AbstractTildrakizumab, a high‐affinity humanized IgG1k antibody that selectively binds interleukin (IL)‐23 p19 subunit of cytokine IL‐23 and neutralizes its function, is under investigation for treatment of moderate‐to‐severe chronic plaque psoriasis. The objective of this analysis was to assess the pharmacokinetics, bioavailability and safety/tolerability of single ascending doses of tildrakizumab after intravenous (IV) and subcutaneous (SC) dosing in healthy subjects. P05661 was a phase 1, single‐dose, randomized, placebo‐controlled study of tildrakizumab IV doses of 0.1, 0.5, 3 and 10 mg/kg, or placebo. P05776 was a phase 1, single‐dose, randomized, placebo‐controlled study of tildrakizumab SC doses of 50 or 200 mg, or placebo. After either single IV or SC dosing, tildrakizumab exhibited slow systemic clearance (CL), limited volume of distribution and a long t1/2. Both the Cmax and the area under the curve (AUC) increased proportionally with doses from 0.1 to 10 mg/kg, or 50–200 mg. The bioavailability of SC dosing was ~80% (90% CI: 62–103%) for 50 mg and ~73% (90% CI: 46–115%) for 200 mg, respectively, versus 0.5 and 3 mg/kg IV. Across both studies, six of 43 evaluable subjects were positive for post‐dose antidrug antibodies; two of these were positive for neutralizing antibodies. Most adverse events (AEs) were mild; the most frequent AEs included upper respiratory tract infection and headache. Single doses of tildrakizumab 0.1, 0.5, 3 and 10 mg/kg administered IV or single doses of 50 and 200 mg administered SC were safe and well tolerated in healthy adult subjects.