Sulfonate Version of OHPAS Linker Has Two Distinct Pathways of Breakdown: Elimination Route Allows Para-Hydroxy-Protected Benzylsulfonate (PHP-BS) to Serve as an Alternative Self-Immolative Group.

Recently we have reported that the ortho-hydroxy-protected aryl sulfate (OHPAS) system can be exploited as a new self-immolative group (SIG) for phenolic payloads. We extended the system to nonphenolic payloads by simply introducing a para-hydroxy benzyl (PHB) spacer. As an additional variation of the system, we explored a benzylsulfonate version of the OHPAS system and found that it has two distinct breakdown pathways, cyclization and 1,4-elimination, the latter of which implies that para-hydroxy-protected (PHP) benzylsulfonate (BS) can also be used as an alternative SIG. The PHP-BS system was found to be stable chemically and in mouse and human plasma, having payload release rates comparable to those of the original OHPAS conjugates.

Pharmacokinetics and tolerability of IDP-73152 mesylate after a single oral administration under fasted and fed conditions in healthy volunteers.

BACKGROUND AND OBJECTIVE: IDP-73152 mesylate is a peptide deformylase inhibitor under investigation for the treatment of complicated skin and respiratory tract infections. The objective of this study was to investigate the pharmacokinetic (PK) profile and tolerability of IDP-73152 and the effect of food after a single oral administration. METHODS: A dose block-randomized, double-blind, placebo-controlled, dose-escalation study was conducted. A total of 56 healthy volunteers received IDP-73152 mesylate in a single oral dose of 40, 80, 160, 320, 640, or 1280 mg in the fasted and fed (640 mg only) states. Blood and urine samples for PK analysis were collected up to 48 h post dose. RESULTS: The area under the plasma concentration-time curve (AUC0-t) of IDP-73152 increased in a dose-proportional manner in the range of 40-320 mg. The mean terminal half-life decreased from 10.7 to 6.2 hrs as the dose increased. The fraction excreted unchanged in the urine ranged from 0.05 to 0.12. In the 640-mg dose group, food delayed the median time to peak concentration (t max) from 0.9 to 3.5 hrs. Furthermore, the maximum plasma concentration (Cmax) were decreased by 36.2%; however, AUC0-t was not generally affected. No serious adverse event or clinically significant findings were observed. CONCLUSIONS: The systemic exposure of IDP-73152 proportionally increased as the dose increased up to 320 mg. The rate of absorption and extent of exposure were reduced by food intake. IDP-73152 was well tolerated without clinically significant adverse effects after a single oral administration.

Application of a novel liquid chromatography/tandem mass spectrometry method for the determination of antazoline in human plasma: Result of ELEPHANT-I [ELEctrophysiological, pharmacokinetic and hemodynamic effects of PHenazolinum (ANTazoline mesylate)] human pharmacokinetic study.

Antazoline is a first-generation antihistaminic agent with antiarrhythmic quinidine-like properties. In some countries, it is widely used for termination of cardiac arrhythmias, especially atrial fibrillation (AF). However, no human pharmacokinetic studies have been conducted with intravenous antazoline. The aim of our study was to develop and validate a novel liquid chromatography/tandem mass spectrometry (LC-MS/MS) method for the determination of antazoline in human plasma: the ELEPHANT-I [ELEctrophysiological, pharmacokinetic and hemodynamic effects of PHenazolinum (ANTazoline mesylate)] human pharmacokinetic study. Antazoline was extracted from plasma using liquid-liquid extraction. The concentration of the analyte was measured by LC-MS/MS with xylometazoline as an internal standard. The method was validated for linearity, precision, accuracy, stability (freeze/thaw stability, stability in autosampler, short and long term stability), dilution integrity and matrix effect. The analyzed validation criteria were fulfilled. The method was applied to a pharmacokinetic study involving 10 healthy volunteers. Following a single intravenous dose of antazoline mesylate (100 mg), the plasma concentration profile showed a relative fast elimination with a terminal elimination half-life of 2.29 h. A relatively high volume of distribution was observed (Vss=315 L). The values of mean residence time (MRT∞), area under the curve (AUC∞) and clearance were 3.45 h, 0.91 mg h L(-1) and 80.5 L h(-1), respectively. One volunteer showed significant differences in pharmacokinetic parameters. In conclusion, the proposed new LC-MS/MS method was successfully used for the first time for the determination of antazoline in human plasma.

Improved oral absorption of cilostazol via sulfonate salt formation with mesylate and besylate.

OBJECTIVE: Cilostazol is a Biopharmaceutical Classification System class II drug with low solubility and high permeability, so its oral absorption is variable and incomplete. The aim of this study was to prepare two sulfonate salts of cilostazol to increase the dissolution and hence the oral bioavailability of cilostazol. METHODS: Cilostazol mesylate and cilostazol besylate were synthesized from cilostazol by acid addition reaction with methane sulfonic acid and benzene sulfonic acid, respectively. The salt preparations were characterized by nuclear magnetic resonance spectroscopy. The water contents, hygroscopicity, stress stability, and photostability of the two cilostazol salts were also determined. The dissolution profiles in various pH conditions and pharmacokinetic studies in rats were compared with those of cilostazol-free base. RESULTS: The two cilostazol salts exhibited good physicochemical properties, such as nonhygroscopicity, stress stability, and photostability, which make it suitable for the preparation of pharmaceutical formulations. Both cilostazol mesylate and cilostazol besylate showed significantly improved dissolution rate and extent of drug release in the pH range 1.2-6.8 compared to the cilostazol-free base. In addition, after oral administration to rats, cilostazol mesylate and cilostazol besylate showed increases in C max and AUC t of approximately 3.65- and 2.87-fold and 3.88- and 2.94-fold, respectively, compared to cilostazol-free base. CONCLUSION: This study showed that two novel salts of cilostazol, such as cilostazol mesylate and cilostazol besylate, could be used to enhance its oral absorption. The findings warrant further preclinical and clinical studies on cilostazol mesylate and cilostazol besylate at doses lower than the usually recommended dosage, so that it can be established as an alternative to the marketed cilostazol tablet.

An Alternative Method for Generating Arynes from ortho-Silylaryl Triflates: Activation by Cesium Carbonate in the Presence of a Crown Ether.

An alternative method for generating arynes from ortho-silylaryl triflates using cesium carbonate and 18-crown-6 is reported. The method was efficiently applied to a variety of reactions between several arynes and arynophiles. We also demonstrated that the efficiency of aryne generation is significantly affected by the alkali metal countercation of the carbonate.

Triketone toxicity: a report on two cases of sulcotrione poisoning.

INTRODUCTION: Sulcotrione is a herbicidal agent belonging to the family of triketones. Sulcotrione herbicides are used for weed control in maize and flax crops. To date, no cases of human poisoning had been reported in the literature linked to different herbicidal agents in the triketone family. We report here on two cases of the voluntary ingestion of this substance in the form of the branded product Mikado(TM), which were recorded by the Angers Poison Centre. CASE REPORT: Both cases of voluntary ingestion constituted attempted suicide, and involved two men aged 30 and 37 years. Their symptoms linked to sulcotrione were limited to vomiting, despite elevated plasma concentrations of sulcotrione. In one case, hypertyrosinemia has been demonstrated. The outcome was favourable in both patients and at follow up, no ocular disorders were observed. In the second case, hypotension and transient renal failure could be linked to the concomitant ingestion of chlorophenoxy herbicides. DISCUSSION: In animal toxicity studies, sulcotrione inhibit 4-hydro-phenylpyruvate dioxygenase leading to hypertyrosinemia and corneal opacities. In both cases, no ocular disorders were observed despite hypertyrosinemia in one case. These case reports were consistent with the animal toxicology findings concerning triketones, and particularly their relative safety in mammals following acute poisoning. However it seems prudent to monitor plasma tyrosine concentrations and to screen prospectively for corneal deposits if further acute intoxication events occur.

