A guanosine derivative and an agonist of TLR7; selective for TLR7 over other human TLRs in a cell-based reporter assay at 1 mM; induces proliferation, increases the antibody response to sheep red blood cells, and activates natural killer cell activity against Yac-1 lymphoma cells in murine splenocyte cultures (EC50s = 10-50, 3-20, and 13-22 μM, respectively); increases production of IL-12, IL-23, IL-27, and IL-10 by human MoDCs at 250 μM; loxoribine-treated MoDCs induce higher levels of IL-17 and IFN-γ secretion by co-cultured allogeneic CD4+ T cells compared to control MoDCs; reduces the number of pulmonary metastases in the B16 mouse model of melanoma at 120 mg/kg, an effect enhanced by co-administration of IL-2; exhibits adjuvant activity in mice immunized with a B16 tumor vaccine