Last updated on February 2018

Pharmacokinetics of Efavirenz in the Presence of Rifampicin and Isoniazid


Brief description of study

The purpose of the study is to measure the drug levels in the blood of HIV-infected individuals taking anti- HIV medication efavirenz 400 mg once daily in the presence of anti-TB medication rifampicin and isoniazid. The study is being run in two-stages - London (Stage 1) and Kampala (Stage 2).

In London (Stage 1): HIV-1 infected patients (without tuberculosis infection) on established treatment with a combination based on 600 mg efavirenz dose will be recruited.

In Kampala (Stage 2): Patients with both HIV-1 and tuberculosis infection being treated with 600 mg efavirenz combination for HIV AND undergoing TB treatment with a dual therapy regimen contaning rifampicin and isoniazid will be recruited.

Efavirenz-containing regimens are recommended as first-line therapy for HIV-TB co-infected patients. It has been shown there is a lack of a significant difference between efavirenz 400 mg and efavirenz 600 mg, indicating that 400 mg efavirenz is non-inferior to the standard dose.

The advantages of antiretroviral dose reductions may translate into greater benefits for more individuals infected by HIV globally, since they may allow access programs to reach higher numbers of infected patients and compensate for the finite global manufacturing capacity and increasing demand. For efavirenz, significant price reductions have been achieved through elimination of trade, logistics and manufacturing capacity barriers, and further price reductions could be achieved with a significant reduction in the cost of pharmaceutical ingredients. However, no data on the PK and effectiveness of efavirenz 400 mg once daily during TB treatment has been produced. Given that many patients on Efavirenz- based ART will need to be treated for TB during their lifetime and rifampicin is one of the most commonly used treatment for tuberculosis, it is important to study the reduced dose under carefully monitored conditions prior to roll out of a lower dose standard treatment. Therefore, we aim to investigate the PK of efavirenz 400 mg once daily in HIV-infected individuals in the presence of rifampicin and isoniazid in London, UK and in HIV/TB-co-infected individuals on dual anti-TB treatment in Kampala, Uganda

Detailed Study Description

Protocol Number: SSAT 062

EudraCT Number: 2014-002608-26

Name of Investigational Product: Sustiva/Stocrin/Atripla; Rifinah or local generic 300/150 Name of active ingredients: Efavirenz/ rifampicin/ isoniazid

Study title:Steady-state pharmacokinetics of efavirenz (Sustiva/Stocrin) 400 mg once daily in the presence of rifampicin and isoniazid (Rifinah or the local generics)

Name of Non Investigational Medicinal Product: 2 nucleoside reverse transcriptase inhibitors (Tenofovir/ emtricitabine or tenofovir/lamivudine or zidovudine/lamivudine)

Phase of study: Phase I

Objectives: The objectives of this study are:

Primary
  1. To evaluate the steady-state pharmacokinetics of efavirenz (Sustiva/Stocrin) 400 mg once daily during co-administration with rifampicin and isoniazid (Rifinah or local generic)
Secondary
  1. To assess the safety and tolerability of efavirenz (Sustiva/Stocrin) 400 mg once daily during co-administration with rifampicin and isoniazid (Rifinah or local generic)
  2. To investigate the association between genetic polymorphisms in drug disposition genes and drug exposure
  3. Exploratory: To investigate the impact of anti-retroviral drugs on platelet function in people living with HIV

Study design:

Two-centre, two-stage, 98/99 days in London (Stage 1) and 28 days in Kampala (Stage 2) (excluding screening and follow up), open-label, pharmacokinetic study

Indication

London: HIV-1 infected patients (without tuberculosis infection) on established treatment with a combination based on 600 mg efavirenz dose Kampala: Patient with both HIV-1 and tuberculosis infection being treated with 600 mg efavirenz combination for HIV AND undergoing TB treatment with a dual therapy regimen contaning rifampicin and isoniazid

Methodology

Measurements of efavirenz concentrations and efavirenz pharmacokinetic profiles in the absence (Stage 1 only) and in the presence of rifampicin and isoniazid in two populations of HIV-infected individuals:

  1. without TB (Stage 1, London)
  2. with TB (Stage 2, Kampala)

Planned sample size:

Stage 1, London: For this sequential design, a sample size of 25 patients would provide at least 80% power to detect a decrease in efavirenz Cmin of 20% during the combined rifampicin/isoniazid-efavirenz phase, compared to the efavirenz alone phase.

