Effect of food on the pharmacokinetics of the WEE1 inhibitor adavosertib (AZD1775) in patients with advanced solid tumors.

PURPOSE: To support future dosing recommendations, the effect of food on the pharmacokinetics of adavosertib, a first-in-class, small-molecule reversible inhibitor of WEE1 kinase, was assessed in patients with advanced solid tumors. METHODS: In this Phase I, open-label, randomized, two-period, two-sequence crossover study, the pharmacokinetics of a single 300 mg adavosertib dose were investigated in fed versus fasted states. RESULTS: Compared with the fasted state, a high-fat, high-calorie meal (fed state) decreased adavosertib maximum plasma concentration (Cmax) by 16% and systemic exposure (area under the plasma concentration-time curve [AUC]) by 6%; AUC0-t decreased by 7% and time to maximum plasma concentration was delayed by 1.97 h (P = 0.0009). The 90% confidence interval of the geometric least-squares mean treatment ratio for AUC and AUC0-t was contained within the no-effect limits (0.8-1.25), while that of Cmax crossed the lower bound of the no-effect limits. Adverse events (AEs) related to adavosertib treatment were reported by 20 (64.5%) of the 31 patients treated in this study. Grade ≥ 3 AEs were reported by four (12.9%) patients (one in the fed state, three in the fasted state); two of these AEs were considered treatment-related by the investigator. Three serious AEs were reported in three (9.7%) patients; these were not considered treatment-related. No patients discontinued because of treatment-related AEs, and no new safety signals were reported. CONCLUSION: A high-fat meal did not have a clinically relevant effect on the systemic exposure of adavosertib, suggesting that adavosertib can be administered without regard to meals.

Phase I trial of TAK-385 in hormone treatment-naïve Japanese patients with nonmetastatic prostate cancer.

This open-label, phase I dose-finding study evaluated the gonadotropin-releasing hormone antagonist, TAK-385, in Japanese patients with nonmetastatic prostate cancer. In a two-part design, patients received daily oral TAK-385 at doses of 320 (loading, day 1)/80 (maintenance, day 2 and thereafter), 320/120, 320/160, or 360/120 mg for 28 days in a dose-escalation phase (part A, n = 13), and at 320/80 or 320/120 mg for up to 96 weeks in a randomized expansion phase (part B, n = 30). Primary endpoint in both parts was safety, including dose-limiting toxicity in part A. Secondary endpoints included pharmacokinetics, pharmacodynamics, and prostate-specific antigen concentration. Ten (77%) patients in part A and all patients in part B experienced an adverse event; hot flush (part A, n = 4; part B, n = 15), viral upper respiratory tract infection (part A, n = 1; part B, n = 10), and diarrhea (part B, n = 8) were most frequent. No dose-limiting toxicities were observed (part A). In 12 evaluable patients (part A), TAK-385 was rapidly absorbed after a single loading dose; on day 28 (maintenance dose), median steady-state Tmax was ~1-2 hours and mean t1/2z was 67-79 hours. All doses rapidly reduced testosterone concentrations to castration levels within 1 week. Durable reductions in prostate-specific antigen of >90% from baseline were observed through 96 weeks. TAK-385 appeared tolerable and resulted in sustained reductions in testosterone to castration levels at all doses. The lowest loading/maintenance dose required for a clinical effect was 320/80 mg. ClinicalTrials.gov: NCT02141659.

Development and validation of a liquid chromatography tandem mass spectrometry assay for AZD3965 in mouse plasma and tumor tissue: Application to pharmacokinetic and breast tumor xenograft studies.

