IC50: 0.82 nM

CB1151 (0-100 nM; 5 days) inhibits MCF-7 cells growth, this cell proliferation is accessed by [ ³ H]-thymidine incorporation, exhibits an IC ₅₀ value of 0.82 nM. CB1151 (0-100 nM; 40 hours) exhibits activation of the IP9-type VD response element with a EC ₅₀ of 1.2 nM, the activation of IP9-type VD response elements shows a good correlation with inhibition of proliferation than the activation of DR3-type elements (EC ₅₀ =3.2nM) in MCF-7 cells transfected with the CAT reporter. CB1151 shows a functional dissociation constant (K _df ) value of 3.6 nM. The ligand concentration that provides 50% of protease-resistant VDR fragment is defined by K _df , this is different from that of the traditional dissociation constant (K _d ).