A human Fc fusion protein composed of the cytokine interleukin (IL)-15 cross-linked with the high-affinity binding sushi domain of IL-15 receptor alpha (IL-15Ra), with potential antineoplastic activity. Upon administration, SHR-1501 activates and increases the levels of natural killer (NK) cells and memory CD8+ T-cells without stimulating regulatory T-cells (Tregs). The memory T-cells enhance the secretion of the cytokine interferon-gamma (IFN-g), which further potentiates the immune response against tumor cells. This may increase tumor cell killing and decrease tumor cell proliferation. IL-15 regulates CD8+ T and NK cell development, activation and proliferation. SHR1501 is more potent than unmodified IL-15 and does not require endogenous IL-15Ra for its action. The Fc moiety allows for an extended half-life of SHR-1501 while cross linking IL-15 with IL-15Ra sushi domain improves stability.