The development of a next generation NK cell engager platform by integrating a potency-reduced IL-15 variant to enhance antitumor activity.

BACKGROUND: Natural killer cell engager (NKCE) has gained attention recently. Conventional NKCEs exhibit mild anti-tumor efficacy despite acceptable safety profiles. Therefore, next-generation NKCE development is essential to enhance efficacy. IL-15, a key NK cell activator, is explored in NKCE design. However, wild-type IL-15 shows significant toxicity in clinical trials. In this study, we present the development of a novel tetravalent NKCE platform (IL15v-NKCE) by incorporating a potency-reduced IL-15 element (IL15v) into our proprietary anti-NKp46 based NKCEs. METHODS: The activity of the IL15v moiety was assessed by quantifying pSTAT5 induction in primary immune cells and evaluating STAT5 activation in an IL-15 reporter cell line. The in vitro activity of IL15v-NKCE was determined using co-culture assays with NK and tumor cells. The in vivo anti-tumor efficacy and safety profile of IL15v-NKCE were evaluated in tumor-bearing mouse models. RESULTS: In vitro, IL15v selectively activates NK cells without affecting T cells, enhances NKCE cytotoxicity, prevents NK apoptosis, and promotes NK proliferation. In vivo, IL15v-NKCE shows good tolerability and superior anti-tumor efficacy compared to conventional NKCE. All four components (anti-NKp46, Fc, IL15v, anti-tumor-associated antigen) of IL15v-NKCE are essential for maximal activity, and IL15v-NKCE is more potent than the conventional NKCE when combined with anti-PD-1 in preclinical models. CONCLUSIONS: By integrating IL15v into our anti-NKp46 based NKCEs, IL15v-NKCE has exhibited enhanced anti-tumor efficacy while maintaining an acceptable safety profile, thereby positioning it as a promising next-generation therapeutic modality for NK cell-based therapy.