Population Pharmacokinetic and Exposure-Response Analyses of Prasugrel in Pediatric Patients with Sickle Cell Anemia.

BACKGROUND AND OBJECTIVE: Prasugrel, a P2Y12 adenosine diphosphate (ADP) receptor antagonist, inhibits ADP-mediated platelet activation and aggregation in patients with sickle cell anemia (SCA). We developed a population pharmacokinetic (popPK) model in pediatric patients from 2 to <18 years of age with SCA, and performed exposure-response evaluations to characterize the effects of prasugrel in a subset of these patients who weighed 19 kg or more and experienced at least two episodes of vaso-occlusive crises (VOC) in the past year. METHODS: A three-compartment popPK model adapted from that used in adults with acute coronary syndrome was used to describe the relationship between plasma concentrations of prasugrel's active metabolite (Pras-AM) and time using data from phase II and III clinical studies in children. A VOC event rate model was developed from the phase III study to explore the exposure-response relationship between Pras-AM exposure and VOC, and included evaluation of covariates. RESULTS: The final popPK model for children with SCA provided a reasonable fit to Pras-AM plasma concentrations over time, with estimates of apparent clearance (CL/F) (172 L/h) and apparent volume of distribution (Vd/F) (51.7 L) that were comparable to previous studies in adults. The final model included weight as a covariate on both CL/F and Vd/F, and age as a covariate on CL/F. Analyses of safety (bleeding events requiring medical intervention) and efficacy (VOC event rate) variables showed no apparent relationship to model-predicted Pras-AM exposure quartiles, and no statistically significant effects of intrinsic or extrinsic factors on the VOC event rate were identified in the VOC event rate model. The effect of post hoc exposures on the VOC event rate did not reach statistical significance. CONCLUSIONS: A popPK model was developed that provided reasonable parameter estimates, goodness-of-fit diagnostics, and visual predictive checks when applied to Pras-AM plasma concentrations in pediatric patients with SCA. Post hoc exposures obtained from this model did not correlate with measures of VOC or bleeding events in this population.

The Rationale for and Clinical Pharmacology of Prasugrel 5 mg.

Prasugrel is a third-generation thienopyridine platelet P2Y12 adenosine diphosphate (ADP) receptor antagonist administered with aspirin for the treatment of patients with acute coronary syndrome (ACS) with planned percutaneous coronary intervention. Prasugrel is administered periprocedurally at an oral loading dose of 60 mg followed by daily maintenance doses (MDs) of 10 mg for most patients and 5 mg for patients weighing <60 kg or aged ≥75 years. Data from a prasugrel phase III study, TRITON-TIMI 38, suggested that a lower MD might be more suitable for patients weighing <60 kg or aged ≥75 years; subsequent pharmacokinetic and pharmacodynamic studies have indicated that prasugrel 5 mg reduced platelet reactivity in these populations to an extent similar to that of prasugrel 10 mg in heavier or younger patients. Clinical experience with prasugrel 5 mg is limited, and additional studies are needed to verify the clinical efficacy and safety of this dose in these challenging populations.

Real-time dose adjustment using point-of-care platelet reactivity testing in a double-blind study of prasugrel in children with sickle cell anaemia.

Patients with sickle cell anaemia (SCA) have vaso-occlusive crises resulting from occlusive hypoxic-ischaemic injury. Prasugrel inhibits platelet activation and aggregation involved in SCA pathophysiology. Determining Effects of Platelet Inhibition on Vaso-Occlusive Events (DOVE) was a phase 3, double-blind, randomised, placebo-controlled trial assessing prasugrel efficacy. DOVE sought to bring patients' P2Y12 reaction unit (PRU) value within a targeted range via prasugrel dose adjustments using encrypted VerifyNow P2Y12® (VN-P2Y12) point-of-care testing and an interactive voice-response system (IVRS). After PRU determination, randomised patients received 0.08 mg/kg/day prasugrel or placebo. Encrypted PRUs and IVRS provided double-blind dose adjustments to achieve a defined PRU target range of 136-231; placebo patients had mock titrations. Of 341 randomised patients, 166 placebo and 160 prasugrel patients reached the fully titrated dose (FTD). Most prasugrel patients (n=104, 65 %) remained on the initial 0.08 mg/kg dose; doses escalations occurred in 23 % of patients (n=36). Mean PRUs for the pharmacodynamic population at baseline were similar in the prasugrel (273 ± 44.9) and placebo groups (273 ± 51.7), with significant reductions in PRU (p<0.001) for prasugrel patients at the FTD and at 9 months. Concomitant use of hydroxyurea did not affect platelet reactivity at any time. The majority of prasugrel patients (n=135, 84.4 %) at the FTD were within the target range of 136-231 PRUs. Mean VN-P2Y12 percentage inhibition at baseline was similar in the prasugrel (2.8 ± 5.4 %) and placebo groups (2.0 ± 4.7 %); prasugrel patients had significant increases in inhibition (p<0.001) at FTD and at 9 months. Patients with higher PRU values at baseline required higher prasugrel doses to bring PRU within the prespecified range. DOVE is the first study to successfully employ double-blind, real-time, encrypted, point-of-care platelet testing and IVRS to dose-adjust antiplatelet therapy to a targeted range of platelet inhibition.

