Overcoming obstacles to the success of protease inhibitors in highly active antiretroviral therapy regimens

Role of systemic inflammation scores for prediction of clinical outcomes in patients treated with atazanavir not boosted by ritonavir in the Italian MASTER cohort

Background

Atazanavir (ATV) not boosted by ritonavir (uATV) has been frequently used in the past for switching combination antiretroviral therapy (cART). However, the clinical outcomes and predictors of such strategy are unknown.

Methods

An observational study was carried out on the Italian MASTER, selecting HIV infected patients on cART switching to an uATV-containing regimen. Baseline was set as the last visit before uATV initiation. In the primary analysis, a composite clinical end-point was defined as the first occurring of any condition among: liver, cardiovascular, kidney, diabetes, non AIDS related cancer or death events. Incidence of AIDS events and incidence of composite clinical end-point were estimated. Kaplan-Meier and multivariable Cox regression analysis were used to assess predictors of the composite clinical end-point.

Results

436 patients were observed. The majority of patients were males (61.5%) and Italians (85.3%), mean age was 42.7 years (IQR: 37.7–42), the most frequent route of transmission was heterosexual intercourse (47%), followed by injection drug use (25%) and homosexual contact (24%); the rate of HCV-Ab positivity was 16.3%. Patients were observed for a median time of 882 days (IQR: 252-1,769) under uATV. We recorded 93 clinical events (3 cardiovascular events, 20 kidney diseases, 33 liver diseases, 9 non AIDS related cancers, 21 diabetes, 7 AIDS events), and 19 deaths, accounting for an incidence of 3.7 (composite) events per 100 PYFU. At multivariable analysis, factors associated with the composite clinical end-point were intravenous drug use as risk factor for HIV acquisition vs. heterosexual intercourses [HR: 2.608, 95% CI 1.31–5.19, p = 0.0063], HIV RNA per Log₁₀ copies/ml higher [HR: 1.612, 95% CI 1.278–2.034, p < 0.0001], number of switches in the nucleoside/nucleotide (NRTI) backbone of cART (performed to compose the uATV regimen under study or occurred in the past) per each more [HR: 1.085, 95% CI 1.025–1.15, p = 0.0051], Fib-4 score per unit higher [HR: 1.03, 95% CI 1.018–1.043, p < 0.0001] and Neutrophil/lymphocytes ratio (NLR inflammation score) per Log₁₀ higher [HR: 1.319, 95% CI 1.047–1.662, p = 0.0188].

Conclusions

Intravenous drug users with high HIV RNA, high Fib-4 levels and more heavily exposed to antiretroviral drugs appeared to be more at risk of clinical events. Interestingly, high levels of inflammation measured through NLR, were also associated with clinical events. So, these patients should be monitored more strictly.

Effect of polarization on HIV-1protease and fluoro-substituted inhibitors binding energies by large scale molecular dynamics simulations

Molecular dynamics simulations in explicit water are carried out to study the binding of six inhibitors to HIV-1 protease (PR) for up to 700 ns using the standard AMBER force field and polarized protein-specific charge (PPC). PPC is derived from quantum mechanical calculation for protein in solution and therefore it includes electronic polarization effect. Our results show that in all six systems, the bridging water W301 drifts away from the binding pocket in AMBER simulation. However, it is very stable in all six complexes systems using PPC. Especially, intra-protease, protease-inhibitor hydrogen bonds are dynamic stabilized in MD simulation. The computed binding free energies of six complexes have a significantly linear correlation with those experiment values and the correlation coefficient is found to be 0.91 in PPC simulation. However, the result from AMBER simulation shows a weaker correlation with the correlation coefficient of −0.51 due to the lack of polarization effect. Detailed binding interactions of W301, inhibitors with PR are further analyzed and discussed. The present study provides important information to quantitative understanding the interaction mechanism of PR-inhibitor and PR-W301 and these data also emphasizes the importance of both the electronic polarization and the bridging water molecule in predicting precisely binding affinities.

