Masitinib mesylate

PRESS RELEASE AB SCIENCE ANNOUNCES THE SUCCESSFUL COMPLETION OF A EUR 2.8 MILLION PRIVATE PLACEMENT AB SCIENCE IS FULLY FINANCED TO FINISH PHASE 1 OF AB8939 IN AML AND TO EXECUTE AN EXPANSION PHASE TO MAXIMIZE CHANCE OF SUCCESS OF FUTURE REGISTRATION STUDY Paris, October 17, 2025, 8am AB Science S.A. (the “Company” or “AB Science”, Euronext – FR0010557264 – AB) announces today the successful completion of a capital increase of a total gross amount of EUR 2.8 million subscribed by a limited number of investors (the “Private Placement”). The Private Placement is not subject to a prospectus requiring an approval from the French Financial Market Authority (Autorité des Marchés Financiers – the “AMF”). In accordance with Article 1.5.(ba) of the Regulation (EU) 2017/1129 of the European Parliament and of the Council of June 14, 2017, as amended (the “Prospectus Regulation”), the Company will file with the AMF a document containing the information set out in Appendix IX of the Prospectus Regulation (the “Information document”), copies of which will be available free of charge on the Company’s website at www.ab-science.com and on the AMF’s website at www.amf-france.org. Use of proceeds The Company intends to use the net proceeds of the Private Placement to finance its ongoing activities, with a focus on the clinical development of the AB8939 program. The next step for the AB8939 development program is to finish phase 1 in combination therapy and to launch an expansion study in around 15 AML (acute myeloid leukemia) patients eligible to AB8939 + Venetoclax at the right dose. The expansion phase is expected to generate robust preliminary evidence of efficacy in the AML label to support the registration trials. This transaction strengthens the Company’s cash position and enables it to cover its financing needs in 2025 and beyond the next 12 months, taking into account the explanations set out in section 2.1.5 (note 2) of the first-half 2025 financial report. Terms and conditions of the Private Placement The Private Placement, for a total amount of EUR 2.8 million (including share issue premium), was carried out through the issuance, without preferential subscription rights and without a priority subscription period, of 2,477,877 new ordinary shares of the Company (the “New Shares”), each with one share warrant attached (a “BSA” and, together with the New Share to which it is attached, an “ABSA”), as part of a share capital increase with cancellation of shareholders’ preferential subscription rights for the benefit of investors within the category of persons defined by the 16th resolution of the Combined General Meeting of the Company’s shareholders of June 30, 2025 (the “General Meeting”), in accordance with article L. 225-138 of the French commercial code (the “Private Placement”). The issue of the ABSAs, representing approximately 3.52% of the Company’s share capital, on a non-diluted basis, before completion of the Private Placement, and 3.40% of the Company’s share capital, on a non-diluted basis, after completion of the Private Placement, was decided on October 16, 2025 by the Chief Executive Officer, pursuant to the delegation of competence granted to him by the board of directors dated October 16, 2025, pursuant to the delegation of competence granted to it under the 16th resolution of the General Meeting . The issue price of one ABSA is EUR 1.13 (including share issue premium), representing a facial discount of 24.99% (i.e. EUR 0.3765) to the volume-weighted average price of the AB Science shares on the regulated market of Euronext Paris (“Euronext Paris”) over the three trading days preceding the setting of such issue price, i.e. October 14 to 16, 2025 (the “3-day VWAP”). The issue price of an ABSA, including the theoretical value of the BSA attached to it (as described below, together with the exercise price of such BSA) represents a total 18.02% discount per AB Science share to the 3-day VWAP, consistent with the maximum discount authorized by the General Meeting pursuant to its 16th resolution. Terms and conditions of the BSA One BSA is attached to each New Share. Five BSA entitle their holder to subscribe to three new ordinary shares of the Company at a price of EUR 1.72 per ordinary share. The BSAs may be exercised at any time within 60 months of their issuance. In the event all BSAs are exercised, a total number of 1,486,726 additional ordinary shares of the Company will be issued, representing additional total proceeds of approximately EUR 2.6 million. The theoretical value of each BSA, assuming