Population PK Modeling of Denosumab Biosimilar MB09 and Reference Denosumab to Establish PK Similarity

<b>Background/Objectives</b>: MB09 is a denosumab biosimilar to the reference products (RPs) Xgeva and Prolia. A population pharmacokinetic (popPK) meta-analysis was conducted to characterize the denosumab PK profile and to support MB09 biosimilarity. <b>Methods</b>: Pooled denosumab PK data from one phase I study [255 healthy adult men receiving a single 35 mg subcutaneous (SC) dose] and one phase III study (555 postmenopausal women with osteoporosis receiving two 60 mg SC doses, one every six months) were used. A one-compartment model with first-order absorption and elimination and parallel non-linear saturable clearance was used. Body weight was included on clearance as a structural covariate and treatment was tested as a covariate on all PK parameters. PK biosimilarity was assessed at 35 mg dose. <b>Results</b>: For a 70 kg subject, the apparent clearance and central volume of distribution for denosumab were 0.123 L/day [95% confidence interval (CI): 0.114, 0.132] and 9.33 L (95% CI: 9.11, 9.55), respectively. The Michaelis constant was 0.124 ng/mL and the maximum rate for the non-linear clearance was 0.139 ng/day. Model-based bioequivalence criteria were met for RP Xgeva, European and US-sourced, versus MB09 for a dose of 60 mg SC. The mean area under the plasma concentration curve (AUC) resultant from the simulation of MB09 120 mg SC was similar to the published mean AUC observed for Xgeva 120 mg SC every four weeks. <b>Conclusions</b>: This analysis provides a valuable assessment of denosumab PK characteristics and elucidates in more detail how the MB09 PK profile compares to the denosumab RPs, supporting the totality of evidence on MB09 biosimilarity.