e18637 Background: Pegfilgrastim-cbqv, a pegfilgrastim biosimilar, is administered 24-72 h after myelosuppressive chemotherapy to prevent febrile neutropenia. Pegfilgrastim delivery via an on-body injector (OBI) applied on the day of chemotherapy eliminates the need for a second healthcare visit. This study evaluated the pharmacokinetic (PK), pharmacodynamic (PD) bioequivalence (BE), and the safety of pegfilgrastim-cbqv administered via OBI vs prefilled syringe. Methods: In this open-label, 2-period crossover study, healthy adult male participants were randomized 1:1 to 2 treatment sequences to receive a 6-mg subcutaneous (SC) injection of pegfilgrastim-cbqv via OBI or prefilled syringe in period 1 and an injection via the other method in period 2 (after a 6- to 8-wk washout). Primary endpoints (PK) were area under the concentration-time curve from time 0 to infinity (AUC0-inf), the AUC from time 0 to the last quantifiable concentration (AUC0-last), and the maximum plasma concentration (Cmax). Secondary endpoints (PD) were area under the absolute neutrophil count (ANC)-time curve from time 0 to the last quantifiable ANC (ANC AUC0-last) and maximum ANC (ANCmax). PK/PD BE was established if the 90% CI for the geometric mean ratios (GMRs) fell within 80-125%. Safety and immunogenicity were also assessed. Results: The 90% CIs of the GMRs for PK and PD endpoints in healthy participants fell within the predetermined range (Table). Treatment-emergent adverse events (TEAEs) occurred in 87.8% (OBI) vs 75.8% (prefilled syringe) of participants. Most TEAEs were musculoskeletal effects and mild in severity. The most common injection siterelated TEAE was erythema (OBI 34.1%; prefilled syringe 2.5%). The injection site erythema reactions were mild in severity and self-limiting. The incidence of treatment-emergent antidrug antibodies (ADAs) in period 1 was similar with OBI (40.0%) vs prefilled syringe (36.6%); ADA titers were low, transient, and primarily directed to the polyethylene glycol (PEG) moiety of pegfilgrastim-cbqv. The ADAs had no apparent impact on PK, PD, or safety. Neutralizing antibodies were not detected in any participant. Conclusions: This study demonstrated PK and PD BE of pegfilgrastim-cbqv administered via OBI vs prefilled syringe in healthy adult males. OBI and prefilled syringe administration had similar safety and immunogenicity profiles. No unexpected safety signals were identified.[Table: see text]