CXCR2 antagonist 3 (compound 11h) is a highly effective antagonist of CXC chemokine receptor 2 (CXCR2). It displays potent activity in inhibiting neutrophil infiltration into the air pouch, with double-digit nanomolar potencies against CXCR2. Moreover, CXCR2 antagonist 3 reduces the infiltration of neutrophils and MDSCs, while enhancing the infiltration of CD3+ T lymphocytes into Pan02 tumor tissues [1].