FDA authorizes trial of imaging agent for PSMA-negative prostate cancer patients

The FDA has approved an Investigational New Drug (IND) application allowing Clarity Pharmaceuticals to launch 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 will be known as the SABRE trial, which stands for "Copper-64 SAR-Bombesin in Biochemical REcurrence of Prostate Cancer trial." The company 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. 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 its news release.

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.

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.²

"We look forward to further progressing the development of SAR-Bombesin and hope it will provide a new and effective diagnostic option for prostate cancer patients. Building on the promising clinical and preclinical data acquired to date, we are also planning an IND submission for a theranostic trial in prostate cancer participants, using ⁶⁷Cu SAR-Bombesin therapy paired with the imaging agent, ⁶⁴Cu SAR-Bombesin,” Dr Alan Taylor, executive chairman of Clarity, stated in a news release.

Additional Clarity theranostic research

Clarity also has several ongoing trials exploring agents geared toward PSMA-positive patients with prostate cancer, such as the phase 1/2 COBRA trial exploring the PSMA-PET imaging agent

⁶⁴Cu SAR-bisPSMA in patients with biochemical recurrence of prostate cancer following definitive therapy (NCT05249127) and the phase 1/2 SECURE trial (NCT04868604), in which ⁶⁴Cu SAR-bisPSMA will be used for the selection of appropriate patients with metastatic castration-resistant prostate cancer to receive treatment with the PSMA targeted therapy ⁶⁷Cu SAR-bis-PSMA.

References

1. 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.

2. 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