Inbakicept (ALT 803) is a fusion protein of the IL-15 receptor α-sushi binding domain IL-15RαSu and immunoglobulin G1 (human Fc fragment), which is an IL-15 superagonist protein complex. Inbakicept has potential anticancer and antitumor activities and can be used to study breast cancer.

b>METHODS: Human NK cells were treated with inbakicept (ALT-803) (0.01-1 nM; 20 hours) to study its effects on the cytotoxicity of the MHC class I low, NK cell-sensitive target K562. Effector cells were washed and the effects of short-term stimulation with ALT-803 on key effector proteins mediating NK cell killing were studied.
RESULTS: Inbakicept enhanced human NK cell killing in a dose-dependent manner; in addition, inbakicept (ALT-803) induced a dose-dependent increase in the expression of perforin and granzyme B in CD56dim human NK cells. [1]

b>METHODS: SCID mice were treated with inbakicept (ALT-803) (0.2 mg/kg; intravenous injection; twice a week for 2 weeks) alone or in combination with rituximab to examine the effect of inbakicept administration on the in vivo elimination of human lymphoma cells by mouse NK cell anti-CD20-mAb.
RESULTS: The survival rate of SCID mice treated with inbakicept combined with rituximab was significantly improved, indicating that it can enhance the protective effect of rituximab against lethal Daudi lymphoma challenge. [1]