Simultaneous population pharmacokinetic model for lopinavir and ritonavir in HIV-infected adults

Population pharmacokinetic analysis of lopinavir in HIV negative individuals exposed to SARS-CoV-2: a COPEP (COronavirus Post-Exposure Prophylaxis) sub-study

BACKGROUND

Lopinavir/ritonavir (LPV/r) is a drug traditionally used for the treatment of HIV that has been repurposed as a potential post-exposure prophylaxis agent against COVID-19 in the COronavirus Post-Exposure Prophylaxis (COPEP) study. The present analysis aims to evaluate LPV levels in individuals exposed to SARS-CoV-2 versus people living with HIV (PLWH) by developing a population pharmacokinetic (popPK) model, while characterizing external and patient-related factors that might affect LPV exposure along with dose-response association.

METHODS

We built a popPK model on 105 LPV concentrations measured in 105 HIV-negative COPEP individuals exposed to SARS-CoV-2, complemented with 170 LPV concentrations from 119 PLWH followed in our routine therapeutic drug-monitoring programme. Published LPV popPK models developed in PLWH and in COVID-19 patients were retrieved and validated in our study population by mean prediction error (MPE) and root mean square error (RMSE). The association between LPV model-predicted residual concentrations (Cmin) and the appearance of the COVID-19 infection in the COPEP participants was investigated.

RESULTS

A one-compartment model with linear absorption and elimination best described LPV concentrations in both our analysis and in the majority of the identified studies. Globally, similar PK parameters were found in all PK models, and provided close MPEs (from -19.4% to 8.0%, with a RMSE of 3.4% to 49.5%). No statistically significant association between Cmin and the occurrence of a COVID-19 infection could be detected.

CONCLUSION

Our analysis indicated that LPV circulating concentrations were similar between COPEP participants and PLWH, and that published popPK models described our data in a comparable way.

Glabridin plays dual action to intensify anti-metastatic potential of paclitaxel via impeding CYP2C8 in liver and CYP2J2/EETs in tumor of an orthotopic mouse model of breast cancer

In spite of unprecedented advances in modern cancer therapy, there is still a dearth of targeted therapy to circumvent triple-negative breast cancer (TNBC). Paclitaxel is the front-line therapy against TNBC, but the main constraints of its treatment are dose-related adverse effects and emerging chemoresistance. In this context, glabridin (phytoconstituent from Glycyrrhiza glabra) is reported to hit multiple signalling pathways at the in-vitro level, but hardly any information is known at the in-vivo level. We aimed here to elucidate glabridin potential with an underlying mechanism in combination with a low dose of paclitaxel using a highly aggressive mouse mammary carcinoma model. Glabridin potentiated the anti-metastatic efficacy of paclitaxel by substantially curtailing tumor burden and diminishing lung nodule formation. Moreover, glabridin remarkably attenuated epithelial-mesenchymal transition (EMT) traits of hostile cancer cells via up-regulating (E-cadherin & occludin) and down-regulating (Vimentin & Zeb1) vital EMT markers. Besides, glabridin amplified apoptotic induction effect of paclitaxel in tumor tissue by declining or elevating pro-apoptotic (Procaspase-9 or Cleaved Caspase-9 & Bax) and reducing anti-apoptotic (Bcl-2) markers. Additionally, concomitant treatment of glabridin and paclitaxel predominantly lessened CYP2J2 expression with marked lowering of epoxyeicosatrienoic acid (EET)'s levels in tumor tissue to reinforce the anti-tumor impact. Simultaneous administration of glabridin with paclitaxel notably enhanced plasma exposure and delayed clearance of paclitaxel, which was mainly arbitrated by CYP2C8-mediated slowdown of paclitaxel metabolism in the liver. The fact of intense CYP2C8 inhibitory action of glabridin was also ascertained using human liver microsomes. Concisely, glabridin plays a dual role in boosting anti-metastatic activity by augmenting paclitaxel exposure via CYP2C8 inhibition-mediated delaying paclitaxel metabolism and limiting tumorigenesis via CYP2J2 inhibition-mediated restricting EETs level. Considering the safety, reported protective efficacy, and the current study results of boosted anti-metastatic effects, further investigations are warranted as a promising neoadjuvant therapy for crux paclitaxel chemoresistance and cancer recurrence.

Herb-Drug Interaction Between Xiyanping Injection and Lopinavir/Ritonavir, Two Agents Used in COVID-19 Pharmacotherapy

The global epidemic outbreak of the coronavirus disease 2019 (COVID-19), which exhibits high infectivity, resulted in thousands of deaths due to the lack of specific drugs. Certain traditional Chinese medicines (TCMs), such as Xiyanping injection (XYPI), have exhibited remarkable benefits against COVID-19. Although TCM combined with Western medicine is considered an effective approach for the treatment of COVID-19, the combination may result in potential herb-drug interactions in the clinical setting. The present study aims to verify the effect of XYPI on the oral pharmacokinetics of lopinavir (LPV)/ritonavir (RTV) using an in vivo rat model and in vitro incubation model of human liver microsomes. After being pretreated with an intravenous dose of XYPI (52.5 mg/kg) for one day and for seven consecutive days, the rats received an oral dose of LPV/RTV (42:10.5 mg/kg). Except for the t_1/2 of LPV is significantly prolonged from 4.66 to 7.18 h (p < 0.05) after seven consecutive days pretreatment, the pretreatment resulted in only a slight change in the other pharmacokinetic parameters of LPV. However, the pharmacokinetic parameters of RTV were significantly changed after pretreatment with XYPI, particularly in treatment for seven consecutive days, the AUC_0-∞ of RTV was significantly shifted from 0.69 to 2.72 h μg/mL (p < 0.05) and the CL exhibited a tendency to decrease from 2.71 L/h to 0.94 L/h (p < 0.05), and the t_1/2 of RTV prolonged from 3.70 to 5.51 h (p < 0.05), in comparison with the corresponding parameters in untreated rats. After administration of XYPI, the expression of Cyp3a1 protein was no significant changed in rats. The in vitro incubation study showed XYPI noncompetitively inhibited human CYP3A4 with an apparent Ki value of 0.54 mg/ml in a time-dependent manner. Our study demonstrated that XYPI affects the pharmacokinetics of LPV/RTV by inhibiting CYP3A4 activity. On the basis of this data, patients and clinicians can take precautions to avoid potential drug-interaction risks in COVID-19 treatment.

