A Study of the Efficacy and Safety of Multiple Doses of Dutasteride Versus Placebo and Finasteride in the Treatment of Male Subjects With Androgenetic Alopecia

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Androgenetic alopecia is a common, androgen-induced, pattern of progressive loss of scalp hair with an onset at any age after puberty in genetically predisposed people. The influence of androgens on scalp hair growth is mediated by local and systemic conversion of testosterone to dihydrotestosterone , by the enzyme 5 alpha-reductase. 5 alpha-reductase has been shown to exist as 2 isoenzyme forms, Type 1 and Type 2. Type 1 is predominantly located in the skin, both in the hair follicles and sebaceous glands, and is also found in the liver and kidney . Type 2 is the dominant form in male genitalia, including the prostate, although it has also been reported to be present in the inner root sheath of the hair follicle. The presence of both isoenzymes in the hair follicles suggests that both forms are likely to be important in the pathogenesis and treatment of androgenetic alopecia. Inhibition of both Type 1 and Type 2 5 alpha-reductase may be expected to more effectively reduce systemic and local dihydrotestosterone levels than inhibition of either isoenzyme alone. Finasteride is a selective Type 2 5 alpha-reductase inhibitor that is currently the only approved oral treatment for androgenetic alopecia worldwide. Dutasteride inhibits both Type 1 and Type 2 5alpha-reductase and is approved in more than 80 countries for the treatment of benign prostatic hyperplasia, and in Korea for the treatment of hair loss. Dutasteride is approximately 3 times as potent as finasteride at inhibiting Type 2 5 alpha-reductase and more than 100 times as potent at inhibiting Type 1 5 alpha-reductase. In a Phase II double-blind, placebo-controlled clinical study (ARIA2004) conducted in the United States, dutasteride demonstrated significant increases in target area hair count, as compared with placebo, as early as 12 weeks. In a Phase III double- blind, placebo-controlled clinical study conducted in Korea, dutasteride 0.5 milligram (mg) demonstrated significant increases in target area hair count, as compared with placebo, at 24 weeks. This 6 month study is being conducted to provide additional evidence of the efficacy and safety of three doses of dutasteride (0.02, 0.1 and 0.5mg) in the treatment of androgenetic alopecia, and more specifically, to characterize the dose-response relationship in an ethnically-diverse population. Treatment arms will be equally balanced with approximately 180 per arm.