The renin inhibitory activity of aliskiren hemifumarate was compared with the novel compound DS-8108b in vitro. Aliskiren hemifumarate exhibited an IC₅₀ of 1.5 nM against purified human renin. Its inhibitory effects on human and cynomolgus monkey plasma renin activity (PRA) were also evaluated, with IC₅₀ values of 2.9 nM and 8.0 nM, respectively. [1]
Aliskiren is a potent, tight-binding competitive inhibitor of purified human renin with a sub-nanomolar IC₅₀ of 0.6 nM. It demonstrates high specificity for renin over other human aspartic peptidases (cathepsin D, E, pepsin) and HIV-1 peptidase, showing more than 10,000-fold lower affinity for these related enzymes.
Additionally, at a concentration of 10 µM, aliskiren exhibited little or no effect on a broad panel of neurotransmitter receptors including α₁-, α₂-, and β-adrenoceptors, 5-HT, histamine, opiate, benzodiazepine and adenosine receptors, muscarinic cholinergic receptors, and AMPA, kainate, or NMDA glutamate receptors. [2]

In marmosets lacking in sodium, oral aliskiren (< 10 mg/kg, daily) lowers blood pressure and inhibits plasma renin activity [2]. In BALB/c mice expressing C26 mouse colon cancer cells, aliskiren (10 mg/kg, once by gavage) can dramatically reduce a number of cachexia-related symptoms, such as weight loss, tumor burden, muscle atrophy, and muscle dysfunction. and decreased longevity [3].

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In cynomolgus monkeys pretreated with furosemide, oral administration of aliskiren hemifumarate at doses of 3 and 10 mg/kg showed ex vivo plasma renin activity (PRA) suppressive effects. However, at equivalent doses or exposure levels, the novel compound DS-8108b demonstrated at least a three times more potent PRA suppressive effect compared to aliskiren hemifumarate. [1]
In sodium-depleted marmosets, once-daily oral administration of aliskiren at 3 mg/kg lowered mean arterial blood pressure (MAP) by approximately 10 mmHg within 2 hours on day 1, with recovery to pretreatment values after about 20 hours. At 10 mg/kg, it lowered MAP by a maximum of 13 ± 2 mmHg on day 1, with a reduction of 6 ± 1 mmHg still present at the time of dosing on day 2. By day 8 of treatment, the maximal reduction in MAP was 16 ± 2 mmHg. No significant changes in heart rate were observed at 3 mg/kg, and only transient increases occurred within the first 2 hours after the 10 mg/kg dose. There was no rebound increase in blood pressure after cessation of treatment.
Total and active plasma renin levels increased in a dose-dependent manner 2 hours after administration on day 8, but had decreased by 24 hours. Plasma renin activity (PRA), however, was reported to be completely inhibited both 2 and 24 hours after administration.
In an open-label study with hypertensive human patients, once-daily oral doses of aliskiren (75 mg for 4 weeks, then 150 mg for 4 weeks) lowered both daytime and night-time ambulatory systolic and diastolic blood pressure. PRA was reduced to 34 ± 7% of baseline after 75 mg and to 27 ± 6% after 150 mg. No significant changes in heart rate were observed. [2]

The inhibitory potency of aliskiren against human renin was studied in vitro. Human recombinant renin (0.33 ng/mL) was incubated with a synthetic tetradecapeptide substrate (13.33 µM) corresponding to the N-terminal 14 amino acids of human angiotensinogen. The incubation was carried out in a buffer containing human serum albumin and neomycin sulphate for 1 hour at 37°C. The enzymatic reaction was stopped by adding an ice-cold Tris-acetate buffer. The amount of Angiotensin I generated during the incubation was quantified by radioimmunoassay.
Aliskiren was also tested against human cathepsin D, cathepsin E, pepsin, and HIV-1 peptidase using specific synthetic peptide substrates for each enzyme, following established assay protocols.
The species specificity of aliskiren was determined by measuring its IC₅₀ for inhibiting endogenous renin activity in plasma from various species (human, marmoset, rat, dog, rabbit, cat, pig, guinea pig). Plasma collected on EDTA was incubated with an angiotensinase inhibitor and aliskiren (0.1 nM – 10 µM) for 1 hour at 37°C and pH 7.2. The Ang I generated was quantified by radioimmunoassay. [2]

