Context The causative link between circulating glucocorticoid excess and osteoporosis is well-established. The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which increases local cortisol production, is expressed in human osteoblasts and its activity increases with age. Objective We hypothesized that local 11β-HSD1 might mediate an age-related decrease in bone formation and that selective 11β-HSD1 inhibition may enhance bone formation. Methods A dual-center, phase II, randomized, double-blind, placebo-controlled trial of 90 days’ treatment with AZD4017 (a selective 11β-HSD1 inhibitor) was conducted in 55 postmenopausal women with osteopenia. Participants received 400 mg oral AZD4017 twice daily vs matched placebo over 90 days. The primary outcome measure was the impact on the bone formation marker osteocalcin. Secondary objectives included correlation with 11β-HSD1 activity. Results At 90 days, osteocalcin levels did not differ between treatment groups: active (mean 22.3 [SD 8.6] ng/mL, n = 22) and placebo (21.7 [SD 9.2] ng/mL, n = 24), with a baseline-adjusted treatment effect of 0.95 (95% CI: −2.69, 4.60). The results from the urinary [THF + alloTHF]/THE ratio (index of 11β-HSD1 activity) and the urinary cortisol/cortisone ratio (index of 11β-HSD2 activity) confirmed a > 90% inhibition of 11β-HSD1 but no change in activity of 11β-HSD2. Conclusion This trial demonstrates that AZD4017 selectively inhibits 11β-HSD1 activity in vivo in a safe and reversible manner. Following 90 days of treatment, there is no effect on bone formation, indicating that the relative impairment of bone mineral density in postmenopausal women is not mediated by local intracellular production of cortisol under normal physiological concentrations.