Evaluation of drug interactions of GSK1292263 (a GPR119 agonist) with statins: from in vitro data to clinical study design.

1. This work investigated the drug interaction potential of GSK1292263, a novel GPR119 agonist, with the HMG-coA reductase inhibitors simvastatin and rosuvastatin. 2. In vitro experiments assessed the inhibition of transporters and CYP enzymes by GSK1292263, and a clinical drug interaction study investigated the effect of GSK1292263 (300 mg BID) on the pharmacokinetic profile of simvastatin (40 mg single dose) and rosuvastatin (10 mg single dose). 3. In vitro, GSK1292263 demonstrated little/weak inhibition (IC50 values >30 µM) towards CYPs (CYP1A2, 2C9, 2C19, 2D6, 3A4), Pgp, OATP1B3, or OCT2. However, GSK1292263 inhibited BCRP and OATP1B1, which are transporters involved in statin disposition. 4. In the clinical study, small increases in the AUC(0-inf) of simvastatin [mean ratio (90% CI) of 1.34 (1.22, 1.48)] and rosuvastatin [mean ratio (90% CI) of 1.39 (1.30, 1.49)] were observed when co-administered with GSK1292263, which is consistent with an inhibitory effect on intestinal BCRP and CYP3A4. In contrast, GSK1292263 did not inhibit OATP1B1 based on the lack of changes in simvastatin acid exposure [mean AUC(0-inf) ratio (90% CI) of 1.05 (0.91, 1.21)]. 5. GSK1292263 has a weak drug interaction with simvastatin and rosuvastain. This study provides a mechanistic understanding of the in vivo inhibition of transporters and enzymes by GSK1292263.

Pharmacokinetic, distribution, metabolism, and excretion of (Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) in Sprague-Dawley rats.

(Z)-2-amino-1,5-dihydro-1-methyl-5-[4-(mesyl)benzylidene]-4H-imidazol-4-one mesilate (ZLJ-601) is an imidazolone COX/5-LOX inhibitor, which has excellent anti-inflammatory activity with an improved gastrointestinal safety profile. The purpose of this study was to evaluate the in vivo absorption, distribution, metabolism, and excretion of ZLJ-601 in Sprague-Dawley rats. After intravenous or intragastric administration to rats, the concentration of ZLJ-601 in plasma, bile, urine, feces and various types of tissues was detected by LC-MS. We also conducted the identification of metabolites using tandem mass spectrometry. After the intravenous administration, the t(1/2) ranged from 38.71 to 42.62 min and the AUC increased in a dose-proportional manner. After oral dosing, the plasma level of ZLJ-601 peaked at 28.33 min, having a C(max) value of 0.26 mg/l, and the bioavailability was only 4.92%. The highest tissue concentration of ZLJ-601 was observed in lung and kidney, but it was not found in brain. The majority of unchanged ZLJ-601 was excreted in urine (∼35.87%) within 36 h. Two main metabolites are the hydroxylation product and the glucuronide conjugate of the hydroxylation product.

In vitro and in vivo iontophoretic transdermal delivery of an anti-parkinsonian agent.

To objective of this work was to study the feasibility of iontophoretic delivery of SLV 318 (7-(4-benzyl-1-piperazinyl)-2(3H)-benzoxazolone methanesulfonate) across hairless rat skin in vitro and in vivo. The effect of counter-ions and temperature were investigated for optimizing SLV 318 solubility. The effect of electrode efficiency and total current applied on the delivery of SLV 318 were studied using Franz diffusion cells and samples were analyzed using HPLC. Delivery increased with increasing concentration. For current-time combinations, electrode had to be replaced every 9h. Passive, iontophoretic (0.1 mA/cm(2) for 1h) and intravenous studies were performed in vivo. Blood samples collected were analyzed using LC-MS/MS. SLV 318 had higher solubility with NaCl (75 mM) as a counter-ion at 25°C than with other counter-ions tested. In vivo iontophoresis significantly enhanced the permeation and also reduced its lag time (P<0.05). The C(max) of SLV 318 during 1h iontophoresis was 6.56 ± 0.68 ng/mL at 1.31 ± 0.29 h (T(max)) as compared to 2.96 ± 0.29 ng/mL at 25.32 ± 0.67 h (T(max)) by 24h passive permeation. The in vitro and in vivo data has shown the feasibility to enhance delivery of SLV 318 by iontophoresis.

