Positive recommendation of the Data and Safety Monitoring Board to continue the Phase 2 study evaluating masitinib in combination with isoquercetin in Covid-19

PRESS RELEASE POSITIVE RECOMMENDATION OF THE DATA AND SAFETY MONITORING BOARD TO CONTINUE THE PHASE 2 STUDY EVALUATING MASITINIB IN COMBINATION WITH ISOQUERCETIN IN COVID-19 Paris, 28 April 2022, 8am CET AB Science SA (Euronext - FR0010557264 - AB) today announced the continuation of the P hase 2 study evaluating masitinib in combination with isoquercetin in COVID-19, following the recommendation of the Data and Safety Monitoring Board (DSMB). This randomized (1:1), open-label, phase 2 study (AB20001) is designed to evaluate the safety and efficacy of masitinib plus isoquercetin in hospitalised patients with moderate COVID-19 (WHO 7-point ordinal scale level 4) or severe COVID-19 (level 5). The study is planned to recruit 200 patients (over 18 years of age with no upper age limit). The primary objective is to improve the clinical status of patients after 15 days of treatment, as measured by the WHO 7-point ordinal scale. The interim analysis was conducted with one third of the patients evaluated, as planned. The purpose of the interim analysis was to assess the safety and efficacy of the treatment. The DSMB recommends continuing the study without restrictions in moderate patients (le vel 4, i.e. hospitalized patients with oxygen supply <6 L/min with SpO2 maintained ≥92%). In line with this recommendation, AB Science has made the decision to continue the study only in moderate patients. The study is therefore now planned to include 200 patients at level 4 of the ordinal scale. Professor Olivier Hermine, President of the Scientific Committee of AB Science said: “This recommendation is in line with our expectation since our opinion is that better efficacy ca n be achieved when treatment is initiated before patients reach a severe stage of the disease. The combination of masitinib with isoquercetin is based on sound scientific rationale and remains a credible option in the search for treatments to prevent progression to severe and life-threatening disease”. A second Phase 2 study (study AB21002) evaluating the antiviral activity of ma sitinib is also ongoing. This study includes non-hospitalized patients with risk factors, as well as hospitalized patients wi th moderate COVID-19, the latter category being similar to AB20001. About the study primary endpoint The 7-point ordinal scale for clinical status is: 1. Not hospitali zed, no limitations on activities; 2.Not hospitalized, limitation on activities; 3. Hospitalized, not requiring suppleme ntal oxygen; 4. Hospitalized, requiring supplemental oxygen; 5. Hospitalized, on non-invasive ventilation or high flow oxygen devices; 6. Hospitalized, on invasive mechanical ventilation or ECMO; 7. Death. About AB Science Founded in 2001, AB Science is a pharmaceutical company specializing in the res earch, development and commercialization of protein kinase inhibitors (PKIs), a class of targeted proteins whose action are key in signaling pathways within cells. Our programs target only diseases with high unme t medical needs, often lethal with short term survival or rare or refractory to previous line of treatment. AB Science has developed a proprietary portfolio of molecules and the Com pany’s lead compound, masitinib, has already been registered for veterinary medicine and is developed in human medicine in oncology, neurological diseases, inflammatory diseases and viral diseases. The company is headq uartered in Paris, France, and 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, e vents, 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 stateme nts are subject to numerous risks and uncertainties that are difficult to predict and generally beyond the control of AB Science and which may imply that results and actual events significantly differ from those expressed, ind uced or anticipated in the forward-looking information and statements. These risks and uncertainties include the uncertainties related to 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 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 the 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 [email protected] Media Relations – USA RooneyPartners Kate Barrette [email protected] +1 212 223 0561 Media Relations – France NewCap Arthur Rouillé [email protected] +33 (0)1 44 71 00 15

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