CYP17A1, 3βHSD, SRD5A, androgen receptor

D4-abiraterone (D4A ) (10 mM) nearly completely blocks conversion from D4-androstenedione (AD) to 5α-androstanedione and other 5α-reduced androgens. The affinity of D4-abiraterone for mutant (expressed in LNCaP, half-maximum inhibitory concentration (IC ₅₀ =5.3 nM)) and wild type (expressed in LAPC4, IC ₅₀ =7.9 nM) androgen receptor (AR) is greater than that of abiraterone (Abi) (IC ₅₀ =418 and >500 nM, respectively). Compare with Abi, D4-abiraterone clearly better suppresses PSA, TMPRSS2 and FKBP5 expression in LNCAP, LAPC4 and C4-2 cell lines. D4-abiraterone also inhibits AR target gene expression in a dose-dependent manner.

D4-abiraterone (D4A) is tenfold more potent than abiraterone (Abi) in blocking conversion from dehydroepiandrosterone (DHEA) by 3β-hydroxysteroid dehydrogenase (3βHSD) to D4-androstenedione (AD) in LNCaP and VCaP xenografts. 0.1 μM D4-abiraterone is equivalent to 1 μM Abi for blocking AD accumulation at 48 h in both LNCaP and VCaP xenografts. Progression is significantly delayed in the D4-abiraterone group compare with the Abi acetate group (P=0.011). D4-abiraterone treatment increases progression-free survival compare with Abi acetate.