V. M. Rzheznikov

Comparative analysis of the effect of gestagens, antiestrogencytostatics, and androstenes on the viability of tumor and normal cells

The hormonal compound with the highest cytostatic activity against MCF-7 tumor cells (human breast cancer, BC) and the lowest activity against normal cells (rat skin fibroblasts) was sought among gestagens, androstenes, and antiestrogencytostatics. It was found that antiestrogencytostatics and androstenes had the highest cytostatic activity against tumor cells whereas gestagens and antiestrogencytostatics were least active against fibroblasts. Studies of the activity of the hormonal compounds in combination with doxorubicin on the viability of MCF-7 and rat skin fibroblasts found that all investigated compounds with the exception of dehydroepiandrosterone (DHEA) intensify the cytostatic activity of doxorubicin against tumor cells, the greatest effect seen for antiestrogencytostatics. A chemoprotective effect of androstenes on normal cells was noted.

Antitumor steroids. 3. Synthesis and biological activity of 11β-hydroxyestra-1,3,5(10)-triene derivatives with bis-(2-chloroethyl)amino-containing substituents in the 3-position

A series of antitumor compounds combining cytotoxic and estrogen action have been synthesized on the basis of 11β-acyloxyestra-1,3,5(10)-trienes. The corresponding synthons, 11β-hydroxy derivatives of estrone, estradiol, and ethynylestradiol, were obtained by oxidative nitration of 3-mono-and 3,17-diesters of these estrogens with ceric ammonium nitrate into the corresponding 9α-hydroxy-and 11β-nitroxy analogs with subsequent hydrogenolysis of the 9-hydroxy groups and removal of the nitrate protecting groups.

Cytotoxic steroids with antiestrogenic activity of the 11α-acyloxyestra-1,3,5(10)-triene series

Esterification of 3-hydroxyl group in 11α-acyloxyestra-1,3,5(10)-trienes with p-[bis(2-chloroethyl)amino]phenyl acetic acid led to antitumor steroids displaying antiestrogenic and cytotoxic activities. Our substances exhibit their activities on the model of murine mammary adenocarcinoma Ca-755, with inhibition of the tumor growth being 94–99%. A new approach was used to the 11α-hydroxylation of estra-1,3,5(10)-trienes.

Search for new drugs

Analogs of 11β-hydroxyestrone and 17α-ethynylestradiol with a cytotoxic bis-(2-chloroethyl)amino-containing substituent were synthesized in two principal steps from the corresponding 11-hydroxysteroids. Introduction of this bulky fragment influences negatively the estrogenic and antitumor activities of the synthesized compounds.

Steroidal nitrates. Part III. Synthesis and antiestrogen activity of the 11α-nitroxy analog of ethynylestradiol

An 11α-nitroxy group was introduced into 17α-ethynylestradiol-3,17-diacetate using a synthetic scheme involving oxidative nitration by cerium ammonium nitrate and configuration inversion at C11 by sodium-borohydride reduction of the 11-nitrate 9α,11β-dihydroxy derivative of the starting steroid. The 11α-nitroxy-containing ethynylestradiol exhibits antiestrogen activity.

Steroid nitrates. II. Synthesis and hormonal activity of 9α,11β-dihydroxyestra-1,3,5(10)-triene 11-nitrates

Abstract11-Nitrates of 9α,11β-dihydroxy derivatives of estrone, estradiol, and ethinylestradiol were synthesized by oxidative nitration of the corresponding estratriene 3-acetates with cerium ammonium nitrate. Three methods are given for this reaction. Compounds had high antifertility and estrogen activity. Antifertility actions were much greater than their estrogen activities, as compared with the similar levels seen with ethinylestradiol.

Investigation of the Gestagen Activity of 17α-acetoxy-3β-butanoyloxy-6-methylpregna-4,6-dien-20-one

The gestagen activity of a new synthetic progesterone derivative, 17α-acetoxy-3β-butanoiloxy-6-methylpregna-4,6-dien-20-one (ABMP) has been studied in rabbits (Clauberg - McPhail test) and in rats (test for the ABMP influence on the progesterone level in blood and on the endometrium morphology). The gestagen activity of ABMP is more pronounced than that of reference drugs (progesterone, levonorgestrel, acetomepregenol). ABMP transforms the endometrium of experimental animals from proliferative to secretory phase and reduces mitotic activity of endometrium in rats. ABMP reduces progesterone level in the rat blood to a lower degree than do the reference drugs. ABMP exhibits no anabolic and androgenic activity in the Hershberger test in rats.