Blood pressure and heart rate effects of aliskiren were evaluated in conscious, freely moving marmosets (weight 250-350 g) using telemetry. Pressure transmitters were surgically implanted into the peritoneal cavity with the sensor catheter placed in the aorta. Animals were allowed to recover for at least 4 weeks post-surgery.
Marmosets were maintained on a low sodium diet for 1 week before and during the experiments. Aliskiren (hydrochloride salt) at doses of 3 or 10 mg/kg, or vehicle (distilled water), was administered orally by gavage once daily for 8 consecutive days. Blood pressure and heart rate were continuously monitored by telemetry. Mean arterial pressure and heart rate values were calculated over 1-hour periods, and changes were determined by comparing pre- and post-administration diurnal profiles for each animal.
To assess pharmacological effects on the renin system, blood samples were collected via femoral vein puncture using EDTA as anticoagulant before the first dose and on day 8 (2 and 24 hours after the last dose). Plasma was used to measure plasma renin activity and immunoreactive active/total renin concentrations. [2]

Absorption, Distribution and Excretion
Alisartan is absorbed from the gastrointestinal tract, but the absorption rate is low, with a bioavailability of 2.0% to 2.5%. Peak plasma concentrations are reached 1 to 3 hours after administration. Steady-state plasma concentrations are reached after 7 to 8 days of regular administration. Alisartan is primarily excreted via the hepatobiliary route and is eliminated through oxidative metabolism by hepatic cytochrome enzymes. Approximately one-quarter of the absorbed dose is excreted unchanged in the urine. A pharmacokinetic study of radiolabeled alisartan detected 0.6% radioactivity in urine and over 80% in feces, indicating that alisartan is primarily excreted via the fecal route. Approximately 80% of the drug in plasma is unmetabolized alisartan. Alisartan is partially cleared by the kidneys; safety data are not available for patients with creatinine clearance below 30 mL/min. A pharmacokinetic study showed a mean renal clearance of 1280 ± 500 mL/hour in healthy volunteers. Absorption is poor; oral bioavailability is approximately 2.5%. Steady-state plasma concentrations are reached in approximately 7-8 days. Peak plasma concentrations are typically reached within 1-3 hours after oral administration. A significant proportion (85-90%) of the antihypertensive effect is achieved within 2 weeks of treatment initiation. High-fat meals can reduce mean AUC and peak plasma concentration by 71% and 85%, respectively; however, in clinical studies, the timing of drug administration was not consistently correlated with meal times. For more complete data on absorption, distribution, and excretion of alisartan (12 items in total), please visit the HSDB record page. Metabolites/Metabolites: After oral administration, approximately 80% of the drug remains unchanged in plasma. Two major metabolites account for approximately 1-3% of alisartan in plasma. One metabolite is an O-demethylated alcohol derivative, and the other is a carboxylic acid derivative. Small amounts of oxidative and hydrolytic metabolites may also be present in plasma. The amount metabolized from the absorbed dose has not been determined; however, the drug appears to be minimally metabolized in the liver. In vitro studies have shown that CYP isoenzyme 3A4 appears to be the main enzyme responsible for drug metabolism. Furthermore, it is also a substrate of P-glycoproteins. The main metabolic pathway of alisartan involves O-demethylation of the phenylpropoxy side chain or 3-methoxypropoxy, followed by further oxidation to a carboxylic acid derivative. …The two main oxidative metabolites of alisartan account for less than 5% of peak plasma drug concentration. …Biological half-life: The plasma half-life of alisartan is 30 to 40 hours, with a cumulative half-life of approximately 24 hours. …The terminal half-life of radioactive materials and alisartan in plasma is 49 hours and 44 hours, respectively. The terminal half-life is approximately 24-40 hours; significant inter-patient variability has been observed.