An HPLC-ultraviolet detection method for the determination of Z24 in mouse whole blood and its application to pharmacokinetic studies.

A sensitive and reproducible high-performance liquid chromatography (HPLC)-UV method for the determination of Z24, a tumorigenesis and angiogenesis inhibitor, has been developed and validated in mouse whole blood. Blood samples were extracted with ether, evaporated, and the residue was reconstituted in mobile phase. An aliquot was separated by isocratic reversed-phase HPLC on a Hypersil ODS-2 column and quantified using UV detection at 390 nm. The mobile phase was 50% (v/v) acetonitrile/water with a flow rate of 0.8 ml/min. A linear curve over the concentration range of 0.05-6 microg/ml (r(2)=0.9976) was obtained. The coefficient of the variation for the intra- and inter-day precision ranged from 3.0 to 10.9% and 5.7 to 10.3%, respectively. The absolute recovery of Z24 was 89.2-108.5%. The method is simple, economical and sufficient for in vivo pharmacokinetic studies on Z24. Nonlinear pharmacokinetics was found in mice at doses from 20 to 80 mg/kg.

Stereoselective toxicokinetics and tissue distribution of ethofumesate in rabbits.

The stereoselective toxicokinetics of ethofumesate enantiomers following a single intravenous (i.v.) administration at doses of 30 mg/kg were investigated in rabbits. Plasma concentrations of (+)- and (-)-ethofumesate were analyzed by a validated chiral HPLC method that involved extraction of plasma with organic solvent followed by separation on a cellulose-Tris-(3,5-dimethylphenylcarbamate)-based chiral column and quantification by UV absorbance at 230 nm. Plasma concentration-time curves after i.v. administration were best described by an open two-compartment model. The concentration of the (-)-enantiomer decreased more rapidly than that of the (+)-enantiomer. Significant differences in toxicokinetic parameters between the two enantiomers indicated that stereoselective behavior occurred with the (-)-enantiomer being preferentially metabolized and eliminated.

Study of a novel indolin-2-ketone compound Z24 induced hepatotoxicity by NMR-spectroscopy-based metabonomics of rat urine, blood plasma, and liver extracts.

Antiangiogenic compound has been believed to be an ideal drug in the current cancer biological therapy, but the angiogenesis inhibitors suffer setback for unknown toxicity now. A novel synthetic indolin-s-ketone small molecular compound, 3Z-3-[((1)H-pyrrol-2-yl)-methylidene]-1-(1-piperidinylmethyl)-1,3-2H-indol-2-one (Z24) can inhibit angiogenesis in new blood vessels. The hepatotoxicity effects of Z24 oral administration (dosed at 60, 130 and 200 mg/kg) have been investigated in female Wistar rats by using metabonomic analysis of (1)H NMR spectra of urine, plasma and liver extracts, as well as by clinical chemistry analysis, liver histopathology and electron micrographs examination. The (1)H NMR spectra of the biofluids were analyzed visually and via pattern recognition by using principal component analysis. The metabonomic trajectory analysis on the time-related hepatotoxicity of Z24 was carried out based on the (1)H NMR spectra of urine samples, which were collected daily predose and postdose over an 8-day period. Urinary excretion of citrate, lactate, 2-oxo-glutarate and succinate increased following Z24 dosing. Increased plasma levels of lactate, TMAO and lipid were observed, with concomitant decrease in the level of glucose and phosphatidylcholine. Metabolic profiling on aqueous soluble extracts of liver tissues with the high dose level of Z24 showed an increase in lactate and glutamine, together with a decrease in glucose, glycogen and choline. On the other hand, studies on lipid soluble extracts of liver tissues with the high dose level of Z24 showed increased level in lipid triglycerides and decreased level in unsaturated fatty acids and phosphatidylcholine. Moreover, the most notable effect of Z24 on the metabolism was the reduction in the urinary levels of creatinine and TMAO and the increase in acetate, citrate, succinate and 2-oxo-glutamate with time dependence. The results indicate that in rats Z24 inhibits mitochondrial function through altering the energy and lipid metabolism, which results in the accumulation of free fatty acids and lactate because of the lack of aerobic respiration. These data show that the metabonomic approach represents a promising new technology for the toxicological mechanism study.

