Hermes Licea Perez

Aim: Bioanalytical assays to measure rhamnose, erythritol, lactulose and sucralose in human urine and plasma were developed to support an indomethacin challenge study for intestinal permeability assessment in healthy participants. Methods: The multi-sugar assays utilized 5-mu l sample matrix and a simple chemical derivatization with acetic anhydride, followed by RPLC-MS/MS detection. Results: Rhamnose and erythritol quantification was established between 1.00-1,000 mu g/ml in urine and 250-250,000 ng/ml in plasma. For lactulose and sucralose, dynamic ranges of 0.1-100 mu g/ml (urine) and 25-25,000 ng/ml (plasma) were applied for biological measurements. Conclusion: This work helped overcome some of the common analytical challenges associated with the bioanalysis of mono- and disaccharides and achieved improved limits of quantification.

Background: The instability of aldehydes in biological matrices is associated with their reactions with thiol and amino moieties in proteins. This chemical reaction is reversible by nature and highly pH dependent. Method: A novel approach that includes protein precipitation with an acidic solution of acetonitrile/water/formic acid (85/14/1; v/v/v) was developed to efficiently recover Aldehyde-1 from plasma by shifting the equilibrium toward the formation of the free form. Results: This enabled the support of two GLP studies where Aldehyde-1 was administered to mice. The recovery of Aldehyde-1 from plasma exceeded 88% at three concentration levels. Plasma stability was confirmed at ambient conditions for 24 h and in the freezer for at least 43 (-20 degrees C) and 64 (-70 degrees C) days.

Aim: Quantification of stereoisomers in biological matrices is of pivotal importance for drug development. Supercritical fluid chromatography paired with chiral stationary phases is the gold standa...

Quantitative bioanalytical data are crucial in pharmaceutical research and development, allowing project teams to make informed scientific decisions on the progression of candidate molecules to medicines. Many challenges are often encountered during the bioanalysis of drugs in biological matrices which require resolution in a timely manner. In this publication, guidance is provided to bioanalytical scientists on how to identify potential problems before they become an obstacle for the drug development and to share our experiences dealing some of most common problems encountered in the bioanalytical laboratory. Relevant topics in bioanalysis such as stabilization approaches for glucuronides (Acyl and N-); prodrugs (phosphate and esters), amides, amines, N-oxides; bioanalysis of light sensitive molecules, halogenated drugs and lactones are discussed in this publication.

GSK1795091 (or CRX-601), an aminoalkyl glucosaminide 4-phosphate, is a potent TLR4 agonist in clinical development for the treatment of cancer. Bioanalysis of GSK1795091 is challenging as extremely low doses (−1 or below. Other challenges associated with the bioanalysis of GSK1795091 include carryover and nonspecific binding issues. Due to these compound characteristics and the lack of precedence, extensive method development was performed to address these challenges. A novel extraction protocol was developed that included sample clean up with an Ostro™ pass-through sample preparation plate and a double chemical derivatization approach targeting hydrophilic functional moieties. The method was validated over the concentration range of 2 to 100 pg mL⁻¹ and employed to determine the exposure of GSK1795091 in a first time in human clinical study. Incurred sample reanalysis was also included and the results agreed with those of the original analysis. The method was found to be precise, accurate and robust, and the low LOQ was critical to adequately support clinical PK assessments.

Aim: Bioanalysis of ester prodrugs represents a great analytical challenge due to poor matrix stability in the presence of esterases. Materials & methods: An approach that includes pH control, temperature and the use of an inhibitor (sodium fluoride, NaF) was employed for complete stabilization of an ester prodrug and its corresponding acid metabolite. Stability information was used to design a methodology with negligible ex vivo hydrolysis of the ester to the corresponding acid analyte during all critical parts of bioanalysis. Results & conclusion: The assay was fully validated to regulatory expectations and employed to support a preclinical Good Laboratory Practice study in rats. Incurred sample reanalysis was also conducted and the percent difference between repeat and original results were within ±20%, thus confirming the repeatability of the assay.

Bioanalysis of stereoisomers represents a great challenge, as chromatographic separation is not feasible using conventional reversed or normal-phase chromatography. Supercritical fluid chromatography in combination with chiral stationary phases has proven to be a great tool for chiral resolution, alleviating some of the challenges associated with bioanalysis of stereoisomers. This technical note describes an alternative to the traditional SFC instrument configuration without the use of a back pressure regulator (BPR) and makeup pump; thereby simplifying its usage and improving the robustness and quality of measurements. This alternative configuration has been successfully employed in our laboratory for multiple chiral applications; in particular for the separation of cis/trans geometric stereoisomers. Four case studies are presented – one of which was validated demonstrating the robustness of the technology for bioanalytical applications.

Carbohydrate analysis poses many analytical challenges, in terms of extraction, chromatographic separation, and detection.