Corticotropin
Immune / Anti-InflammatoryAlso known as: ACTH, Acthar Gel, H.P. Acthar Gel, Adrenocorticotropic Hormone
Mechanism
ACTH (adrenocorticotropic hormone) — the 39-amino acid pituitary hormone that tells your adrenal glands to produce cortisol. But Acthar Gel does more than just raise cortisol levels: it also directly activates melanocortin receptors on immune cells, providing anti-inflammatory effects that are distinct from cortisol itself. FDA-approved for a surprisingly wide range of conditions including MS flares, infantile spasms, nephrotic syndrome, and rheumatic disorders.
Technical detail
Repository (long-acting) preparation of purified porcine ACTH (corticotropin) in gelatin for IM/SC injection. ACTH1-39 is a 39-amino acid linear peptide derived from POMC (pro-opiomelanocortin). Dual mechanism: (1) Endocrine: binds MC2R (melanocortin 2 receptor) on adrenal cortex zona fasciculata → cAMP/PKA → stimulates steroidogenesis (cortisol, corticosterone, aldosterone). This is the "expected" mechanism. (2) Direct immunomodulation: ACTH and its fragments bind MC1R, MC3R, MC4R, and MC5R on immune cells (macrophages, T cells, B cells). MC3R/MC5R activation on macrophages → NF-κB suppression, reduced TNF-α/IL-1β/IL-6 production, enhanced IL-10 (anti-inflammatory). This melanocortin-mediated immunomodulation is mechanistically distinct from glucocorticoid effects and explains clinical efficacy in conditions where prednisone alone is insufficient. Acthar Gel formulation: gelatin matrix provides sustained release over 24-72 hours from IM/SC depot. Dosing: 80 units IM/SC every 24-72 hours (varies by indication). FDA-approved indications: MS acute exacerbations, infantile spasms (first-line), nephrotic syndrome (idiopathic and lupus), rheumatic disorders (RA, psoriatic arthritis, ankylosing spondylitis), dermatomyositis/polymyositis, SLE, sarcoidosis, severe asthma, optic neuritis. Notably expensive: ~$40,000 per vial (significant controversy). Side effects: adrenal axis suppression, hyperglycemia, fluid retention, hypertension, immunosuppression (similar to exogenous glucocorticoids but also includes melanocortin-specific effects).
Effects
ENDOCRINE SYSTEM: Corticotropin (ACTH1-39) is the full-length adrenocorticotropic hormone. Acthar Gel is a highly purified porcine-derived ACTH formulation in a gelatin/phenol repository for prolonged release [FDA-approved]. PRIMARY MECHANISM (CORTISOL): Stimulates adrenal cortex via MC2R (melanocortin-2 receptor), driving cortisol synthesis and release — the traditional mechanism used to explain its clinical effects [pharmacological, clinical]. However, this mechanism alone does not explain Acthar's efficacy in conditions where exogenous corticosteroids are also available. SECOND MECHANISM (MELANOCORTIN ANTI-INFLAMMATORY): ACTH also activates MC1R, MC3R, MC4R, and MC5R — the broader melanocortin receptor family expressed on immune cells, endothelial cells, and in the CNS [in vitro, animal]. MC1R activation on macrophages and T-cells directly suppresses NF-κB signaling, reducing IL-1β, TNF-α, and IL-6 production independent of cortisol [in vitro, animal]. MC3R activation promotes anti-inflammatory macrophage polarization (M2 phenotype) and enhances regulatory T-cell function [animal]. This dual mechanism — cortisol-dependent + cortisol-independent melanocortin anti-inflammatory — may explain why Acthar is effective in some patients who fail exogenous corticosteroids [mechanistic hypothesis, clinical observation]. NEUROLOGICAL (MS EXACERBATIONS): Reduces inflammation and edema in acute MS relapses via both cortisol and direct melanocortin effects on CNS-resident immune cells (microglia express melanocortin receptors) [RCT, clinical practice]. FDA-approved for MS exacerbations since 1978. PEDIATRIC (INFANTILE SPASMS): First-line treatment for infantile spasms (West syndrome) — suppresses the hypsarrhythmia EEG pattern and clinical spasms, potentially via melanocortin effects on brain development and neuroinflammation [RCT — Baram et al., 1996]. NEPHROTIC SYNDROME: Effective in inducing remission in nephrotic syndrome (both idiopathic and membranous), including patients who fail standard immunosuppressives — MC1R expression on podocytes may explain direct renal effects independent of systemic immunosuppression [RCT — Hladunewich et al., 2014, Bomback et al., 2012]. RHEUMATOLOGICAL: Approved for various rheumatic conditions including rheumatoid arthritis, lupus flares, and gout — though rarely used first-line due to cost.
