Purpose: The effectiveness of NK cell infusions to induce leukemic remission is limited by lack of both antigen specificity and in vivo expansion. To address the first issue, we previously generated a bispecific killer engager (BiKE) containing singlechain scFv against CD16 and CD33 to create an immunologic synapse between NK cells and CD33+ myeloid targets. We have now incorporated a novel modified human IL15 crosslinker, producing a 161533 trispecific killer engager (TriKE) to induce expansion, priming, and survival, which we hypothesize will enhance clinical efficacy. Experimental Design: Reagents were tested in proliferation and functional assays and in an in vivo xenograft model of AML. Results: When compared with the 1633 BiKE, the 161533 TriKE induced superior NK cell cytotoxicity, degranulation, and cytokine production against CD33+ HL-60 targets and increased NK survival and proliferation. Specificity was shown by the ability of a 1615EpCAM TriKE to kill CD33-EpCAM+ targets. Using NK cells from patients after allogeneic stem cell transplantation when NK cell function is defective, the 161533 TriKE restored potent NK function against primary AML targets and induced specific NK cell proliferation. These results were confirmed in an immunodeficient mouse HL-60-Luc tumor model where the 161533 TriKE exhibited superior antitumor activity and induced in vivo persistence and survival of human NK cells for at least 3 weeks. Conclusions: Off-the-shelf 161533 TriKE imparts antigen specificity and promotes in vivo persistence, activation, and survival of NK cells. These qualities are ideal for NK cell therapy of myeloid malignancies or targeting antigens of solid tumors.
Bibliographical noteFunding Information:
This work was supported in part by the U.S. Public Health Service Grant R01-CA36725, R01-CA72669, P01-CA65493, P01-CA111412, and R35 CA197292 awarded by the NCI and the NIAID, DHHS. It was also supported by an NIH Research Evaluation and Commercialization Hub (REACH) Award (U01), the Mayo Partnership Award, the Lion Fund, William Lawrence and Blanche Hughes Fund, the Randy Shaver Foundation, the Atwater Cancer Drug Development Award, the Deutsche Krebshilfe (DS), and a CETI translational award from the University of Minnesota Masonic Cancer Center. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.