Lopinavir (LPV) is an HIV protease inhibitor (PI), coformulated with a subtherapeutic dose of ritonavir (RTV), another PI. RTV increases plasma concentrations of LPV by inhibiting its cytochrome P450 (CYP-450)–mediated metabolism.1 This combination (LPV/r) has good efficacy and safety in treatment-naive and treatment-experienced patients.2–4
Dose reductions of several PIs in Thai HIV-1–infected patients result in adequate pharmacokinetic (PK) parameters due to lower body weight and different pharmacogenetic properties compared with Caucasian populations, with continued virological suppression, reduced toxicity, and lower cost.5–10
The tablet formulation of LPV/r (200/50 mg) is bioequivalent to the soft-gel capsules (SGC), heat-stable, and its PK profile is not affected by food.11 Despite significant price reductions for low-income and middle-income countries, the tablets are still expensive. Furthermore, due to a compulsory license, Abbott only markets the pediatric formulation (LPV/r tablets, 100/25 mg) in Thailand. The pharmaceutical company Matrix in India has developed a generic tablet formulation of LPV/r (200/50 mg). The use of these generic LPV/r tablets standard dose (400/100 mg twice daily) in Thai HIV-1–infected patients resulted in a median LPV minimum plasma concentration (Cmin) of 7.2 mg/L,12 well above the therapeutic concentration of 1.0 mg/L for PI-naive patients and more than 10,000-fold higher than the protein binding-adjusted IC50 of wild-type HIV (0.69 ng/mL).13,14 We conducted the present study to determine whether lower dosing of generic LPV/r in Thai HIV-1–infected patients could achieve adequate concentrations and to assess the quality of the generic formulation.
This was a single centre, open-label, prospective, 2-arm, randomized, cross-over PK study. The study was approved by the Ethics Committee of the Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. All participants provided written informed consent. The study was registered with ClinicalTrials.gov (NCT01159275). As this was a proof-of-concept study, we aimed to include 20 patients. Patients were screened at our clinic in Bangkok, Thailand. HIV-infected patients older than 18 years, using a PI-containing regimen for at least 4 weeks before study entry, without an AIDS-defining illness, and with plasma HIV RNA <50 copies per milliliter for at least 24 weeks before study entry were eligible. Study visits were at baseline, weeks 2, 4, and 12.
We collected demographic data and performed urinalysis and pregnancy testing. Participants were randomized at baseline to arm 1 or 2. In addition to a nucleoside reverse transcriptase inhibitor backbone, participants in arm 1 received generic LPV/r (200/50 mg) 1 tablet twice daily, and participants in arm 2 received branded LPV/r (Aluvia, LPV/r tablets, 100/25 mg, Abbott Laboratories, Abbott Park, IL), 2 tablets twice daily. For technical reasons, the participants were not blinded to the product received. After sample collection for PK analysis of LPV and RTV at week 2, patients crossed-over to the other study arm. At week 4, second PK analysis was performed. On both PK sample collection days, adherence was assessed by self-report, and adherence rates were calculated. Participants continued with the study regimen until week 12. After this, patients were switched back to their prestudy medication. Throughout the study, clinical and laboratory assessments (ie, liver transaminases, creatinine, hematology, CD4, and fasting blood glucose and lipids) were performed to evaluate the safety and tolerability of the study medication. Plasma HIV RNA was determined at week 12.
PK analyses were performed at weeks 2 and 4. Patients were provided with standard meals throughout the day of sample collection, and the morning dose was taken under supervision of clinic staff. Six milliliter of blood was collected by venipuncture in a lithium-heparin or heparin-sodium tube shortly before administering the dose and at 1, 2, 3, 4, 6, 8, 10, and 12 hours after drug intake. Blood samples were centrifuged at 3000 revolutions per minute (rpm) at 20°C for 10 minutes. Plasma was transferred to a polypropylene tube and stored at −80°C until processing. The quantitative determination of LPV and RTV in plasma was carried out using a validated high-performance liquid chromatography method.15 The LPV concentration was linear over the range of 0.1–30.0 mg/L. The lower limit of quantification for LPV was 0.1 mg/L. The The HIV Netherlands Australia Thailand Research Collaboration laboratory participates in an international quality control and quality assessment program and has been cross-validated with other PK laboratories.16 The following PK parameters were determined by noncompartmental analysis using Stata version 11.0 (StataCorp LP, College Station, TX): area under the plasma concentration–time curve from 0 to 12 hours (AUC0–12), the maximum plasma drug concentration (Cmax), the trough plasma drug concentration (Ctrough), the time to reach maximum plasma drug concentration (Tmax), and apparent elimination half life (T1/2).