Impact of Increased Gastric pH on the Pharmacokinetics of Evacetrapib in Healthy Subjects.

STUDY OBJECTIVE: To examine the effect of increased gastric pH on exposure to evacetrapib, a cholesteryl ester transfer protein inhibitor evaluated for the treatment of atherosclerotic heart disease. DESIGN: Open-label, two-treatment, two-period, fixed-sequence crossover study. SETTING: Clinical research unit. SUBJECTS: Thirty-four healthy subjects. INTERVENTION: In period 1, subjects received a single oral dose of evacetrapib 130 mg on day 1, followed by 7 days of analysis for evacetrapib plasma concentrations. In period 2, subjects received a once/day oral dose of omeprazole 40 mg on days 8-20, with a single oral dose of evacetrapib 130 mg administered 2 hours after the omeprazole dose on day 14, followed by 7 days of pharmacokinetic sampling. Subjects were discharged on day 21 and returned for a follow-up visit at least 14 days after the last dose of evacetrapib in period 2. Gastric pH was measured before subjects received each evacetrapib dose. MEASUREMENTS AND MAIN RESULTS: Noncompartmental pharmacokinetic parameters were estimated from plasma concentration-time data and compared between periods 1 and 2. Geometric mean ratios with 90% confidence intervals (CIs) were reported. Safety and tolerability were also assessed. The mean age of the 34 subjects was 40.9 years; mean body mass index was 27.2 kg/m(2) . Omeprazole treatment increased mean gastric pH across all subjects by 2.80 and increased evacetrapib area under the concentration versus time curve from time zero extrapolated to infinity (AUC0-∞ ) and maximum observed drug concentration (Cmax ) by 15% (90% CI -2 to 35) and 30% (90% CI 3-63), respectively. For both parameters, the upper bound of the 90% CI of the ratio of geometric least-squares means exceeded 1.25 but was less than 2, indicating a weak interaction. To assess the effect of gastric pH on subjects who responded best to omeprazole treatment, the analyses were repeated to include only the 22 subjects whose predose gastric pH was 3.0 or lower in period 1 and 4.0 or higher in period 2. In this subpopulation, mean gastric pH increased by 4.15 during omeprazole treatment, and evacetrapib AUC0-∞ and Cmax increased by 22% (90% CI 4-42) and 35% (90% CI 1-80), respectively. Despite the small mathematical differences between the analyses, the overall effect in both was a minimal increase in evacetrapib exposure. Of 35 adverse events reported during the study, 4 (11.4%) were considered to be treatment-related, and most were mild in severity. CONCLUSION: The impact of increased gastric pH on evacetrapib pharmacokinetics would not be expected to be clinically relevant. The magnitude of change in pH did not affect the degree of the interaction.

Effect of hepatic or renal impairment on the pharmacokinetics of evacetrapib.

PURPOSE: The aim of this study is to investigate the effect of hepatic or renal impairment on the pharmacokinetics of a single 130-mg evacetrapib dose. METHODS: Two open-label, parallel-design studies in males and females with normal hepatic function or Child-Pugh mild, moderate, or severe hepatic impairment, or with normal renal function or severe renal impairment. Non-compartmental pharmacokinetic parameters were estimated from plasma concentration-time data. Evacetrapib safety and tolerability were assessed. RESULTS: Pharmacokinetic parameter estimates were comparable between controls and mildly hepatically impaired subjects. Geometric mean area under the concentration-time curve (AUC) was greater, half-life (t1/2) was longer, and maximum concentration (Cmax) was lower in subjects with moderate and severe hepatic impairment than in controls. Apparent clearance (CL/F) did not differ between controls and those with mild hepatic impairment, but CL/F decreased for moderate and severe impairment. Spearman correlation coefficient showed no relationship between CL/F and Child-Pugh score. In the renal study, AUC and t1/2 were similar between groups, while Cmax was 15 % lower in subjects with severe impairment. CL/F in severely renally impaired subjects differed by <6 % from that in controls. Spearman correlation coefficient showed no apparent relationship between CL/F and estimated creatinine clearance or glomerular filtration rate. Neither study noted changes in clinical laboratory parameters or clinically significant findings. Adverse event incidence was low, and all were mild or moderate in severity. CONCLUSION: Evacetrapib exposure did not differ between mild hepatic impairment and normal hepatic function, but increased along the progression from mild to moderate to severe hepatic impairment. Severe renal impairment did not affect evacetrapib exposure.

