Cilazapril targets angiotensin-converting enzyme (ACE), a zinc metallopeptidase that converts angiotensin I to the potent vasoconstrictor angiotensin II and degrades the vasodilator bradykinin. Cilazapril is a prodrug that is hydrolyzed in vivo to its active form, cilazaprilat, which inhibits ACE by binding to its active site zinc ion.

In vitro, cilazaprilat (the active metabolite) demonstrates potent ACE inhibition with an IC50 of 1.9 nM against rabbit lung ACE. The compound inhibits the ability of ACE to cleave bonds of angiotensin I and Hip-His-Leu. Cilazapril has been studied in various in vitro assays comparing its potency to other ACE inhibitors such as enalaprilat and lisinopril. Its sub-nanomolar potency makes it one of the most potent ACE inhibitors in its class.

In vivo, cilazapril is effective in lowering blood pressure in hypertensive patients and improving hemodynamics in heart failure patients. Clinically demonstrated to improve aortic compliance (ΔPWV -1.7 m/sec) and exercise tolerance in heart failure (+62.2 sec vs placebo). Cilazaprilat possesses a prolonged terminal elimination half-life of approximately 30-50 hours, which is attributed to saturable, high-affinity binding to ACE and enables once-daily dosing.

In vitro enzyme assays for ACE inhibition typically use rabbit lung ACE or human recombinant ACE as the enzyme source and a synthetic substrate such as hippuryl-histidyl-leucine (HHL) or furanacryloyl-phenylalanyl-glycyl-glycine (FAPGG). The enzyme is incubated with the substrate and varying concentrations of cilazaprilat. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance (for FAPGG) or by HPLC quantification of the hippuric acid product (for HHL). IC50 values are calculated from dose-response curves.

Cellular assays for ACE inhibitors typically use endothelial cells or smooth muscle cells that express ACE. Cells are treated with cilazapril or cilazaprilat, and angiotensin I-induced contraction or angiotensin II production is measured. For example, cells are incubated with angiotensin I in the presence or absence of the test compound, and the amount of angiotensin II produced is quantified by ELISA or radioimmunoassay. The degree of inhibition of angiotensin II production is used to calculate IC50 values.

In vivo animal studies for ACE inhibitors typically use spontaneously hypertensive rats (SHR) or angiotensin I-challenged normotensive rats. Animals are administered cilazapril orally at various doses, and blood pressure is measured by tail-cuff plethysmography or telemetry. For angiotensin I challenge, rats are given angiotensin I intravenously, and the pressor response is measured. The degree of inhibition of the pressor response is calculated. Chronic studies assess the compound's ability to prevent hypertension development or reverse established hypertension.

Absorption, Distribution and Excretion
Cilaprila's plasma concentration reaches peak within two hours after administration. Cilaprila is excreted unchanged via the kidneys. Following intravenous administration of 2.5 mg cialaprila, the total urinary recovery rate is 91%. The total clearance is 12.3 L/h, and the renal clearance is 10.8 L/h. Following oral administration of 2.5 mg cialaprila, the total urinary recovery rate is 52.6%. Biological Half-Life Following intravenous administration of 2.5 mg cialaprila, the half-lives at 1–4 hours and 1–7 days are 0.90 hours and 46.2 hours, respectively.

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Cilazapril is orally bioavailable as a prodrug. Following oral administration, it is absorbed from the gastrointestinal tract and hydrolyzed in the liver to the active metabolite, cilazaprilat. Cilazaprilat possesses a prolonged terminal elimination half-life of approximately 30-50 hours, attributed to saturable, high-affinity binding to ACE. The compound is eliminated primarily via the kidneys. Its long half-life supports once-daily dosing in clinical practice.

Protein Binding
Following administration of 1 to 5 mg of cilazapril, the maximum ACE inhibition rate exceeded 90%. Following administration of 0.5 mg of cilazapril, the maximum ACE inhibition rate was 70% to 80%. A dose-proportioning relationship was observed following administration of 1 to 5 mg of cilazapril. A significant non-proportioning relationship was observed at the 0.5 mg dose, reflecting drug binding to ACE. Higher doses of cilazapril were associated with a longer duration of maximum ACE inhibition.

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Cilazapril is generally well-tolerated in clinical use. Common side effects include cough, dizziness, and hypotension, which are class effects of ACE inhibitors. Rare but serious side effects include angioedema and hyperkalemia. The compound has been extensively studied in clinical trials for hypertension and heart failure. Its safety profile is well-established, and it is approved for clinical use in many countries.

J Pharmacol Sci.2004 Jan;94(1):67-72;Life Sci.1999;64(3):PL27-39.

