Optimization of physicochemical properties of pyrrolidine GPR40 AgoPAMs results in a differentiated profile with improved pharmacokinetics and reduced off-target activities.

GPR40 AgoPAMs are highly effective antidiabetic agents that have a dual mechanism of action, stimulating both glucose-dependent insulin and GLP-1 secretion. The early lipophilic, aromatic pyrrolidine and dihydropyrazole GPR40 AgoPAMs from our laboratory were highly efficacious in lowering plasma glucose levels in rodents but possessed off-target activities and triggered rebound hyperglycemia in rats at high doses. A focus on increasing molecular complexity through saturation and chirality in combination with reducing polarity for the pyrrolidine AgoPAM chemotype resulted in the discovery of compound 46, which shows significantly reduced off-target activities as well as improved aqueous solubility, rapid absorption, and linear PK. In vivo, compound 46 significantly lowers plasma glucose levels in rats during an oral glucose challenge yet does not demonstrate the reactive hyperglycemia effect at high doses that was observed with earlier GPR40 AgoPAMs.

Portable capillary LC for in-line UV monitoring and MS detection: Comparable sensitivity and much lower solvent consumption.

Pharmaceutical development currently relies on quality separation methods from early discovery through to line-of-site manufacturing. There have been significant advancements made regarding the column particle packing, internal diameter, length connectivity, the understanding of the impact key parameters like void volume, flow rate, and temperature all that affects the resultant separation quality, that is, resolution, peak shape, peak width, run time, and signal-to-noise ratio. There is however a strong need to establish better alternatives to large bulky high-performance liquid chromatography racks either for process analytical reaction monitoring or mass spectrometry analysis in establishing product quality. Compact, portable high-pressure liquid chromatography can be a more efficient alternative to traditional ultra-high pressure liquid chromatography and traditional liquid chromatography. The compact versatile instrument evaluated here allows good separation control with either the on-board column with fixed ultra-violet wavelength cartridge or for use with a high-resolution mass spectrometry. Significant space reduction results in greener lab spaces with improved energy efficiency for smaller labs with lower energy demands. In addition, this compact liquid chromatography was used as a portable reaction monitoring solution to compare forced degradation kinetics and assess portable liquid chromatography-mass spectrometry capability for the analyses required for pharmaceutical drug product testing.

Automated ion exchange chromatography screening combined with in silico multifactorial simulation for efficient method development and purification of biopharmaceutical targets.

Bioprocess development of increasingly challenging therapeutics and vaccines requires a commensurate level of analytical innovation to deliver critical assays across functional areas. Chromatography hyphenated to numerous choices of detection has undeniably been the preferred analytical tool in the pharmaceutical industry for decades to analyze and isolate targets (e.g., APIs, intermediates, and byproducts) from multicomponent mixtures. Among many techniques, ion exchange chromatography (IEX) is widely used for the analysis and purification of biopharmaceuticals due to its unique selectivity that delivers distinctive chromatographic profiles compared to other separation modes (e.g., RPLC, HILIC, and SFC) without denaturing protein targets upon isolation process. However, IEX method development is still considered one of the most challenging and laborious approaches due to the many variables involved such as elution mechanism (via salt, pH, or salt-mediated-pH gradients), stationary phase's properties (positively or negatively charged; strong or weak ion exchanger), buffer type and ionic strength as well as pH choices. Herein, we introduce a new framework consisting of a multicolumn IEX screening in conjunction with computer-assisted simulation for efficient method development and purification of biopharmaceuticals. The screening component integrates a total of 12 different columns and 24 mobile phases that are sequentially operated in a straightforward automated fashion for both cation and anion exchange modes (CEX and AEX, respectively). Optimal and robust operating conditions are achieved via computer-assisted simulation using readily available software (ACD Laboratories/LC Simulator), showcasing differences between experimental and simulated retention times of less than 0.5%. In addition, automated fraction collection is also incorporated into this framework, illustrating the practicality and ease of use in the context of separation, analysis, and purification of nucleotides, peptides, and proteins. Finally, we provide examples of the use of this IEX screening as a framework to identify efficient first dimension (1D) conditions that are combined with MS-friendly RPLC conditions in the second dimension (2D) for two-dimensional liquid chromatography experiments enabling purity analysis and identification of pharmaceutical targets.

Assessment of coulometric array electrochemical detection coupled with HPLC-UV for the absolute quantitation of pharmaceuticals.

