OSE Immunotherapeutics Publie Sa Position De Trésorerie Au 30 Juin 2025

Nantes, France, September 25, 2025, 6 p.m. CET - OSE Immunotherapeutics SA ( ISIN: FR0012127173; Mnemo: OSE) reports its cash position as of June 30, 2025. Due to the Company's Annual General Meeting being rescheduled to September 30, 2025, and to allow shareholders to first approve 2024 financial statements, the full 2025 half-year interim financial results will be published on October 15, 2025.

Update on AbbVie Partnership related to ABBV-230

The Company initially expected the initiation of Phase 1 trial of ABBV-230 and the related milestone payment in late 2025. Based on current discussions with its partner, the Company now anticipates a delay in the development timeline.

As the Company has no control over the start of this trial, and in line with the principle of prudence, it has chosen to exclude from its current cash projections the related milestone payment from AbbVie.

Cash Position as of June 30, 2025

As of June 30, 2025, OSE Immunotherapeutics' cash position totalled €41.6 million, compared to €64.2 million as of December 31, 2024.

The cash position includes cash, cash equivalents and fixed-term deposits classified as current and non-current financial assets. As of June 30, 2025, cash and cash equivalents amounted to €25.4 million while fixed-term deposits classified as current and non-current current-financial assets amounted to €16.2 million.

Based on current assumptions and available financial resources, the Company considers that its operations are funded until the beginning of Q4 2026. This cash runway includes a possible exercise of remaining warrants issued to the benefit of Vester Finance¹ but no longer factors in any upcoming milestone from current partnerships. Should one of the anticipated milestones be received in 2026, the cash runway would be extended to at least Q1 2027, as previously communicated.

To extend its runway beyond 2026, the Company continues to evaluate several complementary options, including a potential new strategic partnership involving one of its proprietary assets, equity financing and restructuring of its existing debt in addition to potential milestone payments from current partnerships.

2025 Half-Year Interim Financial Results

Due to the rescheduling of the Company's Annual General Meeting to September 30, 2025, and to allow shareholders to first approve the 2024 financial statements, the full 2025 half-year interim financial results will be published on October 15, 2025.

ABOUT OSE IMMUNOTHERAPEUTICS
OSE Immunotherapeutics is a biotech company dedicated to developing first-in-class assets in immuno-oncology (IO) and immuno-inflammation (I&I) that address the unmet patient needs of today and tomorrow. We partner with leading academic institutions and biopharmaceutical companies in our efforts to develop and bring to the market transformative medicines for people with serious diseases. OSE Immunotherapeutics is based between Nantes and Paris and is quoted on Euronext. Additional information about OSE Immunotherapeutics assets is available on the Company's website: Click and follow us on LinkedIn.

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Forward-looking statements
This press release contains express or implied information and statements that might be deemed forward-looking 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 considering 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 can often be identified by the use of the conditional tense and by verbs such as“expect”,“anticipate”,“believe”,“target”,“plan”, or“estimate”, their declensions and conjugations as well as other similar terms. Although the management of OSE Immunotherapeutics believes that the forward-looking statements and information are reasonable, 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 within the AMF. Such forward-looking statements are not guarantees of future performance. This press release includes only summary information and should be read alongside OSE Immunotherapeutics Universal Registration Document filed with the AMF on April 30, 2025, including the annual financial report for the fiscal year 2024, available on OSE Immunotherapeutics' website. Other than as required by applicable laws, 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.

1 Retained assumption is a full exercise of the remaining 880,000 warrants by Vester Finance at an estimated price of €6.00 per share.

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• 250925_EN_2025 June 30 Cash Position_vF

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