PRESS RELEASE

AB SCIENCE PROVIDES AN UPDATE ON ITS CLINICAL PROGRAM

• AB SCIENCE SECURES EUR 25 MILLION CLINICAL TRIAL INSURANCE FOR ITS PHASE III TRIAL IN AMYOTROPHIC LATERAL SCLEROSIS
  THE POLICY COVERS UP TO EUR 25 MILLION OF TRIAL COSTS IN THE EVENT OF CLINICAL FAILURE, WITH ZERO DEDUCTIBLE
  THIS RISK-TRANSFER STRUCTURE PROTECTS SHAREHOLDER CAPITAL AND SIGNALS INSTITUTIONAL CONFIDENCE IN THE MASITINIB PROGRAMME
• AB SCIENCE IMPLEMENTS A VOLUNTARY TEMPORARY HALT IN EUROPE OF ITS CLINICAL TRIALS, BEFORE THE IMPLEMENTATION OF A STRATEGIC REORGANIZATION

Paris, April 16, 2026, 7pm CET

AB Science SA (Euronext - FR0010557264 - AB) provides an update on its clinical development program.

Insurance for phase 3 in ALS

AB Science has received a binding offer for a Clinical Trial Funding Insurance policy from Medical & Commercial International Ltd. (MCI), Lloyd’s Syndicate 1902, for its Phase III clinical trial AB23005, evaluating masitinib (AB1010) as an add-on therapy in Amyotrophic Lateral Sclerosis (ALS). The policy, effective from the date the first patient is enrolled, provides coverage for a limit of liability of EUR 25,000,000 and potentially up to EUR 39,000,000 against the full financial cost of clinical failure, with no deductible. This placement was arranged by Lloyd’s broker Acrisure Re UK, in conjunction with its European affiliate, Acrisure Re Netherlands.

Clinical Trial Funding Insurance (CTFI) is a specialized financial product that reimburses a biopharmaceutical company for the costs incurred in running a clinical trial, in the event that trial fails to meet its pre-defined, policy specific, success criteria (often aligned to the trial protocol end points). Phase III programs — the pivotal, large-scale studies required before regulatory approval — typically cost millions of euros and can fail for reasons entirely outside a sponsor’s control, including lack of efficacy, unexpected safety findings, regulatory actions, or supply chain disruptions. CTFI allows AB Science to transfer a significant portion of this financial risk to MCI in exchange for a one-time up-front premium.

The delivery of a CTFI binding quotation has been possible through MCI’s thorough diligence process reviewing past clinical data, real-life data, trial design and in-silico modelling. The CTFI will become effective (and the premium will be payable) when AB Science are ready to initiate its ALS Phase III clinical trial, and when AB Science will have mobilized the necessary financing for such study and the payment of the premium. The CFTI offer received is binding and may be activated until December 31st, 2026.

Alain Moussy, CEO and co-founder of AB Science, said “AB Science is very proud to be one of the first companies in the world to benefit from this CTFI for a phase 3 in ALS. ALS is considered one of the riskiest indications in the industry and this insurance is a mark of confidence in the probability of success of the masitinib program in ALS.”

James Banks, co-founder of MCI, said “We are thrilled to be able to support global drug development and facilitate lending through insurance. This approach, helps companies raise capital and reduce equity dilution through downside protection, leaving greater control and ownership in the hands of the innovator. AB Science has a truly exciting asset that has the potential to materially slow disease progression in ALS patients. Through extensive underwriting assessment on safety, efficacy and feasibility, we are proud to be able to support AB Science in their mission.”

Two scenarios are then possible: either the study is a success and the value generated will be large, or the study is a failure and AB Science will get the full cost of the phase 3 study back (excluding the premium).

This is a significant derisking of the ALS program and of AB Science.

The policy reimburses AB Science for all qualifying costs incurred in designing, implementing, and conducting the AB23005 trial — including contract research organization fees, drug manufacturing costs, clinical site costs, and wind-down expenses — in the event of a “Failure to Achieve”. This covers the following situations:

• Efficacy Failure: the phase 3 fails to meet the FDA or the EMA criteria of success, defined by the policy.
• Safety Failure: the drug raises unacceptable safety concerns in the ALS patient population.
• Recruitment Failure: inability to enroll or retain the required number of patients within the policy period.
• Regulatory Action (Clinical Hold): the FDA or an equivalent authority suspends or terminates the trial.
• GCP / Data Integrity Breach: protocol violations by a CRO or clinical investigator that render trial data unacceptable to regulators.
• Early Trial Termination: the Independent Data Monitoring Committee recommends stopping the trial on safety or efficacy grounds.
• Manufacturing (CMC) Issues: defects in drug production or supply chain disruption preventing trial completion.

For shareholders, this insurance structure delivers three concrete benefits.

• First, capital protection: a failed trial could destroy EUR 25 million of invested capital; the policy allows AB Science to recover up to EUR 25 million of those costs (excluding the premium) from the insurer, substantially limiting the financial damage to the company.
• Second, third-party validation: the insurance underwriters conduct rigorous independent due diligence before underwriting these policies, and their willingness to do so at a defined premium constitutes institutional confidence in the trial design, the regulatory pathway, and the underlying science.
• Third, improved capital efficiency: by capping the downside of the trial, the insurance lowers the company’s risk profile for debt and equity financing, potentially improving the terms under which AB Science can access capital to fund parallel activities.

