Study of imaging agent for PSMA-negative prostate cancer hits enrollment goal

The target enrollment has been met for the phase 2 SABRE trial (NCT05407311) exploring the feasibility of the novel PET-imaging agent ⁶⁴Cu SAR-Bombesin in patients with PSMA-negative biochemically recurrent prostate cancer.¹

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

Clarity Pharmaceuticals, the developer of ⁶⁴Cu SAR-Bombesin, explained in a news 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 news release.²

"We are very excited to have successfully imaged 50 participants in the SABRE trial which further explores the clinical benefits of the innovative SAR-Bombesin product. Preclinical and clinical findings thus far indicate that SAR-Bombesin holds significant potential for improving the diagnosis and treatment of prostate cancer, giving hope to clinicians and patients who have no other suitable diagnostic options available. Being able to now visualize the GRPr expressing lesions with SAR-Bombesin has the potential to change the entire treatment paradigm for patients. With more tools to detect prostate cancer that may not be visible with other imaging agents, we may be able to better diagnose and offer more effective treatment for their disease,” Andrei Iagaru, MD, lead principal investigator for the SABRE trial, commented, in a news release.¹

"Unique to Clarity's SAR Technology is the ability to image patients at later timepoints due to the optimal half-life of ⁶⁴Cu. As such, ⁶⁴Cu-SAR-Bombesin enables imaging not only on the day of product administration, but also at later timepoints, which may add utility to the diagnosis of cancerous lesions. We look forward to analyzing data from the SABRE trial in hopes of continuing to validate the benefits associated with this agent and better managing the patients that have few options at present in the face of a devastating diagnosis,” added Iagaru.

Overall, the multicenter, single-arm, non-randomized, open-label SABRE trial 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.¹

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 pleased to have reached our recruitment target in our phase 2 SABRE trial with the ⁶⁴Cu-SAR-Bombesin imaging product. SAR-Bombesin has already resulted in improvements to the management of prostate cancer for patients with PSMA-negative or low PSMA expressing lesions through our clinical program. We believe this product has immense potential, both as a theranostic and as a stand-alone diagnostic, as it targets GRPr, which is present in a number of cancers, potentially broadening its use beyond PSMA-negative prostate cancer,” Dr Alan Taylor, executive chairman of Clarity, stated in a news release.¹

"The successful C-BOBCAT and BOP investigator-initiated trials have already showed the utility of SAR-Bombesin and its potential to identify disease in some patient subgroups where conventional diagnostic imaging has failed. We look forward to reporting further data relating to the potential advantages of SAR-Bombesin and, subject to these results, moving this product into a registrational phase 3 trial," added Taylor.

References

1. Clarity Pharmaceuticals. Recruitment target achieved for Phase II SAR-Bombesin prostate cancer trial. Published online and accessed November 7, 2023. https://www.prnewswire.com/news-releases/recruitment-target-achieved-for-phase-ii-sar-bombesin-prostate-cancer-trial-301979503.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