Statistical analyses were performed using Stata version 11.0. Median [interquartile range (IQR)] and frequency (%) were used to describe the demographic characteristics for continuous and categorical data, respectively. Analyses of variance (ANOVA) were performed on the log (natural)-transformed PK parameters AUC0–12, Cmax, and Ctrough. The analyses of variance model included sequence, formulation, and period as fixed effects and subjects within sequence as random effect. To detect statistically significant differences among different doses, the Kruskal–Wallis test was used. Geometric mean ratio (GMR) and 90% confidence interval (CI) for AUC0–12, Cmax, and Ctrough for LPV and RTV were calculated. PK parameters of both products was compared using bioequivalence analysis; the products were considered comparable when the 90% CI of the GMR of LPV AUC0–12 and Cmax of the generic tablet relative to the branded tablet were within the range of 0.80 to 1.25.17
Demographic and Clinical Characteristics
Twenty patients (8 women and 12 men) were included and randomized to one of the study arms (10 to arm 1 and 10 to arm 2). Median (IQR) age of participants was 38.6 (34.4–47.5) years, median (IQR) weight was 59.8 (52.9–62.0) kg, and median (IQR) CD4 count was 578 (476–795) cells per cubic millimeter. All patients had HIV RNA <50 copies per milliliter. Before study entry, 17 patients were using LPV/r (400/100 mg twice daily) for a median (IQR) of 18 (14–47) months; 3 patients were using saquinavir (SQV)/r for a median (IQR) of 30 (29–31) months, all with a nucleoside reverse transcriptase inhibitor backbone. No patients were lost to follow-up, and none discontinued the medication during the study period.
PK parameters for generic and branded LPV/r are shown in Table 1. Generic and branded tablets showed comparable PK parameters. Mean (SD) Ctrough was 1.5 (0.6) mg/L for generic tablets and 1.6 (0.9) mg/L for branded tablets (P = 0.92).
Subtherapeutic plasma concentrations of LPV (<1.0 mg/L) were detected in 8 patients; 2 patients although using generic tablets and 4 patients although using branded tablets. Two other patients had subtherapeutic concentrations on both, resulting in a total of 10 of 40 samples (25%). The lowest LPV plasma concentration measured was 0.25 mg/L. At the time of measured subtherapeutic concentration, all 8 patients reported adherence rates of >90%, and 7 of 8 patients reported adherence rates of 100%.
Results of the bioequivalence analysis comparing branded and generic tablets are shown in Table 2. The 90% CI of the GMR for generic LPV AUC0–12, Cmax, and Cmin were 0.92–1.09, 0.90–1.07, and 0.76–1.31, respectively.
Using data from a previous study by our group, we compared PK parameters of different doses of LPV/r (data not shown).10 Compared with LPV/r SGC 400/100 mg twice daily, LPV/r SGC 266/66 mg twice daily resulted in a 44.1% decreased LPV AUC0–12, a 36.0% decreased LPV Cmax and a 49.1% decreased LPV Ctrough. LPV/r generic tablets 200/50 mg twice daily resulted in a 63.5% decreased AUC0–12, a 56.6% decreased LPV Cmax and a 70.2% decreased LPV Ctrough compared with LPV/r SGC 400/100 mg twice daily.
Virological Response, Safety, and Tolerability
At week 12, all patients had plasma HIV-1 RNA <50 copies per milliliter. One patient experienced an adverse event (jaundice and elevated liver transaminases) during the study, which was unrelated to study drugs and caused by acute hepatitis C virus infection. Median (IQR) triglycerides levels decreased significantly from baseline [175 (131–285) mg/dL] to week 12 [115 (84–217) mg/dL], P < 0.001. Decreases in total cholesterol and low-density lipoprotein cholesterol were not significant.
