NKG2C+ Adaptive NK Cells For AML

We have established that allogeneic natural killer (NK) cell infusions have an anti-leukemic effect and induce remission in 25-40% of patients with relapsed/refractory acute myelogenous leukemia (AML). Limitations include effector cell persistence, activation, and specificity. Here, we will test novel approaches that address these limitations. Our overarching hypothesis is that NKG2C+ adaptive NK cells given in a setting of “missing self” will overcome suppressive mechanisms and mediate potent anti-AML activity and that targeting these cells with immune engagers containing IL-15 will enhance their specificity to kill AML. Our group and others have explored a population of cytomegalovirus (CMV)-induced adaptive NK cells expressing NKG2C and defined by a unique methylation signature that is associated with superior inflammatory cytokine responses and antibody-dependent cellular cytotoxicity (ADCC). These cells are also more resistant to regulatory T cells and myeloid-derived suppressor cells. We completed a 1st generation trial to enrich for adaptive NK cells, but the frequency of NKG2C+ NK cells in the final product averaged 80% NKG2C+ cells using HLA-E+ K562 feeders. In the current funding, we also conducted first-in-human testing of IL-15 treatments. We developed our own IL-15-containing Tri-specific Killer Engager (161533 TriKE) comprised of three functional domains: 1) an NK cell-engaging single chain variable fragment (scFv) against CD16, 2) an AML-engaging scFv against CD33, and 3) an IL-15 linker between them. We predict that the 161533 TriKE will target and activate endogenous NK cells to treat AML/MDS without bystander T cell activation. We produced the 161533 TriKE under GMP conditions, cleared an IND, and started clinical testing. However, NK cells are diminished in many cancers, and we believe that TriKE therapy might ultimately prove most effective when combined with adoptive transfer of adaptive NK cells or other NK cell products. Using adaptive NK cells as a model, we developed an off-the-shelf induced pluripotent stem cell (iPSC)-derived NK cell product that expresses NKG2C/DAP12. When combined with an NKG2C TriKE, these cells become antigen specific. We have developed themes in Project 1 that will inform the Program on whether CMV-induced adaptive NK cells are optimal for cancer therapy, engage unique metabolic programs, can be targeted with TriKEs, are more active in the setting of missing self, and can be mimicked in an off-the-shelf strategy. Our Specific Aims are to 1) test a 2nd generation NKG2C+ adaptive cell product clinically in advanced AML/MDS; 2) test a CD33-targeted, IL-15-containing TriKE in a phase I trial in patients with AML/MDS; and 3) pre-clinically test the combination of the two in xenogeneic models and test whether our iPSC-derived NK cell expressing NKG2C can be targeted with an NKG2C-specific TriKE. Results from these studies will inform Project 2 and 3 on the importance of NKG2C itself, optimization of targeting components within the TriKEs, and the importance of missing self for clinical efficacy.