Endocrine Abstracts

Introduction: Osilodrostat and Metyrapone are two CYP11B1 inhibitors used for the treatment of patients with Cushing syndrome. Despite their common suspected mechanism of action, the comparison of serum steroid profiles determined in HPLC-MS/MS in patients treated by either Osilodrostat or Metyrapone for an ACTH-dependent Cushing syndrome identified higher levels of 11-deoxycortisol and androgens in patients treated by Metyrapone than in those treated by Osilodrostat (F. Bonnet-Serrano and al., EJE, 2022). This suggested a potential inhibitory effect of Osilodrostat on other steroidogenic enzymes than CYP11B1. The objective of this study was to understand the mechanisms underlying the differences observed in treated patients in clinical routine by comparing the effect of both drugs on the steroid secretion profile of adrenocortical carcinoma cells in vitro, exposed to either Osilodrostat or Metyrapone.

Methods: H295R cells were incubated for 72 hours with five different concentrations of Osilodrostat or Metyrapone (0.05 µM, 0.1 µM, 0.5 µM, 1 µM and 5 µM). A profile of ten steroids was measured in the supernatant using HPLC-MS/MS analysis. Cell viability after drug exposure was evaluated by Crystal Violet assay.

Results: Half-decrease in cortisol and corticosterone levels was observed with only 0.05 µM of Osilodrostat (from 270 to 114 nmol/l and from 12.9 to 4.0 nmol/l, respectively) vs 0.5 µM of Metyrapone (from 267 to 118 nmol/l and from 11.9 to 5.6 nmol/l, respectively). These inhibitions also induced an increase in upstream steroids, 11-deoxycortisol and 11-deoxycorticosterone. Thus, Osilodrostat had a higher inhibitory effect on CYP11B1 and CYP11B2 than Metyrapone, as suggested by the higher 11-deoxycortisol/cortisol and 11-deoxycorticosterone/corticosterone ratios, respectively. Androstenedione levels showed a slight increase ≤20% with Osilodrostat while no variation was observed with Metyrapone. The same experiment and analysis will be performed using different concentrations and exposure durations to better characterize the effect of both drugs on steroid precursors and androgens pathway.

Conclusion: Osilodrostat induced a stronger inhibition of CYP11B1 and CYP11B2 activities than Metyrapone in H295R cells, resulting in a higher decrease in cortisol and corticosterone levels. The comparison of the steroid profile and the expression of steroidogenic enzymes in basal and treated conditions should also give us interesting insights in the action of these drugs on adrenocortical cells. This study would therefore, help to better understand the molecular cause of the adverse effect observed in treated patients, especially hyperandrogenism.