Background: IL-2 and IL-15 signal through the shared IL-2/15 βγ receptor, but unlike IL-2, IL-15 does not expand regulatory T cells (Tregs). In addition, unlike IL-2, IL-15 does not mediate activation-induced cell death and is expected to have an improved therapeutic index compared to IL-2. KD033 is a fusion antibody molecule generated by combining a fully human, high affinity anti-human Programmed Death Ligand 1 (PD-L1) IgG1 antibody with the human IL-15 receptor alpha (IL15Rα) sushi domain and human IL-15 (IL-15). KD033 (or its mouse cross reactive surrogate molecule, srKD033) has been extensively characterized in multiple in vitro and in vivo nonclinical studies to understand the pharmacology, pharmacokinetic (PK) and toxicology properties. The fusion of anti-PD-L1 antibody to IL-15 significantly increases the maximal-tolerated dose (MTD) of srKD033 in mice compared to free-IL-15. The increased safety and efficacy of PD-L1-targeted IL-15 observed in pre-clinical studies warranted evaluation of KD033 in humans. Methods: This is a phase 1, open-label, multiple ascending dose, multi-center clinical trial being conducted in patients with metastatic or locally advanced solid tumors (NCT04242147). The primary objective is to determine the safety and tolerability and the MTD of KD033. KD033 is administered as an IV infusion over 30 minutes every 14 days (i.e., a cycle equals 2 weeks). The starting dose of KD033 is 3 µg/kg, with step-up dosing to 12.5 µg/kg in the first cohort of 3 subjects. After the first cohort, the dose escalation will use a standard 3+3 design with planned doses from 25 µg/kg to 600 µg/kg. The dose escalation phase will be followed by one expansion cohort, which will enroll patients who received PD-1/PD-L1 inhibitor but have either progressed or are refractory to therapy. Secondary objectives include characterization of PK and immunogenicity, evaluation of immune correlates that will potentially differentiate the impact of KD033 versus monotherapy as well as investigate IL-15 biology and determine best overall response and duration of response. (NCT04242147)

Citation Format: Jason J. Luke, Anthony J. Olszanski, Igor Puzanov, Dan Lu, Adrian Hackett, Stella Martomo, Jeegar Patel, Olivier Schueller, Alessandro Mora, Miranda L. Schlitt, Linghui Li. A phase 1 multiple ascending dose study to investigate the safety, pharmacokinetics, pharmacodynamics and preliminary efficacy of KD033 in subjects with metastatic or locally advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT227.