Abnormalities of lipid metabolism are common complications of HIV and certain classes of antiretroviral therapy used to treat the disease.1 As a result, lipid-lowering drugs, particularly inhibitors of 3-hydroxy-3-methylglutaryl–coenzyme A reductase (statins), are often used in persons with HIV infection and dyslipidemia. Because many statins and their metabolites are extensively metabolized by the cytochrome P450 (CYP) system,2 and all of the currently available protease inhibitors (PIs) both inhibit and induce numerous CYP enzymes,3 there is a clear potential for drug–drug interactions (DDIs) between many statins and PIs. Studies have demonstrated that the extent of the interaction varies based on the properties of the statin.3
Pitavastatin is an oral statin recently approved by the Food and Drug Administration (FDA) for the treatment of primary hyperlipidemia and mixed dyslipidemia, demonstrating a mean percent reduction in low-density lipoprotein cholesterol up to 45% and improvement in other lipid parameters.4,5 The principal route of pitavastatin metabolism is glucuronidation with subsequent conversion to pitavastatin lactone.6 Pitavastatin is minimally metabolized by the CYP system, marginally by CYP2C9, and to a lesser extent CYP2C8,2 and therefore, may have a reduced potential for CYP-mediated drug interactions.7 Hepatic uptake of pitavastatin is facilitated by several organic anion-transporting polypeptides (OATP), mainly OATP1B1.8 Drug interactions observed with pitavastatin are thought to be due to mechanisms other than interaction with CYP enzymes.9
Lopinavir/ritonavir is a fixed-dose PI combination used for the treatment of HIV-1 infection. Lopinavir is extensively metabolized by the hepatic enzymes CYP3A4 and CYP3A5.10 Of particular importance, the ritonavir component of lopinavir/ritonavir is a potent inhibitor of CYP3A and CYP2D6,11 an inducer of other hepatic enzyme systems, and is transported by OATP1B1.12 As combination therapy, ritonavir is used to enhance the systemic exposure of lopinavir. Based on their metabolism, coadministration of lopinavir/ritonavir with other drugs that share these uptake and biotransformation pathways, including many statins, can potentially cause clinically significant changes in serum drug levels. As other statins have demonstrated significant interactions with lopinavir/ritonavir and in some cases have led to reduced dosage or contraindication,13 there was a postapproval FDA requirement to evaluate the interaction between pitavastatin and lopinavir/ritonavir when coadministered.
The primary objective of the study was to investigate the pharmacokinetic (PK) interaction of lopinavir/ritonavir 400 mg/100 mg twice daily on the PK of pitavastatin 4 mg, the maximum daily dose. The secondary objectives of the study were to investigate the effect on the safety of pitavastatin 4 mg by the addition of lopinavir/ritonavir 400 mg/100 mg twice daily and to investigate the PK interaction of pitavastatin 4 mg on the PK of lopinavir/ritonavir 400 mg/100 mg twice daily.
This was a phase 4, single-center, open-label, fixed-sequence, 2-way DDI study to determine the effect of lopinavir/ritonavir on the PK of pitavastatin and to determine the effect of pitavastatin on the PK of the lopinavir and ritonavir. Healthy adults between 18 and 45 years of age, inclusive, with a body mass index of 18–30 kg/m2, inclusive, were enrolled into the study. Eligibility was based on medical history, physical examination, clinical laboratory tests, and electrocardiogram (ECG). All female subjects were required to have a negative serum pregnancy test at screening and check-in. Use of prescribed or over-the-counter medications other than vitamin supplements or acetaminophen and use of any known inhibitors or inducers of CYP2C9, CYP3A4, or OATP1B1 was prohibited within 30 days before the first dose of study drug. Medications other than pitavastatin and lopinavir/ritonavir were not permitted during the study.
The study was conducted according to the principles in the Declaration of Helsinki and Guidelines for Good Clinical Practice at a single study site from December 2009 to February 2010. The protocol was approved by an independent institutional review board for the study site. All subjects provided written informed consent before participating in the study. Subjects were restricted to the study site for the 25 days of the study. Subjects entered the clinical unit on day1 before receiving the first dose of study drug and were discharged on day 25.
