CTLA4 and round cell liposarcoma: In a randomized, double-blind phase study (SARC028), pembrolizumab suggested a potential benefit for undifferentiated pleomorphic sarcoma with a response rate of 40% while having little clinical effect in synovial sarcoma and myxoid/round cell liposarcoma due to many factors, including PD-L1 expression, tumour mutation burden, T-cell infiltration, etc. CTLA-4 is a key protein during the priming phase of the immune system, and its inhibition is thought to increase T cells in circulation and deplete Tregs.