Amount of Testosterone on Laundered Clothing After Use of Testosterone Topical 2% Solution by Healthy Male Volunteers.

INTRODUCTION: Testosterone 2% solution (Axiron) applied to armpit(s) is used for replacement therapy in men with a deficiency of endogenous testosterone. AIM: To determine the amount of testosterone on subjects' T-shirts 12 hours after applying testosterone solution, the residual testosterone on subjects' T-shirts after laundering, and the testosterone transferred to unworn textile items during laundering with worn T-shirts. METHODS: Healthy males ≥18 years old applied 2 × 1.5 mL of testosterone 2% solution to both axillae (total testosterone dose: 120 mg) and dressed in cotton long-sleeved T-shirts after a ≥3-minute waiting period. T-shirts were worn 12 hours before being removed and cut into halves, after which a 10 × 10 cm sample of each armpit area was excised for testosterone quantification before or after laundering with samples of unworn textiles. MAIN OUTCOME MEASURES: Testosterone on worn T-shirts before and after laundering, and on unworn textiles laundered with the worn T-shirts. RESULTS: Twelve subjects enrolled and completed, with only minor adverse events. Mean testosterone in unwashed worn T-shirts was 7603 µg, with high between-subject variability (3359 µg to 13,069 µg), representing 13% of the dose to 1 armpit. Mean testosterone in worn, laundered T-shirts was 260 µg (7.55 µg to 1343 µg), representing 3% of the dose to 1 armpit. Mean transferred testosterone to other textiles during laundering ranged from 69 µg on texturized Dacron 56T Double to 10,402 µg on 87/13 nylon/Lycra knit, representing 0.0382% to 5.78% of the dose to 1 armpit. CONCLUSION: Thirteen percent of the testosterone applied to axillae was transferred to T-shirts during wear. Ninety-seven percent of the transferred testosterone was removed from the T-shirts during washing, some of which was then absorbed to various degrees by other textiles. Clinical implications of these findings and biological activity of the remaining/transferred testosterone are unknown.

Absolute bioavailability of evacetrapib in healthy subjects determined by simultaneous administration of oral evacetrapib and intravenous [(13) C8 ]-evacetrapib as a tracer.

This open-label, single-period study in healthy subjects estimated evacetrapib absolute bioavailability following simultaneous administration of a 130-mg evacetrapib oral dose and 4-h intravenous (IV) infusion of 175 µg [(13) C8 ]-evacetrapib as a tracer. Plasma samples collected through 168 h were analyzed for evacetrapib and [(13) C8 ]-evacetrapib using high-performance liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameter estimates following oral and IV doses, including area under the concentration-time curve (AUC) from zero to infinity (AUC[0-∞]) and to the last measureable concentration (AUC[0-tlast ]), were calculated. Bioavailability was calculated as the ratio of least-squares geometric mean of dose-normalized AUC (oral : IV) and corresponding 90% confidence interval (CI). Bioavailability of evacetrapib was 44.8% (90% CI: 42.2-47.6%) for AUC(0-∞) and 44.3% (90% CI: 41.8-46.9%) for AUC(0-tlast ). Evacetrapib was well tolerated with no reports of clinically significant safety assessment findings. This is among the first studies to estimate absolute bioavailability using simultaneous administration of an unlabeled oral dose with a (13) C-labeled IV microdose tracer at about 1/1000(th) the oral dose, with measurement in the pg/mL range. This approach is beneficial for poorly soluble drugs, does not require additional toxicology studies, does not change oral dose pharmacokinetics, and ultimately gives researchers another tool to evaluate absolute bioavailability.

Evacetrapib: in vitro and clinical disposition, metabolism, excretion, and assessment of drug interaction potential with strong CYP3A and CYP2C8 inhibitors.