Effect of a lipoidic excipient on the absorption profile of compound UK 81252 in dogs after oral administration.

PURPOSE: Effect of caprylocaproyl macrogolglycerides (Labrasol), as a lipoidic excipient/vehicle in an oral capsule formulation, on pharmacokinetic disposition of a BCS Class 3 compound, UK-81252, was investigated in vivo in a canine model. METHODS: The control and lipoidic formulations were administrated to six Beagle dogs in a crossover, single dose design with a 2-week washout period in between treatments. The plasma concentration-time profile for the lipoidic formulation was compared to that of the control formulation (lactose-based oral capsule). RESULTS: Although the lipoidic formulation resulted in a markedly increased oral bioavailability (based on mean pharmacokinetic parameters, AUC(0-48 hr) and C(max) ), a double-peaking phenomenon was observed with this formulation. The most likely cause of this double-peak effect was the gastric emptying retardation attribute of the lipoidic vehicle/excipient. The initial peak (Tmax1) was due to the absorption enhancing properties of the lipoidic formulation and the second peak (Tmax2) was most likely the result of a shutdown in gastric emptying for a period of up to 2 hours (this value varied between dogs) after which the remaining Compound UK 81252 emptied from the stomach to generate the second peak. CONCLUSIONS: Caprylocaproyl macrogolglycerides enhanced the absorption of Compound UK 81252. After oral administration, the liquid-filled formulation consistently produced a double-peak phenomenon in the plasma profile. Labrasol was determined to be the most likely culprit for this double peaking phenomenon.

Simultaneous quantification of seven active metabolites of roxifiban in human plasma by LC/MS/MS in the presence of an interfering displacer at millimolar concentrations.

Roxifiban (DMP 754) is a glycoprotein (GP) IIb/IIIa antagonist. Following oral administration to humans, roxifiban is metabolized to its primary active zwitterionic form, XV459, and several minor, active, hydrolyzed and hydroxylated metabolites, namely, M1a (DPC-AD3508), M1b (DPC-AD6128), M2 (SW156), M3 (DPC-AG2185), M8a (DPC-AF5814), and M8b (DPC-AF5818). Quantification of these metabolites in humans was not workable with a previous analytical method due to ion suppression of at least four of the analytes by a competitive displacer, DMP 728. This compound, which is another GP IIb/IIIa antagonist with very high affinity for the platelet receptor, was added to harvested blood samples in millimolar quantity to liberate XV459 from the GP IIb/IIIa receptor. An automated ion exchange solid phase extraction (IX-SPE) procedure was developed to selectively extract the seven metabolites of roxifiban and its deuterated internal standard while specifically excluding DMP 728. Among the six hydroxylation metabolites, there were two pairs of epimeric diastereomers (M1a/M1b and M8a/M8b) and one pair of geometric isomers (M2/M3), corresponding to three critical chromatographic pairs that needed to be base-line resolved because of the lack of specificity of MS/MS detection for these isomers. A new LC/MS/MS assay was developed to simultaneously quantify the seven metabolites in human plasma. The assay method was validated under GLP conditions over the concentration range of 0.5 to 80 nM for each of the analytes and successfully applied to assaying approximately 500 plasma samples from clinical trials.

Determination of bisnafide, a novel bis-naphthalimide anticancer agent, in human plasma by high-performance liquid chromatography with UV detection.

A simple, specific, and sensitive high-performance liquid chromatographic (HPLC) assay utilizing ultraviolet (UV) detection for the determination of bisnafide in human plasma was developed, validated, and applied to plasma samples from patients undergoing cancer therapy. Plasma samples, containing an internal standard, XE842, were first deproteinized with 2.0 ml acetonitrile, and subsequently, 1.0 ml and pH 9 boric acid-potassium chloride-sodium hydroxide buffer (0.1 M) was added. To this mixture, 9.0 ml of ethyl ether was added then vortex mixed. Following centrifugation, the ether layer was back-extracted into 250 microliters of 0.1 M phosphoric acid, then removed by vacuum aspiration. A portion of the remaining acid layer was directly injected onto the HPLC. Bisnafide was quantified using a Shiseido Capcell Pak C8 HPLC column and ultraviolet detection (274 nm). The lower limit of quantification was 10 ng ml-1 using 1.0 ml plasma. The intraday precision (RSD) ranged from 2.7 to 8.6% over a concentration range of 10-1000 ng ml-1. The interday precision (RSD) ranged from 5.6 to 11.5%. Overall mean accuracy was +/- 5.2%. The drug was stable in frozen heparinized human plasma stored at -20 degrees C for at least 1 year and stable throughout at least two freeze-thaw cycles. This method was successfully utilized for quantifying plasma concentrations needed to study the clinical pharmacokinetics of bisnafide in patients undergoing cancer therapy.

Clinical analysis of sampatrilat, a combined renal endopeptidase and angiotensin-converting enzyme inhibitor I: assay in plasma of human volunteers by atmospheric-pressure ionisation mass-spectrometry following derivatisation with BF3-methanol.

Sampatrilat is a dual inhibitor of angiotensin converting enzyme (ACE) and neutral endopeptidase (NEP) under development for the treatment of hypertension and congestive heart failure. In order to support the early clinical development (with oral administration and an expected low bioavailability), a sensitive and selective assay was required. A method for plasma was developed and validated employing HPLC APCI MS-MS. The plasma samples were extracted on solid-phase extraction cartridges, derivatised with BF3-methanol, diluted, extracted again and then subjected to HPLC APCI-MS-MS. Derivatisation was necessary because the two carboxyl group in the molecule prevented efficient ionisation in the heated nebuliser source. The calibration range was from 0.5 to 20 ng ml(-1) and the lower limit of quantification was 0.5 ng ml(-1). Imprecision and inaccuracy were determined on three separate occasions at three concentrations (0.5, 5 and 20 ng ml[-1]) and shown to be lower than 10% in every case.

Clinical analysis of sampatrilat, a combined renal endopeptidase and angiotensin-converting enzyme inhibitor II: assay in the plasma and urine of human volunteers by dissociation enhanced lanthanide fluorescence immunoassay (DELFIA).

Sampatrilat is a dual inhibitor of angiotensin converting enzyme (ACE) and neutral endopeptidase (NEP) under development for the treatment of hypertension and congestive heart failure. In order to support the early clinical development (with oral administration and an expected low bioavailability), a sensitive and selective assay was required. An HPLC-atmospheric-pressure chemical ionisation mass-spectrometric (HPLC-APCI-MS-MS) assay had been already validated (R.F. Venn et al., J. Pharm. Biomed. Anal., in press), but due to its low throughput an alternative method was sought. As the molecule is peptide-like and not metabolised, we believed the immunoassay approach was appropriate. Thus we developed an immunoassay for the compound using time-resolved fluorescence as an end-point (DELFIA) with lower limits of quantification of 0.2 ng ml(-1) for the plasma assay and 5 ng ml(-1) for the assay in urine. This assay is a 96-well plate based competitive immunoassay; the end-point is the determination of a (non-radioactive) europium label by time-resolved fluorimetry. Sampatrilat is labelled with chelated europium via isothiocyanate chemistry. The advantage of this assay is its extremely high throughput, allowing rapid analysis of many thousands of samples. The DELFIA method was successfully cross-validated with the HPLC-APCI-MS-MS method.

