Primary genotypic resistance of HIV-1 to the maturation inhibitor PA-457 in protease inhibitor-experienced patients

Sequences from 82 protease inhibitors (PI)-experienced patients were analysed for the presence of previously described in-vitro resistance mutations to PA-457 located in the C-terminal capside (H226Y, L231F, L231M) and in the N-terminal SP1 (A1V, A3T, A3V) within the CA-SP1 boundary domain. Overall, the CA-SP1 cleavage site was highly conserved in PI pre-treated patients and only one patient showed an L231M mutation. The impact of this mutation should be further addressed in vivo.     

Resistance to amprenavir before and after treatment with lopinavir/ritonavir in highly protease inhibitor-experienced HIV patients

Genotypes in nine highly protease inhibitor (PI)-experienced patients were studied before and after lopinavir/ritonavir (LPV/r) treatment. Resistance to amprenavir was the rule both before and after LPV/r treatment. Treatment with LPV/r can select for the 50 V mutation. In this setting, significant differences in the inference of the amprenavir phenotype from genotype were observed when using different algorithms.     

Effect of baseline protease genotype and phenotype on HIV response to atazanavir/ritonavir in treatment-experienced patients

OBJECTIVES: To assess the virologic response rates of atazanavir/ritonavir and lopinavir/ritonavir based on baseline genotype and phenotype. METHODS: Resistance analyses were performed on a Bristol-Myers Squibb-sponsored study comparing the safety and efficacy of atazanavir/ritonavir to lopinavir/ritonavir in treatment-experienced subjects at 48 weeks. Analyses evaluated virologic response based on the presence of baseline primary protease inhibitor mutations and baseline susceptibility. RESULTS: Less than 30% of atazanavir/ritonavir-treated patients were responders if substitutions at positions M46, G73, I84 or L90 were present in their HIV at baseline. In comparison, lopinavir/ritonavir response rates were less than 30% when protease substitutions at M46, I54, or I84 were present at baseline. The response rates were similar between atazanavir/ritonavir and lopinavir/ritonavir-treated subjects with zero to four baseline protease inhibitor mutations, but response rates were reduced if five or more baseline mutations were present: 0% for atazanavir/ritonavir compared with 28% for lopinavir/ritonavir. Baseline phenotype results showed that response rates were similar between atazanavir/ritonavir and lopinavir/ritonavir if shifts in susceptibility were zero to five, but response rates were lower if shifts were greater than five; 11% for atazanavir/ritonavir compared with 27% for lopinavir/ritonavir. CONCLUSIONS: Both type and number of baseline protease inhibitor mutations affected virologic response to atazanavir/ritonavir and lopinavir/ritonavir in treatment-experienced subjects. In addition, baseline phenotypic susceptibility could differentiate virologic response rates to the two drugs. These resistance analyses provide information on the likelihood of a virologic response to antiretroviral drugs based on baseline genotypic and phenotypic data, which is valuable to physicians and patients when choosing antiretroviral regimens.     

Pharmacokinetics of rifabutin during atazanavir/ritonavir co-administration in HIV-infected TB patients

Background & objective

Rifabutin (RBT) is the rifamycin that is recommended to treat tuberculosis (TB) in HIV-infected individuals during combination antiretroviral therapy (ART) containing HIV protease inhibitors (PIs). We studied the pharmacokinetics of rifabutin at doses of 300 mg thrice weekly and 150 mg daily during concomitant atazanavir/ritonavir (ATZ/r) administration in adult HIV-infected TB patients treated in the Revised National TB Control Programme (RNTCP) in India.

The effects of HIV protease inhibitors atazanavir and lopinavir/ritonavir on insulin sensitivity in HIV-seronegative healthy adults

