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Kay Ahn,
Sarah E Smith,
Marya B Liimatta,
David Beidler,
Nalini Sadagopan,
David T Dudley,
Tim Young,
Paul Wren,
Yanhua Zhang,
Steven Swaney,
Keri Van Becelaere,
Jacqueline L Blankman,
Daniel K Nomura, Shobha N Bhattachar,
Cory Stiff,
Tyzoon K Nomanbhoy,
Eranthie Weerapana,
Douglas S Johnson,
Benjamin F Cravatt
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ABSTRACT: The endogenous cannabinoid (endocannabinoid) anandamide is principally degraded by the integral membrane enzyme fatty acid amide hydrolase (FAAH). Pharmacological blockade of FAAH has emerged as a potentially attractive strategy for augmenting endocannabinoid signaling and retaining the beneficial effects of cannabinoid receptor activation, while avoiding the undesirable side effects, such as weight gain and impairments in cognition and motor control, observed with direct cannabinoid receptor 1 agonists. Here, we report the detailed mechanistic and pharmacological characterization of N-pyridazin-3-yl-4-(3-{[5-(trifluoromethyl)pyridin-2-yl]oxy}benzylidene)piperidine-1-carboxamide (PF-04457845), a highly efficacious and selective FAAH inhibitor. Mechanistic studies confirm that PF-04457845 is a time-dependent, covalent FAAH inhibitor that carbamylates FAAH's catalytic serine nucleophile. PF-04457845 inhibits human FAAH with high potency (k(inact)/K(i) = 40,300 M(-1)s(-1); IC(50) = 7.2 nM) and is exquisitely selective in vivo as determined by activity-based protein profiling. Oral administration of PF-04457845 produced potent antinociceptive effects in both inflammatory [complete Freund's adjuvant (CFA)] and noninflammatory (monosodium iodoacetate) pain models in rats, with a minimum effective dose of 0.1 mg/kg (CFA model). PF-04457845 displayed a long duration of action as a single oral administration at 1 mg/kg showed in vivo efficacy for 24 h with a concomitant near-complete inhibition of FAAH activity and maximal sustained elevation of anandamide in brain. Significantly, PF-04457845-treated mice at 10 mg/kg elicited no effect in motility, catalepsy, and body temperature. Based on its exceptional selectivity and in vivo efficacy, combined with long duration of action and optimal pharmacokinetic properties, PF-04457845 is a clinical candidate for the treatment of pain and other nervous system disorders.
Journal of Pharmacology and Experimental Therapeutics 07/2011; 338(1):114-24. · 3.83 Impact Factor
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ABSTRACT: This work reports on the solubility of two weakly basic model compounds in media containing sodium lauryl sulfate (SLS). Results clearly show that the presence of SLS in the media (e.g. simulated gastric fluid or dissolution media) can result in an underestimation of solubility of some weak bases. We systematically study this phenomenon and provide evidence (chromatography and pXRD) for the first time that the decrease in solubility is likely due to formation of a less soluble salt/complex between the protonated form of the weak base and lauryl sulfate anion.
International journal of pharmaceutics 06/2011; 412(1-2):95-8. · 2.96 Impact Factor
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ABSTRACT: Dogs are one of the most commonly used non-rodent species in toxicology studies and are known to have basal stomach pH ranging from 2 to 7 in the fasted state. Thus absorption and resulting plasma exposure of weakly basic compounds administered as crystalline suspensions to dogs are often variable. LY2157299 is a potent and selective transforming growth factor (TGF)-beta receptor type 1 kinase (TGF-βRI) inhibitor that displayed variable absorption in early dog studies. This molecule is a weakly basic Biopharmaceutics Classification System (BCS)Class II compound, and depends on the rate and extent of dissolution to drive oral absorption. An artificial stomach and duodenum (ASD) dissolution model was utilized to evaluate potential effect of gastric pH on the absorption of suspension and buffered solution formulations. GastroPlus™ was also employed to predict the magnitude of gastric pH changes on LY2157299 absorption. The ASD experiments demonstrated that administration of a buffered acidic solution could improve the potential for absorption by normalizing gastric pH and enabling supersaturation in the duodenum. GastroPlus™ modeling suggested that direct modulation of gastric pH could lead to marked changes in bioavailability. Pharmacokinetic experiments were conducted in dogs to evaluate the effect of gastric pH modification on plasma exposure. The data were qualitatively consistent with the predictions.
