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Chronic kidney disease (CKD) involves significant metabolic abnormalities and has a high mortality rate. Because the levels of serum metabolites in patients with CKD might provide insight into subclinical disease states and risk for future mortality, we determined which serum metabolites reproducibly associate with mortality in CKD using a discovery and replication design. Metabolite levels were quantified via untargeted liquid chromatography and mass spectroscopy from serum samples of 299 patients with CKD in the Modification of Diet in Renal Disease (MDRD) study as a discovery cohort. Six among 622 metabolites were significantly associated with mortality over a median follow-up of 17 years after adjustment for demographic and clinical covariates, including urine protein and measured glomerular filtration rate. We then replicated associations with mortality in 963 patients with CKD from the African American Study of Kidney Disease and Hypertension (AASK) cohort over a median follow-up of ten years. Three of the six metabolites identified in the MDRD cohort replicated in the AASK cohort: fumarate, allantoin, and ribonate, belonging to energy, nucleotide, and carbohydrate pathways, respectively. Point estimates were similar in both studies and in meta-analysis (adjusted hazard ratios 1.63, 1.59, and 1.61, respectively, per doubling of the metabolite). Thus, selected serum metabolites were reproducibly associated with long-term mortality in CKD beyond markers of kidney function in two well characterized cohorts, providing targets for investigation., (Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

A novel orotic acid salt form of tenofovir disoproxil (DA-2802) was developed and is expected to replace the fumaric acid salt form. The pharmacokinetic (PK) characteristics and tolerability profiles of DA-2802 were compared to those of tenofovir disoproxil fumarate (TDF, Viread ® ) in healthy subjects. A randomized, open-label, single-dose study was conducted in 36 healthy subjects using a two-treatment, two-period, and two-sequence crossover design. Subjects received a single oral dose of 319 mg DA-2802 or 300 mg TDF, during each period, with a 7-day washout. Serial blood samples were collected pre-dosing and up to 72 hours post-dosing in each period, for determination of serum tenofovir concentration, which was measured by ultra-performance liquid chromatography-tandem mass spectrometry. A non-compartmental method was used to obtain PK parameters of tenofovir. For comparison between the two tenofovir disoproxil salts, the 90% confidence intervals (90% CIs) of geometric mean ratios of DA-2802 to TDF for the maximum concentration (C max ) and the area under the concentration-time curve to the last quantifiable concentration (AUC 0-t ) were determined. The tolerability profiles of tenofovir were assessed by evaluation of adverse events and vital signs, physical examination, ECG, and clinical laboratory tests. The serum tenofovir concentration-time profiles of DA-2802 or TDF were comparable in 32 subjects who completed the study. In both profiles, a two-compartmental elimination with first-order elimination kinetics in the terminal phase was reported in a few subjects, showing a secondary peak in the initial phase of elimination. The geometric mean ratio (90% CI) of DA-2802 to TDF was 0.898 (0.815-0.990) for C max and 0.904 (0.836-0.978) for AUC 0-t . There were no clinically significant findings in the tolerability assessments. DA-2802 showed comparable PK characteristics and tolerability profiles to TDF., Competing Interests: Disclosure Ms Mun Ju Choi and Mr Tae Young Oh are employees of Dong-A ST Co., Ltd. None of the authors of this study are involved in financial or personal relationships with agencies, institutions, or organizations that could inappropriately influence the statistical analysis plan or interpretation of this work. The authors report no other conflicts of interest in this work.

Background: Fumaric acid is a commonly used excipient in pharmaceutical products. It is not known if its presence may lead to fluctuation of endogenous fumarate levels. An LC-MS/MS method was developed and validated to quantify fumarate in support of a toxicokinetics study., Results: Stability evaluation showed that endogenous fumarate was stable for 6 h at room temperature, while exogenously added fumaric acid was converted to malate within 1 h due to the presence of fumarase. Citric acid, a fumarase inhibitor, prevented the conversion of added fumaric acid in rat plasma., Conclusion: The method was validated in citric acid stabilized rat plasma using a surrogate matrix approach. A discrepancy in stability was observed between endogenous fumarate and exogenously added fumaric acid.

