AB Science Reviews Ongoing Phase 3 Study of Masitinib as ALS Treatment in Conference with Experts

AB Science recently reported positive data from an interim analysis of a Phase 2/3 study of masitinib, its lead compound to treat amyotrophic lateral sclerosis (ALS).  The company also held a web conference with leading ALS experts on April 8, followed by a report summarizing the ongoing trial.

Masitinib is a drug belonging to the tyrosine kinase inhibitor class of drugs, targeting immune cells such as macrophages and mast cells. In ALS, the drug is known to affect glia, immune cells of the brain, reducing microglial accumulation and the activity of other cells, called astrocytes.

The masitinib trial, AB10015, was initiated as a Phase 2 study and progressed to a Phase 3. In total, 392 patients were enrolled at multiple sites across Europe, Argentina, and Canada.

It is investigating two doses of masitinib as an add-on treatment to riluzole, compared to riluzole and placebo. Riluzole, the only drug currently approved for the treatment of ALS, was introduced in 1996. Since then, all drug development attempts have failed.

The interim analysis included 192 patients, and aimed to present preliminary efficacy data for discussions with regulatory authorities.

A primary outcome measure is the change in the Amyotrophic Lateral Sclerosis Functional Rating Scale after 48 weeks of treatment. The scale, recommended by regulatory authorities, measures both survival and quality of life. Patients receiving placebo typically deteriorate one point per month, assessed by the scale, and the aim of the study is to achieve a 25 percent difference in deterioration.

Secondary outcome measures are being taken in forced vital capacity and other tools for evaluating ALS severity and quality of life. AB Science reported in the interim analysis that the treatment also affected secondary measures in a beneficial way.

One of the aims of the web conference was to explain why the trial was continuing, when the interim analysis showed positive results. AS Science said that it wished to continue the trial to obtain more mature survival data and to obtain more long-term safety data.

The safety profile of masitinib is well-documented, and the rates of adverse effects were similar between patients receiving the active drug and placebo. One case of autoimmune hepatic toxicity was reported that might have been caused by the treatment.

Since the study is ongoing, AB Science did not reveal data during the web conference. The company also stated that it was not possible for patients to know to which study group they belonged to, since both riluzole and masitinib have similar profiles for side effects, mainly affecting the gastrointestinal system.