A novel scoring function to estimate protein-ligand binding affinities has been developed and implemented as the Glide 4.0 XP scoring function and docking protocol. In addition to unique water desolvation energy terms, protein-ligand structural motifs leading to enhanced binding affinity are included: (1) hydrophobic enclosure where groups of lipophilic ligand atoms are enclosed on opposite faces by lipophilic protein atoms, (2) neutral-neutral single or correlated hydrogen bonds in a hydrophobically enclosed environment, and (3) five categories of charged-charged hydrogen bonds. The XP scoring function and docking protocol have been developed to reproduce experimental binding affinities for a set of 198 complexes (RMSDs of 2.26 and 1.73 kcal/mol over all and well-docked ligands, respectively) and to yield quality enrichments for a set of fifteen screens of pharmaceutical importance. Enrichment results demonstrate the importance of the novel XP molecular recognition and water scoring in separating active and inactive ligands and avoiding false positives.

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Extra Precision Glide: Docking and Scoring Incorporating a Model of Hydrophobic Enclosure for Protein-Ligand Complexes

Forty years ago, Lerner and coworkers (1958) discovered the first nonsteroidal antiestrogen and Jensen (Jensen and Jacobson, 1960) identified a target for drug action, the ER. This knowledge opened the door for the clinical development of tamoxifen which we now know provides a survival advantage in both node-positive and node-negative patients with ER-positive disease (Early Breast Cancer Trialists Collaborative Group, 1992, 1998). The drug has been studied extensively, and the results have provided an invaluable insight into possible ancillary advantages of "antiestrogens", i.e., maintenance of bone density and the prevention of coronary heart disease, and possible disadvantages, i.e., rat liver carcinogenesis and an increased risk of endometrial cancer. Most importantly, the identification of the target site-specific actions of tamoxifen caused a paradigm shift in the prospective uses of antiestrogens from a direct exploitation of the antitumor properties to the broader application as a preventative for osteoporosis, but with the beneficial side effects of preventing breast and endometrial cancer. Raloxifene, a second-generation SERM, has all the properties in the laboratory that would encourage development as a safe preventative for osteoporosis (Jordan et al., 1997). As a result, raloxifene has been evaluated in more than 11,000 postmenopausal women and found to maintain bone density with significant decreases in breast cancer incidence and no increase in endometrial thickness. Raloxifene is now available as a preventative for osteoporosis in postmenopausal women. There is every reason to believe that a multifaceted agent like raloxifene will find widespread use, and there will be continuing interest by the pharmaceutical industry in the development of new agents with even broader applications. The extensive clinical effort is augmented by past molecular innovations in the laboratory and the future promise of new discoveries. The cloning and sequencing of the ER (Green et al., 1986; Greene et al., 1986) has allowed the development of an ER knock-out mouse (Lubahn et al., 1993) that compliments Jensen's pioneering work (Jensen and Jacobson, 1962) and describes the consequences of the loss of ER alpha. However, ER beta (Kuiper et al., 1996), the second ER, has provided an additional dimension to the description of estrogen and antiestrogen action. For the future, the development of ER beta monoclonal antibodies, the classification of target sites for the protein around the body, and the creation of ER beta and ER alpha, beta knock-out mice will identify new therapeutic targets to modulate physiological functions. Clearly, the successful crystallization of ER alpha with raloxifene (Brzozowski et al., 1997) must act as a stimulus for the crystallization of ER beta. The central issue for research on antiestrogen pharmacology is the discovery of the mechanism (or mechanisms) of target site-specificity for the modulation of estrogenic and antiestrogenic response. The description of a stimulatory pathway for antiestrogens through an AP-1 ER beta signal transduction pathway (Paech et al., 1997), although interesting, may not entirely explain the estrogenicity of antiestrogens. The model must encompass the sum of pharmacological consequences of signal transduction through ER alpha and ER beta with the simultaneous competition from endogenous estrogens at both sites. This is complicated because estradiol is an antagonist at ER beta through AP-1 sites (Paech et al., 1997), so this is clearly not the pathway for estrogen-induced bone maintenance in women. Estrogen is stimulatory through ER alpha, but antiestrogens are usually partial agonists and may either block or stimulate genes. However, we suggest that the ER alpha stimulatory pathway could be amplified through selective increases in coactivators. The principle is illustrated with the MDA-MB-231 cells stably transfected with the cDNAs for the wild-type and the amino acid 351 mutan