Background and Objectives: Renal hemodynamic effects of inhibitors of the renin-angiotensin system can increase the risk of acute kidney injury under certain conditions. The BP-lowering effects of the renin inhibitor aliskiren are sustained 3-4 weeks after withdrawal. In this study, the reversibility of the renal hemodynamic effects of aliskiren was tested., Design, Setting, Participants, & Measurements: In this open-label study, renal perfusion was measured by 1.5-T magnetic resonance imaging-arterial spin labeling in 34 subjects with arterial hypertension before aliskiren (pre-aliskiren), after 4 weeks of aliskiren treatment (300 mg), and 4-5 days (∼2.5-3.0× plasma half-life) after withdrawal (post-aliskiren)., Results: Aliskiren reduced systolic BP from 152 ± 14 to 139 ± 16 mmHg (P<0.0001), which was sustained post-aliskiren (136 ± 13 mmHg, P=1.00 versus aliskiren). Aliskiren significantly altered renal perfusion (P=0.005), increasing from 272 ± 25 pre-aliskiren to 287 ± 29 ml/min per 100 g during aliskiren (P=0.03). This increase in renal perfusion was completely reversed post-aliskiren (272 ± 26 ml/min per 100 g, P=0.03 versus aliskiren, P=0.63 versus pre-aliskiren). No changes were noted in urinary angiotensinogen levels. Plasma renin activity was reduced by aliskiren, which was sustained post-aliskiren. Angiotensin II and aldosterone were reduced by aliskiren but recovered post-aliskiren to pre-aliskiren levels., Conclusions: After withdrawal of aliskiren, the effects on BP were sustained, whereas increase in renal perfusion was reversed, which was associated with recovery of angiotensin II and aldosterone to pretreatment levels. Renal hemodynamic effects are more readily reversible than systemic effects of aliskiren.

Aim: The aim of this study was to investigate the effects of orange juice and apple juice on the pharmacokinetics and pharmacodynamics of aliskiren., Methods: In a randomized crossover study, 12 healthy volunteers ingested 200 ml of orange juice, apple juice or water three times daily for 5 days. On day 3, they ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h, its excretion into urine up to 12 h and plasma renin activity up to 24 h., Results: Orange and apple juice reduced aliskiren peak plasma concentrations by 80% (95% CI 63%, 89%, P < 0.001) and 84% (95% CI 72%, 91%, P < 0.001), and the area under the plasma aliskiren concentration-time curve (AUC) by 62% (95% CI 47%, 72%, P < 0.001) and 63% (95% CI 46%, 74%, P < 0.001), respectively, but had no significant effect on its elimination half-life or renal clearance. The decreases in aliskiren AUC by orange and apple juice correlated with aliskiren AUC during the water phase (r= 0.98, P < 0.001). Plasma renin activity was 87% and 67% higher at 24 h after aliskiren during the orange juice and apple juice phases, respectively, than during the water phase (P < 0.05)., Conclusions: Orange juice and apple juice greatly reduce the plasma concentrations and renin-inhibiting effect of aliskiren, probably by inhibiting its OATP2B1-mediated influx in the small intestine. Concomitant intake of aliskiren with orange or apple juice is best avoided., (© 2011 The Authors. British Journal of Clinical Pharmacology © 2011 The British Pharmacological Society.)

Background: Pharmacological interruption of the renin-angiotensin system focuses on optimization of blockade. As a measure of intrarenal renin activity, we have examined renal plasma flow (RPF) responses in a standardized protocol. Compared with responses with angiotensin-converting enzyme inhibition (rise in RPF approximately 95 mL x min(-1) x 1.73 m(-2)), greater renal vasodilation with angiotensin receptor blockers (approximately 145 mL x min(-1) x 1.73 m(-2)) suggested more effective blockade. We predicted that blockade with the direct oral renin inhibitor aliskiren would produce renal vascular responses exceeding those induced by angiotensin-converting enzyme inhibitors and angiotensin receptor blockers., Methods and Results: Twenty healthy normotensive subjects were studied on a low-sodium (10 mmol/d) diet, receiving separate escalating doses of aliskiren. Six additional subjects received captopril 25 mg as a low-sodium comparison and also received aliskiren on a high-sodium (200 mmol/d) diet. RPF was measured by clearance of para-aminohippurate. Aliskiren induced a remarkable dose-related renal vasodilation in low-sodium balance. The RPF response was maximal at the 600-mg dose (197+/-27 mL x min(-1) x 1.73 m(-2)) and exceeded responses to captopril (92+/-20 mL x min(-1) x 1.73 m(-2); P<0.01). Furthermore, significant residual vasodilation was observed 48 hours after each dose (P<0.01). The RPF response on a high-sodium diet was also higher than expected (47+/-17 mL x min(-1) x 1.73 m(-2)). Plasma renin activity and angiotensin levels were reduced in a dose-related manner. As another functional index of the effect of aliskiren, we found significant natriuresis on both diets., Conclusions: Renal vasodilation in healthy people with the potent renin inhibitor aliskiren exceeded responses seen previously with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. The effects were longer lasting and were associated with significant natriuresis. These results indicate that aliskiren may provide more complete and thus more effective blockade of the renin-angiotensin system.