Lipid profile of HIV-infected patients in relation to antiretroviral therapy: a review

This study reviewed the lipid profile of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) patients in relation to use of antiretroviral therapy (ART), and its different classes of drugs. A total of 190 articles published in peer-reviewed journals were retrieved from PubMed and LILACS databases; 88 of them met the selection criteria and were included in the review. Patients with HIV/AIDS without ART presented an increase of triglycerides and decreases of total cholesterol, low density lipoprotein (LDL-c), and high density lipoprotein (HDL-c) levels. Distinct ART regimens appear to promote different alterations in lipid metabolism. Protease inhibitors, particularly indinavir and lopinavir, were commonly associated with hypercholesterolemia, high LDL-c, low HDL-c, and hypertriglyceridemia. The protease inhibitor atazanavir is apparently associated with a more advantageous lipid profile. Some nucleoside reverse-transcriptase inhibitors (didanosine, stavudine, and zidovudine) induced lipoatrophy and hypertriglyceridemia, whereas abacavir increased the risk of cardiovascular diseases even in the absence of apparent lipid disorders, and tenofovir resulted in lower levels of cholesterol and triglycerides. Although non-nucleoside reverse-transcriptase inhibitors predisposed to hypertriglyceridemia and hypercholesterolemia, nevirapine was particularly associated with high HDL-c levels, a protective factor against cardiovascular diseases. Therefore, the infection itself, different classes of drugs, and some drugs from the same class of ART appear to exert distinct alterations in lipid metabolism.

Comparison of once-daily versus twice-daily combination antiretroviral therapy in treatment-naive patients: results of AIDS clinical trials group (ACTG) A5073, a 48-week randomized controlled trial

BACKGROUND

Dosing frequency is an important determinant of regimen effectiveness. Methods. To compare efficacy of once-daily (QD) versus twice-daily (BID) antiretroviral therapy, we randomized human immunodeficiency virus (HIV)-positive, treatment-naive patients to lopinavir-ritonavir (LPV/r) administered at a dosage of 400 mg of lopinavir and 100 mg of ritonavir BID (n = 160) or 800 mg of lopinavir and 200 mg of ritonavir QD (n = 161), plus either emtricitabine 200 mg QD and extended-release stavudine at a dosage of 100 mg QD or tenofovir at a dosage of 300 mg QD. Randomization was stratified by screening HIV RNA level <100,000 copies/mL versus > or = 100,000 copies/mL. The primary efficacy end point was sustained virologic response (SVR; defined as reaching and maintaining an HIV RNA level <200 copies/mL) through week 48.

RESULTS

Subjects were 78% male, 33% Hispanic, and 34% black. A total of 82% of subjects completed the study, and 71% continued to receive the initially assigned dosage schedule. The probability of SVR did not differ significantly for the BID versus QD comparison, with an absolute proportional difference of 0.03 (95% confidence interval [CI], -0.07 to 0.12). The comparison depended on the screening RNA stratum (P=.038); in the higher RNA stratum, the probability of SVR was significantly better in the BID arm than in the QD arm: 0.89 (95% CI, 0.79-0.94) versus 0.76 (95% CI, 0.64-0.84), a difference of 0.13 (95% CI, 0.01-0.25). Lopinavir trough plasma concentrations were higher with BID dosing. Adherence to prescribed doses of LPV/r was 90.6% in the QD arm versus 79.9% in the BID arm (P<.001). Conclusions. Although subjects assigned to QD regimens had better adherence, overall treatment outcomes were similar in the QD and BID arms. Subjects with HIV RNA levels > or =100,000 copies/mL had better SVR with BID regimens at 48 weeks, which suggests a possible advantage in this setting for more frequent dosing. Clinical trial registration. ClinicalTrials.gov registration number: NCT00036452.

