cΔlog kw IAM: can we afford estimation of small molecules' blood-brain barrier passage based upon in silico phospholipophilicity?

56 compounds, whose log BB values were known from the scientific literature, were considered and their phospholipophilicity values were calculated in silico. These values, along with either experimentally determined or calculated lipophilicity values, were used to extract cΔ/Δ’log k_w^IAM parameters. cΔ/Δ’log k_w^IAM values were found inversely related to data of blood-brain barrier passage, especially in the < -0.20 log BB range and on the IAM.PC.DD2 phase (r² = 0.79). In multiple linear regression, satisfactory statistic models (r² (n-1) = 0.76), based on cΔ/Δ’log k_w^IAM.MG along with other in silico calculated descriptors, were achieved. This method brings the potential to be applied, along with other methodologies, to filter out solutes whose BBB permeation is foreseen to be substandard, thus allowing pharmaceutical companies/research institutes to focus on candidates that are more likely to concentrate in the brain.

Analysis and optimal design of batch and two-column continuous chromatographic frontal processes for monoclonal antibody purification

The increasing demand for efficient and robust processes in the purification of monoclonal antibodies (mAbs) has recently brought frontal chromatography to the forefront. Applied during the polishing step, it enables the removal of high molecular weight aggregates from the target product, achieving high purities. Typically, this process is operated in batch using a single column, which makes it intrinsically subjected to a purity-yield tradeoff. This means that high purities can only be achieved at the cost of lowering the product yield and vice versa. Recently, a two-column continuous implementation of frontal chromatography, referred to as Flow2, was developed. Despite being able of alleviating the purity-yield tradeoff typical of batch operations, the increase in the number of process parameters complicates its optimal design, with the risk of not exploiting its full potential. In this study, we developed an ad hoc design procedure (DP) suitable for the optimization of both batch frontal chromatography and Flow2 in terms of purity, yield, and productivity. This procedure provided similar results as a multiobjective optimization based on genetic algorithm but with lower computational effort. Then, batch and Flow2 operated at their optimal conditions were compared. Besides showing a more favorable Pareto front of yield and productivity at a specified purity, the Flow2 process demonstrated improved robustness compared to the batch process with respect to modifications in the loading linear velocity, washing buffer ionic strength and loading time, thus providing an appealing operation for integrated processes.

Resveratrol and its metabolites bind to PPARs

Resveratrol, a modulator of several signaling proteins, can exert off-target effects involving the peroxisome proliferator-activated receptor (PPAR) transcription factors. However, evidence for the direct interaction between this polyphenol and PPARs is lacking. Here, we addressed the hypothesis that resveratrol and its metabolites control aspects of PPAR transcriptional activity through direct interaction with PPARs. Bioaffinity chromatographic studies with the immobilized ligand-binding domains (LBDs) of PPARγ and PPARα and isothermal titration calorimetry allowed the binding affinities of resveratrol, resveratrol 3-O-glucuronide, resveratrol 4-O-glucuronide, and resveratrol 3-O-sulfate to both PPAR-LBDs to be determined. Interaction of resveratrol, resveratrol 3-O-glucuronide, and resveratrol 4-O-glucuronide with PPARγ-LBD occurred with binding affinities of 1.4, 1.1, and 0.8 μM, respectively, although only resveratrol bound to the PPARα-LBD with a binding affinity of 2.7 μM. Subsequently, X-ray crystallographic studies were carried out to characterize resveratrol binding to the PPARγ-LBD at the molecular level. The electron density map from the crystal structure of the complex between PPARγ-LBD and resveratrol revealed the presence of one molecule of resveratrol bound to the LBD of PPARγ, with the ligand occupying a position close to that of other known PPARγ ligands. Transactivation assays were also performed in HepG2 cells, with the results showing that resveratrol was not a PPAR agonist but instead was able to displace rosiglitazone from PPARγ and Wy-14643 from PPARα with IC50 values of (27.4±1.8) μM and (31.7±2.5) μM, respectively. We propose that resveratrol acts as a PPAR antagonist through its direct interaction with PPARγ and PPARα.

Development and characterization of immobilized cannabinoid receptor (CB1/CB2) open tubular column for on-line screening

Cannabinoid receptors, CB1 and CB2, are therapeutic targets in the treatment of anxiety, obesity, movement disorders, glaucoma, and pain. We have developed an on-line screening method for CB1 and CB2 ligands, where cellular membrane fragments of a chronic myelogenous leukemia cell line, KU-812, were immobilized onto the surface of an open tubular (OT) capillary to create a CB1/CB2-OT column. The binding activities of the immobilized CB1/CB2 receptors were established using frontal affinity chromatographic techniques. This is the first report that confirms the presence of functional CB1 and CB2 receptors on KU-812 cells. The data from this study confirm that the CB1/CB2-OT column can be used to determine the binding affinities (K(i) values) for a single compound and to screen individual compounds or a mixture of multiple compounds. The CB1/CB2-OT column was also used to screen a botanical matrix, Zanthoxylum clava-herculis, where preliminary results suggest the presence of a high-affinity phytocannabinoid.

Synthesis and characterization of liquid chromatographic columns containing the immobilized ligand binding domain of the estrogen related receptor alpha and estrogen related receptor gamma

The ligand binding domains of the estrogen related receptors, ERRalpha and ERRgamma were covalently immobilized onto the surface of an aminopropyl silica liquid chromatography stationary phase to create the ERRalpha-silica and ERRgamma-silica columns and onto the surface of open tubular capillaries to create the ERRalpha-OT and ERRgamma-OT columns. The ERR-silica and ERR-OT columns were characterized using frontal chromatographic techniques with diethylstibesterol and the binding affinities, K(d) values, to the immobilized receptors were consistent with the values obtained by a radioligand binding assay. The ERRgamma-silica column was also characterized using non-linear chromatographic techniques using a series of tamoxifen derivatives. The relative K(d) values obtained for the derivatives were consistent with the relative ability of the compounds to inhibit the cellular proliferation of the human-derived T98G glioma cell line, expressed as IC(50) values. The results indicate that the columns containing immobilized ERRalpha and ERRgamma can be created and used to characterize the binding of compounds to the immobilized receptors and that the relative retention of compounds on these columns reflects the magnitude of their inhibitory activity.