IPH6501 Is a Novel NKp46-Targeting Tetraspecific Antibody-Based Natural Killer Cell Engager Therapeutic (ANKET) Armed with a Non-Alpha IL-2 Variant and Developed for the Treatment of CD20-Positive Malignancies

Abstract

CD20 is expressed by >90% of B-cell non-Hodgkin's lymphomas (NHL). Several generations of CD20-targeting monoclonal antibodies including rituximab, ofatumumab, and obinutuzumab have been widely used for B-cell malignancy therapies. Despite the recent approvals of novel CD20-targeting agents, new alternatives and strategies are still required for patients, which are relapsing or refractory after several lines of treatment. High circulating NK cell numbers have been associated with better clinical responses to anti-CD20- targeting monoclonal antibodies, supporting the role of NK cells in efficacy of these treatments. IPH6501, a novel antibody-based NK cell engager therapeutics (ANKET), is a single tetraspecific molecule engaging two NK cell activating receptors NKp46 and CD16a (FcγRIIIa), the β chain (CD122) of the interleukin-2 receptor (IL-2R), and the CD20 antigen expressed on malignant B cells. The IL-2R binding element incorporated in IPH6501 is an IL-2 variant (IL-2v) designed with point mutations that abolish binding to the IL-2R-α chain (CD25), with the goal of limiting toxicity and interaction with Tregs. IL-2v incorporated into IPH6501 is directed towards NK cells through the binding with high affinity to NKp46 and CD16a, providing its ability to interact with IL-2R preferentially on NK cells and to promote their activation and proliferation at pM doses. IPH6501 was designed to induce NK cell mediated-cytotoxicity and cytokine secretion by co-engaging CD16a and NKp46. Only the binding of IPH6501 to CD20, bridging the NK cells to the target cells, was able to trigger the cytotoxic activity of NK cells. Non-saturating doses of IPH6501 on NK cells and on CD20+ cells were sufficient to promote maximal killing activity. Furthermore, IPH6501 promoted NK cell cytotoxicity against tumor cells expressing very low levels of CD20. IPH6501 also demonstrated superiority to control tumor cell growth in vitro, as compared to the CD20-targeting clinical benchmark antibodies rituximab and the Fc-optimized obinutuzumab. In vivo treatment with a mouse surrogate of IPH6501 induced peripheral NK cell proliferation and activation, and demonstrated potent antitumor efficacy in a xenograft mouse model using the aggressive human B-lymphoma CD20+ RAJI cell line engrafted subcutaneously. In non-human primate, a well-tolerated dose of IPH6501 led to peripheral NK cell expansion and to the depletion of CD20+ B cells in the circulation and within lymphoid tissues, with minimal systemic cytokine release. In conclusion, IPH6501 is a first-in-class CD20-targeting tetraspecific NK cell engager designed to promote NK cell proliferation and specific cytotoxicity against CD20+ cells. IPH6501 is thus a promising biologic designed to harness the anti-tumor functions of NK cells in CD20+ B cell malignancies. IND-enabling studies are ongoing, and IPH6501 is expected to enter FIH clinical study in 2023.