Evaluating an easy sampling method using dried blood spots to determine vedolizumab concentrations.

Area of Science:

• Pharmacology
• Analytical Chemistry
• Gastroenterology

Background:

• Vedolizumab (VDZ) trough concentrations correlate with therapeutic outcomes in inflammatory bowel diseases.
• Venous sampling is standard for VDZ therapeutic drug monitoring (TDM), but intensive sampling for pharmacokinetics is challenging.
• Dried blood spot (DBS) sampling offers a less invasive alternative for drug level monitoring.

Purpose of the Study:

• To develop and validate a DBS method for determining VDZ concentrations.
• To compare VDZ measurements in paired DBS and venous patient samples.
• To assess the utility of DBS for VDZ TDM and pharmacokinetic profiling.

Main Methods:

• VDZ was spiked into whole blood, spotted onto filter paper, dried, extracted, and quantified using ELISA.
• Paired DBS and serum samples from 41 VDZ-treated patients were analyzed.
• VDZ concentrations from DBS extracts were compared to serum concentrations.

Main Results:

• VDZ concentrations measured in DBS extracts showed a strong correlation with serum concentrations (Pearson r = 0.978, p < 0.0001).
• Hematocrit values did not significantly impact VDZ DBS/serum concentration ratios.
• VDZ DBS/serum ratios were generally stable over time within individual patients.

Conclusions:

• DBS sampling is a robust and validated alternative to venous blood collection for VDZ TDM.
• High correlation between DBS and serum VDZ concentrations supports its use for intensive sampling.
• DBS facilitates deeper insights into VDZ pharmacokinetics in patients with inflammatory bowel diseases.