Physiologically Motivated Sequential Population Modeling of Albumin Trends and Vedolizumab Pharmacokinetics for Pregnancy Dosing Regimen Optimization

The pharmacokinetics (PK) of monoclonal antibodies (mAbs) during pregnancy remains poorly characterized, despite active inflammatory bowel diseases (IBD) being the greatest risk factor for adverse pregnancy outcomes. To quantify pregnancy-induced changes, vedolizumab concentrations from 39 pregnant patients on various dosing regimens were analyzed using a sequential albumin-trend/PK modeling approach, extending a published vedolizumab non-pregnancy model. Albumin trends were first characterized using a polynomial mixed-effect model. Then, individual changes in albumin from their pre-pregnancy concentrations, implemented as time-varying patient-influential factor (covariate) in the PK model, served as potential biomarker of pregnancy-induced plasma volume expansion. The modeling framework allowed model-informed imputation of missing covariate data, extraction of hemodilution effect, and estimation of pre-pregnancy PK parameters. Due to albumin change, the central volume of distribution increased 52.4%, consistent with known gestational plasma volume expansion, while clearance increased to 38.6%. An additional third-trimester effect of gestational age, potentially reflecting transplacental transfer, increased clearance by an additional 33.3 percentage points. These changes led to a 49.5% decline in vedolizumab trough concentrations (Cmin) by late pregnancy. To maintain efficacious pre-pregnancy exposure (dependent on the individual dosing interval), dosing intervals were gradually shortened for approximately one-third (e.g., to up to 5.6 weeks for pre-pregnancy 8-week regimens). Optimized dosing times were summarized in an easy-to-use nomogram-like plot. This work provides the first population PK model of vedolizumab in pregnancy. By integrating physiologically motivated pregnancy effects, it advanced quantitative understanding of mAbs PK in pregnancy with potential application to other biologics and provides optimized dosing strategies to mitigate risks of adverse pregnancy outcomes.