Table 1.

Prodrug half-lives (t_1/2) in PBS (pH 7.4), Bovine serum, and Bovine CSF.

Compds	t1/2 (h)
	PBS	Bovine serum	Bovine CSF
4	13.60 ± 0.49	6.20 ± 0.17	7.59 ± 0.12
11	29.79 ± 0.42	ND	ND
12	25.59 ± 0.61	22.21 ± 0.52	25.47 ± 0.10
13	12.91 ± 0.17	ND	ND
14	1.51 ± 0.11	ND	ND
15	0.70 ± 0.04	0.69 ± 0.02	0.96 ± 0.04
16	0.22 ± 0.03	ND	ND
17	26.91 ± 0.71	ND	ND
18	11.16 ± 0.37	0.85 ± 0.12	1.85 ± 0.11
19	3.42 ± 0.10	ND	ND
21	2.21 ± 0.15	1.51 ± 0.04	2.11 ± 0.14

Standard deviations are based on three experiments;

ND = not determined.