Strong enrollment reported for study of imaging agent for PSMA-negative prostate cancer

Half of the enrollment goal has been met for the phase 2 SABRE trial, which is exploring the novel PET-imaging agent ⁶⁴Cu SAR-Bombesin in patients with PSMA-negative biochemically recurrent prostate cancer.¹

"SAR-Bombesin has already resulted in improvements to the management of prostate cancer for patients that are PSMA-negative or have low PSMA expressing tumors and we hope to confirm its safety and efficacy in our clinical programs," Dr Alan Taylor, executive chairman, Clarity Pharmaceuticals, stated in a press release.

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.²

"We have been working on Bombesin for many years now and I am very excited with the progress of the SABRE trial and the continued exploration and validation of the clinical benefits associated with the SAR-Bombesin agent. It gives hope to clinicians and patients who have no other suitable diagnostic options available due to their cancers having low or no PSMA expression,” Andrei Iagaru, MD, lead principal investigator for the SABRE trial, commented in a press release.¹

“Being able to visualize the disease can change the entire treatment paradigm for these patients. Once we can see the cancer, clinicians can then find the most suitable therapeutic regiment to maximize treatment outcomes. Based on the promising preclinical and clinical data to date, SAR-Bombesin is an exciting new product for better managing these patients that have few options at present in the face of a devastating diagnosis. We look forward to recruiting the remaining 25 patients in the trial and further analyzing the trial data," added Iagaru.

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 continue to build significant positive data on our SAR-Bombesin product. In addition to the SABRE trial, we are actively recruiting participants to our theranostic trial, COMBAT, and have recently finished recruitment into an investigator initiated Phase II diagnostic trial, BOP, with this product. Subject to the outcome of the SABRE trial, Clarity is planning to launch a pivotal Phase III diagnostic trial for first product approval in the United States,” Clarity's Executive Chairman, Dr Alan Taylor, stated in a press release.¹

"SAR-Bombesin has already resulted in improvements to the management of prostate cancer for patients that are PSMA-negative or have low PSMA expressing tumors and we hope to confirm its safety and efficacy in our clinical programs. We look forward to progressing the development of SAR-Bombesin and potentially providing a large patient population with accurate and precise detection and treatment of their prostate cancer,” added Taylor.

References

1. Clarity reaches 50% recruitment milestone for Phase II SABRE prostate cancer trial. Published online and accessed July 24, 2023. https://www.prnewswire.com/news-releases/clarity-reaches-50-recruitment-milestone-for-phase-ii-sabre-prostate-cancer-trial-301883828.html

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