This study will assess and characterize the variability observed in the response to darunavir therapy, an antiretroviral medication used against the Human Immunodeficiency Virus (HIV). More specifically, it aims to quantify variations in the drug's blood concentrations and determine the sources of such variability, both genetic and non-genetic. In light of this information, current dosage guidelines will then be reviewed.

Data will be used to create a population pharmacokinetic model. Inter- and intra-individual pharmacokinetic variability will be quantified and linked to patient-specific covariates, both genetic and non-genetic in nature. Pharmacokinetic-pharmacodynamic relationships will be established, linking drug exposure to efficacy (as measured by CD4 cell count and viral load reduction) and toxicity (as measured by frequency and degree of adverse events). Simulations will be conducted for specific patient profiles and current dosage guidelines reviewed.

Pharmacokinetic design : combined sparse/intensive sampling

• Sparse sampling : One blood sample collected in each individual at a random post-intake time (during a routine visit to the hospital), up to three times over the course of the study period (months 1-18).
• Intensive sampling : Eight blood samples collected over six hours in a subset of twelve individuals (during an additional observation period, months 19-22).

Inclusion Criteria:

• Capable of giving informed consent
• HIV-positive
• Routinely followed at the Cliniques universitaires Saint-Luc
• Treated with darunavir

Inclusion Criteria (intensive sampling):

- Perfect adherence to treatment (as assessed by anamnesis and based on available PK data for each patient)

Exclusion Criteria:

- N/A