Avelumab in patients with gestational trophoblastic tumors with resistance to polychemotherapy: Cohort B of the TROPHIMMUN phase 2 trial

There is a need for innovative treatments in women with gestational trophoblastic tumors (GTT) resistant to chemotherapy. The TROPHIMMUN trial assessed the efficacy of avelumab in patients with resistance to single-agent chemotherapy (cohort A), or to polychemotherapy (cohort B). Cohort B outcomes are reported here.In the cohort B of this phase 2 multicenter trial (NCT03135769), women with GTT progressing after polychemotherapy received avelumab 10 mg/kg intravenously every 2 weeks until human chorionic gonadotropin (hCG) normalization, followed by 3 consolidation cycles. The primary endpoint was the rate of hCG normalization enabling treatment discontinuation (2-stage Simon design).Between February 2017 and August 2020, 7 patients were enrolled. Median age was 37 years (range: 29-47); disease stage was I or III in 42.9% and 57.1%; FIGO score was 9-10 in 28.6%, 11 in 28.6%, and 16 in 14.3%, respectively. Median follow-up was 18.2 months. One patient (14.3%) experienced hCG normalization enabling treatment discontinuation. However, resistance to avelumab was observed in the remaining 6 patients (85.7%). The cohort B was stopped for futility. Grade 1-2 treatment-related adverse events occurred in 57.1%, most commonly fatigue (42.9%), nausea, diarrhea, infusion-related reaction, muscle pains, dry eyes (each 14.3%). The median resistance-free survival was 1.4 months (95% CI 0.7-5.3).Although avelumab is active in patients with single-agent chemotherapy-resistant GTT (cohort A), it was associated with limited efficacy in patients with resistance to polychemotherapy (cohort B). The prognosis of patients with polychemotherapy resistance remains poor, and innovative immunotherapy-based therapeutic combinations are needed.