Physiologically Based Pharmacokinetic Modelling to Investigate the Impact of the Cytokine Storm on CYP3A Drug Pharmacokinetics in COVID-19 Patients

Patients with coronavirus disease 2019 (COVID‐19) may experience a cytokine storm with elevated interleukin‐6 (IL‐6) levels in response to severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2). IL‐6 suppresses hepatic enzymes, including CYP3A; however, the effect on drug exposure and drug‐drug interaction magnitudes of the cytokine storm and resulting elevated IL‐6 levels have not been characterized in patients with COVID‐19. We used physiologically‐based pharmacokinetic (PBPK) modeling to simulate the effect of inflammation on the pharmacokinetics of CYP3A metabolized drugs. A PBPK model was developed for lopinavir boosted with ritonavir (LPV/r), using clinically observed data from people living with HIV (PLWH). The inhibition of CYPs by IL‐6 was implemented by a semimechanistic suppression model and verified against clinical data from patients with COVID‐19, treated with LPV/r. Subsequently, the verified model was used to simulate the effect of various clinically observed IL‐6 levels on the exposure of LPV/r and midazolam, a CYP3A model drug. Clinically observed LPV/r concentrations in PLWH and patients with COVID‐19 were predicted within the 95% confidence interval of the simulation results, demonstrating its predictive capability. Simulations indicated a twofold higher LPV exposure in patients with COVID‐19 compared with PLWH, whereas ritonavir exposure was predicted to be comparable. Varying IL‐6 levels under COVID‐19 had only a marginal effect on LPV/r pharmacokinetics according to our model. Simulations showed that a cytokine storm increased the exposure of the CYP3A paradigm substrate midazolam by 40%. Our simulations suggest that CYP3A metabolism is altered in patients with COVID‐19 having increased cytokine release. Caution is required when prescribing narrow therapeutic index drugs particularly in the presence of strong CYP3A inhibitors.

Emergent Drug and Nutrition Interactions in COVID-19: A Comprehensive Narrative Review

Coronaviruses are a large family of viruses that are known to cause respiratory tract infections ranging from colds to more severe diseases, such as Middle East Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome (SARS). New Coronavirus Disease 2019 (COVID-19), which led to deaths as well as social and economic disruptions, is an ongoing worldwide pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Currently, there is no approved treatment for COVID-19. Hence, only supportive care has been approved by the World Health Organization (WHO) for now. Pharmacological agents used for the adjunctive treatment of COVID-19 following the current literature and clinical experiences include antiviral, anti-inflammatory, and anti-malaria drugs, and other traditional or untraditional treatments. However, it has been reported that the use of these drugs may have some negative effects and comorbidities. Moreover, the current data have indicated that the risk of drug-drug interactions may also be high in polypharmacy cases, especially in elderly people, some comorbidity situations, and intensive care unit (ICU) patients. It is highly possible that these situations can not only increase the risk of drug-drug interactions but also increase the risk of food/nutrition-drug interactions and affect the nutritional status. However, this issue has not yet been entirely discussed in the literature. In this review, current information on the possible mechanisms as well as pharmacokinetic and pharmacodynamic effects of some pharmacological agents used in the treatment of COVID-19 and/or their secondary interactions with nutrition were evaluated and some future directions were given.

The impact of age on antiretroviral drug pharmacokinetics in the treatment of adults living with HIV

INTRODUCTION

People living with HIV (PLWH) are aging and will receive life-long treatment: despite substantial improvement in drug efficacy and tolerability, side effects still occur and they can blunt antiretroviral treatment effectiveness. Since age may affect drug exposure and may be associated with side-effects we aimed at reviewing available data on the effect of age on antiretrovirals' pharmacokinetics in adult patients.

AREAS COVERED

We searched public databases and major conference proceedings for data on age and pharmacokinetics/pharmacodynamics in PLWH. We limited our review to currently used drugs and focused on population pharmacokinetics and physiologically-based pharmacokinetic modeling studies.

EXPERT OPINION

Available evidence of a potential detrimental effect in elderly PLWH is limited by study design and small sample sizes. Careful consideration of undoubtful benefits and potential harms is advised when prescribing ARVs to geriatric patients and the knowledge of pharmacokinetics changes need to be included in the process. With the 'greying' of the pandemic we need studies with a specific focus on geriatric patients living with HIV that will consider specific phenotypes and associated changes (including sarcopenia).

COVID-19 outbreak: Challenges in pharmacotherapy based on pharmacokinetic and pharmacodynamic aspects of drug therapy in patients with moderate to severe infection

The new coronavirus (COVID-19) was first detected in Wuhan city of China in December 2019. Most patients infected with COVID-19 had clinical presentations of dry cough, fever, dyspnea, chest pain, fatigue and malaise, pneumonia, and bilateral infiltration in chest CT. Soon COVID-19 was spread around the world and became a pandemic. Now many patients around the world are suffering from this disease. Patients with predisposing diseases are highly prone to COVID-19 and manifesting severe infection especially with organ function damage such as acute respiratory distress syndrome, acute kidney injury, septic shock, ventilator-associated pneumonia, and death. Till now many drugs have been considered in the treatment of COVID-19 pneumonia, but pharmacotherapy in elderly patients and patients with pre-existing comorbidities is highly challenging. In this review, different potential drugs which have been considered in COVID-19 treatment have been discussed in detail. Also, challenges in the pharmacotherapy of COVID-19 pneumonia in patients with the underlying disease have been considered based on pharmacokinetic and pharmacodynamic aspects of these drugs.

Population pharmacokinetics of lopinavir/ritonavir in Covid-19 patients

Objective

To develop a population pharmacokinetic model for lopinavir boosted by ritonavir in coronavirus disease 2019 (Covid-19) patients.

Methods

Concentrations of lopinavir/ritonavir were assayed by an accredited LC-MS/MS method. The population pharmacokinetics of lopinavir was described using non-linear mixed-effects modeling (NONMEM version 7.4). After determination of the base model that better described the data set, the influence of covariates (age, body weight, height, body mass index (BMI), gender, creatinine, aspartate aminotransferase (AST), alanine aminotransferase (ALT), C reactive protein (CRP), and trough ritonavir concentrations) was tested on the model.

Results

From 13 hospitalized patients (4 females, 9 males, age = 64 ± 16 years), 70 lopinavir/ritonavir plasma concentrations were available for analysis. The data were best described by a one-compartment model with a first-order input (KA). Among the covariates tested on the PK parameters, only the ritonavir trough concentrations had a significant effect on CL/F and improved the fit. Model-based simulations with the final parameter estimates under a regimen lopinavir/ritonavir 400/100 mg b.i.d. showed a high variability with median concentration between 20 and 30 mg/L (C_min/C_max) and the 90% prediction intervals within the range 1–100 mg/L.

Conclusion

According to the estimated 50% effective concentration of lopinavir against SARS-CoV-2 virus in Vero E6 cells (16.7 mg/L), our model showed that at steady state, a dose of 400 mg b.i.d. led to 40% of patients below the minimum effective concentration while a dose of 1200 mg b.i.d. will reduce this proportion to 22%.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-03020-w) contains supplementary material, which is available to authorized users.

Abnormal laboratory findings and plasma concentration monitoring of lopinavir and ritonavir in COVID-19

It is not known whether the adverse events (AEs) associated with the administration of lopinavir and ritonavir (LPV/r) in the treatment of COVID-19 are concentration-dependent. In a retrospective study of 65 patients treated with LPV/r and therapeutic drug monitoring (TDM) for severe forms of COVID-19 (median age: 67; males: 41 [63.1%]), 33 (50.8%) displayed a grade ≥2 increase in plasma levels of hepatobiliary markers, lipase and/or triglycerides. A causal relationship between LPV/r and the AE was suspected in 9 of the 65 patients (13.8%). At 400 mg b.i.d., the plasma trough concentrations of LPV/r were high and showed marked interindividual variability (median [interquartile range]: 16,600 [11,430-20,842] ng/ml for lopinavir and 501 [247-891] ng/ml for ritonavir). The trough lopinavir concentration was negatively correlated with body mass index, while the trough ritonavir concentration was positively correlated with age and negatively correlated with prothrombin activity. However, the occurrence of abnormal laboratory values was not associated with higher trough plasma concentrations of LPV/r. Further studies will be needed to determine the value of TDM in LPV/r-treated patients with COVID-19.

