France-based AB Science SA (Euronext: AB) is narrowing its clinical focus to two programs — AB8939 in relapsed/refractory acute myeloid leukemia and masitinib in amyotrophic lateral sclerosis — while formally discontinuing three studies that had already suspended enrollment. The move signals a resource allocation decision by a small-cap company operating in two highly competitive indications.
The three discontinued studies — a Phase II of masitinib in mast cell activation syndrome (AB20006), a Phase III in mastocytosis (AB15003), and a Phase III in progressive multiple sclerosis (AB20009) — were already dormant. AB Science stated the closures are not safety-related, framing them instead as a regulatory compliance measure for suspended trials with no prospect of near-term resumption. The discontinuations remove pipeline optionality but do not change the company's near-term clinical trajectory.
The more substantive update concerns AB8939, a microtubule-destabilizing agent designed to bypass two key resistance mechanisms in AML — P-glycoprotein-mediated drug efflux and myeloperoxidase-mediated drug inactivation. AB Science reported in late June the completion of Phase I, Step 3 — the maximum tolerated dose evaluation of AB8939 combined with AbbVie and Roche's Venclexta (venetoclax) — and said the study's Independent Data Monitoring Committee issued a preliminary favorable opinion. The company is now seeking regulatory authorization to initiate Phase I, Step 4, which will evaluate a triple combination of AB8939, venetoclax, and azacitidine. No numerical efficacy or safety data were disclosed.
The R/R AML landscape has shifted substantially in recent years. Syndax Pharmaceuticals' Revuforj (revumenib) received two separate US FDA approvals in 2024 and 2025 for KMT2A-translocated and NPM1-mutant AML, respectively, while Kura Oncology and Kyowa Kirin's Komzifti (ziftomenib) gained approval for NPM1-mutant R/R AML in November 2025. These menin inhibitors are mutation-specific, which leaves a meaningful gap for mutation-agnostic approaches in patients who lack targetable alterations — the population AB8939 is theoretically positioned to address. Whether those preclinical findings translate into clinical benefit remains to be demonstrated.