The use of inactivated brain homogenate to determine the in vitro fraction unbound in brain for unstable compounds

Abstract

1. The use of IBH-5 decreased the k_deg values and increased the half-life of the compounds PNZ, TCP, Cpd I and Cpd II with k_deg values of 1.10 × 10⁻⁴s^{− 1} (t_1/2 ⁼ 115 min), 4 × 10⁻⁵s⁻¹ (t_1/2 = 289 min), 4 × 10⁻⁵s⁻¹ (t_1/2 = 289 min), and 3 × 10⁻⁵ s⁻¹ (t_1/2 = 385 min) respectively, compared to k_deg values of 1.25 × 10⁻² s⁻¹ (t_1/2 = 0.9 min), 1.1 × 10⁻⁴s⁻¹ (t_1/2 = 105 min), 1.0 × 10⁻³s⁻¹ (t_1/2 = 11.5 min) and 4.5 × 10⁻⁴s⁻¹ (t_1/2 = 26 min₎ in FBH

2. The use of lower temperature (4 °C) for the determination of f_u,brain in this study is not successful due to the instability of the compounds during longer equilibration times required at lower temperatures.

3. The f_u,brain values for a set of 15 CNS drugs determined in FBH and IBH-5 using HT-dialysis were similar and are consistent with the literature values. The use of IBH-5 led to the determination of f_u,brain for unstable compounds that could not be determined by other methods.

4. The use of IBH-5 is an easy and convenient method to determine the f_u,brain of unstable compounds in FBH during drug discovery and development.

Keywords:

• Fraction unbound
• brain homogenate
• equilibrium dialysis
• inactivated brain homogenate
• unstable

Acknowledgements

We wish to acknowledge the support received from Venkat Jasti, Chairman & CEO of Suven Life Sciences Ltd, Hyderabad, India.

Disclosure statement

All authors are employees of Suven Life Sciences. The authors alone are responsible for the content and writing of this manuscript.