Cortexolone 17α-propionate (WINLEVI, BREEZULA) is a steroid belonging to the family of cortexolone derivatives. It is a topical and peripherally selective androgen antagonist. WINLEVI is used for the treatment of acne and has completed Phase II clinical trials and Phase III trials. BREEZULA is used for the treatment of androgenic alopecia and is currently undergoing a Phase II trial in the US.

Finasteride is a synthetic 4-azasteroid compound. This drug is a competitive and specific inhibitor of Type II 5a-reductase, an intracellular enzyme that converts the androgen testosterone into 5α-dihydrotestosterone (DHT). Two distinct isozymes are found in mice, rats, monkeys, and humans: Type I and II. Each of these isozymes is differentially expressed in tissues and developmental stages. In humans, Type I 5a-reductase is predominant in the sebaceous glands of most regions of skin, including scalp, and liver. Type I 5a-reductase is responsible for approximately one-third of circulating DHT. The Type II 5a-reductase isozyme is primarily found in prostate, seminal vesicles, epididymides, and hair follicles as well as liver, and is responsible for two-thirds of circulating DHT. Although finasteride is 100-fold more selective for type II 5a-reductase than for the type I isoenzyme, chronic treatment with this drug may have some effect on type I 5a-reductase. Finasteride is used for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate to: Improve symptoms, reduce the risk of acute urinary retention, reduce the risk of the need for surgery including transurethral resection of the prostate. Also used for the stimulation of regrowth of hair in men with mild to moderate androgenetic alopecia (male pattern alopecia, hereditary alopecia, common male baldness). Finasteride is sold under the brand names Proscar and Propecia among others.

PGD2 (Prostaglandin D2) is a major cellular regulator, has been shown to bind different receptors: D prostanoid receptor (DP) and chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2). PGD2 reportedly inhibits platelet aggregation, the proliferation of cells, and activation of neutrophils. This compound is also a potent vasodilator that also relaxes smooth muscle but causes contraction of the bronchial airways. PGD2 promotes T cell migration via CRTH2 and aggravates asthma. In contrast, there have been some studies suggesting that PGD2 exerts anti-inflammatory effects via DP, such as inhibiting the migration and activation of neutrophils, basophils, dendritic cells and T cells. Elevated levels of prostaglandin D2 (PGD2) have been shown to be present in the bald scalp of androgenic alopecia (AGA) patients and was suggested the PGD(2)-GPR44 pathway as a potential target for treatment. Also was revealed, that PGD2 might be a new target for asthma therapy, PGD2 in serum and BALF were lower in the treated group than in the untreated group.

11-Epiprostaglandin E1 is a synthetic prostaglandin analogue. The activity of the racemic synthetic prostaglandin is approximately one-half that of the naturally occurring compound. 11-Epiprostaglandin E1 is 13%, 3.6% and 12%as potent as PGE1 in contracting the rat uterus, guinea pig ileum and rabbit jejunum, respectively. Nevertheless, this unnatural compound was proposed as a prostaglandin D2 receptor antagonist for use in the treatment of androgenic alopecia.

PF-998425 is a selective non-steroidal androgen receptor antagonist. It is rapidly metabolized systemically, and demonstrated efficacy for treatment of androgenic alopecia in preclinical model.

8-Epiprostaglandin E1 (8-iso-PGE1) arises by isomerization of PGE1. This isoprostane found in human semen. 8-iso-PGE1 has very low biological activity relative to PGE1. Intravenous administration of 8-iso-PGE1 decreased systemic arterial pressure slightly and increased heart rate and myocardial contractile force slightly. The magnitude of the systemic hypotensive effect of 8-iso-PGEl was equivalent to approximately 1/125 to 1/250 of that of PGE1 in dogs. On the other hand, the pulmonary hypertensive action of 8-iso-PGE1 was 5 times greater than that of PGE1. 8-iso-PGE1 is an agonist of prostanoid TP receptor. It was proposed as a prostaglandin D2 receptor antagonist for use in the treatment of androgenic alopecia.

RU58841 is a topically active non-steroidal antiandrogen. It demonstrated efficacy in animal models of androgen-dependent skin disorders such as acne and androgenetic alopecia. Under name of PSK 3841 was being developed by ProStrakan. It underwent clinical evaluation for the treatment of androgen-dependent conditions, such as acne and alopecia. Following the conclusion of phase II trials, no further development was reported. Based on this and the fact the compound is not listed on the companies pipeline, development is presumed discontinued.

Alfatradiol (17a-estradiol, Ell-Cranell® alpha) is a stereoisomer of the female hormone 17b-estradiol. It inhibits the conversion of testosterone to the metabolite dihydrotestosterone (DHT) by suppressing 5a-reductase activity. In addition, by inhibiting 17b-dehydrogenase, it impedes the conversion process of androstenedione to testosterone, resulting in a reduction in the syntheses of testosterone and DHT. It also accelerates the conversion of testosterone to estradiol by stimulating aromatase, decreasing the level of testosterone and leading to a reduction in DHT. In addition, alfatradiol (17a-estradiol) has been reported to stimulate the generation of hair follicular matrix cells.