Evaluation of the clinical molecule anti-human-PD-L1/IL-15 KD033 in the human-PD-1/PD-L1-expressing murine model demonstrates PD-L1 targeting of IL-15 in vivo.

KD033 is a clinical-stage immunocytokine composed of a high-affinity anti-human-PD-L1 antibody and the human IL-15/ IL-15 receptor sushi-domain complex. We have previously shown that KD033-surrogate, the anti-mouse-PD-L1/IL-15 immunocytokine, was efficacious in several syngeneic murine tumor models including those that were refractory to anti-PD-1/PD-L1 checkpoint blockers. KD033-surrogate showed better efficacy than the combination treatment of its component, anti-PD-L1 antibody with the non-targeting IL-15. KD033-surrogate was also efficacious in both low and high PD-L1-expressing tumors. In this study, we have utilized double knock-in mice expressing functional human PD-1/PD-L1 to show that the clinical molecule, KD033, reproduced the anti-tumor efficacy observed with KD033-surrogate in the syngeneic models. KD033 was equally efficacious in reducing the growth of human-PD-L1 positive (hPDL1+) and negative (hPDL1-) MC38 murine tumors. We observed similar peripheral pharmacodynamics changes in KD033-treated mice bearing either hPDL1+ or hPDL1- MC38 tumors. However, different transcriptomic profiles were observed between KD033-treated hPDL1+ and hPDL1- MC38 tumors with marked changes involving mostly downregulated genes in hPDL1- tumors in addition to the immune-related genes changes observed in both hPDL1+ and hPDL1- MC38 tumors. Cytotoxic and myeloid cell signatures were upregulated in both tumors with relatively greater increases observed in hPDL1- MC38 tumors. These effects of KD033 treatment in PD-L1 positive and negative tumors demonstrate the role of PD-L1 in targeting of IL-15 cytokine in vivo.