FDA Grants FTD to 64Cu-SAR-bisPSMA for PET Imaging in Prostate Cancer

• The FDA has granted fast track designation (FTD) for ⁶⁴Cu-SAR-bisPSMA.
• This indication is for positron emission tomography (PET) imaging of prostate-specific membrane antigen (PSMA) positive prostate cancer lesions for the treatment of patients with biochemical recurrence (BCR) of prostate cancer after definitive therapy.
• The FDA’s FTD designation facilitates closer collaboration between Clarity Pharmaceuticals and regulatory authorities, potentially accelerating the development timeline and approval process.

The FDA has granted FTD to the investigational agent, ⁶⁴Cu-SAR-bisPSMA, for PET imaging of PSMA-positive prostate cancer lesions in patients experiencing BCR following definitive therapy.

⁶⁴Cu-SAR-bisPSMA is a novel diagnostic option that has shown superiority compared with current-generation radiopharmaceuticals. Preclinically, ⁶⁴Cu-SAR-bisPSMA exhibits superior tumor uptake vs PSMA-617, suggesting it may become a best-in-class theranostic agent for patients with prostate cancer.²

⁶⁴Cu-SAR-bisPSMA offers unique advantages over current PSMA PET imaging agents due to its bivalent structure and the longer half-life of copper-64 compared with the significantly shorter half-lives of gallium-68 and fluorine-18.¹ These properties promote enhanced flexibility for scheduling of imaging, improved diagnostic performance, and broader accessibility.

"Receiving the second FTD for ⁶⁴Cu-SAR-bisPSMA and well within the 60-day period following our application submission, reserved by the US FDA for review, is yet another significant milestone in our bisPSMA program. This highlights the high unmet need for novel diagnostics in prostate cancer and the high quality of data we presented to the FDA,” Alan Taylor, PhD, Clarity's executive chairperson, in a press release.

The FTD submission was supported by findings from the phase 1/2 COBRA study (NCT05249127), which evaluated the safety and diagnostic performance of ⁶⁴Cu-SAR-bisPSMA in patients with BCR who had inconclusive or negative standard-of-care (SOC) imaging.

The study demonstrated that next-day PET imaging with ⁶⁴Cu-SAR-bisPSMA identified localized disease in up to 80% of patients enrolled and detected lesions as small as 2 mm. The number of lesions identified on next-day imaging was nearly double compared with same-day imaging, further emphasizing the utility of this agent in early detection.

3D rendered medically accurate illustration of prostate cancer: © SciePro - stock.adobe.com

In the trial, the correct detection rate with ⁶⁴Cu-SAR-bisPSMA PET/CT improved from 21.4% to 28.6% on day 0 to 28.6% to 38.1% on day 1, while the region-level positive predictive value ranged from 39.1% to 44.8% on day 0 and 32.7% to 43.3% on day 1.³ Specificity in detecting cancer in pelvic lymph nodes was high, at a rage of 93.8% to 96.9% on day 0, though slightly reduced on day 1 (81.3%-87.9%). Patient-level detection rates increased from 44% to 58% on day 0 to 58% to 80% on day 1.

Notably, ⁶⁴Cu-SAR-bisPSMA identified lesions in up to approximately 60% of patients missed by standard imaging on the same day, increasing to 80% with next-day imaging. Delayed imaging resulted in a 91% median increase in lesion detection, particularly in pelvic lymph nodes, where total lesions detected more than doubled, from 53-80 on day 0 to 82-153 on day 1 (median increase, 108.3%).

For safety, the only reported treatment-related adverse event was a grade 2 worsening of type 2 diabetes, which was resolved. Importantly, the imaging findings prompted treatment plan changes in 48% of patients, with 67% receiving systemic and/or focal therapies. These results underscore the clinical value of delayed imaging in managing prostate cancer.

These findings pave the way for additional trials, including the phase 3 AMPLIFY registrational study, which aims to evaluate the diagnostic performance of ⁶⁴Cu-SAR-bisPSMA in approximately 220 patients with BCR.¹ The results from AMPLIFY will form the basis for an FDA approval submission.

Additionally, the Co-PSMA investigator-initiated trial, led by Louise Emmett, MD, MBChB, FRACP, FAANMS, at St. Vincent's Hospital Sydney in Australia, will compare ⁶⁴Cu-SAR-bisPSMA with SOC ⁶⁸Ga-PSMA-11 in detecting recurrent prostate cancer lesions.

"Being able to now fast-track the development of ⁶⁴Cu-SAR-bisPSMA for patients with BCR as well as for patients prior to initial definitive therapy is incredibly exciting. The news is especially timely as we are actively preparing to commence recruitment for our second registrational trial, AMPLIFY, in the coming months. The designation will allow us to work closely with the FDA to facilitate the development process and accelerate the approval of what could become a best-in-class diagnostic,” added Taylor in the press release.

REFERENCES:

1. Clarity receives U.S. FDA fast track designation for Cu-64 SAR-bisPSMA in biochemical recurrence of prostate cancer. News release. Clarity Pharmaceuticals. January 24, 2025. Accessed January 27, 2025. https://tinyurl.com/3vx9hk62

2. Pipeline. Clarity Pharmaceuticals. Accessed January 27, 2025. https://www.claritypharmaceuticals.com/pipeline/sar-bispsma/

3. 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 January 27, 2025. https://tinyurl.com/35nnsjt3