Introduction: Etrolizumab is a novel, dualaction anti-b7 integrin antibody studied in phase 3 trials in patients with inflammatory bowel disease. An autoinjector (AI) is being developed in parallel to complement the prefilled syringe with needle safety device (PFS-NSD) for subcutaneous (SC) administration in these trials.Here we demonstrate the comparable pharmacokinetics, tolerability, and safety of both devices. Methods: This randomized, open-label, twopart study in healthy participants evaluated the comparability of etrolizumab exposure between the AI and the PFS-NSD. Part 1 (pilot) involved a small number of participants, and initial results were used to finalize the design of the larger part 2 (pivotal) study. In both parts, participants were randomly assigned to receive a single SC dose of etrolizumab 105 mg by AI or PFS-NSD. Randomization was stratified by body weight. Primary pharmacokinetic outcomes were C max , AUC last , and AUC 0-inf .Results: One hundred and eighty healthy participants (part 1, n = 30; part 2, n = 150) received a single SC dose of etrolizumab by AI or PFS-NSD. Primary pharmacokinetic results from part 1 supported modification of the part 2 study design. Results from part 2 demonstrated that etrolizumab exposure was equivalent between devices, with geometric mean ratios (GMRs) between AI and PFS-NSD of 102% (90% confidence interval [CI] 94.2-111) for C max , 98.0% (90% CI 89.3-107) for AUC last , and 97.6% (90% CI 88.6-107) for AUC 0-inf . Median t max and mean terminal t 1/2 were also similar between devices. GMRs and 90% CIs of all primary pharmacokinetic parameters were fully contained within the predefined equivalence limits (80-125%). Conclusion: This pharmacokinetic study demonstrated that single SC injections of etrolizumab 105 mg using an AI or a PFS-NSD resulted in equivalent etrolizumab exposure and similar safety and tolerability in healthy participants. Taken together, these results support the use of an AI for etrolizumab administration. Trial Registration: NCT02996019.

Introduction: Etrolizumab is a novel, dual-action, anti-b7 integrin antibody in development for patients with moderate to severe ulcerative colitis or Crohn's disease. Phase 3 studies use a prefilled syringe (PFS) for etrolizumab administration. In parallel, an autoinjector (AI) is being developed to increase delivery options for patients if etrolizumab is approved. Here we describe the overall development strategy and detail the first-in-human study of this AI.Methods: This open-label study of healthy volunteers evaluated the tolerability and usability of the etrolizumab AI under development. The primary endpoint was the proportion of participants with greater than mild pain following injection. Adverse events (AEs) and usage errors were also assessed. Results were reported by injection site (thigh vs abdomen) and needle H. Tyrrell (&) Á J.