On day 1 through day 5 and day 20 through day 24, each subject received a once-daily oral-dose tablet form of pitavastatin 4 mg in the morning. On day 9 through day 24, each subject received a twice-daily oral dose of two 200-mg/50-mg lopinavir/ritonavir tablets (total dose of 400 mg and 100 mg of lopinavir and ritonavir, respectively; twice daily) in the morning and 12 hours later in the evening. Morning doses followed an 8-hour fast, whereas evening doses followed a 6-hour fast. All dosing was followed by a 0.5-hour fast except on days 5, 19, and 24 when a 4-hour fast after morning dosing was observed.
Study drugs were administered with water and subjects remained upright for 2 hours after dosing. Standard meals were provided to subjects during confinement to the clinical unit. All possible attempts were made to keep meals identical on PK sampling days (days 5, 19, and 24). The consumption of alcohol, grapefruit, fruit juice (including grapefruit, orange, and apple), and caffeine was prohibited throughout the study.
Pitavastatin was obtained from Patheon Inc (Cincinnati, OH) as tablets in 4-mg dose strength. Lopinavir/ritonavir was obtained commercially as KALETRA (Abbott Laboratories, North Chicago, IL), as tablets containing 200 mg of lopinavir and 50 mg of ritonavir.
Blood Samples for PK Assessments
Blood samples for assessment of plasma concentration of pitavastatin and its lactone metabolite were obtained predose and at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10, 12, 16, and 24 hours postmorning dose on day 5 and day 24. Venous blood was collected in 10-mL tubes with EDTA as the anticoagulant, taking precautions not to expose the sample to light and/or high temperatures. Within 30 minutes of collection, aliquots of plasma were stored at approximately –70°C. Samples were analyzed for pitavastatin and the inactive pitavastatin lactone at ADME Bioanalyses (Vergeze, France) using a validated liquid chromatography with tandem mass spectrometric detection method (LC-MS/MS). The method involved a liquid–liquid extraction with tert-butyl methyl ether followed by a LC-MS/MS analysis of the extracts. For both analytes, the lower limit of quantification was 1 ng/mL, and the upper limit of quantification was 200 ng/mL. During validation for pitavastatin and pitavastatin lactone, the intra-assay accuracy (percent relative error) ranged from 91.0% to 101.1% and from 92.8% to 96.5%, respectively; the intra-assay precision (percent relative SD) ranged from 2.5% to 2.9% and from 2.2% to 2.4%, respectively.
Blood samples for assessment of plasma concentration of lopinavir/ritonavir were obtained predose and at 1, 2, 3, 4, 5, 6, 8, and 12 hours postmorning dose on day 19 and day 24. Venous blood was collected in 4-mL sodium heparin tubes. Within 30 minutes of collection, aliquots of plasma were stored at approximately –70°C. Samples were analyzed for lopinavir and ritonavir at Covance Laboratories Inc (Madison, WI), using a validated LC-MS/MS detection method. Lopinavir and ritonavir were extracted from human plasma using liquid–liquid extraction. After evaporation under nitrogen, the residue was reconstituted and analyzed using LC-MS/MS. The lower limits of quantification were 10 ng/mL and 20 ng/mL, and the upper limits of quantification were 2000 ng/mL and 20000 ng/mL for ritonavir and lopinavir, respectively. During validation for ritonavir and lopinavir, the intra-assay accuracy (percent relative error) ranged from 96.0% to 100.4% and from 104.2% to 112.9%, respectively; the intra-assay precision (percent relative SD) ranged from 2.5% to 7.4% and from 5.1% to 10.4%, respectively.
Primary PK Variables
Plasma samples collected on day 5 and day 24 were assayed for concentrations of pitavastatin and its inactive lactone metabolite, whereas plasma samples collected on days 19 and 24 were assayed for concentrations of lopinavir and ritonavir. The concentration data were used to calculate steady-state plasma PK parameters for pitavastatin, the lactone metabolite of pitavastatin, lopinavir, and ritonavir. PK parameters included area under the plasma concentration–time curve extrapolated from time 0 to infinity (AUC0–inf), area under the plasma concentration–time curve from time 0 to the time of the last measurable concentration (τ) using the linear trapezoidal rule (AUC0–τ), maximum observed plasma concentration (Cmax), and time to achieve maximum plasma concentration (Tmax). All PK parameters were calculated using actual sampling times rather than scheduled sampling times, and modeled as appropriate using WinNonlin professional software Version 5.1.1 or higher (Pharsight Corporation, Mountain View, CA). Summary statistics including mean, SD, coefficient of variation, and geometric mean were calculated for all PK measures.
