Endocrine Abstracts

Background: HSD-1, an intracellular enzyme, converts cortisone to cortisol in tissues where cortisol excess is associated with morbidity including liver, adipose, bone, brain, muscle, skin, and eye. SPI-62 is a potent and specific HSD-1 inhibitor in development for treatment of Cushing’s syndrome and autonomous cortisol secretion, and as adjunctive therapy to prednisolone in polymyalgia rheumatica. In Phase 1 clinical trials SPI-62 was generally well tolerated and associated with maximal liver and brain HSD-1 inhibition. SPI-62 decreased urinary cortisol metabolites indicating a similar decrease of hepatocellular cortisol in this important target tissue. After a corresponding transient decrease, circulating cortisol homeostasis was restored by ACTH increase which also resulted in a moderate adrenal androgen increase. SPI-62’s effects on androgens did not result in adverse effects. Urinary free cortisol was unaffected. The RESCUE trial will assess SPI-62 safety and efficacy in patients with a dysregulated HPA axis, ie., ACTH-dependent Cushing’s syndrome.

Methods: In this randomized, placebo-controlled, crossover, multinational, Phase 2 clinical trial, adult patients (n=26) with ACTH-dependent Cushing’s syndrome with active and consistently elevated urinary free cortisol (UFC) will be randomized to receive SPI-62 and placebo for 12 weeks each. A diagnosis of an inadequately treated pituitary adenoma (Cushing’s disease) or ectopic ACTH or CRH producing tumor based on established criteria is required. Evidence of Cushing’s associated morbidities including at least 2 of A) insulin-resistance/type-2 diabetes mellitus, B) dyslipidemia, C) hypertension, or D) osteopenia is required. Subjects must not have had recent Cushing’s surgical, radiation other approved or experimental medical therapies for cortisol excess. Medical conditions or treatments likely to interfere with study assessments or subject safety are also excluded. The primary outcome is pharmacological suppression of the urinary ratio of hepatic 5- and 3-steroid reductase metabolites of cortisol and cortisone (tetrahydrocortisol+allotetrahydrocortisol)/tetrahydrocortisone). Safety is assessed by adverse events, vital signs, ECG, and clinical laboratory analyses including effects on HPA/HPG axis biomarkers. Efficacy is assessed by reduction of Cushing’s features and morbidities of hyperglycemia, dyslipidemia, adiposity, hepatic steatosis, hypertension, glaucoma, osteopenia, muscle strength, cognition, sleep, and mood. Assessments include tumor-imaging by MRI, ocular tonometry, timed up-and-go and hand-grip strength tests, dual-energy x-ray absorptiometry, oral glucose tolerance, continuous glucose monitoring, and ambulatory blood pressure monitoring.

Results: This trial is ongoing; results are pending.

Discussion: This Phase 2 explores SPI-62 safety, HSD-1 inhibition, effects on HPA/HPG axes, and clinical effects in patients with ACTH-dependent Cushing’s syndrome.