Table 1.

Binding affinities of adenosine derivatives at rat A₁ and A_2AARs and at human and rat A₃ARs and maximal agonist effects at human A₃ARs expressed in CHO cells

Compound	N6 substitution	Ki (rA1AR) (nM)a	Ki (rA2AAR) (nM)a	Ki (rA3AR) (nM)a	Ki (hA3AR) (nM)a	Percent activation (hA3AR)
N6-Substituted analogues
Alkyl
1	CH3	60 ± 11	>10000	6390 ± 1630	9.3 ± 0.4	96 ± 3
2	CH3O	223 ± 32	>10000	997 ± 343	28.6 ± 4.7	107 ± 13
3	CH2CH3	4.9 ± 0.2	8900 ± 770	1050 ± 140	4.7 ± 1.9	102 ± 6
4	CH2C(CH3)3	17 ± 6	>10000	1870 ± 320	306 ± 80	76 ± 4
5	CH(CH3)2	1.9 ± 0.1	2030 ± 510	201 ± 38	18.3 ± 5.5	111 ± 4
6	CH(CH2CH3)2	0.8 ± 0.2	471 ± 200	147 ± 40	55.1 ± 9.5	99 ± 6
7	CH(CH((CH3)2)2	3.8 ± 0.8	2170 ± 490	753 ± 384	3760 ± 840	21 ± 2
Cycloalkyl
8	Cyclobutyl	0.7 ± 0.1	1740 ± 170	144 ± 64	6.4 ± 1.0	100 ± 7
9 CPA	Cyclopentyl	0.45 ± 0.04b	462c	240 ± 36c	72 ± 12	97 ± 4
10 CHA	Cyclohexyl	0.9 ± 0.2	514c	167 ± 26c	73 ± 23	76 ± 2
11	Cyclooctyl	1.7 ± 0.1	6200 ± 1120	498 ± 197	411 ± 55	49 ± 5
12	exo-2-Norbornyl	0.7 ± 0.2	3400 ± 140	253 ± 30	85 ± 31	114 ± 6
13 ENBA	(S)-endo-2-Norbornyl	0.34 ± 0.06	477 ± 72	282 ± 101	915 ± 299	23 ± 10
14	7-Norbornyl	0.48 ± 0.01	>10000	229 ± 76	112 ± 25	103 ± 1
15	1-Adamantyl	73 ± 3	14800 ± 3500	>10000	>10000	0
16	2-Adamantyl	46 ± 5	>10000	>10000	>10000	0
17	Cyclopropylmethyl	0.8 ± 0.3	1370 ± 410	608 ± 242	10.2 ± 4.1	108 ± 4
18	Dicyclopropylmethyl	0.8 ± 0.2	590 ± 30	772 ± 200	41.3 ± 5.3	31 ± 6
19	Cyclohexylmethyl	19 ± 7	>10000	2550 ± 1610	263 ± 73	38 ± 3
Aryl-containing
20	Phenyl	3.3 ± 0.3	663c	802 ± 279c	14.9 ± 3.1	102 ± 9
21	Benzyl	175 ± 20	285c	120 ± 20c	41.3 ± 5.3	55 ± 3
22	2-Phenylethyl	24.0 ± 8.8d	161c	240 ± 58c	2.1 ± 0.4	84 ± 5
23	2-Phenylethoxy	225 ± 45	>10000	8660 ± 2900	88.7 ± 7.4	73 ± 6
24 ADAC	4-[[[4-[[[(2-Aminoethyl)amino]-carbonyl]-methyl]aniline]-carbonyl]methyl]phenyl	0.85c	210c	185 ± 64	13.3 ± 3.0	103 ± 4
25 Metrifudil	2-Methylbenzyl	59.6 ± 14.3e	24.1 ± 1.8e	35 ± 15	47.2 ± 10.8	100 ± 3
26	2-Methoxybenzyl	36 ± 2	761 ± 460	29 ± 11	32.5 ± 4.6	81 ± 8
27	2-Fluorobenzyl	6 ± 1	551 ± 282	60 ± 8	339 ± 5	67 ± 7
28	2-Chlorobenzyl	17 ± 3	93 ± 16	13 ± 1	17.3 ± 3.2	95 ± 1
29	3-Chlorobenzyl	45 ± 10	>10000	35 ± 20	4.4 ± 1.7	80 ± 3
30	4-Chlorobenzyl	61 ± 3	5120 ± 1230	96 ± 38	47.5 ± 4.1	96 ± 2
31	2-Pyridylmethyl	225 ± 5	>10000	111 ± 32	115 ± 33	73 ± 15
32	3-Pyridylmethyl	115 ± 4	3220 ± 1210	288 ± 67	4.5 ± 1.1	100 ± 6
