text: Various pharmaceutical and academic groups have conducted the synthesis of nonsteroidal compounds that inhibit human 5α-reductases due to the unwanted hormonal side effects of steroidal compounds. Nonsteroidal inhibitors can be categorized due to their structure. Many have been obtained from azasteroid inhibitors by taking away one or more rings from the steroid structure.
  Four main categories of nonsteroidal 5-ARIs have been described:
  * Benzo(c)quinolizinones
  * Benzo(f)quinolonone
  * Piperidones
  * Carboxylic acids
  Nonsteroidal inhibitors are thought to act as competitive inhibitors on the 5α-reductase isozymes, except for epristeride analogues (carboxylic acids), which are noncompetitive inhibitors.
  Bexlosteride falls into the category of benzo(f)quinolonones, and is probably the derivative that has come closest to being marketed. It functions as a 5-ARI1 inhibitor which inhibits testosterone stimulated LNCaP cell growth but without testosterone the compound shows no effect and was therefore never marketed.