High-performance liquid chromatographic assay of a new HIV-1 protease inhibitor, LB71350, in the plasma of dogs.

A reliable reversed-phase high-performance liquid chromatographic method has been developed for the determination of LB71350 in the plasma of dogs. The analyte was deproteinized with 1.5 volumes of methanol and 0.5 volumes of 10% zinc sulfate, and the supernatant was injected into a 5-microm Capcell Pak C18 column (150x4.6 mm I.D.). The mobile phase was a stepwise gradient mixture of acetonitrile and 0.2% triethylamine-HCl with a flow-rate of 1 ml/min and detection at UV 245 nm. The proportion of acetonitrile was kept at 52% for the first 6 min, increased to 100% for the next 0.5 min, kept at 100% for the next 2 min, decreased to 52% for the next 0.5 min, and finally kept at 52% for the next 7 min. The retention time of LB71350 was 6.9 min. The calibration was linear over the concentration range of 0.1-100 mg/l for dog plasma (r>0.997) and the limit of quantitation was 0.1 mg/l using 0.1 ml plasma. The quality control samples were reproducible with acceptable accuracy and precision at 0.1, 1, 10 and 100 mg/l concentrations. The within-day recovery (n=5) was 90.2-93.9%, the between-day recovery (n=5) was 89.5-93.5%, and the absolute between-day recovery (n=5) was 77-81%. The within-day precision (n=5) and between-day precision (n=5) were 2.59-5.82% and 3.17-4.55%, respectively. No interferences from endogenous substances were observed. Taken together, the above HPLC assay method by deproteinization and UV detection was suitable for the determination of LB71350 in the preclinical pharmacokinetics.

Determination of DMP 728, a IIb/IIIa receptor antagonist, in rat and dog plasma by high-performance liquid chromatography with fluorimetric detection.

A specific and sensitive HPLC assay for the determination of DMP 728 in dog and rat plasma has been developed. The method involves solid-phase extraction of DMP 728 and the internal standard from plasma using a C2 column. The extracted compounds are derivatized with benzoin under alkaline conditions. Using a mixture of acetonitrile and 0.1 M potassium phosphate buffer (25:75, v/v, pH 7.4) as mobile phase, the derivatized products are separated on a Regis semipermeable surface C8 column and monitored fluorometrically using 325 nm and 425 nm as excitation and emission wavelengths, respectively. The assay is linear from 2.5 to 1000 ng/ml in dog plasma and from 5 to 1000 ng/ml in rat plasma. The limit of quantitation is 2.5 ng/ml using 0.5 ml of dog plasma and 5 ng/ml using 0.5 ml of rat plasma. The assay has been used in pharmacokinetic studies of DMP 728 in dogs and rats.

Pre-clinical evaluation of a novel chloroethylating agent, Clomesone.

The in vitro activity of the novel chloroethylating agent, Clomesone, was investigated in a panel of established murine and human tumour cell lines. In vivo anti-tumour activity was examined against three transplantable adenocarcinomas of the mouse colon and in vivo bone marrow toxicity was assessed using a spleen colony forming unit assay. The pharmacokinetic behaviour of the drug in vivo and drug stability in vitro was analysed by gas chromatography with electron capture detection. Clomesone exhibited no activity in vitro against the majority of cell lines derived from solid human colorectal carcinomas. Anti-tumour activity against the murine tumours in vivo was not impressive and was accompanied by myelosuppression. Pharmacokinetic data suggested that the lack of in vivo activity was due to the failure to achieve effective anti-neoplastic drug concentrations at the tumour site. It was concluded that this study found no evidence to suggest that Clomesone was toxicologically more selective than the chloroethylnitrosoureas.