Description of tenofovir levels in South African adults in the EVOLVE study: A pilot project to support therapeutic drug monitoring in HBV infection

This poster has been presented at the European Association for the Study of the Liver (EASL) 2025, to support the new Evaluation of Vukuzazi LiVEr disease - Hepatitis B 'EVOLVE-HBV' study based at the Africa Health Research Institute (AHRI) in KwaZulu-Natal, South Africa.

Hepatitis B virus (HBV) treatment is based on nucleos/tide analogue (NA) drugs for viral suppression, which overlap with therapy used for HIV; the first line agent is tenofovir (TFV). Therapeutic drug monitoring (TDM) has not been explored to optimize therapy in HBV. However, TDM is established in the HIV field, providing a framework to fill evidence gaps for HBV. In this pilot project, we describe the distribution of free tenofovir (TFV) and its metabolite, tenofovir-diphosphate (TFV-DP), in a South African (SA) population offered treatment for HIV monoinfection or HIV/HBV coinfection.

We set out to generate pilot data, aiming to:

1. Describe the distribution of TFV and TFV-DP, in South African (SA) adults offered treatment for HIV monoinfection or HIV/HBV coinfection.
2. Explore the relationship between levels of TFV and TFV-DP.
3. Identify any association between drug levels and suppression of HBV.

Methods

• This project is part of HBV-EVOLVE, a study of HBV infection conducted at the Africa Health Research Institute (AHRI) in KwaZulu Natal. Samples for analysis were collected by the Vukuzazi programme, which recruited residents in the AHRI Health and Demographic Surveillance Systems (HDSS) area, who were aged ≥15 years between May 2018 and March 2020.
• Dried Blood Spot (DBS) samples were selected to represent 40 adults living with HIV/HBV coinfection, and 40 with HIV mono-infection. All 80 are receiving antiretroviral therapy containing tenofovir. We also selected 20 HIV/HBV negative (control samples, presumed untreated).
• We used liquid chromatography tandem mass spectrometry (LC-MS) to measure drug levels of free tenofovir (TFV) and drug metabolite (TFV-DP). HBV viral suppression was defined as plasma HBV Viral load (VL) below the lower limit of quantitation, LLQ (<10 IU/mL). In keeping with other published results from AHRI, drug levels are presented as fmol/sample, where a ‘sample’ is defined as conversion from 5mm to 3mm punch from a DBS.
• Statistical analysis was performed using Pearsons’s or Kruskal-Wallis test, or linear regression in R.