Pharmacokinetics, SAfety/tolerability, and EFficacy of high-dose RIFampicin in tuberculosis-HIV co-infected patients on efavirenz- or dolutegravir-based antiretroviral therapy: study protocol for an open-label, phase II clinical trial (SAEFRIF).

BACKGROUND: Tuberculosis (TB) is a significant public health problem that causes substantial morbidity and mortality. Current first-line anti-TB chemotherapy, although very effective, has limitations including long-treatment duration with a possibility of non-adherence, drug interactions, and toxicities. Dose escalation of rifampicin, an important drug within the regimen, has been proposed as a potential route to higher treatment efficacy with shorter duration and some studies have suggested that dose escalation is safe; however, these have almost entirely been conducted among human immunodeficiency (HIV)-negative TB patients. TB-HIV co-infected patients on antiretroviral therapy (ART) are at increased risk of drug-drug interactions and drug-related toxicities. This study aims to determine the safety of higher doses of rifampicin and its effect on the pharmacokinetics of efavirenz (EFV) and dolutegravir (DTG) in TB-HIV co-infected patients. METHODS: This study is a randomized, open-label, phase IIb clinical trial among TB-HIV infected adult outpatients attending an HIV clinic in Kampala, Uganda. Patients newly diagnosed with TB will be randomized to either standard-dose or high-dose rifampicin (35 mg/kg) alongside standard TB treatment. ART-naïve patients will be randomly assigned to first-line ART regimens (DTG or EFV). Those who are already on ART (DTG or EFV) at enrollment will be continued on the same ART regimen but with dose adjustment of DTG to twice daily dosing. Participants will be followed every 2 weeks with assessment for toxicities at each visit and measurement of drug concentrations at week 6. At the end of intensive-phase therapy (8 weeks), all participants will be initiated on continuation-phase treatment using standard-dose rifampicin and isoniazid. DISCUSSION: This study should avail us with evidence about the effect of higher doses of rifampicin on the pharmacokinetics of EFV and DTG among TB-HIV co-infected patients. The trial should also help us to understand safety concerns of high-dose rifampicin among this vulnerable cohort. TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT03982277. Registered retrospectively on 11 June 2019.

CYP2B6 Genetic Polymorphisms, Depression, and Viral Suppression in Adults Living with HIV Initiating Efavirenz-Containing Antiretroviral Therapy Regimens in Uganda: Pooled Analysis of Two Prospective Studies.

Single-nucleotide polymorphisms (SNPs) in CYP2B6 have been shown to predict variation in plasma efavirenz concentrations, but associations between these SNPs and efavirenz-mediated depression and viral suppression are less well described. We evaluated three SNPs in CYP2B6 (rs3745274, rs28399499, and rs4803419) in Ugandan persons living with HIV. To define exposure, we used previously published pharmacokinetic modeling data to categorize participants as normal, intermediate, and poor efavirenz metabolizers. Our outcomes were probable depression in the first 2 years after antiretroviral therapy (ART) initiation (mean score of >1.75 on the Hopkins Symptom Depression Checklist) and viral suppression 6 months after ART initiation. We fit generalized estimating equation and modified Poisson regression models adjusted for demographic, clinical, and psychosocial characteristics with or without individuals with depression at the time of ART initiation. Among 242 participants, there were no differences in the pre-ART depression or viral load by efavirenz metabolism strata (p > .05). Participants were classified as normal (32%), intermediate (50%), and poor (18%) metabolizers. Seven percent (56/242) of follow-up visits met criteria for depression. Eighty-five percent (167/202) of participants who completed a 6-month visit achieved viral suppression. CYP2B6 metabolizer strata did not have a statistically significant association with either depression [adjusted risk ratio (aRR) comparing intermediate or poor vs. normal, 1.46; 95% confidence interval (CI), 0.72-2.95] or 6-month viral suppression (aRR, 1.01; 95% CI, 0.88-1.15). However, in analyses restricted to participants without pre-ART depression, poorer CYP2B6 metabolism was associated with increased odds of depression (adjusted odds ratio, 4.11; 95% CI, 1.04-16.20). Efavirenz-metabolizing allele patterns are strongly associated with risk of incident depression. Future work should elucidate further region-specific gene-environment interactions and whether alternate polymorphisms may be associated with efavirenz metabolism.

Prevalence of CYP2B6 polymorphisms in Argentinians: the role of genetic testing.

CYP2B6 is a highly polymorphic isoenzyme involved in the metabolism of many drugs including cyclophosphamide, bupropion, and efavirenz. A single nucleotide polymorphism (SNP) in CYP2B6 (516G>T) resulted in decreased expression and function associated with the CYP2B6*6 haplotype. Among the clinical implications of this phenotype, decreased activation of cyclophosphamide and increased plasma levels of efavirenz associated with increased central nervous system toxicity have been reported. The frequency of the CYP2B6 (516G>T) SNP has been studied in several different populations, but there is no data regarding distribution among Argentinians. In this study, 102 DNA samples from healthy volunteers were analyzed using a polymerase chain reaction-restriction fragment length polymorphism reaction specific for the CYP2B6 (516G>T) SNP. Our results showed a prevalence of 71.08% for the G allele and 28.92% for the T allele. This was distributed as 52.9% for the GG genotype (reduced dosage required), 36.6% for the GT genotype (normal dosage range), and 10.8% for the TT genotype (high drug toxicity). There was no preferential gender distribution observed. The relatively high prevalence of the TT genotype in our population supports the clinical use of genotyping as an additional tool in personalized medicine.