Open-label, single-center, phase I trial to investigate the mass balance and absolute bioavailability of the highly selective oral MET inhibitor tepotinib in healthy volunteers

Tepotinib (MSC2156119J) is an oral, potent, highly selective MET inhibitor. This open-label, phase I study in healthy volunteers (EudraCT 2013-003226-86) investigated its mass balance (part A) and absolute bioavailability (part B). In part A, six participants received tepotinib orally (498 mg spiked with 2.67 MBq [¹⁴C]-tepotinib). Blood, plasma, urine, and feces were collected up to day 25 or until excretion of radioactivity was <1% of the administered dose. In part B, six participants received 500 mg tepotinib orally as a film-coated tablet, followed by an intravenous [¹⁴C]-tepotinib tracer dose (53–54 kBq) 4 h later. Blood samples were collected until day 14. In part A, a median of 92.5% (range, 87.1–96.9%) of the [¹⁴C]-tepotinib dose was recovered in excreta. Radioactivity was mainly excreted via feces (median, 78.7%; range, 69.4–82.5%). Urinary excretion was a minor route of elimination (median, 14.4% [8.8–17.7%]). Parent compound was the main constituent in excreta (45% [feces] and 7% [urine] of the radioactive dose). M506 was the only major metabolite. In part B, absolute bioavailability was 72% (range, 62–81%) after oral administration of 500 mg tablets (the dose and formulation used in phase II trials). In conclusion, tepotinib and its metabolites are mainly excreted via feces; parent drug is the major eliminated constituent. Oral bioavailability of tepotinib is high, supporting the use of the current tablet formulation in clinical trials. Tepotinib was well tolerated in this study with healthy volunteers.

Pharmacokinetics and excretion balance of OR-1896, a pharmacologically active metabolite of levosimendan, in healthy men

OBJECTIVE

To investigate the pharmacokinetics and excretion balance of [(14)C]-OR-1896, a pharmacologically active metabolite of levosimendan, in six healthy male subjects. In addition, pharmacokinetic parameters of total radiocarbon and the deacetylated congener, OR-1855, were determined.

METHODS

OR-1896 was administered as a single intravenous infusion of 200 microg of [(14)C]-OR-1896 (specific activity 8.6 MBq/mg) over 10 min. The pharmacokinetic parameters were calculated by three-compartmental methods.

RESULTS

During the 14-day collection of urine and faeces, excretion (+/-S.D.) averaged 94.2+/-1.4% of the [(14)C]-OR-1896 dose. Mean recovery of radiocarbon in urine was 86.8+/-1.9% and in faeces 7.4+/-1.5%. Mean terminal elimination half-life of OR-1896 (t(1/2)) was 70.0+/-44.9 h. Maximum concentrations of OR-1855 were approximately 30% to that of OR-1896. Total clearance and the volume of distribution of OR-1896 were 2.0+/-0.4 l/h and 175.6+/-74.5l, respectively. Renal clearances of OR-1896 and OR-1855 were 0.9+/-0.4 l/h and (5.4+/-2.3)x10(-4) l/h, respectively.

CONCLUSIONS

This study provides data to demonstrate that nearly one half of OR-1896 is eliminated unchanged into urine and that the active metabolites metabolite of levosimendan remain in the body longer than levosimendan. The remaining half of OR-1896 dose is eliminated through other metabolic routes, partially through interconversion back to OR-1855 with further metabolism of OR-1855. Given the fact that the pharmacological activity and potency of OR-1896 is similar to levosimendan, these results emphasize the clinical significance of OR-1896 and its contribution to the long-lasting effects of levosimendan.