Evacetrapib is an investigational cholesteryl ester transfer protein inhibitor (CETPi) for reduction of risk of major adverse cardiovascular events in patients with high-risk vascular disease. Understanding evacetrapib disposition, metabolism, and the potential for drug-drug interactions (DDI) may help guide prescribing recommendations. In vitro, evacetrapib metabolism was investigated with a panel of human recombinant cytochromes P450 (CYP). The disposition, metabolism, and excretion of evacetrapib following a single 100-mg oral dose of (14)C-evacetrapib were determined in healthy subjects, and the pharmacokinetics of evacetrapib were evaluated in the presence of strong CYP3A or CYP2C8 inhibitors. In vitro, CYP3A was responsible for about 90% of evacetrapib's CYP-associated clearance, while CYP2C8 accounted for about 10%. In the clinical disposition study, only evacetrapib and two minor metabolites circulated in plasma. Evacetrapib metabolism was extensive. A mean of 93.1% and 2.30% of the dose was excreted in feces and urine, respectively. In clinical DDI studies, the ratios of geometric least squares means for evacetrapib with/without the CYP3A inhibitor ketoconazole were 2.37 for area under the curve (AUC)(0-∞) and 1.94 for C max. There was no significant difference in evacetrapib AUC(0-τ) or C max with/without the CYP2C8 inhibitor gemfibrozil, with ratios of 0.996 and 1.02, respectively. Although in vitro results indicated that both CYP3A and CYP2C8 metabolized evacetrapib, clinical studies confirmed that evacetrapib is primarily metabolized by CYP3A. However, given the modest increase in evacetrapib exposure and robust clinical safety profile to date, there is a low likelihood of clinically relevant DDI with concomitant use of strong CYP3A or CYP2C8 inhibitors.

A Multidose Study to Examine the Effect of Food on Evacetrapib Exposure at Steady State.

PURPOSE: To determine the effect of a high-fat meal on evacetrapib exposure at steady state in healthy participants. METHODS: This was a randomized, 2-period, 2-sequence, open-label, crossover study. Patients were randomly assigned to 1 of the 2 treatment sequences in which they received evacetrapib 130 mg/d for 10 days following a 10-hour fast each day or following a high-fat breakfast each day. Plasma samples collected through 24 hours were analyzed for evacetrapib concentrations and pharmacokinetic parameter estimates including area under the concentration-time curve during a dosing interval (AUCτ), maximum observed concentration (Cmax), and time of Cmax (tmax) were calculated. Pharmacodynamic parameters, including cholesteryl ester transfer protein (CETP) activity, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol, and triglycerides, were also assessed. RESULTS: A total of 34 males and 6 females, mean age 41.5 years and mean body mass index 26.6 kg/m(2), were enrolled. Statistical analysis showed AUCτ was 44% higher (90% confidence interval [CI]: 29%-62%) and Cmax was 51% higher (90% CI: 28%-79%) in the fed state than in the fasted state, indicating an effect of food. Consistent with higher evacetrapib exposure, changes in HDL-C, LDL-C, and CETP activity appeared to be greater in the fed state than in the fasted state. There were no notable changes in total cholesterol or triglycerides following administration in the fed and fasted states. The 130-mg doses of evacetrapib were well tolerated with and without food. CONCLUSION: A high-fat meal increased evacetrapib mean exposure at steady state by 44% in healthy participants.

Assessment of the persistence of anacetrapib and evacetrapib concentrations using two pharmacokinetic modeling approaches.

Anacetrapib, a cholesterol ester transfer protein (CETP) inhibitor, has been reported to have longer elimination half-life after longer treatment. Two pharmacokinetic model-based approaches were used to assess whether evacetrapib, another CETP inhibitor, could behave similarly. Using population pharmacokinetic (PopPK) modeling, evacetrapib and anacetrapib pharmacokinetics were characterized using available concentration-time data, and steady-state conditions were simulated. Published 2-compartment models for each compound were adapted to include a hypothetical third compartment representing a depot into which drug could partition. Physiologically based pharmacokinetic (PBPK) modeling was used to predict steady-state conditions and terminal half-life based on known physicochemical and dispositional properties. The PopPK model described the anacetrapib data well, showing a likely third compartment with estimated apparent volume of 40,700 L. Anacetrapib's estimated half-life for this compartment was 550 days. Simulations for evacetrapib using a hypothetical 3-compartment model, the third compartment being consistent with that of the anacetrapib model, produced predictions inconsistent with reported results, indicating that evacetrapib did not substantially accumulate into a large compartment. The PBPK simulations were consistent with PopPK results, predicting accumulation for anacetrapib (but not evacetrapib) followed by very slow elimination. Based on available data and known physicochemical properties, evacetrapib is not expected to accumulate substantially during long-term treatment.

Prasugrel in children with sickle cell disease: pharmacokinetic and pharmacodynamic data from an open-label, adaptive-design, dose-ranging study.

