OSE Immunotherapeutics

Share Issue/Capital Change • Sep 16, 2015

OSE Pharma enters Euronext Index CAC® Small, CAC® Mid & Small and CAC® All-Tradable

Paris, September 16 th 2015, 5:45 PM – OSE Pharma SA (ISIN: FR0012127173; Mnemo: OSE), a biotechnology company based in France that is developing T-specific immunotherapy treatments against invasive and metastatic cancers, is pleased to announce that the company has been admitted to CAC® Small, CAC® Mid & Small and CAC® All-Tradable indices on Euronext in Paris. The decision has been taken by the Euronext steering committee, "Conseil Scientifique des Indices", and will be effective September 18th post market.

Press Contacts

OSE Pharma sa Dominique Costantini, CEO dominique.costantini@osepharma.com Mob +33 6 13 20 77 49

Alexis Peyroles, CFO Alexis.peyroles@osepharma.com Mob : +33 6 11 51 19 77

Citigate Dewe Rogerson Laurence Bault / Lucie Larguier +33 1 53 32 84 78 laurence.bault@citigate.fr

Alize RP Florence Portejoie / Caroline Carmagnol +33 6 47 38 90 04 / + 33 1 44 54 36 61 osepharma@alizerp.com

Follow us on Twitter @OSEPharma

About OSE PHARMA (www.osepharma.com)

OSE Pharma is a European cancer immunotherapy company with a multi-epitope technology named Memopi® that directs the body's immune system to generate a specific cytotoxic T response to prevent cancer cell growth.

OSE Pharma's lead product, Tedopi®, combines 10 "neo-epitopes" directed against five tumour associated antigens. In its most advanced application it is about to enter a international pivotal Phase 3 study (Europe and the US) in patients with advanced non-small cell lung cancer (NSCLC) who express HLA-A2 and who have failed first line therapy. Tedopi® has orphan drug status in the USA and is considered as personalised medicine in Europe in HLA-A2 positive patients.

Tedopi® could also be developed in a new Phase 2 clinical trial in combination in NSCLC with another immunotherapy treatment (like check-point inhibitors) or targeted therapies. It could also be developed in other cancer indications (ovarian, prostate, colon, breast).

Tedopi® targets five tumour associated antigens (TAA), selected because their presence is linked to a poor prognosis and the severity of various cancers. Tedopi® contains a total of ten optimised epitopes, or "neoepitopes", designed on the binding of HLA-A2 and TCR. These neo-epitopes generate strong specific T cytotoxic responses that fight cancer and prevent tumour escape.

OSE Pharma is listed on Euronext in Paris (ISIN: FR0012127173 ; Mnemo : OSE).

Disclaimer:

This press release may expressly or implicitly contain forward-looking statements relating to OSE Pharma and its activity. Although OSE Pharma's management believes that the expectations reflected in these forward-looking statements are reasonable, investors are cautioned that such statements are related to known or unknown risks, uncertainties and other factors that could lead actual results, financial conditions, performance or achievements to differ materially from OSE Pharma's results, financial conditions, performance or achievements expressed, projected or implied by such information and forward-looking statements.

Other than as required by applicable law (article 223-1 et seq of the General Regulation of the AMF), OSE Pharma issues this press release at the date hereof and does not undertake any obligation to update or revise any forward-looking information or statements.

These risks and uncertainties include among other things, the uncertainties inherent in future clinical data and analysis, including post marketing, decisions by regulatory authorities, such as the FDA or the EMA, regarding whether and when to approve any drug, and other matters that could affect the availability or commercial potential of such product candidates, the absence of guarantee that the product candidates if approved will be commercially successful, the future approval and commercial success of therapeutic alternatives, For a description of risks and uncertainties which could lead to discrepancies between actual results, financial condition, performance or achievements and those contained in the forward-looking statements, please refer to Chapter 4 "Risk Factors" of the company's Documents de Base filed with the AMF under number I. 14-056 on September, 17th 2014 and Chapter 2 "Risk Factors related to the Offer" in the prospectus approved by the AMF under number 15-078 on 6th March 2015, which can be found on the websites of the AMF (www.amf-france.org) and of OSE Pharma (www.osepharma.com).