Promising Imaging Results Seen With 64Cu SAR-Bombesin in Prostate Cancer

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Favorable imaging data were observed in a phase 2 diagnostic investigator-initiated trial of ⁶⁴Cu SAR-Bombesin for the treatment of patients with prostate cancer (BOP; NCT05613842).¹

The BOP trial enrolled 2 different groups of male patients, those with biochemical recurrence (BCR) of their prostate cancer who have negative PSMA PET imaging scans or low PSMA expression disease, and patients with metastatic castration-resistant prostate cancer (mCRPC) who are not suitable for PSMA therapy. Those enrolled received ⁶⁴Cu SAR-Bombesin at the mean dose of 210 MBq and were imaged with PET at 1-, 3-, and 24-hours post-administration of the product.

Data presented at the European Association of Nuclear Medicine 2023 Congress showed that no adverse events were reported among patients treated with ⁶⁴Cu-SAR-Bombesin. Additionally, 64Cu SAR-Bombesin PET avid disease was identified in over 30% of patients with negative or equivocal standard-of-care (SOC) PSMA PET (8/25; 32% detection rate).

“We are pleased with the results we have generated in the BOP trial, which have shown that ⁶⁴Cu SAR-Bombesin can detect lesions in men with biochemically recurrent prostate cancer that are negative or equivocal on PSMA PET. We believe SAR-Bombesin has the potential to add value in biochemical recurrence of prostate cancer following definitive therapy. We look forward to continuing our collaboration with Clarity and exploring the diagnostic and therapeutic benefits of SAR-Bombesin in not only prostate cancer, which is PSMA negative, but also in other diseases such as breast cancer,” Louise Emmett, PhD, St Vincent’s Hospital Sydney, and principal investigator in the BOP trial, in a press release.

“What is most exciting about this data is the identification of lesions in the most difficult to treat patient group, who are negative on all other SOC imaging. This information arms clinicians with accurate diagnostic information and helps them determine the best course of treatment for their patients. In essence, for the patients that have had a positive SAR-Bombesin scan, this is the difference between having an incorrect negative cancer diagnosis leading to cancer progression and now having an effective treatment plan that may lead to long term remission,” said Alan Taylor, executive chairman of Clarity Pharmaceuticals, in a press release. “This patient-centric approach, reinforced by the flexibility in the timing of the scan, centralized product manufacture and its broad distribution to any imaging center with a PET camera, would be a true paradigm shift in the management of prostate cancer.”

In the BOP trial, most patients in the BCR cohort had undergone radical prostatectomy (96%) with prostate specific antigen (PSA) doubling time of 4.2 months (range, 2.8-7.5; PSA mean 0.69 ng/ml; range, 0.28-2.45) prior to study entrance.

Those eligible for enrollment in the study were male patients aged 18 years and older with hormone-sensitive disease, who demonstrate rising PSA levels (>0.2ng/ml) after definitive therapy and a negative ⁶⁸Ga-PSMA-11 PET scan.² Male patients with mCRPC who are being considered for ¹⁷⁷Lu-PSMA-617 therapy, with known metastatic disease on conventional imaging and sites with low PSMA expression on ⁶⁸Ga-PSMA-11 PET scan in the presence of disease volume of > 1 cm are eligible for enrollment.

Patients with significant inter-current acute illness, an ECOG performance status greater than 2, who have had major surgery within 6 weeks prior to screening visit, eGFR < 40 mL/min/1.73 m², and a history of significant active cancers requiring treatment other than prostate cancer as per investigator discretion were not eligible to enroll in the study.

The primary end point of the study was to assess the diagnostic potential of the agent with secondary end points aiming to assess the diagnostic value, quantitative findings, and optimal timing for imaging post BBN injection with a 1 hour and 3 hours image.

“We are continuing to work diligently on the development of the SAR-Bombesin product in the [United States], including our phase 2 SABRE trial [NCT05407311] as well as the theranostic phase 1/2a COMBAT trial [NCT05633160], in order to make this product available to the patients who need it most and might not have any other diagnostic and therapeutic options available to them,” added Taylor.²

REFERENCES:

1. BOP preliminary trial results presented at EANM 2023 conference. News release. Clarity Pharmaceuticals. September 13, 2023. Accessed September 14, 2023. https://tinyurl.com/ym69dwv

2. Copper-64 SAR bombesin PSMA negative prostate cancer (BOP) (BOP). ClinicalTrials.gov. Updated January 10, 2023. Accessed September 14, 2023. https://classic.clinicaltrials.gov/ct2/show/NCT05613842