Antitubercular nitrofuran isoxazolines with improved pharmacokinetic properties

Abstract

A series of tetracyclic nitrofuran isoxazoline antituberculosis agents was designed and synthesized to improve the pharmacokinetic properties of an initial lead compound, which had potent antituberculosis activity but suffered from poor solubility, high protein binding and rapid metabolism. In this study, structural modifications were carried on the outer phenyl and piperidine rings to introduce solubilizing and metabolically blocking functional groups. The compounds generated were evaluated for their in vitro antitubercular activity, bacterial spectrum of activity, solubility, permeability, microsomal stability and protein binding. Pharmacokinetic profiles for the most promising candidates were then determined. Compounds with phenyl morpholine and pyridyl morpholine outer rings were found to be the most potent antituberculosis agents in the series. These compounds retained a narrow antibacterial spectrum of activity, with weak anti-gram positive and no gram negative activity, as well as good activity against non-replicating M. tuberculosis in a low oxygen model. Overall, the addition of solubilizing and metabolically blocked outer rings did improve solubility and decrease protein binding as designed. However, the metabolic stability for compounds in this series was generally lower than desired. The best three compounds selected for in vivo pharmacokinetic testing all showed high oral bioavailability, with one notable compound showing a significantly longer half-life and good tolerability supporting its further advancement.

Identification and Characterization of CINPA1 Metabolites Facilitates Structure-Activity Studies of the Constitutive Androstane Receptor

“…Microsomal stability of CINPA1 in HLMs and MLMs was analyzed as described previously (Rakesh et al, 2012). Briefly, a 10 mM CINPA1 stock solution was prepared in DMSO and diluted 1000-fold in 0.5 mg/ml HLMs or MLMs in triplicate wells for six time points.…”

“…The solution was incubated at room temperature for 12-18 hours to allow it to fully stabilize and was then filtered through a 96-well filter plate (pION Inc.). This assay was performed as described previously (Rakesh et al, 2012) on a Biomek FX ADMETox workstation (Beckman Coulter Inc., Fullerton, CA). Fractions were collected from the filtered sample plate and diluted with isopropanol [1:1 (v/v)], and the concentration was determined by UV spectrometry (230-500 nm).…”

“…Caco-2 permeability determinations were performed in the 96-well Transwell system (Corning, NY) using the method of Uchida et al (2009) with modifications as described in Rakesh et al (2012). Caco-2 cells were maintained at 37°C in a humidified incubator with a 5% CO 2 atmosphere.…”

“…Plasma Protein Binding. Mouse and human plasma protein binding of CINPA1 was tested as previously described by Rakesh et al (2012) using the singleuse rapid equilibrium dialysis devices from Thermo Scientific (Rockford, IL). Mouse and human plasma was obtained from Lampire Biologic Laboratories (Pipersville, PA) and centrifuged at 1000 rpm for 2 minutes to remove particulates before use.…”

Lurking in the Dark: Latent Tuberculosis Infection

“…[22,24] Other newer drugs found useful for dormant bacilli are nitromidazopyran, metronidazole and nitrofurans. [25,26] However, isoniazid remains the treatment of choice.…”