Dutasteride

Dutasteride (GG745) is a potent inhibitor of both 5α-reductase isozymes. Dutasteride may possess off-target effects on the androgen receptor (AR) due to its structural similarity to DHT^[1]. IC50 & Target: IC50: 5 alpha-reductase^[1] In Vitro: Dutasteride inhibits ³H-T conversion to ³H-DHT and, as anticipated, inhibits T-induced secretion of PSA and proliferation. However the drug also inhibited DHT-induced PSA secretion and cell proliferation (IC₅₀ approximately 1 μM)^[1].
Dutasteride competes for binding the LNCaP cell AR with an IC₅₀ approximately 1.5 μM. High concentrations of dutasteride (10-50 μM), but not finasteride, in steroid-free medium, resulted in enhanced cell death, possibly by apoptosis^[1].
Dutasteride reduces cell viability and cell proliferation in both cell lines tested (androgen-responsive (LNCaP) and androgen-unresponsive (DU145) human prostate cancer (PCa)) ^[2].
In Vivo: GG745 has a terminal half-life of approximately 240 hr, and single doses of >10 mg decreased DHT levels significantly more than did single 5-mg doses of finasteride^[3].
In placebo treated men without prostate cancer there was an 8.3% median increase in PSA at month 24 compared with -59.5% in those who received dutasteride, using doubled values to correct for dutasteride treatment^[4].
Toxicity: Dutasteride may affect male fertility and steroid hormone dynamics. Therefore, a 21-day reproduction study was conducted to determine the effects of dutasteride (10, 32 and 100 μg/L) on fish reproduction. Exposure to dutasteride significantly reduced fecundity of fish and affected several aspects of reproductive endocrine functions in both males and females^[5].