INTRODUCTION: This phase 2 study was designed to characterize the relationship among prasugrel dose, prasugrel's active metabolite (Pras-AM), and platelet inhibition while evaluating safety in children with sickle cell disease. It was open-label, multicenter, adaptive design, dose ranging, and conducted in 2 parts. Part A: Patients received escalating single doses leading to corresponding increases in Pras-AM exposure and VerifyNow®P2Y12 (VN) platelet inhibition and decreases in VNP2Y12 reaction units and vasodilator-stimulated phosphoprotein platelet reactivity index. Part B: Patients were assigned daily doses (0.06, 0.08, and 0.12 mg/kg) based on VN pharmacodynamic measurements at the start of 2 dosing periods, each 14±4 days. Platelet inhibition was significantly higher at 0.12 mg/kg (56.3%±7.4%; least squares mean±SE) compared with 0.06 mg/kg (33.8%±7.4%) or 0.08 mg/kg (37.9%±5.6%). Patients receiving 0.12 mg/kg achieved ≥30% platelet inhibition; only 1 patient receiving 0.06 mg/kg exceeded 60% platelet inhibition. High interpatient variability in response to prasugrel and the small range of exposures precluded rigorous characterization of the relationship among dose, Pras-AM, and platelet inhibition. SAFETY: No hemorrhagic events occurred in Part A; 3 occurred in Part B, all mild and self-limited. CONCLUSIONS: Most children with sickle cell disease may achieve clinically relevant platelet inhibition with titration of daily-dose prasugrel.

Effect of deodorant and antiperspirant use and presence or absence of axillary hair on absorption of testosterone 2% solution applied to men's axillae.

INTRODUCTION: Testosterone 2% solution is applied to axillae and is indicated for testosterone replacement therapy in males deficient in endogenous testosterone. AIM: This open-label crossover study evaluated the effect of deodorant/antiperspirant use and presence or absence of axillary hair on absorption of testosterone solution. METHODS: Healthy males (N = 30; ≥50 years of age with baseline testosterone <400 ng/dL) were randomized to one of four treatment sequences involving six treatments. Each treatment consisted of one 1.5-mL dose of testosterone 2% solution (30 mg of testosterone) applied to each axilla. Axillae were unshaved or shaved, and were untreated or pretreated with deodorant/antiperspirant. MAIN OUTCOME MEASURES: Blood samples were taken over 72 hours after each dose for measuring serum testosterone concentrations. RESULTS: Profiles of mean testosterone concentrations were similar across treatments. For all treatments, area under the concentration-time curve through 24 hours (AUC[0-24] ) and 72 hours (AUC[0-72] ), and maximum total testosterone concentration (Cmax ) were similar except for 15% lower Cmax when treatment was applied after deodorant/antiperspirant to shaved vs. unshaved axillae (least squares mean, 531 ng/dL vs. 626 ng/dL, respectively; P = 0.011). This difference is not considered clinically significant. The 95% confidence intervals for AUC(0-24) , AUC(0-72) , and Cmax fell within the traditional bioequivalence limits of 0.8 to 1.25. Incidence of treatment-emergent adverse events (TEAEs) was low (<15%) in each treatment arm, and most TEAEs were mild. CONCLUSIONS: Absorption of testosterone 2% solution was unaffected by use of deodorant/antiperspirant or by the presence or absence of axillary hair. Testosterone solution was generally well tolerated.

The influence of body size on the pharmacodynamic and pharmacokinetic response to clopidogrel and prasugrel: a retrospective analysis of the FEATHER study.

INTRODUCTION: Patients treated with clopidogrel who have higher body size exhibit greater platelet reactivity than patients with lower body size. In a retrospective analysis of the FEATHER trial, we examined the relationship between platelet response to thienopyridines clopidogrel 75 mg (Clop-75), prasugrel 5mg (Pras-5), and prasugrel 10mg (Pras-10) using 3 body size indices: body weight (BW), body mass index (BMI), and body surface area (BSA). Relationships were assessed as continuous variables and as 4 incremental body size groups. MATERIALS AND METHODS: Aspirin-treated patients with stable coronary artery disease (N=72) and a BW range of 45-134 kg received Clop-75, Pras-5, and Pras-10 in a 3-period, blinded, cross-over study. Platelet assays included maximum platelet aggregation (MPA) to 20µM ADP by light transmission aggregometry, VerifyNow-P2Y12 reaction units (PRU), and vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation platelet reactivity index (PRI). Exposure to active metabolites (AMs) was also assessed. RESULTS: Body size was a determinant of AM exposure and residual platelet reactivity regardless of type and dose of thienopyridine. BW and BSA demonstrated marginally stronger correlations with platelet reactivity; VASP-PRI demonstrated a stronger correlation with the body size than the other tests. Correlation coefficients ranged from a high of 0.64 (BW vs. PRI on Pras-5) to a low of 0.34 (BMI vs. MPA on Pras-10), but all were statistically significant (p<0.01). CONCLUSIONS: Using a comprehensive selection of body size indices, AM exposures, platelet function tests, and thienopyridine doses, we demonstrated a consistent inverse relationship between body size and response to clopidogrel and prasugrel.

Steady-state pharmacokinetics of darunavir/ritonavir and pitavastatin when co-administered to healthy adult volunteers.

