Absorption,excretion, and metabolism of a potential GABA-Aα2/3 receptor modulator in rats

1. 4-Amino-8-(2,5-dimethoxyphenyl)-N-propylcinnoline-3-carboxamide (AZD6280) is a selective GABA-A_α2/3 receptor modulator under development for the treatment of generalized anxiety disorders. Absorption, metabolism, and excretion of [¹⁴C]-AZD6280 was studied in rats following a single oral (7?mg/kg) or intravenous (i.v., 1?mg/kg) administration of [¹⁴C]-AZD6280.

2. The results from the bile duct-cannulated study revealed that AZD6280 was well-absorbed in rats.

3. The pharmacokinetic analysis was conducted using unlabelled parent drug that was rapidly absorbed (plasma T_max ~1?h) and exhibited a mean apparent terminal half-life of ~4.2?h.

4. The overall mean recoveries in the excreta were 98.6% and 100.3% after oral and i.v. administration of [¹⁴C]-AZD6280, respectively. The major route for elimination of [¹⁴C]-AZD6280 and its metabolites was through faeces.

5. The radiochromatographic analysis of the excreta demonstrated that AZD6280 underwent extensive biotransformation. A total of 28 metabolites of AZD6280 were detected and profiled in urine, bile, and faeces in this study. The structures of metabolites were elucidated by high-resolution tandem mass spectrometry. Similar metabolite profiles were observed in rats given AZD6280 orally or intravenously.

     

Metabolic disposition of gefitinib,an epidermal growth factor receptor tyrosine kinase inhibitor,in rat,dog and man

1.?Following oral administration of [¹⁴C]-gefitinib to albino and pigmented rats, radioactivity was widely and rapidly distributed, with the highest levels being found in liver, kidney, lung and gastrointestinal tract, but with only low levels penetrating the brain. Levels of radioactivity persisted in melanin-containing tissues (pigmented eye and skin).

2.?Binding to plasma proteins was high (86–94%) across the range of species examined and was 91% in human plasma. Substantial binding occurred to both human serum albumin and α-1 acid glycoprotein.

3.?Following oral and intravenous administration of [¹⁴C]-gefitinib, excretion of radioactivity by rat, dog and human occurred predominantly via the bile into faeces, with <7% of the dose being eliminated in urine.

4.?In all three species, gefitinib was cleared primarily by metabolism. In rat, morpholine ring oxidation was the major route of metabolism, leading to the formation of M537194 and M608236 as the main biliary metabolites. Morpholine ring oxidation, together with production of M523595 by O-demethylation of the quinazoline moiety, were the predominant pathways in dog, with oxidative defluorination also occurring to a lesser degree.

5.?Pathways in healthy human volunteers were similar to dog, with O-demethylation and morpholine ring oxidation representing the major routes of metabolism.     

Disposition and metabolism of TAK-438 (vonoprazan fumarate), a novel potassium-competitive acid blocker,in rats and dogs

1.?Following oral administration of [¹⁴C]TAK-438, the radioactivity was rapidly absorbed in rats and dogs. The apparent absorption of the radioactivity was high in both species.

2.?After oral administration of [¹⁴C]TAK-438 to rats, the radioactivity in most tissues reached the maximum at 1-hour post-dose. By 168-hour post-dose, the concentrations of the radioactivity were at very low levels in nearly all the tissues. In addition, TAK-438F was the major component in the stomach, whereas TAK-438F was the minor component in the plasma and other tissues. High accumulation of TAK-438F in the stomach was observed after oral and intravenous administration.

3.?TAK-438F was a minor component in the plasma and excreta in both species. Its oxidative metabolite (M-I) and the glucuronide of a secondary metabolite formed by non-oxidative metabolism of M-I (M-II-G) were the major components in the rat and dog plasma, respectively. The glucuronide of M-I (M-I-G) and M-II-G were the major components in the rat bile and dog urine, respectively, and most components in feces were other unidentified metabolites.

4.?The administered radioactive dose was almost completely recovered. The major route of excretion of the drug-derived radioactivity was via the feces in rats and urine in dogs.     