Evaluating darunavir/ritonavir dosing regimens for HIV-positive pregnant women using semi-mechanistic pharmacokinetic modelling

BACKGROUND

Darunavir 800 mg once (q24h) or 600 mg twice (q12h) daily combined with low-dose ritonavir is used to treat HIV-positive pregnant women. Decreased total darunavir exposure (17%-50%) has been reported during pregnancy, but limited data on unbound exposure are available.

OBJECTIVES

To evaluate total and unbound darunavir exposures following standard darunavir/ritonavir dosing and to explore the value of potential optimized darunavir/ritonavir dosing regimens for HIV-positive pregnant women.

PATIENTS AND METHODS

A population pharmacokinetic analysis was conducted based on data from 85 women. The final model was used to simulate total and unbound darunavir AUC0-τ and Ctrough during the third trimester of pregnancy, as well as to assess the probability of therapeutic exposure.

RESULTS

Simulations predicted that total darunavir exposure (AUC0-τ) was 24% and 23% lower in pregnancy for standard q24h and q12h dosing, respectively. Unbound darunavir AUC0-τ was 5% and 8% lower compared with post-partum for standard q24h and q12h dosing, respectively. The probability of therapeutic exposure (unbound) during pregnancy was higher for standard q12h dosing (99%) than for q24h dosing (94%).

CONCLUSIONS

The standard q12h regimen resulted in maximal and higher rates of therapeutic exposure compared with standard q24h dosing. Darunavir/ritonavir 600/100 mg q12h should therefore be the preferred regimen during pregnancy unless (adherence) issues dictate q24h dosing. The value of alternative dosing regimens seems limited.

Population Pharmacokinetics of Lopinavir/Ritonavir: Changes Across Formulations and Human Development From Infancy Through Adulthood

Lopinavir/ritonavir (LPV/r) is recommended by the World Health Organization as first-line treatment for HIV-infected infants and young children. We performed a composite population pharmacokinetic (PK) analysis on LPV plasma concentration data from 6 pediatric and adult studies to determine maturation and formulation effects from infancy to adulthood. Intensive PK data were available for infants, children, adolescents, and adults (297 intensive profiles/1662 LPV concentrations). LPV PK data included 1 adult, 1 combined pediatric-adult, and 4 pediatric studies (age 6 weeks to 63 years) with 3 formulations (gel-capsule, liquid, melt-extrusion tablets). LPV concentrations were modeled using nonlinear mixed effects modeling (NONMEM v. 7.3; GloboMax, Hanover, Maryland) with a one compartment semiphysiologic model. LPV clearance was described by hepatic plasma flow (QHP ) times hepatic extraction (EH ), with EH estimated from the PK data. Volume was scaled by linear weight (WT/70)1.0 . Bioavailability was assessed separately as a function of hepatic extraction and the fraction absorbed from the gastrointestinal tract. The absorption component of bioavailability increased with age and tablet formulation. Monte Carlo simulations of the final model using current World Health Organization weight-band dosing recommendations demonstrated that participants younger than 6 months of age had a lower area under the drug concentration-time curve (94.8 vs >107.4 μg hr/mL) and minimum observed concentration of drug in blood plasma (5.0 vs > 7.1 μg/mL) values compared to older children and adults. Although World Health Organization dosing recommendations include a larger dosage (mg/m2 ) in infants to account for higher apparent clearance, they still result in low LPV concentrations in many infants younger than 6 months of age receiving the liquid formulation.

Pharmacokinetics and Drug-Drug Interactions of Lopinavir-Ritonavir Administered with First- and Second-Line Antituberculosis Drugs in HIV-Infected Children Treated for Multidrug-Resistant Tuberculosis

Lopinavir-ritonavir forms the backbone of current first-line antiretroviral regimens in young HIV-infected children. As multidrug-resistant (MDR) tuberculosis (TB) frequently occurs in young children in high-burden TB settings, it is important to identify potential interactions between MDR-TB treatment and lopinavir-ritonavir. We describe the pharmacokinetics of and potential drug-drug interactions between lopinavir-ritonavir and drugs routinely used for MDR-TB treatment in HIV-infected children. A combined population pharmacokinetic model was developed to jointly describe the pharmacokinetics of lopinavir and ritonavir in 32 HIV-infected children (16 with MDR-TB receiving treatment with combinations of high-dose isoniazid, pyrazinamide, ethambutol, ethionamide, terizidone, a fluoroquinolone, and amikacin and 16 without TB) who were established on a lopinavir-ritonavir-containing antiretroviral regimen. One-compartment models with first-order absorption and elimination for both lopinavir and ritonavir were combined into an integrated model. The dynamic inhibitory effect of the ritonavir concentration on lopinavir clearance was described using a maximum inhibition model. Even after adjustment for the effect of body weight with allometric scaling, a large variability in lopinavir and ritonavir exposure, together with strong correlations between the pharmacokinetic parameters of lopinavir and ritonavir, was detected. MDR-TB treatment did not have a significant effect on the bioavailability, clearance, or absorption rate constants of lopinavir or ritonavir. Most children (81% of children with MDR-TB, 88% of controls) achieved therapeutic lopinavir trough concentrations (>1 mg/liter). The coadministration of lopinavir-ritonavir with drugs routinely used for the treatment of MDR-TB was found to have no significant effect on the key pharmacokinetic parameters of lopinavir or ritonavir. These findings should be considered in the context of the large interpatient variability found in the present study and the study's modest sample size.

Population pharmacokinetic modelling of the changes in atazanavir plasma clearance caused by ritonavir plasma concentrations in HIV-1 infected patients

AIMS

The aim of the present study was to develop a simultaneous population pharmacokinetic model for atazanavir (ATV) incorporating the effect of ritonavir (RTV) on clearance to predict ATV concentrations under different dosing regimens in HIV-1-infected patients.

METHODS

A Cross-sectional study was carried out in 83 HIV-1-infected adults taking ATV 400 mg or ATV 300 mg/RTV 100 mg once daily. Demographic and clinical characteristics were registered and blood samples collected to measure drug concentrations. A population pharmacokinetic model was constructed using nonlinear mixed-effects modelling and used to simulate six dosing scenarios.

RESULTS

The selected one-compartmental model described the pharmacokinetics of RTV and ATV simultaneously, showing exponential, direct inhibition of ATV clearance according to the RTV plasma concentration, which explained 17.5% of the variability. A mean RTV plasma concentration of 0.63 mg l-1 predicted an 18% decrease in ATV clearance. The percentages of patients with an end-of-dose-interval concentration of ATV below or above the minimum and maximum target concentrations of 0.15 mg l-1 and 0.85 mg l-1 favoured the selection of the simulated ATV/RTV once-daily regimens (ATV 400 mg, ATV 300 mg/RTV 100 mg, ATV 300 mg/RTV 50 mg, ATV 200/RTV 100 mg) over the unboosted twice-daily regimens (ATV 300 mg, ATV 200 mg).

