Clarity Pharmaceuticals announced the successful completion of the first stage of cohort 3 of the Phase I/IIa theranostic trial, SECuRE, evaluating 64Cu/67Cu-SAR-bisPSMA in patients with mCRPC where 3 participants have been treated at the highest dose level of 12GBq of 67Cu-SAR-bisPSMA. No adverse events were reported in relation to 64Cu-SAR-bisPSMA. Only 1 adverse event was reported and related to the 12GBq cycle of 67Cu-SAR-bisPSMA in 1 of the 3 participants, which was a grade 1 decrease in neutrophil count, and the patient has fully recovered.

No ongoing adverse events and no DLTs have been reported and the SRC has recommended the trial progresses with the 3 additional participants as planned in cohort 3. The SECuRE trial (NCT04868604) is a Phase I/IIa theranostic trial for identification and treatment of Prostate-Specific Membrane Antigen (PSMA) expressing mCRPC using 64Cu/67Cu-SAR-bisPSMA. 64Cu-SAR-bisPSMA is used to visualise PSMA expressing lesions and select candidates for subsequent 67Cu-SAR-bisPSMA therapy. The trial is a multi-centre, single arm, dose escalation trial with a cohort expansion involving up to 44 patients in the US.

The aim of the trial is to determine the safety and efficacy of 67Cu-SAR-bisPSMA for the treatment of prostate cancer. Cohort 3 of the trial has a 3+3 study design with the intent to gather and analyse data from the first 3 participants before progressing with an additional 3 participants. The initial data is very encouraging with no DLTs observed at the highest dose of 67Cu-SAR-bisPSMA (12GBq) and the SRC, responsible for assessing safety of participants and overseeing the general progress of the trial, has assessed the data and recommended the trial continues.

Cohort 3 is the last to assess single doses of 67Cu-SAR-bisPSMA and will be followed by a multi-dose cohort, pending safety evaluation. The initial 3 participants in cohort 3 were heavily pre-treated prior to entering the trial, having received multiple lines of therapy including other investigational products, radioligand therapy and chemotherapy. They continue to be monitored by their physicians for safety and treatment response as per the trial protocol.

All 3 participants in cohort 3 remain on the trial following their recent administration of 12GBq of 67Cu-SAR-bisPSMA, with 2 demonstrating a PSA reduction within weeks of dosing, one of which is greater than 90% reduction and the second approximately 40% reduction to date.