Insights into drug resistance of mutations D30N and I50V to HIV-1 protease inhibitor TMC-114: free energy calculation and molecular dynamic simulation

The single mutations D30N and I50V are considered as the key residue mutations of the HIV-1 protease drug resistance to inhibitors in clinical use. In this work, molecular dynamics (MD) simulations combined with the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method have been performed to investigate the drug-resistant mechanisms of D30N and I50V to an inhibitor TMC-114. The analyses of absolute binding free energies using the separate trajectory approach suggests that the decrease in the van der Waals energy and electrostatic energy in the gas phase results in the drug resistance of D30N to TMC-114, while for I50V, the decrease in the electrostatic energy mainly drive its drug resistance to TMC-114. Detailed binding free energies between TMC-114 and individual protein residues are computed by using a per-residue basis decomposition method, which provides insights into the inhibitor-protein binding mechanism and also explains the drug-resistant mechanisms of mutations D30N and I50V to TMC-114. The study shows that the loss of the hydrogen bond between TMC-114 and the side chain of Asn30' is the main driving force of the resistance of D30N to TMC-114, and in the case of I50V, the increase in the polar solvation energies between TMC-114 and two residues Val50' and Asp30' definitively drives the resistance of I50V to TMC-114. We expect that this work can provide some helpful insights into the nature of mutational effect and aid the future design of better inhibitors.

Dealing With the Obstacles in Adhering to Highly Active Antiretroviral Therapy

Improving patient adherence to highly active antiretroviral therapy (HAART) is essential to effective treatment and represents a major challenge confronting healthcare providers. Because of their holistic perspective, nurses are uniquely qualified to identify the psychosocial and practical obstacles to full adherence and help patients deal with these problems. Studies have shown that many factors related to the disease, the patient, the provider, and the treatment regimen all play important roles in adopting and maintaining adherent behavior. Therefore, any attempt toward improving adherence should include adherence assessment and an approach that targets the patient, the provider, and the regimen. The availability of antiretroviral agents that are administered once daily and/or are associated with lower toxicity can help to simplify treatment regimens and avoid certain side effects, thereby facilitating greater adherence to highly active antiretroviral therapy.

Role of efflux pumps and metabolising enzymes in drug delivery

The impact of efflux pumps and metabolic enzymes on the therapeutic activity of various drugs has been well established. The presence of efflux pumps on various tissues and tumours has been shown to regulate the intracellular concentration needed to achieve therapeutic activity. The notable members of efflux proteins include P-glycoprotein, multi-drug resistance protein and breast cancer resistance protein. These efflux pumps play a pivotal role not only in extruding xenobiotics but also in maintaining the body's homeostasis by their ubiquitous presence and ability to coordinate among themselves. In this review, the role of efflux pumps in drug delivery and the importance of their tissue distribution is discussed in detail. To improve pharmacokinetic parameters of substrates, various strategies that modulate the activity of efflux proteins are also described. Drug metabolising enzymes mainly include the cytochrome P450 family of enzymes. Extensive drug metabolism due to the this family of enzymes is the leading cause of therapeutic inactivity. Therefore, the role of metabolising enzymes in drug delivery and disposition is extensively discussed in this review. The synergistic relationship between metabolising enzymes and efflux proteins is also described in detail. In summary, this review emphasises the urgent need to make changes in drug discovery and drug delivery as efflux pumps and metabolising enzymes play an important role in drug delivery and disposition.

Protease inhibitor-induced diabetic complications : incidence, management and prevention

Protease inhibitors (PIs) have become a crucial element in the treatment of patients infected with HIV. However, the widespread use of PI therapy has also been associated with a number of metabolic adverse effects, including fat redistribution and hyperglycaemia. The objective of this review is a discussion of the incidence, pathophysiology, management and prevention of PI-associated hyperglycaemia. Initial case reports have been followed by large cross-sectional and cohort studies, which demonstrate that the incidence of PI-induced impaired glucose tolerance, as well as frank diabetes mellitus, is significant and demands attention. Investigations into the pathophysiology behind PI-associated hyperglycaemia have identified an underlying problem of insulin resistance that is presumably caused by both direct PI-induced mechanisms and lipotoxicity. Given this, clinical trials have explored the use of various classes of oral hypoglycaemic agents in the management of PI-induced diabetic complications, and the use of insulin therapy must be considered as well. Newer PI agents are also under development, with the hope of reducing metabolic adverse effects. In the meantime, prevention, in the form of dietary modification, regular physical activity and periodic screening for impaired glucose tolerance, must receive heightened attention in the care plan of patients receiving long-term PI therapy.