Pharmacokinetics of the selective prostacyclin receptor agonist selexipag in rats,dogs and monkeys

1.?This study examined the pharmacokinetics, distribution, metabolism and excretion of the selective prostacyclin receptor agonist selexipag (NS-304; ACT-293987) and its active metabolite MRE-269 (ACT-33679). The compounds were investigated following oral and/or intravenous administration to intact rats, dogs and monkeys, and bile-duct-cannulated rats and dogs.

2.?After oral administration of [¹⁴C]selexipag, selexipag was well absorbed in rats and dogs with total recoveries of over 90% of the dose, mainly in the faeces. Biliary excretion was the major elimination pathway for [¹⁴C]MRE-269 as well as [¹⁴C]selexipag, while renal elimination was of little importance. [¹⁴C]Selexipag-related radioactivity was secreted into the milk in lactating rats.

3.?Plasma was analysed for total radioactivity, selexipag and MRE-269 in rats and monkeys. Selexipag was negligible in rat plasma due to extensive metabolism, and MRE-269 was present in rat and monkey plasma. A species difference was clearly evident when selexipag was incubated in rat, dog and monkey plasma.

4.?Total radioactivity was rapidly distributed to tissues. The highest concentrations were found in the bile duct and liver without significant accumulation or persistence, while there was limited melanin-associated binding, penetration of the blood–brain barrier and placental transfer of drug-related materials.     

The Metabolism of Isopropyl Oxitol in Rat and Dog

1. An intraperitoneal dose of [¹⁴C]isopropyl Oxitol is rapidly metabolized in the rat.

2. The major routes of excretion of radioactivity are the urine (73% dose) and in the expired air as [¹⁴C]carbon dioxide (14%).

3. The major urinary metabolites were characterized as isopropoxyacetic acid (30% of the urinary radioactivity), N-isopropoxyacetyl glycine (46%) and ethanediol (13%).

4. The metabolism of the compound in the dog is similar to that in the rat.     

Pharmacokinetics,metabolism and excretion of an inhibitor of inducible nitric oxide synthase,L-NIL-TA,in dog

1.?The pharmacokinetics, metabolism and excretion of L-NIL-TA, an inducible nitric oxide synthase inhibitor, were investigated in dog.

2.?The dose of [¹⁴C]L-NIL-TA was rapidly absorbed and distributed after oral and intravenous administration (5?mg?kg^?1), with C_max of radioactivity of 6.45–7.07?μg equivalents?g^?1 occurring at 0.33–0.39-h after dosing. After oral and intravenous administration, radioactivity levels in plasma then declined with a half-life of 63.1 and 80.6-h, respectively.

3.?Seven days after oral and intravenous administrations, 46.4 and 51.5% of the radioactive dose were recovered in urine, 4.59 and 2.75% were recovered in faeces, and 22.4 and 22.4% were recovered in expired air, respectively. The large percentages of radioactive dose recovered in urine and expired air indicate that [¹⁴C]L-NIL-TA was well absorbed in dogs and the radioactive dose was cleared mainly through renal elimination. The mean total recovery of radioactivity over 7 days was approximately 80%.

4.?Biotransformation of L-NIL-TA occurred primarily by hydrolysis of the 5-aminotetrazole group to form the active drug L-N6-(1-iminoethyl)lysine (NIL or M3), which was further oxidized to the 2-keto acid (M5), the 2-hydroxyl acid (M1), an unidentified metabolite (M2) and carbon dioxide. The major excreted products in urine were M1 and M2, representing 22.2 and 21.2% of the dose, respectively.     

