title: Changes in plasma ACTH levels and corticotroph tumor size in patients with Cushing's disease during long-term treatment with the glucocorticoid receptor antagonist mifepristone.
abstract: BACKGROUND
  Pituitary effects of long-term therapy with mifepristone, a glucocorticoid receptor antagonist, in Cushing's disease (CD) patients are not well understood.
  
  
  OBJECTIVE
  Our objective was to report changes in ACTH and pituitary magnetic resonance imaging (MRI) findings during long-term use of mifepristone in CD patients.
  
  
  METHODS
  The Study of the Efficacy and Safety of Mifepristone in the Treatment of Endogenous Cushing's Syndrome (SEISMIC) was a 24-week, open-label study of mifepristone, and its long-term extension (LTE) is a multicenter U.S. study.
  
  
  METHODS
  Forty-three CD patients (mean age 45.3 years) were enrolled in SEISMIC with 27 continuing into the LTE study.
  
  
  METHODS
  Mifepristone (300-1200 mg) was administered once daily.
  
  
  METHODS
  ACTH and pituitary MRI were assessed at baseline and at regular intervals during treatment.
  
  
  RESULTS
  A ≥2-fold increase in ACTH was observed in 72% of patients treated for a median duration of 11.3 months. The mean peak increase in ACTH was 2.76 ± 1.65-fold during SEISMIC, and mean ACTH concentrations remained stable during the LTE. ACTH was directly correlated with mifepristone dose and declined to near baseline levels after mifepristone discontinuation. Tumor regressed in 2 patients and progressed in 3 patients with macroadenomas. An additional microadenoma was identified after 25 months of treatment after a baseline tumor-negative MRI.
  
  
  CONCLUSIONS
  In the largest prospective study to date, long-term mifepristone treatment increased ACTH in approximately two-thirds of patients with CD. ACTH elevations were observed within the first few weeks of treatment, were dose-dependent, and generally remained stable over time. Corticotroph tumor progression and regression may occur over time, but patients may have significant increases in ACTH levels without evidence of tumor growth.
authors.affiliation: Oregon Health & Science University (M.F.), Portland, Oregon 97239; Medical College of Wisconsin (J.W.F.), Milwaukee, Wisconsin 53051; University of Mississippi Medical Center (C.A.K.), Jackson, Mississippi 39216; University of Erlangen-Nürnberg (S.-M.S., M.B.), 91054 Erlangen, Germany; and Corcept Therapeutics (C.G.), Menlo Park, California 94025.
authors.forename: Maria
authors.initials: M
authors.lastname: Fleseriu
authors.forename: James W
authors.initials: JW
authors.lastname: Findling
authors.forename: Christian A
authors.initials: CA
authors.lastname: Koch
authors.forename: Sven-Martin
authors.initials: SM
authors.lastname: Schlaffer
authors.forename: Michael
authors.initials: M
authors.lastname: Buchfelder
authors.forename: Coleman
authors.initials: C
authors.lastname: Gross
mesh_terms: D000236:Adenoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000328:Adult; D052680:Corticotrophs / Q000378:metabolism / Q000473:pathology; D005260:Female; D006727:Hormone Antagonists / Q000008:administration & dosage / Q000009:adverse effects; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015735:Mifepristone / Q000008:administration & dosage* / Q000009:adverse effects; D047748:Pituitary ACTH Hypersecretion / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010911:Pituitary Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D011446:Prospective Studies; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors*
chemical_list: D006727:Hormone Antagonists; D011965:Receptors, Glucocorticoid; D015735:Mifepristone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone