Use of the Distribution Coefficient in Brain Polar Lipids for the Assessment of Drug-Induced Phospholipidosis Risk.

In vitro safety assessment in early drug discovery represents an important step to detect potential safety-related liabilities. It reduces late stage attrition and allows candidate optimization. In this study, we report on the use of the LogDBPL assay (a recently published assay for the determination of drug distribution coefficients between an aqueous phase and porcine brain polar lipids extract) for phospholipidosis (PLD) risk evaluation. The LogDBPL parameter was first compared to the effective permeability in the parallel artificial membrane permeability assay (PAMPA), previously reported as correlating with PLD risk. Subsequently, the LogDBPL for a set of 234 drugs with known PLD effect was measured, representing the largest data set of LogDBPL data published so far, and the correlation with phospholipid accumulation was further investigated. In addition, a comparison with other in silico methods based on physicochemical parameters is reported. Results showed that LogDBPL is an efficient descriptor to assess PLD risk, especially when corrected using the pKa value of compounds, being superior to the distribution coefficient in octanol, LogDOCT, and the effective permeability in the PAMPA assay. A multivariate statistical analysis approach was finally used to better define the intrinsic features of LogDBPL, whose effect proved to be highly similar to that of volume of distribution in silico when used to predict brain distribution and PLD.

Hazardous element inertisation in vitrified silicate ceramics: Effect of different matrices.

The ceramic industry is a production sector that can efficiently recycle its own processing residues, achieving a reuse index of almost 100%. Recently, the range of waste from other industrial sectors that can be used as secondary raw materials in ceramic bodies has expanded. However, such an expansion potentially introduces hazardous components. This study aimed to quantitatively assess the efficiency of inertising hazardous elements (HEs) through ceramisation. The ceramics were characterised through XRPD, SEM-EDS and leaching tests to determine their leaching behaviour and the mechanisms of element immobilisation in neoformation phases during the ceramisation process. The results indicate high immobilisation efficiency for Ba, Co, Cr, Cu, Pb, Sb, Sn and Zn. However, Mo is the main element of concern owing to its poor retention in ceramic bodies. This is likely due to the formation of oxyanionic complexes that are difficult to immobilise in silicate matrices. In addition, the ceramic bodies exhibit substantial differences that appear to be associated with variations in pseudo-structural components and the degree of polymerisation of their vitreous phase.

X-ray diffraction microtomography (XRD-CT), a novel tool for non-invasive mapping of phase development in cement materials.

A recently developed synchrotron-based imaging technique, X-ray diffraction microtomography (XRD-CT), has been applied here for the first time to a complex system, the hydrating Portland cement paste, in order to monitor the evolution of microstructure and phase formation with a 3D non-invasive imaging approach. The ettringite-XRD-peak-based image reconstructions, combined with transmission microtomography (X-microCT) images, allowed to assess the ubiquitous distribution of this phase, which appears early in the hydration process and showed its preferential concentration in the relatively less compact regions of the paste. The comparison of greyscale histograms for cement pastes after 9 and 58 h from hydration showed an increase of ettringite content with age, in agreement with the quantitative Rietveld analysis of the sum patterns. By renormalizing the greyscale histograms to the relative weight fraction, as obtained from Rietveld refinements, a new technique which allows estimation of phase contents with spatial resolution has been developed. The results achievable by combining XRD-CT, X-microCT and Rietveld appear very promising to provide experimental snapshots of the cement hydration process to be compared with results obtained from computer simulations.

Ethanol impairs post-prandial hepatic protein metabolism.