Metabolic disposition of gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor, in rat, dog and man

Following oral administration of [14C]-gefitinib to albino and pigmented rats, radioactivity was widely and rapidly distributed, with the highest levels being found in liver, kidney, lung and gastrointestinal tract, but with only low levels penetrating the brain. Levels of radioactivity persisted in melanin-containing tissues (pigmented eye and skin). Binding to plasma proteins was high (86-94%) across the range of species examined and was 91% in human plasma. Substantial binding occurred to both human serum albumin and alpha-1 acid glycoprotein. Following oral and intravenous administration of [14C]-gefitinib, excretion of radioactivity by rat, dog and human occurred predominantly via the bile into faeces, with < 7% of the dose being eliminated in urine. In all three species, gefitinib was cleared primarily by metabolism. In rat, morpholine ring oxidation was the major route of metabolism, leading to the formation of M537194 and M608236 as the main biliary metabolites. Morpholine ring oxidation, together with production of M523595 by O-demethylation of the quinazoline moiety, were the predominant pathways in dog, with oxidative defluorination also occurring to a lesser degree. Pathways in healthy human volunteers were similar to dog, with O-demethylation and morpholine ring oxidation representing the major routes of metabolism.     

Comparison of celecoxib metabolism and excretion in mouse,rabbit, dog,cynomolgus monkey and rhesus monkey

1. The metabolism and excretion of celecoxib, a specific cyclooxygenase 2 (COX-2) inhibitor, was investigated in mouse, rabbit,the EM(extensive) and PM(poor metabolizer) dog, and rhesus and cynomolgus monkey. 2. Some sex and species differences were evident in the disposition of celecoxib. After intravenous (i.v.) administration of [¹⁴C]celecoxib, the major route of excretion of radioactivity in all species studied was via the faeces: EM dog (80.0%), PM dog (83.4%), cynomolgus monkey (63.5%), rhesus monkey (83.1%). After oral administration, faeces were the primary route of excretion in rabbit (72.2%) and the male mouse (71.1%), with the remainder of the dose excreted in the urine. After oral administration of [¹⁴C]celecoxib to the female mouse, radioactivity was eliminated equally in urine (45.7%) and faeces (46.7%). 3. Biotransformation of celecoxib occurs primarily by oxidation of the aromatic methyl group to form a hydroxymethyl metabolite, which is further oxidized to the carboxylic acid analogue. 4. An additional phase I metabolite (phenyl ring hydroxylation) and a glucuronide conjugate of the carboxylic acid metabolite was produced by rabbit. 5. The major excretion product in urine and faeces of mouse, rabbit, dog and monkey was the carboxylic acid metabolite of celecoxib.     

Absorption, excretion, and metabolism of a potential GABA-A α2/3 receptor modulator in rats

4-Amino-8-(2,5-dimethoxyphenyl)-N-propylcinnoline-3-carboxamide (AZD6280) is a selective GABA-A(α2/3) receptor modulator under development for the treatment of generalized anxiety disorders. Absorption, metabolism, and excretion of [(14)C]-AZD6280 was studied in rats following a single oral (7 mg/kg) or intravenous (i.v., 1 mg/kg) administration of [(14)C]-AZD6280. The results from the bile duct-cannulated study revealed that AZD6280 was well-absorbed in rats. The pharmacokinetic analysis was conducted using unlabelled parent drug that was rapidly absorbed (plasma T(max) ~1 h) and exhibited a mean apparent terminal half-life of ~4.2 h. The overall mean recoveries in the excreta were 98.6% and 100.3% after oral and i.v. administration of [(14)C]-AZD6280, respectively. The major route for elimination of [(14)C]-AZD6280 and its metabolites was through faeces. The radiochromatographic analysis of the excreta demonstrated that AZD6280 underwent extensive biotransformation. A total of 28 metabolites of AZD6280 were detected and profiled in urine, bile, and faeces in this study. The structures of metabolites were elucidated by high-resolution tandem mass spectrometry. Similar metabolite profiles were observed in rats given AZD6280 orally or intravenously.     

The Metabolism of Tolamolol* in the Mouse,Rat, Guinea-pig,Rabbit and Dog

1. [³H, ¹⁴C]Tolamolol was well absorbed after oral administration to mice, rats, guinea-pigs, rabbits and dogs.

2. The major route for excretion of. radioactivity by mice, rats and guineapigs was the faeces; in rabbits the major route was the urine. Dogs excreted similar amounts of radioactivity by both routes. Biliary excretion of radioactivity by the rat and guineapig was demonstrated.

