Pharmacokinetics, Safety and Tolerability of ABT-494, a Novel Selective JAK 1 Inhibitor, in Healthy Volunteers and Subjects with Rheumatoid Arthritis

ABT-494 is a potent and selective Janus kinase (JAK) 1 inhibitor being developed for the treatment of several autoimmune disorders, with potential for an improved safety profile compared with non-selective JAK inhibitors. This work characterized the pharmacokinetics, safety, and tolerability of ABT-494 following single and multiple dosing of the immediate-release formulation. ABT-494 single (1-48 mg or placebo; n = 56) and multiple (3-24 mg or placebo twice daily for 14 days; n = 44) doses in healthy subjects, as well as multiple doses (3-24 mg or placebo twice daily for 27 days; n = 14) in subjects with rheumatoid arthritis (RA) on a background of methotrexate were evaluated. Pharmacokinetic samples were collected and safety and tolerability were assessed. ABT-494 followed bi-exponential disposition, with a terminal elimination half-life of 6-16 h and a functional half-life, calculated from maximum observed plasma concentration (C (max)) to trough plasma concentration (C (trough)) ratio at steady state, of 3-4 h. ABT-494 exposure was approximately dose proportional over the 3-36 mg dose range, with no significant accumulation with repeated dosing. In subjects with RA, no pharmacokinetic interaction between ABT-494 and methotrexate was observed. The fraction of ABT-494 dose eliminated in urine as unchanged ABT-494 was 14-25 %. All treatment-emergent adverse events (TEAEs) were mild or moderate in severity, with headache being the most frequently observed TEAE (15.6 % for ABT-494 vs. 16.7 % for placebo) after multiple twice-daily administration to healthy subjects. No clinically significant changes in laboratory parameters, vital signs, or electrocardiogram findings in healthy or RA subjects were observed. The favorable pharmacokinetics, safety, and tolerability results from these studies supported further evaluations of ABT-494 in phase IIb dose-ranging trials in RA and Crohn's disease.