Head-to-head trial to compare 64Cu-SAR-bisPSMA and 68Ga-PSMA-11 PET/CT

The phase 2 Co-PSMA trial is set to evaluate the performance of ⁶⁴Cu-SAR-bisPSMA compared with that of standard-of-care ⁶⁸Ga-PSMA-11 PET/CT in the detection of prostate cancer recurrence, Clarity Pharmaceuticals announced in a news release.¹

The Co-PSMA trials plans to enroll a total of 50 patients.

⁶⁸Ga-PSMA-11 was approved by the FDA for PET imaging of prostate-specific membrane antigen (PSMA)-positive lesion in men with prostate cancer in December 2020. ⁶⁴Cu-SAR-bisPSMA was granted a fast track designation by the agency in August 2024.

In total, the prospective Co-PSMA study plans to include 50 patients. Those included in the comparative trial must have biochemical recurrence following radical prostatectomy and are being considered for curative salvage radiotherapy. The primary objective for the study is to compare the detection rate of sites of prostate cancer recurrence (measured by the number of lesions per patient) between the 2 agents.

The trial will be conducted at St. Vincent’s Hospital in Sydney, Australia and will be led by Louise Emmett, MD, FAANMS, FRACP, MBChB.

“Men with [biochemical recurrence] after radical prostatectomy have a window of opportunity for a cure with the use of external beam radiotherapy. In order to achieve that, we need to use highly sensitive imaging techniques that can accurately detect the site of disease recurrence when the prostate-specific antigen levels start to rise,” Emmett said in the news release.¹ “This could really help improve patients’ lives, and I am really looking forward to seeing whether the use of ⁶⁴Cu-SAR-bisPSMA has a significant management impact over the current standard ⁶⁸Ga-PSMA-11 PET/CT, detecting sites of disease recurrence more accurately.”

Emmett was previously the principal investigator for Clarity Pharmaceutical’s phase 1 PROPELLER trial (NCT04839367), which assessed the performance of ⁶⁴Cu-SAR-bisPSMA in patients with untreated prostate cancer. Overall, data showed favorable safety and efficacy of the agent in patients with prostate cancer prior to radical prostatectomy.^2,3 In total, the study enrolled 30 patients with prostate cancer who were set to undergo radical prostatectomy and lymph node dissection.

Data 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 ongoing registrational phase 3 CLARIFY trial (NCT06056830) in the same patient population. This trial is currently enrolling participants in the United States and Australia. The study plans to enroll a total of 383 adult patients.⁴

To be eligible for enrollment, patients must have untreated and histologically confirmed adenocarcinoma of the prostate, high-risk prostate cancer per National Comprehensive Cancer Center guidelines version 1.202327, and have elected to undergo radical prostatectomy with pelvic lymph node dissection.

For the study, participants will be evaluated at 2 time points: day 1 (day of administration) and day 2 (approximately 24 hours after administration). The primary end point for the study is the diagnostic performance of ⁶⁴Cu-SAR-bisPSMA PET to detect regional nodal metastases in patients with high-risk prostate cancer prior to radical prostatectomy, as assessed for up to 16 weeks.

Final completion of the study is anticipated for February 2025.

Reference

1. St Vincent’s Hospital to conduct head-to-head trial with Clarity’s SAR-bisPSMA diagnostic product. News release. Clarity Pharmaceuticals. November 18, 2024. Accessed November 19, 2024. https://www.claritypharmaceuticals.com/news/co-psma/

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 November 19, 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 November 5, 2024. Accessed November 19, 2024. https://clinicaltrials.gov/study/NCT06056830