Onxeo

Report Publication Announcement • May 4, 2016

Publication of 2015 Reference Document

Paris (France), Copenhagen (Denmark), May 4, 2016 – Onxeo S.A. (Euronext Paris, Nasdaq Copenhagen: ONXEO), an innovative company specializing in the development of orphan oncology therapeutics, announced the publication of the Company's 2015 Reference Document.

The 2015 Reference Document, registered with the French Market Authorities (Autorité des Marchés Financiers) on April 29, 2016, is available to the public free of charge upon request, as per current legal regulations, at Onxeo's headquarters - 49 Boulevard du Général Martial Valin, 75015 Paris - and on the Company's website: http://www.onxeo.com/en/investisseurs/.

The annual financial report, the report of the Chairman of the Board of Directors on corporate governance and internal control and risk management procedures as well as the related auditors' reports and information on the fees paid to the statutory auditors in 2015 are included in this Reference Document.

About Onxeo

Onxeo is a leading developer of orphan oncology drugs. The Company is focused on developing innovative therapeutics for rare cancers, one of the fastest growing markets in the healthcare industry with high, unmet medical needs. Onxeo's comprehensive portfolio features a broad orphan oncology pipeline, with three independent programs in advanced clinical development, including Onxeo's first approved orphan oncology drug, Beleodaq®. In addition, Onxeo has successfully developed and registered two non-cancer products which are currently being commercialized in the U.S. and Europe. Onxeo's vision is to become a global leader and pioneer in oncology, with a focus on orphan or rare cancers, by developing advanced, effective, and safe therapeutics designed to improve the lives of patients. The Company is headquartered in Paris, France and has approximately 50 employees. Onxeo is listed on Euronext in Paris, France (Ticker: ONXEO, ISIN Code: FR0010095596) and Nasdaq Copenhagen, Denmark (Ticker: ONXEO).

Onxeo orphan oncology products at the advanced development stage are:

• Livatag® (Doxorubicin Transdrug™): Currently being evaluated in a Phase III trial (ReLive) in patients with hepatocellular carcinoma (primary liver cancer); and in combination with other cancer agents in first-line HCC
• Beleodaq® (belinostat): FDA-approved in the U.S. in 2014 under the agency's accelerated approval program as a second-line treatment for patients with peripheral T-cell lymphoma (PTCL) and currently marketed by Onxeo's partner in the U.S., Spectrum Pharmaceuticals; belinostat in combination with other cancer agents is currently in development in first-line treatment for patients with PTCL (BelCHOP) and in other solid tumors
• AsiDNA : the first-in-class siDNA (signal interfering DNA) which has successfully undergone a proof-of-concept Phase 1/2a trial in metastatic melanoma
• Validive® (Clonidine Lauriad®): Positive final results from a Phase II trial in head and neck cancer patients with severe oral mucositis;

Learn more by visiting www.onxeo.com.

To receive our press releases and newsletters, please register on: http://www.onxeo.com/en/newsletter/ Follow us on Twitter: @Onxeo_

Disclaimer

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 and does not undertake to update any forward-looking statements contained herein as a result of new information, future events or otherwise. For a discussion of risks and uncertainties which could cause actual results, financial condition, performance or achievements of Onxeo to differ from those contained in the forward-looking statements, please refer to the Risk Factors ("Facteurs de Risque") section of the 2015 Reference Document filed with the AMF on April 29, 2016, which is available on the AMF website (http://www.amf-france.org) or on the company's website (www.onxeo.com).

Contact:

Nathalie Delair-Trepo Investor Relations, Onxeo investors@onxeo.com + 33 1 45 58 76 00

Caroline Carmagnol /Florence Portejoie – Alize RP (France) onxeo@alizerp.com +33 6 64 18 99 59 / +33 6 47 38 90 04

Kirsten Thomas / Lee Roth – The Ruth Group (U.S.) kthomas@theruthgroup.com / lroth@theruthgroup.com +1 508 280 6592 / +1 646 536 7012