A recombinant, humanized fusion protein consisting of a cytotoxic T-lymphocyte-associated antigen 4 (CTLA4; CTLA-4) single domain antibody linked to a Fc domain, with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti-CTLA4 antibody Fc fusion protein KN044 targets and binds to CTLA4 expressed on T-cells and inhibits the CTLA4-mediated downregulation of T-cell activation. This leads to a cytotoxic T-lymphocyte (CTL)-mediated immune response against cancer cells. CTLA4, an inhibitory receptor and member of the immunoglobulin superfamily (IgSF), plays a key role in the downregulation of the immune system.