Statistical Analysis of PK Data
All analyses were performed using SAS software, Version 9.1.3 or higher (SAS Institute Inc, Cary, NC). Values that were below the lower limits of quantification (BLQ) were set equal to 0 for the summary statistics. For calculation of PK parameters, BLQ values were set to zero unless the BLQ value was between 2 measurable concentrations. In this case, the BLQ value was set to missing.
Pitavastatin and pitavastatin lactone log-transformed Cmax and AUC0-τ in the presence and absence of lopinavir/ritonavir were compared using analysis of variance. Reference treatment was pitavastatin alone on day 5, and test treatment was pitavastatin coadministered with lopinavir/ritonavir on day 24. In addition, lopinavir/ritonavir log-transformed Cmax and AUC0–τ in the presence and absence of pitavastatin were compared using analysis of variance. Reference treatment was lopinavir/ritonavir alone on day 19 and test treatment was lopinavir/ritonavir coadministered with pitavastatin on day 24.
A mixed-effects model was performed on log-transformed PK parameters (AUC0–τ and Cmax) of pitavastatin and pitavastatin lactone and lopinavir/ritonavir with treatment as a fixed effect and subject as a random effect. The least squares means of the log-transformed parameters AUC0–τ and Cmax for the reference and test treatments were exponentiated to obtain the geometric means on the raw data scale. The 90% confidence intervals (CIs) for the geometric mean ratio of the test-to-reference treatments (day 24 versus day 5, and day 24 versus day 19) were calculated for these parameters to evaluate the potential for a DDI. The CIs were reported as a percentage relative to the least squares mean of the reference treatment.
Determination of Sample Size
No formal sample size calculation was performed. A sample size of 20 subjects was considered sufficient to detect any possible interaction between steady-state lopinavir/ritonavir and pitavastatin. Twenty-four subjects were enrolled to allow for dropouts during the study.
Safety evaluations included the assessment of adverse events (AEs), clinical laboratory test results, vital sign measurements, and 12-lead ECG results. The latest version of the Medical Dictionary for Regulatory Activities was used to code the AEs. They were summarized by treatment (pitavastatin alone, lopinavir/ritonavir alone, or pitavastatin and lopinavir/ritonavir) and overall according to intensity, relationship to study drug, and number leading to withdrawal. A treatment-emergent adverse event (TEAE) was defined as an AE that began after the start of study drug or an event that began before the start of study drug and worsened in severity after starting treatment. A treatment-related AE was defined as a TEAE that was considered possibly, probably, or definitely related to the study drug.
Twenty-four subjects were enrolled and 23 subjects completed the study. The subjects enrolled in the study were white (18 of 24 subjects; 75.0%) or African American (6 of 24 subjects; 25%). There were an equal number of male and female subjects. The majority of subjects were not Hispanic or Latino (16 of 24 subjects; 66.7%). The mean age was 33.8 (SD = 8.24) years with a range of 19–45 years. The mean weight was 75.4 (SD = 13.9) kg and the mean body mass index was 25.9 kg/m2.
Plasma Concentration Versus Time Curves of Pitavastatin, Pitavastatin Lactone, Lopinavir, and Ritonavir
Mean plasma concentrations of pitavastatin alone and pitavastatin coadministered with lopinavir/ritonavir were comparable up to 4 hours after dosing. After 4 hours, pitavastatin concentrations at steady state were lower when coadministered with lopinavir/ritonavir than when pitavastatin was administered alone. Mean plasma concentrations of pitavastatin lactone at 1.5 hours after dosing were lower and remained lower at steady state when coadministered with lopinavir/ritonavir than when pitavastatin was administered alone.