In this study, we observed inadequate plasma concentrations with LPV/r 200/50 mg twice daily, irrespective of the formulation used, and demonstrated that generic and branded LPV/r tablets have comparable PK parameters.
Using standard dose of generic tablets of LPV/r, we have previously shown encouraging PK parameters and short-term efficacy.12 Reduced dose of LPV/r in Thai HIV-1–infected patient has been described as well in a PK study of SGC LPV/r 400/100 or 266/66 mg twice daily coadministered with SQV 1000 or 600 mg twice daily.10 The number of patients with adequate LPV concentrations was similar in both arms, irrespective of LPV or SQV dose received.
Thai HIV-1–infected patients taking recommended doses of several PIs show higher plasma concentrations, and dose reduction of these PIs result in maintained viral efficacy.6–8 In these studies, the doses of SQV, atazanavir, and indinavir were reduced although maintaining the RTV dose. Compared with PIs such as SQV and darunavir, LPV plasma concentrations are to a greater extent dependent on the RTV dose used, that is, a higher dose of RTV will lead to a higher LPV plasma concentration.18 In our study, we reduced both the LPV and RTV doses, which could partly explain the found subtherapeutic LPV concentrations.
Based on currently available data on the association between LPV concentration and virological efficacy in patients with HIV subtype B, current guidelines recommend a minimum LPV trough concentration of 1.0 mg/L for PI-naive patients.13 Due to the small sample size and limited follow-up time of our study, we cannot draw a definite conclusion about the virological implication of the found subtherapeutic concentrations. Although the lowest measured LPV concentration in our study (0.25 mg/L) was 355-fold higher than the IC50 of wild-type virus,14 prolonged exposure to poor LPV plasma concentrations results in a higher risk of virological failure.19–22 Furthermore, the susceptibility of the CRF01_AE virus (the main HIV subtype found in Thailand) to LPV might be reduced compared with that of subtype B,23 although a difference in virological response rate to LPV according to HIV subtype in a clinical setting has not been established.24
As all patients with subtherapeutic levels reported good adherence, we can consider the possibility of nonadherence as a cause for subtherapeutic concentrations as less likely. However, as we did not perform pill count, socially desirable responding cannot be excluded. Extraordinarily high levels of adherence are required using the 200/50 mg twice daily dose, and this dose would be substantially less forgiving of nonadherence compared with the standard dose.
PK profiles of alternative dosages for LPV/r have been investigated in other populations as well. One of these describes the PK profile of LPV/r in 16 antiretroviral naive patients receiving LPV/r 200/100 mg twice daily. After 3 weeks, the mean (±SD) LPV Ctrough was 3.74 ± 3.46 mg/L, and all patients achieved virological suppression (plasma HIV RNA below 50 copies/mL) after 48 weeks of treatment,3 suggesting 200 mg LPV twice daily is sufficient, if there is a sufficient dose of RTV for boosting of LPV concentrations.
In a study in HIV-uninfected volunteers, using 200/50 mg twice daily, the Ctrough was 70% lower compared with 400/100 mg twice daily, supporting that adequate RTV concentrations are pivotal when reducing the LPV dose.25 Using LPV/r 200/150 mg twice daily, a 26% reduction of LPV plasma concentrations was observed compared with 400/100 mg twice daily, due to higher RTV concentrations. All patients using this dosage had LPV plasma concentrations >1.0 mg/L. This study was not powered to assess the different rates of adverse events between the different doses.
Although we did not compare generic and branded products using the approved dose of LPV/r, that is, 400/100 mg twice daily, our bioequivalence analysis demonstrated that the generic and branded tablets result in comparable PK parameters. These data are particularly important for clinicians working in settings where the branded tablets are not available due to compulsory licensing or cost. The availability of safe and effective generic alternatives to branded second-line treatment will play an important role in the scaling-up of second-line treatment in low-income and middle-income countries.
We thank all the study participants and the staff of The HIV Netherlands Australia Thailand Research Collaboration.
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