CONCLUSIONS

A one-compartment simultaneous model can describe the pharmacokinetics of RTV and ATV, including the effect of RTV plasma concentrations on ATV clearance. This model is promising for predicting individuals' ATV concentrations in clinical scenarios, and supports further clinical trials of once-daily doses of ATV 300 mg/RTV 50 mg or ATV 200 mg/RTV 100 mg to confirm efficacy and safety.

Development of a Tumour Growth Inhibition Model to Elucidate the Effects of Ritonavir on Intratumoural Metabolism and Anti-tumour Effect of Docetaxel in a Mouse Model for Hereditary Breast Cancer

In a mouse tumour model for hereditary breast cancer, we previously explored the anti-cancer effects of docetaxel, ritonavir and the combination of both and studied the effect of ritonavir on the intratumoural concentration of docetaxel. The objective of the current study was to apply pharmacokinetic (PK)-pharmacodynamic (PD) modelling on this previous study to further elucidate and quantify the effects of docetaxel when co-administered with ritonavir. PK models of docetaxel and ritonavir in plasma and in tumour were developed. The effect of ritonavir on docetaxel concentration in the systemic circulation of Cyp3a knock-out mice and in the implanted tumour (with inherent Cyp3a expression) was studied, respectively. Subsequently, we designed a tumour growth inhibition model that included the inhibitory effects of both docetaxel and ritonavir. Ritonavir decreased docetaxel systemic clearance with 8% (relative standard error 0.4%) in the co-treated group compared to that in the docetaxel only-treated group. The docetaxel concentration in tumour tissues was significantly increased by ritonavir with mean area under the concentration-time curve 2.5-fold higher when combined with ritonavir. Observed tumour volume profiles in mice could be properly described by the PK/PD model. In the co-treated group, the enhanced anti-tumour effect was mainly due to increased docetaxel tumour concentration; however, we demonstrated a small but significant anti-tumour effect of ritonavir addition (p value <0.001). In conclusion, we showed that the increased anti-tumour effect observed when docetaxel is combined with ritonavir is mainly caused by enhanced docetaxel tumour concentration and to a minor extent by a direct anti-tumour effect of ritonavir.

No Need for Lopinavir Dose Adjustment during Pregnancy: a Population Pharmacokinetic and Exposure-Response Analysis in Pregnant and Nonpregnant HIV-Infected Subjects

Lopinavir-ritonavir is frequently prescribed to HIV-1-infected women during pregnancy. Decreased lopinavir exposure has been reported during pregnancy, but the clinical significance of this reduction is uncertain. This analysis aimed to evaluate the need for lopinavir dose adjustment during pregnancy. We conducted a population pharmacokinetic analysis of lopinavir and ritonavir concentrations collected from 84 pregnant and 595 nonpregnant treatment-naive and -experienced HIV-1-infected subjects enrolled in six clinical studies. Lopinavir-ritonavir doses in the studies ranged between 400/100 and 600/150 mg twice daily. In addition, linear mixed-effect analysis was used to compare the area under the concentration-time curve from 0 to 12 h (AUC0-12) and concentration prior to dosing (Cpredose) in pregnant women and nonpregnant subjects. The relationship between lopinavir exposure and virologic suppression in pregnant women and nonpregnant subjects was evaluated. Population pharmacokinetic analysis estimated 17% higher lopinavir clearance in pregnant women than in nonpregnant subjects. Lopinavir clearance values postpartum were 26.4% and 37.1% lower than in nonpregnant subjects and pregnant women, respectively. As the tablet formulation was estimated to be 20% more bioavailable than the capsule formulation, no statistically significant differences between lopinavir exposure in pregnant women receiving the tablet formulation and nonpregnant subjects receiving the capsule formulation were identified. In the range of lopinavir AUC0-12 or Cpredose values observed in the third trimester, there was no correlation between lopinavir exposure and viral load or proportion of subjects with virologic suppression. Similar efficacy was observed between pregnant women and nonpregnant subjects receiving lopinavir-ritonavir at 400/100 mg twice daily. The pharmacokinetic and pharmacodynamic results support the use of a lopinavir-ritonavir 400/100-mg twice-daily dose during pregnancy.

CYP3A4 polymorphism and lopinavir toxicity in an HIV-infected pregnant woman

Cytochrome P450 (CYP) 3A4 has been considered to be the most important enzyme system for metabolism of lopinavir/ritonavir (LPV/r), a widely used HIV protease inhibitor (PI) recommended during pregnancy. Herein we present a clinical case of a pregnant HIV-infected woman who was taking standard doses of LPV/r, 400/100 mg twice daily. The trough plasma concentrations for LPV were fourfold above that recommended for PI-pretreated patients and toxicity associated with LPV/r and PI regimens was observed. These high concentrations continued after delivery in spite of a dosage reduction. The pharmacogenetic analysis revealed a genetic polymorphism in the CYP3A4 gene that encodes a non-functional protein. The pharmacokinetic study could indicate the occurrence of a phenomenon of non-linear pharmacokinetics which would justify why dosage reduction after pregnancy did not proportionally affect the patient's degree of exposure to the drug. In addition, an increment in CYP3A activity during pregnancy could explain lower LPV/r exposure during this period compared to postpartum, despite the impaired activity of CYP3A4 caused by the polymorphism.

Impact of body weight and missed doses on lopinavir concentrations with standard and increased lopinavir/ritonavir doses during late pregnancy

OBJECTIVES

To assess the influence of body weight and missed doses on lopinavir pharmacokinetics with standard and increased doses of lopinavir/ritonavir melt extrusion tablets during late pregnancy.

PATIENTS AND METHODS

Lopinavir concentration data during the third trimester of pregnancy were pooled from clinical trials in Thailand (NCT00409591) and the USA (NCT00042289). A total of 154 HIV-infected pregnant women receiving either 400/100 mg (standard) or 600/150 mg (increased) twice daily had lopinavir plasma concentration data available. Population parameters were estimated using non-linear mixed-effects regression models. Monte Carlo simulations were performed to estimate the probability of achieving target lopinavir trough concentrations (>1.0 mg/L) with standard and increased doses of lopinavir/ritonavir during pregnancy.

RESULTS

The median (range) age, weight and gestational age were 28 years (18-43), 62 kg (45-123) and 33 weeks (29-38), respectively. Body weight influenced lopinavir oral clearance (CL/F) and volume of distribution (V/F). Population estimates of lopinavir CL/F and V/F were 6.21 L/h/70 kg and 52.6 L/70 kg, respectively. Based on simulations, the highest risk of subtherapeutic trough concentrations was for women weighing >100 kg using the standard dose (∼ 7%), while the risk was <2% with the 600/150 mg dose for women weighing 40-130 kg. After a missed dose, 61% of women have lopinavir concentrations below target prior to the next dose with the standard dose compared with 42% with the increased dose.

CONCLUSIONS

Standard dosing provides adequate lopinavir trough concentrations for the majority of pregnant women but increased doses may be preferable for women weighing >100 kg and with a history of lopinavir/ritonavir use and/or adherence issues.

Population pharmacokinetic/pharmacogenetic model of lopinavir/ritonavir in HIV-infected patients

AIM

This study aims to develop a population pharmacokinetic/pharmacogenetic model for lopinavir/ritonavir (LPV/r) in European HIV-infected patients.

