The combination of trabectedin and anti–PD-1 therapy may synergistically attack tumor cells and promote antitumor immunity. This pilot feasibility study was conducted to assess the safety, toxicity, and efficacy of this combination in patients with advanced soft-tissue sarcoma (STS). Each patient received 1 dose of trabectedin (1.5 mg/kg continuous intravenous infusion [CIV] for 24 hours) followed 3 weeks later by trabectedin CIV in combination with nivolumab (3 mg/kg intravenously over 30 minutes) every 3 weeks. Baseline and follow-up cross-sectional imaging were performed after every 2 cycles of combination therapy. Tumor response was assessed by RECIST 1.1 and immune-related response criteria (irRC). All 13 patients with STS who were evaluable for response at the time of reporting had metastatic disease and had received a median of 4 prior systemic therapies. Among these 13 patients, overall response rate (per RECIST and irRC) was 15%: 2 partial responses. Another 8 patients achieved stable disease. Pseudoprogression was observed in 1 patient after the second cycle of treatment. To date, both progression-free survival and overall survival range from 8 to 21 weeks. The safety of trabectedin and nivolumab was acceptable. Grade 3 adverse events included anemia, fatigue, thrombocytopenia, and increased creatinine kinase. To date, no immune-related adverse events have been observed. Tseng WW, et al. CTOS 2016. Abstract 2555232. P2 Poster 128.