OSE Immunotherapeutics

Regulatory Filings • Mar 15, 2023

OSE Immunotherapeutics to Present Preclinical and Clinical Research Updates from its Pipeline and Platforms in Immuno-Oncology At the 2023 American Association for Cancer Research (AACR)

Nantes, France – March 15, 2023, 6:00 p.m. CET – OSE Immunotherapeutics SA (ISIN: FR0012127173; Mnemo: OSE) today announced it will be presenting five posters at the 2023 American Association for Cancer Research (AACR) Annual Meeting. AACR will be held in person in Orlando (Florida) on April 14-19.

Four communications will feature the latest research on pre-IND programs for the pioneering Myeloid and BiCKI® platforms, namely presentations on CLEC-1 (new myeloid immune checkpoint) and BiCKI®- IL7 (new bifunctional therapy targeting PD-1 and IL-7), and OSE-127 (anti-IL-7 receptor antagonist) hematology program. A fifth communication will feature biomarker analyses on BI 765063 (anti-SIRPα monoclonal antibody on CD47/SIRPα pathway) from the ongoing Phase 1 clinical trial in advanced solid tumors.

Nicolas Poirier, Chief Executive Officer of OSE Immunotherapeutics, comments: "We are very pleased to have several poster presentations at the prestigious AACR annual meeting. This selection by the international scientific community underlines the recognition and the interest in the quality of our R&D engines with preclinical and clinical innovative research programs. It further highlights our long-term commitment to fight against debilitating cancer and chronic diseases through the development of firstin-class innovative immunotherapies."

Poster presentation details:

Poster CLEC#1*

Title: ""CLEC-1 inhibitory myeloid checkpoint blockade enhances antitumor responses and tumor phagocytosis by macrophages"" Session Category: Immunology Session Title: Immune Checkpoints Session Date and Time: April 19, 2023 - 9:00 AM – 12:30 PM Location: Section 23 Poster Board Number: 2

Poster CLEC#2*

Title: "TRIM21 is a novel endogenous partner of the inhibitory myeloid checkpoint CLEC-1 involved in tumor antigen cross-presentation" Session Category: Immunology Session Title: Immune Checkpoints Session Date and Time: April 19, 2023 - 9:00 AM - 12:30 PM Location: Poster Section 23 Poster Board Number: 9

Poster BiCKI®-IL-7

Title: "Anti-PD-1/IL-7v bispecific antibody promotes TCF1+ stem like CD8 T cells expansion and longlasting in vivo efficacy" Session Category: Immunology Session Title: Therapeutic Antibodies 3 Session Date and Time: April 17, 2023 - 1:30 PM - 5:00 PM Location: Poster Section 24 Poster Board Number: 2

Poster OSE-127

Title: "CD127 is expressed by acute lymphoblastic leukemias and is efficiently targeted by the IL7Rantagonist OSE-127 through macrophage-mediated antibody dependent phagocytosis" Session Category: Immunology Session Title: Therapeutic Antibodies 3 Session Date and Time: April 17, 2023 - 1:30 PM - 5:00 PM Location: Poster Section 24 Poster Board Number: 4

In parallel, OSE-127 is currently being developed in clinical stage in partnership with Servier. Two clinical studies are ongoing in inflammatory diseases: a phase 2a study conducted in primary Sjögren's syndrome by Servier, for which completion of patient enrollment has been announced in November 2022, and a Phase 2 study conducted in ulcerative colitis by OSE Immunotherapeutics.

Poster BI 765063

Title: "Predictive response biomarkers from Phase I clinical trial of a SIRPalpha inhibitor BI765063, stand-alone and in combination with ezabenlimab, a PD1 inhibitor, in patients with advanced solid tumors"

Session Category: Clinical Research Excluding Trials Session Title: Biomarkers of Therapeutic Benefit 2 Date & Time: April 17, 2023 - 9:00 AM - 12:30 PM Location: Poster Section 39, Poster Board 3 Poster Number: 2129

BI 765063 is being evaluated in combination with Ezabenlimab in a Phase 1 expansion clinical trial in patients with microsatellite stable (MSS) advanced colorectal cancer and MSS advanced endometrium cancer whose disease relapsed after standard of care and who received no prior anti-PD-L1 inhibitors.

This Phase 1 clinical trial with BI 765063 is conducted by OSE Immunotherapeutics as part of a collaboration and license agreement under which Boehringer Ingelheim obtained exclusive rights to BI 765063.

* Collaborative academic program between OSE Immunotherapeutics and Dr Elise Chiffoleau's research teams (Center for Research in Transplantation and Translational Immunology (CR2TI), UMR1064, INSERM, Nantes University at Nantes University Hospital, https://cr2ti.univnantes.fr/research/team-1).

