Gary H. Rasmusson

5α-Reductase inhibitory and anti-androgenic activities of some 4-azasteroids in the rat

Abstract Inhibition of 5α-reductase and anti-androgenicity were studied in rats treated with various 4-azasteroids. The known inhibitor, N,N-diethyl-4-methyl-3-oxo-4-aza-5 α-androstane-17 β-carboxamide (4-MA) served as a reference compound, and analogs of this basic molecule were assayed. Enhancement of enzyme inhibitory potency was usually seen with Δ1 analogs, whereas reduction in activity was noted with substitutuents such as Δ5, a spirotetrahydrofuran ring at C-17 or 4-deaza groups. Many of the 4-azasteroids had a much greater oral anti-androgenic effect against testosterone propionate (TP) than dihydrotestosterone propionate (DHTP). This difference in activity versus the two androgens is believed to reflect the necessity for TP to undergo reduction to DHT before becoming capable of stimulating prostatic growth. Inhibition of 5α-reductase by active compounds prevented the conversion, thereby producing an anti-androgenic effect. In this regard, certain Δ1 analogs of 4-MA, particularly those bearing a 17β-(N-tert butylcarbamoyl) group, proved very effective against TP but were relatively inactive versus DHTP.

Biochemical and biological studies with 4-aza-steroidal 5α-reductase inhibitors

Summary A series of 4-aza-3-oxosteroids were found to be good inhibitors of steroid 5α-reductase. Two of these compounds. 17 β-N,N -diethylcarbamoyl-4-methyl-4-aza-5α-androstan-3-one (4-MA) and 4-methyl-4-aza-5α-pregnan-3-one-20(s)-carboxylate, inhibit 5α-reductase competitively with testosterone (T) with K i values of 5 and 1.7 nM, respectively. These 5α-reductase inhibitors also have an affinity to the androgen receptor which is orders of magnitude lower than that of 5α-dihydrotestosterone (DHT), spironolactone and cyproterone acetate. 4-MA decreases the prostatic concentration of DHT and increases that of T in intact male rats and in castrates given T or its propionate derivative. 4-MA is a better inhibitor of T-induced growth than of DHT-induced growth of the prostate and seminal vesicles in castrated rats. It decreases the weight of the prostate and seminal vesicles in intact rats and that of the prostate in dogs. It has no significant antifertility activity in rats. In pregnant rats, 4-MA reduces the ano-genital distance of male fetuses. 4-MA has no significant androgenic, estrogenic, progestational, antiprogestational or antigonadotrophic activity.

Biological Activities of a New Steroidal Inhibitor of δ4-5α-Reductase

Abstract 17β-N,N-Diethylcarbamoyl-4-methyl-4-aza-5α-androstan-3-one (4-MA), a known 5α-reductase inhibitor, was tested in a variety of bioassays designed to document its endocrinological spectrum. It proved to be a relatively nontoxic compound which showed little or no antifertility activity in either male or female rats, no significant estrogenic, progestational, androgenic, or gonadotropin-inhibiting potency, and it did not affect serum prolactin levels. 4-MA did, however, cause feminization of male fetuses carried by treated pregnant female rats. It also caused a cessation in growth of the ventral prostate and seminal vesicles of young adult male rats. Both the feminization of male fetuses and the inhibition of male sex accessory growth are believed to be a result of the inhibition of 5α-reductase by 4-MA.

Azasteroids as inhibitors of testosterone 5α-reductase in mammalian skin

Abstract Elevated levels of testosterone 5α-reductase (5α-R) and its product, dihydrotesterone are associated with a number of androgen-dependent skin conditions. A series of 4-azasteroids were tested in vitro as inhibitors of 5α-R in the isolated anagen human hair follicle. Major structural requirements for maximal 5α-R inhibitory activity include a 4-methyl-4-aza moiety and a bulky, lipophilic side chain at C-17. Only one compound, 17 β - N , N -diethylcarbamyl-4-methyl-4-aza-5 α -androstan-3-one (4-MA), was found to be a potent 5α-R inhibitor in all tissues studied: human hair follicles, foreskin ( K i =3 nM), genital fibroblasts ( K i = 12 nM), and prostate. 17β-Hydroxysteroid dehydrogenase activity was not inhibited by 4-MA. With the exception of 4-MA, azasteroid IC 50 s varied widely in human prostate vs skin, suggesting the possible existence in man of at least two 5α-R isozymes. Finasteride [ N (1,1-dimethylethyl)-3-oxo-4-aza-5 α -androst-1-ene-17 β -carboxamide], a Δ 1 orally active, specific 5α-R inhibitor exhibiting no affinity for the androgen receptor, was only modestly active in the hair follicle microassay (IC 50 = 200 nM). However, it was a potent in vitro inhibitor of human foreskin and prostate 5α-R. Orally administered to rats finasteride inhibited 5α-R in skin. A vasodilator used to treat male pattern baldness (MPB), minoxidil, was found to be a weak inhibitor of human hair follicle 5α-R (IC 50 = 1000 nM). 5α-R activity in frontal scalp hair follicles from a MPB subject was four times higher than in occipital follicles. 4-Azasteroids are efficient inhibitors of human skin 5α-R and offer promise for the treatment of acne, hirsutism and MPB.

