Table 2.

Inhibitory potencies of synthesized compounds 38–53 with 3-arylisoxazolo[5,4-d]pyrimidin-4(5H)-one scaffold against IDO1, IDO2, and TDO.

3-arylisoxazolo[5,4-d]pyrimidin-4(5H)-one scaffold
Compound	R1	R2	% of Inhibition @ 100 µM or IC50 a,b
			IDO1	IDO2	TDO
38			n.a. c	16 ± 4%	n.a.
39			IC50, 22 ± 2 µM	11 ± 7%	n.a.
40			IC50, 127 ± 5 µM	16 ± 5%	n.a.
41			32 ± 1%	n.a.	n.a.
42			15 ± 4%	n.d. d	n.d.
43			n.a.	n.d.	n.d.
44			n.a.	n.a.	n.a.
45			n.a.	n.a.	n.a.
46			14 ± 3%	n.a.	n.a.
47			34 ± 1%	n.a.	n.a.
48			IC50, 75 ± 4 µM	n.a.	10 ± 6%
49			IC50, 96 ± 5 µM	n.a.	10 ± 2%
50			n.a.	n.a.	n.a.
51			IC50, 53 ± 3 µM	n.a.	n.a.
52			23 ± 5%	n.a.	n.a.
53			IC50, 40 ± 2 µM	21 ± 6%	n.a.

^a IC₅₀ values are the means of at least two independent determinations, presented as mean ± SD; ^b Positive control: epacadostat (1), IC₅₀ values obtained for IDO1, IDO2, and TDO were 53, 580, and 9620 nM, respectively; ^c n.a., not active; ^d n.d., not determined.