IO Biotech Announces Late-Breaking Abstract in Advanced Melanoma Selected for Oral Presentation at ESMO Congress 2025

• Oral presentation will highlight the results from the randomized Phase 3 trial (IOB-013/KN-D18) of IO102-IO103 cancer vaccine plus pembrolizumab for first-line (1L) advanced melanoma
• Poster presentation will share final data from Phase 2 basket trial (IOB-022/KN-D38) of IO102-IO103 cancer vaccine plus pembrolizumab for 1L treatment of solid tumors

NEW YORK, Sept. 23, 2025 (GLOBE NEWSWIRE) — IO Biotech (Nasdaq: IOBT), a clinical-stage biopharmaceutical company developing novel, immune-modulatory, off-the-shelf therapeutic cancer vaccines, today announces a late-breaking abstract has been accepted and selected as a Proffered Paper oral presentation at the 2025 European Society for Medical Oncology (ESMO) Congress taking place in Berlin, Germany from October 17-21, 2025.

The oral presentation will highlight the results from the randomized Phase 3 trial assessing the efficacy and safety of IO102-IO103 (IDO/PD-L1 vaccine) in combination with pembrolizumab vs pembrolizumab monotherapy in 1L advanced melanoma. In addition, final data from the Phase 2 basket trial with updated efficacy and safety data, median progression-free survival (PFS), landmark PFS and overall survival data, as well as biomarker and translational data for 1L treatment in non-small cell lung cancer (NSCLC) and squamous cell carcinoma of head and neck (SCCHN), will be presented in a poster session. Details of the presentations are as follows:

Late-breaking abstracts at ESMO are generally reserved for high-quality, new research findings from randomized Phase 2 or Phase 3 trials with implications for clinical practice or understanding of disease processes. Proffered papers are oral presentations of original data of superior quality, followed by expert discussion and perspectives.

The poster may be found on the “Posters & Publications” page of the IO Biotech website at the start of the meeting.

About Cylembio^®

Cylembio^® (imsapepimut and etimupepimut, adjuvanted) is an investigational, immune-modulatory, off-the-shelf therapeutic cancer vaccine candidate designed to kill both tumor cells and immune-suppressive cells in the tumor microenvironment (TME) by stimulating activation and expansion of T cells against indoleamine 2,3-dioxygenase 1 (IDO1) positive and/or programmed death-ligand 1 (PD-L1) positive cells. The company is currently conducting a pivotal Phase 3 trial (IOB-013/KN-D18; NCT05155254) investigating Cylembio in combination with Merck’s anti-PD-1 therapy, KEYTRUDA^® (pembrolizumab) versus pembrolizumab alone in patients with advanced melanoma, a Phase 2 basket trial (IOB-022/KN-D38; NCT05077709) investigating Cylembio in combination with pembrolizumab as first line treatment in patients with advanced solid tumors, and a Phase 2 basket trial (IOB-032/PN-E40; NCT05280314) investigating Cylembio in combination with pembrolizumab as neo-adjuvant/adjuvant treatment of patients with solid tumors. Enrollment in the Phase 3 trial was completed rapidly by December 2023 with topline results from this trial reported in the third quarter of 2025. Enrollment in the two ongoing company-sponsored Phase 2 clinical trials is now complete.

The clinical trials are sponsored by IO Biotech and conducted in collaboration with Merck, which is supplying pembrolizumab. IO Biotech maintains global commercial rights to Cylembio.

Cylembio^® is a registered trademark of IO Biotech ApS, a subsidiary of IO Biotech.

KEYTRUDA^® is a registered trademark of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA (known as MSD outside of the US and Canada).

About the IOB-013/KN-D18 Pivotal Phase 3 Clinical Trial

IOB-013/KN-D18 (ClinicalTrials.gov: NCT05155254) is an open label, randomized Phase 3 pivotal clinical trial evaluating Cylembio^® in combination with Merck’s anti-PD-1 therapy, KEYTRUDA^® (pembrolizumab) versus pembrolizumab alone in patients with previously untreated, unresectable or metastatic (advanced) melanoma. Enrollment in the trial was completed by December 2023 with a total of 407 patients enrolled from more than 100 centers across the United States, Europe, Australia, Turkey, Israel and South Africa. The primary endpoint of the study was progression free survival. Secondary endpoints include overall response rate, overall survival, durable objective response rate, complete response rate, duration of response, time to complete response, disease control rate, and incidence of adverse events and serious adverse events (safety and tolerability). Biomarkers in the blood and tumor tissue will also be assessed as exploratory endpoints. The company reported topline results from this trial in the third quarter of 2025. IO Biotech is sponsoring the Phase 3 trial and Merck is supplying pembrolizumab.

About the IOB-022/KN-D38 Phase 2 Solid Tumor Basket Trial

IOB-022/KN-D38 (NCT05077709) is a non-comparative, open label trial to investigate the safety and efficacy of Cylembio^® in combination with Merck’s anti-PD-1 therapy, KEYTRUDA^® (pembrolizumab) in the first-line treatment of metastatic non-small cell lung cancer (NSCLC) or metastatic squamous cell carcinoma of the head and neck (SCCHN) at sites in the United States, Spain, and the United Kingdom. IO Biotech is sponsoring the Phase 2 trial and Merck is supplying pembrolizumab.

About IO Biotech

IO Biotech is a clinical-stage biopharmaceutical company developing novel, immune-modulatory, off-the-shelf therapeutic cancer vaccines based on its T-win^® platform. The T-win platform is based on a novel approach to cancer vaccines designed to activate T cells to target both tumor cells and the immune-suppressive cells in the tumor microenvironment. IO Biotech is advancing its lead cancer vaccine candidate, Cylembio^®, in clinical trials, and additional pipeline candidates through preclinical development. IO Biotech is headquartered in Copenhagen, Denmark and has US headquarters in New York, New York.

For further information, please visit www.iobiotech.com. Follow us on our social media channels on LinkedIn and X (@IOBiotech).

Forward-Looking Statement

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements, including statements regarding the timing or outcome of communications with regulatory authorities including the FDA, the timing or outcome of the submission of marketing applications, including a BLA, for Cylembio, the timing or outcome of the launch of Cylembio, and statements regarding other current or future clinical trials, their timing, progress, enrollment or results, or the company’s financial position or cash runway, are based on IO Biotech’s current assumptions and expectations of future events and trends, which affect or may affect its business, strategy, operations or financial performance, and actual results and other events may differ materially from those expressed or implied in such statements due to numerous risks and uncertainties. Forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified. Because forward-looking statements are inherently subject to risks and uncertainties, you should not rely on these forward-looking statements as predictions of future events. These forward-looking statements speak only as of the date hereof and should not be unduly relied upon. Except to the extent required by law, IO Biotech undertakes no obligation to update these statements, whether as a result of any new information, future developments or otherwise.

Contact:

Investors
Maryann Cimino, Director of Investor Relations
IO Biotech, Inc.
617-710-7305
mci@iobiotech.com

Media
Julie Funesti
Edelman
917-498-1967
julie.funesti@edelman.com