Jeffrey A. Peterson

Synthesis, Crystallization, and Biological Evaluation of an Orally Active Prodrug of Gemcitabine

The design, synthesis, and biological characterization of an orally active prodrug (3) of gemcitabine are described. Additionally, the identification of a novel co-crystal solid form of the compound is presented. Valproate amide 3 is orally bioavailable and releases gemcitabine into the systemic circulation after passing through the intestinal mucosa. The compound has entered clinical trials and is being evaluated as a potential new anticancer agent.

Novel Method for the Determination of Piperazine in Pharmaceutical Drug Substances Using Hydrophilic Interaction Chromatography and Evaporative Light Scattering Detection

Abstract A novel method for the determination of piperazine in pharmaceutical drug substances was developed using high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD). This method uses the hydrophilic interaction chromatography (HILIC) mode on a cyanopropyl (CN) bonded stationary phase. Optimization of organic modifier and acid composition in the mobile phase resulted in robust chromatography conditions with excellent resolution, peak shape, and retention time for the piperazine peak. The method was further evaluated with respect to linearity, precision, selectivity, limit of detection (LOD), and reproducibility. Based on the data provided, this HPLC–ELSD method demonstrated acceptable levels of linearity, precision, LOD, and selectivity for determination of piperazine.

Cyclopropanecarboxylic Acid Esters as Potential Prodrugs with Enhanced Hydrolytic Stability

Esters of cyclopropanecarboxylic acid demonstrate a substantial increase in stability under both acid- and base-catalyzed hydrolytic conditions. Comparison of the stability of valacyclovir 13 with the cyclopropane analogue 14 shows that at 40 degrees C and pH 6 the half-life of 14 is >300 h while the value for 13 is 69.7 h. CBS-QB3 calculations on isodesmic reactions for transfer of groups from an alkane to an ester show that a cyclopropyl group provides hyperconjugative stabilization.

Simultaneous Resolution and Detection of a Drug Substance, Impurities, and Counter Ion Using A Mixed-Mode HPLC Column with Evaporative Light Scattering Detection

Abstract An alternative approach to developing individual potency, impurity, and counter ion methods is the simultaneous resolution and detection of the drug substance, impurities, and the counter ion in a single chromatogram. LY326315 hydrochloride was used as a model compound to demonstrate this concept. The separation was achieved using a conventional HPLC system with an Alltech mixed-mode column, a reversed phase eluant, and evaporative light scattering detection (ELSD). The mixed-mode column, which has both reversed phase and ion chromatography functionalities (e.g. phenyl/cation, C8/anion), coupled with ELSD offers a novel approach to simultaneously resolving and detecting pharmaceutical compounds and counter ions in a single chromatogram.

AMINO ACID ANALYSIS OF PEPTIDES USING HPLC WITH EVAPORATIVE LIGHT SCATTERING DETECTION

A new procedure for the amino acid analysis of peptides has been devised utilizing high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD). This procedure eliminates the need for complex derivatization schemes inherent of previous amino acid analysis procedures since the ELSD detects the amino acids directly. This quantitative method detects and separates 18 of the common amino acids in a one hour run time using cation exchange chromatography coupled with ELSD. The procedure was tested by analyzing the hydrolysate of human parathyroid hormone 1–34 (PTH), a synthetic polypeptide. A standard digestion consisting of 24 hour hydrolysis at 110°C in 6 N hydrochloric acid with 3% phenol was used. Validation data reveal this is an accurate and precise procedure for the amino acid analysis of peptides. The sensitivity of this technique is low compared to other state-of-the-art analytical techniques. Detection limits varied depending on the amino acid being analyzed and were...

Validation of an HPLC Method for the Determination of Sodium in LY293111 Sodium, a Novel LTB4 Receptor Antagonist, Using Evaporative Light Scattering Detection

Abstract Analysis of inorganic ions such as sodium or chloride in pharmaceutical compounds has traditionally employed ion-chromatography (IC) with conductivity detection. A new quantitative method for the determination of sodium in LY293111 sodium, a novel LTB4 receptor antagonist, using high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD) is discussed. The separation of sodium from other ions and interferences was achieved using a Zorbax 300 SCX cation-exchange column suitable for use with organic solvents. Acceptable levels of precision, linearity, recovery, selectivity and limit of detection were achieved during the validation of the method. The results of this method were within 99.8% agreement when compared to the theoretical amount of sodium in LY293111 sodium. HPLC coupled with evaporative light scattering detection offers a practical alternative to IC using conductivity detection in pharmaceutical compounds.

A High-Performance Liquid Chromatography Method for the Quantitation of Impurities in an NMDA Antagonist Using Evaporative Light Scattering Detection

Abstract A reversed-phase high-performance liquid chromatography (HPLC) method utilizing an evaporative light scattering detector (ELSD) was developed for a new NMDA (N-methyl-D-aspartate) antagonist. This method permits quantitation of both the bulk drug substance purity and the related materials possible within the bulk drug substance. The method is compatible with LC/MS and the mass spectral data were obtained for each component in the bulk drug substance.

ENANTIOMERIC SEPARATION OF AN AMPA ANTAGONIST USING A CHIROBIOTIC T™ COLUMN WITH HPLC AND EVAPORATIVE LIGHT-SCATTERING DETECTION

A Chirobiotic T™ column was used for the direct separation of AMPA receptor antagonist LY293558 and the undesired enantiomer LY293559 in bulk drug substance. High performance liquid chromatography (HPLC) separation of the enantiomers was optimized using reversed phase and hydrophilic interaction chromatography (HILIC) by varying the organic composition of the mobile phase. Baseline resolution was achieved allowing accurate, trace level quantitation of the undesired enantiomer in the optically pure bulk material. Because the analytes lack a sufficient ultraviolet chromophore, an evaporative light-scattering detector (ELSD) was used to enhance detection. The ELSD was capable of obtaining detection limits as low as 0.1% of the undesired enantiomer. Additional experiments were conducted to assess the linearity, precision, and accuracy of the HPLC-ELSD system.