Pharmacokinetics and bioavailability of bemoradan, a long-acting inodilator in healthy males

Bemoradan is a potent, long-acting orally active inodilator. The pharmacokinetics and bioavailability of bemoradan were studied in twelve normal males following oral administration of single, ascending doses of the bemoradan HCL salt in capsules. Plasma and urine levels of bemoradan were determined by HPLC (detection limits: approximately 0.5 ng/ml for plasma and 5 ng/ml for urine). Bemoradan was rapidly absorbed from the capsule formulation at all doses (Cmax occurred at 2.1-2.4 hours). Bemoradan was slowly eliminated from the body (harmonic mean t1/2 16-23 hours). There was a dose-proportional increase in the AUC (0-48) values of bemoradan in humans following the administration of 0.5, 1, 1.5 and 2 mg of bemoradan. The AUC (0-48) values increased to 2.3, 3.4 and 4.0 times when the dose was increased to 2, 3 and 4 times. Urinary excretion of unchanged bemoradan accounted for approximately 5-12% of the dose. Results from this study and previous studies in rats and dogs indicate that bemoradan is well and rapidly absorbed after oral dosing, has linear pharmacokinetics and long elimination half-lives across species.

[Biotransformation of pyridazines. 1. Pyridazine and 3-methylpyridazine]

Pyridazin (1) and 3-methylpyridazine (6) undergo oxidative biotransformation in an unexpected high degree. Beside the unchanged compounds, after administration of 1 two isomeric monohydroxylated products (2, 3), 4,5-dihydrodihydroxypyridazine (4) and 4,5-dihydroxypyridazine (5) and after administration of 6 one ringhydroxylated 6-derivative (7), 3-hydroxymethylpyridazine (8), one ringhydroxylated 3-hydroxymethylpyridazine derivative (9) and 4,5-dihydroxy-3-methylpyridazine (10) were suggested as urinary metabolites in rats. 2 and 7 are the main metabolites of 1 and 6, respectively.

The influence of food on the pharmacokinetics and ACE inhibition of cilazapril

1. The influence of food on the pharmacokinetics and angiotensin-converting enzyme (ACE) inhibitory effects of oral 5 mg doses of cilazapril was investigated in a two-way crossover study in 16 volunteers. 2. Plasma and urine concentrations of cilazaprilat, the active diacid metabolite of cilazapril, and plasma ACE activity were determined by a radio-enzymatic method. 3. Cmax decreased by 30% (P less than 0.05) with a delay in (t)max of 1 h (P less than 0.05) and area under curve (AUC) was decreased by 14% (P less than 0.05). The elimination rate was unaltered. 4. Onset of ACE inhibition was delayed by approximately 30 min but degree and duration were unaffected. 5. The effect of food on the bioavailability of cilazapril at this dose would not be expected to be clinically significant.

Red cell haemolysis induced by SK&F 95018--a combined vasodilator and beta-adrenoceptor antagonist

SK&F 95018, a potential antihypertensive agent with the combined properties of vasodilation and beta-adrenoceptor antagonism, induced red urine when given intravenously to a dog. Further studies revealed that in the dog, SK&F 95018 treatment led to haemoglobinaemia, haemoglobinuria and a fall in the red blood cell count. The compound was therefore suspected of causing red cell haemolysis and this was confirmed using dog blood in an in vitro haemolysis test system. Oral administration of the compound to dogs gave no indication of haemolysis, but the animals lost large portions of their dose through vomiting and the lack of effect is therefore questionable. Rats, which have no vomit reflex, were treated orally and although no direct evidence of haemolysis was obtained (e.g. haemoglobinaemia), the presence of polychromasia suggested some loss of mature red blood cells had occurred. Rat blood was haemolysed in vitro by SK&F 95018. Human red cells were also used in the in vitro haemolysis test system and these, too, were lysed by the compound. The haemolysis was shown to be related to the structure of the compound itself rather than to its pharmacological effects and development of SK&F 95018 as an antihypertensive agent was abandoned. Electron microscopy indicated that SK&F 95018 induced alterations in the red cell membrane which led to shape change, characterized by discocyte to spherocyte transformation, and finally haemolysis. The mechanism of this effect remains under investigation.