AZD3965, a pyrole pyrimidine derivative, is a potent and orally bioavailable inhibitor of monocarboxylate transporter 1 (MCT1), currently in a Phase I clinical trial in UK for lymphomas and solid tumors. There is currently no published assay for AZD3965. The objectives of this study were to develop and validate a LC/MS/MS assay for quantifying AZD3965 in mouse plasma and tumor tissue. Protein precipitation with 0.1% formic acid in acetonitrile was used for sample preparation. Chromatographic separation was achieved on a C18 column followed by tandem mass spectrometry detection in multiple reaction monitoring mode with utilizing Atmospheric Pressure Chemical Ionization. AR-C155858 was used as the internal standard. The inter-day and intra-day precision and accuracy of quality control samples evaluated in plasma and tumor tissue were less than ±7% of the nominal concentrations. The extraction recovery, matrix effect and stability values were all within acceptable levels. Sample dilution integrity, accessed by diluting plasma spiked with AZD3965 10-fold with blank plasma, was 101%. The lower limit of quantification (LLOQ) and upper limit of quantification (ULOQ) were 0.15 ng/mL and 12 µg/mL, respectively, in plasma. The assay of AZD3965 in tumor tissue was also validated with good precision and accuracy. The LLOQ was 0.15 ng/mL in tumor tissue. This assay was successfully applied to pharmacokinetic and murine 4T1 breast tumor xenograft studies of AZD3965 in mice.

Quantification of the next-generation oral anti-tumor drugs dabrafenib, trametinib, vemurafenib, cobimetinib, pazopanib, regorafenib and two metabolites in human plasma by liquid chromatography-tandem mass spectrometry.

A sensitive and selective method of high performance liquid chromatography (HPLC) coupled to tandem mass spectrometry (MS/MS) has been developed for the simultaneous quantification of six anticancer protein kinase inhibitors (PKIs), dabrafenib, trametinib, vemurafenib, cobimetinib, pazopanib, regorafenib, and two active metabolites (regorafenib-M2 and regorafenib-M5) in human plasma. Plasma protein precipitation with methanol enables the sample extraction of 100 µL aliquot of plasma. Analytes are detected by electrospray triple-stage quadrupole mass spectrometry and quantified using the calibration curves with stable isotope-labeled internal standards. The method was validated based on FDA recommendations, including assessment of extraction yield (74-104%), matrix effects, analytical recovery (94-104%) with low variability (<15%). The method is sensitive (lower limits of quantification within 1 to 200 ng/mL), accurate (intra- and inter-assay bias: -0.3% to +12.7%, and -3.2% to +6.3%, respectively) and precise (intra- and inter-assay CVs within 0.7-7.3% and 2.5-8.0%, respectively) over the clinically relevant concentration range (upper limits of quantification 500 to 100,000 ng/mL). This method is applied in our laboratory for both clinical research programs and routine therapeutic drug monitoring service of PKIs.

A simple and sensitive HPLC-MS/MS method for quantification of eggmanone in rat plasma and its application to pharmacokinetics.

Allosteric phosphodiesterase 4 (PDE4) inhibitors are highly sought after due to their important anti-inflammatory and anti-cancer therapeutic effects. We recently identified Eggmanone, an extraordinarily selective allosteric PDE4 inhibitor displaying favorable drug properties. However, a specific analytic method of Eggmanone in serum and its pharmacokinetics have not been reported yet. In this study, we developed a rapid and sensitive high performance liquid chromatography-mass spectrometric (HPLC-MS/MS) method to determine Eggmanone concentrations in rat plasma. This assay method was validated in terms of specificity, linearity, sensitivity, accuracy, precision, matrix effect, recovery and stability, and was applied to a pharmacokinetic study in rats following intravenous injection of Eggmanone at doses of 1 and 3 mg/kg. The lower limit of quantification (LLOQ) of this assay was 5 ng/mL and the linear calibration curve was acquired with R2 > 0.99 between 5 and 1000 ng/m. The intra-day and inter-day precision was evaluated with the coefficient of variations less than 11.09%, whereas the mean accuracy ranged from 98.38% to 105.13%. The assay method exhibited good recovery and negligible matrix effect. The samples were stable under all the experimental conditions. The plasma concentrations of Eggmanone were detected and quantified over 24 h with the terminal elimination half-live of 3.57 ±â€¯1.80 h and 5.92 ±â€¯3.34 h for the low dose (1 mg/kg) and high dose (3 mg/kg) respectively. In summary, the present method provides a robust, fast and sensitive analytical approach for quantification of Eggmanone in plasma and was successfully applied to a pharmacokinetic study in rats.

