Izonsteride (LY320236) is a selective and potent 5alpha reductase inhibitor with dual action on the type I and type II isoforms of the enzyme.Izonsteride is used in the treatment of oncology and genitourinary disorders, and may be used in the study of prostate cancer.

Izonsteride is a benzoquinolinone (BQ) that inhibits 5alpha-R activity in human scalp skin (Ki(typeI)=28.7+/-1.87 nM) and prostatic homogenates (Ki(typeII)=10.6+/-4.5 nM). Lineweaver-Burk, Dixon, and non-linear analysis methods were used to evaluate the kinetics of 5alpha-R inhibition by Izonsteride. Non-linear modeling of experimental data evaluated V(max) in the presence or absence of Izonsteride. Experimental data modeled to the following equation 1v=+ fixing the In0c value equal to 1.0 or 0 are consistent with non-competitive or competitive inhibition, respectively. Izonsteride is a competitive inhibitor of type I 5alpha-R (In0c=0, Ki=3.39+/-0.38, RMSE = 1.300) and a non-competitive inhibitor of type II 5alpha-R (In0c=1, Ki=29. 7+/-3.4, RMSE = 0.0592). These data are in agreement with the linear transformation of the data using Lineweaver-Burk and Dixon analyses. These enzyme kinetic data support the contention that the BQ Izonsteride is a potent dual inhibitor with differing modes of activity against the two known human 5-alpha-reductase isozymes. Izonsteride represents a class of non-steroidal 5alpha-R inhibitors with potential therapeutic utility in treating a variety of androgen-dependent disorders.[1]