OR12-04 Clofutriben, an 11beta-Hydroxysteroid Dehydrogenase Type 1 Inhibitor, vs Placebo in a Phase II Trial for ACTH-dependent Cushing’s Syndrome (RESCUE)

Abstract Disclosure: M. Fleseriu: None. C.P. Badiu: None. I. Bancos: None. E.B. Geer: None. M. Orbetzova: None. J.M. Silverstein: None. I. Uzunova: None. K.C. Yuen: None. T.K. Marmon: None. D.A. Katz: None. F.S. Czerwiec: None. Introduction: 11β-hydroxysteroid dehydrogenase type 1 (HSD-1) regulates exposures of intracellular receptors to active glucocorticoids. HSD-1 deficiency suppresses a Cushing syndrome (CS) phenotype despite presence of hypercortisolism.1-3 Treatment with clofutriben (C), a potent and specific inhibitor of HSD-1, might improve CS comorbidities by decreasing intracellular cortisol. Methods: Seventeen adults with CS (16 pituitary, 1 ectopic), and type 2 diabetes (T2D), impaired glucose tolerance (IGT), hypertension (HTN), hyperlipidemia, or osteopenia were randomized to a total of 12 weeks of oral C 6mg/d and 12 weeks of matching placebo (P) in 2 blinded sequences (PCCP, CCPP; “P” or “C” representing 6-week periods). Patients were offered open-label C treatment on completion. Primary endpoint was urinary ratio of cortisol and cortisone metabolites at Week 6 (hepatocellular HSD-1 activity biomarker). Key exploratory endpoints (and applicable population) at Week 6 were OGTT-AUCglucose decrease 25% (IGT/T2D), HbA1c decrease ≥ 0.5% (T2D), systolic blood pressure decrease ≥ 5mmHg or decreased treatment (HTN), and normalization of urinary free cortisol (baseline >1.5xULN). Results: Mean baseline HSD-1 ratio was 1.95 +/- 0.171. At Week 6, mean ratio was 0.21 +/- 0.091 with C and 2.01 +/- 0.263 with P. More patients responded at Week 6 to C on OGTT-AUCglucose (4/8 v 0/5), HbA1c (4/5 v 0/4), systolic blood pressure (5/7 v 2/4), and urinary free cortisol (3/8 v 0/6). Concomitant medications for T2D were reduced in 4 C-treated but increased in 2 P-treated patients. For HTN there were also 4 reductions for C-treated and 1 increase for P-treated patients. One patient succumbed to ectopic Cushing’s due to cervical carcinoma after discontinuing the trial. Four patients discontinued for reasons other than an adverse event (AE). One serious AE of vomiting (possible glucocorticoid withdrawal syndrome per investigator) led to temporary drug interruption. Common AEs (≥ 3 patients) included Arthralgia, Fatigue, Headache, and Nausea, but only Headache was more common in C during the P-controlled period. There was no evidence of clinical or biochemical (defined by low morning plasma cortisol) adrenal insufficiency. All 13 patients who completed elected to enter the open-label extension (current treatment duration 3-15 months). Conclusions: Clofutriben decreased hepatic HSD-1 activity adequately to confer clinical benefit while maintaining safety and overall tolerability. These limited data support clofutriben’s potential for clinical improvement without adrenal insufficiency. References: 1Tomlinson JW 2002; 2Arai H 2008; 3Weber RJ 2024 Presentation: Sunday, July 13, 2025