The effects of acute ethanol ingestion on whole body and hepatic protein metabolism in humans are not known. To simulate social drinking, we compared the effects of the association of a mixed meal (632 kcal, 17% amino acids, 50% glucose, 33% lipids) with a bottle of either table wine (ethanol content 71 g) or water on the estimates ([1-14C]-leucine infusion) of whole body protein breakdown, oxidation, and synthesis, and on the intravascular fractional secretory rates (FSR) of hepatically (albumin, fibrinogen) and extrahepatically (IgG) synthesized plasma proteins in two randomized groups (ethanol n = 7, water n = 7) of healthy nonalcoholic volunteers. Each study was carried out for 8 h. Protein kinetics were measured in the overnight post-absorptive state, over the first 4 h, and during a meal infusion (via a nasogastric feeding tube at constant rate) combined with the oral ingestion of wine or water, over the last 4 h. When compared with water, wine ingestion during the meal reduced (P < 0.03) by 24% the rate of leucine oxidation, did not modify the estimates of whole body protein breakdown and synthesis, reduced (P < 0.01) by approximately 30% the FSR of albumin and fibrinogen, but did not affect IgG FSR. In conclusion, 70 g of ethanol, an amount usual among social drinkers, impairs hepatic protein metabolism. The habitual consumption of such amounts by reducing the synthesis and/or secretion of hepatic proteins might lead to the progressive development of liver injury and to hypoalbuminemia also in the absence of protein malnutrition.

Effects of different routes of application on ethylenediurea persistence in tobacco leaves.

Ethylenediurea (EDU) is a common research tool for investigating ozone impacts on vegetation, although the role of different application routes (foliar spray vs soil drench) on EDU persistence in the leaves is unknown. We quantified EDU concentrations in leaves of the O3-sensitive Bel-W3 cultivar of tobacco treated with EDU as either foliar spray or soil drench. Foliar EDU concentrations were measured by Q-TOF LC/MS. When EDU was applied as foliar spray, 1 h was enough for reaching a measurable concentration within the leaf. EDU concentration increased over the 21-day period when the leaf was not washed after the application (treatment #1), while it decreased when the leaf was washed after the application (treatment #2). These results suggest that: a) dry deposition of EDU onto the leaf surface was gradually absorbed into the unwashed leaf, although the mechanisms of such uptake were unclear; b) concentration of EDU was decreased quickly (-35%) during the first 24 h from application and more slowly during the following three days (-20%) in the washed leaves. Degradation did not involve enzymatic reactions and was not affected by the presence of ROS. When EDU was applied as soil drench, foliar concentrations increased over time, likely due to adsorption onto soil organic matter and gradual re-solubilization by irrigation water. An analysis of EDU concentration in protoplast and intercellular washing fluid showed that EDU did not enter the cells, but was retained in the apoplast only. Possible implications of EDU in the apoplast and recommendations for EDU application are discussed.

Cyto- and enzyme toxicities of ionic liquids modelled on the basis of VolSurf+ descriptors and their principal properties.

Five in silico principal properties (PPs) for 218 heterocyclic cations and four PPs for 38 organic and inorganic anionic counterparts of ionic liquids (ILs) were derived by the VolSurf+ approach. VolSurf+ physicochemical descriptors take into account several cationic structural features of ILs such as heterocyclic aromatic and non-aromatic cationic cores, alkyl chain length, presence of oxygen atoms in the substituents as well as the properties of a wide variety of inorganic and organic anions. Combination of these cation and anion PPs can provide descriptors for over 8000 ILs, thus allowing the development of QSPR models for IL cytotoxicity (IPC-81 rat cell line) and enzyme toxicity (acetylcholinesterase inhibition). The adoption of a Partial Least Squares approach, relating PPs and toxicities, provided affordable predictions for ILs in both learning and external validation sets, implying the possibility to extend the predictive model to a set of 520 ILs. This allows us to establish priorities in selecting ILs for experimental hazard assessment as required by the REACH regulation.

Sequential tamoxifen and aminoglutethimide versus tamoxifen alone in the adjuvant treatment of postmenopausal breast cancer patients: results of an Italian cooperative study.

