Pharmacokinetic interaction between nelfinavir and pravastatin in HIV-seronegative volunteers: ACTG Study A5108

Pathophysiology and Clinical Management of Dyslipidemia in People Living with HIV: Sailing through Rough Seas

Infections with human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) represent one of the greatest health burdens worldwide. The complex pathophysiological pathways that link highly active antiretroviral therapy (HAART) and HIV infection per se with dyslipidemia make the management of lipid disorders and the subsequent increase in cardiovascular risk essential for the treatment of people living with HIV (PLHIV). Amongst HAART regimens, darunavir and atazanavir, tenofovir disoproxil fumarate, nevirapine, rilpivirine, and especially integrase inhibitors have demonstrated the most favorable lipid profile, emerging as sustainable options in HAART substitution. To this day, statins remain the cornerstone pharmacotherapy for dyslipidemia in PLHIV, although important drug-drug interactions with different HAART agents should be taken into account upon treatment initiation. For those intolerant or not meeting therapeutic goals, the addition of ezetimibe, PCSK9, bempedoic acid, fibrates, or fish oils should also be considered. This review summarizes the current literature on the multifactorial etiology and intricate pathophysiology of hyperlipidemia in PLHIV, with an emphasis on the role of different HAART agents, while also providing valuable insights into potential switching strategies and therapeutic options.

Prediction of the Pharmacokinetics of Pravastatin as an OATP Substrate Using Plateable Human Hepatocytes With Human Plasma Data and PBPK Modeling

Plateable human hepatocytes with human plasma were utilized to generate the uptake transporter kinetic data for pravastatin, an organic anion-transporting polypeptide (OATP) transporter substrate. The active hepatic uptake of pravastatin was determined with a J_max value of 134.4 pmol/min/million cells and K_m of 76.77 µM in plateable human hepatocytes with human plasma. The physiologically-based pharmacokinetic (PBPK) model with incorporation of these in vitro kinetic data successfully simulated the i.v. pharmacokinetic profile of pravastatin without applying scaling factor (the mean predicted area under the curve (AUC) is within 1.5-fold of the observed). Furthermore, the PBPK model also adequately described the oral plasma concentration-time profiles of pravastatin at different dose levels. The current investigation demonstrates an approach allowing us to build upon the translation of in vitro OATP uptake transporter data to in vivo, with a hope of utilizing the in vitro data for the prospective human pharmacokinetic (PK) prediction.

Lack of pharmacokinetic interactions between pitavastatin and efavirenz or darunavir/ritonavir

BACKGROUND

The drug-drug interactions between pitavastatin and darunavir/ritonavir (DRV/r) as well as pitavastatin and efavirenz (EFV) were examined in an open-label, parallel-arm, pharmacokinetic (PK) study in HIV-uninfected healthy volunteers.

METHODS

Subjects received a pitavastatin dose of 2 mg for 4 days, followed by either EFV 600 mg (n = 14) or DRV/r 800/100 mg (n = 14) daily for 10 days, and pitavastatin 2 mg coadministered with EFV 600 mg or DRV/r 800/100 mg for 4 days. Full PK profiles were determined for pitavastatin and its lactone metabolite on days 4 and 18 and for EFV or DRV on days 14 and 18.

RESULTS

In the EFV arm, the geometric mean area under the concentration time curve (AUC0-τ) and Cmax of pitavastatin were 85.3 ng·h·mL and 15.6 ng/mL, respectively, when given alone, versus 76 ng·h·mL and 18.8 ng/mL when coadministered with EFV. The geometric mean ratio for pitavastatin with EFV versus alone was 0.89 [90% confidence interval (CI): 0.73 to 1.09] for AUC0-τ and 1.20 (90% CI: 0.79 to 1.83) for Cmax. In the DRV/r arm, AUC0-τ and Cmax were 62.8 ng·h·mL and 24.0 ng/mL, respectively, when pitavastatin was administered alone, versus 56.9 ng·h·mL and 23.2 ng/mL when coadministered with DRV/r. The geometric mean ratio for pitavastatin with DRV/r versus alone was 0.91 (90% CI: 0.78 to 1.06) for AUC0-τ and 0.93 (90% CI: 0.72 to 1.19) for Cmax.

CONCLUSIONS

There were no significant PK interactions between pitavastatin and EFV or DRV/r. No significant safety issues or lipid changes were noted.