Atazanavir trough plasma concentration monitoring in a cohort of HIV-1-positive individuals receiving highly active antiretroviral therapy

OBJECTIVES

Atazanavir is a recently approved HIV protease inhibitor (PI). As with other PIs, careful attention to potential pharmacokinetic drug interactions in clinical practice is necessary. The aim of this study was to assess the clinical associations with plasma atazanavir concentrations in HIV-positive individuals.

METHODS

Individuals established on an atazanavir-containing regimen, completed an interviewer-administered questionnaire recording atazanavir dosing characteristics, concomitant medication use and adherence. After completion, plasma atazanavir concentrations were measured.

RESULTS

Of 100 individuals, mean trough plasma atazanavir concentrations (mug/L) were 282 (95% CI 95-468, n = 19) and 774 (95% CI 646-902, n = 81) in those on non- and ritonavir-boosted atazanavir regimens, respectively. Eighty-five individuals had HIV RNA <50 copies/mL. Seven individuals had atazanavir plasma concentrations below the assay limit of detection (<50 microg/L), all of whom had undetectable plasma HIV RNA. In a multivariate analysis, nevirapine use was associated with significantly lower trough atazanavir concentrations (P = 0.011) and lopinavir/ritonavir use with higher trough atazanavir concentrations (P = 0.032). Dosing characteristics (including food taken), concomitant medications (including drugs used for dyspepsia) and HIV RNA were not significantly associated with trough atazanavir concentrations.

CONCLUSIONS

In this cohort, despite the wide inter-individual variability of atazanavir trough concentrations, no significant association with dosing characteristics, concomitant medication (with the exception of nevirapine and lopinavir/ritonavir) or virological response was observed. Further work is needed to assess the optimal dosing regimen when using atazanavir with nevirapine.

Symmetric fluoro-substituted diol-based HIV protease inhibitors. Ortho-fluorinated and meta-fluorinated P1/P1'-benzyloxy side groups significantly improve the antiviral activity and preserve binding efficacy

HIV-1 protease is a pivotal enzyme in the later stages of the viral life cycle which is responsible for the processing and maturation of the virus particle into an infectious virion. As such, HIV-1 protease has become an important target for the treatment of AIDS, and efficient drugs have been developed. However, negative side effects and fast emerging resistance to the current drugs have necessitated the development of novel chemical entities in order to exploit different pharmacokinetic properties as well as new interaction patterns. We have used X-ray crystallography to decipher the structure-activity relationship of fluoro-substitution as a strategy to improve the antiviral activity and the protease inhibition of C2-symmetric diol-based inhibitors. In total we present six protease-inhibitor complexes at 1.8-2.3 A resolution, which have been structurally characterized with respect to their antiviral and inhibitory activities, in order to evaluate the effects of different fluoro-substitutions. These C2-symmetric inhibitors comprise mono- and difluoro-substituted benzyloxy side groups in P1/P1' and indanoleamine side groups in P2/P2'. The ortho- and meta-fluorinated P1/P1'-benzyloxy side groups proved to have the most cytopathogenic effects compared with the nonsubstituted analog and related C2-symmetric diol-based inhibitors. The different fluoro-substitutions are well accommodated in the protease S1/S1' subsites, as observed by an increase in favorable Van der Waals contacts and surface area buried by the inhibitors. These data will be used in the development of potent inhibitors with different pharmacokinetic profiles towards resistant protease mutants.