High-performance liquid chromatographic determination of cadralazine in human plasma and urine

A sensitive and selective high-performance liquid chromatographic method for determination of intact cadralazine in human plasma or urine has been developed. The sample was buffered (plasma, pH 7.6; urine, pH 12.0) and mixed with internal standard before it was applied to an Extrelut-3 column. After adsorption, the column was eluted with chloroform, and the eluate was extracted with sodium acetate-hydrochloric acid buffer (pH 2.1). A 20-microliters aliquot of the aqueous phase was chromatographed on a 5-microns Spherisorb ODS reversed-phase column, with acetonitrile-phosphate buffer (pH 6.0, 25:75) as eluent. The quantitation was achieved by monitoring the ultraviolet absorbance at 254 nm. The detection limit was 0.03 nmol/ml in plasma and 5.00 nmol/ml in urine. The within-assay variation and the day-to-day reproducibility were less than or equal to 10% for plasma or urine standard samples. No interferences from possible metabolites or endogenous constituents could be noted. The utility of the method was demonstrated by analysing cadralazine in samples from one hypertensive subject on a therapeutic dose of the drug (7.5 mg orally).

Analysis of drugs from biological fluids using disposable solid phase columns

The traditional liquid-liquid extraction method for the removal of drug from biological matrix is being superseded by solid phase extraction. This involves the selection of an appropriate sorbent (normal-phase, reversed-phase, ion-exchange etc.), but once this has been achieved the method is quick and simple to operate. Most sample handling losses are avoided so recovery of drug is high and it is easily automated. Disposable columns have several advantages. Samples of 0.05-2.0 ml can be analysed routinely. Several wash stages can be included in a method to provide a specific extraction prior to a quick analysis by high-performance liquid chromatography (HPLC), radioimmunoassay, UV etc. A potential problem is that retention of the drug may involve more than one mechanism. Elution of drug may therefore require a stronger eluting solvent than analytical HPLC systems using the same stationary phase.

Identification in man of urinary metabolites of a new bronchodilator, MDL 257, using triple stage quadrupole mass spectrometry-mass spectrometry

The structure elucidation of drug metabolites directly from urine by tandem mass spectrometry (MS/MS) for a new bronchodilator is described. When urine samples from human subjects dosed with 400 mg of MDL 257 were examined by MS/MS, three major urinary metabolites previously characterized in animal studies were confirmed and two previously unsuspected metabolites were identified. Using the operational modes of a triple stage quadrupole mass spectrometer, it is possible both to detect and to identify possible metabolites. Since the pure drug and its metabolites often contain common structural daughter ions, the parent spectra of these common daughter ions should contain some or all of the molecular ions of possible metabolites. Daughter spectra of these suspected molecular ions were obtained and the resulting daughter spectra were interpreted for structural information of suspected metabolites. This study confirms the utility of MS/MS to do rapid metabolic profiling and identification directly from complex samples such as urine, with minimal time for sample preparation and analysis. This technique can provide unique and complimentary data when combined with the more classical approaches such as HPLC profiling, isolation, and off-line spectroscopy.

Metabolic oxidation of the pyrrole ring: structure and origin of some urinary metabolites of the anti-hypertensive pyrrolylpyridazinamine, mopidralazine. III: Studies with the 13C-labelled drug

The metabolism of the anti-hypertensive drug, mopidralazine, N-(2',5'-dimethyl-1H-pyrrol-1-yl)-6-(4"-morpholinyl)-3-pyridazinamine, was reinvestigated in rats using the [2'(5')-13CH3]-labelled drug to determine the significance of the pharmacologically active intermediate 3-hydrazino-6-(4-morpholinyl)pyridazine. The previously proposed mesonic structure of the major metabolite I, i.e., 5'-hydroxy-3',6'-dimethyl-1'-[6-(4"-morpholinyl)-3-pyridazinyl]pyrida zinium hydroxide inner salt, was confirmed by chemical synthesis, X-ray diffraction analysis and 1H n.m.r. of the [3',6'-13CH3]-labelled metabolite I. Metabolite II, 3-methyl-6-(4-morpholinyl)-triazolo [4,3-6 b]pyridazine and metabolite VII, 3-methyl-7-(4-morpholinyl)-3H-pyridazino[1,6-c]pyridazine, were shown to retain the 13CH3 labelling of mopidralazine, whereas metabolite X, 3-acetyl-hydrazino-6-(4-morpholinyl)-pyridazine, loses the labelling, indicating that their formation involves two different pathways. It is hypothesized that the oxidation of the pyrrole leads to ring opening followed by a chemical rearrangement giving rise directly to metabolites II and VII or, with the intermediacy of the pharmacologically active 3-hydrazino-6-(4-morpholinyl) derivative and an enzymic acetylation or conjugation with pyruvic acid, to metabolites X, II and VII.

