Derivatives of vitamin D3 selected were 1α,24R,25(OH)3D3, which is the first major intermediate in 1,25(OH)2D3 inactivation produced by CYP24A1, and 20S,24R(OH)2D3, which is a product of the consecutive actions of CYP11A1 and CYP24A1 on vitamin D3, which has previously been shown to have biological activity, including on melanoma cells [40,41]. The gene discussed is CYP24A1; the disease is melanoma.