Drug-drug interactions between HMG-CoA reductase inhibitors (statins) and antiviral protease inhibitors

The HMG-CoA reductase inhibitors are a class of drugs also known as statins. These drugs are effective and widely prescribed for the treatment of hypercholesterolemia and prevention of cardiovascular morbidity and mortality. Seven statins are currently available: atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin and simvastatin. Although these drugs are generally well tolerated, skeletal muscle abnormalities from myalgia to severe lethal rhabdomyolysis can occur. Factors that increase statin concentrations such as drug-drug interactions can increase the risk of these adverse events. Drug-drug interactions are dependent on statins' pharmacokinetic profile: simvastatin, lovastatin and atorvastatin are metabolized through cytochrome P450 (CYP) 3A, while the metabolism of the other statins is independent of this CYP. All statins are substrate of organic anion transporter polypeptide 1B1, an uptake transporter expressed in hepatocyte membrane that may also explain some drug-drug interactions. Many HIV-infected patients have dyslipidemia and comorbidities that may require statin treatment. HIV-protease inhibitors (HIV PIs) are part of recommended antiretroviral treatment in combination with two reverse transcriptase inhibitors. All HIV PIs except nelfinavir are coadministered with a low dose of ritonavir, a potent CYP3A inhibitor to improve their pharmacokinetic properties. Cobicistat is a new potent CYP3A inhibitor that is combined with elvitegravir and will be combined with HIV-PIs in the future. The HCV-PIs boceprevir and telaprevir are both, to different extents, inhibitors of CYP3A. This review summarizes the pharmacokinetic properties of statins and PIs with emphasis on their metabolic pathways explaining clinically important drug-drug interactions. Simvastatin and lovastatin metabolized through CYP3A have the highest potency for drug-drug interaction with potent CYP3A inhibitors such as ritonavir- or cobicistat-boosted HIV-PI or the hepatitis C virus (HCV) PI, telaprevir or boceprevir, and therefore their coadministration is contraindicated. Atorvastatin is also a CYP3A substrate, but less potent drug-drug interactions have been reported with CYP3A inhibitors. Non-CYP3A-dependent statin concentrations are also affected although to a lesser extent when coadministered with HIV or HCV PIs, mainly through interaction with OATP1B1, and treatment should start with the lowest available statin dose. Effectiveness and occurrence of adverse effects should be monitored at regular time intervals.

Influence of SLCO1B1 polymorphisms on the drug-drug interaction between darunavir/ritonavir and pravastatin

The authors investigated whether SLCO1B1 polymorphisms contribute to variability in pravastatin pharmacokinetics when pravastatin is administered alone versus with darunavir/ritonavir. HIV-negative healthy participants were prospectively enrolled on the basis of SLCO1B1 diplotype: group 1 (*1A/*1A, n = 9); group 2 (*1A/*1B, n = 10; or *1B/*1B, n = 2); and group 3 (*1A/*15, n = 1; *1B/*15, n = 5; or *1B/*17, n = 1). Participants received pravastatin (40 mg) daily on days 1 through 4, washout on days 5 through 11, darunavir/ritonavir (600/100 mg) twice daily on days 12 through 18, with pravastatin 40 mg added back on days 15 through 18. Pharmacokinetic studies were conducted on day 4 (pravastatin alone) and day 18 (pravastatin + darunavir/ritonavir). Pravastatin area under the plasma concentration-time curve (AUC(tau)) was 21% higher during administration with darunavir/ritonavir compared with pravastatin alone; however, this difference was not statistically significant (P = .11). Group 3 variants had 96% higher pravastatin AUC(tau) on day 4 and 113% higher pravastatin AUC(tau) on day 18 compared with group 1. The relative change in pravastatin pharmacokinetics was largest in group 3 but did not differ significantly between diplotype groups. In sum, the influence of SLCO1B1*15 and *17 haplotypes on pravastatin pharmacokinetics was maintained in the presence of darunavir/ritonavir. Because OATP1B1 inhibition would be expected to be greater in carriers of normal or high-functioning SLCO1B1 haplotypes, these findings suggest that darunavir/ritonavir is not a potent inhibitor of OATP1B1-mediated pravastatin transport in vivo.

Management of dyslipidemia in HIV-infected patients

Antiretroviral therapy has dramatically increased survival for HIV-infected individuals. As this population lives longer, coronary heart disease has become an important comorbid condition. Dyslipidemia in HIV-infected individuals is a complex condition, with multiple contributing factors including the HIV virus itself, individual genetic characteristics and antiretroviral therapy-induced metabolic changes. Effective management of dyslipidemia in this population is essential to reduce cardiovascular risk but presents multiple challenges due to interactions between antiretroviral therapy agents and lipid-lowering medications.

