Interaction Between High Dose Rifampicine and Efavirenz in Pulmonary Tuberculosis and HIV Co-infection

Justification: In vitro and animal studies have shown that increasing the dose of rifampicin (R) improves the R sterilising effect. If a similar effect can be demonstrated in the clinical setting, this could allow shortening treatment duration from 6 to 4 months, with good tolerance. Several phase 2 trials in HIV-negative patients are ongoing. We propose a first interaction study between efavirenz (EFV) and R20mg/Kg taking into consideration the absence of data about R induction at this dose. Due to an important inter-patient variability of the CYP2B6 polymorphism, the EFV pharmacokinetic (Pk) will be compared in same patients with and without TB treatment.

Principal objective: To compare the Pk parameters of EFV in HIV-TB co-infected patients, with and without TB treatment, using R at 10 and 20mg/Kg/day and EFV at 600 and 800mg/day.

Secondary objectives: To describe the Pk parameters of R and isoniazid (H); the TB treatment réponse (Mycobacterium tuberculosis culture conversion after 8 weeks(w) and cure after 24w) ; the virological response; the occurrence of severe adverse events, especially hepatic and neurological events; the treatment adherence; the genes involved in the EFV metabolism of EFV, R and H, and its relation with the Pk parameters.

Primary endpoint: AUC0-24, Cmax, Cmin, Tmax of EFV after 4w of TB treatment + ARV, and 4w after interruption of TB treatment.

Study design : phase 2 randomized, open label 3 arms therapeutic trial:

• Arm 1 : 8 weeks R20mg/Kg + H + pyrazinamide(Z)+ ethambutol(E) and EFV600mg/J + tenofovir-lamivudine
• Arm 2: 8 weeks R20mg/Kg + H+Z+E and EFV800mg/J + tenofovir-lamivudine
• Standard arm : 8 weeks R10mg/Kg + H+Z+E and EFV600mg/J + tenofovir-lamivudine

The ARV treatment will be initiated 4 weeks after starting TB treatment. After 8 weeks, all patients will receive 16 weeks of H+R with R at 10mg/Kg/day and EFV at 600mg/day. Treatment will be observed at home by a domiciliary treatment monitor (DTM). Patients will be followed during 28 weeks after starting TB treatment: weekly visit during first 8 weeks and then every 4 weeks.

Pk sampling for EFV, R and H will be at w2 (Pk1), w8 (Pk2) and w28 (Pk3). Liver function test and full blood count will be measured after 2, 4 and 8 weeks; sputum culture for TB at baseline and w8; HIV-1 RNA at baseline, w4, w12 and w24 and CD4 count at baseline and w24.

Eligibility criteria: > 18 years old; previously untreated pulmonary TB; Xpert confirming Mtb susceptible to R; body weight >45Kg; CD4 between 50 and 250cells/mm3; Karnofsky score >80%; ALAT/biluribin \<5xULN; no grade 4 clinical/biological sign; no pregnancy + barrier contraception; agree to participate and sign a consent form.

Randomisation block, 1:1:1. Sample size: 28 patients to show that the reduction of AUC of EFV with R20mg/Kg vs no R is not greater to 30%, with 20% expected reduction. Same number per study arm and 20% increase for patients' withdrawals or lost to follow-up resulting in a total of 105 patients.

Site: Mbarara (Uganda)