Atazanavir/Ritonavir and Zinc Pharmacokinetic Study

Atazanavir is a protease inhibitor (PI) and, like other agents in this class, requires pharmacological 'boosting' with the cytochrome p450 inhibitor ritonavir. Ritonavir slows the hepatic clearance of PIs, increasing plasma concentration and allowing the us eof lower, and less frequent doses. Atazanavir, boosted with ritonavir, is approved for once-daily use, is an internationally preferred first-line agent (in combination with a backbone of two nucleosides [NRTI]) and the most commonly prescribed PI in the UK. Once-daily atazanavir/ritonavir with two NRTI is an effective and well-tolerated therapeutic option for people living with HIV infection. The most common adverse event associated with atazanavir use is unconjugated hyperbilirubinaemia. This is observed in over 40% of patients and up to 5% of patients discontinue the drug due jaundice and/or scleral icterus.

Truvada is a fixed dose combination of two NRTI, tenofovir (245mg) and emtricitabine (200mg), administered as one tablet once daily. Truvada is a preferred NRTI backbone in national and international guidelines and the first line, therefore most commonly used, NRTI backbone in our unit.

Benefits of atazanavir/ritonavir compared with alternative agents include once daily dosing, low pill burden, low rates of gastro-intestinal toxicity and, importantly in a patient population already at an elevated risk of cardiovascular disease, a favourable lipid profile. If a simple intervention could reduce the incidence of hyperbilirubinaemia this could reduce the risk of treatment discontinuation/switch. The aim of this study is to explore the benefit, and safety, of adding zinc sulphate in patients on a stable regimen of Truvada, atazanavir and ritonavir.

Inclusion criteria

• The ability to understand and sign a written informed consent form, prior to participation in any screening procedure and must be willing to comply with all study requirements
• Male or non-pregnant, non-lactating females.
• Aged between 18 to 65 years, inclusive.
• Documented HIV-1 infection
• Plasma HIV RNA less than 40 copies/mL (note retesting of screening viral load is allowed).
• CD4 count > 100 at screening (note retesting of screening CD4 count is allowed).
• Receiving an antiretroviral regimen of Truvada and atazanavir/ritonavir for more than 3 months.
• Serum total bilirubin concentration greater than 25 micromol/L
• Agrees not to change regimen, outside the study recommendations, from baseline until end of the treatment period unless this is medically indicated as decided by their treating physician.

Exclusion criteria

• Any serious or active medical or psychiatric illness, which, in the opinion of the investigator, would interfere with subject treatment, assessment, or compliance with the protocol. This would include any active clinically significant renal, cardiac, hepatic, pulmonary, vascular, metabolic disorders or malignancy.
• Body mass index (BMI) >35 kg/m2
• Presence of any current active AIDS defining illness (Category C conditions according to the CDC Classification System for HIV Infection 1993) with the following exceptions:

• Stable cutaneous Kaposi's Sarcoma
• Clinically relevant alcohol or drug use (positive urine drug screen, with the exception of cannabinoids) or history of alcohol or drug use considered by the Investigator to be sufficient to hinder compliance with treatment, follow-up procedures or evaluation of adverse events.
• The use of zinc supplements for 1 month before screening and disallowed concomitant therapy (See Concomitant Medication and treatment, section 5.2) or medication that may interfere with the study results (as determined by the principal investigator).
• Females of childbearing potential who are not using effective non-hormonal birth control methods or not willing to continue using these birth control methods for at least 14 days after the end of the treatment period.
• Previous allergy to any of the constituents of the zinc sulphate tablets administered in this trial.
• Subjects with laboratory evidence of significantly decreased hepatic or renal function (as determined by the principal investigator).
• Exposure to any investigational drug or placebo within 4 weeks of first dose of study drug