3. Tolamolol was extensively metabolized by all five species. The major metabolite in mice, rats, guinea-pigs and rabbits was the product of hydroxylation of the tolyl ring, which was excreted as such and as the glucuronide and sulphate conjugates.

4. In the dog the major metabolite was the acid resulting from hydrolysis of the carbamoyl group. This acid was also excreted by the rabbit, but was only a minor metabolite in the other species studied.     

The metabolism in animals and man of oxmetidine—A new histamine H2-receptor antagonist

1. The absorption, distribution, metabolism and excretion of [¹⁴C]oxmetidine in rat, dog and man has been studied following both i.v. and oral administration.

2. Excretion is rapid and essentially complete in all three species. The biliary route is predominant.

3. Distribution of radioactivity is widespread although none is seen in the brain.

4. Metabolite patterns in urine from rat, dog and man have been compared by thin-layer chromatography.

5. Metabolite patterns in urine and bile from rat and dog have been compared by high-pressure liquid chromatography.

6. Six major metabolites have been isolated and identified including two O-glucuronides and one N-glucuronide.     

Metabolism of Linoleamides: II. Absorption,Distribution, Excretion and Metabolism of N-[α-Phenyl-β-(p-tolyl)ethyl] linoleamide

1. Absorption, distribution, excretion and metabolism of (-)N-[α-phenyl-β-(p-tolyl)ethyl][¹⁴C]linoleamide (¹⁴C-PTLA) were studied in rats and dogs. Faecal excretion of PTLA was studied in dogs and men by g.l.c.

2. ¹⁴C-PTLA (10 mg/kg) given orally to rats resulted in urinary and faecal excretion of radioactivity of 2 and 93 %, respectively, by male rats and 8 and 87% by female rats in 48 h. Faecal excretion of PTLA in men was similar to that in rats.

3. Distribution of radioactivity in rats and dogs after oral administration of ¹⁴C-PTLA showed that a major part of the dose was not absorbed.

4. N-[α-Phenyl-β-(p-tolyl)ethyl]succinic acid monoamide and N-[α-phenyl-β-(p-tolyl)ethyl]glutaric acid monoamide were detected in the urine of rats dosed orally with ¹⁴C-PTLA.     

Disposition of α-[(dimethylamino)methyl]-2-(3-ethyl-5-methyl-4-isoxazolyl)-1H-indole-3- methanol (59–801), a hypoglycaemic agent,in rats,dogs and monkeys

1. The disposition of α-[(dimethylamino)methyl]-2-(3-ethyl-5-methyl-4-isoxazolyl)-1 H-[3-¹⁴C]indole-3-methanol, an oral hypoglycaemic drug, has been studied in the rat, dog and monkey.

2. Oral doses of the drug were almost completely absorbed. The rate of absorption was rapid in the rat but less rapid in dog and monkey. Due to first-pass effect, the absolute bioavailability of the drug was incomplete and ranged from 60–75% in the monkey to 90% in the dog.

3. Intravenous as well as oral doses of the radiolabelled drug were rapidly and extensively distributed to body tissues. In rat, concentrations of radioactivity in all tissues except the brain exceeded, or were similar to, corresponding blood levels. Tissue and blood radioactivity levels were higher in female than in male rats, and increased disproportionately with increasing dose.

4. The drug was partially metabolized before excretion, the extent of metabolism ranging from ca. 50% in the rat to 90% in the monkey. Although only a limited number of animals were used, metabolism appeared to be saturable within the dose range studied in dog and monkey but not in rat. The half-life of unchanged drug was dose-independent in the rat (1.4 h), but tended to increase with increasing dose in the dog (4.1–7.2 h) and monkey (2.1–4.5 h).

5. In all three species, the administered radioactivity was recovered predominantly in urine, although biliary excretion also played an important role in drug elimination. Recovery of dose was essentially complete within 1–2 days.     

Absorption,metabolism and excretion studies on clavulanic acid in the rat and dog

1. At least one third of an oral dose of sodium [G-¹⁴C]clavulanate was absorbed by rat and dog. Excretion of radioactivity was rapid in both species.