Lipodystrophy: pathophysiology and advances in treatment

Lipodystrophy is a medical condition characterized by complete or partial loss of adipose tissue. Not infrequently, lipodystrophy occurs in combination with pathological accumulation of adipose tissue at distinct anatomical sites. Patients with lipodystrophy exhibit numerous metabolic complications, which indicate the importance of adipose tissue as an active endocrine organ. Not only the total amount but also the appropriate distribution of adipose tissue depots contribute to the metabolic state. Genetic and molecular research has improved our understanding of the mechanisms underlying lipodystrophy. Circulating levels of hormones secreted by the adipose tissue, such as leptin and adiponectin, are greatly reduced in distinct subpopulations of patients with lipodystrophy. This finding rationalizes the use of these adipokines or of agents that increase their circulating levels, such as peroxisome proliferator-activated receptor γ (PPARγ) agonists, for therapeutic purposes. Other novel therapeutic approaches, including the use of growth hormone and growth-hormone-releasing factors, are also being studied as potential additions to the therapeutic armamentarium. New insights gained from research and clinical trials could potentially revolutionize the management of this difficult-to-treat condition.

Organic anion transporting polypeptide 1B1: a genetically polymorphic transporter of major importance for hepatic drug uptake

The importance of membrane transporters for drug pharmacokinetics has been increasingly recognized during the last decade. Organic anion transporting polypeptide 1B1 (OATP1B1) is a genetically polymorphic influx transporter expressed on the sinusoidal membrane of human hepatocytes, and it mediates the hepatic uptake of many endogenous compounds and xenobiotics. Recent studies have demonstrated that OATP1B1 plays a major, clinically important role in the hepatic uptake of many drugs. A common single-nucleotide variation (coding DNA c.521T>C, protein p.V174A, rs4149056) in the SLCO1B1 gene encoding OATP1B1 decreases the transporting activity of OATP1B1, resulting in markedly increased plasma concentrations of, for example, many statins, particularly of active simvastatin acid. The variant thereby enhances the risk of statin-induced myopathy and decreases the therapeutic indexes of statins. However, the effect of the SLCO1B1 c.521T>C variant is different on different statins. The same variant also markedly affects the pharmacokinetics of several other drugs. Furthermore, certain SLCO1B1 variants associated with an enhanced clearance of methotrexate increase the risk of gastrointestinal toxicity by methotrexate in the treatment of children with acute lymphoblastic leukemia. Certain drugs (e.g., cyclosporine) potently inhibit OATP1B1, causing clinically significant drug interactions. Thus, OATP1B1 plays a major role in the hepatic uptake of drugs, and genetic variants and drug interactions affecting OATP1B1 activity are important determinants of individual drug responses. In this article, we review the current knowledge about the expression, function, substrate characteristics, and pharmacogenetics of OATP1B1 as well as its role in drug interactions, in parts comparing with those of other hepatocyte-expressed organic anion transporting polypeptides, OATP1B3 and OATP2B1.

Comparative Effectiveness and Toxicity of Statins Among HIV-Infected Patients

BACKGROUND

dyslipidemia is common and is often treated with 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (statins). Little is known about the comparative effectiveness of statins among human immunodeficiency virus (HIV)-infected patients. This study compared the effectiveness and toxicity of statins among HIV-infected patients in clinical care.

METHODS

we conducted a retrospective cohort study of patients starting their initial statin medications at 2 large HIV clinics (N = 700). The primary observation was change in lipid levels during statin therapy. Secondary observations included whether individualized National Cholesterol Education Program (NCEP) goals for low density lipoprotein cholesterol (LDL-C) and non-high density lipoprotein cholesterol (non-HDL-C) levels were reached, and toxicity rates. We used linear regression to examine change in lipid levels, controlling for baseline lipid values and demographic and clinical characteristics. We conducted secondary analyses using propensity scores to address confounding by indication.

RESULTS

the most commonly prescribed statins were atorvastatin (N = 303), pravastatin (N = 280), and rosuvastatin (N = 95). One year after starting a statin therapy, patients who received atorvastatin or rosuvastatin had significantly greater decreases in total cholesterol, LDL-C, and non-HDL-C than patients on pravastatin. The likelihood of reaching NCEP goals for LDL-C levels was higher with the use of rosuvastatin (OR 2.1; P = .03) and atorvastatin (odds ratio [OR], 2.1; P = .001) compared with that of pravastatin. The likelihood of reaching NCEP goals for non-HDL-C levels was higher for rosuvastatin (OR 2.3; P = .045) but not atorvastatin (OR, 1.5; P = .1) compared with pravastatin. Toxicity rates were similar for all 3 statins: 7.3% for atorvastatin, 6.1% for pravastatin, and 5.3% for rosuvastatin.