BACKGROUND: Therapy with some HIV protease inhibitors (PI) contributes to insulin resistance and type 2 diabetes mellitus, by inhibition of insulin-sensitive glucose transporters. Atazanavir (ATV) is a new PI with substantially less in vitro effect on glucose transport than observed with other PI, including lopinavir (LPV) or ritonavir (RTV). METHODS: Randomized, double-blind, crossover study of the effect of 5 days of administering ATV, lopinavir/ritonavir (LPV/r) or placebo on insulin-stimulated glucose disposal in 30 healthy HIV-negative subjects. Each subject was studied on two of three possible treatments with a wash-out period between treatments. RESULTS: The mean insulin-stimulated glucose disposal (mg/min per kg body weight) per unit insulin (microU/ml) (M/I) was 9.88, 9.80 and 7.52 for placebo, ATV and LPV/r, respectively (SEM, 0.84 for all). There was no significant difference between ATV and placebo. The M/I for LPV/r was 23% lower than that for ATV (P = 0.010) and 24% lower than that for placebo (P = 0.008). The mean glycogen storage rates were 3.85, 4.00 and 2.54 mg/min per kg for placebo, ATV and LPV/r, respectively (SEM, 0.39 for all). There was no significant difference between ATV and placebo. The glycogen storage rate for LPV/r was 36% lower than ATV (P = 0.003) and 34% lower than placebo (P = 0.006). CONCLUSIONS: ATV given to healthy subjects for 5 days did not affect insulin sensitivity, while LPV/r induced insulin resistance. This observation is consistent with differential in vitro effects of these PI on glucose transport. Further data are needed to assess clinical implications for body composition.     

Clinical significance of hyperbilirubinemia among HIV-1-infected patients treated with atazanavir/ritonavir through 96 weeks in the CASTLE study

CASTLE was a randomized 96-week study that demonstrated that atazanavir/ritonavir (ATV/r) was noninferior to lopinavir/ritonavir (LPV/r) in treatment-na?ve HIV-infected patients. Analyses were carried out among patients who received ATV/r in the CASTLE study to better understand the clinical significance of unconjugated hyperbilirubinemia associated with administration of boosted ATV. Hyperbilirubinemia was defined as total bilirubin (conjugated and unconjugated) elevation greater than 2.5 times the upper limit of normal (grade 3-4). Patients in the ATV/r arm were assessed based on the presence or absence of hyperbilirubinemia through week 96. Analyses included number of confirmed virologic responders (CVR; HIV RNA<50 copies per milliliter), impact of hyperbilirubinemia on symptoms, elevations in liver enzymes, patient quality of life, and medication adherence. Through 96 weeks in the CASTLE study, 44% of patients who received ATV/r had hyperbilirubinemia at any time point, and between 12.5% and 21.6% had hyperbilirubinemia at any single study visit. At 96 weeks, 74% of patients overall and 84% and 69% of patients with and without hyperbilirubinemia, respectively, achieved CVR. Symptoms of jaundice or scleral icterus occurred in 5% of patients overall and in 11% with hyperbilirubinemia and 0% without hyperbilirubinemia. Four percent of patients with and 3% of patients without hyperbilirubinemia had grade 3-4 elevations in liver transaminases. Less than 1% of patients discontinued treatment due to hyperbilirubinemia. There were no differences in quality of life or adherence between patients with or without hyperbilirubinemia. In the CASTLE study, hyperbilirubinemia observed in the ATV/r group did not negatively impact clinical outcomes in HIV-infected patients.     

Impact of switching from lopinavir/ritonavir to atazanavir/ritonavir on body fat redistribution in virologically suppressed HIV-infected adults

Changes in body fat distribution in virologically suppressed HIV-infected patients switching from lopinavir/ritonavir (LPV/r) to atazanavir/ritonavir (ATV/r) were assessed. A prospective comparative study was conducted of 37 patients receiving LPV/r regimens switching to ATV/r with 46 patients continuing with LPV/r. Body composition was assessed with whole-body dual-energy x-ray absorptiometry (DXA). Abdominal CT scans were also performed in a subset of patients. Groups were comparable in baseline demographic, clinical, and anthropometric characteristics. After 12 months, peripheral fat did not change significantly, but an increase in trunk fat was observed only in the ATV/r group (0.87 kg, p = 0.021). The percentage of patients with an increase ≥20% in total fat was 37.8% and 15.2% in the ATV/r and LPV/r groups, respectively (p = 0.018). In the ATV/r group, the increase in trunk fat (9.4%) was significantly higher than in peripheral fat (3.7%) (p = 0.007), leading to a significant increase in fat mass ratio (3.76%, p = 0.028), whereas no significant differences were found among LPV/r patients. CT scans showed that abdominal fat increase corresponded to both visceral (28%, p = 0.008) and subcutaneous fat (42%, p = 0.008). These data suggest that switching from LPV/r to ATV/r is associated with increased trunk fat, both subcutaneous and visceral.     

