Dose-Finding and Pharmacogenetic Study of Efavirenz in HIV-infected and HIV/TB Co-infected Infants and Children 3 Months to Less Than 36 Months of Age

An increasing number of children in resource-limited countries require treatment for both HIV and tuberculosis (TB); however, the options for antiretroviral therapy (ART) that is compatible with concurrent rifampin-containing anti-TB therapy are limited. As a result, treatment of HIV/TB-coinfected patients remains difficult with multiple drug interactions, very high pill burdens, overlapping toxicities, and possible immune reconstitution affecting treatment outcomes.

The use of EFV in adults and older children has allowed them to maintain their non-nucleoside reverse transcriptase inhibitor (NNRTI) backbone while receiving TB therapy including rifampin. In younger children with TB/HIV coinfection, the first-line treatment recommendation has been the triple-nucleoside reverse transcriptase inhibitor (NRTI) regimen. However, this regimen has been shown to be less effective than an EFV plus NNRTI-based regimen. In addition, triple-NRTI regimens in resource-limited settings are costly and have limited data in patients with TB, and monitoring for drug-related hypersensitivity reactions is difficult. All of these factors make EFV an attractive agent for use in HIV-infected pediatric patients with and without TB coinfection. This study will evaluate the safety, tolerance, and pharmacokinetics (PKs) of EFV when administered as opened capsules to pediatric patients younger than 3 years of age, with and without concomitant rifampin-containing anti-TB therapy. This study will also investigate genetic polymorphisms, including CYP 2B6, to help establish dosing guidelines.

This study will have two cohorts that will enroll at the same time. Cohort I, Step 1 will enroll HIV-infected infants without TB coinfection who are eligible for initiation of ART. Cohort I, Step 1 will be administered EFV for up to 24 weeks. EFV dosage, in Cohort I, Step 1, will range from 50 mg to 600 mg once daily, based on weight and CYP 2B6 genotype.

Participants in Cohort I Step 1 who develop TB or TB immune reconstitution inflammatory syndrome (IRIS) and require anti-TB medications will be allowed to enroll into Cohort I, Step 2, in which they will receive rifampin-containing anti-TB therapy and a higher dose of EFV (50 mg to 800 mg) to account for the anticipated impact of rifampin on EFV PKs. If participants in Cohort I, Step 2 require more than 24 weeks of anti-TB therapy and are unable to obtain EFV capsules from in-country sources, they may remain on the study longer than 24 weeks until discontinuing anti-TB therapy, up to 36 weeks study duration.

Participants in Cohort II will be HIV/TB coinfected infants who are eligible for ART and have been treated with and tolerated a rifampin-containing anti-TB treatment regimen for at least 1 week prior to enrollment. Participants in Cohort II will be followed while taking both rifampin-containing anti-TB and EFV therapy for 24 weeks; participants unable to obtain EFV capsules from in-country sources at the conclusion of the study may remain on the study until discontinuing anti-TB therapy, up to 36 weeks study duration. An estimated 10 to 20 of these participants from Cohort II will be followed every 4 weeks on study and provided EFV until completion of TB treatment (for up to 36 weeks study duration).