Androgen action is the net result of opposing pathways of steroid biosynthesis and metabolism. It is now widely recognized that testosterone (T) is an androgenic precursor of the more potent 5?-dihydrotestosterone (DHT), produced by 5?-reductase type 2. Circulating T and DHT also serve as precursors of estrogens through their conversion to estradiol and estrone by aromatase. Thus, regardless of gender, these secreted steroids are converted peripherally into divergent signals for two members of the steroid hormone nuclear receptor family. The overproduction of androgens in both sexes is the root cause of most acne (acne vulgaris), alopecia and seborrhea, and the practice of using antiandrogenic therapy in these disorders is accepted. However, the systemic antiandrogen side effects of marketed nonsteroidal androgen antagonists (flutamide, nilutamide, bicalutamide) and 5?-reductase type 2 inhibitors (finasteride) are serious drawbacks to their repeated use, and some are contraindicated in pregnant women. While acne vulgaris is the most prevalent skin disorder in humans, the other diseases are also relatively common. All of the current therapies for these disorders, including over the counter medications, treat the symptoms but not the excess skin androgens. In addition, all current treatments for these disorders have local and systemic side effects. Severe forms of these skin disorders, e.g. cystic acne, are largely untreatable and represent a significant unmet medical need. We and our collaborators at Hygeia Therapeutics Inc. have identified a synthetic antiandrogenic compound - (S)-HYG-440 - a chiral ester that potently binds the androgen receptor and reduces androgenic functional activity in cell cultures. In contrast, its hydrolysis product - (S)-HYG-441 - is devoid of both activities. (S)-HYG-440, applied topically to one hamster flank, reduced the size of this organ but only on the ipsilateral side These results suggest that this drug is a """"""""soft antiandrogen"""""""", expected to be active topically in androgen-dependent maladies of the skin and scalp, but to be hydrolyzed by plasma or tissue enzymes, thus terminating its systemic action. Indeed, (S)-HYG-440 is readily hydrolyzed after incubation in animal plasmas.
The specific aims to answer the fundamental question """"""""is (S)-HYG-440 actually a """"""""soft"""""""" drug?"""""""" include: synthesis by yet newer methods of both (S)-HYG-440 and (S)-HYG-441 as candidate drug and metabolic product, respectively;the latter will serve also as toxicology sample and marker for further analyses;application of (S)-HYG-440 to the skin of hamsters, and analysis of plasma and tissue extracts for uptake and distribution of the parent compound and its conversion to (S)-HYG-441;and toxicity testing of the hydrolysis product (S)-HYG-441 in vitro and in vivo the hamster. Although inhibition of androgen action to treat acne, seborrhea and alopecia in men and women (and hirsutism in women) is efficacious, it can carry serious systemic risks. However, because all of these maladies are localized to the skin, it follows that local treatment would carry a higher benefit-to-risk ratio compared to orally administered therapies. Unlike all other antiandrogens or 5?-reductase inhibitors on the market or in development, (S)-HYG-440 was designed to avoid systemic activity by taking advantage of esterases and hydrolases found in most tissues in the body for metabolic deactivation, i.e. as a metabolically """"""""soft"""""""" drug. The antiandrogenic activity of the prototype compound (S)-HYG-440 may be limited to the parent drug because its putative hydrolysis product has no detectable affinity for the androgen receptor. An antiandrogen specifically designed to act locally would minimize or avoid unwanted systemic antiandrogen effects. The synthesis and discovery of an optimal locally active androgen antagonist to be applied to the skin to treat acne, alopecia, seborrhea (and hirsutism in women) are the subjects of this application.
Secreted androgenic steroids are converted into male and female hormones in both sexes. Because the androgenic hormones are responsible for acne, alopecia and seborrhea, the rationale for using antiandrogenic therapy for their treatment is strong. Our lead compound (S)-HYG-440 has shown efficacy in vivo after topical application in the hamster, and may behave as a metabolized soft drug. The purpose of this project is to obtain direct evidence for this hypothesis and to obtain toxicity of the presumed metabolite (S)-HYG-441.
