OSE Immunotherapeutics : and Boehringer Ingelheim Present Positive Phase 1 Results with First-in-Class SIRP? inhibitor BI 765063 in Advanced Solid Tumors at ASCO 2021

Nantes - OSE Immunotherapeutics (ISIN: FR0012127173; Mnemo: OSE) and its development partner Boehringer Ingelheim announced acceptance of an upcoming poster presentation at the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting, being held June 4 - 8, 2021, covering promising initial data from Phase 1 dose escalation of selective SIRP? inhibitor BI 765063 in patients with advanced solid tumors (Abstract #2623).

The data to be presented at ASCO 2021 indicate that OSE Immunotherapeutics' first-in-class signal regulatory protein ? (SIRP?) inhibitor BI 765063 was well-tolerated, showed sustained receptor occupancy (RO) saturation and monotherapy activity. Clinical benefit was observed in 45% of patients evaluable per RECIST* criteria. A durable partial response was observed in an advanced hepatocellular carcinoma (HCC) patient, and the on-treatment biopsy of the responder showed an increase in CD8 T-cell infiltration and activation. Furthermore, the ontreatment biopsy also showed an increase in PD-L1 expression on tumor cells. A BI 765063 dose escalation study in combination with Ezabenlimab (PD-1 antagonist) is ongoing and will help determine the recommended dose for further Phase 2 clinical development in patients with advanced solid tumors. Alexis Peyroles, CEO of OSE Immunotherapeutics commented: 'OSE Immunotherapeutics is moving forward to deliver highly innovative, first-in-class and best-in-class compounds. The promising data presented at ASCO includes no serious dose limiting toxicities, as well as early evidence of efficacy, suggesting that selective myeloid cell targeting of SIRP? to modulate CD47-dependent inhibition of anti-tumor immunity including the 'Don't Eat Me' axis is a sound therapeutic strategy in solid tumors. These promising data presented at ASCO 2021 on BI 765063 confirm the quality of our science and we look forward to continuing to accelerate our clinical development and pipeline diversification over the coming years.'

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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 forward-looking 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 2021, including the annual financial report for the fiscal year 2020, 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 forward-looking information or statements.

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