Cilapril is a pyridazine diazepam compound formed by the condensation of the carboxyl group of cilazapril with ethanol. It is a drug used to treat hypertension and heart failure. It is a prodrug, an antihypertensive drug, and an EC 3.4.15.1 (peptidyl dipeptidase A) inhibitor. It is an ethyl ester, a pyridazine diazepam compound, and a dicarboxylic acid monoester. Its function is related to cilazapril. Cilapril is an angiotensin-converting enzyme inhibitor (ACE inhibitor) used to treat hypertension and heart failure. It belongs to the angiotensin-converting enzyme inhibitor (ACE inhibitor) class of drugs. It is a prodrug that is hydrolyzed after absorption to produce its main metabolite, cilazapril. In Canada and other countries, it is marketed as Inhibace; in some European countries, it is marketed as Vascace and Dynorm, among many other names. These products are not sold in the United States. Cilapril monohydrate is a pyrazine angiotensin-converting enzyme (ACE) inhibitor with antihypertensive effects. As a prodrug, cilazapril is rapidly metabolized in the liver to cilazaprilat. Cialaprilat competitively binds to and inhibits the activity of ACE, thereby blocking the conversion of angiotensin I to angiotensin II. This prevents the potent vasoconstriction of angiotensin II, leading to vasodilation. Cialaprilat also reduces adrenal cortex aldosterone secretion for angiotensin II, thereby increasing sodium excretion and consequently water excretion. The anhydrous form of cilazapril is the pyrazine angiotensin-converting enzyme (ACE) inhibitor cilazapril and has antihypertensive effects. As a prodrug, cilazapril is rapidly metabolized in the liver to cilazaprilat. Cialaprilat competitively binds to and inhibits the activity of angiotensin-converting enzyme (ACE), thereby blocking the conversion of angiotensin I to angiotensin II. This prevents the potent vasoconstriction of angiotensin II, leading to vasodilation. Cilapril also reduces adrenal cortex aldosterone secretion from angiotensin II, thereby increasing sodium excretion and consequently water excretion. Cilapril is one of the angiotensin-converting enzyme inhibitors (ACE inhibitors) used to treat hypertension. It is a prodrug that is hydrolyzed after absorption to its main metabolite, cialapril. Drug Indications Cilapril is an angiotensin-converting enzyme inhibitor (ACE inhibitor) used to treat hypertension and heart failure. FDA Label Mechanism of Action Cilapril is a pyridazine ACE inhibitor. It competitively binds to angiotensin-converting enzyme with angiotensin I, thereby blocking the conversion of angiotensin I to angiotensin II. Because angiotensin II is a vasoconstrictor and a negative feedback regulator of renin activity, a decrease in angiotensin II levels leads to a decrease in blood pressure, an increase in renin activity, and stimulation of the baroreceptor reflex mechanism. Kallikrein II is an enzyme that degrades the vasodilator bradykinin and, like angiotensin-converting enzyme (ACE), can also be inhibited.

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Pharmacodynamics
Cilapril inhibits the production of angiotensin II. By inhibiting the production of angiotensin II, it reduces the reabsorption of sodium and water (via aldosterone) and decreases vasoconstriction. The combined result of these effects is reduced vascular resistance, thereby lowering blood pressure. Based on urinary recovery data, the absolute bioavailability of cilazapril after oral administration is 57%. (The absolute bioavailability of cilazapril after oral administration is 19%.) Eating immediately before taking cilazapril reduces the mean peak plasma concentration of cilazapril by 29%, delays the time to peak concentration by 1 hour, and reduces the bioavailability of cilazapril by 14%. These pharmacokinetic changes have little effect on the inhibitory effect of plasma ACE.

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Cilazapril (Ro 31-2848) is a potent ACE inhibitor prodrug used for the treatment of hypertension and congestive heart failure. It is hydrolyzed in vivo to cilazaprilat, which has an IC50 of 1.9 nM against ACE. Cilazaprilat has a prolonged terminal elimination half-life of 30-50 hours, enabling once-daily dosing. The compound has been clinically demonstrated to improve aortic compliance and exercise tolerance in heart failure patients. It is available as Inhibace in various markets.

C22H31N3O5

417.5

417.226

88768-40-5

Cilazapril monohydrate;92077-78-6

56330

Typically exists as solid at room temperature

1.26g/cm3

598.1ºC at 760 mmHg

95-97ºC

315.5ºC

3.73E-15mmHg at 25°C

1.591

1.862

2

7

9

30

608

3

C([C@@H]1CCCN2CCC[C@@H](C(N12)=O)N[C@H](C(=O)OCC)CCC1C=CC=CC=1)(=O)O

HHHKFGXWKKUNCY-FHWLQOOXSA-N

InChI=1S/C22H31N3O5/c1-2-30-22(29)18(13-12-16-8-4-3-5-9-16)23-17-10-6-14-24-15-7-11-19(21(27)28)25(24)20(17)26/h3-5,8-9,17-19,23H,2,6-7,10-15H2,1H3,(H,27,28)/t17-,18-,19-/m0/s1

(4S,7S)-7-[[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino]-6-oxo-1,2,3,4,7,8,9,10-octahydropyridazino[1,2-a]diazepine-4-carboxylic acid

Ro 31 2848 Ro 31-2848 Ro 312848 Ro-31-2848 Ro312848Cilazapril Vascace Cilazaprilum UNII-8Q9454114Q

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)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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