33	4-Pyridylmethyl	70 ± 5	3860 ± 1520	67 ± 9	80.1 ± 20.0	99 ± 12
34	2-Furanylmethyl	95 ± 9	>10000	301 ± 72	21.8 ± 3.9	54 ± 10
35	2-Thienylmethyl	36 ± 7	734 ± 60	112 ± 33	59.8 ± 25.7	92 ± 2
36	3-Thienylmethyl	45 ± 9	3300 ± 450	297 ± 53	26.3 ± 8.2	97 ± 8
37	1-Naphthylmethyl	13 ± 3	1120 ± 580	2.7 ± 0.5	25.2 ± 9.7	67 ± 8
38	R-1-Phenylethyl	3.4 ± 0.4	1300 ± 620	60 ± 25	113 ± 22	76 ± 10
39	S-1-Phenylethyl	195 ± 20	>10000	1110 ± 460	68.7 ± 17.3	83 ± 5
40	R-1-Indanyl	65 ± 10	2480 ± 740412f	79 ± 12	233 ± 27	82 ± 5
41 R-PIA	R-1-Phenyl-2-propyl	1.2 ± 0.1	124c	158 ± 52c	8.7 ± 0.9	102 ± 6
42 S-PIA	S-1-Phenyl-2-propyl	49.3c	1820c	920 ± 311c	68 ± 12	97 ± 3
43	R-1-Phenyl-2-pentyl	3.34 ± 0.66d	>10000	76 ± 18	70.9 ± 26.2	92 ± 9
44	S-1-Phenyl-2-pentyl	282 ± 17d	>10000	1810 ± 530	37 ± 13	101 ± 10
45	R-1-Phenyl-isopentyl	8.89 ± 1.97d	3250 ± 580	103 ± 43	96 ± 17	77 ± 4
46 DPMA	2-(3,5-Dimethoxy-phenyl)-2-(2-methylphenylethyl	142c	4.4c	3570 ± 1700c	106 ± 22	0
47	(1R,2S)-2-Phenyl-1-cyclopropyl	15.2 ± 3.2d	3040 ± 490	358 ± 33	24.1 ± 10.9	87 ± 4
48	(1S,2R)-2-Phenyl-1-cyclopropyl	11.8 ± 2.4d	560 ± 232	694 ± 157	0.63 ± 0.17	117 ± 9
49	cis-(1R,2R)-2-Phenylcyclohexyl	15 ± 6	>10000	1170 ± 30	1450 ± 241	73 ± 12
50	trans-(1R,2S)-2-Phenylcyclohexyl	6 ± 3	672 ± 51	279 ± 41	559 ± 96	72 ± 9
Compound	Substitution	Ki (rA1AR) (nM)	Ki (rA2AAR) (nM)	Ki (rA3AR) (nM)	Ki (hA3AR) (nM)	Percent activation (hA3AR)
Other halo analogues
51 CADO	2-Chloro	6.7 ± 1.0b	63e	1890 ± 900e	87 ± 24	100 ± 7
52 FADO	2-Fluoro	68.3 ± 18.9d	28c	4590 ± 2410	99 ± 13	31 ± 3
53	2-Chloro-R-PIA	0.86 ± 0.14d, 1.4 ± 0.1g	1070 ± 250	34 ± 10	13.1 ± 0.9	76 ± 13
54	5′-Chloro-5′-deoxyadenosine	20 ± 1b	62.7 ± 14.4	4590 ± 2410	107 ± 6	9 ± 4

^aAll A₃AR experiments were performed using adherent CHO cells stably transfected with cDNA encoding the human or rat A₃ receptor. Percent activation of the human A₃AR was determined at 10 µM. Unless otherwise noted, K_i values at A₁AR are from Daly et al. [10]. Binding at A₁ and A_2AARs was carried out as described in Section 2. Values from the present study are means ± SEM, N = 3–5.

^bData from Daly and Padgett [19].

^cData from Van Galen et al. [16].

^dK_i values at the A₁AR determined in the present study.

^eData from Siddiqi et al. [20].

^fData from Trivedi et al. [17].

^gData from Thompson et al. [18].