Phase I Trial Characterizing the Pharmacokinetic Profile of N-803, a Chimeric IL-15 Superagonist, in Healthy Volunteers

The oncotherapeutic promise of IL-15, a potent immunostimulant, is limited by a short serum t(1/2). The fusion protein N-803 is a chimeric IL-15 superagonist that has a >20-fold longer in vivo t(1/2) versus IL-15. This phase 1 study characterized the pharmacokinetic (PK) profile and safety of N-803 after s.c. administration to healthy human volunteers. Volunteers received two doses of N-803, and after each dose, PK and safety were assessed for 9 d. The primary endpoint was the N-803 PK profile, the secondary endpoint was safety, and immune cell levels and immunogenicity were measures of interest. Serum N-803 concentrations peaked 4 h after administration and declined with a t(1/2) of similar to 20 h. N-803 did not cause treatment-emergent serious adverse events (AEs) or grade >= 3 AEs. Injection site reactions, chills, and pyrexia were the most common AEs. Administration of N-803 was well tolerated and accompanied by proliferation of NK cells and CD8(+) T cells and sustained increases in the number of NK cells. Our results suggest that N-803 administration can potentiate antitumor immunity.