Virtual twins for model‐informed precision dosing of clozapine in patients with treatment‐resistant schizophrenia

Abstract Model‐informed precision dosing using virtual twins (MIPD‐VTs) is an emerging strategy to predict target drug concentrations in clinical practice. Using a high virtualization MIPD‐VT approach (Simcyp version 21), we predicted the steady‐state clozapine concentration and clozapine dosage range to achieve a target concentration of 350 to 600 ng/mL in hospitalized patients with treatment‐resistant schizophrenia (N = 11). We confirmed that high virtualization MIPD‐VT can reasonably predict clozapine concentrations in individual patients with a coefficient of determination (R2) ranging between 0.29 and 0.60. Importantly, our approach predicted the final dosage range to achieve the desired target clozapine concentrations in 73% of patients. In two thirds of patients treated with fluvoxamine augmentation, steady‐state clozapine concentrations were overpredicted two to four‐fold. This work supports the application of a high virtualization MIPD‐VT approach to inform the titration of clozapine doses in clinical practice. However, refinement is required to improve the prediction of pharmacokinetic drug–drug interactions, particularly with fluvoxamine augmentation.