Phase I Study of Mogamulizumab in Combination with Pembrolizumab in Patients with Relapsed or Refractory Non-Hodgkin Lymphoma—A National Cancer Institute Experimental Therapeutics Clinical Trials Network (NCI-ETCTN) Trial

<b>Introduction</b>: Immune evasion through inhibition of effector T cells is a key survival mechanism of lymphoma cells. We hypothesized that reinstating effector T cell activity through concurrent inhibition of the PD1/PD-L1 axis and of Treg activity will result in a synergistic anti-tumor effect with an acceptable toxicity profile. <b>Methods</b>: Phase I multi-institutional NCI-ETCTN trial aimed to evaluate the safety and tolerability of the combination of mogamulizumab and pembrolizumab in relapsed or refractory non-Hodgkin lymphoma. The study used a 3 + 3 design. Treatment consisted of mogamulizumab 1 mg/kg on days 1, 8, and 15 of cycle 1, followed by 1.5 mg/kg on day 1 of each subsequent 21-day cycle in combination with pembrolizumab 200 mg on day 1 of each cycle. A de-escalation level was defined as a 50% reduction in the dose of mogamulizumab (registered in clinicaltrials.gov NCT03309878). <b>Results</b>: The study was discontinued early, after treating seven patients (two angioimmunoblastic T cell lymphoma, four transformed follicular lymphoma, and one diffuse large B cell lymphoma of germinal center subtype) for concerns of futility and non-tolerability. Only two patients completed the first two cycles of treatment. Three patients presented with an early progression and three withdrew consent in the setting of general deterioration with clinically suspected progression. All six patients expired shortly after withdrawal from the study. The remaining patient experienced stress cardiomyopathy during the third cycle and was taken off the study. <b>Discussion</b>: In striking difference to the observation in solid malignancies, the combination of mogamulizumab with pembrolizumab was associated with low tolerability and suspected hyper-progression in patients with lymphoma.