An UPLC-MS/MS method for the quantification of BRAF inhibitors (vemurafenib, dabrafenib) and MEK inhibitors (cobimetinib, trametinib, binimetinib) in human plasma. Application to treated melanoma patients.

Targeted therapies for cancers are fast-growing therapies. For instance kinase inhibitors such as BRAF inhibitors (BRAFi) and MEK inhibitors (MEKi) are increasingly used to treat malignant melanoma. The metabolic profile of these drugs can result in great interindividual variability, justifying therapeutic drug monitoring (TDM). We describe a rapid and specific method for quantification of 2 BRAFi (vemurafenib, dabrafenib) and 3 MEKi (cobimetinib, trametinib and binimetinib). Chromatography was performed on a Waters Acquity-UPLC system with CORTECS C18+ column, under a gradient of 10% acetic acid in water/acetonitrile. An Acquity-TQD® with electrospray ionization was used for detection. Samples were prepared by solid phase extraction (Oasis® MCX microElution) before injection in the system. Calibration curves ranges from 0.4 to 100µg/ml for vemurafenib, from 1 to 1000ng/ml for dabrafenib, from 0.5 to 500ng/ml for cobimetinib and binimetinib, and from 0.75 to 250ng/ml for trametinib. At all concentrations the bias was within ±15% of the nominal concentrations and precision was ≤15%. All results were within the acceptance criteria of the EMA guidelines on method validation. This rapid, sensitive and specific UPLC-MS/MS method can perform simultaneous quantification of targeted therapies used in malignant melanoma and is usable for routine TDM.

Lead optimization of a pyrazolo[1,5-a]pyrimidin-7(4H)-one scaffold to identify potent, selective and orally bioavailable KDM5 inhibitors suitable for in vivo biological studies.

Starting with a lead [1,5-a]pyrimidin-7(4H)-one-containing molecule (1), we generated potent, selective and orally bioavailable KDM5 inhibitors. Using structure- and property-based approaches, we designed 48 with improved cell potency (PC9 H3K4Me3 EC50=0.34µM). Furthermore, 48 maintained suitable physiochemical properties and displayed an excellent pharmacokinetic (PK) profile in mice. When dosed orally in mice at 50mg/kg twice a day (BID), 48 showed an unbound maximal plasma concentration (Cmax) >15-fold over its cell EC50, thereby providing a robust chemical probe for studying KDM5 biological functions in vivo.

Lipoprotein-associated phospholipase A2 (Lp-PLA2) as a therapeutic target to prevent retinal vasopermeability during diabetes.

Lipoprotein-associated phospholipase A2 (Lp-PLA2) hydrolyses oxidized low-density lipoproteins into proinflammatory products, which can have detrimental effects on vascular function. As a specific inhibitor of Lp-PLA2, darapladib has been shown to be protective against atherogenesis and vascular leakage in diabetic and hypercholesterolemic animal models. This study has investigated whether Lp-PLA2 and its major enzymatic product, lysophosphatidylcholine (LPC), are involved in blood-retinal barrier (BRB) damage during diabetic retinopathy. We assessed BRB protection in diabetic rats through use of species-specific analogs of darapladib. Systemic Lp-PLA2 inhibition using SB-435495 at 10 mg/kg (i.p.) effectively suppressed BRB breakdown in streptozotocin-diabetic Brown Norway rats. This inhibitory effect was comparable to intravitreal VEGF neutralization, and the protection against BRB dysfunction was additive when both targets were inhibited simultaneously. Mechanistic studies in primary brain and retinal microvascular endothelial cells, as well as occluded rat pial microvessels, showed that luminal but not abluminal LPC potently induced permeability, and that this required signaling by the VEGF receptor 2 (VEGFR2). Taken together, this study demonstrates that Lp-PLA2 inhibition can effectively prevent diabetes-mediated BRB dysfunction and that LPC impacts on the retinal vascular endothelium to induce vasopermeability via VEGFR2. Thus, Lp-PLA2 may be a useful therapeutic target for patients with diabetic macular edema (DME), perhaps in combination with currently administered anti-VEGF agents.

Simultaneous quantification of dabrafenib and trametinib in human plasma using high-performance liquid chromatography-tandem mass spectrometry.

