# Personalizing IL-23 Inhibitor Therapy in IBD: Current Evidence and Future Directions in Therapeutic Drug Monitoring and Dose Optimization

## TL;DR

This paper reviews the current understanding of using IL-23 inhibitors for IBD and explores how drug monitoring and dose adjustments could improve treatment outcomes.

## Contribution

The paper highlights emerging evidence on dose–response relationships and potential thresholds for IL-23 inhibitors, emphasizing the need for further research on therapeutic drug monitoring.

## Key findings

- IL-23 inhibitors like risankizumab show dose–response relationships and potential maintenance thresholds.
- Current evidence on therapeutic drug monitoring for IL-23 inhibitors is limited to small, retrospective studies.
- Routine use of TDM and dose optimization for IL-23 inhibitors remains investigational due to insufficient data.

## Abstract

Interleukin-23 (IL-23) inhibitors have rapidly become an essential component of the therapeutic armamentarium for inflammatory bowel disease (IBD). Risankizumab, mirikizumab, and guselkumab share broadly similar pharmacokinetic and pharmacodynamic properties, including linear clearance, long half-lives, and low immunogenicity. While therapeutic drug monitoring (TDM) is well established in the use of anti-TNF agents, its role in IL-23 inhibitors remains undefined. Emerging evidence, mostly for risankizumab, demonstrates dose–response relationships, suggests potential maintenance thresholds, and outlines possible dose optimization strategies. However, this preliminary data is predominantly retrospective, often single-center, and involves a small number of patients. Until more robust evidence supporting the efficacy of TDM and dose optimization emerges, routine use of this clinical practice in IBD remains investigational.