2. In addition to urinary and faecal excretion of radioactivity, appreciable elimination of ¹⁴CO₂ occurred, particularly in the rat. This was produced in part by the action of the gut microflora.

3. In the rat, only a small proportion of the radioactive dose was secreted in the bile.

4. The major metabolite in urine was identified as l-amino-4-hydroxybutan-2-one. Clavulanic acid was also a major component in urine.     

The metabolism of carfecillin in rat,dog and man

1. The absorption of the phenol moiety of [phenol-¹⁴C]carfecillin following oral administration to rat, dog and man was extensive, since 95%, 73% and 99% of the administered radioactivity respectively was recovered in the urine. In contrast, less than half of the carbenicillin moiety of carfecillin was absorbed after oral administration, as judged by excretion studies using [carbenicillin-¹⁴C]carfecillin in intact and bile-duct cannulated animals.

2. The patterns of radiometabolites in the urines of rat, dog and man following single oral administration of [phenol-¹⁴C]carfecillin were determined by chromatography and radioassay. In two men, the majority of a dose was excreted as phenylsulphate (71%) and phenylglucuronide (16%) with the sulphate and glucuronic acid conjugates of quinol representing small amounts of the urinary radioactivity. Similar metabolic patterns were observed in the rat and dog following oral administration of either [¹⁴C]phenol or [phenol-¹⁴C]carfecillin, although some saturation of sulphate conjugation was apparent at the dose levels employed.     

Disposition and metabolism of amosulalol hydrochloride,a new combined α- and β-adrenoceptor blocking agent,in rats,dogs and monkeys

1. The disposition and metabolism of amosulalol hydrochloride, a combined α- and β-adrenoceptor blocking agent, were studied in rats, dogs and monkeys.

2. After oral administration of [¹⁴C]amosulalol hydrochloride, the plasma concentration of radioactivity reached a maximum at 05 to 1 h in all species and declined with half-lives of about 2 h in both rats and monkeys, and of about 4 h in dogs. The ratios of unchanged drug to total radioactivity in the rat and dog plasma were 8 and 43% at 05 h after administration, respectively. The radioactivity in the rat tissues was high in the liver, kidney, blood and pancreas after oral administration.

3. Following oral dosage, the urinary excretion of radioactivity was 26-34% of the dose in rats, 45% in dogs and 46% in monkeys in 48 h. The biliary excretion after oral dosage amounted to 66% and 41% in rats and dogs, respectively.

4. Six metabolites were isolated and identified from the urine of rats and dogs. They were derived from one or two of the following pathways: I, hydroxylation of the 2-methyl group of the methylbenzenesulphonamide ring; II, demethylation of the o-methoxy group of the methoxyphenoxy ring; III, hydroxylation at the 4 or 5 position of the methoxy-phenoxy ring; IV, oxidative cleavage of the C—N bond yielding o-methoxyphenoxy acetic acid. Moreover, some metabolites were metabolized to glucuronide or sulphate.     

The Metabolism of Talampicillin in Rat,Dog and Man

1. After administration of [phthalidyl-¹⁴]talampicillin (Talpen® to rat. dog and man, radioactivity was excreted mainly in the urine (90%, 86% and 98% in rat, dog and man respectively).

2. After administration of [ampicillin-¹⁴C]talampicillin, radioactivity was excreted in the urine of rats and dogs to a lesser extent (35% in both species) and only a small proportion of the dose was excreted in the bile (6% in rats, less than 0·1% in dogs).

3. The pattern of radiometaboletes was very similar in extracts of the urines of rat, dog and man dosed orally with [phthalidyl-14C]talampicillin. The major metabolite was 2-hydroxymethylbenzoic acid.

4. Unchanged talampicillin was present in the hepatic portal vein blood of dog and thus reached the liver, whereas in rat, no parent compound could be detected in portal vein blood. This result may help to explain differences in toxicity of the compound in rat and dog.

