Clinical development of AsiDNA™ continues in phase 1 study DRIIV-1

• Activity of AsiDNA™ demonstrated through the marked activation of its cellular targets enabling the determination of active doses and favorable tolerance profile
• Impending initiation of a phase 1b study in combination with platinum-based chemotherapy and paclitaxel; preliminary results expected before year-end 2019

New lead compound sourced from platON™ ready to enter preclinical proof-of-concept studies

Cash position of €11.3 million at December 31, 2018 and new equity financing negotiated to ensure cash runway into Q2 2020

Paris (France), March 12, 2019 – 6.00 pm CET – Onxeo S.A. (Euronext Paris, NASDAQ Copenhagen: ONXEO – FR0010095596), (“Onxeo” or “the Company”), a clinical-stage biotechnology company specializing in the development of innovative drugs targeting tumor DNA Damage response (DDR) in oncology, in particular against rare or resistant cancers, today reported its consolidated full-year financials, as of December 31, 2018, and provided a business update.

Judith Greciet, Chief Executive Officer of Onxeo, said: “2018 was marked by major achievements that confirmed the potential of our unique approach to DNA Damage response (DDR) with our first-in-class lead drug candidate AsiDNA™. In terms of development, we obtained remarkable data from several preclinical studies of AsiDNA™ in combination with other cancer treatments such as chemotherapy and PARP inhibitors, especially on tumor cell lines resistant to PARP inhibitors. We also identified predictive biomarkers of response to AsiDNA™, opening the way for its use in personalized medicine.

From a clinical standpoint, our phase 1 dose escalation study, DRIIV-1, of AsiDNA™ administered intravenously in advanced solid tumors continues at full speed and has already demonstrated the activity of AsiDNA™ through the activation of its tumor cell targets, with a good tolerance profile. We are now ready to start an extension Phase 1b study of AsiDNA™ in combination with chemotherapies, using the active doses determined in DRIIV-1. Preliminary results of this DRIIV-1b trial are expected before the end of the year and will be a major milestone for AsiDNA™.

In addition to our positive momentum with AsiDNA™, our first compound sourced from platON™ is ready to enter the preclinical proof-of-concept phase. This new candidate, which benefits from a differentiated set of features from AsiDNA™, will enlarge our pipeline and reinforce our unique positioning in the DDR field.”