Up to 40 subjects may be screened and enrolled to have 25 HIV-infected patients completing the study.

Stage 2, Kampala: A pilot study in 10 patients in Uganda with HIV and TB co-infection and on anti-HIV treatment and anti-TB treatment will also be performed to validate findings of the London PK study in a TB-infected population.

Up to 25 subjects may be screened and enrolled to have 10 HIV/TB-co-infected patients completing the pilot sub-study

Summary of eligibility criteria:

Stage 1, London: HIV-1 infected males or females of at least 18 years, treated with a stable efavirenz based combination regimen (tenofovir/ emtricitabine or tenofovir/lamivudine or zidovudine/lamivudine) for at least the preceding 12 weeks and with an undetectable viral load and a CD4+ T-cell count > 100 cell/mm3.

Stage 2, Kampala: HIV-1 infected males or females of at least 18 years, treated with a stable efavirenz based combination regimen (tenofovir /emtricitabine or tenofovir/lamivudine or zidovudine/lamivudine) for at least the preceding 12 weeks, with a CD4+ T-cell count > 100 cell/mm3, co-infected with TB and undergoing anti-TB treatment with rifampicin and isoniazid-containing regimens.

Duration of treatment:

London: 98 / 99 (+/- 1) days (excluding screening and follow up visits) Kampala: 28 days (+/- 7) days (excluding screening and follow up visits)

Dose and route of administration:

All study drugs will be administered orally to subjects with the following schedule:

Stage 1, London:

  • Phase 1 (2 weeks): tenofovir/emtricitabine or tenofovir/lamivudine or zidovudine/lamivudine plus efavirenz (Sustiva/Stocrin) 400 mg once daily
  • Phase 2 (12 weeks): tenofovir/emtricitabine or tenofovir /lamivudine or zidovudine/lamivudine) plus efavirenz (Sustiva/Stocrin) 400 mg once daily plus Rifinah or local generics once daily (rifampicin 600 mg and isoniazid 300 mg if 50kg or rifampicin 450 mg and isoniazid 300 mg if <50kg.)

Stage 2, Kampala:

Tenofovir/emtricitabine or lamivudine or zidovudine/lamivudine plus efavirenz (Sustiva/Stocrin) 400 mg once daily plus Rifinah or local generics once daily (rifampicin 600 mg and isoniazid 300 mg if 50 kg or rifampicin 450 mg and isoniazid 300 mg if < 50kg).

Criteria for evaluation:

Stage 1, London: Pharmacokinetic (PK) parameters of efavirenz will be evaluated on blood drawn on days:

  • 14/15 (2 weeks after reducing efavirenz dose from 600 mg to 400 mg)
  • 42/43 (4 weeks after Rifinah or local generics initiation at start of phase 2) and
  • 98/99 (12 weeks after Rifinah or local generics initiation)
  • PK profile at 0 (pre-dose), 2, 4, 8, 12 and 24 hours post administered dose.

Stage 2, Kampala: Pharmacokinetic parameters of efavirenz will be evaluated on blood drawn

on
  • days 28 +/- 7 days (while on anti-TB medications)
  • PK profile at 0 (pre-dose), 2, 4, 8, 12 and 24 hours post last dose.

Safety and tolerability of medications will also be assessed by questioning to collect adverse event symptoms, physical examination and laboratory parameters, performed at regular intervals during the study, including efavirenz therapeutic drug monitoring (TDM) once/twice a week.

Endpoints

Primary endpoint:

  1. Steady state plasma concentrations of efavirenz when administered at 400 mg once daily in the presence of rifampicin and isoniazid

Secondary endpoints:

  1. Safety and tolerability of efavirenz when administered at 400 mg once daily in the presence of rifampicin and isoniazid.
  2. Relationship between genetic polymorphisms and exposure to efavirenz.
  3. Exploratory: impact of anti-retroviral drugs or platelet function in people living with HIV.

Clinical Study Identifier: NCT02832778

Contact Investigators or Research Sites near you

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Mohammed Lamorde, MBBS, MRCP, PhD

Infectious Diseases Insitute
Kampala, Uganda
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Marta Boffito

Chelsea and Westminster Hospital NHS Foundation Trust
London, United Kingdom
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Recruitment Status: Open


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