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PRESS RELEASE

Onxeo announces a Combined General Meeting

on August 17, 2022

Paris (France), July 12, 2022 - 07:00 pm CEST - Onxeo S.A. (Euronext Growth Paris: ALONX, Nasdaq First North

Copenhagen: ONXEO), hereafter "Onxeo" or the "Company", a clinical-stage biotechnology company specializing in the development of innovative drugs targeting tumor DNA Damage Response (DDR), today announces that it will hold a Combined General Meeting on Wednesday, August 17, 2022 at 2:00 pm CEST at the Renaissance Paris Nobel Tour Eiffel Hotel, 55 avenue Raymond Poincaré, 75116 Paris.

The meeting notice will be published in the BALO (Bulletin of Mandatory Legal Notices)on July 13, 2022 and will be available through this link.

Shareholders are notably invited to vote on the delisting of the Company from Nasdaq First North market in Copenhagen. This project would allow Onxeo to centralize its listing on Euronext Growth in Paris, the leading platform for biotech stocks in Europe, which would result in increased liquidity.

All documents relating to this general meeting will be uploaded on the Company's website in the General Meetingssection within the legal deadlines (15 days prior to the meeting), and shareholders will be notified by a company announcement.

For any question, please contact the Investor Relations team by e-mail at the dedicated address: ag2022@onxeo.com.

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About Onxeo

Onxeo (Euronext Paris, NASDAQ Copenhagen: ONXEO) is a clinical-stage biotechnology company developing innovative oncology drugs targeting tumor DNA-binding functions through unique mechanisms of action in the sought-after field of DNA Damage Response (DDR). The Company is focused on bringing early-stagefirst-in-class or disruptive compounds from translational research to clinical proof-of-concept, a value-creating inflection point appealing to potential partners.

platON is Onxeo's proprietary chemistry platform of oligonucleotides acting as decoy agonists, which generates new innovative compounds and broaden the Company's product pipeline.

AsiDNA, the first compound from platON, is a highly differentiated, clinical-stagefirst-in-class candidate in the field of DNA damage response (DDR) applied to oncology. Its decoy and agonist mechanism acting upstream of multiple DDR pathways results in distinctive antitumor properties, including the ability to prevent or abrogate tumor resistance to targeted therapies such as PARP inhibitors and strong synergy with tumor DNA-damaging agents such as radio-chemotherapy. AsiDNA is currently being studied in Europe in combination with other treatment modalities in difficult-to-treat solid tumors.

OX400 is a series of new drug candidates from platON, designed to be a next-generation PARP inhibitor acting on both the DNA Damage Response and the activation of immune response, without inducing resistance. The lead OX400 candidate is currently being optimized and is undergoing preclinical proof-of-concept studies, alone and in combination with immunotherapies.

For further information, please visit www.onxeo.com.

Forward looking statements

This communication expressly or implicitly contains certain forward-looking statements concerning Onxeo and its business. Such statements involve certain known and unknown risks, uncertainties and other factors, which could cause the actual results, financial condition, performance or achievements of Onxeo to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Onxeo is providing this communication as of this date

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