Oncoinvent ASA: Key information relating to the reverse share split and change of ISIN

Oslo, Norway, 14 January 2026: Reference is made to the stock exchange announcement made by Oncoinvent ASA (the "Company") on 8 January 2026 regarding the resolution by the Company's extraordinary general meeting to carry out a reverse share split of the Company's shares. Key information related to the reverse share split, including the relevant key dates that have been determined by the board of directors today in accordance with the resolution by the general meeting, is set out below:

· Date on which the corporate action was made public: 18 December 2025 · Reverse split ratio: 100:1, i.e. one hundred (100) old shares give one (1) new share · Last day including right: 16 January 2026 · Ex-date: 19 January 2026 · Record date: 20 January 2026 · Date of approval: 8 January 2026

Following completion of the reverse share split, the par value of the Company's shares will be increased from NOK 0.50 to NOK 50. Shareholders who do not own a number of shares which can be divided by 100 shall, in connection with the reverse share split, have their holdings rounded downwards, so that the shareholder receives a whole number of shares. Fractional shares will not be issued and the shareholders will not receive any compensation for the rounding. The fractional shares will be added together to whole shares and will be sold at the Oslo Stock Exchange. The net proceeds from the sale shall be donated to charity as determined by the board of directors.

In connection with the reverse share split, the Company's shares will be transferred to a new ISIN.

Please note the following key information for the change of ISIN:

· Issuer: Oncoinvent ASA · Previous ISIN for the Company's shares: ISIN NO 0013251173 · New ISIN for the Company's shares: ISIN NO 0013711713 · Date of ISIN change: 19 January 2026

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For further information, please contact:

Oystein Soug, Chief Executive Officer Email: soug@oncoinvent.com

About Oncoinvent

Oncoinvent is a clinical-stage biotechnology company developing novel radiopharmaceutical therapies against cancer. The lead product candidate, Radspherin®, uses the alpha-emitting radionuclide radium-224, directly targeting micro-metastases post-surgery, harnessing the benefits of modern radiopharmaceuticals without the complexities of biological targeting. Oncoinvent is investigating the safety and efficacy of Radspherin® in a clinical development program in two indications. One Phase 1 trial and one Phase 1/2a trial have been completed and one randomized Phase 2 trial is currently ongoing in the US, UK and Europe. Early clinical efficacy data are highly encouraging, and no serious toxicity or safety concerns have been reported to date. The Oncoinvent team consists of approx. 40 employees and runs a state-of-the-art manufacturing facility to produce drug products for clinical trials in Nydalen, Oslo. Oncoinvent is listed on the Oslo Stock Exchange.

About Radspherin

Radspherin® is an investigational radiopharmaceutical designed for the local treatment of cancer that has spread to body cavities. It consists of calcium carbonate microparticles containing the radioactive material radium-224. The mode of action is the decay of radium-224 emitting alpha-particles, a highly potent form of ionizing radiation. Radspherin® is investigated in clinical studies to treat peritoneal carcinomatoses from ovarian and colorectal cancer and it is administered intraperitoneally after surgical resection with removal of all macroscopic tumors.

Forward-Looking Statements

All statements other than statements of historical facts contained in this press release are forward-looking statements and are not a representation that Oncoinvent's plans, estimates, or expectations will be achieved. These forward -looking statements represent Oncoinvent's expectations as of the date of this press release, and Oncoinvent disclaims any obligation to update the forward -looking statements. These forward-looking statements are subject to known and unknown risks and uncertainties that may cause actual results to differ materially, including with respect to whether the results of clinical or other studies will support the use of our product offerings, the impact of results of such studies, our expectations of the reliability, accuracy and performance of our tests, or of the benefits of our tests and product offerings to patients, providers and payers.