Cytochrome P450 2B6 (CYP2B6) and constitutive androstane receptor (CAR) polymorphisms are associated with early discontinuation of efavirenz-containing regimens

Objectives Cytochrome P450 2B6 (CYP2B6) is responsible for the metabolic clearance of efavirenz and single nucleotide polymorphisms (SNPs) in the CYP2B6 gene are associated with efavirenz pharmacokinetics. Since the constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) correlate with CYP2B6 in liver, and a CAR polymorphism (rs2307424) and smoking correlate with efavirenz plasma concentrations, we investigated their association with early (<3 months) discontinuation of efavirenz therapy. Methods Three hundred and seventy-three patients initiating therapy with an efavirenz-based regimen were included (278 white patients and 95 black patients; 293 male). DNA was extracted from whole blood and genotyping for CYP2B6 (516G → T, rs3745274), CAR (540C → T, rs2307424) and PXR (44477T → C, rs1523130; 63396C → T, rs2472677; and 69789A → G, rs763645) was conducted. Binary logistic regression using the backwards method was employed to assess the influence of SNPs and demographics on early discontinuation. Results Of the 373 patients, 131 withdrew from therapy within the first 3 months. Black ethnicity [odds ratio (OR) = 0.27; P = 0.0001], CYP2B6 516TT (OR = 2.81; P = 0.006), CAR rs2307424 CC (OR = 1.92; P = 0.007) and smoking status (OR = 0.45; P = 0.002) were associated with discontinuation within 3 months. Conclusions These data indicate that genetic variability in CYP2B6 and CAR contributes to early treatment discontinuation for efavirenz-based antiretroviral regimens. Further studies are now required to define the clinical utility of these association

Maraviroc for previously treated patients with R5 HIV-1 infection

Background CC chemokine receptor 5 antagonists are a new class of antiretroviral agents.Methods We conducted two double- blind, placebo- controlled, phase 3 studies - Maraviroc versus Optimized Therapy in Viremic Antiretroviral Treatment- Experienced Patients ( MOTIVATE) 1 and MOTIVATE 2 - with patients who had R5 human immunodeficiency virus type 1 ( HIV- 1) only. They had been treated with or had resistance to three antiretroviral- drug classes and had HIV- 1 RNA levels of more than 5000 copies per milliliter. The patients were randomly assigned to one of three antiretroviral regimens consisting of maraviroc once daily, maraviroc twice daily, or placebo, each of which included optimized background therapy ( OBT) based on treatment history and drug- resistance testing. Safety and efficacy were assessed after 48 weeks.Results A total of 1049 patients received the randomly assigned study drug; the mean baseline HIV- 1 RNA level was 72,400 copies per milliliter, and the median CD4 cell count was 169 per cubic millimeter. At 48 weeks, in both studies, the mean change in HIV- 1 RNA from baseline was greater with maraviroc than with placebo: - 1.66 and - 1.82 log(10) copies per milliliter with the once- daily and twice- daily regimens, respectively, versus - 0.80 with placebo in MOTIVATE 1, and - 1.72 and - 1.87 log(10) copies per milliliter, respectively, versus - 0.76 with placebo in MOTIVATE 2. More patients receiving maraviroc once or twice daily had HIV- 1 RNA levels of less than 50 copies per milliliter ( 42% and 47%, respectively, vs. 16% in the placebo group in MOTIVATE 1; 45% in both maraviroc groups vs. 18% in MOTIVATE 2; P&lt; 0.001 for both comparisons in each study). The change from baseline in CD4 counts was also greater with maraviroc once or twice daily than with placebo ( increases of 113 and 122 per cubic millimeter, respectively, vs. 54 in MOTIVATE 1; increases of 122 and 128 per cubic millimeter, respectively, vs. 69 in MOTIVATE 2; P&lt; 0.001 for both comparisons in each study). Frequencies of adverse events were similar among the groups.Conclusions Maraviroc, as compared with placebo, resulted in significantly greater suppression of HIV- 1 and greater increases in CD4 cell counts at 48 weeks in previously treated patients with R5 HIV- 1 who were receiving OBT. (ClinicalTrials. gov numbers, NCT00098306 and NCT00098722.)