Background: Similarity of the pharmacokinetic (PK)/pharmacodynamic (PD) profiles of Sandoz proposed biosimilar pegfilgrastim and EU-reference biologic was confirmed in a pivotal Phase I study. In order to confirm PK/PD similarity to the US reference biologic, and to bridge between the two references, a 3-way study was conducted. Methods: A randomized, double-blind, single-dose, 3-treatment, 6-sequence crossover Phase I study was performed in healthy volunteers (HVs) to demonstrate similarity in PK, PD, safety and immunogenicity between Sandoz proposed biosimilar, US reference, and EU reference pegfilgrastim administered subcutaneously (6 mg/0.6 mL) in each treatment period. The primary objective was to demonstrate PK (AUC_0-inf, AUC_0-last, C_max) and PD similarity (ANC AUEC_0-last, ANC E_max). The study was powered (90%) to achieve confidence intervals (CIs) within biosimilarity margins 0.8─1.25 in pairwise comparisons. Secondary objectives were additional PK/PD parameters, safety and immunogenicity. Results: The study included 577 male and female HVs. PK and PD similarity were demonstrated between Sandoz proposed biosimilar and US reference (Table), as well as EU reference and between both reference biologics since the 90% CIs of the geometric mean ratios were contained within the pre-defined margins of 0.80‒1.25. Safety, immunogenicity and secondary PK/PD parameters were also similar across treatment groups. Conclusions: This large randomized, double-blind, single-dose, 3-treatment, 6-sequence crossover study demonstrated PK and PD similarity between Sandoz proposed biosimilar, US reference and EU reference pegfilgrastim with similar safety, local tolerability and immunogenicity. Clinical trial information: 2016-003549-27.