BACKGROUND: The treatment of hyperlipidaemia in human immunodeficiency virus (HIV)-infected patients has become increasingly important. However, treatment options are limited because of the drug-drug interaction between certain statins and HIV medications metabolized by cytochrome P450 (CYP) enzymes. OBJECTIVES: The primary objective was to investigate the steady-state pharmacokinetics of pitavastatin when co-administered with darunavir/ritonavir. The secondary objective was to investigate the steady-state pharmacokinetics of both darunavir and ritonavir when co-administered with pitavastatin. METHODS: This was a single-centre, open-label, multi-dose, fixed-sequence study in HIV seronegative healthy volunteers. Pitavastatin 4 mg was administered once daily on days 1-5 and on days 12-16, and darunavir 800 mg/ritonavir 100 mg once daily on days 6-16. Pharmacokinetic blood sampling was performed on days 5, 11 and 16. No significant interaction was concluded if the 90 % confidence intervals (CIs) of the geometric mean ratios (GMRs) for total exposure [i.e. the area under the plasma concentration-time curve over a dosing interval at steady state (AUC(0-τ))] and for peak exposure [i.e. the maximum plasma concentration (C(max))] of the two treatments were within the 80-125 % range. RESULTS: Twenty-eight subjects (mean age 30.5 years) were enrolled, and pharmacokinetic data were available for 27 subjects. For pitavastatin, the GMRs and 90 % CIs for the AUC(0-τ) and C(max) ratios with co-administration were 0.74 (0.69-0.80) and 0.96 (0.84-1.09), respectively. For both darunavir and ritonavir, the 90 % CIs for the AUC(0-τ) and C max ratios were within 80-125 % with pitavastatin co-administration. No significant safety issues were reported. CONCLUSION: Darunavir/ritonavir decreased total exposure to pitavastatin by 26 %, while peak exposures were similar. Pitavastatin did not influence the pharmacokinetics of darunavir or ritonavir. There is limited interaction between pitavastatin and darunavir/ritonavir.

Higher body weight patients on clopidogrel maintenance therapy have lower active metabolite concentrations, lower levels of platelet inhibition, and higher rates of poor responders than low body weight patients.

Body weight is a predictor of clopidogrel response. However, no prospective studies have compared pharmacodynamic (PD) and pharmacokinetic (PK) data based on body weight. We compared PD and PK effects of clopidogrel 75 mg in low body weight (LBW, <60 kg) and higher body weight (HBW, ≥60 kg) patients with stable coronary artery disease. LBW (n = 34, 56.4 ± 3.7 kg) and HBW (n = 38, 84.7 ± 14.9 kg) aspirin-treated patients received clopidogrel 75 mg for 10-14 days. The area under the concentration-time curve of active metabolite (Clop-AM) calculated through the last quantifiable concentration up to 4 h postdose, AUC(0-tlast), was calculated by noncompartmental methods. Light transmission aggregometry (LTA) (maximum platelet aggregation and inhibition of platelet aggregation to 20 µM adenosine diphosphate (ADP), and residual platelet aggregation to 5 µM ADP), VerifyNow(®) P2Y12 reaction units (PRU), and vasodilator-associated stimulated phosphoprotein phosphorylation platelet reactivity index (VASP-PRI) were performed. Mean AUC(0-tlast) was lower in HBW than LBW patients: 12.8 versus 17.9 ng h/mL. HBW patients had higher platelet reactivity as measured by LTA (all p ≤ 0.01), PRU (207 ± 68 vs. 152 ± 57, p < 0.001), and VASP-PRI (56 ± 18 vs. 39 ± 17, p < 0.001). More HBW patients exhibited high on-treatment platelet reactivity (HPR) using PRU (35 vs. 9%) and VASP-PRI (65 vs. 27%). Body weight correlated with PRU and VASP-PRI (both p < 0.001), and inversely with log transformed AUC(0-tlast) (p < 0.001). In conclusion, HBW patients had lower levels of Clop-AM, and higher platelet reactivity and rates of HPR than LBW subjects, contributing to their suboptimal response to clopidogrel.

Prasugrel 5 mg in the very elderly attenuates platelet inhibition but maintains noninferiority to prasugrel 10 mg in nonelderly patients: the GENERATIONS trial, a pharmacodynamic and pharmacokinetic study in stable coronary artery disease patients.

