A new immunotherapy called VIR-5500 is offering hope for patients with metastatic castration-resistant prostate cancer (mCRPC), a highly aggressive and treatment-resistant form of the disease. In an ongoing Phase 1 trial, this dual-masked T-cell engager has demonstrated both safety and efficacy, positioning itself as a potential game-changer for advanced prostate cancer treatment.

The trial included 12 participants who received VIR-5500 at doses starting from 120 µg/kg. Early results revealed that 100% of patients showed a reduction in prostate-specific antigen (PSA),  58% of patients experienced a PSA50 response, meaning their PSA levels dropped by at least 50%.

Such significant reductions in PSA levels suggest the drug is effectively targeting the cancer and slowing its progression, even in cases where other therapies have failed.

What sets VIR-5500 apart is its innovative dual-masking technology, designed to target prostate-specific membrane antigen (PSMA), a protein found in abundance on prostate cancer cells. By engaging T cells only when PSMA is detected, the therapy minimizes off-target effects and reduces the risk of harming healthy tissues. This precision targeting is a major advancement in T-cell therapy, which has previously been limited by challenges like cytokine release syndrome (CRS), a potentially dangerous immune response. In this trial, CRS cases were minimal and low-grade, while no dose-limiting toxicities were reported, even at doses up to 1000 µg/kg.

The ongoing trial will continue to evaluate the drug’s safety and efficacy, with researchers looking at higher doses and additional measures like progression-free and overall survival. If these positive trends hold, VIR-5500 could mark a significant leap forward in the treatment of advanced prostate cancer.

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