Table 2

Summary of [d-Ala²]deltorphin analogues in vitro BBB permeability, capacity factor and stability in 15% mouse brain membrane homogenate and 100% plasma

Compounds	Molecular Weight	Permeability Coefficient	Capacity Factor	Stability (Half-Lives hr)
Compounds	Molecular Weight	Mean ± S.E.M. cm/min × 10⁻⁴	k′	Brain	Plasma
1. [d-Ala²]deltorphin I	768.9	22.73 ± 0.22	11.54	4.8	3.2
H-Tyr-d-Ala-Phe-Asp-Val-Val-Gly-NH₂
2. [d-Ala²]deltorphin II	782.9	23.49 ± 2.42	11.29	9.8	2.7
H-Tyr-d-Ala-Phe-Glu-Val-Val-Gly-NH₂
3. [d-Ala²,Ser⁴,d-Val⁵]deltorphin	740.9	11.72 ± 0.30	12.57	>15	>15
4. [d-Ala²,Ser⁴,d-Ala⁵]deltorphin	712.8	14.07 ± 2.82	9.22	>15	>15
5. [d-Ala²,Gln⁴,d-Val⁵]deltorphin	781.9	6.70 ± 0.81	12.38	>15	>15
6. [d-Ala²,Gln⁴,d-Ala⁵]deltorphin	753.9	7.77 ± 1.41	9.22	>15	>15
7. [Arg⁻¹,Arg⁰,d-Ala²]deltorphin II	1275.4	16.12 ± 2.10	8.50	10 min	27 min
8. [Arg⁰,d-Ala²]deltorphin II	1059.2	19.06 ± 3.73	9.36	16 min	33 min
9. [Lys⁻¹,Lys⁰,d-Ala²]deltorphin II	1219.4	14.07 ± 2.82	8.21	7 min	15 min
10. [Lys⁰,d-Ala²]deltorphin II	1031.2	8.53 ± 0.58	9.28	27 min	59 min
11. [Ala⁻¹,Pro⁰,d-Ala²]deltorphin II	952.0	17.38 ± 1.01	11.95	52 min	16 min
12. [Pro⁻¹,Pro⁰,d-Ala²]deltorphin II	978.0	22.22 ± 5.93	12.41	43 min	13 min
13. [Abu⁻¹,Abu⁰,d-Ala²]deltorphin II	953.5	29.30 ± 1.70	13.08	10 min	10 min