Steady-state pharmacokinetics of once-daily fosamprenavir/ritonavir and atazanavir/ritonavir alone and in combination with 20 mg omeprazole in healthy volunteers

OBJECTIVES: Use of proton pump inhibitors in HIV-infected patients is common. The purpose of this study was to determine the steady-state pharmacokinetics of once-daily (qd) fosamprenavir/ritonavir (FPV/r) and atazanavir/ritonavir (ATV/r) alone and in combination with 20 mg qd omeprazole (OMP) in healthy volunteers. DESIGN AND METHODS: A prospective, open-label, single-site, two-period, crossover pharmacokinetic study was carried out in healthy volunteers. Subjects received either qd FPV/r 1400 mg/200 mg or ATV/r 300 mg/100 mg in the morning for 14 days and then 20 mg OMP in the evening for an additional 7 days. The pharmacokinetics were assessed over 24 h on days 14 and 21. Following a 2-week washout, subjects repeated the process with the other regimen. Trough protease inhibitor (PI) concentrations were taken on day 16 of each period to assess the impact of a single dose of OMP on ATV and amprenavir (APV) concentrations. Plasma ATV and APV pharmacokinetic parameters were assessed by noncompartmental analysis; geometric mean ratios (GMRs; PI+OMP/PI; 90% confidence interval) were calculated between days 14 and 21. RESULTS: Nineteen healthy, non-HIV-infected volunteers were evaluated. OMP reduced ATV exposure [area under the concentration curve at 0-24 h (AUC0-24 h)] and the minimum drug concentration (Cmin) by 27% each. In contrast, APV exposure and Cmin were decreased by 4 and 2%, respectively. Four subjects (21%) experienced greater than 50% declines in both ATV AUC0-24 h and Cmin after the addition of OMP; this was not observed in any subject following receipt of FPV/r. No alterations in APV or ATV trough concentrations were observed following a single dose of OMP. CONCLUSIONS: The addition of 20 mg OMP administered in the evening has minimal effect on APV pharmacokinetics. In contrast, ATV pharmacokinetics were altered; a number of ATV-treated subjects experienced pronounced declines in exposures upon the addition of 20 mg OMP administered in the evening, whereas others experienced little to no change.     

Effects of atazanavir/ritonavir and lopinavir/ritonavir on glucose uptake and insulin sensitivity: demonstrable differences in vitro and clinically

BACKGROUND: The HIV protease inhibitor (PI) atazanavir does not impair insulin sensitivity acutely but ritonavir and lopinavir induce insulin resistance at therapeutic concentrations. OBJECTIVE: To test the hypothesis that atazanavir combined with a lower dose of ritonavir would have significantly less effect on glucose metabolism than lopinavir/ritonavir in vitro and clinically. METHODS: Glucose uptake was measured following insulin stimulation in differentiated human adipocytes in the presence of ritonavir (2 micromol/l) combined with either atazanavir or lopinavir (3-30 micromol/l). These data were examined clinically using the hyperinsulinemic euglycemic clamp and oral glucose tolerance testing (OGTT) in 26 healthy HIV-negative men treated with atazanavir/ritonavir (300/100 mg once daily) and lopinavir/ritonavir (400/100 mg twice daily) for 10 days in a randomized cross-over study. RESULTS: Atazanavir inhibited glucose uptake in vitro significantly less than lopinavir and ritonavir at all concentrations. Ritonavir (2 micromol/l) combined with either atazanavir or lopinavir (3-30 micromol/l) did not further inhibit glucose uptake. During euglycemic clamp, there was no significant change from baseline insulin sensitivity with atazanavir/ritonavir (P = 0.132), while insulin sensitivity significantly decreased with lopinavir/ritonavir from the baseline (-25%; P < 0.001) and from that seen with atazanavir/ritonavir (-18%; P = 0.023). During OGTT, the HOMA insulin resistance index significantly increased from baseline at 120 min with atazanavir/ritonavir and at 150 min with lopinavir/ritonavir. The area under the curve of glucose increased significantly with lopinavir/ritonavir but not with atazanavir/ritonavir. CONCLUSIONS: Both glucose uptake in vitro and clinical insulin sensitivity in healthy volunteers demonstrate differential effects on glucose metabolism by the combination PI atazanavir/ritonavir and lopinavir/ritonavir.