Use of trifluoroacetic acid to quantify small, polar compounds in rat plasma during discovery-phase pharmacokinetic evaluation.

Although it is accepted that trifluoroacetic acid (TFA) can cause suppression of an analyte during LC/MS analysis, this paper presents a relatively sensitive gradient method that uses a TFA mobile phase for the improved quantification of small, polar drug-like compounds. The described method was developed in a discovery drug metabolism and pharmacokinetics (DMPK) laboratory for the screening measurement of compound concentrations to calculate PK parameters and CNS exposure of compounds from a chemical series that had poor chromatography under generic methods using formic acid mobile phase. The samples were collected by a Culex automated sampling unit, and the plasma proteins were precipitated by a Tecan robot in 96-well plates. After centrifugation, the supernatant was removed, dried down using a SPE-Dry unit, and the samples were reconstituted in aqueous buffer on the robot. The samples were analyzed on an Agilent LC/MSD using a 5-min gradient on a 5 cm phenyl column. No additional steps, such as the "TFA-fix", were necessary. Although sample batches were analyzed over 6h, no drift or degradation of signal was observed. The improved chromatography resulted in a method that was selective, rugged, and had a dynamic range from 5 to 20,000 nM, which was sufficient to quantitate low volume, serial plasma samples collected out to 8 h postdose.

Substituted 3-(phenylmethyl)-1H-indole-5-carboxamides and 1-(phenylmethyl)indole-6-carboxamides as potent, selective, orally active antagonists of the peptidoleukotrienes.

Substituted indole-5-carboxamides and indole-6-carboxamides have been found to be potent and selective antagonists of the peptidoleukotrienes. Initial derivatives of these series (4-[[5-[(cyclopentylmethyl)carbamoyl]-1-methylindol-3-yl] methyl]-3-methoxy-N-[(2-methylphenyl)sulfonyl]benzamide (5a) and 4-[[6-[(cyclopentylmethyl)carbamoyl]-3-methylindol-1-yl] methyl]-3-methoxy-N-[(2-methylphenyl)sulfonyl]benzamide (6a), respectively), when compared to the corresponding indole amides (e.g. 28 and 29), were found to be approximately 10-fold less potent in vitro and substantially less active when administered orally to guinea pigs. Efforts to improve the potency of the title series by variation of the amide, indole, or sulfonamide substituents led to compounds of comparable in vitro potency to ICI 204,219, but of somewhat lower oral activity. A trend which suggested that more lipophilic transposed amides were needed to increase oral activity was exploited with some success and has led to the discovery of 5q (4-[[5-[(2-ethylbutyl)-carbamoyl]-1-ethylindol-3-yl]methyl]- 3- methoxy-N-[(2-methylphenyl)sulfonyl]benzamide), a transposed amide with subnanomolar affinity for the leukotriene receptor and an oral ED50 of 5 mg/kg in a model of asthma in guinea pigs. In this model, ICI 204,219 was active at 0.4 mg/kg. The absolute bioavailability of 5q has been found to be 28% in the rat, as compared to 68% for ICI 204,219, with significant levels of 5q observed in the blood of rats up to 24 h postdose.

N-aryl-3,3,3-trifluoro-2-hydroxy-2-methylpropanamides: KATP potassium channel openers. Modifications on the western region.

A subset of antiandrogen compounds, the N-aryl-3,3,3-trifluoro-2-hydroxy-2-methylpropanamides 1, were found to activate ATP sensitive potassium channels (KATP) and represent a new class of potassium channel openers (PCOs). A structure-activity relationship was carried out on the western region of this series with the goal of obtaining an activator of the ATP sensitive potassium channel suitable for use in the treatment of urge urinary incontinence. In particular three large 4-(N-aryl) substituents, the (N-phenyl-N-methylamino)sulfonyl, benzoyl, and 4-pyridylsulfonyl moieties, yielded non-antiandrogen, KATP potassium channel openers (39, 41, and 64, respectively) that are bladder selective in an in vivo rat model that simultaneously measures bladder contractions, heart rate, and blood pressure. Substitutions of the aryl rings of 41 and 64 gave several derivatives that also display selectivity in the in vivo rat model; however, none appear to offer a substantial advantage over 41 and 64. The PCO activity of 41 and 64 resides in the (S)-(-) enantiomers. ZD6169, 41(S), has been selected into development for the treatment of urge urinary incontinence.