Combination of monalizumab and cetuximab in recurrent or metastatic head and neck cancer patients previously treated with platinum-based chemotherapy and PD-(L)1 inhibitors.

6516 Background: Monalizumab is a first-in-class immune checkpoint inhibitor targeting Natural Killer Group 2A (NKG2A), which is expressed on subsets of Natural Killer (NK), gd T and tumor-infiltrating CD8+T cells. NKG2A blockade promotes innate anti-tumor immunity mediated by NK and CD8+T cells and enhances NK cell antibody-dependent cell-mediated cytotoxicity induced by cetuximab. In a Phase I study, the combination of monalizumab and cetuximab was well tolerated. In an initial expansion cohort 1 of 40 patients (pts) who had progressed after platinum-based therapy, we reported an overall response rate (ORR) of 27.5%, a 4.5 month median PFS and an 8.5 month median OS. In a subset of patients (n=18) previously treated with PD-(L)1 inhibitors (IO), corresponding results were 17%, 5.1, and 14.1 months, respectively (ESMO 2019). Here we present data from a second expansion cohort 2 (n=40) conducted specifically in the post-IO setting to independently confirm the cohort 1 results. Methods: Eligible patients had R/M SCCHN previously treated with platinum and a PD-(L)1 inhibitor. Pts received monalizumab 750 mg q2weeks and cetuximab according to the label until progression or toxicity. Cohort 2 was designed as a confirmatory multicenter single arm phase II study, with a pre-planned total of 40 patients. The primary endpoint was ORR assessed per RECIST 1.1. Results: As of January 31, 2020, 40 pts have been treated in cohort 2. Median follow-up is 7.3 months (range, 1.9-13.6+). Eight (8) pts have a confirmed partial response (PR); ORR is 20% [95% confidence interval: 11-35]. Median time to response is 1.6 months [1.6-5.3]. At the time of data analysis, 3 pts were still in PR and 3 pts had stable disease continue on treatment. PFS and OS are still immature. Conclusions: In pts previously treated with platinum and PD-(L)1 inhibitors, the combination of monalizumab and cetuximab demonstrated promising activity. The second extension cohort confirmed prospectively the ORR reported in cohort 1. A randomized phase III trial of monalizumab and cetuximab is planned in this platinum and IO-pretreated SCCHN population. Clinical trial information: NCT02643550 .