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

Abstract Intravenous anti-CTLA4 with anti-PD1 provides durable tumor responses but generates high rates of severe immune-related adverse events (irAEs) in cancer patients1-3. As opposed to anti-PD1 antibodies, anti-CTLA4 efficacy and toxicity is dose dependent, which limits its use in many patients and restricts broader application, particularly in localized cancers. Therefore, administering lower doses of anti-CTLA4 but directly into tumors and at high local concentrations could enhance anti-tumor efficacy while minimizing systemic exposure and toxicity. Conversely, stronger activation of tumor infiltrating lymphocytes could increase systemic toxicity in case of cross-reactivity with healthy tissue antigens. To challenge those hypothesis we launched a randomized multicenter Phase 1b NIVIPIT trial (NCT02857569), where 61 patients untreated metastatic melanoma patients were randomly assigned 2:1 to receive intravenous nivolumab (1mg/kg) in combination with either intratumoral (IT) ipilimumab (0.3mg/kg) or intravenous (IV) ipilimumab (3mg/kg). The primary endpoint was met with a significantly lower incidence of grade ≥ 3 irAEs at 6 months in the IT arm vs the IV arm (22.6% vs 57.1%), equivalent to anti-PD1 monotherapy, thereby demonstrating the safety of this approach. The RECIST 1.1 best objective response rate was 65.7% for anti-CTLA4 injected tumor lesions, and 50% for the non-injected lesions demonstrating an increased efficacy upon intratumoral anti-CTLA4 therapy. Baseline tumor immune profiling revealed that, unexpectedly, protumoral activated Tregs and M2 macrophages, were alongside HLA-I & II mediated adaptive T- & B-cells anti-tumor immunity predicting durable clinical benefit regardless of the anti-CTLA4 administration route. Upon anti-CTLA4 + anti-PD1 immunotherapy, intratumoral activated Tregs decrease and tumor-secreted Granzymes increase was found only in patients with durable clinical benefit. Our results provide the rationale for developing intratumoral anti-CTLA4 immunotherapy strategies in oligo-metastatic and earlier-stage cancers to avoid toxicities and suggest that persisting intratumoral regulatory–effector immune interface with high Tregs and M2 macrophages is a pre-requisite for anti-CTLA- 4 + anti-PD1 efficacy. Trial registration: ClinicalTrials.gov Identifier, NCT 02857569