PURPOSE: To determine whether switching patients from tamoxifen to antiaromatase treatment would prevent some of the relapses or deaths that we assume would occur if tamoxifen were continued. PATIENTS AND METHODS: Three hundred eighty postmenopausal breast cancer patients receiving adjuvant tamoxifen treatment for 3 years were randomized to either continue tamoxifen for 2 more years or to switch to low-dose aminoglutethimide (250 mg daily) for 2 years. RESULTS: At a median follow-up of 61 months (range, 5 to 94 months), 59 events occurred in the tamoxifen group, and 55 occurred in the aminoglutethimide group. More treatment failures at distant sites, such as viscera (P =.02), were observed in the tamoxifen group. Although no differences in disease-free survival between the two groups have emerged so far, a significant trend favors aminoglutethimide in overall survival (P =.005) and breast cancer-specific survival (P =.06). Even if more patients in the antiaromatase group complained of drug-related side effects and more of them discontinued treatment (P =.0001), the number of cardiovascular events and, in general, of life-threatening adverse events was higher in the tamoxifen arm. CONCLUSION: Switching patients from tamoxifen to aminoglutethimide treatment resulted in comparable event-free survival, but longer overall survival was achieved in patients who were switched to aminoglutethimide as compared with those who continued to receive tamoxifen. Should these preliminary results be confirmed by larger studies with a similar design, which are now testing the effectiveness of the new, more active, and tolerable aromatase inhibitors, sequencing tamoxifen with an aromatase inhibitor could become a preferable alternative to tamoxifen alone in early breast cancer patients.

Bicalutamide monotherapy versus flutamide plus goserelin in prostate cancer patients: results of an Italian Prostate Cancer Project study.

PURPOSE: To compare the efficacy of bicalutamide monotherapy to maximal androgen blockade (MAB) in the treatment of advanced prostatic cancer. PATIENTS AND METHODS: Previously untreated patients with histologically proven stage C or D disease (American Urological Association Staging System) were randomly allocated to receive either bicalutamide or MAB. After disease progression, patients treated with bicalutamide were assigned to castration. The primary end point for this trial was overall survival. Secondary end points included response to treatment, disease progression, treatment safety, quality-of-life (QOL), and sexual function. RESULTS: A total of 108 patients received bicalutamide and 112 received MAB. There was no difference in the percentage of patients whose prostate-specific antigen returned to normal levels. At the time of the present analysis (median follow-up time, 38 months; range, 1 to 60 months), 129 patients progressed and 89 died. There was no difference in the duration of either progression-free survival or overall survival. However, a survival trend favored bicalutamide in stage C disease but MAB in stage D disease. Overall and subgroup trends were confirmed by multivariate analysis. Serious adverse events and treatment discontinuations were more common in patients receiving MAB (P =.08 and P =.04, respectively). Fewer patients in the bicalutamide group complained of loss of libido (P =. 01) and of erectile dysfunction (P =.002). Significant trends favored bicalutamide-treated patients also with respect to their QOL, namely relative to social functioning, vitality, emotional well-being, and physical capacity. CONCLUSION: Bicalutamide monotherapy yielded comparable results relative to standard treatment with MAB, induced fewer side effects, and produced a better QOL.

Cisplatin-gemcitabine combination in advanced non-small-cell lung cancer: a phase II study.

PURPOSE: The nucleoside analog, gemcitabine, has shown activity as a single agent in the treatment of metastatic non-small-cell lung cancer (NSCLC). Its combination with cisplatin in preclinical models suggested synergy between the two drugs. The aim of the study was to evaluate the clinical efficacy and toxicity of the cisplatin-gemcitabine combination in advanced NSCLC. PATIENTS AND METHODS: Forty-eight consecutive previously untreated NSCLC patients entered the trial from January to June 1994. The median age was 60 years (range, 37 to 70) and performance status (PS) was 0 or 1; 22 patients had unresectable stage III disease (21 stage IIIB and one stage IIIA) and 26 had stage IV disease. Gemcitabine 1 g/m2 was administered weekly (days 1, 8, and 15) followed by a 1-week rest and cisplatin 100 mg/m2 on day 2 of each 28-day cycle. Survival and response were determined in accordance with the intention-to-treat principle in all enrolled patients. RESULTS: Of 48 assessable patients, one (stage IV) had a complete response (CR) and 25 achieved a partial response (PR). The overall response rate was 54% (95% confidence interval [CI], 40% to 68%). Thrombocytopenia was the main side effect, with 52% of patients experiencing grade III to IV toxicity, which was usually short-lived and responsible for the omission of gemcitabine administration on day 15 in 50% of chemotherapy courses. The median survival time was 61.5 weeks (95% CI, 40 to 71). CONCLUSION: The combination of gemcitabine and cisplatin induced a high response rate in both stage IIIB and IV NSCLC, with modest side effects. The regimen deserves further careful evaluation in a phase III prospective randomized trial.

