UPDATE: Seven Complete Responses in a 19-Patient Cohort of 67Cu-SAR-bisPSMA Trial for mCRPC

A small but encouraging clinical dataset suggests that 67Cu-SAR-bisPSMA may produce substantial anti-tumour activity in patients with metastatic castration-resistant prostate cancer (mCRPC) who have exhausted multiple treatment options.

The findings come from the SECuRE clinical trial, in which 19 participants received treatment with 67Cu-SAR-bisPSMA at an 8 GBq dose.

Despite the advanced disease setting, treatment was associated with deep responses after a relatively small number of treatment cycles. The reported median number of cycles was 2.8, with a range of one to four cycles. Across the trial, seven participants achieved either undetectable disease or a complete response, based on assessments that included RECIST criteria, bone scans and prostate-specific antigen (PSA) results. Five of these responses occurred among patients treated in the 8 GBq cohorts.

Among evaluable patients treated at the 8 GBq dose level, almost one-third achieved a complete response and/or undetectable disease. PSA responses were also notable: 63% of patients experienced a PSA reduction of at least 50%, while more than one-quarter achieved a PSA90 response, corresponding to a reduction of at least 90%.

These results are particularly relevant because mCRPC can become increasingly difficult to control after progression on androgen-receptor pathway inhibitors and other systemic therapies. In this setting, the ability to induce profound responses with only a limited number of treatment cycles could have important clinical implications, although the current evidence remains preliminary and must be interpreted in light of the small patient population.

The reported safety profile of 67Cu-SAR-bisPSMA at 8 GBq was described as favourable. Adverse events were mostly mild to moderate, transient and manageable. A favourable balance between anti-tumour activity and tolerability could support the evaluation of the treatment in earlier stages of prostate cancer, where the therapeutic objective may include delaying progression, reducing tumour burden and improving long-term outcomes.

67Cu-SAR-bisPSMA is a radioligand therapy designed to target prostate-specific membrane antigen (PSMA), a protein that is highly expressed in many prostate cancer cells. The molecule combines a bivalent “bis” structure, intended to enhance target binding, with copper-67, a radioactive beta emitter capable of delivering therapeutic radiation to PSMA-expressing tumour cells. Its sarcophagine-based chelating technology is designed to securely bind the copper isotope, supporting the development of the compound for both diagnostic and therapeutic applications.

The same molecular platform has been investigated across several stages of prostate cancer, including imaging in patients before prostatectomy, detection of biochemically recurrent disease and treatment of advanced mCRPC. This theranostic approach could allow clinicians to identify PSMA-expressing lesions diagnostically and subsequently use a related radioligand to deliver targeted radiation to those lesions.

Source.