Human pharmacokinetics of cadralazine: a new vasodilator

The pharmacokinetic profiles in plasma and the renal elimination of 2-(3-[6-(2-hydroxypropyl)ethylamino]pyridazinyl)ethylcarbazate+ ++ were investigated in six healthy volunteers following single oral doses of 5, 10 and 20 mg of cadralazine. The study was run in a randomized change-over design experiment. Concentrations of cadralazine in plasma and urine were determined by a high-performance liquid chromatography method. Maximum plasma levels (Cmax) were reached between 0.25 and 1.0 h (tmax) after administration and ranged from 69.8 to 210.0 ng/g after the 5 mg dose, 148.9 to 333.3 ng/g after the 10 mg dose and 292.9 to 474.5 ng/g after the 20 mg dose. The corresponding area under the plasma concentration-time curve (AUC24hO) are 330, 621 and 1168 (ng/g). h. Mean renal elimination of the unchanged-drug ranged from 69 to 73% of the dose. Mean Cmax, AUC24hO and mean total renal elimination were linearly dose-related. An elimination half-life from plasma of about 2.5 h was observed for cadralazine. Estimations for the mean renal and total clearance range from 185 to 216 ml/min and 251 to 295 ml/min, respectively.

Circulating and brain metabolites of minaprine in the baboon

A mixture of 15N-labelled, 14C-labelled and unlabelled minaprine was administered orally to three baboons, and metabolites in blood, urine and brain investigated. Biological samples were extracted with dichloromethane and the radioactive components extracted were analysed by t.l.c. and autoradiography. Compounds identified by comparing their physiochemical properties with those of synthetic standards and by g.l.c.-mass spectrometry were minaprine, 3-[2-(3-oxo)morpholino-ethylamino]-4-methyl-6-phenylpyridazine, 3-amino-4-methyl-6-phenylpyridazine, 3-[2-(aminoethyl)ethylamino]-4-methyl-6-phenylpyridazine, p-hydroxyminaprine and minaprine N-oxide. In addition to the urinary metabolites, two circulating metabolites were detected: metabolite A, 3-[2-(3-oxo)morpholino-ethylamino]-4-methyl-6-phenylpyridazine, and metabolite B (unidentified). All circulating metabolites appeared very early in blood, confirming the rapid and extensive metabolism of the drug. Metabolites A, B and 3 (p-hydroxyminaprine) were the major metabolites present in plasma. The parent drug was not the major circulating form, and was present in a higher concentration in erythrocytes than in plasma. Erythrocytes might act as a reservoir of the drug and could explain the relatively slow blood clearance of minaprine despite its rapid metabolism. The qualitative metabolic profile in brain tissue was similar to that in blood.