Gemcitabine and cisplatin versus mitomycin, ifosfamide, and cisplatin in advanced non-small-cell lung cancer: A randomized phase III study of the Italian Lung Cancer Project.

PURPOSE: To compare gemcitabine and cisplatin (GC) with mitomycin, ifosfamide, and cisplatin (MIC) chemotherapy in patients with stage IIIB (limited to T4 for pleural effusion and N3 for supraclavicular lymph nodes) or stage IV non-small-cell lung cancer (NSCLC). The end points were the evaluation of quality of life (QoL), response rates, survival, and toxicity. PATIENTS AND METHODS: Three hundred seven patients were randomized to receive either gemcitabine 1,000 mg/m(2) on days 1, 8, and 15 plus cisplatin 100 mg/m(2) on day 2, every 28 days, or mitomycin 6 mg/m(2), ifosfamide 3,000 mg/m(2), and mesna on day 1 plus cisplatin 100 mg/m(2) on day 2, every 28 days. The whole-blood cell count was repeated on day 1 in both arms and weekly in the GC arm before each gemcitabine administration. RESULTS: No major differences in changes in QoL were observed between the two treatment arms. The objective response rate was 38% in the GC arm compared with 26% in the MIC arm (P =.029). The median survival time was 8.6 months in the GC arm and 9.6 months in the MIC arm (P =.877, log-rank test). Grade 3 and 4 thrombocytopenia was significantly worse in the GC arm (64% v 28%, P <.001), whereas grade 3 and 4 alopecia was reported more commonly in the MIC arm (39% v 12%, P <. 001). CONCLUSION: We report an increased response rate without changes in QoL and a similar overall survival, time to progression, and time to treatment failure for the GC when compared with the MIC regimen in the treatment of advanced NSCLC.

Physiological increments in plasma insulin concentrations have selective and different effects on synthesis of hepatic proteins in normal humans.

These studies tested the hypothesis that physiological increments in plasma insulin concentrations have selective effects on the synthesis of hepatic proteins in humans. Leucine kinetics and fractional synthetic rates of albumin, fibrinogen, antithrombin III, and apoB-100 were determined in 6 normal subjects, on two different occasions during either the infusion of saline (control study) or a euglycemic-hyperinsulinemic (0.4 mU.kg-1 x min-1 for 240 min) clamp, by a primed-constant infusion of [1-14C]Leu. The insulin infusion significantly decreased the rates of nonoxidative Leu disposal (1.70 +/- 0.10 vs. control 2.06 +/- 0.09 mol.kg-1 x min-1), increased the albumin (7.2 +/- 0.4 vs. 6.2 +/- 0.6%/day), decreased the fibrinogen (18 +/- 1 vs. 23 +/- 2%/day), and antithrombin III (28 +/- 3 vs. 40 +/- 4%/day) fractional synthetic rate, whereas it did not affect the total apoB-100 (49 +/- 5 vs. 52 +/- 6%/day) fractional synthetic rate. Thus, the insulin-induced decrement in the estimates of whole-body protein synthesis (nonoxidative Leu disposal) represents the mean result of opposite effects of hyperinsulinemia on the synthesis of proteins with different functions. The positive effect of insulin on albumin synthesis may play an important anabolic role during nutrient absorption by promoting the capture of a relevant amount of dietary essential amino acids into the protein, whereas the negative effect of insulin on fibrinogen synthesis might, at least partially, account for the increased plasma fibrinogen concentrations previously reported in poorly controlled diabetic patients.

Contribution of amino acids and insulin to protein anabolism during meal absorption.

