No abstract

This study quantitatively explores the mechanisms underpinning the effects of model pharmaceutical polymeric precipitation inhibitors (PPIs) on the crystal growth and, in turn, maintenance of supersaturation of indomethacin, a model poorly water-soluble drug. A recently developed second-derivative UV spectroscopy method and a first-order empirical crystal growth model were used to determine indomethacin crystal growth rates in the presence of model PPIs. All three model PPIs including HP-β-CD, PVP, and HPMC inhibited indomethacin crystal growth at both high and low degrees of supersaturation (S). The bulk viscosity changes in the presence of model PPIs could not explain their crystal growth inhibitory effects. At 0.05% w/w, PVP (133-fold) and HPMC (28-fold) were better crystal growth inhibitors than HP-β-CD at high S. The inhibitory effect of HP-β-CD on the bulk diffusion-controlled indomethacin crystal growth at high S was successfully modeled using reactive diffusion layer theory, which assumes reversible complexation in the diffusion layer. Although HP-β-CD only modestly inhibited indomethacin crystal growth at either high S (∼15%) or low S (∼2-fold), the crystal growth inhibitory effects of PVP and HPMC were more dramatic, particularly at high S (0.05% w/w). The superior crystal growth inhibitory effects of PVP and HPMC as compared with HP-β-CD at high S were attributed to a change in the indomethacin crystal growth rate-limiting step from bulk diffusion to surface integration. Indomethacin crystal growth inhibitory effects of all three model PPIs at low S were attributed to retardation of the rate of surface integration of indomethacin, a phenomenon that may reflect the adsorption of PPIs onto the growing crystal surface. The quantitative approaches outlined in this study should be useful in future studies to develop tools to predict supersaturation maintenance effects of PPIs.

Weak base therapeutic agents can show reduced absorption or large pharmacokinetic variability when coadministered with pH-modifying agents, or in achlorhydria disease states, due to reduced dissolution rate and/or solubility at high gastric pH. This is often referred to as pH-effect. The goal of this study was to understand why some drugs exhibit a stronger pH-effect than others. To study this, an API-sparing, two-stage, in vitro microdissolution test was developed to generate drug dissolution, supersaturation, and precipitation kinetic data under conditions that mimic the dynamic pH changes in the gastrointestinal tract. In vitro dissolution was assessed for a chemically diverse set of compounds under high pH and low pH, analogous to elevated and normal gastric pH conditions observed in pH-modifier cotreated and untreated subjects, respectively. Represented as a ratio between the conditions, the in vitro pH-effect correlated linearly with clinical pH-effect based on the Cmax ratio and in a non-linear relationship based on AUC ratio. Additionally, several in silico approaches that use the in vitro dissolution data were found to be reasonably predictive of the clinical pH-effect. To explore the hypothesis that physicochemical properties are predictors of clinical pH-effect, statistical correlation analyses were conducted using linear sequential feature selection and partial least-squares regression. Physicochemical parameters did not show statistically significant linear correlations to clinical pH-effect for this data set, which highlights the complexity and poorly understood nature of the interplay between parameters. Finally, a strategy is proposed for implementation early in clinical development, to systematically assess the risk of clinical pH-effect for new molecular entities that integrates physicochemical analysis and in vitro, in vivo and in silico methods.

No abstract

No abstract

ObjectivesChloride intracellular channel protein 4 (Clic4) is a ubiquitously expressed protein involved in multiple cellular processes including cell-cycle control, cell differentiation, and apoptosis. Here, we investigated the role of Clic4 in pancreatic β-cell apoptosis.MethodsWe used βTC-tet cells and islets from β-cell specific Clic4 knockout mice (βClic4KO) and assessed cytokine-induced apoptosis, Bcl2 family protein expression and stability, and identified Clic4-interacting proteins by co-immunoprecipitation and mass spectrometry analysis.ResultsWe show that cytokines increased Clic4 expression in βTC-tet cells and in mouse islets and siRNA-mediated silencing of Clic4 expression in βTC-tet cells or its genetic inactivation in islets β-cells, reduced cytokine-induced apoptosis. This was associated with increased expression of Bcl-2 and increased expression and phosphorylation of Bad. Measurement of Bcl-2 and Bad half-lives in βTC-tet cells showed that Clic4 silencing increased the stability of these proteins. In primary islets β-cells, absence of Clic4 expression increased Bcl-2 and Bcl-xL expression as well as expression and phosphorylation of Bad. Mass-spectrometry analysis of proteins co-immunoprecipitated with Clic4 from βTC-tet cells showed no association of Clic4 with Bcl-2 family proteins. However, Clic4 co-purified with proteins from the proteasome suggesting a possible role for Clic4 in regulating protein degradation.ConclusionsCollectively, our data show that Clic4 is a cytokine-induced gene that sensitizes β-cells to apoptosis by reducing the steady state levels of Bcl-2, Bad and phosphorylated Bad.

Spray-dried dispersions (SDDs) have become an important formulation technology for the pharmaceutical product development of poorly water-soluble (PWS) compounds. Although this technology is now widely used in the industry, especially in the early-phase development, the lack of mechanistic understanding still causes difficulty in selecting excipients and predicting stability of SDD-based drug products. In this review, the authors aim to discuss several principles of polymer science pertaining to the development of SDDs, in terms of selecting polymers and solvents, optimizing drug loading, as well as assessing physical stability on storage and supersaturation maintenance after dissolution, from both thermodynamic and kinetic considerations. In order to choose compatible solvents with both polymers and active pharmaceutical ingredients (APIs), a symmetric Flory-Huggins interaction (Δχ ∼0) approach was introduced. Regarding spray drying of polymer-API solutions, low critical solution temperature (LCST) was discussed for setting the inlet temperature for drying. In addition, after being exposed to moisture, SDDs are practically converted to ternary systems with asymmetric Flory-Huggins interactions, which are thermodynamically not favored. In this case, the kinetics of phase separation plays a significant role during the storage and dissolution of SDD-based drug products. The impact of polymers on the supersaturation maintenance of APIs in dissolution media was also discussed. Moreover, the nature of SDDs, with reference to solid solution and the notion of solid solubility, was examined in the context of pharmaceutical application. Finally, the importance of robust analytical techniques to characterize the SDD-based drug products was emphasized, considering their complexity.

We report a photochemical, hydroxy-directed fluorination that addresses the prevailing challenge of high diastereoselectivity. Numerous motifs showcase a range of regio- and stereochemical outcomes based on the configuration of the hydroxy group.