Time-dependent elimination of cinoxacin in rats

The effect of the variation of urinary pH on the pharmacokinetics of the acidic antibacterial agent, cinoxacin (pKa 4.60), was examined. Urinary pH of 24-h fasted rats remained at about pH 6 during the daytime, while that of nonfasted rats was high (about pH 7.5) in the morning and gradually decreased to a pH similar to that of the fasted rat in the afternoon. The free fraction of cinoxacin in fasted rat sera in the morning was similar to that in nonfasted rats despite the longer half-life of cinoxacin in fasted rats. In the afternoon the free fraction was slightly different despite similar cinoxacin elimination in fasted and nonfasted rats. These findings seemed to exclude the contribution of protein binding from the causes of increased cinoxacin elimination in nonfasted rats in the morning. Elimination rate constants of cinoxacin obtained with a one-compartment open model correlated well with urinary pH 30 min after injection, suggesting that the urinary pH plays a more important role in cinoxacin elimination. When cinoxacin was orally administered to fasted rats at 11:00, the area under the plasma concentration-time curve was threefold larger than in nonfasted rats. As found with the intravenous administration, this difference may be explained by the prolonged half-life caused by decreased urinary pH after fasting. This study revealed the time-dependent elimination of cinoxacin in nonfasted rats, which is related to physiological change of urinary pH caused by food intake.

High-performance liquid chromatographic separation of cadralazine from its potential metabolites and degradation products. Quantitation of the drug in human plasma and urine

The chromatographic behaviour of cadralazine and its potential metabolites and degradation products with respect to pH, buffer molarity and composition of eluent is described. A selective method with an adequate sensitivity for the determination of the drug in human plasma and urine is also reported. The method includes extraction of biological fluids with chloroform and the analysis of extracts on a reversed-phase column with isocratic elution and detection at 254 nm. The method has been applied to the analysis of plasma and urine of a patient administered a single oral dose of 30 mg of cadralazine.

Determination of cadralazine in human plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic method is described for the determination of cadralazine in human plasma and urine. To 1 g of plasma (pH 7) or urine (adjusted to pH 11), internal standard was added and the samples were extracted with chloroform-ethanol (95:5, v/v). The substances were then back-extracted into acid (pH 2) and 100 microliter of the aqueous phase were injected. Chromatography was performed on a 10-micron LiChrosorb RP-8 column with acetonitrile-phosphate buffer pH 6 (15:85, v/v) as eluent at a flow-rate of 2.7 ml/min. The substances were detected by UV spectrophotometry at 254 nm. Concentrations down to 0.141 nmol/g in plasma or 10.59 nmol/g in urine could be measured with very good precision. This method was applied to samples from two healthy volunteers given a single oral dose of 10 mg or 20 mg of cadralazine .

Multiple inverse isotope dilution assay for cadralazine and four metabolites in biological fluids

An inverse isotope dilution assay was developed for the specific determination of 14C-labelled cadralazine and four of its metabolites in biological samples. After addition of unlabelled carrier substances to the sample, metabolite IV was derivatized. The derivative and the unaltered compounds (I, II, III, V) were extracted and separated by high-performance liquid chromatography on silica gel. Quantitation was performed by on-line ultraviolet detection at 274 nm and off-line radiometry by liquid scintillation counting. Endogenous compounds and unknown metabolites did not interfere in the assay. The analysis of water, plasma and urine samples spiked with [14C]cadralazine showed mean recoveries between 98.4 and 101.3%. The lower limit of detection was 10 nmol/1 (3 ng/ml) for any of the compounds I-V. The method was used for the analysis of plasma and urine samples of rats dosed with [14C]cadralazine.

Quantitative analysis of minaprine and some of its metabolites with application to kinetic studies in rats

A simple and rapid high-performance liquid chromatographic method is described for the quantitative analysis of the psychotropic drug minaprine and three of its metabolites (M1, M3 and M11), including one as yet undetected metabolite (M11) known as a monoamine oxidase type A inhibitor in vitro. After selective extraction all four compounds were separated on a reversed-phase muBondapak C18 column using sodium acetate (0.03 M)-acetonitrile-methanol (88:7:5) (pH 3.3) as the mobile phase. The eluted compounds were detected with a UV detector at 254 nm. The sensitivity of the method is 0.02 microgram per millilitre of body fluid or per gram of tissue for M1 and M11 and 0.05 microgram per minaprine and M3. The method has been applied successfully to the determination of minaprine and the metabolites in plasma and brain and is compared here with an gas-liquid chromatographic method with an electron-capture detector previously developed for the detection of minaprine and M11. M11 was identified in rat urine by gas chromatography-mass spectrometry.