Dabrafenib (Tafinlar(®)) and trametinib (Mekinist(®)) are registered for the treatment of patients with BRAF V600 mutation positive unresectable or metastatic melanoma. To support therapeutic drug monitoring (TDM) and clinical pharmacological trials, an assay to simultaneously quantify dabrafenib and trametinib in human plasma using liquid chromatography tandem mass spectrometry was developed and validated. Human plasma samples were collected on an outpatient base and stored at nominally -20°C. Analytes and internal standards (stable isotope labeled compounds) were extracted with TBME. After snap freezing the samples in a dry ice-ethanol bath, the organic layer was transferred to a clean tube and evaporated under a gentle stream of nitrogen gas. The dry extract was then reconstituted with 100µL acetonitrile and 5µL of the final extract was injected and separated on a C18 column with gradient elution, and analyzed with triple quadrupole mass spectrometry in positive-ion mode. The validated assay ranges from 50 to 5000ng/mL for dabrafenib and 0.5-50ng/mL for trametinib were linear, and correlation coefficient (r(2)) of 0.996 or better. At all concentrations of both analytes the biases were within ±15% of the nominal concentrations and precisions were ≤15%. All results were within the acceptance criteria of the latest US FDA guidance and EMA guidelines on method validation. Dabrafenib was found to degrade under the influence of light in different organic solvents and at least seven degradation products were detected. In conclusion, the described method to simultaneously quantify dabrafenib and trametinib in human plasma was successfully validated and applied for therapeutic drug monitoring in cancer patients treated with dabrafenib and trametinib.

Activity of the oral mitogen-activated protein kinase kinase inhibitor trametinib in RAS-mutant relapsed or refractory myeloid malignancies.

BACKGROUND: RAS/RAF/mitogen-activated protein kinase activation is common in myeloid malignancies. Trametinib, a mitogen-activated protein kinase kinase 1 (MEK1)/MEK2 inhibitor with activity against multiple myeloid cell lines at low nanomolar concentrations, was evaluated for safety and clinical activity in patients with relapsed/refractory leukemias. METHODS: This phase 1/2 study accrued patients with any relapsed/refractory leukemia in phase 1. In phase 2, this study accrued patients with relapsed/refractory acute myeloid leukemia (AML) or high-risk myelodysplastic syndromes (MDS) with NRAS or KRAS mutations (cohort 1); patients with AML, MDS, or chronic myelomonocytic leukemia (CMML) with a RAS wild-type mutation or an unknown mutation status (cohort 2); and patients with CMML with an NRAS or KRAS mutation (cohorts 3). RESULTS: The most commonly reported treatment-related adverse events were diarrhea, rash, nausea, and increased alanine aminotransferase levels. The phase 2 recommended dose for Trametinib was 2 mg orally daily. The overall response rates were 20%, 3%, and 27% for cohorts 1, 2, and 3, respectively, and this indicated preferential activity among RAS-mutated myeloid malignancies. Repeated cycles of trametinib were well tolerated with manageable or reversible toxicities; these results were similar to those of other trametinib studies. CONCLUSIONS: The selective, single-agent activity of trametinib against RAS-mutated myeloid malignancies validates its therapeutic potential. Combination strategies based on a better understanding of the hierarchical role of mutations and signaling in myeloid malignancies are likely to improve the response rate and duration. Cancer 2016;122:1871-9. © 2016 American Cancer Society.

Relative bioavailability of pediatric oral solution and tablet formulations of trametinib in adult patients with solid tumors.

Trametinib (Mekinist®) is a selective inhibitor of mitogen-activated protein kinase kinase (MEK) approved in the United States as a single agent and in combination with dabrafenib (Tafinlar®) for treatment of patients with unresectable or metastatic melanoma with a positive BRAF V600E/V600K mutation for which a pediatric oral solution formulation is being developed. This open-label, two-period, two-treatment, randomized, crossover study assessed the relative bioavailability of the trametinib pediatric oral solution compared to the tablet formulation after a single-dose administration to adult patients with solid tumors. Primary pharmacokinetic endpoints derived from standard non-compartmental methods were AUC0-inf , AUC0-t , and Cmax . As expected, Cmax was higher and Tmax earlier for the pediatric oral solution compared to the tablet formulation. Administration of the trametinib pediatric oral solution resulted in a 12%, 10%, 18%, and 71% higher AUC0-inf , AUC0-last , AUC0-24 , and Cmax , respectively, as compared to the tablet formulation. Safety results were aligned with the known safety profile of trametinib. No serious or non-serious adverse events resulted in study drug withdrawal. Palatability of the pediatric oral solution was evaluated and found to be acceptable to most adult patients, but may differ in the pediatric population.

