Blue Earth Therapeutics, a UK-based developer of radiopharmaceutical therapies, on Thursday reported further progress in the development of its radio-hybrid, lutetium-labelled, PSMA targeted, investigational radioligand therapy for metastatic castrate resistant prostate cancer, with enrolment of the first two patients in a Phase 2 clinical trial.

The primary measure of efficacy in the study will be the proportion of patients achieving greater than or equal to 50% reduction in PSA levels, as well as assessing radiographic progression-free survival and patient safety.

Blue Earth Therapeutics is testing multiple dosing regimens that focus on delivering higher radiation doses when tumour burden is usually highest, at the beginning of treatment. The study design aligns with the US FDA Project Optimus initiative, where the goal is that drug developers optimise dosing early in a product's development to deliver the best possible benefit risk profile.

Loading doses will be delivered by either giving a higher dose in the first two treatment cycles, or shortening the time between administration of the first three doses to three weeks from the usual six weeks. The study is also designed to test the clinical benefit of administration of high total doses of administered radioactivity, up to 60GBq. Phase 1 data confirmed a high ratio of uptake in tumour tissues vs. uptake in healthy tissues such as kidneys and salivary glands.

With up to 20 sites enrolling patients, the company expects to see first results from the study early next year.