The use of a coulometric array detector in tandem with HPLC-UV was evaluated for the absolute quantitation of pharmaceutical compounds without standards, an important capability gap in contemporary pharmaceutical research and development. The high-efficiency LC flow-through electrochemical detector system allows for the rapid evaluation of up to 16 different potentials, aiding in the identification and quantitation of electrochemically reactive species. By quantifying the number of electrons added or removed from an analyte during its passage through the detector, the number of moles of the analyte can be established. Herein we demonstrate that molecules containing common electroactive functional groups (e.g. anilines, phenols, parabens and tertiary alkyl amines) can in some cases be reliably quantified in HPLC-EC-UV without the need for authentic standards. Furthermore, the multichannel nature of the CoulArray detector makes it well suited for optimizing the conditions for electrochemical reaction, allowing the impact of changes in potential, flow rate, temperature and pH to be conveniently studied. The electrochemical oxidation of albacivir, zomepirac, diclofenac, rosiglitazone and several other marketed drugs resulted in large linear ranges, predictable recoveries and excellent quantitation using the total moles of electrons and back-calculating using Faraday's law. Importantly, we observed several instances where subtle structural changes within a given class of molecules (e.g. aromatic ring isomers) led to unanticipated changes in electrochemical behavior. Consequently, some care should be taken when applying the technique to the routine quantitation of compound libraries where standards are not available.

Enhanced fluidity liquid chromatography: A guide to scaling up from analytical to preparative separations.

The evolution of supercritical fluid chromatography (SFC) instrumentation, improved detection capability, and expanded modifier range has led to extending the reach of SFC to the analysis of a broader spectrum of analytes beyond enantioselective separations. However, preparative SFC has yet to see the same technological revitalization, especially in regards to the purification of highly polar analytes. Enhanced fluidity liquid chromatography (EFLC) has been demonstrated as one of the ways to extend the applicable range of SFC instrumentation to highly polar analytes such as proteins, carbohydrates, and nucleotides. Despite recent applications of EFLC for challenging mixtures of hydrophilic metabolites and analogs, its viability in preparative purification, which is of great importance to the pharmaceutical industry, remains unknown. Herein, multiple chromatographic parameters that are critical to achieve feasible EFLC purification methods were investigated, including system pressure as a function of modifier composition (for several MeOH:H2O ratios), effect of diluent injection conditions on peak shape, and optimization of mass load with diluent composition. The usage of 50% acetonitrile or methanol diluents provided the most volumetric loading capacity. In the case of sucrose, leveraging higher analyte solubility in water proved to be more favorable than the volumetric loading capacity of diluents with higher organic content. In fact, an 80 mg injection of sucrose was possible on a 2 cm preparative HILIC column with minimal peak shape degradation. The combined information led to the successful demonstration of EFLC for the preparative separation of sugars using readily available MS-directed SFC instrumentation.

Evaluation of global conformational changes in peptides and proteins following purification by supercritical fluid chromatography.

Supercritical fluid chromatography (SFC) has become the fastest growing analytical tool for chiral and achiral small-molecule pharmaceutical separations. The benefits from savings in cost (as a result of lower solvent and energy consumption), and time have made SFC a proven effective tool for solving many analytical problems for small-molecules over the years. There is, however, a gap in the application of SFC for larger biomolecules, proteins and peptides. There has been a notable increase of protein- and peptide-based drug therapies that contain a higher-order structure important to their efficacy. These studies leverage the use of size exclusion chromatography coupled with hydrogen-deuterium exchange (SEC-HDX) methodology and circular dichroism (CD) spectroscopy to probe global conformational structures of model peptides and proteins following purification by preparative SFC. It was demonstrated that bradykinin and insulin can be used in SFC purification, and moreover, insulin was able to recover its original higher-order structure when compared to pre-purification insulin by three orthogonal techniques: 1) calculated percent alpha-helicity based on CD spectra, 2) alpha-helix - temperature hysteresis analysis by CD and 3) SEC-HDX-MS at different temperatures. However, it was shown that the higher order structures of the other three model proteins used in the study (ubiquitin, cytochrome C, and apomyoglobin) were significantly modified during SFC purification and were unable to re-fold to their original conformations. The present workflow was applied successfully to several peptide therapeutic programs at our comp any and in addition can be applied for small proteins.

Discovery of Pyrrolidine-Containing GPR40 Agonists: Stereochemistry Effects a Change in Binding Mode.

A novel series of pyrrolidine-containing GPR40 agonists is described as a potential treatment for type 2 diabetes. The initial pyrrolidine hit was modified by moving the position of the carboxylic acid, a key pharmacophore for GPR40. Addition of a 4-cis-CF3 to the pyrrolidine improves the human GPR40 binding Ki and agonist efficacy. After further optimization, the discovery of a minor enantiomeric impurity with agonist activity led to the finding that enantiomers (R,R)-68 and (S,S)-68 have differential effects on the radioligand used for the binding assay, with (R,R)-68 potentiating the radioligand and (S,S)-68 displacing the radioligand. Compound (R,R)-68 activates both Gq-coupled intracellular Ca2+ flux and Gs-coupled cAMP accumulation. This signaling bias results in a dual mechanism of action for compound (R,R)-68, demonstrating glucose-dependent insulin and GLP-1 secretion in vitro. In vivo, compound (R,R)-68 significantly lowers plasma glucose levels in mice during an oral glucose challenge, encouraging further development of the series.