Evaluation of the effects of food on the single-dose pharmacokinetics of trametinib, a first-in-class MEK inhibitor, in patients with cancer.

The aim of this study was to estimate the effect of a high-fat, high-calorie meal on the single-dose pharmacokinetics (PK) of trametinib, a MEK inhibitor. The design of this 2 treatment, 2 period crossover, incomplete wash-out study was influenced by the subject population, long half-life and PK variability; 24 subjects were randomized to a single, oral 2 mg trametinib dose administered in a fed/fasted state, followed by 7 days of serial PK sampling. Period 2 PK parameters were adjusted based on residual Period 1 concentrations. Geometric least square mean ratios of fed:fasted were 0.30, 0.76, and 0.90 for corrected maximum concentration (C(max)), area under concentration-time curve from time 0 to last quantifiable sample (AUC(0-last)) and AUC from time 0 extrapolated to infinity (AUC(0-α)), respectively. Median half-life was 6.3 and 5.3 days for fed and fasted regimens, respectively. Uncorrected PK parameters were consistent with these results. Food delayed absorption and had a mean difference in time of maximum concentration (t(max)) of 3.9 hours. Both oral trametinib doses were well-tolerated. Single-dose trametinib administration with food decreased the rate and, to a lesser degree, the extent of absorption, supporting the recommendation to administer trametinib 1 hour before or 2 hours after a meal.

Phase II study of the MEK1/MEK2 inhibitor Trametinib in patients with metastatic BRAF-mutant cutaneous melanoma previously treated with or without a BRAF inhibitor.

PURPOSE: BRAF mutations promote melanoma cell proliferation and survival primarily through activation of MEK. The purpose of this study was to determine the response rate (RR) for the selective, allosteric MEK1/MEK2 inhibitor trametinib (GSK1120212), in patients with metastatic BRAF-mutant melanoma. PATIENTS AND METHODS: This was an open-label, two-stage, phase II study with two cohorts. Patients with metastatic BRAF-mutant melanoma previously treated with a BRAF inhibitor (cohort A) or treated with chemotherapy and/or immunotherapy (BRAF-inhibitor naive; cohort B) were enrolled. Patients received 2 mg of trametinib orally once daily. RESULTS: In cohort A (n = 40), there were no confirmed objective responses and 11 patients (28%) with stable disease (SD); the median progression-free survival (PFS) was 1.8 months. In cohort B (n = 57), there was one (2%) complete response, 13 (23%) partial responses (PRs), and 29 patients (51%) with SD (confirmed RR, 25%); the median PFS was 4.0 months. One patient each with BRAF K601E and BRAF V600R had prolonged PR. The most frequent treatment-related adverse events for all patients were skin-related toxicity, nausea, peripheral edema, diarrhea, pruritis, and fatigue. No cutaneous squamous cell carcinoma was observed. CONCLUSION: Trametinib was well tolerated. Significant clinical activity was observed in BRAF-inhibitor-naive patients previously treated with chemotherapy and/or immunotherapy. Minimal clinical activity was observed as sequential therapy in patients previously treated with a BRAF inhibitor. Together, these data suggest that BRAF-inhibitor resistance mechanisms likely confer resistance to MEK-inhibitor monotherapy. These data support further evaluation of trametinib in BRAF-inhibitor-naive BRAF-mutant melanoma, including rarer forms of BRAF-mutant melanoma.

Assessing the impact of hepatitis C virus coinfection on lopinavir/ritonavir trough concentrations in HIV-infected patients.