MATERIALS & METHODS

A total of 693 LPV/r plasma concentrations were assessed and 15 single-nucleotide polymorphisms were genotyped. The population pharmacokinetic/pharmacogenetic model was created using a nonlinear mixed-effect approach (NONMEM^® v.7.2.0., ICON Development Solutions, Dublin, Ireland).

RESULTS

Covariates significantly related to LPV/r apparent clearance (CL/F) were ritonavir trough concentration (RTC), BMI, high-density lipoprotein cholesterol (HDL-C) and certain single-nucleotide polymorphisms in genes encoding for metabolizing enzymes, which are representable as follows: CL/F = (0.216BMI + 0.0125HDL-C) × 0.713^RTC × 1.26^{rs28371764[C/T]} × 0.528^{rs6945984[C/C]} × 0.302 ^{CYP3A4[1461insA/del]} Conclusion: The LPV/r standard dose appears to be appropriate for the rs28371764[C/T] genotype. However, lower doses should be recommended for the rs6945984[C/C] and CYP3A4[1461insA/del] genotypes and even for those patients without any of these variants, as the standard dose seems to be higher than that which is required in order to achieve therapeutic levels.

Determination of total and unbound concentrations of lopinavir in plasma using liquid chromatography-tandem mass spectrometry and ultrafiltration methods

Lopinavir is an HIV protease inhibitor with high protein binding (98-99%) in human plasma. This study was designed to develop an ultrafiltration method to measure the unbound concentrations of lopinavir overcoming the non-specific binding issue. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of total concentrations of lopinavir in plasma was developed and validated, and an adaptation was also optimized and validated for the determination of unbound concentrations. The chromatographic separation was performed with a C18 column (100 mm × 2.1mm i.d., 5 μm particle size) using a mobile phase containing deionized water with formic acid, and acetonitrile, with gradient elution at a flow-rate of 350 μL min(-1). Identification of the compounds was performed by multiple reaction monitoring, using electrospray ionization in positive ion mode. The method was validated over a clinical range of 0.01-1 μg/mL for human plasma ultrafiltrate and 0.1-15 μg/mL in human plasma. The inter and intra-assay accuracies and precisions were between 0.23% and 11.37% for total lopinavir concentrations, and between 3.50% and 13.30% for plasma ultrafiltrate (unbound concentration). The ultrafiltration method described allows an accurate separation of the unbound fraction of lopinavir, circumscribing the loss of drug by nonspecific binding (NSB), and the validated LC-MS/MS methodology proposed is suitable for the determination of total and unbound concentrations of lopinavir in clinical practice.

Toxicogenetics of lopinavir/ritonavir in HIV-infected European patients

AIMS

We present a genetic association study in 106 European HIV-infected individuals aimed at identifying and confirming polymorphisms that have a significant influence on toxicity derived from treatment with lopinavir/ritonavir (LPV/r).

PATIENTS & METHODS

Genotyping was performed by matrix-assisted laser desorption/ionization-time of flight and KASPar^® (KBiosciences, Hoddesdon, UK); LPV/r plasma concentrations were quantified using HPLC with an UV detection system and the pharmacokinetic parameters were estimated using Bayesian algorithms. Genetic association analysis was performed with PASW Statistics 18 (SPSS Inc., IL, USA) and R for Windows (Microsoft, WA, USA).

RESULTS

Suggestive relationships have been established between lipid plasma levels and total bilirubin and SNPs in CETP, MCP1, ABCC2, LEP and SLCO1B3 genes and between diarrhea and SNPs in IL6 gene.

CONCLUSION

Replication analysis should confirm the novel results obtained in this study prior to its application in the clinical practice to achieve a safer LPV/r-based combined antiretroviral therapy.

Pharmacokinetics of lopinavir/ritonavir and efavirenz in food insecure HIV-infected pregnant and breastfeeding women in Tororo, Uganda

Pregnancy and food insecurity may impact antiretroviral (ART) pharmacokinetics (PK), adherence and response. We sought to quantify and characterize the PK of lopinavir/ritonavir (LPV/r) and efavirenz (EFV) by pregnancy and nutritional status among HIV-infected women in Tororo, Uganda. In 2011, 62/225 ante-partum/post-partum single dried blood spot samples DBS and 43 post-partum hair samples for LPV/r were derived from 116 women, 51/194 ante-/post-partum DBS and 53 post-partum hair samples for EFV from 105 women. Eighty percent of Ugandan participants were severely food insecure, 26% lost weight ante-partum, and median BMI post-partum was only 20.2 kg/m(2) . Rich PK-data of normally nourished (pregnant) women and healthy Ugandans established prior information. Overall, drug exposure was reduced (LPV -33%, EFV -15%, ritonavir -17%) compared to well-nourished controls (P < 0.001), attributable to decreased bioavailability. Pregnancy increased LPV/r clearance 68% (P < 0.001), whereas EFV clearance remained unchanged. Hair concentrations correlated with plasma-exposure (P < 0.001), explaining 29% PK-variability. In conclusion, pregnancy and food insecurity were associated with lower ART exposures in this cohort of predominantly underweight women, compared to well-nourished women. Much variability in plasma-exposure was quantified using hair concentrations. Addressing malnutrition as well as ART-PK in this setting should be a priority.

Simultaneous population pharmacokinetic modelling of atazanavir and ritonavir in HIV-infected adults and assessment of different dose reduction strategies

OBJECTIVES

The objective of this study was to develop a simultaneous population pharmacokinetic (PK) model to describe atazanavir/ritonavir (ATV/RTV) PK (300/100 mg) and to assess the effect of RTV dose reduction on ATV PK. Simulations of ATV concentration-time profiles were performed at doses of ATV/RTV 300/50 mg, 200/50 mg, and 200/100 mg once daily.

METHODS

A total of 288 ATV and 312 RTV plasma concentrations from 30 patients were included to build a population PK model using the stochastic approximation expectation maximization algorithm implemented in MONOLIX 3.2 software.

RESULTS

A one-compartment model with first-order absorption and lag-time best described the data for both drugs in the final simultaneous model. A maximum-effect model in which RTV inhibited the elimination of ATV was used to describe the relationship between RTV concentrations and ATV clearance (CL/F). An RTV concentration of 0.22 mg/L was associated with 50% maximum inhibition of ATV CL/F. The population prediction of ATV CL/F in the absence of RTV was 16.6 L/h (relative standard error, 7.0%), and the apparent volume of distribution and absorption rate constant were 106 L (relative standard error, 8%) and 0.87 per hour (fixed), respectively. Simulated average ATV trough concentrations at ATV/RTV 300/50 mg, 200/50 mg, and 200/100 mg once daily were 45%, 63%, and 33% lower, respectively, than that of the standard dose.

CONCLUSION

Although simulated median ATV trough concentrations after dose reductions were still more than the ATV minimum effective concentration (2.9-, 1.9-, and 3.6-fold for ATV/RTV 300/50 mg, 200/50 mg, and 200/100 mg, respectively); our modeling predicted a high proportion of individuals with subtherapeutic trough concentrations on the 200/50 mg dose. This suggests that 300/50 mg and 200/100 mg dosing are preferred candidate regimens in future clinical studies.