The contribution of dietary amino acids and endogenous hyperinsulinemia to prandial protein anabolism still has not been established. To this end, leucine estimates ([1-14C]leucine infusion, plasma alpha-ketoisocaproic acid [KIC] specific activity [SA] as precursor pool SA) of whole-body protein kinetics and fractional secretory rates (FSRs) of albumin, fibrinogen, antithrombin III, and immunoglobulin G (IgG) were measured in three groups of healthy volunteers during intragastric infusion of water (controls, n = 5), liquid glucose-lipid-amino acid (AA) meal (meal+AA, n = 7), or isocaloric glucose-lipid meal (meal-AA, n = 7) that induced the same insulin response as the meal+AA. The results of this study demonstrate that 1) by increasing (P < 0.01) whole-body protein synthesis and decreasing (P < 0.01) proteolysis, dietary amino acids account for the largest part (approximately 90%) of postprandial protein anabolism; 2) the ingestion of an isocaloric meal deprived of amino acids exerts a modest protein anabolic effect (10% of postprandial protein anabolism) by decreasing amino acid oxidation and increasing (P < 0.01) albumin synthesis; 3) albumin FSR is increased (approximately 20%) by postprandial hyperinsulinemia (meal-AA) and additionally increased (approximately 50%) by amino acid intake (meal+AA); 4) IgG FSR is stimulated (approximately 40%) by amino acids, not by insulin; and 5) fibrinogen and antithrombin III FSR are not regulated by amino acids or insulin.

Hyperthermia enhances the response of paclitaxel and radiation in a mouse adenocarcinoma.

PURPOSE: The aim of our study was to investigate if the efficacy of paclitaxel and paclitaxel-radiation treatments in vivo could be enhanced by hyperthermia. MATERIALS AND METHODS: Paclitaxel was administered i.p. in doses from 30 to 60 mg/kg b.w. to (C3D2F1) mice bearing spontaneous mammary carcinoma. Local hyperthermia (41 degrees, 42 degrees, 43 degrees C) was carried out by immersing tumor-bearing legs in a water bath for 1 h. Single X-ray treatments from 10 to 90 Gy were performed. Tumor growth delay (TGD) or tumor control dose (TCD(50), radiation dose needed to induce local tumor control in 50% of irradiated animals) were the endpoints. RESULTS: A significant increase of dose-dependent growth delay was observed in paclitaxel and 43 degrees C hyperthermia combined treatments, and a superadditive effect was seen with paclitaxel 45 mg/kg. Combined treatments with hyperthermia at 41 degrees and 42 degrees C were less effective. Administration of paclitaxel 24 h, 4 h, and 15 min before or 15 min and 4 h after hyperthermic treatments produced similar results (TGDs varying from 22.1 to 17 days), and administering paclitaxel 48 h before or 24 h after hyperthermic treatments decreased TGDs (about 10 days). Trimodality treatment (paclitaxel 45 mg/kg, hyperthermia, and X-ray), with a TCD(50) of 14. 1 Gy, in respect to the TCD(50) of 53.1 obtained with X-ray alone, was the most effective. CONCLUSIONS: Hyperthermia enhanced the effectiveness of paclitaxel in all the tested protocols. Our results show a superadditive effect of paclitaxel 45 mg/kg combined with a hyperthermic treatment of 1 h at 43 degrees C. Trimodality treatment, evaluated in terms of percentage of cures, shows a very high enhancement ratio.

Enhancement of radiation response by paclitaxel in mice according to different treatment schedules.