a volatility of 28.932%1 and based on closing price as of October 16, 2025, is equal to EUR 0.1860 using Black & Scholes model. The BSAs will be immediately detached (détachés) from the New Shares upon issuance and will not be listed. Impact of the Private Placement on the Company’s shareholding Following the issuance of the ABSAs, the Company’s total share capital will be EUR 729,474.72 (or EUR 744,341.98 in the event of exercise of all BSAs). It will be comprised of 66,184,793 ordinary shares (or of 67,671,519 ordinary shares in the event of exercise of all BSAs) with a par value of EUR 0.01. There will be no change on the number of preferred shares. To the Company’s knowledge, immediately prior to completion of the Private Placement and after completion of the Private Placement, the breakdown of the Company's share capital is as follows: ShareholdersBefore the capital increaseAfter the capital increase (before exercising the warrants)After the capital increase and exercise of the warrantNumber of shares ( 1) %Diluted base ( 2)Number of shares ( 1) %Diluted base ( 2)Number of shares ( 1) %Diluted base ( 2)A. Moussy7 345 39610.42%16.72%7 345 39610.07%16.27%7 345 3969.87%16.02%AMY SAS (3)12 273 00017.42%13.52%12 273 00016.82%13.16%12 273 00016.49%12.95%Subtotal concert A. Moussy19 618 39627.84%30.23%19 618 39626.89%29.43%19 618 39626.36%28.97%Other investors members of the concert2 610 9363.71%5.84%2 610 9363.58%5.69%2 610 9363.51%5.60%Actions in the pact1 123 9021.59%4.21%1 123 9021.54%4.09%1 123 9021.51%4.03%Actions outside the pact1 487 0342.11%1.64%1 487 0342.04%1.59%1 487 0342.00%1.57%Total concert22 229 33231.54%36.08%22 229 33230.47%35.12%22 229 33229.86%34.57%Other investors above 5%6 888 6109.78%8.88%6 888 6109.44%8.64%6 888 6109.25%8.50%Other investors41 351 65358.68%55.05%43 829 53060.08%56.24%45 316 25660.88%56.93%Total70 469 595100.00%100.00%72 947 472100.00%100.00%74 434 198100.00%100.00% (1) All classes of shares are affected. The number of ordinary shares amounts to 63,706,916 before the Private Placement, 66,184,793 after the Private Placement (but before exercise of the BSAs), and 67,671,519 after the Private Placement and exercise of the BSAs.(2) The diluted basis takes into account the exercise of all instruments giving access to the capital, the definitive allocation of all free shares and the conversion of all preferred shares into ordinary shares (aiming for the highest theoretical dilution).(3) AMY SAS is a company controlled by A. Moussy. On the basis of the share capital of the Company immediately after completion of the Private Placement, the interest of a shareholder who held 1.00% of the Company’s share capital prior to the above-mentioned capital increase and who did not subscribe to it now stands at 0.97% on a non-diluted basis and 0.76% on a diluted basis.diluted basis. Admission to trading of the New Shares The New Shares are expected to be admitted to trading on the regulated market of Euronext Paris on October 22, 2025. The New Shares will be subject to the provisions of the Company’s by-laws and will be assimilated to existing shares upon final completion of the Private Placement. They will bear current dividend rights and will be admitted to trading on the same listing line as the Company’s existing shares under the same ISIN code FR0010557264 – AB. Lock-up commitments The Company has signed a lock-up commitment (to the benefit of the investors) pursuant to which it has agreed to a lock-up period of 45 calendar days from the date of the settlement and delivery of the Private Placement, subject to certain customary exceptions. The directors and officers of the Company have signed a lock-up commitment pursuant to which they have agreed to a lock-up period of 90 calendar days from the date of the settlement and delivery of the Private Placement, subject to certain customary exceptions. Indicative timetable October 16, 2025Decisions of the Board of Directors deciding the principle of the Private Placement.October 16, 2025Decisions of the Chief Executive Officer setting the terms and conditions of the Private Placement (including the subscription price of the ABSAs and the gross amount of the Private Placement).October 17, 2025Publication of this press release.Publication of the Information Document.October 22, 2025Publication of the Euronext notice of admission of the New Shares to trading on Euronext Paris. October 22, 2025Settlement-delivery of the ABSAs - Detachment of the BSA - Start of trading of the New Shares on Euronext Paris. Risk factors AB Science draws the attention of the public