Journal of Pharmaceutical Sciences 06/2011; 100(11):4756-65. · 3.06 Impact Factor
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Douglas S Johnson,
Cory Stiff,
Scott E Lazerwith,
Suzanne R Kesten,
Lorraine K Fay,
Mark Morris,
David Beidler,
Marya B Liimatta,
Sarah E Smith,
David T Dudley,
Nalini Sadagopan, Shobha N Bhattachar,
Stephen J Kesten,
Tyzoon K Nomanbhoy,
Benjamin F Cravatt,
Kay Ahn
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ABSTRACT: Fatty acid amide hydrolase (FAAH) is an integral membrane serine hydrolase that degrades the fatty acid amide family of signaling lipids, including the endocannabinoid anandamide. Genetic or pharmacological inactivation of FAAH leads to analgesic and anti-inflammatory phenotypes in rodents without showing the undesirable side effects observed with direct cannabinoid receptor agonists, indicating that FAAH may represent an attractive therapeutic target for the treatment of inflammatory pain and other nervous system disorders. Herein, we report the discovery and characterization of a highly efficacious and selective FAAH inhibitor PF-04457845 (23). Compound 23 inhibits FAAH by a covalent, irreversible mechanism involving carbamylation of the active-site serine nucleophile of FAAH with high in vitro potency (k(inact)/K(i) and IC(50) values of 40300 M(-1) s(-1) and 7.2 nM, respectively, for human FAAH). Compound 23 has exquisite selectivity for FAAH relative to other members of the serine hydrolase superfamily as demonstrated by competitive activity-based protein profiling. Oral administration of 23 at 0.1 mg/kg results in efficacy comparable to that of naproxen at 10 mg/kg in a rat model of inflammatory pain. Compound 23 is being evaluated in human clinical trials.
ACS Medicinal Chemistry Letters 02/2011; 2(2):91-96. · 3.36 Impact Factor
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ABSTRACT: The design and validation of a novel high-throughput system for thermodynamic solubility determination requiring only 5 mg of sample is described. The system uses a sintered nickel filter assembly to recover excess solids from saturated solutions for rapid crystallinity assessment via powder X-ray diffraction (PXRD). Moreover, the system measures the pH of filtrates to provide a final pH value with the solubility measurement. The limit of detection for the UV-vis plate reader used on this system is approximately 0.001 mg/ml, while the practical upper limit is approximately 3 mg/mL. The solubility measurements of 60 proprietary Pfizer compounds were used to validate the nickel filter assembly against a more conventional polyvinylidenedifluoride (PVDF) filter. Additionally, a comparison was made between a subset of 10 compounds run on the automated system and a more traditional shake-flask method employing HPLC analysis. In both cases, a favorable comparison was obtained.
Journal of Pharmaceutical and Biomedical Analysis 05/2007; 43(5):1660-6. · 2.97 Impact Factor
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ABSTRACT: In drug development, the thermodynamically most stable form of a compound is preferred because metastable forms are prone to transform to the stable form during processing, formulation, or storage [Guillory, J.K., 1999. Generation of polymorphs, hydrates, solvates, and amorphous solids. In: Brittain, H.G. (Ed.), Polymorphism in Pharmaceutical Solids. Marcel Dekker, New York, pp. 183-226]. It is therefore important to discover and characterize the stable form as early as possible. One of the most important properties to determine is thermodynamic solubility. However, due to compound and time constraints this solubility value is usually not determined until late in discovery. This report explores the ability of the pH-metric titration method to measure intrinsic solubility of the stable form of compounds that exist in one or more polymorphic forms. One metastable form and the stable form of eight compounds were examined. Intrinsic solubility was measured via pH-metric titration. The technique was performed on a larger scale in order to monitor polymorphic form changes by powder X-ray diffraction. Shake-flask solubility and corresponding X-ray diffraction data of each form was also determined. The results of this study indicate that, in general, when starting with a metastable polymorph, the pH-metric titration method is able to achieve the solubility of the stable form by the third titration, while the traditional shake-flask solubility method is unable to consistently determine the stable form solubility.
