Off-the-Shelf Natural Killer Cell Immunotherapy for Enhanced Antibody Directed Cellular Cytotoxicity

Natural Killer (NK) cells play a crucial role in immunosurveillance and form a first line of defense against cancer. In comparison to other lymphocytes, NK cells are unique in their capability to elicit tumoricidal responses without the need for antigen presentation or prior sensitization. Clinical data from bone marrow transplant and allogeneic NK immunotherapy suggest that MHC mismatch is advantageous in promoting graft-versus-leukemia without eliciting graft-versus-host, providing evidence that NK cells hold promisa as an allogeneic, universal immunotherapeutic. Further, the anti-tumor effect of many monoclonal antibodies is mediated through binding of the low-affinity Fc receptor CD16 on NK cells, which induces tumor cell killing through antibody-dependent cellular cytotoxicity (ADCC). Thus, NK cells represent a unique source of effector cells that can be combined with monoclonal antibodies, bispecific engagers or chimeric antigen receptors to direct tumor specificity and enhance cytotoxicity. Despite the significant potential of NK cell therapy, current clinical practices are limited by the need for large numbers of healthy NK cells, lack of in vivo persistence, and a burdensome manufacturing strategy that requires donor cell extraction, modulation, expansion and re-introduction per each patient.

The ability to generate universally histocompatible and genetically-enhanced NK cells from continuously renewable human induced pluripotent stem cell (hiPSC) lines offers the potential to develop a true "off-the-shelf" cellular immunotherapy. While NK differentiation from hiPSC has been demonstrated, the clonal derivation of engineered hiPSCs to improve effector function has been challenging and the scalability and robustness of the differentiation method has been limited by skewed development towards primitive hematopoiesis and the cumbersome use of embryoid bodies.

Here we highlight our "off-the-shelf" NK cell therapy preclinical program by demonstrating robust and highly scalable generation of functionally mature, genetically targeted and universally histocompatible NK cells. This program utilizes our previously described naïve hiPSC platform where we uniquely create clonal lines of precisely engineered, renewable hiPSCs and drive definitive hematopoiesis in a highly scalable manner. Because hiPSC differentiation is lineage directed, minimal cellular contamination is seen, including the lack of T and B cells, in the final product. Through precise genetic engineering of naïve hiPSC lines, we have engineered HLA-class I deficient NK cells uniformly expressing a high affinity, non-cleavable version of the Fc receptor CD16 (NcHaCD16-NK). The hiPSC-derived NcHaCD16-NKs display markers of maturity, including CD16, KIR, NCRs, and CD94. When compared to conventional cord blood and peripheral blood sourced NK cells, NcHaCD16-NKs exhibit superior cytotoxicity and production of effector cytokines in response to both solid and liquid tumor cell challenge in vitro. NcHaCD16-NKs exhibit augmented cytokine response following Fc-mediated stimulation, demonstrating function competence of the engineered CD16 construct. Because surface expression of CD16 is resistant to activation-induced shedding, NcHaCD16-NKs continuously maintain enhanced ADCC while retaining the capacity for general cytotoxicity. Importantly, the hiPSC-derived hematopoietic cells can be successfully cryopreserved and banked, serving as a highly-stable cell bank for subsequent therapeutic use. Preliminary data also shows NcHaCD16-NKs elicit preferred specificity for cancer stem cells as defined by expression of ALDH1 and surface markers such as CD24. In conclusion, the outlined preclinical data demonstrate the potential therapeutic utility of NK cells developed via precision genetic engineering of a renewable, scalable hiPSC platform, and highlights the therapeutic value of NcHaCD16-NKs as an ideal ADCC-mediated "off-the-shelf" NK cell-based immunotherapeutic product with augmented persistence, anti-tumor capacity and preclinical efficacy.