Enantiomeric characterization and structure elucidation of Otamixaban.

Otamixaban is a potent (Ki=0.5 nM) fXa inhibitor currently in late-stage clinical development at Sanofi for the management of acute coronary syndrome. Being unproductive in obtaining a suitable crystal of Otamixaban, the required enantiomeric characterization has been accomplished using vibrational circular dichroism (VCD) spectroscopy. Selected by a spectrum similarity index, the calculated spectra of several higher energy conformers were found to match well with the observed spectra. The characteristic IR bands of these conformers were also identified and attributed to the solvation effect. Combined with both the single crystal x-ray diffraction results for an intermediate and the proton NMR study, the absolute configuration of Otamixaban is unambiguously determined to be (R,R).

Applications of ammonium trifluoroacetate as an additive for elution of chiral acids and bases from derivatized polysaccharide stationary phases.

The ability ammonium trifluoroacetate as an additive for elution of acids and bases from derivatized polysaccharide chiral stationary phases was first observed in the process of developing normal-phase chiral HPLC methods in our lead-generation programs. To demonstrate this ability on a broader scale, chiral HPLC methods containing this additive in the mobile phases were developed to resolve selected acidic, basic, and neutral racemates, which are considered standards in the pharmaceutical industry and for which published methods exist. The mobile phases of these published methods contain acidic and/or basic additives (e.g., trifluoroacetic acid or diethylamine). This article demonstrates the versatility of ammonium trifluoroacetate additive in resolving the enantiomers of acidic and basic racemates on the same derivatized polysaccharide chiral columns. This resolution is achieved without changing the mobile phase between the analysis of acidic and basic racemates and also without observation of stationary-phase "memory effect." This chiral method development strategy can result in significant savings of cost and time.

Epimerization study of the L,L- and L,D-diastereoisomers of the calpain inhibitor MDL 28170 by capillary electrophoresis.

MDL 28170, Cbz-(L)-Val-(D,L)-Phe-H, which exists as a mixture of L,L- and L,D-diastereoisomers, is a calpain inhibitor currently investigated as a novel therapeutic agent for the treatment of ischemic stroke and head and spinal trauma. This report describes a capillary electrophoresis (CE) method that uses sodium dodecyl sulfate (SDS) micellar electrokinetic conditions for the separation of the L,L- and L,D-diastereoisomers of MDL 28170. The report also describes the applications of this CE method to the study of epimerization of the L,L- and L,D-diastereoisomers in pH 7.4 phosphate buffered saline solution (PBS), rat and human plasma at 37 degrees C. The relative percent-time courses obtained showed interconversion of the diastereoisomers in all three matrices studied. However, the epimerization process in rat and human plasma was found to be at least 50 times faster than that in PBS. The epimerization half-life of the L,L-diastereoisomer in rat plasma was approximately 30 min, which is about three-fold faster than the observed elimination half-life of the L,L-diastereoisomer reported in a pharmacokinetic study following intravenous bolus dosing.

Evaluation of a method for high throughput solubility determination using a multi-wavelength UV plate reader.

Aqueous solubility is a critical physicochemical property and must be addressed early during drug discovery research. Due to the difficulty in accurately predicting aqueous solubility in silico, high throughput experimental determination of aqueous solubility is in great demand. This study evaluates a method using a multi-wavelength UV plate reader and disposable 96-well UV plates for fast solubility determination. It was demonstrated that this method has the sensitivity and reproducibility to effectively determine solubility as low as 1 micro M. Excellent correlation (R>0.97) was observed between the solubility determined using the UV reader method and the HPLC method over the range of 1-1000 micro M for a diverse set of pharmaceutical compounds. In addition to excellent sensitivity and reproducibility, the UV plate reader method also offers the flexibility of being able to determine thermodynamic solubility in the presence or absence of dimethyl sulfoxide, which is a solvent widely used for combinatorial compounds during high throughput screening.

A comparative study of artificial membrane permeability assay for high throughput profiling of drug absorption potential.

Artificial membrane permeability measurement is a potentially high throughput and low cost alternative for in vitro assessment of drug absorption potential. It will be an ideal screening/profiling tool in the lead generation program of drug discovery research if it is proven to be generally applicable for classifying drug absorption potential and is advantageous over other in vitro or in silico methods. This study provides an in-depth evaluation of the method in close comparison to Caco-2, LogD, LogP, polar surface area (PSA), and quantitative structure-property relationship (QSPR) predictions using a large and diverse compound set. It showed that the accuracy of using artificial membrane permeability in assessing drug absorption is comparable to Caco-2, but significantly better than LogP, LogD, PSA, and QSPR predictions. This study also explored the artificial membrane composition by adopting a hydrophilic filter membrane for artificial membrane (lecithin-dodecane) support. The use of hydrophilic filter membrane increased the rate of permeation significantly and reduced the transport time to 2 h or less as compared with over 10 h when a hydrophobic filter membrane is used.