PURPOSE: The aim of our study was to determine if paclitaxel could be used as a radiosensitizer in vivo. MATERIALS AND METHODS: Paclitaxel was tested as a single agent and combined with an X-ray treatment. Paclitaxel was administered i.p. in doses from 30 to 120 mg/kg b.w. to (C3D2F1) mice bearing spontaneous mammary carcinoma. Tumor growth delay (TGD) or tumor control dose (TCD50, radiation dose needed to induce local tumor control in 50% of irradiated animals) and moist desquamation dose (MDD50, radiation dose needed to induce serious moist desquamation in 50% of the non-tumor-bearing feet) were the endpoints. DNA flow cytometric analysis was performed. RESULTS: DNA analysis demonstrated a G2/M block of tumor cells and a depletion of cells in S phase, with a maximum at 24 h from paclitaxel administration. Administering paclitaxel, in graded doses, 15 min before a 10-Gy X-ray treatment resulted in a linear regression line, almost parallel to that with paclitaxel alone, with a growth delay of about 6 days. In contrast, varying the X-ray dose with a constant paclitaxel injection (45 mg/kg b.w.) treatment showed some degree of synergism as the linear regression curves diverged. Interval time and sequence between paclitaxel administration and a 10 Gy X-ray treatment did not influence TGD. Protocols with paclitaxel at 30, 45, or 60 mg/kg were combined with radiation treatments at various doses (from 10 to 65 Gy). Values of TCD50 varied from 50.8 Gy for X-ray alone to 31.8 Gy for paclitaxel 60 mg/kg + X-ray. No differences were observed among MDD of different protocols. CONCLUSIONS: These results suggest that, under some conditions, paclitaxel combined with radiation can show superadditive effects and this result combined with the lack of severe normal tissue damage indicate that a favorable therapeutic gain can be obtained.

A novel strategy for improving ligand selectivity in receptor-based drug design.

A major desirable characteristic of many drugs is their ability to interact specifically with only one variety of the target receptor among many others. It is remarkable that, even when accurate three dimensional structures for the target biomolecules are available, there is no well-established methodology to describe their differences and use them for the design of selectively-interacting compounds. This work presents a novel method that uses multivariate GRID descriptors and principal component analysis (PCA) with the aim of revealing the most relevant structural and physicochemical differences between biomacromolecules related to receptor selectivity. The methodology is described through an example involving the study of bacterial (Escherichia coli) and recombinant human varieties of the dihydrofolate reductase (EC 1.5.1.3, DHFR) enzyme. This analysis easily unveils the most important regions on these biomolecules which should be taken into consideration for the design of selectively interacting compounds.

Comparative molecular field analysis using GRID force-field and GOLPE variable selection methods in a study of inhibitors of glycogen phosphorylase b.

A primary goal in any drug design strategy is to predict the activity of new compounds. Comparative molecular field analysis (CoMFA) has been used in drug design and three-dimensional quantitative structure/activity relationship (3D-QSAR) methods. The CoMFA approach permits analysis of a large number of quantitative descriptors and uses chemometric methods such as partial least squares (PLS) to correlate changes in biological activity with changes in chemical structure. One of the characteristics of the 3D-QSAR method is the large number of variables which are generated in order to describe the nonbonded interaction energies between one or more probes and each drug molecule. Since it is difficult to know a priori which variables affect the biological activity of the compounds, much effort has been devoted to developing methods that optimize the selection of only those variables of importance. This work focuses on some of the aspects involved in the selection of such variables, applied to a series of glucose analogue inhibitors of glycogen phosphorylase b, using the program GRID to describe the molecular structures and using a method of generating optimal partial least squares estimations (program GOLPE) as the chemometric tool. This data set, consisting of over 30 compounds in which the three-dimensional ligand-enzyme bound structures are known, is well suited to study the effect of different data pretreatment procedures on the final model used for the prediction of new drug molecules. By relying on our knowledge of the real physical problem (i.e., using the combined crystallographic and kinetic results), it has been shown that suitable data pretreatment and variable selection have been found that does not result in a significant loss of relevant information. Moreover, by using an appropriate scaling procedure, GOLPE variable selection minimizes the risk of overfitting and overpredicting.

Smart region definition: a new way to improve the predictive ability and interpretability of three-dimensional quantitative structure-activity relationships.

This report describes a new methodology aimed at grouping 3D-QSAR interaction energy descriptors into regions of neighbor variables bearing the same chemical and statistical information. These regions represent the structural variability of the series better than individual descriptor variables and can advantageously replace them in the chemometric analysis. The algorithm used to generate such regions is described, together with their application for improving the quality of GOLPE variable selection. The method is illustrated on a series of 47 glucose analogues, inhibitors of glycogen phosphorylase b, and is shown to improve both the predictive ability and the interpretability of the 3D-QSAR models obtained, comparing favorably with other methods previously described.