ABOUT OSE Immunotherapeutics

OSE Immunotherapeutics is a biotech company dedicated to developing first-in-class assets in immuno-oncology and immuno-inflammation. The Company's current well-balanced first-in-class clinical pipeline includes:

• Tedopi® (immunotherapy activating tumor specific T-cells, off-the-shelf, neoepitope-based): this cancer vaccine is the Company's most advanced product; positive results from the Phase 3 trial (Atalante 1) in Non-Small Cell Lung Cancer patients in secondary resistance after checkpoint inhibitor failure. Other Phase 2 trials, sponsored by clinical oncology groups, of Tedopi® in combination are ongoing in solid tumors.
• OSE-279 (anti-PD1): ongoing Phase 1/2 in solid tumors or lymphomas (first patient included). OSE-279 is the backbone therapy of the BiCKI® platform.
• OSE-127/S95011 lusvertikimab (humanized monoclonal antibody antagonist of IL-7 receptor) developed in partnership with Servier; ongoing Phase 2 in ulcerative colitis (sponsor OSE Immunotherapeutics) and ongoing Phase 2a in Sjögren's syndrome (sponsor Servier); ongoing pre-clinical research in leukemia (OSE Immunotherapeutics).
• FR-104/VEL-101 (anti-CD28 monoclonal antibody): developed in partnership with Veloxis Pharmaceuticals, Inc. in transplantation; ongoing Phase 1/2 in renal transplant (sponsor Nantes University Hospital); Phase 1 ongoing in the US (sponsor Veloxis Pharmaceuticals, Inc.).
• OSE-172/BI 765063 (anti-SIRPα monoclonal antibody on CD47/SIRPα pathway) developed in partnership with Boehringer Ingelheim in advanced solid tumors; positive Phase 1 dose escalation results in monotherapy and in combination, in particular with anti-PD-1 antibody ezabenlimab; international Phase 1b ongoing clinical trial in combination with ezabenlimab alone or with other drugs in patients with recurrent/metastatic head and neck squamous cell carcinoma (HNSCC) and hepatocellular carcinoma (HCC).

OSE Immunotherapeutics expects to generate further significant value from its two proprietary drug discovery platforms, which are central to its ambitious goal to deliver next-generation first-in-class immunotherapeutics:

• BiCKI® platform focused on immuno-oncology (IO) is a bispecific fusion protein platform built on the key backbone component of anti-PD1 combined with a new immunotherapy target to increase anti-tumor efficacy. BiCKI-IL-7 is the most advanced BiCKI® candidate targeting anti-PD1xIL-7.
• Myeloid platform focused on optimizing the therapeutic potential of myeloid cells in IO and immuno-inflammation (I&I). OSE-230 (ChemR23 agonist mAb) is the most advanced candidate generated by the platform, with the potential to resolve chronic inflammation by driving affected tissues to tissue integrity.

International Media: MEDiSTRAVA Consulting

OSEImmuno@medistrava.com

Sylvie Berrebi

+44 203 928 6900

Additional information about OSE Immunotherapeutics assets is available on the Company's website: www.ose-immuno.com

French Media: FP2COM Florence Portejoie fportejoie@fp2com.fr +33 6 07 768 283

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Contacts OSE Immunotherapeutics Sylvie Détry sylvie.detry@ose-immuno.com +33 1 53 198 757

Investor Relations Thomas Guillot thomas.guillot@ose-immuno.com +33 6 07 380 431

Forward-looking statements

This press release contains express or implied information and statements that might be deemed forward-looking information and statements in respect of OSE Immunotherapeutics. They do not constitute historical facts. These information and statements include financial projections that are based upon certain assumptions and assessments made by OSE Immunotherapeutics' management in light of its experience and its perception of historical trends, current economic and industry conditions, expected future developments and other factors they believe to be appropriate.

These forward-looking statements include statements typically using conditional and containing verbs such as "expect", "anticipate", "believe", "target", "plan", or "estimate", their declensions and conjugations and words of similar import. Although the OSE Immunotherapeutics management believes that the forward-looking statements and information are reasonable, the OSE Immunotherapeutics' shareholders and other investors are cautioned that the completion of such expectations is by nature subject to various risks, known or not, and uncertainties which are difficult to predict and generally beyond the control of OSE Immunotherapeutics. These risks could cause actual results and developments to differ materially from those expressed in or implied or projected by the forwardlooking statements. These risks include those discussed or identified in the public filings made by OSE Immunotherapeutics with the AMF. Such forward-looking statements are not guarantees of future performance. This press release includes only summary information and should be read with the OSE Immunotherapeutics Universal Registration Document filed with the AMF on 15 April 2022, including the annual financial report for the fiscal year 2021, available on the OSE Immunotherapeutics' website. Other than as required by applicable law, OSE Immunotherapeutics issues this press release at the date hereof and does not undertake any obligation to update or revise the forwardlooking information or statements.

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