CONCLUSIONS

our findings suggest that atorvastatin and rosuvastatin are preferable to pravastatin for treatment of HIV-infected patients with dyslipidemia, due to greater declines in total cholesterol, LDL-C, and non-HDL-C, with similar lower toxicity rates.

Dyslipidemia and its Treatment in HIV Infection

HIV-infected patients have metabolic abnormalities that put them at increased risk of cardiovascular disease (CVD), including abnormalities associated with HIV infection itself, antiretroviral treatment, restoration to health, and body composition changes. The 2 major components of dyslipidemia in HIV-infected patients are hypertriglyceridemia and reduction in high-density lipoprotein (HDL) cholesterol (with likely altered function of HDL cholesterol); these abnormalities contribute to increased atherosclerotic risk. Adverse effects of antiretroviral drugs on lipids are not class specific but rather are associated with particular drugs. Thus, practitioners need to be cognizant of the risks of metabolic abnormalities posed by individual drugs. HIV infection increases CVD risk independent of the effects of traditional risk factors. The relative risk of CVD in HIV-infected patients has decreased in recent years with increasing use of lipid-lowering therapy. However, use of lipid-lowering therapy is complicated by numerous potential drug interactions with antiretroviral drugs that practitioners need to consider when prescribing lipid-lowering therapy. This article summarizes a presentation made by Carl Grunfeld, MD, PhD, at the International AIDS Society-USA continuing medical education program in Los Angeles in March 2010. The original presentation is available as a Webcast at www.iasusa.org.

Comorbidities and challenges affecting African Americans with HIV infection

The significant disparities in health outcomes that exist among racial minorities in the United States are clearly evident in the HIV epidemic. HIV disproportionately affects minorities, African Americans in particular. Current treatment of HIV/AIDS is complicated by medical problems such as hepatitis, diabetes and dyslipidemia, which also disproportionately affect African Americans and can significantly impact the complexity of clinical care. In addition, untreated psychological problems such as depression and societal barriers to adequate medical care may decrease treatment adherence and increase HIV-related morbidity and mortality among African Americans. Consideration of these issues by healthcare providers is necessary to optimize care and improve treatment outcomes for African Americans with HIV infection.

Successful strategy to improve the specificity of electronic statin-drug interaction alerts

PURPOSE

A considerable weakness of current clinical decision support systems managing drug-drug interactions (DDI) is the high incidence of inappropriate alerts. Because DDI-induced, dose-dependent adverse events can be prevented by dosage adjustment, corresponding DDI alerts should only be issued if dosages exceed safe limits. We have designed a logical framework for a DDI alert-system that considers prescribed dosage and retrospectively evaluates the impact on the frequency of statin-drug interaction alerts.

METHODS

Upper statin dose limits were extracted from the drug label (SPC) (20 statin-drug combinations) or clinical trials specifying the extent of the pharmacokinetic interaction (43 statin-drug combinations). We retrospectively assessed electronic DDI alerts and compared the number of standard alerts to alerts that took dosage into account.

RESULTS

From among 2457 electronic prescriptions, we identified 73 high-risk statin-drug pairs. Of these, SPC dosage information classified 19 warnings as inappropriate. Data from pharmacokinetic trials took quantitative dosage information more often into consideration and classified 40 warnings as inappropriate. This is a significant reduction in the number of alerts by 55% compared to SPC-based information (26%; p < 0.001).

CONCLUSION

This retrospective study of pharmacokinetic statin interactions demonstrates that more than half of the DDI alerts that presented in a clinical decision support system were inappropriate if DDI-specific upper dose limits are not considered.

Lipid management in patients who have HIV and are receiving HIV therapy

Dyslipidemia now is recognized as a significant potential adverse event in HIV-infected patients who are receiving antiretroviral therapy. HIV-infected persons who have hyperlipidemia should be managed similarly to those without HIV infection in accordance with the National Cholesterol Education Program. Providers must treat the HIV infection first; if dyslipidemia develops, patients should be prescribed lipid-lowering therapies or should consider modifying their current antiretroviral therapy, if indicated. Evidence for these two strategies is discussed.

Effects of atazanavir/ritonavir or fosamprenavir/ritonavir on the pharmacokinetics of rosuvastatin

BACKGROUND

Rosuvastatin (RSV) is a potent statin with a lower potential for drug interactions. However, recent data have revealed unexpected increases in RSV concentrations with lopinavir/ritonavir. The objective is to study the pharmacokinetic interaction of RSV with atazanavir/ritonavir (ATV/RTV) or fosamprenavir/ritonavir (FPV/RTV).

