First patient dosed at highest level in trial of novel PSMA theranostic in mCRPC

The first patient has been dosed at the highest dose level of 12GBq in cohort 3 of the phase 1/2 SECuRE trial (NCT04868604), which is exploring the novel theranostic ⁶⁴Cu/⁶⁷Cu SAR-bisPSMA in patients with metastatic castrate-resistant prostate cancer (mCRPC).¹

“Results from cohort 2 are incredibly exciting and we look forward to seeing data from the increased dosing of 12GBq as well as discover the potential positive effects of multi-dosing on prostate cancer patients,” said Alan Taylor, PhD.

The theranostic ⁶⁴Cu/⁶⁷Cu SAR-bisPSMA combines the prostate-specific membrane antigen (PSMA) PET imaging agent 64Cu-SAR-bisPSMA and the PSMA targeted therapy ⁶⁷Cu-SAR-bisPSMA. In the SECuRE trial, ⁶⁴Cu-SAR-bisPSMA is being used for the selection of appropriate patients to receive treatment with ⁶⁷Cu-SAR-bisPSMA.²

Cohort 3 of the trial is exploring the safety and efficacy of a single-dose administration of 12GBq ⁶⁷Cu SAR-bisPSMA. This cohort will be the last to evaluate single doses, with multi-dose cohort explorations to follow given positive safety evaluations.

“Results from cohort 2 are incredibly exciting and we look forward to seeing data from the increased dosing of 12GBq as well as discover the potential positive effects of multi-dosing on prostate cancer patients,” said Alan Taylor, PhD, executive chairperson of Clarity Pharmaceuticals, the developer of the theranostic, in a news release on the findings.¹

Taylor added, “The fast pace of recruitment into the dose escalation phase of the trial is indicative of the high unmet need in the prostate cancer therapy space and we are thrilled to be working on a solution that has potential to not only offer treatment benefits to patients with mCRPC, but also resolve the logistical and manufacturing challenges of the current-generation radiopharmaceuticals, such as ¹⁷⁷Lu PSMA-617, especially now with the availability of commercial quantities of the ⁶⁷Cu radioisotope routinely produced domestically in the US and exclusively supplied to us by NorthStar.”

To enroll in the open-label, single-arm, dose-escalation SECuRE trial, patients must have mCRPC that has progressed despite being treated with androgen-deprivation therapy and at least 1 second-generation androgen receptor pathway inhibitor, such as abiraterone acetate (Zytiga) or enzalutamide (Xtandi).² Patients are required to have an ECOG performance status of 0 to 2, and a castrate level of serum/plasma testosterone (<50 ng/dL or <1.7 nmol/L). Individuals with brain metastases are not eligible to enroll.

Clarity previously reported on the completion of cohort 1 of the trial. Cohort 1 included 6 patients with mCRPC who received ⁶⁷Cu SAR-bisPSMA at the lowest dose level of 4 GBq. The study investigators reported that there were no dose-limiting toxicities at this dose level.³

Cohort 2 of the trial included 3 patients who were treated with a single dose of ⁶⁷Cu SAR-bisPSMA at 8 GBq. No dose-limiting toxicities were reported with this dose and all 3 patients remain on the trial. Further, all 3 participants experienced a 50% reduction in their PSA level within weeks of the single dose, with 2 of the patients showed a PSA reduction of greater than 95% and the third patient experiencing a reduction of approximately 70%.⁴

Recruitment for cohort 3 of the trial remains ongoing.

“We look forward to sharing more data on ⁶⁷Cu SAR-bisPSMA as we continue to recruit participants into the SECuRE trial and progress on our path towards commercialisation with the ultimate goal of improving treatment outcomes for people with cancer,” concluded Taylor in the news release.¹

References

1. First participant treated at the highest dose level in Clarity’s theranostic prostate cancer trial. News release. Clarity Phamaceuticals. Published online and accessed August 25, 2023. https://www.prnewswire.com/news-releases/first-participant-treated-at-the-highest-dose-level-in-claritys-theranostic-prostate-cancer-trial-301909746.html

2. NIH ClinicalTrials.gov. 64Cu-SAR-bisPSMA and 67Cu-SAR-bisPSMA for Identification and Treatment of PSMA-expressing Metastatic Castrate Resistant Prostate Cancer (SECURE). Last updated May 24, 2023. Accessed August 25, 2023. https://clinicaltrials.gov/ct2/show/NCT04868604

3. Clarity's theranostic prostate cancer trial advances to cohort 2. News release. Clarity Pharmaceuticals. May 24, 2023. Accessed August 25, 2023. https://www.prnewswire.com/news-releases/claritys-theranostic-prostate-cancer-trial-advances-to-cohort-2-301833001.html

4. Clarity's theranostic prostate cancer trial advances to highest dose level. News release. Clarity Pharmaceuticals. August 10, 2023. Accessed August 25, 2022. https://www.prnewswire.com/news-releases/claritys-theranostic-prostate-cancer-trial-advances-to-highest-dose-level-301897641.html