Clarity Pharmaceuticals' 64Cu-SAR-bisPSMA, a novel PET imaging agent, has received Fast Track designation from the FDA for imaging prostate-specific membrane antigen (PSMA)-positive prostate cancer lesions with suspected metastases eligible for initial definitive therapy. This designation aims to expedite the development and potential approval of this diagnostic agent.
PROPELLER Trial Results
Data from the phase 1 PROPELLER trial (NCT04839367), presented at the 2023 ASCO Annual Meeting, demonstrated a 100% primary prostate cancer detection rate by one reader and 85.7% by another among patients with histologically proven prostate cancer. The trial compared 64Cu-SAR-bisPSMA with the FDA-approved standard of care, 68Ga-PSMA-11, revealing greater uptake with the novel agent. Specifically, reader 1 median maximum standard uptake values (SUVmax) were 31.40 (IQR, 27.45) with 64Cu-SAR-bisPSMA versus 10.08 (IQR, 13.92) with 68Ga-PSMA-11. For reader 2, median SUVmax values were 41.00 (IQR, 46.09) versus 14.58 (IQR, 14.98), respectively (P < .001). Median tumor-to-background ratios (TBR) were also significantly higher with 64Cu-SAR-bisPSMA: 49.07 (IQR, 67.69) versus 21.91 (IQR, 35.71) with 68Ga-PSMA-11 (P = .0015) for reader 1, and 76.34 (IQR, 66.37) versus 23.90 (IQR, 33.05) (P < .001) for reader 2. The trial enrolled 30 adult male patients with previously untreated intermediate- to high-risk primary prostate cancer, assessing safety, tolerability, and efficacy as primary endpoints.
COBRA Trial Findings
The phase 1/2 COBRA trial (NCT05249127), presented at the 2024 ASCO Annual Meeting, evaluated 64Cu-SAR-bisPSMA in patients with prostate cancer with biochemical recurrence (BCR) and negative or equivocal standard of care imaging. The study found day 0 and day 1 detection rates of 44% to 58% (95% CI, 30.0%-71.8%) and 58% to 80% (95% CI, 43.2%-90.0%), respectively. Positive predictor values (PPVs) for days 0 and 1 were 71.4% to 87.5% (95% CI, 29.0%-99.7%) and 50.0% to 61.5% (95% CI, 15.7%-86.1%), respectively. The trial enrolled 52 patients, with 32 completing the study, and assessed safety, detection rate, and PPV as primary endpoints.
Clinical Implications
According to Alan Taylor, PhD, executive chairperson of Clarity Pharmaceuticals, 64Cu-SAR-bisPSMA has the potential to be a "game changer" in prostate cancer diagnosis. Its bisPSMA dual targeting structure and the longer half-life of copper-64 enable next-day imaging, demonstrating higher tumor uptake and retention, and the capability of detecting smaller lesions. Clarity Pharmaceuticals is actively recruiting for its registrational phase 3 trial, CLARIFY (NCT06056830), and preparing for an end-of-phase meeting with the FDA for a second pivotal phase 3 trial.
