SECuRE trial pre-chemo participants experience PSA level drops

Cohort expansion phase commences with promising results

The Safety Review Committee (SRC) has confirmed the end of the Dose Escalation phase and the start of the cohort expansion phase (phase 2) of the SECuRE trial. Based on efficacy and safety assessments, the SRC recommended expanding the dose level to 8 GBq and increasing the number of cycles from up to 4 to up to 6.

In Cohort 4 of the Dose Escalation phase, prostate-specific antigen (PSA) levels continue to drop, with reductions of 80% or more observed in three participants. One participant achieved a complete response after two doses of 12 GBq of 67Cu-SAR-bisPSMA, based on RECIST criteria.

Across all cohorts, 68% of participants showed reductions in PSA levels, despite most receiving only a single dose of 67Cu-SAR-bisPSMA. Participants who did not respond had received chemotherapy in the mCRPC stage or were part of the lowest dose cohort with high PSA levels at entry.

67Cu-SAR-bisPSMA has shown a favourable safety profile across all cohorts. Most adverse events (AEs) were Grade 1-2, with anaemia and thrombocytopenia being the most prevalent. One Dose Limiting Toxicity occurred at the highest dose in cohort 4, a transient grade 4 thrombocytopenia, which improved to grade 3 after two weeks.

In participants who had not received chemotherapy, PSA drops of 35% or more were observed in all but one participant. PSA reductions of 80% or more were achieved in almost half of these patients. Disease control was achieved in 92% of pre-chemotherapy participants.

The SECuRE trial protocol has been amended to include participants at earlier stages of their disease. The amendment increases the number of participants in the cohort expansion phase from 14 to 24, with some participants receiving 67Cu-SAR-bisPSMA and enzalutamide.

Clarity’s Executive Chairperson, Dr Alan Taylor, commented: “The SECuRE trial continues to generate extraordinary results, and we are thrilled to progress to phase 2. We are looking forward to executing our strategy of bringing 67Cu-SAR-bisPSMA to earlier lines of prostate cancer therapy and exploring its potential benefits in combination with enzalutamide.”