Thiazide diuretics, angiotensin-converting enzyme inhibitors, and angiotensin receptor blockers all cause reactive rises in plasma renin activity. We hypothesized that renin inhibition with aliskiren would prevent this reactive rise and also enhance blood pressure lowering. In 3 open-label studies in which blood pressure was assessed with ambulatory measurement, aliskiren was administered to patients with mild-to-moderate hypertension in combination with hydrochlorothiazide (n=23), ramipril (n=21), or irbesartan (n=23). In the diuretic combination study, the addition of 25 mg of hydrochlorothiazide to 150 mg of aliskiren daily for 3 weeks significantly lowered daytime pressure, compared with aliskiren monotherapy (systolic/diastolic mean change from baseline [SEM]: daytime: -18.4 [2.1]/ -10.6 [1.7] versus -10.4 [1.8]/-5.8 [1.4]; nighttime: -15.6 [2.7]/-8.1 [1.8] versus -8.8 [2.9]/-5.0 [2.2]). In the angiotensin-converting enzyme inhibitor combination study, the addition of 75 or 150 mg of aliskiren to 5 mg of ramipril alone for 3 weeks further lowered both daytime and nighttime pressures compared with ramipril monotherapy (daytime: -10.5 [2.9]/-8.1 [2.1] and -14 [3.7]/-8.7 [2.3] versus -6.1 [2.4]/-5.9 [1.5]; nighttime: -8.1 [2.6]/-5.3 [2.4] and -9.6 [3.4]/-5.3 [2.4] versus -2 [2.3]/-0.7 [2.2]). In the angiotensin receptor blocker combination study, the addition of 75 or 150 mg of aliskiren to 150 mg of irbesartan alone, for 3 weeks, resulted in significantly lower nighttime pressures compared with irbesartan monotherapy (daytime: -14.8 [2]/-8.2 [1.3] and -13.3 [1.6]/-6.8 [0.9] versus -11.4 [1.6]/-6.5 [1.1]; nighttime: -16.1 [2.4]/-8.6 [1.7] and -13.2 [2.7]/-7.2 [1.9] versus -9.0 [2.5]/-4.7 [1.9]). Aliskiren (150 mg) alone significantly inhibited plasma renin activity by 65% (P<0.0001). Ramipril and irbesartan monotherapy caused 90% and 175% increases in plasma renin activity, respectively. By contrast, when aliskiren was coadministered with hydrochlorothiazide, ramipril, or irbesartan, plasma renin activity did not increase but remained similar to baseline levels or was decreased (combination therapy versus untreated; median [interquartile range]; aliskiren and hydrochlorothiazide: 0.4 [0.2 to 1.1] versus 0.7 [0.5 to 1.3]; ramipril and aliskiren: 0.5 [0.3 to 0.9] versus 0.6 [0.5 to 0.8]; irbesartan and aliskiren: 0.4 [0.2 to 0.9] versus 0.6 [0.4 to 0.9]). These results suggest that renin inhibition with aliskiren in these combinations increases renin-angiotensin system suppression, improves 24-hour blood pressure control, and may ultimately provide better end-organ protection in patients with hypertension.

Aims: Aliskiren is the first in a new class of orally effective renin inhibitors for the treatment of hypertension. This study compared the pharmacokinetic and pharmacodynamic properties of aliskiren in Japanese and Caucasian subjects., Methods: In this open-label, single-centre, parallel-group, single- and multiple-dose study, 19 Japanese and 19 Caucasian healthy young male subjects received a single 300-mg oral dose of aliskiren on day 1 and then aliskiren 300 mg once daily on days 4-10. Blood samples were collected for the measurement of plasma aliskiren concentration, plasma renin concentration (PRC) and plasma renin activity (PRA)., Results: Pharmacokinetic parameters were comparable in Japanese and Caucasian subjects following administration of a single dose of aliskiren {ratio of geometric means: C(max) 1.12 [90% confidence interval (CI) 0.88, 1.43]; AUC(0-72 h) 1.19 [90% CI 1.02, 1.39]} and at steady state [mean ratio: C(max) 1.30 (90% CI 1.00, 1.70); AUC(0-tau) 1.16 (90% CI 0.95, 1.41)]. There was no notable difference in the plasma half-life of aliskiren between Japanese and Caucasian groups (29.7 +/- 10.2 h and 32.0 +/- 6.6 h, respectively). At steady state, peak PRC level and AUC for the concentration-time plot were not significantly different between Japanese and Caucasian subjects (P = 0.64 and P = 0.80, respectively). A single oral dose of aliskiren significantly reduced PRA to a similar extent in Japanese and Caucasian subjects (by 87.5% and 85.7%, respectively, compared with baseline; P < 0.01). Aliskiren was well tolerated by both ethnic groups., Conclusions: The oral renin inhibitor aliskiren demonstrated similar pharmacokinetic and pharmacodynamic properties in Japanese and Caucasian subjects.

