OSE Immunotherapeutics Reports its Cash Position as of June 30, 2026, and Provides Business Update

• €11.1 million cash position as of June 30, 2026; cash runway confirmed through December 2026
• The Company continues to engage actively with institutional investors in the United States and Europe to extend its cash runway beyond key upcoming value inflection points
• In this context, publication of first half 2026 financial results is postponed
• Enrolment of Tedopi’s Phase 3 clinical trial ARTEMIA in lung cancer on track for completion by end of December 2026; planned futility analysis now estimated for early-2027 due to a lower number of death events than expected
• Subcutaneous formulation of lusvertikimab (IL-7R) on track for validation by mid-2027
• Opportunity to move lusvertikimab into Phase 2 with current IV formulation in chronic pouchitis in 2027

Nantes, France, September 28, 2026 – 7:30am CET – OSE Immunotherapeutics SA (ISIN: FR0012127173; Mnemo: OSE), a clinical-stage biotech company dedicated to developing first-in-class therapies in immuno-oncology and immuno-inflammation, today reported its cash position as of June 30, 2026, updated its financial calendar and provided a business update.

“On the operational front, enrolment of Tedopi’s Phase 3 trial ARTEMIA in non-small cell lung cancer is on track. The interim futility analysis for ARTEMIA is event-driven. Deaths across the study have accrued more slowly than originally projected, and the analysis is now expected in early-2027, which is definitely interesting. In parallel, the subcutaneous formulation of lusvertikimab is moving as planned and results should be available by mid-2027 to support pursuing clinical development in ulcerative colitis. We are also very encouraged by our conversations with key opinion leaders to move rapidly into a Phase 2 trial with the current formulation in Chronic Pouchitis, a significant unmet need”, commented Marc Le Bozec, Chief Executive Officer of OSE Immunotherapeutics. “We have been actively engaging with institutional investors in the United States and in Europe for the past few months, helped by a flexible bridge financing in May, and are confident that the strength of our pipeline provides a solid foundation as we work to secure the financing needed to reach key value inflection points.”

Cash Position as of June 30, 2026

As of June 30, 2026, OSE Immunotherapeutics’ cash position totalled €11.1 million, compared to €17.0 million as of March 31, 2026. 

The Company implemented a flexible bridge equity financing in May 2026 which, in addition to available cash, and based on its current plans, is estimated to be sufficient to fund its operations through December 2026. This cash runway does not include any potential future milestone payments from existing partnerships.

This bridge financing was the first step of a global financing strategy aiming at securing OSE’s 3-year Strategic Plan and the Company continues to actively engage with institutional investors in the United States and in Europe in view to further extend its runway beyond 2026.

In addition, the Company continues to evaluate several complementary options, including a potential new strategic partnership involving one of its proprietary assets, restructuring of its existing debt, and potential milestone payments from current partnerships.

In the context of its ongoing financing efforts, the Company has deferred the publication of its half-year financial statements for 2026 and its Interim Financial Report to a later date.

Pivotal Phase 3 clinical trial ARTEMIA of Tedopi® in second-line non-small cell lung cancer (NSCLC)

Enrolment in the international pivotal Phase 3 clinical trial ARTEMIA evaluating Tedopi® in 363 HLA-A2 positive patients with metastatic NSCLC who have developed secondary resistance to immune checkpoint inhibitors is on track for completion by end of December 2026, as planned.

As per protocol, a futility analysis will be conducted independently by the statisticians of the Independent Data Monitoring Committee (IDMC). This analysis, performed when the trial reaches a predefined number of events, is based on an interim survival analysis and will remain blinded to the Sponsor, Regulatory Authorities, and all Investigators.

Initial assumptions anticipated reaching the required and predefined number of deaths by Q3 2026. While enrolment of the study has progressed according to plan, the trial is showing a lower number of deaths than initially expected, and the Company now anticipates reaching the predefined number of death events by the end of 2026. Consequently, the futility analysis is now expected to take place early 2027.

Other clinical trials evaluating Tedopi® in multiple indications

TEDOVA in ovarian cancer

In May 2026, the Company reported positive topline results from the TEDOVA/GINECO-OV244b/ENGOT-ov58 academic, international, Phase 2 trial sponsored by ARCAGY-GINECO and evaluating Tedopi®, with or without pembrolizumab, as a maintenance treatment in 185 patients with platinum-sensitive recurrent ovarian cancer (PSOC).

The primary endpoint was progression-free survival (PFS) comparing Tedopi® combined with pembrolizumab and the best supportive care. It was met and results showed a statistically significant improvement in PFS for the combination of Tedopi® and pembrolizumab compared to best supportive care (median PFS: 4.1 months vs 2.8 months; HR=0.53; p<0.001). When comparing the two investigational arms, the addition of pembrolizumab to Tedopi® resulted in a 28% reduction in the risk of progression or death (HR=0.72, p=0.074).

These results were presented by principal investigator Alexandra Leary, MD, PhD, at the ASCO 2026 Annual Meeting in May 2026 in Chicago, United States.

Combi-TED in NSCLC

Topline results from the Combi-TED Phase 2 international clinical trial sponsored by FoRT and evaluating Tedopi® in second-line treatment in combination with anti-PD1 or chemotherapy in 105 patients with metastatic NSCLC will be presented by principal investigator Federico Cappuzzo, MD, PhD, at the ESMO 2026 Annual Meeting on October 25, 2026, in Madrid, Spain.

Subcutaneous formulation of lusvertikimab (IL-7R) in inflammatory bowel diseases (IBD)

The subcutaneous formulation of lusvertikimab to be advanced in clinical development was selected and characterized earlier this year. The achieved concentration at 225mg per mL, based on previously evaluated intravenous efficacious doses in Phase 2 of 450mg and 850mg, is potentially compatible with the use of an autoinjector device.

The application for authorization of a Phase I study in healthy volunteers is currently being prepared with a submission scheduled by the end of 2026, with results expected by mid-2027.

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 listed on Euronext. Additional information about OSE Immunotherapeutics assets is available on the Company’s website: www.ose-immuno.com. Follow us on LinkedIn.

Contacts

OSE Immunotherapeutics: investors@ose-immuno.com

FP2COM (Media Relations): Florence Portejoie: fportejoie@fp2com.fr I +33 6 07 768 283

Astr Partners (Investor Relations):

Europe/UK: Guillaume Cabon: guillaume.cabon@astrpartners.com I +33 6 95 06 92 06

United States: Brian korb: brian.korb@astrpartners.com I +1 917-653-5122

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 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 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 June 4, 2026, including the annual financial report for the fiscal year 2025, 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.

Attachment

• EN_260928_OSE_Immunotherapeutics_2026_Q2_Cash_and_Business_Update_vdef