Trial launches of imaging agent for PSMA-negative prostate cancer patients

Enrollment has started for a phase 2 trial of ⁶⁴Cu SAR-Bombesin, an investigational PET-imaging agent for patients with biochemically recurrent prostate cancer that is PSMA-PET negative.¹

The phase 2 study is known as the SABRE trial, which stands for "Copper-64 SAR-Bombesin in Biochemical REcurrence of Prostate Cancer trial.” Clarity Pharmaceuticals, the developer of ⁶⁴Cu SAR-Bombesin, explained in a press release that the impetus for launching the trial was to address the unmet need faced by the approximately 20% of patients with biochemically recurrent prostate cancer who are PSMA-PET negative.² These patients are unable to respond to the burgeoning class of PSMA-targeted products and thus are left with few available treatment options.

The target of ⁶⁴Cu SAR-Bombesin is the Gastrin Releasing Peptide receptor (GRPr), which is found on prostate tumors as well as several other tumors. “As such, the product could offer valuable imaging and therapeutic options for not only PSMA-negative patients, but also the large number of patients that have the target receptor on their cancers,” Clarity noted in a press release.

Overall, the multicenter, single-arm, non-randomized, open-label SABRE trial (NCT05407311), aims to enroll up to 50 patients with PSMA-negative biochemically recurrent prostate cancer (known or suspected) following definitive therapy (eg, surgery or radiation). Safety and tolerability of ⁶⁴Cu SAR-Bombesin, as well as its effectiveness in accurately detecting prostate recurrence, are the primary outcome measures of the study.

Positive initial safety and efficacy data for ⁶⁴Cu SAR-Bombesin were shown in a pilot trial of the imaging agent in patients with breast cancer. Results from this trial were shared in an abstract presented at the 2022 ASCO Annual Meeting.³

"We are very excited to initiate patient accrual for the SABRE trial which will explore and validate the clinical benefits associated with the novel SAR-Bombesin agent. We have been investigating Bombesin for many years and believe it is an agent with high diagnostic and therapeutic potential. We hope this trial will inform us on the role of SAR-Bombesin in diagnosing disease in PSMA-negative prostate cancer patients by imaging patients on day of injection and at ~24 hours after injection, with the delayed imaging being a novel feature enabled by ⁶⁴Cu,” Andrei Iagaru, MD, lead principal investigator on the SABRE trial, and a professor of Radiology – Nuclear Medicine and chief of the Division of Nuclear Medicine and Molecular Imaging at Stanford University Medical Center, stated in a press release.¹

“In addition to investigating the clinical benefits of the product, we also look forward to leveraging centralized manufacture and on-demand delivery advantages of copper-based products. These features have potential to facilitate universal access to SAR-Bombesin and enhance accessibility to treatment facilities throughout the United States,” added Iagaru.¹

References

1. Recruitment opens for Phase II trial in prostate cancer with Cu-64 SAR-Bombesin in the US. Published online September 5, 2022. Accessed September 6, 2022. https://prn.to/3BhQNfh

2. IND approval from the US FDA for Phase II SAR-Bombesin imaging trial in prostate cancer. Published online June 6, 2022. Accessed June 9, 2022. https://prn.to/3NCLISI

3. Wong K, Sheehan-Dare G, Nguyen A, et al. 64Cu-SAR-Bombesin PET-CT imaging in the staging of ER+/PR+/HER2- metastatic breast cancer: Safety, dosimetry, and feasibility in a phase I trial. J Clin Oncol 40, no. 16_suppl (June 01, 2022) 3092-3092. doi: 10.1200/JCO.2022.40.16_suppl.3092