New Biomarker May Unlock Precision Treatment for ALS and Beyond

PARIS, FRANCE – February 24, 2026 – French pharmaceutical company AB Science has announced a discovery that could pivot the treatment strategy for some of the world's most intractable neurodegenerative diseases. The company has identified a novel blood-based biomarker that signals the activity of its experimental drug, masitinib, in patients with Amyotrophic Lateral Sclerosis (ALS), potentially allowing doctors to pinpoint who will benefit most from the therapy.

The undisclosed biomarker also shows promise for identifying target patient populations in progressive forms of Multiple Sclerosis (MS) and Alzheimer's disease, creating a potential unified strategy across three devastating conditions. This development could significantly de-risk the company's clinical programs and offers a new glimmer of hope for a precision medicine approach where it is desperately needed.

A Precision Tool for a Devastating Disease

The newly identified biomarker is a significant step forward because it is easily measured in plasma via a standard blood test. According to AB Science, it is produced by pro-inflammatory microglia—the brain's resident immune cells—which are increasingly understood to play a central role in the progression of neurodegenerative diseases. The biomarker is also released by mast cells, another key immune cell type. This establishes a direct biological link between the two cell populations that masitinib is designed to inhibit, validating the drug's core mechanism of action.

Crucially, the company states the biomarker is not just a passive indicator but an active participant in the disease process, contributing to a "vicious neuroinflammation feedback loop." In-house laboratory experiments demonstrated that masitinib reduced levels of this biomarker when microglia and mast cells were activated. This suggests the biomarker could serve as a direct measure of whether the drug is hitting its intended target and calming the neuroinflammation that drives neuronal damage in ALS.

For patients and clinicians, this could transform the trial-and-error nature of ALS treatment. The biomarker is reportedly predictive of survival in ALS, offering a powerful tool to stratify patients in clinical trials and, eventually, in clinical practice. This would allow researchers to focus on individuals whose specific disease biology makes them most likely to respond, potentially leading to clearer trial results and more effective treatments.

Revitalizing Masitinib's Journey

The discovery of this biomarker could be a turning point for masitinib, a drug that has shown significant promise but has also faced a challenging regulatory path. Masitinib is an oral tyrosine kinase inhibitor that has been in development for years across multiple diseases.

In a prior Phase 2/3 study (AB10015), masitinib, when added to the standard ALS treatment riluzole, demonstrated a statistically significant 27% slowing in the rate of functional decline over 48 weeks. This effect was most pronounced in a subgroup of patients classified as "normal progressors." The drug also showed a survival benefit of over two years in this group.

Despite these positive results, AB Science encountered regulatory hurdles. In 2024, the European Medicines Agency's (EMA) Committee for Medicinal Products for Human Use (CHMP) issued a negative opinion for conditional marketing authorization, a decision that was upheld upon re-examination. The company also faced setbacks with Health Canada.

This new biomarker directly addresses the central challenge from those earlier efforts: identifying the right patient. By providing a biological signature for the patients who benefited most in the previous trial, AB Science can now refine the enrollment for its new confirmatory Phase 3 study (AB23005). This larger trial, authorized by the FDA and several European agencies, will prospectively use the biomarker to validate masitinib's mechanism of action, aiming to produce the robust data needed to finally secure regulatory approval.

A New Blueprint for Neurodegenerative Drug Development

AB Science's strategy aligns with a broader shift in neurology toward precision medicine, mirroring advances seen in oncology over the past two decades. The U.S. Food and Drug Administration (FDA) has actively encouraged drug developers to incorporate exploratory biomarkers into their clinical programs for ALS. The agency's guidance notes that a greater scientific understanding could pave the way for surrogate endpoints—biomarkers that are reasonably likely to predict clinical benefit and could serve as a basis for accelerated approval.

This biomarker could become a textbook example of that guidance in action. If validated in the upcoming Phase 3 trials, it could serve not only to select patients but also to monitor treatment response and potentially act as a surrogate for long-term clinical outcomes like survival. This would drastically shorten development timelines and reduce the cost of bringing new therapies to market for slowly progressing neurodegenerative diseases.

The approach stands in contrast to many previous therapies that have been tested on broad, heterogeneous patient populations, often leading to failed trials where a real therapeutic effect in a subgroup may have been missed. By focusing on the underlying biology of neuroinflammation, AB Science is betting that a targeted approach is the key to unlocking a successful treatment.

Beyond ALS: A Potential Triple Threat

Perhaps the most exciting aspect of the announcement is the biomarker's potential relevance beyond ALS. Neuroinflammation driven by microglia is a common pathological thread in other major neurodegenerative disorders, including progressive MS and Alzheimer's disease.

Professor Olivier Hermine, President of AB Science's Scientific Committee, noted the biomarker's broad applicability. “In multiple sclerosis, for instance, this biomarker has normal plasmatic levels in clinically isolated syndrome (CIS), is elevated in RRMS during relapse, and is high in progressive forms, consistent with what we know about the involvement of microglia in MS,” he commented in the press release.

This finding is particularly timely, as AB Science is running major Phase 3 trials for masitinib in both progressive MS (the MAXIMS study) and mild-to-moderate Alzheimer's disease (study AB21004). The company plans to introduce the biomarker into these programs as well. If the biomarker proves effective at identifying responders in these conditions, it could position masitinib as a unique, cross-disease platform therapy targeting a fundamental driver of neurodegeneration.

For now, the specific identity of the biomarker remains a closely guarded secret for patent protection reasons. Its ultimate impact will depend on rigorous validation in the large-scale clinical trials that are now underway. However, the announcement provides a clear strategic roadmap and a powerful new tool that could change the course of development not just for masitinib, but for the entire field of neurodegenerative medicine.