An orally bioavailable inhibitor of the enzyme cytochrome 450 side-chain cleavage (scc)(CYP11A1), with potential antineoplastic activity. Upon oral administration, CYP11A1 inhibitor ODM-209 targets, binds to and inhibits the activity of CYP11A1. This prevents the synthesis of all steroid hormones and their precursors. This may inhibit the proliferation of hormone-positive tumor cells. CYP11A1, a mitochondrial enzyme, catalyzes the conversion of cholesterol to pregnenolone (Preg), which is the first rate-limiting step in steroid hormone biosynthesis.