In vitro activity: Dutasteride inhibits type-1 5AR and type-2 5AR with IC50 of 6 nM and 7 nM, respectively. Dutasteride is 60-fold more potent than Finasteride in its initial Ki versus type 1 5AR and ~5-fold more rapid in inactivating the enzyme. Dutasteride inhibits (3)H-T conversion to (3)H-DHT and, as anticipated, inhibits T-induced secretion of PSA and proliferation in LNCaP cells. Dutasteride also inhibits DHT-induced PSA secretion and cell proliferation with IC50 of 1 μM in LNCaP cells. Dutasteride competes for binding the LNCaP cell AR with an IC50 of 1.5 μM. Dutasteride (10–50 μM) results in enhanced cell death, possibly by apoptosis, in steroid-free medium. Dutasteride reduces cell viability and cell proliferation in androgen-responsive (LNCaP) and androgen-unresponsive (DU145) human prostate cancer(PCa) cell lines. Dutasteride results in overexpressed genes included genes encoding for proteins involved in biosynthesis and metabolism of androgen (HSD17B1;HSD17B3;CYP11B2), androgen receptor and androgen receptor co-regulators (AR;CCND1), and signal transduction(ERBB2; V-CAM; SOS1) whereas, underexpressed genes (KLK3; KLK2; DHCR24) are androgen-regulated genes (ARGs) in androgen-responsive (LNCaP) cell. Dutasteride inhibits FASN mRNA, protein expression and enzymatic activity in prostate cancer cells.

Kinase Assay: Dutasteride (GG745) is a potent inhibitor of both 5 alpha-reductase isozymes. Dutasteride may possess off-target effects on the androgen receptor (AR) due to its structural similarity to DHT. IC50 Value: Target: 5 alpha-reductase in vitro: Dutasteride inhibited (3)H-T conversion to (3)H-DHT and, as anticipated, inhibited T-induced secretion of PSA and proliferation. However the drug also inhibited DHT-induced PSA secretion and cell proliferation (IC(50) approximately 1 microM). Dutasteride competed for binding the LNCaP cell AR with an IC(50) approximately 1.5 microM. High concentrations of dutasteride (10-50 microM), but not finasteride, in steroid-free medium, resulted in enhanced cell death, possibly by apoptosis. 

Cell Assay: Dutasteride has been reported to inhibit conversion of 3H-testosterone to 3H-DHT by more than 99% in LNCaP cells. Dutasteride strongly reduces growth, proliferation, and viability of LNCaP cells as well. Dutasteride increased the enzymatic activities of caspase 7 and caspase 8 dose-dependently at 48 hours, providing functional significance and confirming that the apoptotic and survival pathways are being activated by dutasteride treatment in LNCaP cells.