Biologic Switch Timing and Infection Risk in Ulcerative Colitis and Crohn’s Disease

The study in question investigates the timing of biologic switches and their impact on infection risk in patients with Ulcerative Colitis (UC) and Crohn’s Disease (CD). It specifically examines the difference in infection risk between overlapping switches (OS), where the switch occurs within less than 5 half-lives of the prior biologic, and non-overlapping switches (NOS), where the switch occurs after more than 5 half-lives.

### Key Findings:

1. **Study Population and Methodology**:

• The study analyzed data from 11,992 biologic-naïve adults with UC or CD who initiated biologic therapy between 2017 and 2022.
• Among these, 1,293 patients underwent a biologic switch and were categorized into OS (<5 half-lives) and NOS (>5 half-lives) groups.
• Infection outcomes were evaluated over a 90-day follow-up using advanced statistical models to account for confounding variables.

2. **Prevalence of Overlapping Switches**:

• Overlapping switches were common, comprising 64.2% of all biologic switches.

3. **Infection Risk Outcomes**:

• The adjusted incidence rates of both any infection and serious infections (requiring hospitalization) were similar between the OS and NOS groups.
• There were no statistically significant differences in the adjusted hazard ratios for serious infections between the two switching strategies.
• Sensitivity analyses using alternative washout periods (e.g., 28 days or 3 half-lives) showed consistent results. However, a slight increase in non-serious infections was observed with very short washout periods.

4. **Implications for Clinical Practice**:

• The findings suggest that overlapping biologic switches do not elevate the risk of serious infections in UC/CD patients.
• Shorter washout periods may be safe and could enable more timely disease control, improving patient outcomes and clinical trial feasibility.
• This challenges the FDA’s recommendation for a 5 half-life washout period, providing evidence for more flexible switching strategies in real-world clinical practice.

### Conclusion:

The study provides reassurance that overlapping biologic switches can be safely performed without increasing the risk of serious infections in patients with UC or CD. This supports the adoption of more flexible switching strategies, which may help achieve better disease management and timely treatment adjustments.