Fundamentals of population pharmacokinetic modelling: validation methods

Population pharmacokinetic modelling is widely used within the field of clinical pharmacology as it helps to define the sources and correlates of pharmacokinetic variability in target patient populations and their impact upon drug disposition; and population pharmacokinetic modelling provides an estimation of drug pharmacokinetic parameters. This method's defined outcome aims to understand how participants in population pharmacokinetic studies are representative of the population as opposed to the healthy volunteers or highly selected patients in traditional pharmacokinetic studies. This review focuses on the fundamentals of population pharmacokinetic modelling and how the results are evaluated and validated. This review defines the common aspects of population pharmacokinetic modelling through a discussion of the literature describing the techniques and placing them in the appropriate context. The concept of validation, as applied to population pharmacokinetic models, is explored focusing on the lack of consensus regarding both terminology and the concept of validation itself. Population pharmacokinetic modelling is a powerful approach where pharmacokinetic variability can be identified in a target patient population receiving a pharmacological agent. Given the lack of consensus on the best approaches in model building and validation, sound fundamentals are required to ensure the selected methodology is suitable for the particular data type and/or patient population. There is a need to further standardize and establish the best approaches in modelling so that any model created can be systematically evaluated and the results relied upon.

Model-based approach to dose optimization of lopinavir/ritonavir when co-administered with rifampicin

AIMS

Rifampicin, a key component of antitubercular treatment, profoundly reduces lopinavir concentrations. The aim of this study was to develop an integrated population pharmacokinetic model accounting for the drug-drug interactions between lopinavir, ritonavir and rifampicin, and to evaluate optimal doses of lopinavir/ritonavir when co-administered with rifampicin.

METHODS

Steady-state pharmacokinetics of lopinavir and ritonavir were sequentially evaluated after the introduction of rifampicin and gradually escalating the dose in a cohort of 21 HIV-infected adults. Intensive pharmacokinetic sampling was performed after each dose adjustment following a morning dose administered after fasting overnight. A population pharmacokinetic analysis was conducted using NONMEM 7.

RESULTS

A simultaneous integrated model was built. Rifampicin reduced the oral bioavailability of lopinavir and ritonavir by 20% and 45% respectively, and it increased their clearance by 71% and 36% respectively. With increasing concentrations of ritonavir, clearance of lopinavir decreased in an E(max) relationship. Bioavailability was 42% and 45% higher for evening doses compared with morning doses for lopinavir and ritonavir, respectively, while oral clearance of both drugs was 33% lower overnight. Simulations predicted that 99.5% of our patients receiving doubled doses of lopinavir/ritonavir achieve morning trough concentrations of lopinavir > 1 mg l(-1) during rifampicin co-administration, and 95% of those weighing less than 50 kg achieve this target already with 600/150 mg doses of lopinavir/ritonavir.

CONCLUSIONS

The model describes the drug-drug interactions between lopinavir, ritonavir and rifampicin in adults. The higher trough concentrations observed in the morning were explained by both higher bioavailability with the evening meal and lower clearance overnight.

Estimation of the effect of SLCO1B1 polymorphisms on lopinavir plasma concentration in HIV-infected adults

BACKGROUND

The organic anion transporting polypeptides (OATP)/SLCO family represents an important class of hepatic drug uptake transporters that mediate the sodium independent transport of a diverse range of amphipathic organic compounds, including the protease inhibitors. The SLCO1B1 521T>C (rs4149056) single nucleotide polymorphism (SNP) has been consistently associated with reduced transport activity in vivo, and we previously showed an association of this polymorphism with lopinavir plasma concentrations. The aim of this study was to develop a population pharmacokinetic (PK) model to quantify the impact of 521T>C.

METHODS

A population PK analysis was performed with 594 plasma samples from 375 patients receiving lopinavir/ritonavir. Non-linear mixed effects modelling was applied to explore the effects of SLCO1B1 521T>C and patient demographics. Simulations of the lopinavir concentration profile were performed with different dosing regimens considering the different alleles.

RESULTS

A one-compartment model with first-order absorption best described the data. Population clearance was 5.67 l/h with inter-patient variability of 37%. Body weight was the only demographic factor influencing clearance, which increased 0.5 l/h for every 10 kg increase. Homozygosity for the C allele was associated with a 37% lower clearance, and 14% for heterozygosity, which were statistically significant.

CONCLUSIONS

These data show an association between SLCO1B1 521T>C and lopinavir clearance. The association is likely to be mediated through reduced uptake by hepatocytes leading to higher plasma concentrations of lopinavir. Further studies are now required to confirm the association and to assess the influence of other polymorphisms in the SLCO family on lopinavir PK.

[New strategies in the optimisation of lopinavir/ritonavir doses in human immunodeficiency virus-infected patients]

Lopinavir/ritonavir (LPV/r) has demonstrated virological and immunological efficacy in the combined antiretroviral treatment (cART), in both naïve and experienced patients. Furthermore, LPV/r showed a high barrier to the development of resistance. Although generally well tolerated, adverse gastrointestinal side effects and metabolic disorders are frequent. The different tools used to optimise the cART with this drug combination in the daily clinical practice, emphasising the therapeutic drug monitoring (TDM) of LPV/r and the genetic analysis of the main enzymes responsible for the metabolism and transport, are reviewed. The relationship between phenotype and genotype, established through TDM, could be useful for the physician to improve the clinical management of the HIV infection, due to the possibility of individualising the dose with this drug. Monotherapy is also reviewed as a new strategy used in the simplification of the treatment with this drug, which could increase safety and reduce costs.

Population pharmacokinetics of lopinavir/ritonavir (Kaletra) in HIV-infected patients

BACKGROUND

A relationship between plasma concentrations and viral suppression in patients receiving lopinavir (LPV)/ritonavir (RTV) has been observed. Therefore, it is important to increase our knowledge about factors that determine interpatient variability in LPV pharmacokinetics (PK).

METHODS

The study, designed to develop and validate population PK models for LPV and RTV, involved 263 ambulatory patients treated with 400/100 mg of LPV/RTV twice daily. A database of 1110 concentrations of LPV and RTV (647 from a single time-point and 463 from 73 full PK profiles) was available. Concentrations were determined at steady state using high-performance liquid chromatography with ultraviolet detection. PK analysis was performed with NONMEM software. Age, gender, height, total body weight, body mass index, RTV trough concentration (RTC), hepatitis C virus coinfection, total bilirubin, hospital of origin, formulation and concomitant administration of efavirenz (EFV), saquinavir (SQV), atazanavir (ATV), and tenofovir were analyzed as possible covariates influencing LPV/RTV kinetic behavior.

RESULTS

Population models were developed with 954 drug plasma concentrations from 201 patients, and the validation was conducted in the remaining 62 patients (156 concentrations). A 1-compartment model with first-order absorption (including lag-time) and elimination best described the PK. Proportional error models for interindividual and residual variability were used. The final models for the drugs oral clearance (CL/F) were as follows: CL/F(LPV)(L/h)=0.216·BMI·0.81(RTC)·1.25(EFV)·0.84(ATV); CL/F(RTV)(L/h) = 8.00·1.34(SQV)·1.77(EFV)·1.35(ATV). The predictive performance of the final population PK models was tested using standardized mean prediction errors, showing values of 0.03 ± 0.74 and 0.05 ± 0.91 for LPV and RTV, and normalized prediction distribution error, confirming the suitability of both models.

