A phase II basket trial of Dual Anti-CTLA-4 and Anti-PD-1 Blockade in Rare Tumors (DART) SWOG S1609: vaginal cancer sub cohort results.

[OBJECTIVE] The SWOG S1609 Dual Anti-CTLA-4 & Anti-PD-1 blockade in Rare Tumors (DART) trial is the first basket study to include a sub-cohort assessing ipilimumab and nivolumab in patients with primary vaginal cancers with differing histology.

[METHODS] DART is a prospective, open-label, multicenter, multi-cohort phase II clinical trial of ipilimumab (1 mg/kg intravenously) 6 weekly plus nivolumab (240 mg intravenously) 2 weekly across multiple rare tumor cohorts, with the vagina cohort (any vaginal histology) reported here. The primary endpoint was objective response rate (ORR) per RECISTv1.1; progression-free survival (PFS), overall survival (OS), clinical benefit rate (CBR; overall response plus stable disease [SD] ≥6 months), and toxicity are secondary endpoints.

[RESULTS] Seven evaluable patients (median age, 60 years; performance status 0-1; no prior exposure to immunotherapy) were analyzed, of whom 3 had adenocarcinoma, 2 had squamous cell carcinoma (SCC), one had small-cell carcinoma and one had undifferentiated histology. The ORR was 29%, with 1 patient (14%) with undifferentiated histology achieving complete response (lasting 14.8 months) and 1 patient with SCC histology (14%) attaining a partial response (lasting 45.2 months). The CBR was 43%. The 6-month PFS rate was 43% and the median OS was 11.7 months. Five patients (71.4%) experienced an adverse event (AE) with 4 (57.1%) having grade 3-4 AE's.

[CONCLUSION] Ipilimumab plus nivolumab showed efficacy (ORR was 29% and CBR of 43%) and durability (one patient with prolonged SD >6 months) in a sub cohort of patients with vaginal cancer of differing histology without new safety signals.

[TRIAL REGISTRATION] ClinicalTrials.gov Identifier: NCT02834013.