The relationship between nevirapine plasma concentrations and abnormal liver function tests

Abnormal liver function tests are frequently observed in HIV-infected individuals receiving nevirapine (NVP). Here we investigate the relationship between total and unbound plasma concentrations of NVP and the liver enzymes alanine aminotransferase (ALT) and gamma-glutamyl transferase (gammaGT). HIV-infected individuals [n = 85, 22 female, 34 hepatitis C or B virus (HCV or HBV(+))] receiving NVP (200 mg bd; median duration 66 weeks, range 3-189) and two nucleoside reverse transcriptase inhibitors (NRTIs) were enrolled into this study. Blood samples were taken at C(trough) (12 hr postdose) for measurement of NVP and liver function tests (ALT and gammaGT). Plasma protein bound and unbound drug was separated using ultrafiltration and NVP concentrations quantified using HPLC-MS/MS. A linear relationship was observed between total and unbound NVP C(trough) (r(2) = 0.77, p < 0.0001). Patients with elevated ALT (>37 IU/liter; n = 31) had higher NVP unbound C(trough) than those with ALT within the normal range (median 2268 vs. 1694 ng/ml, p = 0.04) but there was no difference in total C(trough). Logistic regression revealed no association between higher NVP C(trough) and ALT elevations. Significantly higher NVP total and unbound C(trough) were observed in patients with increased gammaGT (>40 IU/liter; n = 63; total 6747 vs. 4530 ng/ml, p = 0.001; unbound 2113 vs. 1557 ng/ml, p = 0.03). Significantly higher unbound NVP C(trough) was observed in HCV/HBV(+) (median 2275 vs. 1726 ng/ml, p = 0.02) and on bivariate analysis, higher NVP C(trough) was associated with HCV/HBV coinfection (chi(2) = 4.228; p = 0.04). Overall we found no strong association between NVP concentrations and hepatotoxicity. Although in this study NVP was well tolerated in HCV/HBV coinfected patients, higher plasma concentrations were observed.

Saquinavir: a review of its use in boosted regimens for treating HIV infection

Protease inhibitor boosting involves concurrent administration of a protease inhibitor, such as saquinavir, plus a potent inhibitor of cytochrome P450 (CYP) 3A4, usually ritonavir in subtherapeutic doses. Since protease inhibitors are extensively metabolised by CYP3A4, this results in a marked increase in systemic exposure of saquinavir or other protease inhibitors boosted by ritonavir. As with traditional protease inhibitor regimens, boosted regimens are typically used in combination with nucleoside reverse transcriptase inhibitors (NRTIs). In protease inhibitor-experienced and -naive patients with HIV infection, twice-daily and once-daily boosted saquinavir regimens achieved good rates of viral suppression, improved CD4+ cell counts and were generally well tolerated in clinical trials. Encouraging results have also been reported in a number of small studies in heavily pretreated HIV-infected patients who received salvage therapy comprising double-boosted regimens of saquinavir plus lopinavir with subtherapeutic doses of ritonavir, along with other agents. The largest clinical trials have been multicentre, randomised comparisons of twice-daily boosted saquinavir versus twice-daily boosted indinavir (MaxCmin1) or lopinavir (MaxCmin2) regimens. In the MaxCmin1 study, >90% of patients in both groups had an undetectable viral load (<400 copies/mL) after 48 weeks of therapy in the on-treatment analysis. However, viral suppression was achieved in significantly more saquinavir than indinavir recipients in the intention-to-treat analysis, which appeared to be due to the significantly greater percentage of patients in the indinavir group who switched from randomised therapy because of adverse events. Interim 24-week results of the MaxCmin2 trial indicate that 90% of patients in both groups combined had plasma HIV RNA levels <400 copies/mL; final results at 48 weeks will report data separately for the boosted regimens of saquinavir and lopinavir.

CONCLUSION

Boosted protease inhibitor regimens (including two NRTIs) are recommended as a first-line option in current HIV treatment guidelines and are used extensively in clinical practice. The convenient administration schedule and good pharmacokinetic profile associated with boosted saquinavir regimens have the potential to increase adherence to therapy and improve antiretroviral effects through increased drug exposure. Twice-daily boosted saquinavir is one of the most extensively evaluated boosted protease inhibitor regimens and has been shown to have good efficacy on surrogate markers of HIV disease as well as significant tolerability advantages over boosted indinavir. Once-daily boosted saquinavir regimens may be most suitable for HIV-infected patients with busy lifestyles and those who would benefit from directly observed therapy.