OBJECTIVES: This study assessed pharmacodynamic (PD) response to the reduced prasugrel maintenance dose of 5 mg in very elderly (VE) patients (≥75 years of age). BACKGROUND: In the TRITON-TIMI 38 (TRial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet InhibitioN with Prasugrel-Thrombolysis In Myocardial Infarction 38) study prasugrel 10 mg reduced ischemic events versus clopidogrel 75 mg, but increased bleeding in VE patients. METHODS: We examined PD and active metabolite pharmacokinetics (PKs) with prasugrel 5 and 10 mg and clopidogrel 75 mg in a 3-period (12 days each) blinded, crossover study in VE (n = 73; mean: 79 ± 3 years of age) or (n = 82) nonelderly (NE) (≥45 to <65 years of age; mean: 56 ± 5 years of age) stable coronary artery disease (CAD) patients receiving background aspirin. Assays included light transmission aggregometry (LTA), VerifyNow P2Y12 (VN-P2Y12), and vasodilator-associated stimulated phosphoprotein (VASP). The primary comparison was noninferiority of maximum platelet aggregation (MPA) comparing the median for prasugrel 5 mg in VE versus the 75th percentile for prasugrel 10 mg in NE, using a pre-specified 1-sided 97.5% confidence interval for the difference <15%. RESULTS: Prasugrel 5 mg in VE met the primary PD noninferiority criterion versus prasugrel 10 mg in NE. For prasugrel 5 mg, MPA was significantly lower (57 ± 14%) than clopidogrel (63 ± 14%; p < 0.001) in VE but higher than prasugrel 10 mg in NE (46 ± 12%; p < 0.001). PD response by LTA, VN-P2Y12, and VASP during all treatments appeared similar between age cohorts. Prasugrel 5 mg resulted in fewer VE poor responders than clopidogrel. Rates of mild bleeding were higher with prasugrel 10 mg but similar for prasugrel 5 mg versus clopidogrel 75 mg. CONCLUSIONS: In aspirin-treated stable CAD patients, prasugrel 5 mg in VE attenuated platelet inhibition while meeting pre-specified noninferiority criterion versus prasugrel 10 mg in NE, with significantly better PD response and fewer poor responders compared to clopidogrel 75 mg in VE. (Comparison of Prasugrel and Clopidogrel in Very Elderly and Non-Elderly Patients With Stable Coronary Artery Disease [GENERATIONS]; NCT01107912).

Pharmacokinetic and pharmacodynamic effects of prasugrel in healthy Korean males.

Prasugrel is a thienopyridine for treatment of acute coronary syndromes in patients undergoing percutaneous coronary intervention. Higher concentrations of prasugrel's active metabolite (R-138727) have been observed in Asian than white subjects. The primary objective was to investigate pharmacokinetics of R-138727 in healthy Korean males. Thirty subjects were randomized (1:2) to a 60 or 30 mg loading dose, subsequently (1:1:1) to 10-, 7.5-, or 5-mg maintenance doses. R-138727 plasma concentrations were analyzed with liquid chromatography/mass spectrometry. Platelet aggregation was measured with Accumetrics VerifyNow. Mean (coefficient of variation) exposure to R-138727 was 600 ng·h/mL (16%) after 60 mg prasugrel and 283 ng·h/mL (17%) after 30 mg. After 10, 7.5, and 5 mg, mean exposures were 78.1 (24%), 58.4 (21%), and 38.3 ng·h/mL (24%). Pharmacokinetics were linear over this range. Daily 5 mg doses maintained a 65% (SD = 14.5%) inhibition of adenosine diphosphate-induced platelet aggregation; all other doses produced ≥90%. Prasugrel was well tolerated with no serious adverse events. Results are consistent with other studies of Asian subjects administered prasugrel. Although further guidance will be provided by a recently completed phase 3 study, these preliminary data suggest that dosing strategies approved for white patients with acute coronary syndromes are applicable to Asian patients.

A phase 1 study of prasugrel in patients with sickle cell disease: pharmacokinetics and effects on ex vivo platelet reactivity.

AIMS: Prasugrel is a novel thienopyridine P2Y12 adenosine diphosphate (ADP) receptor antagonist that inhibits ADP-mediated platelet activation and aggregation. Accordingly, it may be useful in reducing platelet-related ischaemia in sickle cell disease (SCD). Exposure to prasugrel's active metabolite (Pras-AM) and its antiplatelet activity in SCD have not been investigated. METHODS: Thirteen adult patients with SCD and an equal number of matched healthy control subjects were studied before and after 12 days of 5.0 or 7.5 mg day(-1) prasugrel treatment. Platelet reactivity was assessed by light transmission aggregometry (LTA), impedance aggregometry (MEA), VerifyNow® P2Y12, vasodilator-stimulated phosphoprotein (VASP) phosphorylation and Plateletworks. Exposure to Pras-AM was also assessed. RESULTS: At baseline, patients with SCD showed increased platelet reactivity vs. healthy control subjects with VerifyNow (408 vs. 323 P2Y12 reaction units (PRU), respectively, P = 0.003) and MEA (106 vs. 77 area under the aggregation curve (AU.min), P = 0.002); lower platelet reactivity index with VASP flow cytometry (59 vs. 79% platelet reactivity index (PRI), P = 0.018); and no significant differences with LTA, VASP enzyme-linked immunosorbent assay or Plateletworks. Relative to baseline, prasugrel significantly reduced platelet reactivity by all assays in both populations (all P < 0.05). Prasugrel was well tolerated, with no bleeding-related events in patients with SCD. The mean concentration-time profiles of Pras-AM were comparable between healthy subjects and patients with SCD following a single 10 mg prasugrel dose and following the 12th dose of 7.5 or 5 mg prasugrel. CONCLUSIONS: Results demonstrate that in response to prasugrel, patients with SCD and healthy subjects have similar degrees of platelet inhibition and exposure to Pras-AM, and provide a basis for further study of prasugrel in patients with SCD.

