Yesterday’s post outlined expert recommendations for proactive therapeutic drug monitoring (pTDM).  Today’s post reviews a study (NV Casteele et al. Clin Gastroenterol Hepatol 2019; 17: 1814-21) which identifies optimal levels at earlier time points. The authors note that “higher infliximab (IFX) concentrations during induction therapy  are correlated with long-term relapse-free and colectomy-free survival.”

The authors analyzed data from 484 patients with active ulcerative colitis (UC) from two double-blind, placebo-controlled, parallel group studies: ACT-1 and ACT-2.

Key findings:

• IFX levels ≥18.6 mcg/mL at week 2, ≥10.6 mcg/mL at week 6, and ≥34.9 mcg/mL at week 8 were associated with Mayo endoscopic scores (MES) of ≤1 at week 8.
• IFX level of ≥5.1 mcg/mL at week 14 was associated with MES of ≤1 at week 30
• IFX level of ≥6.7 mcg/mL at week 14 was associated with MES of 0 at week 30

My take: In pediatric patients receiving monotherapy with an anti-TNF agent, checking earlier levels (week 6, week 8, or week 10) may help avoid low troughs which are associated with a higher likelihood of treatment failure.  This study provides guidance on target levels at earlier time points.

Related blog posts:

• Briefly Noted: Induction Infliximab Levels Infliximab level ≥18 mcg/mL at week 6 was strongly associated with clinical and biologic response as well as achieving an infliximab level ≥5 mcg/mL at week 14 (AUC 0.85).
• Is Standard Infliximab Dose Too Low in Pediatrics?
• Combination Therapy Study Points to Central Role of Adequate Drug Levels
• Can Therapeutic Drug Monitoring with Monotherapy Achieve Similar Results as Combination Therapy for IBD? | gutsandgrowth The authors utilized TDM at week 10.  If the IFX level was <20 mcg/mL, the dose and frequency of infliximab were both adjusted. If the level was between 20 & 25, either the frequency was adjusted or no adjustment, and if the level was >25, then no adjustment in dosing was performed.
• Don’t be Fooled About Withdrawing Immunomodulator Cotherapy -Look Past the Headline

Disclaimer: These blog posts are for educational purposes only. Specific dosing of medications/diets (along with potential adverse effects) should be confirmed by prescribing physician/nutritionist.  This content is not a substitute for medical advice, diagnosis or treatment provided by a qualified healthcare provider. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a condition.

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