NK cells play a major role in the anti-tumor efficacy of certain tumor-antigen targeting antibodies. NK cells express CD16, an activating receptor that binds to the Fc portion of IgG antibodies. Once activated through CD16, NK cells are able to destroy antibody-coated target cells and secrete cytokines, such as interferon gamma, to recruit and potentiate adaptive immune cells, including T cells. This mechanism of action, referred to as antibody-dependent cellular cytotoxicity (ADCC), is believed to be important for the treatment of a wide range of human tumor types.
ADCC is dependent on NK cells maintaining stable and effective expression of CD16, which has been shown to undergo considerable down-regulation in cancer patients. In addition, CD16 occurs in two variants, 158V or 158F, that elicit high or low binding affinity, respectively, to the Fc domain of IgG1 antibodies. Numerous clinical studies with FDA-approved tumor-targeting antibodies, including rituximab, trastuzumab and cetuximab, have demonstrated that patients homozygous for the 158V variant, which is present in only about 15% of patients, have improved clinical outcomes.
FT516 is an investigational, universal, off-the-shelf natural killer (NK) cell cancer immunotherapy derived from a clonal master iPSC line engineered to express a novel high-affinity 158V, non-cleavable CD16 (hnCD16) Fc receptor, which has been modified to prevent its down-regulation and to enhance its binding to tumor-targeting antibodies. FT516 is being investigated in an open-label, multi-dose Phase 1 clinical trial as a monotherapy for the treatment of acute myeloid leukemia and in combination with CD20-directed monoclonal antibodies for the treatment of advanced B-cell lymphoma (NCT04023071). Additionally, the FDA has allowed investigation of FT516 in an open-label, multi-dose Phase 1 clinical trial in combination with monoclonal antibody therapy, including PDL1-, PD1-, EGFR- and HER2-targeting therapeutic antibodies, across a broad range of solid tumors.
Engineered high-Affinity non-Cleavable CD16 Fc Receptor