AB Science reports first-half 2026 loss and cuts trials

09) -------------------------------------------------- ---------- --------- In thousands of euros 30/06/2026 31/12/2025 -------------------------- ---------- ---------- Cash and cash equivalents 8,980 10,179 Total assets 18,901 24,525 -------------------------- ---------- ---------- Shareholders' equity (22,454) (17,198) -------------------------- ---------- ---------- Non-current liabilities (25,223) (26,908) Trade payables (9,155) (9,300) Current liabilities (15,323) (14,815) -------------------------- ---------- --------- KEY CLINICAL DEVELOPMENT EVENTS DURING THE FIRST HALF OF 2026 AND SINCE 30 JUNE 2026 Update on the development plan following a sponsor inspection on Good Clinical Practice Following a Good Clinical Practice inspection conducted from 21 to 25 September 2026 by three European health authorities, AB Science is revising its operational plan.

The final inspection report is expected before the end of the year. The preliminary findings support management in its priority of establishing a new quality management system. The finalisation of this system and its external audit are planned by the end of 2026, before clinical trials resume. AB Science anticipates resuming the Phase 1 study in acute myeloid leukaemia (AB8939) in the first quarter of 2027.

The resumption of the Phase 3 study in amyotrophic lateral sclerosis (masitinib) is planned for the fourth quarter of 2027. This timeframe will make it possible to optimise the design and methodology of these two studies. The masitinib programme in sickle cell disease, sponsored by AP-HP, would not be affected and is expected to start in early 2027.

In addition, as announced in July 2026, the Company announced that three clinical studies considered non-priority at this stage, and whose recruitment 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 Company specified that the discontinuation of these studies was not related to any safety concern regarding masitinib.

Clinical trial insurance of EUR25 to EUR39 million obtained for the Phase 3 study in Amyotrophic Lateral Sclerosis AB Science announced that it had received a firm offer to underwrite a clinical trial financing insurance policy from Medical & Commercial International Ltd. (MCI), Lloyd's Syndicate 1902, for its pivotal Phase III trial AB23005 evaluating masitinib (AB1010) in combination with standard of care in amyotrophic lateral sclerosis (ALS -- Lou Gehrig's disease). The placement was arranged by Acrisure Re UK, in collaboration with its subsidiary Acrisure Re Netherlands.

The policy provides coverage with no deductible, with a liability limit of EUR25 million that can be increased to EUR39 million, intended to cover all financial costs associated with a clinical failure. It takes effect on the date of enrolment of the first patient, subject to AB Science securing the financing required for the study and to payment of the premium of approximately EUR8 million (an amount including the insurance premium, taxes and brokerage fees, for a liability limit of EUR25 million; this premium may amount to approximately EUR13 million for a liability limit of EUR39 million).

The covered events include an efficacy failure according to FDA/EMA criteria, a safety failure, a recruitment failure, a regulatory suspension, a breach of GCP or of data integrity, early termination recommended by the independent committee, as well as manufacturing (CMC) issues.

This structure represents a significant reduction in the risk profile of the ALS programme and of the Company, with three benefits for shareholders: (i) protection of the capital invested up to EUR25 million in the event of failure; (ii) external validation of the trial design and regulatory pathway through the independent due diligence conducted by the insurer; (iii) improved capital efficiency and better conditions of access to debt and equity financing.

Identification of a potential biomarker to assess the activity of masitinib on the pathological involvement of microglia in amyotrophic lateral sclerosis In February 2026, AB Science announced the identification of a potential biomarker to assess the activity of masitinib on the pathological involvement of microglia in amyotrophic lateral sclerosis. The main characteristics of this newly identified biomarker are as follows - It is a blood (plasma) biomarker, which has the advantage of being easy to collect and of being accurately measured by ELISA (enzyme-linked immunosorbent assay). - It is produced by pro-inflammatory microglia.

- It activates microglia and astrocytes and is therefore an activator contributing to a harmful feedback loop of neuroinflammation. - It is also released by mast cells, thereby establishing a link between mast cells and microglia, which are the two main cellular targets of masitinib. - It predicts survival in ALS, which could explain why masitinib may prolong survival in certain specific patients. - Internal experiments showed that this biomarker was reduced by masitinib when mast cells and microglia were activated in vitro, highlighting the specific and potent activity of masitinib on mast cells and microglia.

Update on the Phase 1 study of AB8939 and completion of Stage 3 of Phase 1, evaluating the combination of AB8939 and Venetoclax in the treatment of relapsed or refractory acute myeloid leukaemia In January 2026, AB Science reviewed the status of the Phase 1 study of AB8939 and the fourth consecutive response with the combination of AB8939 and Venetoclax in patients with acute myeloid leukaemia (AML) associated with a very unfavourable genetic profile.

- The combination treatment was well tolerated, with no haematological toxicity or dose-limiting toxicity - The fourth patient had a complex karyotype including monosomy of chromosome 5 and a TP53 mutation, and was in third-line treatment.

The patient achieved a near-complete response after 14 days of treatment with AB8939 at 21 mg/m2 combined with Venetoclax - This is the fourth patient showing signs of response to the combination out of a total of 4 patients treated - The rate of partial response signals is 100% (4/4), including one patient in complete remission, one in near-complete response and two in partial response according to the clinical approach - The results were obtained after the first treatment cycle (14 days) in patients receiving third- or fourth-line treatment, two of whom had previously progressed on Venetoclax in combination with other chemotherapies - These four patients all have cytogenetic profiles that are very difficult to treat, including complex karyotype, TP53 mutation, NRAS mutation, monosomy 5 and MECOM rearrangement, which are generally associated with a poor prognosis due to the aggressive course of the disease and resistance to treatment - This diversity of responding patients appears to corroborate the mechanism of action of AB8939, which is able to destabilise microtubules while bypassing multidrug resistance and also by targeting cancer stem cells without eliminating non-tumour stem cells - These results support the positioning of AB8939 in patients with unfavourable genetics, complex karyotypes, TP53, NRAS and KRAS mutations, monosomy 5 and 7, and MECOM rearrangement, who represent the greatest unmet medical needs (MORE TO FOLLOW) Dow Jones Newswires October 09, 2026 12:23 ET (16:23 GMT) The statements in this document shall not be considered as an objective or independent explanation of the matters.

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