5. Studies in vitro showed that the intestinal wall is an important site of hydrolysis of talampicillin in rat and dog.     

Absorption,metabolism and excretion of [14C]gemigliptin,a novel dipeptidyl peptidase 4 inhibitor,in humans

Abstract

1. Gemigliptin (formerly known as LC15-0444) is a newly developed dipeptidyl peptidase 4 inhibitor for the treatment of type 2 diabetes. Following oral administration of 50?mg (5.4?MBq) [¹⁴C]gemigliptin to healthy male subjects, absorption, metabolism and excretion were investigated.

2. A total of 90.5% of administered dose was recovered over 192?hr postdose, with 63.4% from urine and 27.1% from feces. Based on urinary recovery of radioactivity, a minimum 63.4% absorption from gastrointestinal tract could be confirmed.

3. Twenty-three metabolites were identified in plasma, urine and feces. In plasma, gemigliptin was the most abundant component accounting for 67.2%?～?100% of plasma radioactivity. LC15-0636, a hydroxylated metabolite of gemigliptin, was the only human metabolite with systemic exposure more than 10% of total drug-related exposure. Unchanged gemigliptin accounted for 44.8%?～?67.2% of urinary radioactivity and 27.7%?～?51.8% of fecal radioactivity. The elimination of gemigliptin was balanced between metabolism and excretion through urine and feces. CYP3A4 was identified as the dominant CYP isozyme converting gemigliptin to LC15-0636 in recombinant CYP/FMO enzymes.     

Pharmacokinetics,distribution, and disposition of esaxerenone,a novel,highly potent and selective non-steroidal mineralocorticoid receptor antagonist,in rats and monkeys

1.?Esaxerenone (CS-3150) is a novel non-steroidal mineralocorticoid receptor antagonist. The pharmacokinetics, tissue distribution, excretion, and metabolism of esaxerenone were evaluated in rats and monkeys.

2.?Following intravenous dosing of esaxerenone at 0.1–3?mg/kg, the total body clearance and the volume of distribution were 3.53–6.69?mL/min/kg and 1.47–2.49?L/kg, respectively, in rats, and 2.79–3.69?mL/min/kg and 1.34–1.54?L/kg, respectively, in monkeys. The absolute oral bioavailability was 61.0–127% in rats and 63.7–73.8% in monkeys.

3.?After oral administration of [¹⁴C]esaxerenone, the radioactivity was distributed widely to tissues, with the exception of a low distribution to the central nervous system. Both in rats and in monkeys, following oral administration of [¹⁴C]esaxerenone the main excretion route of the radioactivity was feces.

4.?Five initial metabolic pathways in rats and monkeys were proposed to be N-dealkylation, carboxylation, hydroxymethylation, O-glucuronidation, and O-sulfation. The oxidized metabolism was predominant in rats, while both oxidation and glucuronidation were predominant in monkeys.     

Influence of Route of Administration on Metabolism of [14C]Nicotine in Four Species

Abstract

1. The metabolism of [¹⁴C]nicotine has been studied in four species of animals, rabbit, rat, cat and squirrel monkey, after administration by different routes.

2. Intravenous injection of 4 μg/kg [¹⁴C]nicotine every 60 s for 1 h results in peak blood levels of approximately 100 ng/ml in all species but the rabbit. [¹⁴C]Cotinine levels in blood vary widely between species.

3. Subcutaneous injection of 0·4 mg/kg [¹⁴C]nicotine produces similar peak blood nicotine levels but the time course, for a given species, is different.

4. Intragastric instillation of 1 mg/kg [¹⁴C]nicotine to the cat and rabbit results in much lower levels of [¹⁴C]nicotine in blood and relatively high levels of [¹⁴C]-cotinine.

5. Urinary excretion data indicate that, irrespective of route, the squirrel monkey excretes only a small proportion of the dose into urine during the period of experiment, of which the major proportion is [¹⁴C]nicotine. The cat, in contrast, excretes a relatively large proportion of the dose during the experimental period though only a minor proportion of the radioactivity is due to [¹⁴C]nicotine or [¹⁴C]cotinine.

6. All four species are potentially useful for model experiments with nicotine, though metabolism of nicotine by squirrel monkey is most similar to man.