A combination of PD-1 and TIGIT immune checkpoint inhibitors elicits a strong anti-tumour response in mesothelioma

BACKGROUND: Finding effective and curative treatment for mesothelioma remains challenging. While the introduction of immunotherapy combinations using ipilimumab (anti-CTLA-4) and nivolumab (anti-PD-1) have offered hope for some patients, a large proportion of mesothelioma cases, particularly the epithelial subtype, have minimal benefit from this. 

METHODS: Our study was inspired by the results of the AdvanTG-105 phase I clinical trial, which showed partial response with anti-TIGIT/PD-1 treatment in two epithelioid mesothelioma patients. Here, we conducted a comprehensive in vivo experiment involving eight animal treatment groups administered with either PBS (control group), cisplatin/pemetrexed, anti-PD-1, anti-PD-1 + anti-CTLA-4, anti-TIGIT, anti-PD-1 + anti-TIGIT, anti-PD-1 + anti-CTLA-4 + anti-TIGIT, and cisplatin/pemetrexed + anti-PD-1 + anti-TIGIT. 

RESULTS: Our results indicate that animals receiving anti-PD-1 + TIGIT exhibited a superior anti-tumour response, with 90% of the treatment group exhibiting an objective response, compared to 60%, 20% and 40% for the standard-of-care anti-PD-1 + CTLA-4, single-agent anti-PD-1 and cisplatin/pemetrexed treatment groups, respectively. Animals receiving anti-PD-1 + TIGIT displayed a significantly reduced average tumour size, with improved weight and survival rates, and fewer adverse effects than those receiving anti-PD-1 + CTLA-4 treatment. Anti-PD-1 + TIGIT-treated animals achieved complete tumour regression, with heightened effector CD8 + T cell and NK cell activity, remaining tumour-free for over 300 days without immune-related adverse events. After initial tumour elimination, anti-PD-1 + TIGIT-treated animals showed no tumour regrowth in the rechallenge experiment. 

CONCLUSION: These findings provide rationale for the development of an anti-PD-1 + TIGIT combination immunotherapy trial for mesothelioma patients.