AB Science Suspends Three Masitinib Trials to Concentrate Resources on ALS and AML Programs

Trial closeout obligations and protocol amendment filings are the immediate operational consequence for AB Science SA as the Paris-based company formally discontinues three masitinib studies and narrows its active clinical portfolio to two priority programs: AB8939 in acute myeloid leukemia and masitinib in amyotrophic lateral sclerosis.

The three discontinued studies, a Phase 2 investigation of masitinib in mast cell activation syndrome (AB20006), a Phase 3 study in mastocytosis (AB15003), and a Phase 3 study in progressive forms of multiple sclerosis (AB20009), had already suspended patient enrollment. AB Science confirmed the discontinuations carry no safety signal for masitinib; the decision reflects resource allocation under regulatory compliance obligations rather than any efficacy or pharmacovigilance concern. The company has stated it will complete each study in accordance with applicable regulations, meaning formal closeout procedures, final study reports, and regulatory notifications remain outstanding work items.

For QA and regulatory leads tracking the AML program, AB Science has completed Phase 1, Step 3 of the AB18001 study, which evaluated AB8939 in combination with venetoclax in relapsed/refractory AML. The company is now seeking health authority authorization, supported by a preliminary favorable opinion from the study's Independent Data Monitoring Committee (IDMC), to advance to Phase 4, which will assess the triple combination of AB8939, venetoclax, and azacitidine. IDMC endorsement at this juncture provides a documented evidentiary basis for the regulatory submission, a procedural checkpoint that will be scrutinized in any subsequent inspection of the trial master file.

The ALS program carries a distinct regulatory complexity. The Phase 3 AB23005 study received health authority approval in 2025 but has not yet initiated. Before enrollment can begin, AB Science must submit a substantial amendment to update the protocol and implementation procedures, then obtain renewed authorization. The study is a 408-patient, randomized, double-blind, placebo-controlled design evaluating masitinib at 4.5 mg/kg/day alongside riluzole over 48 weeks, with U.S. patients on edaravone eligible as a stratification subgroup, a design feature that adds a layer of site-level procedural alignment across geographies.

Chairman and CEO Stéphane Ledermann framed the discontinuations explicitly as a compliance-driven decision, noting that terminating studies with no prospect of rapid resumption is consistent with regulatory requirements and with concentrating quality resources on the two active programs.

The measurable near-term checkpoint is the substantial amendment submission for AB23005; its acceptance timeline will determine when the ALS Phase 3 can formally open to enrollment.

Source: AB Science SA via GlobeNewswire, July 10, 2026.