Ab0082 reduced Steroidogenic Activity of Repository Corticotropin Injection (Rci) Induces a Distinct Cytokine Response Following T Cell Activation in Vivo

Abstract

Background:Melanocortin receptor agonists, such as αMSH have been shown to reduce inflammation in preclinical models, suppressing the production of proinflammatory cytokines. Natural and synthetic ACTH analogues remain linked to the induction of corticosteroids as their primary mechanism of action, leading to the anti-inflammatory and immunosuppressive responses. Repository Corticotropin Injection (RCI) is a complex mixture containing purified porcine pituitary ACTH-analogue, and is an FDA-approved treatment for several inflammatory diseases. RCI has been shown to be effective in steroid-refractory autoimmune disease.Objectives:We hypothesize that Acthar has an immune regulatory response distinct from synthetic ACTH and steroids. These studies sought to explore the differences between RCI and synthetic ACTH on corticosterone levels in rats and cytokine production in a murine T cell activation model.Methods:RCI (10, 40, or 400 IU/kg) or ACTH (0.6, 1.2, or 2.4 mg/kg) was administered to Sprague Dawely rats, plasma samples collected and analyzed for corticosterone. To determine the effect on T cell cytokine production, Balb/C mice were treated with RCI (10, 40, and 400 U/kg), ACTH (0.6, 1.2, or 2.4 mg/kg) or prednisolone 1 hour prior to the administration of an anti-CD3. Two hours after antibody administration, plasma cytokines were measured using Meso Scale multiplex ELISA.Results:RCI and ACTH peak corticosterone and area under the curve (AUC) were evaluated. RCI-induced corticosterone rapidly peaked between 2 -8 hrs. and was dependent on the dose. ACTH displays a delay in the peak time (8-24 hours) and was not dose dependent. When compared to the high dose ACTH, RCI reduced the AUC by 50.0 ± 2.6%, 45.5 ± 5.6% and 27.3 ± 12.5% respectively for 10, 40, and 400 IU/kg. However, there was no significant reduction between any of the ACTH doses tested.To further explore functional differences between RCI and ACTH, we examined the effects on T cell activation. In vivo T cell activation with the anti-CD3 antibody (clone, 145-2C11) increased several cytokines, including IL-2, IL-6, IL-10, and IFNγ. Treatment with RCI, ACTH, or prednisolone significantly reduced the production of IL-2, IL-4, IFNγ, and TNFα. Interestingly, RCI showed an inverse dose-response on the production of IL-6 and IL-10. RCI inhibited the production of IL-6 at 74.7 ± 4.4% and 67.9 ± 8.5% and IL-10 at 39.1 ± 7.1% and 26.7 ± 9.3% for 10 and 40 IU/kg, respectively, whereas 400 IU/kg had no effect. ACTH inhibited the production of IL-6 at a similar level for all doses tested and had no effect on IL-10 production, whereas treatment with prednisolone inhibited all cytokines.Conclusion:These data show that RCI has a reduced steroidal response compare to synthetic ACTH. RCI has a direct and distinct immunomodulatory response on T cells unique from both synthetic ACTH and steroids. These characteristic effects suggest a mechanism of action for RCI that is steroid-independent and may help explain its benefit in steroid refractory syndromes.Disclosure of Interests...

Distinct binding and signaling activity of Acthar Gel compared to other melanocortin receptor agonists

“…Treatment with Acthar Gel has also been effective in patients with rheumatoid arthritis or glomerular diseases that have been resistant to corticosteroid treatment, further confirming a mechanism of action that is independent of cortisol production [48,49]. Thus, these data, in combination with preclinical and clinical studies [24][25][26]28,48,49], suggest that Acthar Gel may provide benefit in the treatment of inflammatory disease through mechanisms beyond the induction of steroids.…”

“…Taken together, the combined engagement profile of Acthar Gel at MC1R, MC3R, MC4R, and MC5R suggests a distinct direct immune cell effect beyond the indirect antiinflammatory effect from MC2R-dependent production of corticosteroids. Despite less sustained cortisol induction, Acthar Gel remains efficacious [48,49], suggesting direct interaction with immune cells to treat disease [24][25][26]. The mechanism of action of Acthar Gel is unique from that of pACTH 1-39 , ACTH 1-24 , N25D-ACTH 1-39 , and other MCR agonists, suggesting that its complex mixture of peptides interacts with MCRs differently than any single MCR agonist does.…”

“…Acthar V R Gel (repository corticotropin injection; Mallinckrodt Pharmaceuticals, Bedminster, NJ, USA) is a naturally sourced complex mixture of ACTH analogs and other pituitary peptides [23]. Acthar Gel engages the MCRs expressed on immune cells and other tissues throughout the body and is thought to produce both indirect anti-inflammatory and direct immunomodulatory effects [24][25][26]. Acthar Gel is approved for several indications, including treatment of acute exacerbations of multiple sclerosis in adults, as a monotherapy for infantile spasms, and for the induction of diuresis or a remission of proteinuria in nephrotic syndrome without uremia of the idiopathic type or due to lupus erythematosus [23].…”

“…The anti-inflammatory effects of Acthar Gel originally were thought to be mediated indirectly through corticosteroid production following the engagement of MC2R-expressing cells in the adrenal cortex [32]; however, recent studies challenge that hypothesis and suggest that Acthar Gel directly modulates the activity of MC1R, MC3R, MC4R, and MC5R on immune cells and various other cell types [24,25].…”

Patient Characteristics and Indicators of Treatment Initiation with Repository Corticotropin Injection in Patients with Rheumatoid Arthritis: A Claims Database Analysis

“…Evaluation of clinical characteristics, treatment patterns, and HCRU before initiation of RCI, versus initiation or continuation of ts/ bDMARD therapy, is critical in understanding differences in patients with uncontrolled RA requiring alternatives to standard therapy and in generating an accurate patient profile for RCI initiators. Repository corticotropin injection is a complex mixture of adrenocorticotropic hormone analogs and other pituitary peptides that activates all five melanocortin receptors (MC1R-MC5R), inducing steroidogenesis, antiinflammatory effects, and direct immunomodulation of B and T cells [28][29][30][31][32]. Recently, Montero-Melendez et al demonstrated activation of MC1R-induced cellular senescence in both synovial and dermal fibroblasts in a mouse model of inflammatory arthritis [33].…”