Mean plasma concentrations of lopinavir and ritonavir at steady state were slightly lower when lopinavir/ritonavir was coadministered with pitavastatin than when lopinavir/ritonavir was administered alone. Mean plasma concentration versus time profiles for the PK population are illustrated as follows: pitavastatin in Figure 1A, pitavastatin lactone in Figure 1B, lopinavir in Figure 2A, and ritonavir in Figure 2B.
Plasma PK Parameters of Pitavastatin, Pitavastatin Lactone, Lopinavir, and Ritonavir
Following once-daily administration, Cmax of pitavastatin at steady state was similar when pitavastatin was administered alone or coadministered with lopinavir/ritonavir. Mean AUC0–τ was lower when pitavastatin was coadministered with lopinavir/ritonavir than when pitavastatin was administered alone. Median Tmax of pitavastatin was approximately 0.5 hours for both treatments. Mean AUC0–τ and Cmax of pitavastatin lactone at steady state were decreased when pitavastatin was coadministered with lopinavir/ritonavir compared with when pitavastatin was administered alone. Median Tmax of pitavastatin lactone was 1.5 hours for both treatments. Summary of plasma PK parameters for pitavastatin and pitavastatin lactone by treatment and analyte is shown in Table 1.
Following twice-daily administration, mean AUC0–τ and Cmax of lopinavir and ritonavir were similar when lopinavir/ritonavir was coadministered with pitavastatin compared with when lopinavir/ritonavir was administered alone. Median Tmax of lopinavir and ritonavir for both treatments were similar (2.0–3.0 hours). Summary of plasma PK parameters for lopinavir and ritonavir by treatment and analyte is shown in Table 2.
Statistical Analysis of PK Parameters
Statistical comparison of the difference in exposures of pitavastatin when coadministered with lopinavir/ritonavir versus when administered alone indicated that lopinavir/ritonavir did not increase peak exposures of pitavastatin. Coadministration of pitavastatin with lopinavir/ritonavir decreased the AUC0–τ of pitavastatin by approximately 20%. The 90% CI of the geometric least squares mean ratio for AUC0–τ was outside the range of 80% to 125%, with values between 73.4% and 87.3%, whereas the 90% CI of the geometric least squares mean ratio for Cmax was contained within the specified range, with values between 83.6% and 110.4%. Statistical analysis of PK parameters of pitavastatin, pitavastatin lactone, lopinavir, and ritonavir is shown in Table 3.
Statistical comparison of the difference in exposures of pitavastatin lactone when pitavastatin was coadministered with lopinavir/ritonavir versus when administered alone indicated a moderate effect of lopinavir/ritonavir on the total exposure of pitavastatin lactone (decrease of approximately 58%) and a weak effect on peak exposure (decrease of approximately 30%) of pitavastatin lactone. The 90% CIs of the geometric least squares mean ratio for AUC0–τ and Cmax were outside the range of 80% to 125%, with values from 39.0% to 45.2%, and 62.9% to 76.9%, respectively.
Statistical comparison of the difference in exposures of lopinavir and ritonavir when lopinavir/ritonavir was coadministered with pitavastatin versus when administered alone indicated that pitavastatin did not increase the peak and total exposures of lopinavir, had no effect on total exposure of ritonavir, and had only a marginal effect on peak exposure of ritonavir. The 90% CIs of the geometric least squares mean ratio for AUC0–τ and Cmax were from 85.7% to 96. 8% and from 87.8% to 98.1%, respectively, for lopinavir and from 80.5% to 98.1% and from 79.5% to 99.7%, respectively, for ritonavir. The lower 90% CI of the geometric least squares mean ratio of Cmax for ritonavir was 79.5%, marginally lower than 80%.
Overall, 18 of 24 subjects (75.0%) reported TEAEs; 15 (62.5%) after receiving lopinavir/ritonavir alone, 8 (33.3%) after receiving pitavastatin alone, and 2 (8.7%) after pitavastatin coadministered with lopinavir/ritonavir. Treatment-related AEs were reported by 3 subjects (12.5%) after lopinavir/ritonavir alone or pitavastatin alone and by 1 subject (4.3%) after receiving pitavastatin coadministered with lopinavir/ritonavir.