CONCLUSIONS

These validated models could be implemented in clinical PK software and applied to dose individualization using a Bayesian approach for both drugs.

Assessment of lopinavir pharmacokinetics with respect to developmental changes in infants and the impact on weight band-based dosing

Improved antiretroviral therapies are needed for the treatment of HIV-infected infants, given the rapid progression of the disease and drug resistance resulting from perinatal exposure to antiretrovirals. We examined longitudinal pharmacokinetics (PK) data from a clinical trial of lopinavir/ritonavir (LPV/r) in HIV-infected infants in whom therapy was initiated at less than 6 months of age. A population PK analysis was performed using NONMEM to characterize changes in lopinavir (LPV) PK relating to maturational changes in infants, and to assess dosing requirements in this population. We also investigated the relationship between LPV PK and viral dynamic response. Age and ritonavir concentrations were the only covariates found to be significant. Population PK of LPV was characterized by high apparent clearance (CL/F) in young infants, which decreased with increasing age. Although younger infants had lower LPV concentrations, the viral dynamics did not correlate with initial LPV exposure. Monte Carlo simulations demonstrated that WHO weight band-based dosing recommendations predicted therapeutic LPV concentrations and provided drug exposure levels comparable to those resulting from US Food and Drug Administration (FDA)-suggested dosing regimens.

Sequential population pharmacokinetic modeling of lopinavir and ritonavir in healthy volunteers and assessment of different dosing strategies

Nonlinear mixed-effects modeling was applied to explore the relationship between lopinavir and ritonavir concentrations over 72 h following drug cessation and also to assess other lopinavir and ritonavir dosing strategies compared to the standard 400-mg-100-mg twice-daily dose. Data from 16 healthy volunteers were included. Possible covariates influencing lopinavir and ritonavir pharmacokinetics were also assessed. Data were modeled first separately and then together by using individually predicted ritonavir pharmacokinetic parameters in the final lopinavir model. The model was evaluated by means of a visual predictive check and external validation. A maximum-effect model in which ritonavir inhibited the elimination of lopinavir best described the relationship between ritonavir concentrations and lopinavir clearance (CL/F). A ritonavir concentration of 0.06 mg/liter was associated with a 50% maximum inhibition of the lopinavir CL/F. The population prediction of the lopinavir CL/F in the absence of ritonavir was 21.6 liters/h (relative standard error, 14.0%), and the apparent volume of distribution and absorption rate constant were 55.3 liters (relative standard error, 10.2%) and 0.57 h(-1) (relative standard error, 0.39%), respectively. Overall, 92% and 94% of the observed concentrations were encompassed by the 95% prediction intervals for lopinavir and ritonavir, respectively, which is indicative of an adequate model. Predictions of concentrations from an external data set (HIV infected) (n = 12) satisfied predictive performance criteria. Simulated lopinavir exposures at lopinavir-ritonavir doses of 200 mg-150 mg and 200 mg-50 mg twice daily were 38% and 65% lower, respectively, than that of the standard dose. The model allows a better understanding of the interaction between lopinavir and ritonavir and may allow a better prediction of lopinavir concentrations and assessments of different dosing strategies.

Can therapeutic drug monitoring improve pharmacotherapy of HIV infection in adolescents?

Currently, therapeutic drug monitoring (TDM) of antiretroviral therapy (ART) is not performed in the United States as part of routine clinical care of an HIV-infected adolescent patient. TDM is recommended to rule out subtherapeutic drug concentrations and to differentiate among malabsorption, drug interactions, poor adherence, or increased drug metabolism or clearance as possible causes of decreased drug exposure. The use of TDM is also considered to assist in finding the optimal dose of a drug in patients whose virus has shown reduced susceptibility to that drug. The dosing of antiretroviral (ARV) drugs in adolescent patients with HIV infection depends on the chronologic age, weight, height, and the stage of sexual maturation. As a result of the limited data on the pharmacokinetics of ART during puberty, the transition of a dosing regimen from higher pediatric (weight and surface-based) to adult (fixed) range is not well defined. Developmental pharmacokinetic differences contribute to high variability in pediatric and adolescent patients and an increased frequency of suboptimal ARV exposure as compared to in adults. Individualized, concentration-targeted optimal dosing of ARV medications can be beneficial to patients for whom only limited dosing guidelines are available. This article describes three cases of the application of TDM in treatment-experienced adolescent patients whose ART was optimized using ARV TDM. TDM of ARV drugs is useful in managing the pharmacotherapy of HIV in adolescent patients and is well received by the adolescent patients with HIV and their families. Among others, the benefits of TDM provide evidence for adherence interventions and create grounds for enhanced education of the adolescent patient and involved adult caregivers about ART. Finally, TDM in adolescents provides valuable information about the clinical pharmacology of ART during puberty.

Population pharmacokinetics of lopinavir in combination with rifampicin-based antitubercular treatment in HIV-infected South African children

PURPOSE

The population pharmacokinetics (PK) of lopinavir in tuberculosis (TB)/human immunodeficiency virus (HIV) co-infected South African children taking super-boosted lopinavir (lopinavir/ritonavir ratio 1:1) as part of antiretroviral treatment in the presence of rifampicin were compared with the population PK of lopinavir in HIV-infected South African children taking standard doses of lopinavir/ritonavir (ratio 4:1).

METHODS

Lopinavir concentrations were measured in 15 TB/HIV-co-infected paediatric patients who were sampled during and after rifampicin-based TB treatment and in 15 HIV-infected children without TB. During TB therapy, the dose of ritonavir was increased to lopinavir/ritonavir 1:1 in order to compensate for the induction of rifampicin. The children received median (interquartile range=IQR) doses of lopinavir 292 mg/m(2) (274, 309) and ritonavir 301 mg/m(2) (286, 309) twice daily. After TB treatment completion the children received standard doses of lopinavir/ritonavir 4:1 (median [IQR] lopinavir dose 289 mg/m(2) [286, 303] twice daily) as did those without TB (median [IQR] lopinavir dose 265 mg/m(2) [249, 289] twice daily).

RESULTS

Lopinavir oral clearance (CL/F) was about 30% lower in children without TB than in co-infected children treated with super-boosted lopinavir. However, the predicted lopinavir C(min) was above the recommended minimum therapeutic concentration during TB/HIV co-treatment in the 15 children. Lopinavir CL/F increased linearly during the dosing interval.

CONCLUSIONS

Increasing the ritonavir dose to achieve a lopinavir/ritonavir ratio of 1:1 when given in combination with rifampicin-based TB treatment did not completely compensate for the enhancement of lopinavir CL/F caused by rifampicin. The time-dependent lopinavir CL/F might be due to a time-dependent recovery from ritonavir inhibition of lopinavir metabolism during the dosing interval.