Reduction in platelet reactivity with prasugrel 5 mg in low-body-weight patients is noninferior to prasugrel 10 mg in higher-body-weight patients: results from the FEATHER trial.

OBJECTIVES: The aim of this study was to confirm prior modeling data suggesting that prasugrel 5 mg in low-body-weight (LBW) patients would be noninferior to prasugrel 10 mg in higher-body-weight (HBW) patients as assessed by maximal platelet aggregation (MPA). BACKGROUND: Prasugrel 10 mg reduced ischemic events compared with clopidogrel 75 mg but increased bleeding, particularly in LBW patients. METHODS: In this blinded, 3-period, crossover study in stable patients with coronary artery disease (CAD) taking aspirin, prasugrel 5 and 10 mg and clopidogrel 75 mg were administered to LBW (56.4 ± 3.7 kg; n = 34) and HBW patients (84.7 ± 14.9 kg; n = 38). Assays included light transmission aggregometry (LTA), VerifyNow P2Y12 (VN), and vasodilator-associated stimulated phosphoprotein (VASP) level measured predose and after each 12-day treatment. RESULTS: Median MPA by LTA for prasugrel 5 mg in LBW patients was noninferior to the 75th percentile for prasugrel 10 mg in HBW patients (primary endpoint) and mean MPA was similar, but active metabolite exposure was lowered by 38%. Within LBW patients, prasugrel 5 mg lowered MPA more than clopidogrel (least squares mean difference [95% confidence interval]: -3.7% [-6.72%, -0.69%]) and resulted in lower rates of high on-treatment platelet reactivity (HPR). Within HBW patients, prasugrel 10 mg lowered MPA more than clopidogrel (-16.9% [-22.3%, -11.5%]). Similar results were observed by VN and VASP. Prasugrel 10 mg in LBW patients was associated with more mild to moderate bleeding (mainly bruising) compared with prasugrel 5 mg and clopidogrel. CONCLUSIONS: In aspirin-treated patients with CAD, prasugrel 5 mg in LBW patients reduced platelet reactivity to a similar extent as prasugrel 10 mg in HBW patients and resulted in greater platelet inhibition, lower HPR, and similar bleeding rates compared with clopidogrel. (Comparison of Prasugrel and Clopidogrel in Low Body Weight Versus Higher Body Weight With Coronary Artery Disease [FEATHER]; NCT01107925).

Effect of pitavastatin vs. rosuvastatin on international normalized ratio in healthy volunteers on steady-state warfarin.

OBJECTIVE: Statins have been shown to impact international normalized ratio (INR) when coadministered with warfarin. The aim of this study was to assess the effect of pitavastatin compared with rosuvastatin on steady-state pharmacodynamics (PD) of warfarin by measuring INR in healthy adult subjects. METHODS: Subjects received oral doses of warfarin 5 mg once daily on days 1 through 3. The dose was titrated on days 4 through 9 to reach a steady-state INR of 1.5 to 2.2. Warfarin was continued on days 10 through 21 and pitavastatin 4 mg or rosuvastatin 40 mg was administered once daily on days 14 through 22. After a 14-day washout period, the process was repeated with the alternate statin. STUDY NUMBER: NK-104-4.03US. RESULTS: For pitavastatin, mean INR changed from 1.73 ± 0.18 (n = 42) on day 14 before starting statin dosing, to 1.78 ± 0.29 (n = 42) on day 22 at treatment end; the difference in INR was not significant (p = 0.219). For rosuvastatin, mean INR increased significantly from 1.74 ± 0.20 (n = 43) at baseline to 1.90 ± 0.30 (n = 43) at treatment end (p < 0.001). Rosuvastatin caused a significantly greater increase in INR than pitavastatin (p < 0.001). CONCLUSION: Steady-state INR during warfarin treatment did not change significantly when pitavastatin 4 mg was added to the regimen, while a significant increase was observed when rosuvastatin 40 mg was added. The effect of rosuvastatin on INR was significantly larger than the effect of pitavastatin. This study is limited because it was done in healthy volunteers. Further studies in patient populations are needed to better understand the clinical significance of the results.