Safety and Efficacy of Intratumoural Anti-CTLA4 with Intravenous Anti-PD1

Why It Matters

Reducing severe toxicity expands eligibility for checkpoint‑inhibitor combos, potentially reshaping first‑line melanoma therapy and informing delivery strategies for other solid tumours.

Key Takeaways

• Intratumoural ipilimumab reduced grade 3‑4 toxicity to 24% vs 67% IV
• Objective response rate on injected lesions reached 66% with deep, durable responses
• Median progression‑free survival was 13.8 months; overall survival not reached
• Durable clinical benefit linked to pre‑existing MHC‑I/II tumor immunity

Pulse Analysis

Checkpoint inhibitors have transformed melanoma care, yet the combination of intravenous ipilimumab and nivolumab is hampered by high-grade toxicities in up to two‑thirds of patients. Researchers therefore explored a localized delivery model, injecting a ten‑fold lower dose of ipilimumab directly into tumours while maintaining standard nivolumab dosing. This approach leverages the Fcγ‑receptor‑mediated activity of ipilimumab at the tumour site, aiming to concentrate immune activation where it matters most and spare the rest of the body from systemic exposure. The concept aligns with a broader trend toward spatially precise immunotherapy, which seeks to maximize efficacy while minimizing collateral damage.

The NIVIPIT phase 1b trial enrolled 61 advanced melanoma patients across four sites, randomising two‑thirds to the intratumoural regimen. Safety outcomes were striking: only 24 % experienced grade 3‑4 adverse events, comfortably below the pre‑specified 30 % threshold, compared with 67 % in the intravenous control. Efficacy remained robust, with a 66 % objective response rate on injected lesions and a median progression‑free survival of 13.8 months. Biomarker work revealed that patients who achieved durable clinical benefit already possessed higher baseline expression of MHC‑I and MHC‑II molecules, and their tumours showed dynamic shifts in regulatory T‑cell and Fcγ‑receptor‑positive macrophage populations after treatment.

These findings suggest that intratumoural CTLA‑4 blockade can decouple efficacy from toxicity, potentially widening the therapeutic window for checkpoint‑inhibitor combos. If validated in larger, randomized studies, this strategy could become a new standard for melanoma and may be adaptable to other immunogenic cancers where systemic toxicity limits current regimens. Moreover, the identified immune signatures provide a roadmap for patient selection, enabling clinicians to target those most likely to derive lasting benefit from localized immunotherapy.