Steroidal Nitrates: Synthesis and Antitumor Activity of 9α,11β-Dihydroxyestra-1,3,5(10)-triene 11-Nitrates

Steroidal nitrates, in contrast to other inorganic acid esters such as sulfates, are not encountered in nature. Nitration was used only as a means of protecting hydroxy groups [1]. The biological properties of steroidal nitrates are still insufficiently studied, although the spectrum of action can be rather wide. This was demonstrated by the experimental results for 11-nitrates of 11 -hydroxyand 9 ,11 -dihydroxy derivatives of estrone and estradiol, which first showed a high estrogen activity and then revealed the contraceptive properties of these compounds [2, 3]. In continuation of the study of the biological activity spectrum of 11-nitrates of 9 ,11 -dihydroxyestratrienes, we turned to evaluation of their antitumor properties. This interest was inspired by the fact that steroidal nitrates can generate nitric oxide, an agent known to produce a cytotoxic action, besides others [4]. Below we describe the synthesis of 11-nitrates of 9 ,11 -dihydroxyestratrienes containing various substituents in positions 3 and 17 and present data on the antitumor activity of these compounds. The synthesized compounds include the derivatives of estrone (III), estrone acetate (IV), 17-oxime (VI), and oxime diacetate (VII); ethinylestradiol derivatives were represented by 3,17-diacetate (V). The target nitrates were synthesized using the well-known process of nitration with cerium ammonium nitrate [5]. However, estrone acetate and ethinylestradiol 3,17-diacetate were nitrated in a heterogeneous regime, rather than in acetic acid under usual conditions requiring large volumes of solvent (see experimental chemical part below). Note that the oximation of nitrate IV is of interest both as a pathway to potential antitumor drugs and as a means of protecting 17-keto group, opening a simple way to 11 and 11 -hydroxyestrones [6].

A Simple Method of Obtaining 11-Keto-9β-estra-1,3,5(10)-trienes: Potential Reactants for the Synthesis of Steroidal Antigestagens

In recent years there have been extensive investigations into the chemistry and biology of 11-aryl-norsteroids known to possess a broad spectrum of physiological properties, in particular, antigestagen activity [1]. These compounds are capable of competing with natural gestagens for binding to receptors of the reproductive organs of females, thus violating normal development of the fetus. In contrast to traditional oral contraceptives, antigestagen preparations can not only prevent but, owing to their abortive action, terminate gestation. Among the abortive contraceptives, most widely used is the drug mifepristone (RU-486) reproduced in Russia as pencroftone. RU-486 and its analogs are obtained by partial syntheses from estrone. All variants of the synthesis, while differing in the number of stages and or the way of protecting the 3-keto group, employ only estra-5,9-diene-3,17-dione as the initial compound [2 – 4]. At the same tine, the synthesis of related 11-alkyl-19-norsteroids was frequently performed using 11-ketoestrogens, representing steroids with aromatic ring A [5]. These compounds, albeit considered among possible reactants in the synthesis of 11-aryl-19-norsteroids [6], were never used in practice – apparently because of the lack of sufficiently economic and technologically simple methods for their production. The known syntheses, for example, of 11-keto-9 -estrone (compounds with the 9 configuration are most stable in the series of 11-ketoestratrienes [7]), include three principal stages: (i) dehydration with 2,3-dichloro-5,6-dicyano-1,4benzoquinone (DDB), (ii) epoxidation with superacid, and (iii) epoxide conversion into ketone under the action of Lewis acid (BF3, Et2O, LiClO4) [7]. All these schemes possess drawbacks related to the difficulties in reproducing the first stage even for simple 17-analogs of estrone; attempts at using relatively cheap and accessible chloranil instead of DDB were unsuccessful [8 – 10].

Antitumor activity of various medicinal forms of the new estrogenocytostatic drug cytestrol acetate

Previously, estrogens were extensively used in practical oncology for the treatment of hormone-receptive malignancies such as breast and prostate carcinomas. At present, the administration of estrogens is restricted because of their strong side effects upon the cardiovascular and blood-coagulation systems. At the same time, there is growing interest in the use of estrogens as carriers of cytotoxic groups for the selective treatment of hormone-receptive tumors. This has resulted in the synthesis of a number of so-called estrogenocytostatic drugs, some of which (stilbostat, bustramustine, estracyt) have found practical application. A collaboration of the Blokhin Oncological Research Center and Scientific Endocrinological Center of the Russian Academy of Medical Sciences led to the development of a new approach to the creation of various types of estrogens, including previously unknown preparations possessing antihormonal activity. This approach is based on the use of 1 l ct-hydroxy derivatives of estradiol, ethynylestradiol, and estrone (these series are known to contain antiestrogens). In order to provide for the most complete structural-functional analysis of the new estrogenocytostatics, we have also studied the l l]3-epimers known as strong hormones. An alkylating fragment was introduced into position 3 or 11 of the initial steroids either by conventional etherification methods or by esterification reactions [1, 2]. The structural-functional analysis of the results allowed all the synthesized compounds to be separated into four groups with respect to their hormonal activity, including strong and weak estrogens, substances possessing the antiestrogen activity, and compounds exhibiting no hormonal action [3]. As for the antitumor activity, the compounds were also divided into four groups, representing the agents with high and moderate activity, inactive substances, and the compounds stimulating tumor growth [4]. Among the series of compounds combining high antitumor activity with antiestrogen properties, a