Table 2. Inhibition of E2-Induced Transactivation Determined in a Luciferase Reporter Gene Assay (ERα and ERβ) Using U2OS Cells, Transiently Transfected with Plasmids pSG5-ERα or pSG5-ERβ and the Reporter Plasmid p(ERE)2-luc⁺.

	compound	transactivation ERα	transactivation ERβ
		IC50a [nM]	IC50a [nM]
thioxo-quinazolinones	15	30.2 ± 14.3	4.1 ± 0.6
	16	18.5± 1.8	7.5 ± 1.3
	17	104 ± 14	48.0 ± 12.0
	18	914 ± 50	157± 22
5-methoxybenzimidazole	31	9.7 ± 8.9	6.7 ± 2.7
	32	21.5 ± 10.7	26.9 ± 5.7
	34	34.5 ± 3.5	11.6 ± 5.5
	36	9.2 ± 3.2	8.9 ± 4.0
	38	9.4 ± 2.7	9.0 ± 3.3
5-hydroxybenzimidazole	39	26.0 ± 6.6	20.2 ± 8.6
	40	80.8 ± 16.4	18.7 ± 8.3
	41	107 ± 4	15.9 ± 1.7
	42	30.9 ± 8.7	46.5 ± 20.7
	43	20.0 ± 3.2	16.1 ± 7.0
references	GW7604	238 ± 74	154 ± 53
	fulvestrant	n.d.b	n.d.b
	4-OHT	2.3 ± 1.3	1.0 ± 1.3
	44	5.3 ± 3.2	3.6 ± 1.4

^aIC₅₀ values represent the means ± SD of ≥3 independent experiments,.

^bn.d., not defined.