Pharmacokinetics and Pharmacodynamics of Repository Corticotropin Injection Compared With Synthetic ACTH(1‐24) Depot and Methylprednisolone in Healthy Subjects

Repository corticotropin injection (RCI; Acthar Gel) is a naturally sourced complex mixture of adrenocorticotropic hormone (ACTH) analogs and other pituitary peptides. This phase 1, single‐center, open‐label, randomized parallel study directly compared the pharmacokinetics and pharmacodynamics of RCI and synthetic ACTH(1‐24) depot. Methylprednisolone was included to estimate the steroidogenic exposure of RCI and synthetic ACTH(1‐24) depot when used to treat nephrotic syndrome. A total of 48 healthy subjects aged 18 to 50 years were randomly assigned 1:1:1 to RCI (80 IU subcutaneously twice weekly on study days 1 and 4), synthetic ACTH(1‐24) depot (1 mg subcutaneously twice weekly on study days 1 and 4), or methylprednisolone (32 mg orally once daily on study days 1 through 6). After 2 doses, RCI induced about 5‐fold lower free cortisol exposure and an estimated 4‐fold lower steroidogenic exposure than synthetic ACTH(1‐24) depot. The lower endogenous cortisol response of RCI was achieved despite higher observed mean plasma concentrations of N25‐deamidated porcine ACTH(1‐39) (the pharmacokinetic marker for RCI) than of ACTH(1‐24). The different pharmacodynamic properties demonstrated by RCI and synthetic ACTH(1‐24) depot in this study suggest that these products in the ACTH class are not interchangeable.