Endocrine Abstracts

Introduction: The steroidogenesis inhibitors ketoconazole and metyrapone are frequently used for treatment of Cushing’s syndrome, but can cause side effects. LCI699 is a known 11β-hydroxylase inhibitor, but effects on other steroidogenic enzymes are unknown. We aimed to compare effects of LCI699, ketoconazole, and metyrapone in vitro.

Methods: HAC-15 cells, with or without 10 nM ACTH, and three primary human adrenocortical adenoma cultures were incubated with LCI699, ketoconazole, or metyrapone (3 days; 0.01–5 μM). Cortisol was measured in the supernatant using a chemiluminescence immunoassay system (Immulite 2000Xi), corrected for cell amount. Steroid profiling was carried out in HAC-15 control and 5 μM treated cells by liquid chromatography/mass spectrometry (LC-MS/MS).

Results: LCI699 inhibited cortisol production at significantly lower concentrations (EC₅₀: 0.038 μM; 95% CI 0.031–0.048) than ketoconazole (0.764 μM; 0.535–1.092, P<0.0001), and metyrapone (0.084 μM; 0.0602–0.117, P<0.0001). Under ACTH stimulation (mean cortisol increase 37.4±1.98%, P<0.0001), sensitivity only changed for LCI699 (0.056 μM; 0.046–0.070, P<0.05 vs basal EC₅₀). Treatment did not affect cell number. For three primary cultures, the cortisol EC₅₀ of LCI699 (mean 0.050 μM) was significantly lower compared to that of ketoconazole (mean 0.984 μM; P<0.05). LCI699 strongly suppressed corticosterone and cortisol (91%, 87%, resp.; both P<0.001), and modestly suppressed androstenedione (38%), DHEA (38%), DHEAS (33%), testosterone (21%), and 17-hydroxyprogesterone (9.0%) production by HAC-15 cells (P<0.05). Progesterone increased by 70% under LCI699 treatment, while 11-deoxycortisol remained unchanged. The same trend was seen for metyrapone. Ketoconazole strongly inhibited concentrations of all steroids (mean 90%, P<0.001), except progesterone, which increased (644%, P<0.001).

Conclusion: LCI699 is a potent inhibitor of basal- and ACTH-stimulated cortisol production in adrenocortical tumor cells, and in these conditions seems to block 11β-hydroxylase (CYP11B1), and to a lesser extent 17,20-lyase activity. Besides, the absence of strong accumulation of steroid precursors might indicate an inhibition proximal of 3β-HSD.