A monoclonal antibody directed against C-C-chemokine receptor 8 (CCR8), with potential immunomodulating and antineoplastic activities. Upon administration, anti-CCR8 monoclonal antibody BGB-A3055 targets and binds to CCR8 on CCR8-positive tumor-infiltrating regulatory T-cells (Tregs) in the tumor microenvironment (TME) and prevents chemokine ligand 1 (CCL1)-CCR8-mediated signaling. This may reactivate antitumor immune responses. CCR8 is specifically expressed by tumor-infiltrating Tregs in multiple types of cancer and plays a key role in immunosuppression. High expression is correlated with poor prognosis.