For patients with low or absent Prostate-Specific Membrane Antigen (PSMA) expression, effective treatment options for prostate cancer can be limited. This population often faces challenges because PSMA-targeted therapies, a cornerstone in metastatic prostate cancer treatment, may not be effective. To address this unmet need, new radiopharmaceuticals are emerging as promising candidates. Among them, ⁶⁷Cu-SAR-bisFAP and ⁶⁷Cu-SAR-Bombesin offer potential solutions tailored to unique molecular profiles.

In addition to their standalone potential for low PSMA-expressing prostate cancer, ⁶⁷Cu-SAR-bisFAP and ⁶⁷Cu-SAR-Bombesin could complement PSMA-targeting therapies in tumors that do express PSMA.

⁶⁷Cu-SAR-Bombesin: Targeting GRPr in Prostate Cancer

For prostate cancer patients with low PSMA expression, ⁶⁷Cu-SAR-Bombesin presents another innovative option. This radiopharmaceutical targets the Gastrin-Releasing Peptide receptor (GRPr), a protein highly expressed in many solid tumors, including prostate cancer.

• Clinical Trials: ⁶⁷Cu-SAR-Bombesin is already in Phase 1 clinical trials, where early results have demonstrated its safety and potential efficacy. The trial focuses on its use in metastatic castration-resistant prostate cancer (mCRPC), particularly in patients not suited for PSMA-targeted therapies.
• Mechanism of Action: By binding to GRPr, ⁶⁷Cu-SAR-Bombesin delivers a targeted dose of radiation to cancer cells, potentially shrinking tumors while sparing healthy tissue.
• Significance for Low PSMA Cases: This approach is especially promising for patients who lack sufficient PSMA expression for other therapies, addressing a critical gap in treatment.

⁶⁷Cu-SAR-bisFAP: A New Therapeutic Horizon

⁶⁷Cu-SAR-bisFAP (Fibroblast Activation Protein) is designed to target the fibroblast activation protein, a marker commonly found in the tumor microenvironment, particularly in cancer-associated fibroblasts. These cells are abundant in various solid tumors, including prostate cancer, and contribute to cancer progression by remodeling the surrounding tissue and promoting metastasis.

• Clinical Development: ⁶⁷Cu-SAR-bisFAP is expected to enter clinical trials by the end of 2025. As a theranostic agent, its copper-67 isotope allows for both imaging and treatment, making it a versatile tool in personalized cancer care.
• Relevance to Low PSMA-Expressing Prostate Cancer: By targeting FAP rather than PSMA, this agent bypasses the need for PSMA expression, providing a potential alternative for patients who do not benefit from PSMA-directed therapies.
• Potential Impact: If successful in clinical trials, ⁶⁷Cu-SAR-bisFAP could redefine the treatment landscape for prostate cancer by addressing the tumor microenvironment rather than solely targeting the cancer cells.

The development of ⁶⁷Cu-SAR-bisFAP and ⁶⁷Cu-SAR-Bombesin marks a significant step forward in the management of prostate cancer.

As clinical trials progress, these radiopharmaceuticals hold the promise of transforming care for an underserved patient group, offering new hope for better outcomes and improved quality of life. For now, the prostate cancer community eagerly anticipates further data from ongoing and upcoming studies.

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