VIR-5500 Phase 1 Yields 82% PSA50, 53% PSA90 Declines and 45% ORR
Vir Biotechnology's VIR-5500 monotherapy showed no dose-limiting toxicities in 58 patients and manageable Grade ≥3 adverse events in 12%, with limited Grade 1 cytokine release in 50%. At ≥3,000 µg/kg Q3W, 82% achieved PSA50 and 53% PSA90 declines with 45% ORR; dose-expansion begins Q2 2026 ahead of Phase 3 trials in 2027.
1. Safety and Tolerability
Data from 58 metastatic prostate cancer patients receiving VIR-5500 monotherapy across dose-escalation cohorts demonstrated no dose-limiting toxicities to date. Treatment-related Grade ≥3 adverse events occurred in 12% (7/58) of patients and were manageable; cytokine release syndrome was limited to Grade 1 fevers in 50% without prophylactic steroids.
2. Dose-Dependent Efficacy
In the highest dosing cohort (≥3,000 µg/kg Q3W; n=22), 82% (14/17) of PSA-evaluable patients achieved ≥50% PSA declines and 53% (9/17) achieved ≥90% declines. Among 11 RECIST-evaluable patients, objective responses were observed in 45% (5/11), including four confirmed responses and tumor shrinkage across visceral lesions.
3. Development and Next Steps
Vir plans to initiate monotherapy dose-expansion in late-line mCRPC and combination expansion in early-line mCRPC and mHSPC in Q2 2026, aiming for pivotal Phase 3 trials in 2027. The company also scheduled a conference call today to discuss fourth quarter and full year 2025 financial results alongside the updated VIR-5500 data.