AB Science has discontinued three non‑priority masitinib studies to concentrate resources on ALS and AML programs, advancing a pivotal Phase III ALS trial and next‑phase AML combination study.
Written By: Nalam Karthik, PharmD
Reviewed By: Pharmacally Editorial Team
AB Science has discontinued three non-priority clinical studies involving its investigational tyrosine kinase inhibitor masitinib, allowing the company to focus resources on two lead development programs: the Phase III study of masitinib in amyotrophic lateral sclerosis (ALS) and the clinical development of AB8939 for acute myeloid leukemia (AML).
The discontinued studies include the Phase II AB20006 trial (NCT05449444) in mast cell activation syndrome, the Phase III AB15003 study in mastocytosis, and the Phase III AB20009 trial (NCT05441488) in progressive forms of multiple sclerosis. Patient enrollment in all three studies had already been suspended.
The company said the decision reflects strategic prioritization and regulatory compliance rather than any new safety findings. AB Science will complete the closure of these studies in accordance with applicable regulatory requirements.
Focus shifts to advanced ALS and AML development
Masitinib is an oral tyrosine kinase inhibitor that targets mast cells, macrophages, and other immune pathways implicated in inflammatory and neurodegenerative diseases. It is under investigation across multiple therapeutic indications, including ALS.
The company’s lead masitinib program is the Phase III AB23005 study in ALS (NCT07174492), a progressive neurodegenerative disorder with limited treatment options. The randomized, double-blind, placebo-controlled trial will enroll 408 patients with normal disease progression who retain function across all ALS Functional Rating Scale-Revised (ALSFRS-R) domains.
Participants will receive masitinib at 4.5 mg/kg/day plus riluzole or placebo plus riluzole for 48 weeks. U.S. patients receiving edaravone will also be eligible, with edaravone incorporated as a stratification factor. Although the study received regulatory approval in 2025, enrollment has not yet started. AB Science plans to update the study protocol and implementation procedures before submitting a substantial amendment to health authorities to restart the trial.
AB8939 advances toward next AML study phase
The second priority program centers on AB8939, an investigational microtubule destabilizer being evaluated for relapsed or refractory AML.
The ongoing AB18001 Phase I/II study has completed its third step, which evaluated AB8939 in combination with venetoclax. Following a preliminary favorable recommendation from the Independent Data Monitoring Committee (IDMC), AB Science plans to seek regulatory authorization to begin the fourth study phase.
The next phase will evaluate a triple-drug regimen combining AB8939 with venetoclax and azacitidine while determining the maximum tolerated dose after 14 consecutive days of treatment. Earlier study phases established dose escalation with AB8939 alone before progressing to combination therapy.
Executive perspective
Chairman and Chief Executive Officer Stéphane Ledermann said discontinuing studies with suspended enrollment ensures compliance with regulatory obligations while allowing the company to dedicate the necessary scientific and operational resources to its highest-priority programs.
Path Forward
AB Science’s revised development strategy concentrates investment on two programs with the greatest near-term clinical potential. Key upcoming milestones include regulatory authorization to initiate the next AML combination study and submission of an amended protocol to resume the pivotal Phase III ALS trial. The company emphasized that the discontinuation of the three masitinib studies does not alter the established safety profile of the drug.
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About the Writer
Nalam Karthik (LinkedIn) is a healthcare writer and PharmD graduate with interests in pharmacovigilance, drug safety, clinical data analysis, and quality assurance. He is passionate about translating clinical and pharmaceutical knowledge into accessible healthcare content while staying engaged with advancements in drug development and patient safety initiatives.