PURPOSE: Chronic hepatitis C is an emerging issue in the management of human immunodeficiency virus (HIV) disease because both diseases have the same route of transmission, leading to a very high prevalence of hepatitis C virus (HCV)-coinfection in the HIV-positive patient population. Lopinavir is extensively metabolized by the hepatic cytochrome P450 3A4, and the pharmacokinetics of this protease inhibitor (PI) could be influenced by liver impairment. However, data currently available on the impact of HCV-coinfection on lopinavir plasma concentrations are both limited and conflicting. METHODS: This was an observational, open-label study in which adult HIV-infected outpatients on stable antiretroviral treatment that included two nucleoside reverse transcriptase inhibitors (NRTIs) plus lopinavir/ritonavir for at least 4 weeks were asked to participate. The trough plasma concentration (C (trough)) of lopinavir and ritonavir was assessed at steady state by a validated high-performance liquid chromatography-tandem mass spectrometry method. RESULTS: A total of 65 HIV-positive patients were enrolled in the study. These patients were stratified into two groups based on the absence/presence of HCV-coinfection: 45 were monoinfected (HIV+/HCV-) and 20 were coinfected (HIV+/HCV+). The lopinavir C (trough) in plasma was comparable between HIV+/HCV+ and HIV+/HCV- patients, without any statistically significant difference (geometric mean ratio 0.89, 95% confidence interval 0.61-1.42; p = 0.581). The mean ritonavir C (trough) was also comparable in the two groups. Almost all samples were found to be within the therapeutic plasma level range (97% in HIV+/HCV- group and 100% in HIV+/HCV+ group). No correlation was found between lopinavir plasma levels and adverse events (such as diarrhoea and hypertriglyceridaemia) or immune-virological parameters of HIV disease. CONCLUSIONS: Among the HIV-positive patients participating in this study, the pharmacokinetics of lopinavir/ritonavir did not significantly change in those HIV-positive patients coinfected with HCV and in the absence of liver cirrhosis.

Lopinavir loaded solid lipid nanoparticles (SLN) for intestinal lymphatic targeting.

The poor orally available lopinavir was successfully encapsulated in glyceryl behenate based solid lipid nanoparticles (Lo-SLN) for its ultimate use to target intestinal lymphatic vessels in combined chemotherapy-the so-called Highly Active Anti-Retroviral Therapy (HAART). SLN with mean particle size of 230 nm (polydispersity index, PDI<0.27) and surface electrical charge of approx. -27mV, were produced by hot homogenization process followed by ultrasonication. Particles were characterized using differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and atomic force microscopy (AFM) to confirm their solid character and the homogeneous distribution of drug within the lipid matrix. In vitro release studies at pH 6.8 phosphate buffer (PBS) and at pH 1.2 HCl 0.1N showed a slow release in both media. From the intestinal lymphatic transport study it became evident that SLN increased the cumulative percentage dose of lopinavir secreted into the lymph, which was 4.91-fold higher when compared with a conventional drug solution in methyl cellulose 0.5% (w/v) as suspending agent (Lo-MC). The percentage bioavailability was significantly enhanced. The AUC for the Lo-SLN was 2.13-fold higher than that obtained for the Lo-MC of similar concentration. The accelerated stability studies showed that there was no significant change in the mean particle size and PDI after storage at 25±2°C/60±5% RH. The shelf life of optimized formulation was assessed based on the remained drug content in the stabilized formulation and was shown to be 21.46 months.

Phase 2 and pharmacodynamic study of oral forodesine in patients with advanced, fludarabine-treated chronic lymphocytic leukemia.

