Short Communication: Specimen Processing Impacts Tissue Tenofovir Pharmacokinetic Measurements

Area of Science:

• Pharmacology
• HIV/AIDS Research
• Biomedical Science

Background:

• Antiretroviral drug concentrations at HIV exposure sites are critical for pre-exposure chemoprophylaxis (PrEP) strategies.
• Understanding how biopsy collection methods affect drug levels is essential for accurate pharmacokinetic assessments.

Purpose of the Study:

• To evaluate the impact of tissue culture medium on tenofovir (TFV) and tenofovir diphosphate (TFV-DP) concentrations in colonic biopsies.
• To determine the implications of these changes for HIV PrEP assay development and interpretation.

Main Methods:

• Colonic biopsies were collected and analyzed for TFV and TFV-DP concentrations.
• Biopsies were incubated with and without tissue culture medium to assess changes in drug concentrations over time.
• Tissue weight changes and drug concentrations were measured and compared between conditions.

Main Results:

• Significant baseline interbiopsy variation was observed for both TFV (38% CV) and TFV-DP (33% CV).
• Incubation in medium increased tissue weight twofold, decreasing weight-adjusted TFV concentrations by 75%.
• Adjusted TFV-DP concentrations decreased by only 25% in medium, a change that was not statistically significant.

Conclusions:

• Colonic biopsies should be collected without medium to ensure accurate TFV concentration measurements.
• The presence of medium does not significantly affect TFV-DP levels, suggesting minimal impact on TFV-DP-dependent assays.
• Accurate assessment of tissue drug concentrations requires consideration of biopsy collection methods and drug-specific mechanisms of action.