SAR-Bombesin Treatment in Prostate Cancer Begins

3D rendered illustration of prostate cancer | Image Credit: © SciePro | stock.adobe.com

The first patient has been dosed with the theranostic drug ⁶⁴Cu/⁶⁷Cu SAR-Bombesin in a phase 1/2 trial in metastatic castrate resistant prostate cancer (mCRPC). Clarity Pharmaceuticals, the drug’s manufacturer, reported that no issues were observed.

“We look forward to progressing the COMBAT trial and building on the compelling data from our preclinical and clinical studies to date,” said Alan Taylor, PhD, executive chairperson of Clarity Pharmaceuticals, in a press release. Taylor added that “we see a clear path to bringing SAR-Bombesin and SAR-bisPSMA to the prostate cancer population in need of novel treatments.”

SAR-Bombesin is a radiopharmaceutical that targets gastrin releasing peptide receptor (GRPR) that is present on multiple types of cancer cells, including breast, pancreas, and lung, and it is found in 100% of prostate cancers.¹

COMBAT (NCT05633160) is a dose escalation and cohort expansion trial for up to 38 patients. The study’s aim is to determine the safety and efficacy of SAR-Bombesin in patients with GRPR-expressing mCRPC and who are ineligible for therapy with ¹⁷⁷Lu-PSMA-617. The first patient was dosed with 6 GBq of SAR-Bombesin, and the trial is planning to investigate doses up to 14 GBq in up to 4 cycles, pending safety reviews. The study began in June 2023 and has an estimated completion date of May 2026.

The study is evaluating the maximum tolerated dose or maximum feasible dose of a single dose, the recommended dose of two doses, efficacy of SAR-Bombesin in prostate specific antigen response, efficacy of SAR-Bombesin in radiographic response, incidence of dose limiting toxicities, and incidence of treatment-emergent adverse events. Investigators are also monitoring the numbers of participants with changes from baseline in vital signs, electrocardiogram parameters, and laboratory results.

COMBAT is currently open for recruitment. Eligible patients are those with an ECOG performance status of 0-2, at least 1 metastatic prostate cancer lesion, positive ⁶⁴Cu-SAR-BBN PET/CT scan, castrate level of serum/plasma testosterone, and progressive mCRPC despite prior androgen deprivation therapy. Exclusion criteria includes symptomatic brain metastasis, prior history of leukemia or myelodysplastic syndrome, deep vein thrombosis or pulmonary embolism diagnosis, and previous treatment with any systemic anti-cancer therapy 4 weeks prior to enrollment.²

“SAR-Bombesin has already resulted in improvements in the management of prostate cancer for patients with PSMA-negative or low PSMA expressing lesions throughout diagnostic trials,” Taylor said.¹

Similar compounds, ⁶⁴Cu/⁶⁷Cu-SAR-bisPSMA, are also undergoing a phase 1/2 trial with an estimated enrollment of 44 participants (NCT04868604). The compounds are being evaluated for safety and efficacy in patients with PSMA-expressing mCRPC.³ The SABRE study (NCT05407311) is also evaluating SAR-Bombesin in a diagnostic context, and the study is estimated to finish this month.⁴

REFERENCES

1. Clarity Pharmaceuticals. First patient treated with Cu-67 SAR-Bombesin in theranostic prostate cancer trial. October 3, 2023. https://tinyurl.com/2anhuzrp

2. 64Cu-SAR-BBN and 67CU-SAR-BBN for identification and treatment of gastrin releasing peptide receptor (GRPR)-expressing metastatic castrate resistant prostate cancer in patients who are ineligible for therapy with 177Lu-PSMA-617 (COMBAT). ClinicalTrials.gov. Updated September 28, 2023. Accessed October 3, 2023. https://clinicaltrials.gov/study/NCT05633160

3. 64Cu-SAR-bisPSMA and 67CU-SAR-bisPSMA for identification and treatment of PSMA-expressing metastatic castrate resistant prostate cancer (SECuRE). ClinicalTrials.gov. Updated May 24, 2023. Accessed October 3, 2023. https://clinicaltrials.gov/study/NCT04868604

4. 64Cu-SAR-BBN for identification of participants with recurrence of prostate cancer (SABRE). ClinicalTrials.gov. Updated June 2, 2023. Accessed October 3, 2023. https://clinicaltrials.gov/study/NCT05407311