SECuRE trial progresses: No dose-limiting toxicities, strong early efficacy in first multi-dose group

Clarity Pharmaceuticals, a clinical-stage radiopharmaceutical company, has reported positive safety and preliminary efficacy results from the ongoing SECuRE trial. The trial is investigating the safety and efficacy of 67Cu-SAR-bisPSMA in treating prostate cancer. Cohort 4, which is the focus of this update, is the first group to receive multiple cycles of this radiopharmaceutical at the highest dose of 12GBq.

The Safety Review Committee (SRC) evaluated early data from the first three participants in Cohort 4, each of whom received two doses of 67Cu-SAR-bisPSMA. Two participants have completed the dose-limiting toxicity (DLT) period, and the third is expected to complete it by the end of September. To date, no DLTs have been observed, consistent with findings from the earlier cohorts. The safety profile remains positive, with most adverse events (AEs) being mild or moderate and largely resolving or improving over time.

Preliminary efficacy data is promising. Two participants who completed the DLT period have shown significant drops in prostate-specific antigen (PSA) levels, exceeding 60% reductions following their second dose. One participant has experienced a notable 92.3% decrease in PSA levels, along with a substantial reduction in tumor volume, as visualized by 64Cu-SAR-bisPSMA imaging.

Based on these encouraging results, the SRC recommended proceeding with the enrollment of the last three participants in Cohort 4. Following this, the trial will move into Phase II, which involves a cohort expansion of 14 participants, pending additional safety evaluations.

Cohort 4 is structured as a "3+3" cohort, where participants receive a minimum of two therapy cycles. Observing the positive safety profile in earlier cohorts, the SRC approved a modification allowing up to four doses for those benefiting from the treatment. This adjustment aims to maximize the therapeutic benefit for participants.

In terms of safety, the SRC reviewed data from the first three participants in Cohort 4, all of whom received two cycles. No DLTs were noted, and most AEs were mild to moderate, with the majority resolving or improving by the last assessment. For the participant yet to complete the DLT period, nausea was the only AE reported, and it has since resolved.

Efficacy assessments show a significant reduction in PSA levels in the two participants who have completed the DLT period. Notably, one participant experienced a remarkable 92.3% decrease in PSA and a 60.6% reduction in tumor volume, assessed through PSMA PET imaging. This participant had previously undergone several lines of therapy, including androgen deprivation therapy (ADT), an androgen receptor pathway inhibitor (ARPI), and an investigational agent in a clinical trial, highlighting the potential efficacy of 67Cu-SAR-bisPSMA even in heavily pre-treated patients.

Dr. Alan Taylor, Clarity's Executive Chairperson, expressed optimism about the trial's progress, noting the excellent safety profile and significant efficacy data. He emphasized that while safety is the current priority in this dose-escalation phase, the observed efficacy results are highly encouraging. Participants who have completed the DLT period may receive additional doses, pending ongoing safety and efficacy evaluations.

Looking ahead, Clarity plans to use this data to inform the next stages of its clinical development program, including the expanded cohort in the SECuRE trial and a subsequent Phase III clinical trial. The goal is to obtain regulatory approval and achieve full commercial rollout. According to Dr. Taylor, the favorable safety profile of 67Cu-SAR-bisPSMA compared to current prostate cancer treatments suggests its potential for earlier disease stages, with plans for clinical trials focusing on these earlier stages already in motion.

The outstanding efficacy observed in late-stage patients, particularly those with high PSA levels who have failed multiple therapies, remains a priority for Clarity. The company is collaborating with key opinion leaders and clinical advisors to address this unmet need while also progressing toward treating earlier stages of prostate cancer. Dr. Taylor highlighted the rapid progress from initial research to clinical application, underscoring Clarity's commitment to improving cancer treatment outcomes.