Why it matters: The move turns a temporary suspension announced in April into a broader pipeline reset, following questions from European regulators about whether AB Science had sufficient resources and organisational structure to conduct its trials.
What’s new: The Paris-based company will discontinue:
- A phase 2 trial of masitinib in mast cell activation syndrome.
- A phase 3 trial in mastocytosis.
- A phase 3 trial in progressive forms of multiple sclerosis.
Patient recruitment in the studies had already been suspended. AB Science said their termination was not linked to safety concerns and that it would close the trials in line with regulatory requirements.
Backstory: In April, AB Science voluntarily halted recruitment across its European studies while talking to regulators and reviewing its priorities.
- At the time, the company said European authorities had raised questions about its resources and organisational structure. It planned to deprioritise mastocytosis and mast cell activation syndrome, while seeking partners to continue development in multiple sclerosis and Alzheimer’s disease.
What’s next: AB Science will now direct its internal clinical resources toward two programmes:
- Masitinib in amyotrophic lateral sclerosis (ALS): Masitinib is an oral tyrosine kinase inhibitor designed to reduce neuroinflammation by targeting immune cells including mast cells, macrophages and microglia. The planned 408-patient phase 3 trial will test masitinib alongside riluzole over 48 weeks. Although regulators approved the study in 2025, recruitment has not started. AB Science now plans to revise the protocol and implementation procedures before seeking permission to begin the trial.
- AB8939 in acute myeloid leukemia (AML): AB8939 is an intravenously administered microtubule-disrupting agent designed to kill malignant blood cells, including cells resistant to commonly used microtubule-targeting drugs. The company is seeking regulatory clearance to test AB8939 in a triple combination with venetoclax and azacitidine after completing the venetoclax combination stage of its phase 1 trial.
Zoom in: Six heavily pretreated AML patients received AB8939 plus venetoclax in the completed phase 1 stage. Four responded, including one incomplete blood-count recovery remission and three partial responses, while the other two had stable disease. No dose-limiting toxicities were reported.
Also notable: AB Science has raised €5.5m through two private placements since April. The first, worth €3.2m, was mainly intended to support AB8939, while a €2.3m placement completed in July prioritised both AB8939 in AML and masitinib in ALS. The company said each transaction extended its financing horizon beyond 12 months. However, €5.5m remains a modest sum relative to the cost of advancing an oncology programme and launching a 408-patient phase 3 ALS trial.
- The company has also received a binding offer for insurance covering €25m – and potentially up to €39m – of qualifying costs if the ALS phase 3 trial fails. However, the policy will only become effective once AB Science has financed the study, paid the premium and enrolled its first patient.
Between the lines: The clinical reset comes days after AB Science appointed longtime shareholder Stéphane Ledermann as chairman and CEO, replacing co-founder Alain Moussy, who remains on the board. Ledermann has been tasked with reviewing the company’s operations, assets and prospects. AB Science expects to present a new strategic roadmap in the autumn.
The bottom line: AB Science is shrinking its near-term ambitions to match its resources. Hopefully, investors will believe in this new direction and change the trajectory of a stock that has lost 51% of its value since the beginning of 2026.
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