to the risk factors relating to the Company and its business described in its annual management reports and press releases, which are available free of charge on the Company's website (www.ab-science.com). In addition, the main risks specific to securities are as follows: The existing shareholders who do not participate in the Private Placement will see their shareholding in the share capital of AB Science diluted, and this shareholding may also be diluted in the event of exercise of the BSA, as well as in the event of new securities transactions. The volatility and liquidity of AB Science shares could fluctuate significantly. The market price of the Company's shares may fluctuate and fall below the subscription price of the shares issued in the context of the Private Placement. The sale of Company shares may occur on the secondary market, after the Private Placement, and have a negative impact on the Company share price. About masitinib Masitinib is a novel oral tyrosine kinase inhibitor that is being developed to target mast cells and macrophages, key immune cells, through inhibition of a limited number of kinases. Due to its unique mode of action, the Company believed that masitinib can be developed in a wide range of diseases, including oncology, inflammatory diseases, and certain central nervous system diseases. In oncology, through its immunotherapy activity, masitinib may have an effect on survival, alone or in combination with chemotherapy. Through its activity on mast cells and microglial cells and therefore its inhibitory effect on the activation of the inflammatory process, masitinib may have an effect on the symptoms associated with certain inflammatory and central nervous system diseases. About AB8939 AB8939 is a new synthetic microtubule-destabilizing drug candidate. Preclinical data suggests that AB8939 has broad anticancer activity, with a notable advantage over standard chemotherapies that target microtubules of being able to overcome P-glycoprotein (Pgp) and myeloperoxidase (MPO) mediated drug resistance. Development of drug resistance often restricts the clinical efficacy of microtubule-targeting chemotherapy drugs (for example, taxanes and vinca alkaloids); thus, AB8939 has the potential to be developed in numerous oncology indications. 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 are key in signaling pathways within cells. Our programs target only diseases with high unmet 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 Company’s lead compound, masitinib, has already been registered for veterinary medicine and is being developed in human medicine in oncology, neurological diseases, inflammatory diseases and viral diseases. The company is headquartered in Paris, France, and listed on Euronext Paris (ticker: AB). Further information is available on AB Science’s website: www.ab-science.com. Disclaimer This press release and the information contained herein do not constitute an offer to subscribe or purchase, or the solicitation of an order to purchase or subscribe, for the New Shares in the United States of America or in any other jurisdiction. Securities may not be offered or sold in the United States of America absent registration under the U.S. Securities Act or an exemption from registration under the U.S. Securities Act. AB Science does not intend to make a public offering of the New Shares in the United States of America or in any other jurisdiction. The distribution of this press release may be subject to legal or regulatory restrictions in certain countries. Persons in possession of this press release should inform themselves of and observe any local restrictions. The information contained herein is subject to change without notice. This information contains forward-looking statements, which are not guarantees of future performance. These statements are based on the current expectations and beliefs of AB Science’s management and are subject to several factors and uncertainties that could cause actual results to differ materially from those described in the forward-looking statements. AB Science and its affiliates, directors, officers, employees, consultants or agents do not undertake, and are not under any obligation, to release any updates to any forward-looking statement or to revise any forward-looking statement. For additional information, please contact: AB Science Financial communication and public relationsinvestors@ab-science.com 1Based on the volatility over the last 12 months of the Euronext Next Biotech index. Attachment AB Science - October 2025 Press Release VEng VF