OR25-02 A Phase 3 Study of a Modified-Release Hydrocortisone in the Treatment of Congenital Adrenal Hyperplasia

Background: Patients with congenital adrenal hyperplasia (CAH) due to classic 21-hydroxylase deficiency have poor health outcomes related to inadequate glucocorticoid (GC) replacement. We compared disease control of adults with classic CAH treated with a modified release hydrocortisone (MRHC), which replicates physiological diurnal cortisol secretion, versus standard GC therapy. Methods: 6 month, open label, study in 122 patients randomised either to treatment with MRHC (Chronocort®, Diurnal Ltd, Cardiff, UK) twice daily at ~ 0700h & ~2300h, or to remain on their standard GC regimen (hydrocortisone, prednisolone, prednisone, dexamethasone). Patients had 24-hr profiling of serum 17-hydroxyprogesterone (17-OHP) at baseline and for dose titration at 4 and 12 weeks. The primary efficacy endpoint was the change from baseline to 24 weeks in the natural logarithm of the mean of the 24-hr standard deviation score (SDS) profile for 17-OHP. Results: Both groups achieved improved hormonal control at 24 weeks. The mean 24-hour 17-OHP SDS was significantly lower on MRHC compared to standard GC at 4 weeks (p = 0.0074) and 12 weeks (p = 0.019), but not at 24 weeks. In post-hoc analyses at 24 weeks, MRHC treatment showed a greater reduction in 17-OHP SDS compared to standard GC in the morning, 0700-1500h (p = 0.0442) and a greater reduction in log transformed 17-OHP 24 hour AUC (p=0.0251). Defining a morning 17-OHP <1200ng/dl (<36 nmol/L) as good control, for patients not controlled at baseline 85% were well controlled at 24 weeks with MHRC versus 50% on standard GC. For patients controlled at baseline 100% were controlled at 24 weeks on MHRC versus 84% with standard GC (p = 0.0018). The variability of 17-OHP over 24 hours was significantly reduced in the MRHC group compared to standard GC: the ratio of amplitude at 24 weeks divided by amplitude at baseline was for MRHC, 0.361 [95% CI: 0.235, 0.651], and standard GC, 0.917 [0.773, 1.366]; (p = 0.0001).There were no adrenal crises on MRHC and fewer stress doses despite similar incidence of inter-current illness to the standard GC group which had 3 adrenal crises. MRHC was associated with patient reported benefit including restoration of menstruation in 4 patients on MRHC and 1 on standard GC and two partner pregnancies in patients on MRHC and none on standard GC. Discussion: This is the largest randomised controlled trial of GC treatment in CAH and showed that intensification of therapy could improve control of the androgen-precursor, 17-OHP, and that this hormonal control was superior in the morning with MRHC. MRHC reduced the fluctuations in 17-OHP such that in the majority of patients the 17-OHP profile was within the reference range throughout 24 hours, providing consistent and optimal disease control. Conclusion: Diurnal cortisol replacement with a MRHC improves the biochemical control of classic CAH with a twice-daily therapeutic regimen.