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According to reports, the bioavailability of alisartan hemifumarate in cynomolgus monkeys via oral administration was low, similar to that of DS-8108b (bioavailability of 4.1% and 5.3% at doses of 3 mg/kg and 10 mg/kg, respectively).
Alisartan is a hydrophilic molecule (log Pₒcₜ/water = 2.45 at pH 7.4) with high water solubility (>350 mg/mL at pH 7.4). The molecular formula of its free base is C₃₀H₅₃N₃O₆, with a molecular weight of 551.8 g/mol (the molecular weight of hemifumarate is 609.8 g/mol). The pKₐ value of the free base is 9.49. [2]

Hepatotoxicity
Elevated serum transaminase levels during alisartan treatment are uncommon, and no such elevations have been reported in large clinical trials demonstrating its efficacy in treating hypertension. One case of elevated serum transaminase with jaundice was reported in the alisartan registration trial, and several other cases have been reported showing significant serum enzyme elevations during treatment, but with mild symptoms and no jaundice. In most cases, the enzyme elevations are markedly hepatocellular and recover rapidly upon discontinuation of alisartan. Furthermore, the sponsor has received reports of serious liver reactions (including liver failure), and recently published a case report of acute liver injury associated with this drug. The latency period for liver injury is 1 to 6 months, and the injury pattern is usually cholestatic or mixed. Most cases are mild to moderate and recover rapidly upon discontinuation of alisartan. Probability score: C (likely the cause of clinically significant liver injury). Protein Binding The plasma protein binding rate of alisartan is 47-51%.

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Drug Interactions
Furosemide: When alisartan is used in combination with furosemide, the AUC and Cmax of furosemide decrease by approximately 30% and 50%, respectively. Patients taking furosemide may experience a decrease in the efficacy of furosemide after starting alisartan.
Verapamil: 240 mg verapamil combined with 300 mg alisartan increases the Cmax and AUC of alisartan by approximately 2-fold. However, no dose adjustment is required.
Cyclosporine: 200 mg and 600 mg cyclosporine combined with 75 mg alisartan result in an approximately 2.5-fold increase in the Cmax and a approximately 5-fold increase in the AUC of alisartan. Combined use of alisartan and cyclosporine is not recommended.
Ketoconazole: 200 mg ketoconazole twice daily combined with alisartan results in an approximately 80% increase in plasma concentrations of alisartan. A once-daily dose of 400 mg was not studied, but this dose is expected to further increase alisartan blood concentrations. More interaction (complete) data (of 11 items) for alisartan can be found on the HSDB record page. In marmoset studies, no significant adverse reactions to alisartan were observed at doses up to 10 mg/kg/day during an 8-day treatment period. In human pilot studies, alisartan at once-daily doses of 75 mg and 150 mg were reported to be well tolerated for 4 weeks each. No significant changes in clinical chemistry or hematology were observed. Adverse events were mild to moderate, reported in 4 of 8 patients; these included infection (urinary or respiratory tract infection) and nausea in 1 patient. Headache was reported in two patients prior to the start of the study. [2]

[1]. Discovery of DS-8108b, a Novel Orally Bioavailable Renin Inhibitor. ACS Med. Chem. Lett., 2012, 3 (9), pp 754–758.

[2]. Structure-based design of aliskiren, a novel orally effective renin inhibitor.Biochem Biophys Res Commun, 2003, 308(4), 698-705.

[3]. Aliskiren targets multiple systems to alleviate cancer cachexia. Oncol Rep. 2016 Nov;36(5):3014-3022.

[4]. Interplay between brain stem angiotensins and monocyte chemoattractant protein-1 as a novel mechanism for pressor response after ischemic stroke. Neurobiol Dis. 2014 Nov;71:292-304.

[5]. Pharmacokinetics and pharmacodynamics of aliskiren, an oral direct renin inhibitor. Pharmacol Rep. 2008 Sep-Oct;60(5):623-31.

[6]. Aliskiren, a novel orally effective renin inhibitor, provides dose-dependent antihypertensive efficacy and placebo-like tolerability in hypertensive patients. Circulation, 2005, 111(8), 1012-1018.

