Phase 3 trial of Cu-64 SAR-bisPSMA in prostate cancer set to commence later this year

CLARIFY, a prospective phase 3 trial of Cu-64 SAR-bisPSMA for prostate cancer, is set to commence at the end of this year following a successful end-of-phase meeting with the FDA, Clarity Pharmaceuticals, the developer of the diagnostic, announced in a news release.¹

The trial plans to enroll a total of 383 patients who have received a diagnosis of prostate cancer.

“We look forward to opening our phase 3 trial later this year to confirm and build on the positive data we have seen on the 64Cu SAR-bisPSMA product to date. Our hope is that better diagnostic tools will help clinicians determine the best course of treatment for their patients, informing a potential life-changing decision between the surgical removal of the prostate and other treatment options that may support a better quality of life post-treatment,” said Alan Taylor, PhD, in a news release on the announcement. Taylor is the executive chairperson for Clarity Pharmaceuticals.

The non-randomized, single-arm, open-label, multi-center trial plans to enroll a total of 383 patients who have received a diagnosis of prostate cancer with high-risk features, as determined by histopathology, and who are set to receive radical prostatectomy with pelvic lymph node dissection.

The study will assess the ability of Cu-64 SAR-bisPSMA to detect prostate cancer within the pelvic lymph nodes. Evaluation will take place on day 1, the day of administration, and approximately 24 hours following administration.

Patient recruitment is set to begin in late 2023.

Previous data on Cu-64 SAR-bisPSMA

The phase 3 trial design is based on previous data on Cu-64 SAR-bisPSMA, including from the phase 1 PROPELLER trial (NCT04839367), which assessed the safety, tolerability, and efficacy of the diagnostic. Data from PROPELLER were presented the 2023 ASCO Genitourinary Cancers Symposium in San Francisco, California.²

Patients in the study were administered a 68Ga-PSMA-11 PET/CT at screening about 45 to 60 minutes following injection. They were randomized 1:1:3 to receive 100 MBq (n = 6), 150 MBq (n = 6), or 200 MBq (n = 18) of 64Cu-SAR-bisPSMA followed by a PET/CT at 2 to 4 hours after injection.

The highest image quality scores for both readers were seen among those from patients in the 200 MBq of Cu-64 SAR-bisPSMA cohort (n = 18). In this cohort, reader 1 reported that Cu-64 SAR-bisPSMA was able to detect primary prostate cancer in 100% (18/18) of patients and 68Ga-PSMA-11 PET/CT was able to detect primary prostate cancer in 77.8% (14/18) of patients.

Reader 2 reported that Cu-64 SAR-bisPSMA was able to detect primary prostate cancer in 85.7% of patients (12/14; 4 scans were determined by the reader to be non-evaluable) and 68Ga-PSMA-11 PET/CT was able to detect primary prostate cancer in 83.3% (15/18) of patients.

Further, safety results showed that Cu-64 SAR-bisPSMA was well tolerated. In total, there was 1 adverse event that was considered to be related to Cu-64 SAR-bisPSMA, which was grade 1 dysgeusia in 1 patient who received the 200 MBq dose.

“The positive results from our completed PROPELLER trial showed that 64Cu SAR-bisPSMA is safe, and its uptake in PSMA-expressing cancer lesions was significantly higher compared [with] the approved standard-of-care PSMA imaging agent for PC in Australia and the US,” Taylor said. “This may enable diagnosis of additional and smaller lesions, especially when coupled with the opportunity for delayed imaging, a characteristic not available to the first generation of PSMA imaging agents that exhibit high specificity but low sensitivity in diagnosing metastases outside of the prostate. Furthermore, we believe that the additional shelf-life of up to 48 hours could not only allow clinics greater flexibility in scheduling of the scans, but also improve patients' access to care in clinics and geographic areas where the short half-life of current PSMA PET tracers restricts the use of radiopharmaceuticals.”

References

1. Positive guidance from US FDA on Cu-64 SAR-bisPSMA Phase III trial in prostate cancer. News release. Clarity Pharmaceuticals. July 4, 2023. Accessed July 5, 2023. https://www.prnewswire.com/news-releases/positive-guidance-from-us-fda-on-cu-64-sar-bispsma-phase-iii-trial-in-prostate-cancer-301869495.html

2. Emmett L, Wong V, Lenzo N, Lengyelova E, Biggin C. Positron emission tomography of patients with confirmed prostate cancer using 64Cu-SAR-bisPSMA. J Clin Oncol. 41, 2023 (suppl 6; abstr 318). doi:10.1200/JCO.2023.41.6_suppl.318.