Correlation of physicochemical parameters and biological activity in steroids. 9Alpha-substituted corticol derivatives

Quantitative Framework for Bench-to-Bedside Cancer Research

Bioscience is an interdisciplinary venture. Driven by a quantum shift in the volume of high throughput data and in ready availability of data-intensive technologies, mathematical and quantitative approaches have become increasingly common in bioscience. For instance, a recent shift towards a quantitative description of cells and phenotypes, which is supplanting conventional qualitative descriptions, has generated immense promise and opportunities in the field of bench-to-bedside cancer OMICS, chemical biology and pharmacology. Nevertheless, like any burgeoning field, there remains a lack of shared and standardized framework for quantitative cancer research. Here, in the context of cancer, we present a basic framework and guidelines for bench-to-bedside quantitative research and therapy. We outline some of the basic concepts and their parallel use cases for chemical-protein interactions. Along with several recommendations for assay setup and conditions, we also catalog applications of these quantitative techniques in some of the most widespread discovery pipeline and analytical methods in the field. We believe adherence to these guidelines will improve experimental design, reduce variabilities and standardize quantitative datasets.

Quantitative structure-pharmacokinetic/pharmacodynamic relationships of corticosteroids in man

The purpose of this study was to develop quantitative structure-activity/pharmacokinetic relationships (QSAR/QSPKR) for 11 selected corticosteroids in man. Multiple linear regression analysis with an automatic forward step-wise inclusion algorithm was used to construct QSAR/QSPKR models from molecular and submolecular descriptors that were generated using the SYBYL and KowWin computer programs. The final equations describing steroid relative receptor affinity, systemic clearance, volume of distribution, fraction unbound in plasma, and percent of oral absorption, all showed significant correlations (R(2) range 0.841 to 0.977). These relationships were crossvalidated using the leave-one-out method, and appeared to have good predictive performance (Q(2) range 0.715 to 0.912). In addition, a general method for integrating QSAR/QSPKR data to predict the time course of pharmacologic effects is presented. This approach, termed quantitative structure-pharmacodynamic relationships modeling, was successfully applied to predict the rapid cortisol suppressive effects of triamcinolone acetonide after a 2-mg intravenous bolus dose in healthy volunteers.

Glucocorticoids: binding affinity and lipophilicity

The relative binding affinity of 35 steroids for the glucocorticoid receptor was determined in experiments in which the competition of various unlabeled steroids with either [6,7-3H]dexamethasone or [1,2-3H]hydrocortisone for the cytosolic glucocorticoid receptor of cultured human keratinocytes was measured. The data obtained were correlated with steroid lipophilicity, measured as the partition coefficient of the steroid between 1-octanol and pH 7.4 aqueous buffer. The introduction of various substituents on the steroid molecule induced changes in the binding affinity and was associated in some cases with concomitant changes in steroid lipophilicity. The substitution by a 17 alpha-OH or 21-OH group leads in all cases to a decrease in steroid lipophilicity and to an increase in affinity. In contrast, 17 alpha-OAc and especially 21-OAc substitution on hydrocortisone and betamethasone causes a decrease in the steroid affinity for the receptor and an increase in steroid lipophilicity. The elongation of the ester chain from acetate to valerate in both position C-17 and C-21 leads to the increase in both the binding affinity for the receptor and the lipophilicity of steroids. However, all 21-esters showed lower binding affinity than the parent alcohol. The binding affinity of the highly lipophilic 17 alpha, 21-diester was found to be lower than that of the 17 alpha-ester but higher than that of the 21-ester or of the parent alcohol. Only in the series of 17 alpha- and 21-esters is there a correlation between the binding affinity of steroids for the glucocorticoid receptor and their lipophilicity.

Structure and conformation of glucocorticoids

The approaches currently available for determining the structure and conformation of glucocorticoids are reviewed. We discuss the optimization of steroid geometry based on the relative molecular energy calculated by a Westheimer equation. This method permits an extensive description of steroid molecules in a state free of external constraints and which can be assumed to correspond to the minimum internal energy. The structures, conformations, surface areas, and volumes of fifteen steroid molecules that interact with the glucocorticoid receptor have been studied. The basic structure of the A ring is a 1 alpha,2 beta-half-chair, whatever the substitutions. Rings B and C are semi-rigid chairs virtually uninfluenced by substituent groups. In contrast, the shape of the D ring depends on the nature and environment of the substituents. As to the fundamental conformation of the side chain, the steroids fall into two categories, depending on the pressure of a 17-hydroxyl group. For a given molecule, the energy changes associated with conformations of the side chain other than that corresponding to the minimum energy have also been explored. The hypothesis is formulated that receptor binding requires a particular conformation of the side chain. Finally, the overall shape of the molecule can be influenced by the summation of minor but numerous changes brought about by various substitutions, such as 11 beta-hydroxyl, which increases the convexity of the molecule. These investigations should help in elucidating structure-activity relationships for glucocorticoids. They may improve our knowledge of the interaction between these hormones and their receptor and of the molecular mechanism of glucocorticoid action.