A series of poorly soluble BCS class II compounds with "grease ball" characteristics were assessed for solubility and dissolution rate in biorelevant dissolution media (BDM) with the purpose of investigating which molecular structures gain most in solubility when dissolved under physiologically relevant conditions. The compounds were studied in four media (simulated intestinal fluid in fasted (FaSSIF pH 6.5) and fed state (FeSSIF pH 5.0), and their corresponding blank buffers (FaSSIF(blk) and FeSSIF(blk))) at a temperature of 37 °C. The experimental results were used to analyze which molecular characteristics are of importance for the solubility in BDM and for in silico modeling using multivariate data analysis. It was revealed that a majority of the compounds exhibited a higher dissolution rate and higher solubility in the FaSSIF and FeSSIF than in their corresponding blank buffers. Compounds which were neutral or carried a positive charge were more soluble in FeSSIF than FaSSIF. The acidic compounds displayed clear pH dependency, although the higher concentration of solubilizing agents in FeSSIF than FaSSIF also improved the solubility. Five of the ten compounds were upgraded to BCS class I when dissolved in FaSSIF or FeSSIF, i.e., the maximum dose of these compounds given orally was soluble in 250 mL of these BDMs. Lipophilicity as described by the log D(oct) value was identified as a good predictor of the solubilization ratio (R(2) = 0.74), and computed molecular descriptors were also shown to successfully predict the solubilities in BDM for this data set. To conclude, the physiological solubility of "grease ball" molecules may be largely underestimated in in vitro solubility assays unless BDM is used. Moreover, the results herein indicate that the improvement obtained in BDM may be possible to predict from chemical features alone.

No abstract

No abstract

Purpose To mimic the physicochemical selectivity of the blood-brain barrier (BBB) and to predict its passive permeability using a PAMPA model based on porcine brain lipid extract (PBLE 10%w/v in alkane). Methods Three PAMPA (BD pre-coated and PBLE with 2 different lipid volumes) models were tested with 108 drugs. Abraham solvation descriptors were used to interpret the in vitro-in vivo correlation with 282 in situ brain perfusion measurements, spanning over 5 orders of magnitude. An in combo PAMPA model was developed from combining measured PAMPA permeability with one H-bond descriptor. Results The in combo PAMPA predicted 93% of the variance of 197 largely efflux-inhibited insitu permeability training set. The model was cross-validated by the “leave-many-out” procedure, with q2=0.92±0.03. The PAMPA models indicated the presence of paramembrane water channels. Only the PBLE-based PAMPA-BBB model with sufficient lipid to fill all the internal pore space of the filter showed a wide dynamic range window, selectivity coefficient near 1, and was suitable for predicting BBB permeability. Conclusion BBB permeability can be predicted by in combo PAMPA. Its speed and substantially lower cost, compared to in vivo measurements, make it an attractive first-pass screening method for BBB passive permeability.

No abstract

Values of the ionization constants at 37°C, which are scarcely reported, are more meaningful for interpreting mechanisms of cellular transport by ionizable molecules and in mechanistic dissolution studies, which are often performed at the biorelevant temperature. An equation was developed where the pKa values of drug-like molecules determined at 25°C can be simply converted to values at 37°C, without additional measurement. The differences between the values, ΔpKa = pKa37 − pKa25, were linearly fitted to a function of pKa25 and the standard entropy of ionization, ΔSo, where the latter term was approximated by the five Abraham linear free energy solvation descriptors using multiple linear regression. The Abraham descriptors (H-bond donor and acceptor strengths, dipolar solute-solvent interactions potential, the pi- and n-electrons dispersion force, and molar volume) were determined from the 2-dimensional structure of the molecules. A total of 143 mostly drug-like molecules (207 pKa values at 25°C and at 37°C) were chosen for the study. The pKa values of many were determined here for the first time. Included were 34 weak acids, 85 weak bases, and 24 amphoteric compounds (6 ordinary ampholytes, 18 zwitterions).

The incidence of osteoporosis is high in postmenopausal women due to altered estrogen levels and continuous calcium loss that occurs with aging. Recent studies have shown that microRNAs (miRNAs) are involved in the development of osteoporosis. These miRNAs may be used as potential biomarkers to identify women at a high risk for developing the disease. In this study, whole blood samples were collected from 48 postmenopausal Chinese women with osteopenia or osteoporosis and pooled into six groups according to individual T-scores. A miRNA microarray analysis was performed on pooled blood samples to identify potential miRNA biomarkers for postmenopausal osteoporosis. Five miRNAs (miR-130b-3p, -151a-3p, -151b, -194-5p, and -590-5p) were identified in the microarray analysis. These dysregulated miRNAs were subjected to a pathway analysis investigating whether they were involved in regulating osteoporosis-related pathways. Among them, only miR-194-5p was enriched in multiple osteoporosis-related pathways. Enhanced miR-194-5p expression in women with osteoporosis was confirmed by quantitative reverse transcription–polymerase chain reaction analysis. For external validation, a significant correlation between the expression of miR-194-5p and T-scores was found in an independent patient collection comprised of 24 postmenopausal women with normal bone mineral density, 30 postmenopausal women with osteopenia, and 32 postmenopausal women with osteoporosis (p < 0.05). Taken together, the present findings suggest that miR-194-5p may be a viable miRNA biomarker for postmenopausal osteoporosis.

The permeability characteristics of 33 amphoteric drugs (about 64% zwitterions at physiological pH) were studied using the parallel artificial membrane permeability assay (PAMPA) at pH 6.5. The PAMPA data were modified to include the paracellular permeability component found in cellular monolayers based on a newly generalized version of a popular model devised for Caco-2 cells. These "in combo" PAMPA data were used to predict the human absolute bioavailability of the ampholytes. The analysis produced a good fit, with only five outliers whose transport properties, could be rationalized by (a) nonpassive permeability processes, (b) metabolic instability, and (c) the possible sensitivity to microclimate pH effects in the case of acidic ampholytes. With the exception of two compounds, all of the ampholytes with bioavailability <50% were predominantly transported by the paracellular route, surprisingly with several of the compounds having molecular weights exceeding 350 Da.