Practitioner Guide
ADMINISTRATION: Subcutaneous or intramuscular injection. Acthar Gel is a repository formulation providing sustained ACTH release over 24-48 hours per injection. DOSING — MS EXACERBATIONS: 80-120 units IM/SC daily for 2-3 weeks, then taper over 1-2 weeks. Alternative: 80 units q48-72h for milder exacerbations. Used as alternative to IV methylprednisolone 1g/day x 3-5 days — particularly for patients who fail IV steroids, cannot tolerate IV steroids, or lack IV access. DOSING — INFANTILE SPASMS: 150 IU/m² IM twice daily for 2 weeks. High-dose short-course protocol (UKISS trial protocol). If spasms resolve: taper over 2 weeks. If no response by 2 weeks: typically switch to vigabatrin. Pediatric neurology specialist management required. DOSING — NEPHROTIC SYNDROME: 80 units SC twice weekly for 6 months (protocolized in several studies). Some nephrologists use 80 units SC 2-3 times weekly. Monitor proteinuria monthly. DOSING — RHEUMATOLOGIC: 40-80 units SC/IM every 24-72 hours depending on indication and response. Gout flares: 25-40 units SC, may repeat in 24 hours. MONITORING: Blood glucose (ACTH stimulates cortisol → hyperglycemia), blood pressure, electrolytes (hypokalemia from mineralocorticoid effect), weight, mood/psychiatric symptoms. For infantile spasms: EEG monitoring for hypsarrhythmia resolution. For nephrotic syndrome: spot urine protein/creatinine ratio monthly. SIDE EFFECTS: Identical to exogenous corticosteroids (because cortisol elevation is the primary mechanism) — hyperglycemia, hypertension, weight gain, mood changes, insomnia, infection risk, adrenal suppression with chronic use, osteoporosis, cataracts. Additionally: injection site reactions, fluid retention. THE PRICING CONTROVERSY: Acthar Gel costs approximately $40,000-50,000 per vial (5 mL, 80 units/mL). This extreme pricing has been the subject of congressional scrutiny, investigative journalism, and multiple lawsuits. The original Acthar formulation cost $40/vial in 2001 before being acquired by Questcor (later Mallinckrodt). The price has increased >10,000%. This has limited its use and generated significant controversy despite legitimate clinical utility in specific niches. PRACTICAL RECOMMENDATION: Reserve for patients who fail standard immunosuppressives or have specific indications where melanocortin effects may be superior (infantile spasms, refractory nephrotic syndrome, MS exacerbations failing IV steroids).
Research Summary
TIER 1: Baram et al., 1996 — RCT: ACTH vs. prednisone for infantile spasms, ACTH superior for cessation of spasms and resolution of hypsarrhythmia. UKISS trial — high-dose ACTH or vigabatrin for infantile spasms, ACTH better long-term outcomes (especially non-tuberous sclerosis patients). Hladunewich et al., 2014 and Bomback et al., 2012 — pilot studies showing Acthar efficacy in membranous nephropathy and refractory nephrotic syndrome. Rose et al., 1970 — early RCT establishing ACTH for MS exacerbations. FDA-approved for: MS exacerbations, infantile spasms, nephrotic syndrome, rheumatic disorders, and multiple other inflammatory conditions (broad label from original 1952 approval). TIER 2: Systematic reviews of ACTH vs. corticosteroids for infantile spasms (Cochrane — ACTH superior). Reviews of melanocortin receptor biology and the dual-mechanism hypothesis (Catania et al., 2004). Comparative effectiveness reviews of Acthar vs. IV methylprednisolone for MS relapses (equivalent or possibly superior in some patients). Nephrotic syndrome case series and pilot studies. Health economic analyses (universally critical of pricing). TIER 3: Rheumatology and nephrology case series. Expert opinion on appropriate use in refractory autoimmune conditions. Gout treatment case reports. International practice patterns (Acthar is primarily used in the US due to availability). KEY FINDINGS: Acthar Gel has legitimate clinical utility, particularly for infantile spasms (where it is standard of care), refractory nephrotic syndrome, and MS exacerbations. The dual-mechanism hypothesis (cortisol + melanocortin anti-inflammatory) is scientifically plausible and may explain efficacy in corticosteroid-refractory patients. The pricing controversy has overshadowed the science. GAPS: No large RCT comparing Acthar to IV steroids for MS in modern era. Melanocortin-specific effects vs. cortisol effects not clearly delineated in clinical trials. Optimal dosing for nephrotic syndrome not established. ACTIVE TRIALS: Studies in nephrotic syndrome, lupus, and rheumatoid arthritis. Mechanistic trials attempting to confirm melanocortin receptor engagement in patients.