Supercritical fluid chromatography for GMP analysis in support of pharmaceutical development and manufacturing activities.

Supercritical fluid chromatography (SFC) has long been a preferred method for enantiopurity analysis in support of pharmaceutical discovery and development, but implementation of the technique in regulated GMP laboratories has been somewhat slow, owing to limitations in instrument sensitivity, reproducibility, accuracy and robustness. In recent years, commercialization of next generation analytical SFC instrumentation has addressed previous shortcomings, making the technique better suited for GMP analysis. In this study we investigate the use of modern SFC for enantiopurity analysis of several pharmaceutical intermediates and compare the results with the conventional HPLC approaches historically used for analysis in a GMP setting. The findings clearly illustrate that modern SFC now exhibits improved precision, reproducibility, accuracy and robustness; also providing superior resolution and peak capacity compared to HPLC. Based on these findings, the use of modern chiral SFC is recommended for GMP studies of stereochemistry in pharmaceutical development and manufacturing.

Determination of minor conformational changes of a doxorubicin-peptide conjugate under chromatographic conditions.

Thermodynamic analysis of the reversed-phase retention behavior of a doxorubicin-peptide conjugate demonstrated that the degree of non-linearity observed in Van't Hoff plots was impacted by mobile phase acetonitrile content over the 25-38% acetonitrile (v/v) range tested. Small decreases in the non-polar surface area of the doxorubicin-peptide conjugate as a function of temperature were estimated from these data using linear solvent strength relationships, suggesting that the retention behavior may be the result of minor analyte conformational changes during the chromatographic experiment. This hypothesis was supported via circular dichroism (CD), Raman and 1H NMR spectroscopic studies of the doxorubicin-peptide conjugate in selected chromatographic mobile phase compositions. The CD and Raman data indicated small changes to the apparent analyte microenvironment as a function of temperature and bulk solvent environment, while 1H NMR studies specifically demonstrated the environmental sensitivity of protons on three non-polar peptide residues and the proximal aromatic region of the analyte. Together, these data suggest that minor changes to the conformational order of the essentially random structure of the doxorubicin-peptide conjugate are sufficient to impact chromatographic performance.

Investigations into the chromatographic behavior of a doxorubicin-peptide conjugate.

HPLC impurity profile method development for a doxorubicin-heptapeptide conjugate included significant changes of the separation profile with diluent, eluent and pH. These separation variables were also temperature-dependent with a shift in retention from 35 to 45 degrees C. There was also a direct relationship of temperature with LC retention, and a pH minimum at 5.9. Atypical dependence of the impurity profile on diluent at a k' of 18 led to further investigation. A large change in retention by several minutes was a function of both the organic eluent composition and temperature between 15 and 30 degrees C. Several Van't Hoff temperature studies from 5 to 65 degrees C on several column types resulted in non-linear plots. Analysis of the molecular subunits suggested that the peptide portion of the analyte influenced the non-linear retention behavior. The stationary phase type was not a significant factor causing non-linearity. Circular dichroism-temperature studies indicated a notable transition in ellipticity for the amine regions (198-202 nm) that occurred between 39 and 44 degrees C. This transition temperature range coincided with the results of the Van't Hoff analysis, between 35 and 44 degrees C, to indicate that these effects were not primarily stationary phase induced.

In situ moisture determination of a cytotoxic compound during process optimization.

A simple and safe prototype apparatus was designed and adapted for the in situ determination of the moisture content of a cytotoxic compound (9-fluorenylmethyl-protected doxorubicin-peptide conjugate, or Fm-DPC) by near-infrared absorbance spectroscopy during optimization of the chemical isolation procedure. The cytotoxic nature of the compound restricts one's ability to safely sample such drying processes for more traditional means of moisture determination for fear of hazardous solids dusting, hence in situ sampling approaches are of great importance. These concerns also exist for the process development laboratory, where despite the smaller scale of operations, the volume of experiments (hence cytotoxic samples) required to define a chemical process is often more significant. In this application, partial least squares regression was used with Karl Fischer volumetric titration analysis to generate a calibration model. Although pronounced differences in cake density were observed as a function of the buffer selected for the isolation process, the model still achieved a standard error of calibration of 0.63% w/w and a standard error of prediction of 0.99% (w/w). These results demonstrated the versatility of the prototype apparatus/data processing approach to model Fm-DPC drying under extremely variable conditions, as inherently expected during the investigational laboratory development of a chemical process.