule is ongoing as long as the physician determines it is providing benefit. This is less burdensome than IV infusion cycles but more frequent than some other ALS treatments.