Forodesine is a new and potent purine nucleoside phosphorylase (PNP) inhibitor. Patients with chronic lymphocytic leukemia (CLL) with primary resistance to fludarabine-based therapy or with progressive disease were eligible for oral forodesine (200 mg/d) for up to 24 weeks. Eight patients with median lymphocyte count of 35.9 x 10(9)/L and median serum beta2 microglobulin level of 6.45 mg/L were treated. Six had Rai stage III to IV and were previously heavily treated (median prior therapy = 5). Two had transient decrease in lymphocyte count to normal, whereas in 5, disease progressed. Adverse events were mild. Steady-state level of forodesine ranged from 200 to 1300 nM and did not reach desired 2 microM level. PNP inhibition ranged from 57% to 89% and steady-state 2'-deoxyguanosine (dGuo) concentration median was 1.8 microM. Intracellular deoxyguanosine triphosphate (dGTP) increase was very modest, from median of 6 microM to 10 microM. Compared with in vivo, in vitro incubations of CLL lymphocytes with 10 or 20 microM dGuo and forodesine (2 microM) resulted in accumulation of higher levels of dGTP (40-250 microM) which resulted in increase in apoptosis. Forodesine has biologic activity in CLL; pharmacodynamic parameters suggest that an alternate dosing schedule and/or higher doses to achieve greater intracellular dGTP may be beneficial in this patient population.

The impact of SLCO1B1 polymorphisms on the plasma concentration of lopinavir and ritonavir in HIV-infected men.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: * There is large interindividual variability in the pharmacokinetics of protease inhibitors (PIs) among human immunodeficiency virus (HIV)-infected individuals under highly active antiretroviral therapy. * Protease inhibitor have been recently reported to be substrates of the SLCO1B1/OATP1 drug transporter. * A single nucleotide polymorphism (SNP) in the SLCO1B1 gene (521T-->C) was associated with plasma levels of lopinavir in HIV-infected individuals. WHAT THIS STUDY ADDS: * Data on the impact of three SLCO1B1 SNPs (521T-->C, 388A-->G, 463C-->A) on the trough plasma concentration of lopinavir and ritonavir in a cohort of 99 adult HIV-infected Brazilian men under stable highly active antiretroviral therapy. * Evidence that carriers of the 521C allele display significantly higher lopinavir, but not ritonavir plasma concentrations relative to the wild-type TT genotype. * No effect of either 388A-->G or 463C-->A SNPs on lopinavir or ritonavir plasma concentrations. * Further studies are required to confirm the clinical significance of the association between the SLCO1B1521T-->C polymorphism and lopinavir pharmacokinetics. AIMS: To investigate possible associations between three SLCO1B1 single nucleotide polymorphisms (388A-->G, 463C-->A, 521T-->C) and lopinavir/ritonavir plasma concentrations. METHODS: The study included 99 human immunodeficiency virus-infected men on stable highly active antiretroviral therapy containing lopinavir/ritonavir. Trough concentrations of lopinavir and ritonavir in plasma were quantified using liquid chromatography-tandem mass spectrometry. Genotyping of SLCO1B1388A-->G, 463C-->A and 521T-->C polymorphisms was performed by allelic discrimination using real-time polymerase chain reaction. RESULTS: The trough concentration of lopinavir in plasma is significantly associated with SLCO1B1521T-->C genotypes (P= 0.03). There is a significant trend for increasing concentrations of lopinavir from TT to TC to CC genotypes (P= 0.02). Carriers of the 521C allele display significantly higher lopinavir plasma concentrations relative to the wild-type TT genotype (P= 0.03). CONCLUSIONS: Reduced uptake of lopinavir by hepatocytes in carriers of the 521C allele may account for these results, but further studies to confirm the clinical importance of SLCO1B1 polymorphisms in lopinavir pharmacokinetics are warranted.

HIV protease inhibitors are substrates for OATP1A2, OATP1B1 and OATP1B3 and lopinavir plasma concentrations are influenced by SLCO1B1 polymorphisms.