Basic Guide to the Mechanisms of Antiestrogen Action

Antiestrogens and Selective Estrogen Receptor Modulators as Multifunctional Medicines. 2. Clinical Considerations and New Agents

BACKGROUND
The nonsteroidal antiestrogen tamoxifen is well established as an effective treatment for patients with breast carcinoma, both for the treatment of metastatic disease and as an adjuvant to surgery for patients with primary breast carcinoma. In addition to exerting antagonistic effects on the estrogen receptor, tamoxifen and its derivatives act as partial agonists on certain tissues. These agonistic effects, for example, endometrial stimulation and stimulation of tumor growth after previous response to tamoxifen, may limit their clinical efficacy. ICI 182,780 (Faslodex™) from AstraZeneca (Cheshire, United Kingdom) is a novel, steroidal estrogen antagonist that was designed to be devoid of estrogen agonist activity in preclinical models.

METHODS
ICI 182,780 was tested in a large number of in vitro and in vivo preclinical models, and its value was assessed clinically when administered before surgery for breast carcinoma and hysterectomy for benign conditions and after failure of tamoxifen in patients with advanced breast carcinoma.

RESULTS
All data indicated that ICI 182,780 is devoid of agonist activity in preclinical models and in clinical trials. It inhibits growth of the breast and endometrium. In animal models, it does not cross the blood-brain barrier and appears to be neutral with respect to lipids and bone. ICI 182,780 down-regulates the estrogen receptor and is active in tamoxifen-resistant breast carcinoma. In a small, Phase II study, durable responses were seen: Phase III clinical trials are in progress comparing ICI 182,780 with anastrozole and tamoxifen in the treatment of patients with advanced breast carcinoma.

CONCLUSIONS
ICI 182,780 specifically down-regulates the estrogen receptor and, thus, represents the first of a new class of therapeutic agents. In this report, the authors present the current evidence that distinguishes ICI 182,780 from tamoxifen and related nonsteroidal compounds and establishes ICI 182,780 as the first in a new class of therapeutic agents. Cancer 2000;89:817–25. © 2000 American Cancer Society.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1097-0142%2820000815%2989%3A4%3C817%3A%3AAID-CNCR14%3E3.0.CO%3B2-6

ICI 182,780 (Faslodex): development of a novel, "pure" antiestrogen.

DHEA and the intracrine formation of androgens and estrogens in peripheral target tissues: its role during aging

(S)-(+)-4-[7-(2,2-Dimethyl-1-oxopro- poxy)-4-methyl-2-[4-[2-(1-piperidinyl)- ethoxy]phenyl]-2H-1-benzopyran-3-yl]- phenyl 2,2-Dimethylpropanoate (EM-800): A Highly Potent, Specific, and Orally Active Nonsteroidal Antiestrogen

Acolbifene (EM-652·HCl, SCH 57068·HCl), a highly potent and orally active selective estrogen receptor modulator (SERM), is at late stage clinical development for the treatment of estrogen-sensitive breast cancer. Acolbifene-7-glucuronide 1 (major) and acolbifene-4′-glucuronide 2 (minor) were identified as metabolites of acolbifene in the human. The two monoglucuronides and a diglucuronide 3 as well as the corresponding 2H-labelled derivatives 4–6 were synthesised for use as preclinical and clinical standards for LC–MS/MS analysis. All glucuronides were prepared by the Schmidt glycosylation of monoprotected acolbifene with a glucuronyl imidate at −10°C to prevent epimerisation at the C-2 position. The two monoglucuronides 1 and 2 of acolbifene were separated by semi-preparative HPLC. Incorporation of three deuteriums was achieved by alkylation of chromanone 15 with C2H3MgI followed by dehydration with C2H3CO22H/2H2O. After chemical resolution and salt neutralisation, [2H3]acolbifene 19 was obtained with 99.4% enantiomeric purity and >98% isotopic purity. Copyright © 2007 John Wiley & Sons, Ltd.

Denis Larouche

Papers

(S)-(+)-4-[7-(2,2-Dimethyl-1-oxopro- poxy)-4-methyl-2-[4-[2-(1-piperidinyl)- ethoxy]phenyl]-2H-1-benzopyran-3-yl]- phenyl 2,2-Dimethylpropanoate (EM-800): A Highly Potent, Specific, and Orally Active Nonsteroidal Antiestrogen

Synthesis and deuterium labelling of the pure selective estrogen receptor modulator (SERM) acolbifene glucuronides