Voluntary temporary halt of clinical trials in Europe

The recruitment of new patients in AB Science studies has been voluntarily halted while AB Science was negotiating with the insurer and was having on-going exchanges with European health authorities.

European health authorities raised questions on the resources of AB Science and its level of structuration to conduct clinical studies in Europe. AB Science submitted detailed responses to the agencies and is reviewing its strategic priorities, namely:

• To deprioritize development in mastocytosis and mast cell activation program. These two indications bare comparable clinical development costs as program in neurology but significantly less market potential.
• To pursue the phase 3 clinical development in multiple sclerosis and Alzheimer’s disease through partnerships. Maximizing the potential in these two indications required established sales and marketing capabilities, which AB Science does not have at this time.
• To prioritize AB Science clinical development program on the masitinib phase 3 in amyotrophic Lateral Sclerosis (ALS) and AB8939 phase 1 in acute myeloid leukemia (AML).

Given the current stage of its clinical pipeline, such temporary halt has no material impact on AB Science’s current operations. The phase 3 in ALS is yet to be started. The phase 1 of AB8939 recently completed its step 3 (Determination of the MTD after 14 consecutive days of treatment with AB8939 in combination with venetoclax) and initiation of step 4 (Determination of MTD after 14 consecutive days of treatment with AB8939 in combination with venetoclax and azacitidine) is pending regulatory approval.

However, for the launch of the ALS Phase III clinical trial and the pursuance of its AB8939 program, AB Science will strengthen its organization to meet the demands and address the concerns of the health authorities regarding the adequation of resources. The CFTI binding offer has contributed to this strategic prioritization, with a focus on the ALS Phase III clinical trial that has been de-risked.

About AB23005 in ALS

Study AB23005 is a prospective, multicenter, randomized, double-blind, placebo-controlled, two-arm study in patients with amyotrophic lateral sclerosis (ALS), to confirm the efficacy and safety of masitinib (at a dose of 4.5 mg/kg/day in combination with riluzole) as compared against riluzole in combination with placebo after 48 weeks of treatment. The study will include 408 patients (randomized 1:1) with ALS, with normal disease progression (i.e., functional decline of less than 1.1 points per month) and no total loss of function (i.e., a score of at least 1 on each of the 12 items of the ALSFRS-R score). US patients receiving edaravone will also be eligible to participate in the study, with the use of this drug being a stratification factor.

About AB18001 in AML

Study AB18001, titled ‘A Phase 1/2 Study to Assess the Safety, Pharmacokinetics, and Efficacy of Daily Intravenous of AB8939 in patients with Relapsed/Refractory Acute Myeloid Leukemia’, has a multi-stage design. The first part is a dose escalation study that aims to determine the safety and tolerability of intravenous AB8939, and to determine the recommended dose for the expansion study.

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

• Stage 1: Determination of the MTD after 3 consecutive days of treatment with AB8939 alone.
• Stage 2: Determination of the MTD after 14 consecutive days of treatment with AB8939 alone.
• Step 3: Determination of the MTD after 14 consecutive days of treatment with AB8939 in combination with venetoclax.
• Stage 4: Determination of MTD after 14 consecutive days of treatment with AB8939 in combination with venetoclax and azacitidine.

About AB Science

Founded in 2001, AB Science is a pharmaceutical company specializing in the research, development, and commercialization of protein kinase inhibitors (PKIs), a class of targeted proteins whose action is key in signaling pathways within cells. Our programs target only diseases with high unmet medical needs, which are often lethal with short-term survival or rare or refractory to previous lines of treatment.

AB Science has developed a proprietary portfolio of molecules, and the Company’s lead compound, masitinib, has already been registered for veterinary medicine and is being developed for human medicine in oncology, neurological diseases, inflammatory diseases, and viral diseases. The company is headquartered in Paris, France and is listed on Euronext Paris (ticker: AB).

Further information is available on AB Science’s website: www.ab-science.com.

Forward-looking Statements - AB Science

This press release contains forward-looking statements. These statements are not historical facts. These statements include projections and estimates as well as the assumptions on which they are based, statements based on projects, objectives, intentions, and expectations regarding financial results, events, operations, future services, product development, and their potential or future performance.

These forward-looking statements can often be identified by the words "expect", "anticipate", "believe", "intend", "estimate" or "plan" as well as other similar terms. While AB Science believes these forward-looking statements are reasonable, investors are cautioned that these forward-looking statements are subject to numerous risks and uncertainties that are difficult to predict and generally beyond the control of AB Science, which may imply that results and actual events significantly differ from those expressed, induced, or anticipated in the forward-looking information and statements. These risks and uncertainties include uncertainties related to the product development of the Company, which may not be successful, or to the marketing authorizations granted by competent authorities, or, more generally, any factors that may affect the marketing capacity of the products developed by AB Science, as well as those developed or identified in the public documents published by AB Science. AB Science disclaims any obligation or undertaking to update forward-looking information and statements, subject to the applicable regulations, in particular articles 223-1 et seq. of the AMF General Regulations.

For additional information, please contact:

AB Science
Financial Communication & Media Relations
investors@ab-science.com