Safety and efficacy of intratumoural anti-CTLA4 with intravenous anti-PD1.

Abstract

Intravenous administration of anti-CTLA4 with anti-PD1 provides durable tumour responses but causes severe treatment-related adverse events in patients with cancer¹. Intratumoural administration at lower doses but high local concentrations could enhance antitumour efficacy while minimizing systemic exposure and toxicity. Here we report the randomized multicentre phase 1b NIVIPIT trial (ClinicalTrials.gov: NCT02857569 ), which enrolled 61 patients with untreated metastatic melanoma, randomly assigned 2:1 to receive intravenous nivolumab (anti-PD1; 1 mg kg^-1) combined with either intratumoural ipilimumab (anti-CTLA4; 0.3 mg kg^-1) or intravenous ipilimumab (3 mg kg^-1). The primary end-point was met with significantly lower incidence of grade 3 or 4 treatment-related adverse events at 6 months in the intratumoural versus intravenous arm (22.6% versus 57.1%), equivalent to anti-PD1 monotherapy. RECIST (response evaluation criteria in solid tumours) best objective response rate reached 65.7% for anti-CTLA4 injected lesions and 50% for uninjected lesions, confirming the relationship between intratumoural exposure to anti-CTLA4 and efficacy. Baseline tumour immune profiling revealed that protumoural activated regulatory T (T_reg) cells and M2 macrophages predict durable clinical benefit, regardless of the anti-CTLA4 administration route. A decrease in activated intratumoural T_reg cells occurred only in patients who showed durable clinical benefit, who also presented high intratumoural Fcγ receptor (FcγR) expression. Our results provide a rationale for intratumoural anti-CTLA4 strategies in oligometastatic and early-stage cancers and indicate that high intratumoural activated T_reg cell and FcγR⁺ M2 macrophage numbers are prerequisites for efficacy of combined anti-CTLA4 and anti-PD1.