The arming of NK cells with Fc-engineered rituximab confers them specificity against CD20-expressing cells

Clinical effects of IgG1 monoclonal antibodies (mAb) relies on various mechanisms, including antibody dependent cell-mediated cytotoxicity (ADCC), which requires natural killer (NK) cells as the main immune effectors. These cells are emerging as significant tools for cancer cell therapies, presenting a potential alternative to Chimeric Antigen Receptor-T (CAR-T) cell therapies. We generated in vitro expanded NK cells (eNK) and investigated the feasibility of loading them with a Fc-modified rituximab (RTX) displaying high affinity for CD16a. We demonstrated that the Fc modified RTX (SDH-RTX: S239D/H268F/S324T/I332E) can be effectively loaded onto eNK cells, resulting in what we termed “armed eNK”. The SDH-RTX-armed eNK retained SDH-RTX in the presence of physiological concentrations of IgG1 and exhibited specific cytotoxic activity against CD20-positive cells, including cell lines and samples from NHL and B-CLL patients. Remarkably, armed eNK cells demonstrated comparable ADCC to eNK cells in the presence of an excess of RTX. Importantly, arming eNK cells did not compromise their natural cytotoxicity against other target cells. These findings pave the way to innovative approaches utilizing armed eNK as a form of “non-genetically modified CAR-like” NK cells to treat diseases susceptible to mAb targeting. This approach offers the advantages of reduced mAb requirement and versatile specificity.