Oncoinvent ASA

Regulatory Filings • Oct 8, 2025

Oncoinvent Reports Positive Final Data from Phase 1 Trial of Radspherin® to Treat Ovarian Cancer

New Data Highlight Continued Potential of Radspherin to Prevent Disease Progression

Oslo, Norway, 8 October 2025

Oncoinvent ASA, a clinical-stage radiopharmaceutical company developing innovative treatments for solid cancers, today announced positive final 24-month follow-up results from its Phase 1 clinical trial (RAD-18-001) evaluating Radspherin® in patients with platinum-sensitive recurrent ovarian cancer and peritoneal carcinomatosis. Radspherin®, direct intraperitoneal targeting with the alphaemitter radium-224, aims to eliminate post-surgery micro-metastases and thereby prevent or delay peritoneal recurrence.

In this Phase 1 trial, 10 out of 21 patients received the highest and recommended intraperitoneal dose of 7 MBq Radspherin® after dose escalation (1, 2, 4 and 7 MBq). The final 24-month data still reports that only 1 of these 10 patients had peritoneal recurrence, and peritoneal recurrence rate remains at 10%. Two additional patients were reported with lymph node metastases outside of the peritoneum, giving an overall recurrence rate of 30%. In similar populations, approximately 55-60% of patients receiving best standard of care would expect disease recurrence at this time point1,2,3 .

"These highly encouraging results conclude our Phase 1 program for Radspherin® and fuel our determination to advance Radspherin® as an innovative treatment for patients with peritoneal metastases as quickly as possible," said Oystein Soug, CEO of Oncoinvent. "We are profoundly grateful to the patients, investigators, and the team for their invaluable contributions and look forward to interim results from our Phase 2 study next year."

"Peritoneal metastases remain a defining challenge in ovarian cancer, often driving recurrence," said Dr. Luis Chiva, Principal Investigator and Director of Department of Obstetrics and Gynecology, Clinica Universidad de Navarra, Spain. "These final results are truly encouraging, suggesting that Radspherin® could help delay disease progression and offer patients hope for longer, healthier lives. It is particularly promising to see that the new recurrences were limited to lymph nodes, which are typically associated with longer survival compared to peritoneal relapses.

¹ Coleman et al. N Engl J Med. 2019 Nov 14;381(20):1929-1939

²Harter et al. N Engl J Med. 2021 Dec 2;385(23):2123-2131

³ Shi et al. Lancet Oncol. 2021 Apr;22(4):439-449

About RAD-18-001

RAD-18-001 was an open label Phase 1 trial conducted in patients with peritoneal metastases in platinum-sensitive recurrent ovarian cancer. The trial was designed to evaluate dosing, safety and tolerability, and signal of efficacy of intraperitoneally administered Radspherin® following complete surgical resection. A total of 21 patients were enrolled across sites in Norway, Belgium and Spain.

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 Euronext Growth Oslo.

About Radspherin

Radspherin® is an investigational radiopharmaceutical designed for the local treatment of cancer that has spread to body cavities. It consists of billions of calcium carbonate microparticles containing the radioactive material radium-224. The mode of action is the decay of radium-224 emitting alphaparticles, 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 forwardlooking 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.

For further information, please contact:

Oystein Soug, Chief Executive Officer

Email: soug@oncoinvent.com

Tore Kvam, Chief Financial Officer Email: kvam@oncoinvent.com