CTLA4 and undifferentiated pleomorphic sarcoma: Then, Alliance A091401 study (NCT02500797) assessed the efficacy of nivolumab (a PD-1 inhibitor) alone or in combination with ipilimumab (a CTLA4 inhibitor) in advanced sarcomas where the combination regimen was found to be more efficacious in leiomyosarcoma, UPS, myxofibrosarcoma, angiosarcoma, alveolar soft part sarcoma and malignant fibrous histiocytoma.