Population Pharmacokinetic Analysis and Simulation of Alternative Dosing Regimens for Biosimilars to Adalimumab and Etanercept in Patients with Rheumatoid Arthritis

\ua9 2024 by the authors.Efficacy to biologics in rheumatoid arthritis (RA) patients is variable and is likely influenced by each patient’s circulating drug levels. Using modelling and simulation, the aim of this study was to investigate whether adalimumab and etanercept biosimilar dosing intervals can be altered to achieve therapeutic drug levels at a faster/similar time compared to the recommended interval. RA patients starting subcutaneous Amgevita or Benepali (adalimumab and etanercept biosimilars, respectively) were recruited and underwent sparse serum sampling for drug concentrations. Drug levels were measured using commercially available kits. Pharmacokinetic data were analysed using a population approach (popPK) and potential covariates were investigated in models. Models were compared using goodness-of-fit criteria. Final models were selected and used to simulate alternative dosing intervals. Ten RA patients starting the adalimumab biosimilar and six patients starting the etanercept biosimilar were recruited. One-compartment PK models were used to describe the popPK models for both drugs; no significant covariates were found. Typical individual parameter estimates were used to simulate altered dosing intervals for both drugs. A simulation of dosing the etanercept biosimilar at a lower rate of every 10 days reached steady-state concentrations earlier than the usual dosing rate of every 7 days. Simulations of altered dosing intervals could form the basis for future personalised dosing studies, potentially saving costs whilst increasing efficacy

Comparative Effectiveness of Abatacept Versus Adalimumab in Shared Epitope Positive and Negative Patients With Rheumatoid Arthritis

\ua9 2025 The Author(s). Arthritis & Rheumatology published by Wiley Periodicals LLC on behalf of American College of Rheumatology. Objective: The effect of the shared epitope (SE) and valine at position 11 (Val11) of HLA–DRB1 on the activation of CD4+ T cells is expected to be diminished by abatacept, a costimulation blocker. However, published evidence on the value of genetic stratification for abatacept treatment is conflicting. We aimed to compare the difference in effectiveness of abatacept and adalimumab in patients carrying the SE (or Val11). Methods: The Biologics in Rheumatoid Arthritis Genetics and Genomics Study Syndicate is a nationwide observational cohort study recruiting patients from 53 centers across the United Kingdom before the initiation of biologic treatment and following them up prospectively for 12 months. Three hundred forty-two patients starting either abatacept or adalimumab were eligible for this analysis. Serum drug levels for abatacept, adalimumab, and methotrexate were determined at multiple time points. Multivariate modeling integrating demographic, clinical, and pharmacological variables was used to test for associations between the number of copies of the SE or Val11 and response to treatment (EULAR response; Disease Activity Score in 28 joints [DAS28] remission; change in DAS28). Differential effectiveness between drugs and genetic markers was assessed by the significance of their interaction term. Results: There was no difference in the efficacy of abatacept versus adalimumab. We found weak evidence for an independent association of genetic markers with response to treatment (Val11 with EULAR response: P = 0.02), but there was no significant difference in this effect between drugs. Conclusion: We found no evidence that HLA typing is clinically useful to support prescription decisions for these two drugs. (Figure presented.)