Substituted penta- and hexapeptides as potent inhibitors of herpes simplex virus type 2 ribonucleotide reductase

Abstract Structural modifications of the Tyr, Asn, and Leu residues of YVVNDL, a peptide which is equipotent to YAGAVVNDL in the inhibition of herpes simplex virus type 2 ribonucleotide reductase (HSV-2 RR), have produced peptides which are as much as 90- to 120-times as potent as YAGAVVNDL in vitro against HSV-2 RR. The chemistry and the structure activity relationships of these inhibitors are described. For the inhibition of herpes simplex virus type 2 ribonucleotide reductase (HSV-2 RR), structure-activity relationship studies on Y, N, and/or L of YVVNDL (equipotent to YAGAVVNDL on HSV-2 RR) using synthetic peptides are reported. The most potent of these, YVV-N(Nγ-Me2)-D-L(γ-Me), and (Bzl)2CHCO-VVND-L(γ-Me) had relative potencies of 110 and 120, respectively, relative to YAGAVVNDL.

Topical anti-androgenicity of a new 4-azasteroid in the hamster

The topical anti-androgenic activity of L-651,580 (methyl 3-oxo-4-methyl-4-aza-5 alpha-androst-1-ene-17 beta-carboxylate) was established in a series of for experiments using castrated male hamsters. During each 21-day experiment, the animals received a daily subcutaneous injection of 40 micrograms testosterone propionate or 20 micrograms dihydrotestosterone propionate. Test compound in 25 microliters of gel was applied daily to the left flank organ. Compounds assayed included L-651,580, WIN 17,665 (17 alpha-propyltestosterone), and SH-434 (17 beta-hydroxy-1 alpha-methyl-17 alpha-propyl-5 alpha-androstan-3-one). Endpoints were flank organ area, sebaceous gland area, and prostate weight. Very similar results were obtained with L-651,580 and WIN 17,665. Daily doses of 0.25 mg or more of either compound usually produced a significant reduction in the areas of treated flank organs and sebaceous glands underlying treated flank organs. Neither compound caused significant changes in the area of the contralateral flank organs and sebaceous glands, which indicated they possess little or no systemic activity at topically effective treatment levels. In direct comparisons, SH-434 was less anti-androgenic than L-651,580 or WIN 17,665, although in one experiment, 0.5 mg/d of SH-434 significantly reduced the area of treated flank organs and sebaceous glands. Neither WIN 17,665 nor SH-434 caused a change in prostate weight; however, in one of four tests, a significant decrease was induced by the 0.5 mg/d level of L-651,580. The results of these experiments show that the topical anti-androgenicity of L-651,580 compares very favorably with that of WIN 17,665 and SH-434. They also indicate that the topical administration of effective dosage levels of L-651,580 causes few, if any, systemic effects.

Chapter 18. Chemical Control of Androgen Action

Publisher Summary Androgens originate primarily from three glands: the testes, the adrenal cortex and the ovary. The androgen level in an individual is dependent on a balance of several interrelated stimulatory and inhibitory processes. Excess androgenic activity is implicated in precocious puberty, male hypersexuality, seborrhea, acne, male pattern baldness, and hirsutism. Prostate size and maintenance are androgen dependent, suggesting that interference with this hormone would be a treatment for benign prostatic hyperplasia (BPH) and prostatic carcinoma (PC). Male fertility control would be possible if T-stimulated spermatogenesis could be blocked. Treatments that interfere with androgen action include administration of agents that block regulatory mechanisms, the androgen receptor (AR) or key biosynthetic steps in the formation of 5 α-dihydrotestosterone(DHT). This chapter discusses recent developments in methods for limiting and abolishing androgen action. In interference with control regulatory mechanisms, there is review of hormones estrogens, progestins, and LHRH analogues. On androgen receptor (AR) antagonists, the chapter studies flutamide and non-steroidal antagonists, cymoterone acetate, 17 β-hvdroxysteroids, and 11-oxynenated steroids. The chapter also reviews biosynthesis inhibition of 17.20-Desmolase, 3β-01 Dehydrogenase and 5α-reductase. The use of LHRH analogs, alone or in the presence of androgen antagonists or synthesis inhibitors, now provides a highly effective and safe alternative to surgical castration in the treatment of PC.

A stereoselective synthesis of 7β-phenyl and 7β-methylcholesterol

Abstract A stereoselective synthesis of 7β-phenylcholesterol and 7β-methylcholesterol is described.

Chapter 23. Therapeutic Control of Androgen Action

Publisher Summary Circulating C1g steroids, secreted from the testis, adrenal, and ovary serve as the source of hormonal androgens for endocrine function. Two androgens, testosterone (T) and 5a dihydrotestosterone (DHT) are responsible for the activation of the intracellular androgen receptor (AR) that, in turn, regulates gene transcription, and ultimately protein synthesis. Two major approaches have been employed to control androgen action: modulation of the AR-hormone interaction and inhibition of hormone production. The focus of this review are conditions that are amenable to hormonal manipulation and includes benign prostatic hyperplasia (BPH), prostatic carcinoma (PC), and skin-related problems, such as acne, seborrhea, androgenic alopecia, and hirsutism. Earlier reviews of these topics can be found in this series or elsewhere. The high incidence of BPH and PC in modern society has provided impetus for broadening the search for safe and specific agents to control agerelated phenomena of the androgen sensitive prostate gland. New agents, such as casodex and finasteride, appear to provide significant advances toward the treatment of PC and BPH, respectively, by offering ease of use and good side-effect profiles. The use of combined androgen ablation methods are likely to add to the length and quality of life for PC patients. Other approaches, such as the use of anti-sense DNA to block AR expression or blocking of the AR response elements on DNA, may lead to more specific effects, but their medical application appears to be more distant.

Selenium dioxide oxidation of vitamin D3 acetate to a dimer of 1-oxotransvitamin D3 acetate

The treatment of vitamin D3 acetate with selenium dioxide and t-butyl hydroperoxide leads to a mixture from which a Diels-Alder dimer of 1-oxotransvitamin D3 acetate was isolated.