Age-related changes in plasma concentrations of the HIV protease inhibitor lopinavir

The advent of highly active antiretroviral therapy in the treatment of HIV disease has substantially extended the lifespan of individuals infected with HIV resulting in a growing population of older HIV-infected individuals. The efficacy and safety of antiretroviral agents in the population are important concerns. There have been relatively few studies assessing antiretroviral pharmacokinetics in older patients. Thirty-seven subjects aged 18-30 years and 40 subjects aged 45-79 years, naive to antiretroviral therapy, received lopinavir/ritonavir (400/100) bid, emtricitibine 200 mg qd, and stavudine 40 mg bid. Trough lopinavir concentrations were available for 44 subjects, collected at 24, 36, and 96 weeks. At week 24, older age was associated with higher lopinavir trough concentrations, and a trend was observed toward older age being associated with higher lopinavir trough concentrations when all time points were evaluated. In the young cohort, among subjects with two or more measurements, there was a trend toward increasing intrasubject trough lopinavir concentrations over time. Using a nonlinear, mixed-effects population pharmacokinetic model, age was negatively associated with lopinavir clearance after adjusting for adherence. Adherence was assessed by patient self-reports; older patients missed fewer doses than younger patients (p = 0.02). No difference in grade 3-4 toxicities was observed between the two age group. Older patients have higher trough lopinavir concentrations and likely decreased lopinavir clearance. Age-related changes in the pharmacokinetics of antiretroviral drugs may be of increasing importance as the HIV-infected population ages and as older individuals comprise an increasing proportion of new diagnoses.

Pharmacokinetics of lopinavir-ritonavir with and without nonnucleoside reverse transcriptase inhibitors in Ugandan HIV-infected adults

We evaluated the pharmacokinetics of lopinavir-ritonavir with and without nonnucleoside reverse transcriptase inhibitors (NNRTIs) in Ugandan adults. The study design was a three-period crossover study (3 tablets [600 mg of lopinavir/150 mg of ritonavir {600/150 mg}], 4 capsules [533/133 mg], and 2 tablets [400/100 mg] twice a day [BD]; n = 40) of lopinavir-ritonavir with NNRTIs and a parallel one-period study (2 tablets BD; n = 20) without NNRTIs. Six-point pharmacokinetic sampling (0, 2, 4, 6, 8, and 12 h) was undertaken after observed intake with a standardized breakfast. Ugandan DART trial participants receiving efavirenz (n = 20), nevirapine (n = 18), and no NNRTI (n = 20) had median ages of 41, 35, and 37 years, respectively, and median weights of 60, 64, and 63 kg, respectively. For the no-NNRTI group, the geometric mean (percent coefficient of variation [%CV]) lopinavir area under the concentration-time curve from 0 to 12 h (AUC(0-12)) was 110.1 (34%) microg x h/liter. For efavirenz, the geometric mean lopinavir AUC(0-12) (%CV) values were 91.8 microg x h/liter (58%), 65.7 microg x h/liter (39%), and 54.0 microg x h/liter (65%) with 3 tablets, 4 capsules, and 2 tablets BD, respectively, with corresponding (within-individual) geometric mean ratios (GMR) for 3 and 2 tablets versus 4 capsules of 1.40 (90% confidence interval [CI], 1.18 to 1.65; P = 0.002) and 0.82 (90% CI, 0.68 to 0.99; P = 0.09), respectively, and the apparent oral clearance (CL/F) values were reduced by 58% and 1%, respectively. For nevirapine, the geometric mean lopinavir AUC(0-12) (%CV) values were 112.9 microg x h/liter (30%), 68.1 microg x h/liter (53%), and 61.5 microg x h/liter (52%), respectively, with corresponding GMR values of 1.66 (90% CI, 1.46 to 1.88; P < 0.001) and 0.90 (90% CI, 0.77 to 1.06; P = 0.27), respectively, and the CL/F was reduced by 57% and 7%, respectively. Higher values for the lopinavir concentration at 12 h (C(12)) were observed with 3 tablets and efavirenz-nevirapine (P = 0.04 and P = 0.0005, respectively), and marginally lower C(12) values were observed with 2 tablets and efavirenz-nevirapine (P = 0.08 and P = 0.26, respectively). These data suggest that 2 tablets of lopinavir-ritonavir BD may be inadequate when dosed with NNRTIs in Ugandan adults, and the dosage should be increased by the addition of an additional adult tablet or a half-dose tablet (100/25 mg), where available.

Pharmacokinetics and pharmacodynamics of GS-9350: a novel pharmacokinetic enhancer without anti-HIV activity

GS-9350 is a new chemical entity under development as a potent, mechanism-based inhibitor of human cytochrome P450 3A (CYP3A) isoforms. Its intended use is to increase the systemic exposure of coadministered agents that are metabolized by CYP3A enzymes. Unlike ritonavir, which is in current clinical use for this purpose, GS-9350 is devoid of anti-HIV activity. The pharmacokinetics of GS-9350 and its efficacy in increasing systemic exposure of the probe CYP3A substrate midazolam were examined in a study involving single- and multiple-dose escalations of GS-9350 from 50 to 400 mg. Single-dose escalation from 50 to 400 mg resulted in a 164-fold increase in GS-9350 exposure, whereas multiple-dose escalation in the dosage range of 50-300 mg resulted in a 47-fold increase in exposure. GS-9350 potently inhibited midazolam apparent clearance (95% reduction), similar in effect to ritonavir 100 mg. GS-9350 was generally well tolerated at all doses, and there was no evidence of dose-limiting toxicity. Establishing proof-of-concept, GS-9350 is currently under phase II development as a potential alternative to ritonavir for use with antiretroviral agents (including the HIV integrase inhibitor elvitegravir) that are often prescribed along with a "booster" drug.

Saquinavir exposure in HIV-infected patients with chronic viral hepatitis

OBJECTIVES

The aim of this study was to assess the influence of hepatitis B virus or hepatitis C virus co-infection and the extent of liver fibrosis on saquinavir and ritonavir pharmacokinetics in HIV-infected subjects without liver function impairment.

METHODS

A cross-sectional, comparative study enrolling HIV-infected adults receiving saquinavir/ritonavir 1000/100 mg twice daily or 1500/100 mg once daily was conducted. Patients with chronic viral hepatitis (HEP+) were grouped as having advanced liver fibrosis (HEP+/FIB+) or not (HEP+/FIB-) based on the FIB-4 index. Saquinavir and ritonavir trough concentrations (C(trough)) in plasma were determined by HPLC. The geometric mean ratio (GMR) was used to compare saquinavir and ritonavir C(trough) between HEP- and HEP+ patients, and the influence of the extent of liver fibrosis on saquinavir and ritonavir pharmacokinetics was explored using analysis of variance.

RESULTS

One hundred and thirty-eight patients on twice-daily saquinavir/ritonavir (67 HEP-, 71 HEP+) and 36 patients on once-daily saquinavir/ritonavir (12 HEP-, 24 HEP+) were included. Saquinavir C(trough) was comparable between HEP- and HEP+ patients receiving either saquinavir/ritonavir 1000/100 mg twice daily [GMR 0.91, 95% confidence interval (CI) 0.60-1.37; P = 0.655] or 1500/100 mg once daily (GMR 0.88, 95% CI 0.39-1.97; P = 0.752). Similarly, ritonavir C(trough) was also comparable between HEP- and HEP+ patients. The extent of liver fibrosis was not significantly related to saquinavir or ritonavir C(trough) in patients receiving either of the two studied doses.

CONCLUSIONS

Saquinavir C(trough) was not increased in HIV-infected patients with chronic viral hepatitis in the absence of liver function impairment. These results confirm that no specific dose modification of saquinavir/ritonavir should be recommended in this setting.