Oncoinvent has published Phase 1 dosimetry data for Radspherin in the Journal of Nuclear Medicine, showing low radiation exposure to normal organs.

Phase 1 dosimetry results published

Oncoinvent has announced publication of clinical dosimetry results from Phase 1 studies of Radspherin in patients with ovarian and colorectal cancer.

The findings, published in the Journal of Nuclear Medicine, assessed radiation exposure to normal tissues following treatment with Radspherin, an intraperitoneal alpha radiopharmaceutical being developed for peritoneal metastases.

The study included nine patients enrolled in dosimetry cohorts from the Phase 1 clinical studies.

Results showed that absorbed radiation doses to normal organs were below levels commonly associated with risks of complications, including in the kidneys and red bone marrow, which can be activity-limiting organs for radiopharmaceutical treatments.

The data provide information about how Radspherin distributes radiation following administration and could help inform further clinical development of the treatment.

Measuring radiation exposure

The publication, titled “Normal Tissue Dosimetry of Intraperitoneal Radium-224-Microparticle Therapy: Data from First-in-Human Studies in Patients with Peritoneal Metastases”, describes the methods used to estimate radiation exposure to normal tissues.

The study was conducted at The Norwegian Radium Hospital, part of Oslo University Hospital.

Caroline Stokke, senior author of the publication, head of nuclear medicine physics at Oslo University Hospital and chair of the European Association of Nuclear Medicine Dosimetry Committee, said dosimetry is important during early clinical development of radiopharmaceuticals.

“In early-phase clinical studies, dosimetry is essential to understand how radiation exposure relates to potential toxicity and identify potential dose-limiting tissues,” Stokke said.

Alpha-emitting radiopharmaceuticals can present particular challenges for dosimetry because conventional imaging approaches may not always be suitable for directly measuring radiation distribution.

The researchers therefore used a combination of approaches, including blood sampling and biokinetic modelling, to estimate radiation exposure to normal tissues.

Radspherin development

Radspherin is being developed as an intraperitoneal treatment intended to target cancer cells remaining in the abdominal cavity following surgery.

Oncoinvent said the dosimetry findings are consistent with the favourable safety profile reported from its Phase 1 studies and support continued development of the treatment for peritoneal metastases.

Kari Myren, chief medical officer at Oncoinvent, said radiation exposure to healthy organs can limit the doses that can be administered with radiopharmaceutical therapies.

“Our results indicate very low radiation exposure to healthy organs after treatment, which is consistent with the favorable safety profile observed in our clinical trials and supports the further development of Radspherin,” Myren said.

The published results relate specifically to normal-tissue dosimetry and do not establish the efficacy of Radspherin. Oncoinvent has previously reported final data from its Phase 1 studies, including what it described as encouraging efficacy signals.

The company is continuing development of Radspherin for patients with peritoneal metastases, including those associated with ovarian and colorectal cancers.