METHODS

In a prospective pharmacokinetic drug interaction study, six HIV-seronegative, healthy adult volunteers received single 10-mg doses of RSV at baseline and after 6 days of ATV/RTV and FPV/RTV, with 6-day washout periods. Plasma concentrations of RSV and its metabolites, N-desmethyl-RSV and RSV-lactone, were measured by using a internally validated tandem mass spectrometric (LC-MS/MS) method over 24 hours.

RESULTS

Compared to baseline, the area under the plasma concentration-time curve (AUC 0-24h) and maximum plasma concentration (Cmax) of RSV increased by 213% and 600%, respectively, and the time to reach Cmax was shorter (1.75 h vs. 2.91 h) when given with ATV/RTV (P < 0.05). However, coadministration with FPV/RTV did not significantly affect the pharmacokinetics of RSV. The AUC 0-24h of N-desmethyl-RSV was not significantly affected by either combinations, but that of RSV-lactone increased (P < 0.05) by 61% and 76% after coadministration with ATV/RTV and FPV/RTV, respectively.

CONCLUSION

ATV/RTV significantly increases the plasma concentrations of rosuvastatin, most likely by increasing rosuvastatin's oral bioavailability. Dose limitations of RSV with ATV/RTV may be needed.

Potential for new antiretrovirals to address unmet needs in the management of HIV-1 infection

Despite the myriad advances in antiretroviral therapy since the original highly active antiretroviral therapy regimens were developed, there remain numerous important and pressing unmet needs that, if addressed, would substantially improve the quality of life and longevity of HIV-infected patients. The most achievable goals of antiretroviral (ARV) therapy in the near future are likely to be continued reduction in HIV-related morbidity and mortality; improved quality of life; and restoration and preservation of immune function: all of which are most effectively achieved through sustained suppression of HIV-1 RNA. The ability to achieve long-term viral load reduction will require new ARVs with few, manageable toxicities, and medications that are convenient to adhere to, with few drug interactions. This is particularly true for the large number of highly treatment-experienced patients in whom HIV has developed resistance to one or more ARVs. Development of therapies that allow convenient dosing schedules, that do not necessitate strict adherence to meal-related timing restrictions, and that remain active in the face of resistance mutations is paramount, and remains a significant unmet need. Of the large number of ARVs currently in development, this article focuses on three agents recently approved that have shown particular promise in addressing some of these unmet needs: the novel non-nucleoside reverse transcriptase inhibitor etravirine; the CCR5 antagonist maraviroc; and the integrase inhibitor raltegravir.

Antiretroviral therapy and the human immunodeficiency virus--improved survival but at what cost?

Patients infected with human immunodeficiency virus are living longer since the introduction of combination antiretroviral therapy more than a decade ago - but at what cost? Highly active antiretroviral therapy has been associated with lipodystrophy and associated metabolic derangements such as dyslipidaemia, insulin resistance and diabetes. These complications are likely to contribute to an increased risk of premature and accelerated atherosclerosis with growing concern about potential cardiovascular consequences.

Comparison of direct and indirect measurement of LDL-C in HIV-infected individuals: ACTG 5087

BACKGROUND

Hypertriglyceridemia is common in HIV-infected individuals on antiretroviral therapy. Triglyceride (TG) levels >400 mg/dL interfere with the accurate determination of low-density lipoproteins (LDL-C) by the Friedewald equation, making it difficult to assess coronary heart disease risk.

OBJECTIVE

The objective of this study is to compare the agreement of the direct LDL-C assay and the Friedewald equation with a reference ultracentrifugation method in the estimation of LDL-C concentrations.

METHOD

Samples from ACTG 5087 were assayed by ultracentrifugation and a direct enzymatic assay and calculated using the Friedewald equation.

RESULTS

In subjects with TG <400 mg/dL (n = 271), 90% of the direct LDL-C values and Friedewald calculations were within 30 mg/dL and 32 mg/dL of the ultracentrifugation values, respectively. With TG > or = 400 mg/dL (n = 186), 90% of the direct assay and Friedewald observations were within 68 mg/dL and 120 mg/dL of the ultracentrifugation results, respectively. Only 27% of the LDL-C values were within 15 mg/dL of the ultracentrifugation LDL-C results for direct assay and 16.3% for the Friedewald equation.

CONCLUSION

The direct LDL-C assay and the calculated LDL-C values did not display adequate agreement with the reference ultracentrifugation method. In subjects with TG >400 mg/dL, the direct assay overestimates the actual LDL-C whereas the Friedewald calculation underestimates the actual LDL. Clinical usage of these methods may lead to misclassification of the severity of dyslipidemia, resulting in improper management.