Fast Track Designation Given to Novel PET Imaging Agent in Prostate Cancer

The imaging agent led to changes in intended treatment plans for 48% of patients with prostate cancer and biochemical recurrence after definitive therapy.

64Cu-SAR-bisPSMA has received fast track designation from the FDA for the PET imaging of patients with a biochemical recurrence of prostate cancer following definitive therapy who are harboring prostate-specific membrane antigen (PSMA)–positive prostate cancer lesions, a press release from the developer, Clarity, stated.1

Previously, in August 2024, 64Cu-SAR-bisPSMA received fast track designation for patients with suspected metastasis of prostate cancer who are also candidates for initial definitive therapy.1

Data supporting the FDA’s decision primarily comes from the phase 1/2 COBRA study (NCT05249127) evaluating the safety and efficacy of 64Cu-SAR-bisPSMA, as well as the tool’s capability of detecting prostate cancer recurrence in those who have biochemical recurrence of prostate cancer after definitive therapy.

“This designation highlights the unique opportunity for 64Cu-SAR-bisPSMA in this very large market by addressing the limitations of the current-generation diagnostic radiopharmaceuticals and providing patients with prostate cancer with a more accurate diagnosis leading to more optimal treatment options,” Alan Taylor, PhD, executive chairperson at Clarity, said in the press release.1 “As such, we are fully committed to advancing the development of this best-in-class product to address the critical need for more accurate and accessible diagnostic tools in prostate cancer management.”

Results from the COBRA trial were presented at the 2024 American Society of Clinical Oncology (ASCO) Annual Meeting.3

64Cu-SAR-bisPSMA PET, on day 0, had a detection rate (DR) in positive patients of 44% to 58%, and of 58% to 80% on day 1; in equivocal patients, the DR was 4% to 12% on day 0 and 0% to 14% on day 1; and in negative patients, it was 30% to 50% on day 0 and 12% to 42% on day 1. The authors noted that, on day 1, 34% more patients had correct 64Cu-SAR-bisPSMA scans.

The correct detection rate (CDR) in true positive patients was 21.2% to 28.6% (95% CI, 10.3%-44.6%) on day 0 and 28.6% to 38.1% (95% CI, 15.7%-54.4%) on day 1.

In 48% of patients, results from 64Cu-SAR-bisPSMA imaging led to clinicians changing their intended treatment plant.

From day 0 to day 1, the total number of identified lesions increased from 70 on day 0 to 129 on day 1, an 82% increase. The median number of lesions identified per patient with a positive scan was 1 (range, 1-15) on day 0 and 1 to 2 (range, 1-15) on day 1.

The predictive positive value (PPV) in true positive regions was 4.6% to 7.2% on day 0 and 6.7% to 8.7% on day 1; in false positive regions, it was 7.2% to 10.3% on day 0 and 8.7% to 18.0% on day 1; the overall PPV was 39.1% to 44.8% (95% CI, 19.7%-64.3%) on day 0 and 32.7% to 43.3% (95% CI, 20.3%-62.6%) on day 1.

Regarding safety, 17.3% (n = 9) of patients experienced at least one treatment-emergent adverse event (TEAE) unrelated to the trial treatment, and 1.9% (n = 1) experienced a TEAE related to treatment, which was worsening type 2 diabetes mellitus.

A total of 52 patients received 64Cu-SAR-bisPSMA and were included in the safety analysis, 50 of whom followed up. All patients received 200 MBq (5.4 mCi) of 64Cu-SAR-bisPSMA injection then had a PET/CT scan 1 to 4 hours after injection on day 0 and then 24 hours (plus or minus 6 hours) after injection on day 1.

Patients had to have confirmed adenocarcinoma of prostate with subsequent definitive therapy and suspected recurrence of prostate cancer based on rising or detectible prostate-specific antigen levels. Additionally, patients were required to have negative or equivocal findings for prostate cancer on conventional imaging per standard of care within 60 days of study treatment day 0.

The trial’s primary end points were the safety and tolerability of 64Cu-SAR-bisPSMA and the ability of 64Cu-SAR-bisPSMA PET/CT to correctly identify recurrence of prostate cancer. PET/CT imaging scans were assessed by 3 independent, blinded, central readers and judged against a composite reference standard determined by an independent, blinded, central expert panel.

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/nhk7p64b
2. Clarity receives FDA Fast Track Designation for 64Cu-SAR-bisPSMA. News release. Clarity Pharmaceuticals. August 22, 2024. Accessed January 27, 2025. https://tinyurl.com/2hw9bumt
3. Nordquist L, Lengyelova E, Saltzstein D, et al. COBRA: assessment of safety and efficacy of 64Cu-SAR-bisPSMA in patients with biochemical recurrence of prostate cancer following definitive therapy. J Clin Oncol. 2024;42(suppl 16):5100. doi:10.1200/JCO.2024.42.16_suppl.5100