On July 10, 2026 AB Science SA (Euronext – FR0010557264 – AB) reported an update on its clinical development program and announces the discontinuation of certain non-priority clinical studies in order to focus on two clinical programs, the AB8939 program for acute myeloid leukemia and the masitinib program for amyotrophic lateral sclerosis.

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Following the company’s press release dated April 16 [1], three clinical studies—which the company currently considers non-priority and for which patient enrollment had been suspended—are being discontinued, namely:

Phase 2 study (AB20006) of masitinib in mast cell activation syndrome
Phase 3 study (AB15003) of masitinib in mastocytosis
Phase 3 study (AB20009) of masitinib in progressive forms of multiple sclerosis

The discontinuation of these studies is not related to any safety concerns regarding masitinib. The company intends to complete these clinical studies in accordance with applicable regulations.

Stéphane Ledermann, Chairman and CEO of AB Science, stated, "This decision to terminate non-priority studies for which recruitment had been suspended and for which there is no prospect of a rapid resumption reflects compliance with regulatory requirements. It is also consistent with our commitment to allocate all necessary resources to ensure the two priority programs are carried out to the highest standards of quality."

Regarding the AB8939 program for acute myeloid leukemia, the company announced [2] the completion of Phase 1, Step 3, evaluating the combination of AB8939 and venetoclax. The next step is to seek authorization from health authorities—based on a preliminary favorable opinion from the study’s Independent Data Monitoring Committee (IDMC)—to initiate Phase 4 of the study, which will evaluate the triple combination of AB8939, venetoclax, and azacitidine.

Regarding the Phase 3 program for masitinib in amyotrophic lateral sclerosis, which was approved in 2025 [3] but has not yet begun, the company will update the protocol and its implementation procedures, and will seek authorization from health authorities to resume this study after submitting a substantial amendment.

About AB23005 in ALS

The AB23005 study is a prospective, multicenter, randomized, double-blind, placebo-controlled, two-arm study conducted in patients with amyotrophic lateral sclerosis (ALS), designed to confirm the efficacy and safety of masitinib (at a dose of 4.5 mg/kg/day in combination with riluzole) compared to riluzole plus placebo after 48 weeks of treatment. The study will include 408 patients (randomized in a 1:1 ratio) with ALS who are experiencing normal disease progression (i.e., a functional decline of less than 1.1 points per month) and who have not experienced a complete loss of function (i.e., a score of at least 1 on each of the 12 items of the ALSFRS-R scale). U.S. patients receiving edaravone will also be eligible to participate in the study, as the use of this medication constitutes a stratification factor.

About AB18001 in AML

The AB18001 study, titled "A Phase 1/2 Study to Evaluate the Safety, Pharmacokinetics, and Efficacy of AB8939 Administered Intravenously Daily in Patients with Relapsed/Refractory Acute Myeloid Leukemia," is designed in several phases. The first part is a dose-escalation study designed to assess the safety and tolerability of AB8939 and to determine the recommended dose for the Phase 2 expansion study.

The objective of the Phase 1 study is to determine the maximum tolerated dose (MTD) for the different treatment regimens with AB8939.

Phase 1: Determination of the MTD after 3 consecutive days of treatment with AB8939 alone.
Phase 2: Determination of the MTD after 14 consecutive days of treatment with AB8939 alone.
Phase 3: Determination of the MTD after 14 consecutive days of treatment with AB8939 in combination with venetoclax.
Phase 4: Determination of the maximum tolerated dose (MTD) after 14 consecutive days of treatment with AB8939 in combination with venetoclax and azacitidine.

(Press release, AB Science, JUL 10, 2026, View Source [SID1234669139])