Background: Psoriasis is a chronic inflammatory skin disease that can be successfully treated with a mixture of fumaric acid esters (FAE) formulated as enteric-coated tablets for oral use. These tablets consist of dimethylfumarate (DMF) and salts of monoethylfumarate (MEF) and its main bioactive metabolite is monomethylfumarate (MMF). Little is known about the pharmacokinetics of these FAE. The aim of the present study was to investigate the hydrolysis of DMF to MMF and the stability of MMF, DMF and MEF at in vitro conditions representing different body compartments., Results: DMF is hydrolyzed to MMF in an alkaline environment (pH 8), but not in an acidic environment (pH 1). In these conditions MMF and MEF remained intact during the period of analysis (6 h). Interestingly, DMF was hardly hydrolyzed to MMF in a buffer of pH 7.4, but was rapidly hydrolyzed in human serum having the same pH. Moreover, in whole blood the half-life of DMF was dramatically reduced as compared to serum. The concentrations of MMF and MEF in serum and whole blood decreased with increasing time. These data indicate that the majority of the FAE in the circulation are metabolized by one or more types of blood cells. Additional experiments with purified blood cell fractions resuspended in phosphate buffered saline (pH 7.4) revealed that at concentrations present in whole blood monocytes/lymphocytes, but not granulocytes and erythrocytes, effectively hydrolyzed DMF to MMF. Furthermore, in agreement with the data obtained with the pure components of the tablet, the enteric-coated tablet remained intact at pH 1, but rapidly dissolved at pH 8., Conclusion: Together, these in vitro data indicate that hydrolysis of DMF to MMF rapidly occurs at pH 8, resembling that within the small intestines, but not at pH 1 resembling the pH in the stomach. At both pHs MMF and MEF remained intact. These data explain the observation that after oral FAE intake MMF and MEF, but not DMF, can be readily detected in the circulation of human healthy volunteers and psoriasis patients.

Renin is the main determinant of angiotensin (Ang) II levels. It, therefore, always appeared desirable to reduce Ang II levels by direct inhibition of renin. So far, specific renin inhibitors lacked potency and/or oral availability. We tested the new orally active nonpeptidic renin inhibitor SPP100 (Aliskiren, an octanamide with a 50% inhibitory concentration [IC50] in the low nanomolar range) in 18 healthy volunteers on a constant 100 mmol/d sodium diet using a double-blind, 3-way crossover protocol. In 3 periods of 8 days, separated by wash-outs of 6 days, each volunteer received 2 dosage levels of Aliskiren (low before high; 40 and 80 or 160 and 640 mg/d) and randomized placebo or 20 mg enalapril. Aliskiren was well tolerated. Not surprisingly, blood pressure and heart rate remained unchanged in these normotensive subjects. There was a dose-dependent decrease in plasma renin activity, Ang I, and Ang II following single doses of Aliskiren starting with 40 mg. Inhibition was still marked and significant after repeated dosing with maximal decreases in Ang II levels by 89% and 75% on Days 1 and 8, respectively, when the highest dose of Aliskiren was compared with placebo. At the same time, mean plasma active renin was increased 16- and 34-fold at the highest dose of Aliskiren. Plasma drug levels of Aliskiren were dose-dependent with maximal concentrations reached between 3 to 6 hours after administration; steady state was reached between 5 and 8 days after multiple dosing. Less than 1% of dose was excreted in the urine. Plasma and urinary aldosterone levels were decreased after doses of Aliskiren > or =80 mg and after enalapril. Aliskiren at 160 and 640 mg enhanced natriuresis on Day 1 by +45% and +62%, respectively, compared with placebo (100%, ie, 87+/-11 mmol/24h) and enalapril (+54%); kaliuresis remained unchanged. In conclusion, the renin inhibitor Aliskiren dose-dependently decreases Ang II levels in humans following oral administration. The effect is long-lasting and, at a dose of 160 mg, is equivalent to that of 20 mg enalapril. Aliskiren has the potential to become the first orally active renin inhibitor that provides a true alternative to ACE-inhibitors and Ang II receptor antagonists in therapy for hypertension and other cardiovascular and renal diseases.

In 28 patients with fulminant hepatic failure alkalaemia was present in 49 of a total of 65 observations. Alkalaemia was due primarlily to a low Pa, C02 in 30 instances and to raised plasma bicarbonate in 16 instances. Blood lactate, pyruvate, and acetoacetate were significantly raised, and in individual cases, blood citrate, succinate, and fumarate were elevated. Blood citrate rose progressively as the clinical condition worsened. Metabolic acidosis was only present in four patients. In three of these patients, all of whom had taken an overdose of paracetamol, the acidosis was severe, present before the onset of clinical heparic failure, and associated with hypoglycaemiaand mild hypotension. In two of these patients the acidosis was shown to be due to accumulation of lactic acid. Plasma free fatty acid concentrations were elevated out of proportion to the degree of ketosis.