Determination of hydralazine metabolites: 4-hydrazino-phthalazin-1-one and n-acetylhydrazinophthalazin-1-one by gas chromatography and s-triazolo[3,4-alpha]phthalazine and phthalazinone by high-performance liquid chromatography

Methods are described for the determination of 2-N-acetylhydrazinophthalazin-1-one, 4-hydrazinophthalazin-1-one, phthalazinone and s-triazolo[3,4-alpha]phthalazine in human urine. 4-Hydrazinophthalazin-1-one and 4-N-acetylhydrazinophthalazin-1-one (following acid hydrolysis) are reacted with acetylacetone to give a distinctive pyrazole derivative which can be determined by gas chromatography using a nitrogen-specific detector. Phthalazinone and s-triazolo[3,4-alpha]phthalazine are measured underivatised by high-performance liquid chromatography.

Influence of probenecid on serum levels and urinary excretion of cinoxacin

Serum levels and urinary excretion of cinoxacin were examined in healthy individuals after a two-step intravenous infusion in the presence and absence of probenecid. After dosing cinoxacin alone, steady-state serum levels were approached in 1 h and were maintained for an additional 2 h with a reduced infusion rate. After probenecid pretreatment, serum levels of cinoxacin continued to increase during 3 h of infusion, reaching levels approximately double those obtained with cinoxacin alone. The mean elimination half-life of cinoxacin from serum was increased from 1.3 to 3.5 h in the presence of probenecid, and renal clearance was significantly reduced, with 46% of dosed drug appearing in 7-h urines of probenecid-treated subjects compared with 68% in subjects receiving cinoxacin alone. Probenecid had no apparent influence on cinoxacin distribution in the body but caused a significant decrease in the rate of cinoxacin extrarenal elimination, possibly due to competition for a common metabolic pathway.

Metabolites of 3-hydrazino-6-[bis-(2-hydroxyethyl)amino]pyridazine dihydrochloride in rat urine

In 24 hr urine of rats orally given 150 mg/kg of 3-hydrazino-6-[bis-(2-hydroxyethyl)amino]pyridazine dihydrochloride (DL 150), no unchanged compound was detected. Three metabolites, less polar than DL 150, were isolated, their structures assigned by UV, MS, IR and 1H NMR spectroscopies, and confirmed by synthesis. They are: 3-[bis-(2-hydroxyethyl)amino]-6-isopropoxypyridazine (1); 3-[bis-(2-hydroxyethyl)amino]pyridazine (2); 3-methyl-6-[bis-(2-hydroxyethyl)amino]-s-triazolo[4,3-b]pyridazine (3). The metabolism of DL 150 in the rat follows some of the metabolic pathways reported for hydralazine.

Isolation and characterization of 7-hydroxydiftalone beta-glucuronide

Metabolic studies on diftalone (I), a new non-steroidal antiinflammatory agent, demonstated that 7-hydroxydiftalone beta-glucuronide (V) is the main urinary metabolite. The isolation of (V) from the urine of a dog treated with 14C-diftalone was performed by liquid-liquid partition after precolation through Amberlite XAD-2 and IRC-50 (H+). All the steps were followed by radio-detection and by thin layer radio-chromatography. Compound (V) was characterized mainly by mass spectrometry after esterification with diazomethane and silylation with BSA.

Isolation and structure determination of a further metabolite of diftalone

A further metabolite of diftalone, a new antiinflammatory drug, has been identified as 7,14-dihydroxyphthalazino [2,3-b] phthalazine-5,12(7H,14H)-dione, on the basis of physico-chemical properties. The free metabolite was isolated from guinea-pig urine, where it is present as such and as the beta-glucuronide. This structure confirms the selective susceptibility of the methylene group of diftalone towards biological hydroxylation.