Oncoinvent will present final 24-month follow-up data from its Phase 1 RAD-18-001 study of Radspherin in platinum-sensitive epithelial ovarian cancer at the European Society of Gynaecological Oncology 2026 Congress.

The company said the data show that nine of 10 patients treated at the recommended dose remained free from peritoneal recurrence at 24 months following cytoreductive surgery.

Radspherin is an intraperitoneal alpha-emitting therapy consisting of radium-224 labelled microparticles. It is designed to target residual cancer cells in the peritoneal cavity after surgery while limiting exposure to surrounding healthy tissue. The approach aims to address microscopic residual disease and reduce the risk of recurrence in a population with historically high relapse rates.

The RAD-18-001 Phase 1 study enrolled 21 patients across escalating dose levels after cytoreductive surgery for peritoneal recurrence of platinum-sensitive epithelial ovarian cancer. According to the company, the study demonstrated a favourable safety profile, with no dose-limiting toxicities observed.

No grade 3 or higher adverse events were considered related to Radspherin. Following dose escalation, 7 MBq was selected as the recommended dose.

At 24 months, only one of 10 patients treated at the recommended dose experienced peritoneal recurrence, indicating a signal of durable local disease control in this small early-stage trial.

Yun Wang, principal investigator of the RAD-18-001 trial at the Norwegian Radium Hospital, Oslo University Hospital, said: “We are pleased to present our Phase 1 data at the ESGO 27th Annual Meeting, an important forum for sharing findings with the international gynecologic oncology community. These encouraging data reflect the collaborative efforts of the study team and the potential of Radspherin to address a patient population with high risk of peritoneal recurrence and poor prognosis.”

Kari Myren, chief medical officer at Oncoinvent, added: “We remain committed to advancing Radspherin in the Phase 2 trial and to further evaluating its potential to benefit patients with ovarian cancer.”

The poster, titled “Safety and efficacy results from a phase 1 study of intraperitoneal alpha-emitting radium-224 labelled microparticles after cytoreductive surgery in patients with peritoneal recurrence of platinum-sensitive epithelial ovarian cancer”, will be presented at the ESGO Congress, taking place in Copenhagen from 26–28 February 2026.

While the results are based on a limited number of patients and an early-stage study, the 24-month follow-up provides insight into the durability of response and safety profile of intraperitoneal radium-224 microparticles in this setting. Oncoinvent is continuing clinical development of Radspherin in a Phase 2 trial to further assess efficacy and safety in a larger cohort.