TEAEs reported after pitavastatin only and pitavastatin with lopinavir/ritonavir were mild in severity. Four subjects (16.7%) reported moderate TEAEs after lopinavir/ritonavir only. All TEAEs resolved by the end of the study. One subject was discontinued from the study because of an AE of diarrhea during treatment with lopinavir/ritonavir only. There were no severe AEs or deaths.
There were no clinically significant findings in any of the other safety assessments (clinical laboratory test results, vital sign measurements, ECG results, and physical examinations).
This study was conducted in 24 healthy adult male and female subjects to investigate the PK interaction of lopinavir/ritonavir 400 mg/100 mg twice daily on the PK of pitavastatin 4 mg. In addition, the effect on the safety of pitavastatin 4 mg by the coadministration of lopinavir/ritonavir 400 mg/100 mg twice daily and the PK interaction of pitavastatin 4 mg on the PK of lopinavir/ritonavir 400 mg/100 mg twice daily was investigated. DDIs between PIs and other statins have been reported.14–17 The exposures of simvastatin and atorvastatin have been reported to increase by 505% to 3059% and from 71% to 130%, respectively, with coadministration of PIs.14 Coadministration of darunavir/ritonavir with pravastatin increased the pravastatin least square mean ratio of the 90% CI for Cmax to 1.63 (0.95–2.82) and the AUC to 1.81 (1.23–2.66).15 For rosuvastatin, AUC0–τ and Cmax were increased 2.1-fold and 4.7-fold when given in combination with lopinavir/ritonavir in HIV-seronegative volunteers.16 In HIV-infected patients on the same drug combination, rosuvastatin levels increased 1.6-fold compared with data from healthy volunteers.17 Studies with statins in combination with antiviral agents, in particular, PIs, contribute to better management of the comorbidities related to HIV and its treatment.
This study shows that the PK of pitavastatin 4 mg is minimally affected by coadministration with lopinavir/ritonavir 400 mg/100 mg twice daily. At steady state, when coadministered with lopinavir/ritonavir, pitavastatin peak exposure (Cmax) was unaffected, whereas total exposure (AUC0-τ) was weakly affected (decrease of approximately 20%). Coadministration of lopinavir/ritonavir had a moderate effect on AUC0–τ of pitavastatin lactone at steady state (decrease of approximately 58%) and a weak effect on Cmax of pitavastatin lactone at steady state (decrease of approximately 30%). However, because pitavastatin lactone is an inactive metabolite, this interaction is not expected to influence the efficacy or safety of pitavastatin.
For lopinavir 400 mg twice daily, Cmax and AUC0–τ at steady state were not affected by coadministration of pitavastatin 4 mg. There was no interaction effect of pitavastatin 4 mg on AUC0–τ of ritonavir 100 mg twice daily and a marginal interaction effect of pitavastatin on peak exposure of ritonavir. Importantly, there are few other studies in the literature that evaluated the effect of statins on total and peak exposure of PIs.18
Although generally well tolerated, lopinavir/ritonavir is associated with elevations in total cholesterol, low-density lipoprotein cholesterol, and triglycerides, which may require coadministration of lipid-lowering agents to reduce the risk of coronary heart disease.19 Statins are important lipid-modifying agents in HIV-1–infected patients for the management of high cholesterol and dyslipidemia which may occur due to the natural course of the disease and/or effect of antiretroviral therapy.20 The current study fulfilled the postapproval FDA requirement by demonstrating that there was minimal PK interaction between pitavastatin and lopinavir/ritonavir when coadministered. This has lead to a clinical trial evaluating the effect of pitavastatin on lipid parameters in HIV-1–infected patients with dyslipidemia.21
In conclusion, this study shows that the effect on PK parameters when pitavastatin and lopinavir/ritonavir are coadministered was minimal. Overall, multiple doses of pitavastatin alone and pitavastatin coadministered with lopinavir/ritonavir were safe and well tolerated in the healthy subjects in this study.
The authors wish to acknowledge Maryann Weller of Pharmnet/i3 for assistance with writing and editing the article.
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Keywords:© 2012 Lippincott Williams & Wilkins, Inc.
pitavastatin; lopinavir; ritonavir; HMG-CoA; drug–drug interaction