International Journal of Pharmaceutics 03/2007; 330(1-2):105-13. · 3.35 Impact Factor
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ABSTRACT: Solubility data are used to make crucial decisions from the earliest stages of drug discovery throughout the development process, but often the decision-maker is far removed, in terms of both organization and scientific background, from the scientist who generates the data. Here we provide a reference point for consumers of solubility who are presented with increasingly sophisticated strategies to measure sooner, faster or more accurately. We discuss the fundamental forces that govern solubility, the role of physical-chemical parameters such as pH and pK(a), and the principles involved in different solubility measurements. Our ultimate goal is to enable a decision-maker, when presented with solubility data, to have in hand the tools to evaluate not just the magnitude but also the context and appropriateness of those measurements to the drug in question.
Drug Discovery Today 12/2006; 11(21-22):1012-8. · 6.83 Impact Factor
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ABSTRACT: Solubility measurements using chemiluminescent nitrogen detection (CLND) has advantages of reduced compound requirement and increased throughput compared to UV-spectrophotometric and HPLC-based measurements. CLND with direct flow injection was evaluated for the measurement of thermodynamic solubility to support drug discovery. The limit of quantitation (LOQ), accuracy, and day-to-day reproducibility of the detector were measured. Measurements made on CLND were compared to those obtained from UV spectrophotometry and HPLC. Based on the results obtained, it was concluded that the CLND performs satisfactorily for discovery stage thermodynamic solubility measurements.
Journal of Pharmaceutical and Biomedical Analysis 05/2006; 41(1):152-7. · 2.97 Impact Factor
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ABSTRACT: Micronization is a commonly used enabling technology to improve the bioavailability of compounds where absorption is dissolution rate limited. However, decreasing particle size often results in increased Van der Waals' interactions and electrostatic attraction between particles. This causes agglomeration of particles, thereby compromising the increase in surface area gained by micronization. Comicronization with excipients has been reported to offer significant advantages over neat micronization. The present work describes the comicronization of a model compound CI-1040 at a high drug load that shows an increase in the dissolution rate and bioavailability in male Wistar rats. Physicochemical characterization of the comicronized and neat micronized material is presented to help explain the in-vitro and in-vivo data.
Pharmaceutical Development and Technology 02/2005; 10(4):451-60. · 1.36 Impact Factor
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ABSTRACT: The flow properties of pharmaceutical powders and blends used in solid oral dosage forms are an important consideration during dosage form development. The vibratory feeder method, a flow measurement technique that quantifies avalanche flow, has been adapted for measurement of the flow properties of common pharmaceutical powders used in solid oral dosage forms. The flow properties of 17 different powders were measured with the instrument, and the results are reported as a powder flow index (PFI). The PFI trends of the powders correlate well with flow properties reported in the literature. The flow properties of the powders were also measured with a commercially available avalanche instrument, the Aero-Flow, and the results were reported as the mean time to avalanche (MTA). Since the two instruments analyze the avalanche by different algorithms, the results were compared with nonparametric statistical evaluation of ranked data, and they were found to be in excellent agreement. A recommended procedure for measurement of powder flow with the vibratory feeder is presented.
International Journal of Pharmaceutics 02/2004; 269(2):385-92. · 3.35 Impact Factor
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ABSTRACT: Dissolution of Pfizer Compound PD198306, a poorly soluble compound, was studied in 25 mM pH 9 sodium phosphate solution with 0.5% SLS using the flow-through cell dissolution apparatus. Unmicronized and micronized drug powders were tested. Several methods of loading the drug powder into the flow-through dissolution cells and their impact on dissolution were investigated. The influence of flow rate of the dissolution medium on the rate and extent of dissolution were studied. PD198306 has poor wettability even in the presence of 0.5% SLS. It was found that loading the drug powder into the dissolution cell in the form of a suspension provided the best dissolution profile in terms of the rate and extent of dissolution. The flow rate of 4 ml/min resulted in good particle size discrimination.
International Journal of Pharmaceutics 05/2002; 236(1-2):135-43. · 3.35 Impact Factor
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ABSTRACT: Hydrogenated phospholipid (HPL) has been found to form complexes with three non-steroidal ntiinflammatory drugs: salicylic acid, diclofenac and indomethacin. The solubility of the salicylic acid complex in squalane was less than that of the plain drug, but the solubilities of the diclofenac and indomethacin complex increased upon complexation. The permeability coefficients of salicylic acid and diclofenac across shed snake skin are not affected significantly by the presence of hydrogenated phospholipid. However, the permeability coefficient for the indomethacin-HPL complex is about double that for either plain indomethacin or an indomethacin-HPL physical mixture.
International Journal of Pharmaceutics.
