Introduction Cyclosporine A (CyA) is a powerful immunosuppressive agent and has been used off label for steroid-dependent or steroid-refractory ulcerative colitis. However, systemic exposure results in a number of side effects. A novel advanced oral drug delivery system, SmPill®, has been developed to permit targeted release of CyA directly into the colon tissue with limited systemic exposure.
Aims/Background The objective was to compare SmPill®-CyA activity in the IL10 knock-out mouse model of Crohn's colitis against the marketed Neoral® (po) and Sandimmun® (ip).
Method Mice were treated for 42 days, received the equivalent of 15 mg/kg/day CyA as well as untreated and SmPill® placebo. A secondary objective was to measure systemic pro-inflammatory cytokine activity in isolated spleen cells.
Results General Mouse Health:
The SmPill®-CyA group were significantly heavier than mice in all other groups on Day 42.
The SmPill®-CyA group had the lowest Disease Activity Index scores relative to the other groups.
Colon Tissue Inflammatory Biomarkers:
The untreated mice had the highest Serum Amyloid A levels (SAA), with the lowest levels seen with those treated with SmPill®-CyA (p<0.001) followed by Sandimmun® (i.p) (p<0.01) treated mice.
Sandimmun (i.p) and SmPill®-CyA groups had significantly lower (P<0.01) histology scores relative to Neoral®. Neoral® (po) had the greatest relative score.
The highest levels of Myeloperoxidase (MPO) activity were seen in the untreated and placebo mice. There was statistically lower MPO activity in both the SmPill®-CyA and Sandimmune® (i.p.) groups relative to untreated mice (p<0.05).
Similarly to a reduction in MPO activity, the SmPill®-CyA groups also had reduced IL-1α, IL-17 and TNFα pro-inflammatory cytokine levels (p<0.05) in colon tissue at Day 42.
Systemic Tissue Inflammatory Biomarkers:
In a measure of systemic CyA activity, the activity of a number of pro-inflammatory cytokines in activated isolated spleen cells was measured. The Sandimmune® (i.p) treated mice had significantly reduced production of TNF-α (p<0.01) and IL-17 (p<0.05) relative to cells from the untreated and placebo treated mice. In mice treated with SmPill®-CyA the reduction in TNF-α and IL-17 release by cells was non-significant. The pro-inflammatory cytokine expression levels for Neoral® was between that of Sandimmune® and SmPill®-CyA.
Conclusion The above study demonstrated that SmPill®-CyA conferred preferential local colonic efficacy with limited systemic activity, in effect, harnessing the local efficacy of CyA and reducing systemic side effect risks. A SmPill®-CyA formulation, CyCol®, has progressed through human Phase I (PK) study in Canada and Phase IIb study in Ireland and the UK. A multi-centre Phase IIb study is being planned.
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