Therapeutic Uses

Antihypertensive Drug; Renin/Antagonists and Inhibitors
Tekturna is indicated for the treatment of hypertension. It can be used alone or in combination with other antihypertensive drugs. Its use in combination with the maximum dose of an ACE inhibitor has not been adequately studied. /US Product Label Contains/
Drug Warnings
/Black Box Warning/ Warning: Fetal Toxicity. Tekturna should be discontinued as soon as pregnancy is discovered. Drugs that act directly on the renin-angiotensin system may cause harm or even death to the developing fetus.
Use during pregnancy may result in fetal and neonatal morbidity and mortality. This potential risk may persist throughout pregnancy, especially during the second and third trimesters.
Retrospective data have shown that angiotensin-converting enzyme (ACE) inhibitors (a class of drugs that act on the renin-angiotensin-aldosterone (RAA) system) are associated with an increased risk of serious birth defects when taken in early pregnancy.
Excessive hypotension has been rarely reported in patients with uncomplicated hypertension who are taking this drug alone; it has also been occasionally reported when used in combination with other antihypertensive drugs.
For more complete data on drug warnings for alisartan (21 in total), please visit the HSDB record page.

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Pharmacodynamics
Alisartan lowers blood pressure by inhibiting renin. This leads to a range of events that lower blood pressure and reduce the risk of fatal and nonfatal cardiovascular events, including stroke and myocardial infarction.

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Alisartan hemifumarate is a known marketed nonpeptide renin inhibitor used to treat hypertension. In this study, it was used as a reference compound to evaluate the efficacy of the newly discovered inhibitor DS-8108b. [1]
Alisartan (SPP-100) is the first orally effective nonpeptide human renin transition state mimic inhibitor discovered through structure-based drug design. The drug is designed to utilize a novel subpocket (S3sp) in the renin active site, thereby achieving high activity and high selectivity. Its mechanism of action is through mimicking the transition state of the renin-substrate reaction, where the central hydroxyl and amino groups form hydrogen bonds with the catalytic aspartic acid residues (Asp32 and Asp215) of renin. The drug is being developed for the treatment of hypertension and related cardiovascular diseases. In clinical practice, an independent study (submitted) showed that once-daily administration of 300 mg alisartan had similar efficacy and tolerability in lowering blood pressure compared to once-daily administration of 100 mg losartan, an angiotensin II receptor blocker. [2]

C₃₀H₅₃N₃O₆

551.76

551.393

173334-57-1

Aliskiren hemifumarate;173334-58-2;Aliskiren hydrochloride;173399-03-6;Aliskiren-d6 hydrochloride;1246815-96-2;Aliskiren fumarate;1196835-68-3;Aliskiren-d6 hemifumarate

5493444

White to light yellow solid powder

1.1±0.1 g/cm3

748.4±60.0 °C at 760 mmHg

>95

406.4±32.9 °C

0.0±2.6 mmHg at 25°C

1.514

2.74

4

7

19

39

717

4

CC(C)[C@@H](CC1=CC(=C(C=C1)OC)OCCCOC)C[C@@H]([C@H](C[C@@H](C(C)C)C(=O)NCC(C)(C)C(=O)N)O)N

UXOWGYHJODZGMF-QORCZRPOSA-N

InChI=1S/C30H53N3O6/c1-19(2)22(14-21-10-11-26(38-8)27(15-21)39-13-9-12-37-7)16-24(31)25(34)17-23(20(3)4)28(35)33-18-30(5,6)29(32)36/h10-11,15,19-20,22-25,34H,9,12-14,16-18,31H2,1-8H3,(H2,32,36)(H,33,35)/t22-,23-,24-,25-/m0/s1

(2S,4S,5S,7S)-5-amino-N-(3-amino-2,2-dimethyl-3-oxopropyl)-4-hydroxy-7-[[4-methoxy-3-(3-methoxypropoxy)phenyl]methyl]-8-methyl-2-propan-2-ylnonanamide

CGP-60536B SPP100 CGP 60536 SPP-100CGP60536B SPP 100

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Ethanol : ~100 mg/mL (~181.24 mM)
DMSO : ~100 mg/mL (~181.24 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.53 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (4.53 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (4.53 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)