Cl-4AS-1 is a dual anabolicâÂÂandrogenic steroid (AAS) and 5ñ-reductase inhibitor. It is a potent and selective full agonist of the androgen receptor (IC<sub>50</sub> = 12 nM) and inhibitor of 5ñ-reductase types I and II (IC<sub>50</sub> = 6 and 10 nM, respectively). Structurally, Cl-4AS-1 is a 4-azasteroid.