Continuous inhibition of 11β-hydroxysteroid dehydrogenase type I in adipose tissue leads to tachyphylaxis in humans and rats but not in mice

Abstract

Background and purpose: 11β-hydroxysteroid dehydrogenase type I (11β-HSD1), a target for Type 2 diabetes mellitus, converts inactive glucocorticoids into bioactive forms, increasing tissue concentrations. We have compared the pharmacokinetic-pharmacodynamic (PK/PD) relationship of target inhibition after acute and repeat administration of inhibitors of 11β-HSD1 activity in human, rat and mouse adipose tissue (AT).

Experimental approach: Studies included abdominally obese human volunteers, rats and mice. Two specific 11β-HSD1 inhibitors (AZD8329 and COMPOUND-20) were administered as single oral doses or repeat daily doses for 7-9 days. 11β-HSD1 activity in AT was measured ex vivo by conversion of (3) H-cortisone to (3) H-cortisol.

Key results: In human and rat AT, inhibition of 11β-HSD1 activity was lost after repeat dosing of AZD8329, compared with acute administration. Similarly, in rat AT, there was loss of inhibition of 11β-HSD1 activity after repeat dosing with COMPOUND-20 with continuous drug cover, but effects were substantially reduced if a 'drug holiday' period was maintained daily. Inhibition of 11β-HSD1 activity was not lost in mouse AT after continuous cover with COMPOUND-20 for 7 days.

Conclusions and implications: Human and rat AT, but not mouse AT, exhibited tachyphylaxis for inhibition of 11β-HSD1 activity after repeat dosing. Translation of observed efficacy in murine disease models to human for 11β-HSD1 inhibitors may be misleading. Investigators of the effects of 11β-HSD1 inhibitors should confirm that desired levels of enzyme inhibition in AT can be maintained over time after repeat dosing and not rely on results following a single dose.

Trial registration: ClinicalTrials.gov NCT01207089.

© 2015 The British Pharmacological Society.

Figures

Figure 1

Comparison of the PK/PD relationship between ex vivo activity of the human 11β‐HSD1 enzyme in sub‐cutaneous AT biopsies (measured as the conversion of 3H‐cortisone to 3H‐cortisol) and free plasma concentrations of AZD8329 both after acute and repeat oral administration (n = 6 per dose level). A direct response (Emax) model was used to fit the PK/PD results. The observed results for day 1 and for day 9 are shown with the corresponding lines representing the model fit for each set of observations.

Figure 2

Meta‐analysis of multiple rat experiments to compare the PK/PD relationship between ex vivo activity of rat 11β‐HSD1 enzyme in epididymal AT (measured as conversion of 3H‐cortisone to 3H‐cortisol, normalized to vehicle treated rats) and free plasma concentrations of AZD8329 after acute and repeat oral administration. A direct response (Emax) model was used to fit the PK/PD data. The observed results for acute (n = 109) and repeat dosing for 7 days (n = 58) are shown with the corresponding lines representing the model fit for each set of observations.

Figure 3

Rat study B with AZD8329: (A) Box and whisker plot of ex vivo activity of rat 11β‐HSD1 enzyme in epididymal AT (measured conversion of 3H‐cortisone to 3H‐cortisol) after acute and repeat oral administration, per treatment group of AZD8329 (n = 12), comparison of the vehicle (n = 8) versus the treated groups (box and whisker plot shows the median (central line), the upper and lower quartiles (top and bottom of the box) and the range of the data (whiskers). If there are data points more than 1.5× the interquartile range (IQR) above the upper quartile (or below the lower quartile), then these points are singled out and presented separately. *** P < 0.001, significantly different from vehicle. (B) Comparison of the PK/PD relationship between rat 11β‐HSD1 enzyme activity and free plasma concentrations of AZD8329 after acute and repeated (7 days) oral administration in rats.. (C) Treatment groups statistical comparison of the ex vivo activity of the rat 11β‐HSD1 enzyme in epididymal AT. The confidence intervals are 95% (with Sidak's multiple comparison adjustment) so statistical significance was inferred if the 95% confidence interval did not span zero. **P< ,0.01. Rat experiment with COMPOUND‐20: (D) Box and whisker plot of ex vivo activity of rat 11β‐HSD1 enzyme in epididymal AT (measured conversion of 3H‐cortisone to 3H‐cortisol) after acute and repeat oral administration (u.i.d. and b.i.d.), per treatment group of COMPOUND‐20 (n = 12), comparison of the vehicle (n = 8) versus the treated groups. (E) Comparison of the PK/PD relationship between rat 11β‐HSD1 enzyme activity and free plasma concentrations of COMPOUND‐20 after acute and repeat (b.i.d. or u.i.d. for 7 days) oral administration in rats. (F) Treatment groups statistical comparison of the ex vivo activity of the rat 11β‐HSD1 enzyme in epididymal AT. The confidence intervals are 95% (with Sidak's multiple comparison adjustment). *P < 0.05, **P < 0.01. (G) Free plasma concentrations (+SD) of COMPOUND‐20 in rats following a daily dose of COMPOUND‐20 at either 20 mg · kg−1 u.i.d. or 60 mg · kg−1 b.i.d.. Horizontal dotted line indicates ‘efficacious’ concentrations based on acute IC50 for the inhibition of rat 11β‐HSD1 activity in the adipose tissue. Results shown are measured plasma concentrations of COMPOUND‐20 for the first 12 h on day 6. The second 12 h are simulated based on results from the first 12 h.

Figure 4

Mouse experiment with COMPOUND‐20: (A) Box and whisker plot of ex vivo activity of mouse 11β‐HSD1 enzyme in epididymal AT (measured conversion of 3H‐cortisone to 3H‐cortisol) after acute and repeat oral administration, per treatment group of COMPOUND‐20 (n = 13), comparison of the vehicle (n = 5) versus the treated groups (see legend of Figure 3 for description of box and whiskers plot). ***P < 0.001, significantly different from vehicle . (B) Comparison of the PK/PD relationship between mouse 11β‐HSD1 enzyme activity and free plasma concentrations of COMPOUND‐20 after acute and repeat (b.i.d. or u.i.d. for 7 days) oral administration in mice. (C) Treatment groups statistical comparison of the ex vivo activity of the mouse 11β‐HSD1 enzyme in epididymal AT. The confidence intervals are 95% (with Sidak's multiple comparison adjustment) so statistical significance was inferred if the 95% confidence interval did not span zero. *P < 0.05.