A 3D-QSAR study on the structural requirements for binding to CB(1) and CB(2) cannabinoid receptors.

A 3D-QSAR study was carried out on 20 cannabinoids for which the binding affinities (K(i)) with respect to CB(1) and CB(2) receptors, determined in the same cell line, were available. For the first time three series of significantly different chemical structures such as Delta(9)-THC analogues, anandamides, and indoles were included in a single 3D-QSAR model, to obtain information on the interactions of all ligands with both CB(1) and CB(2) receptors and on their receptor selectivity. Delta(9)-THC was chosen as the structural template for alignment. The 3D-structure-activity correlation obtained by the GOLPE procedure provided a partial least squares (PLS) model with a very good predictive ability for the CB(1) receptor affinity of all compounds. The model allowed us to identify seven different regions in the space that contribute to explain the above binding affinities. External validation of the interpretation of the 3D-QSAR model was derived from a response-independent procedure such as principal components analysis (PCA). The CB(2) receptor model evidenced, besides the seven regions found for the CB(1) receptor, a new characteristic region for the CB(2) receptor. Another PCA, using 10 GRID probes, provided further evidence of receptor selectivity regions. One region opposite to the amidic NH of CB(1) selective O585 appears to be responsible for the CB(1) selectivity, while an interaction region opposite to the carbonyl of CB(2) selective JWH-015 appears to be involved in the CB(2) binding selectivity.

A strategy for the incorporation of water molecules present in a ligand binding site into a three-dimensional quantitative structure--activity relationship analysis.

Water present in a ligand binding site of a protein has been recognized to play a major role in ligand-protein interactions. To date, rational drug design techniques do not usually incorporate the effect of these water molecules into the design strategy. This work represents a new strategy for including water molecules into a three-dimensional quantitative structure-activity relationship analysis using a set of glucose analogue inhibitors of glycogen phosphorylase (GP). In this series, the structures of the ligand-enzyme complexes have been solved by X-ray crystallography, and the positions of the ligands and the water molecules at the ligand binding site are known. For the structure-activity analysis, some water molecules adjacent to the ligands were included into an assembly which encompasses both the inhibitor and the water involved in the ligand-enzyme interaction. The mobility of some water molecules at the ligand binding site of GP gives rise to differences in the ligand-water assembly which have been accounted for using a simulation study involving force-field energy calculations. The assembly of ligand plus water was used in a GRID/GOLPE analysis, and the models obtained compare favorably with equivalent models when water was excluded. Both models were analyzed in detail and compared with the crystallographic structures of the ligand-enzyme complexes in order to evaluate their ability to reproduce the experimental observations. The results demonstrate that incorporation of water molecules into the analysis improves the predictive ability of the models and makes them easier to interpret. The information obtained from interpretation of the models is in good agreement with the conclusions derived from the structural analysis of the complexes and offers valuable insights into new characteristics of the ligands which may be exploited for the design of more potent inhibitors.

Predicting blood-brain barrier permeation from three-dimensional molecular structure.

Predicting blood-brain barrier (BBB) permeation remains a challenge in drug design. Since it is impossible to determine experimentally the BBB partitioning of large numbers of preclinical candidates, alternative evaluation methods based on computerized models are desirable. The present study was conducted to demonstrate the value of descriptors derived from 3D molecular fields in estimating the BBB permeation of a large set of compounds and to produce a simple mathematical model suitable for external prediction. The method used (VolSurf) transforms 3D fields into descriptors and correlates them to the experimental permeation by a discriminant partial least squares procedure. The model obtained here correctly predicts more than 90% of the BBB permeation data. By quantifying the favorable and unfavorable contributions of physicochemical and structural properties, it also offers valuable insights for drug design, pharmacological profiling, and screening. The computational procedure is fully automated and quite fast. The method thus appears as a valuable new tool in virtual screening where selection or prioritization of candidates is required from large collections of compounds.