Table 2.

Potency of 2-cycloalkyl substituted 1H-imidazo-[4,5-c]quinolin-4-amine derivatives in binding assays at the human A₁ and A₃ARs expressed in CHO cells and at the human A_2A in HEK-293 cells and the allosteric effects at the human A₃AR.^a

No.	R =	A1AR, %displ. at 10 μM	A2AAR, %displ. at 10 μM	A3AR, %displ. at 10 μM	A3AR ag. dissociation,c % at 10 μM	[35S]GTPγS binding in A3AR cells,d % at 10 μM
1b		−5.2	0.4	52	116±3	126±3b
2b		15	0	67e	144±9	141±5b
3		37±9	−11.2±2.8	40.5±13.4	192±7	208±14
4b		−4.2	−2.2	68	130±2	115±7b
16		37.2±8.6	−11.9±2.8	69.6±1.4	115±12	114±7
17		77.9±12.2	5.8±1.0	61.2±1.4	187±16	201±26
18		44.8±10.5	39.4±1.9	50.5±5.5	168±8	168±13
19		14.5±2.7	−17.3±6.9	3.3±4.1	139±10	156±2
20		13.8±6.9	−4.4±12.5	17.2±6.7	196±13	210±12
21		21.4±4.3	56.8±1.7	5.6±4.9	102±5	96±5
22		31.7±16.2	15.8±1.2	4.2±6.1	107±11	111±6
23		20.2±10.1	8.8±1.9	29.8±0.6	91±9	93±7
24		12.4±1.1	43.4±5.5	35.3±1.5	92±5	93±1
25		17.8±3.6	−3.1±1.6	46.3±0.8	93±6	97±5
26		10.9±8.6	7.0±0.7	52.8±1.1	101±7	99±3

^aAll experiments were performed using adherent mammalian cells stably transfected with cDNA encoding the human ARs. Binding at human A₁, A_2A and A₃ARs in this study was carried out as described in the Experimental Procedures using [³H]34, [³H]35, or [¹²⁵I]36 as a radioligand.¹⁹-²¹ Values from the present study are expressed as mean ± s.e.m., n = 3−5. Percentage inhibition at A₁, A_2A, or A₃ receptors is expressed as the mean value from 2−4 separate experiments with similar results performed in duplicate.

^bValues from Göblyös et al,¹⁵ the functional enhancement of which was measured with the cyclic AMP assay.²⁶

^cDissociation: % decrease of [¹²⁵I]36 dissociation at 60 min (control = 100%).

^dIncrease of efficacy in the stimulation of the binding of [³⁵S]GTPγS: compared to maximal effect induced by 10 μM 15 alone (set to 100%). It should be noted that the E_max of 15 in this functional assay was recently demonstrated to be about 50% of that of 37.¹⁷ In the adenylate cyclase assay, 15 and 37 were both full agonists.¹⁵

^eK_i value in a binding assay¹⁵ = 4690±970 nM.