FDA fast tracks 64Cu-SAR-bisPSMA for prostate cancer imaging

The FDA has awarded a fast track designation to ⁶⁴Cu-SAR-bisPSMA for PET imaging of prostate-specific membrane-antigen (PSMA)-positive prostate cancer lesions with suspected metastasis who are candidates for initial definitive therapy, Clarity Pharmaceuticals announced in a news release.¹

64Cu-SAR-bisPSMA is currently being assessed in the phase 3 CLARIFY trial.

Fast track designation is awarded to new drugs and vaccines that are intended to treat or prevent serious conditions and have the potential to address an unmet medical need. With this designation, the development process for ⁶⁴Cu-SAR-bisPSMA can benefit from more frequent engagement with the FDA, eligibility for accelerated approval, and priority review.

“Receiving Fast Track Designation for ⁶⁴Cu-SAR-bisPSMA is a significant milestone, especially as we are actively recruiting into our first registrational phase 3 trial, CLARIFY, and preparing for an End of Phase meeting with the FDA for a second pivotal phase 3 trial with this product,” said Clarity’s Executive Chairperson Alan Taylor, PhD, in the news release.¹ “The designation will allow us to work closely with the FDA to facilitate the development process, potentially accelerating the approval of this best-in-class diagnostic.”

The fast track designation for ⁶⁴Cu-SAR-bisPSMA is supported by findings from Clarity’s ongoing clinical program for the imaging agent. This program includes indications for patients with prostate cancer prior to radical prostatectomy, supported by the PROPELLER and CLARIFY trials, and in patients with biochemical recurrence, supported by the COBRA trial and a planned phase 3 trial.

The initial phase 1 PROPELLER trial (NCT04839367) demonstrated favorable safety and efficacy of the agent in patients with prostate cancer prior to radical prostatectomy. In total, the study enrolled 30 patients with prostate cancer who were set to undergo radical prostatectomy and lymph node dissection. The primary end points included safety, tolerability, and efficacy of the agent, and the secondary end point was to determine the optimal dose level for subsequent trials. The study also compared the diagnostic properties of ⁶⁴Cu-SAR-bisPSMA with that of ⁶⁸Ga PSMA-11 as an exploratory objective.^2,3

Overall, data from the trial showed that ⁶⁴Cu-SAR-bisPSMA was safe and well-tolerated among all patients in the study. The recommended dose was determined to be 200 MBq, as this cohort demonstrated the highest scores for imaging quality following review by 2 independent blinded central readers. In comparison with ⁶⁸Ga PSMA-11, ⁶⁴Cu-SAR-bisPSMA showed higher SUVmax values in patients who received the 200 MBq dose (n = 18).

Results from the PROPELLER trial led to the start of the registrational phase 3 CLARIFY trial (NCT06056830) in the same patient population. Recruitment for the CLARIFY trial is currently ongoing.

In total, the phase 3 trial plans to enroll 383 patients across multiple clinical sites in the United States and Australia. The study will assess the diagnostic performance of ⁶⁴Cu-SAR-bisPSMA in detecting regional node metastasis prior to radical prostatectomy in patients who have high-risk prostate cancer. Participants will be evaluated at 2 time points: day 1 (day of administration) and day 2 (approximately 24 hours after administration).

Final completion of the CLARIFY trial is expected for early 2025.⁴

In addition, ⁶⁴Cu-SAR-bisPSMA was also assessed in the phase 1/2 COBRA trial (NCT05249127), in which reported results have supported the safety and efficacy of the agent in detecting prostate cancer lesions in patients with biochemical recurrence.⁵ Overall, data showed that ⁶⁴Cu-SAR-bisPSMA was able to identify lesions in approximately 60% of patients on same-day imaging and up to 80% on next-day imaging in whom standard of care imaging was unable to detect any lesions.

Further, the correct detection rate (defined as the proportion of true positive patients who had at least 1 evaluable reference standard data point among all participants) ranged from 21.4% to 28.6% among 3 central readers on day 0 and 28.6% to 38.1% on day 1. The region-level positive predictive value (defined at the proportion of true positive regions ⁶⁴Cu-SAR-bisPSMA PET/CT scan with corresponding evaluable reference standard among all positive regions) ranged from 39.1% to 44.8% on day 0 and 32.7% to 43.3% on day 1 across all readers.

The findings from this study have informed planning for a second phase 3 registrational trial in this patient population.

“We believe that ⁶⁴Cu-SAR-bisPSMA could be a game changer in prostate cancer diagnosis,” Taylor concluded in the news release.¹ “[Fast track] designation highlights the potential of ⁶⁴Cu-SAR-bisPSMA to provide a novel diagnostic option for patients with prostate cancer and address the limitations of the current-generation diagnostic radiopharmaceuticals.”

References

1. Clarity receives FDA Fast Track Designation for 64Cu-SAR-bisPSMA. News release. Clarity Pharmaceuticals. Published online and accessed August 22, 2024. https://www.claritypharmaceuticals.com/news/fast-track/

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

3. PROPELLER trial results – SAR-bisPSMA safe, well tolerated and efficacious in the detection of prostate cancer. News release. Clarity Pharmaceuticals. February 14, 2023. Accessed August 22, 2024. https://www.claritypharmaceuticals.com/news/propeller_results/

4. Positron Emission Tomography Using 64Cu-SAR-bisPSMA in Participants With High-risk Prostate Cancer Prior to Radical Prostatectomy (CLARIFY). ClinicalTrials.gov. Last updated July 31, 2024. Accessed August 22, 2024. https://clinicaltrials.gov/study/NCT06056830

5. Initial COBRA results: Clarity’s SAR-bisPSMA is safe and highly effective in detecting tumours in prostate cancer patients. Phase 3 planning underway. News release. Clarity Pharmaceuticals. February 15, 2024. Accessed August 22, 2024. https://www.claritypharmaceuticals.com/news/cobra_results/