Trial of 64Cu/67Cu SAR-bisPSMA progresses following positive data

The Safety Review Committee has recommended progression of the phase 1/2 SECuRE trial (NCT04868604) exploring 64Cu/67Cu SAR-bisPSMA in patients with metastatic castrate-resistant prostate cancer (mCRPC) following positive data from the initial 3 patients enrolled in cohort 3, who are being treated at the highest dose level of 12GBq, announced Clarity Pharmaceuticals, the developer of the products, in a news release.¹

Recruitment of the additional 3 participants for cohort 3 of the study has opened across clinical sites in the US.

According to the release, no dose-limiting toxicities were observed among the initial 3 patients in cohort 3, and no patients experienced adverse events (AEs) related to 64Cu-SAR-bisPSMA. Only 1 patient experienced an AE related to treatment with 67Cu-SAR-bisPSMA, which was a grade 1 reduction in neutrophil count. The patient has fully recovered.

Additionally, 2 of the 3 participants experienced a reduction in prostate-specific antigen (PSA) levels within weeks following single dose administration of 12GBq 67Cu-SAR-bisPSMA. At the time of data report, 1 patient had experienced a greater than 90% reduction in PSA, and the other had experienced an approximately 40% reduction in PSA.

Given the SECuRE trial’s 3+3 design, the Safety Review Committee has recommended that the trial continue with the 3 additional patients in cohort 3 as planned.

"A number of patients from the SECuRE trial have either received, or will soon receive, additional doses of 67Cu-SAR-bisPSMA under the US Food and Drug Administration's (FDA) Expanded Access Program (EAP). This demonstrates the initial clinical benefit observed in such patients after the administration of a single cycle of the product during the trial,” said Executive Chairperson for Clarity Pharmaceuticals Alan Taylor, PhD, in the news release.¹

The SECuRE trial is a multicenter, single-arm, dose escalation study to assess the safety and efficacy of 67Cu-SAR-bisPSMA following detection of PSMA-expressing lesions with 64Cu-SAR-bisPSMA.² The trial includes patients with mCRPC who have progressed following treatment with androgen deprivation therapy and at least 1 second-generation androgen receptor pathway inhibitor, such as abiraterone acetate (Zytiga) or enzalutamide (Xtandi).

Cohort 3 of the SECuRE trial is the last to assess 67Cu-SAR-bisPSMA administered in single doses. Pending safety evaluations from the additional 3 participants in the cohort, the trial will progress to multi-dose cohort explorations. All 3 initial participants in cohort 3 remain on trial.

Recruitment of the additional 3 participants for cohort 3 of the study has opened across clinical sites in the US.

Taylor concluded in the news release, "As we have seen PSA reductions in the majority of patients after a single cycle of 67Cu-SAR-bisPSMA across all dose levels, which is known to be an independent prognostic indicator of improved overall survival following radio-ligand therapy, we hope to achieve long-term and durable responses once we progress to the multi-dose cohorts of the trial. Furthermore, with commercial quantities of the 67Cu radioisotope now being routinely produced domestically in the US, we see a clear path to commercialization as we can resolve the supply and manufacturing issues which have plagued the commercial launch of first-generation products. We look forward to sharing more data along with any further updates from patients who may receive single or multiple cycles of 67Cu-SAR-bisPSMA in our programs and bringing this product to the greater prostate cancer patient population.”¹

References

1. Clarity’s theranostic prostate cancer trial progresses at the highest dose level cohort. News release. Clarity Pharmaceuticals. Published online and accessed November 29, 2023. https://www.prnewswire.com/news-releases/claritys-theranostic-prostate-cancer-trial-progresses-at-the-highest-dose-level-cohort-302000099.html

2. 64Cu-SAR-bisPSMA and 67Cu-SAR-bisPSMA for Identification and Treatment of PSMA-expressing Metastatic Castrate Resistant Prostate Cancer (SECURE). ClinicalTrials.gov. Last updated May 24, 2023. Accessed November 29, 2023. https://clinicaltrials.gov/ct2/show/NCT04868604