OBJECTIVE: OATP1B1 and OATP1B3 are major hepatic drug transporters whilst OATP1A2 is mainly located in the brain but is also located in liver and several other organs. These transporters affect the distribution and clearance of many endobiotics and xenobiotics and have been reported to have functional single nucleotide polymorphisms (SNPs). We have assessed the substrate specificities of these transporters for a panel of antiretrovirals and investigated the effects of SNPs within these transporters on the pharmacokinetics of lopinavir. METHODS: SLCO1A2, SLCO1B1 and SLCO1B3 were cloned, verified and used to generate cRNA for use in the Xenopuslaevis oocyte transport system. Using the oocyte system, antiretrovirals were tested for their substrate specificities. Plasma samples (n=349) from the Liverpool therapeutic drug monitoring registry were genotyped for SNPs in SLCO1A2, SLCO1B1 and SLCO1B3 and associations between SNPs and lopinavir plasma concentrations were analysed. RESULT: Antiretroviral protease inhibitors, but not non-nucleoside reverse transcriptase inhibitors, are substrates for OATP1A2, OATP1B1 and OATP1B3. Furthermore, ritonavir was not an inhibitor of OATP1B1. The 521T>C polymorphism in SLCO1B1 was significantly associated with higher lopinavir plasma concentrations. No associations were observed with functional variants of SLCO1A2 and SLCO1B3. CONCLUSION: These data add to our understanding of the factors that contribute to variability in plasma concentrations of protease inhibitors. Further studies are now required to confirm the association of SLCO1B1 521T>C with lopinavir plasma concentrations and to assess the influence of other polymorphisms in the SLCO family.

Effect of rifampicin on lopinavir pharmacokinetics in HIV-infected children with tuberculosis.

OBJECTIVE: Rifampicin dramatically reduces plasma lopinavir concentrations (coformulated with ritonavir in a 4:1 ratio). A study in healthy adult volunteers showed that this reduction could be ameliorated if additional ritonavir is given. We evaluated the effect of additional ritonavir on plasma lopinavir concentrations in HIV-infected children receiving rifampicin-based treatment for tuberculosis. METHODS: We measured plasma lopinavir concentrations in 2 parallel groups receiving combination antiretroviral therapy that included lopinavir-ritonavir, with and without rifampicin-based antitubercular treatment. Additional ritonavir was given (lopinavir/ritonavir ratio of 1:1) during antitubercular treatment. Lopinavir concentrations were determined using liquid chromatography-tandem mass spectrometry. RESULTS: There were 15 children (aged 7 months to 3.9 years) in each group. Lopinavir pharmacokinetic measures (median [interquartile range]) for children with and without rifampicin, respectively, were maximum concentration (Cmax) of 10.5 [7.1 to 14.3] versus 14.2 [11.9 to 23.5] mg/L (P = 0.018), area under the curve from 0 to 12 hours (AUC0-12) of 80.9 [50.9 to 121.7] versus 117.8 [80.4 to 176.1] mg/h/L (P = 0.036), and trough concentration (Cmin) of 3.94 [2.26 to 7.66] versus 4.64 [2.32 to 10.40] mg/L (P = 0.468). Thirteen of 15 children receiving antitubercular treatment (87%) had a lopinavir Cmin greater than the recommended minimum therapeutic concentration (1 mg/L). CONCLUSIONS: The effect of rifampicin-based antitubercular treatment on lopinavir concentrations was attenuated by adding ritonavir to rifampicin. Although the median Cmax and AUC0-12 were lowered by 26% and 31%. respectively, the Cmin was greater than the minimum recommended concentration in most children.

Factors associated with altered pharmacokinetics in substance users and non-substance users receiving lopinavir and atazanavir.

Substance use is highly prevalent in HIV-infected individuals in the United States, and clinical management is complicated by the need for antiretroviral treatment, addiction therapy, variable medication adherence, and co-morbidities. The interrelation between HIV and substance use prompted our investigation to examine substance use and self-reported medication adherence in patients receiving the HIV-1 protease inhibitors, atazanavir (ATV) or lopinavir (LPV). ATV and LPV pharmacokinetics were determined by measuring plasma concentrations in subjects with active substance use (SU group) or with no active substance use (NSU group). No difference in adherence was observed between groups (p > 0.05). The mean SU ATV trough was 0.550+/-0.45 microg/mL; the mean NSU ATV trough was 0.780+/-0.590 microg/mL (p > 0.05). The mean SU LPV trough was 4.02+/-2.39 microg/mL; the mean NSU LPV trough was 6.67+/-0.910 microg/mL (p = 0.01). Co-factors found to be associated with variation in ATV and LPV concentrations included concurrent methadone use, cigarette smoking, and substance use status. These data indicate that chronic HIV treatment may be assisted with plasma concentration monitoring to identify those patients who may require dosage modification and/or regimen adjustment in order to optimize antiretroviral effects.