Purpose: Ischemia-reperfusion injury (IRI) is the strongest non-HLA factor that augments allogenicity of transplanted organs. Damage subsequent to IRI is critically linked to an abundance of reactive oxygen species (ROS), including H²0² that initiates inflammation and significantly contributes to allograft loss. Antioxidant Polymer Prodrugs, or APPs™, are potent, site-specific, self-limiting therapeutics that mitigate inflammation by reducing localized oxidative stress. APPs are innovative, highly effective, and safe antioxidative and anti-inflammatory therapies. Here, we show that APP-103 is able to mitigate IRI incurred during transplant surgery by reducing inflammation and improving graft function.
Methods: Lew kidneys were stored at 4℃ after procurement. Recipients received APP-103 (i.v./15mg/Kg) or vehicle (PBS); time for anastomosis was 25±5 minutes. Kidney function was assessed by serum creatinine (SCrea) measured at days 1 and 7 after transplantation. Local inflammation was determined by histology and qPCR for pro-and anti-inflammatory cytokines. Dosing at -1 and +2hrs after transplant was based on pharmacokinetic studies that revealed a 3-hr half-life for APP-103.
Results: APP-103 ameliorated IRI in prior studies of warm ischemia (kidney, heart and limb injury). Here, we demonstrate that APP-103 restores graft function following renal transplantation in syngeneic rat models by early mitigation of inflammatory responses. Recipients treated with APP-103 had 40% improved graft function (SCrea at days 1 and 7). Pathological analysis confirmed a significant reduction in interstitial fibrosis and tubular atrophy on POD days 1 and 7. Extended cold ischemia conditions were also mitigated by APP-103 with >50% SCrea reduction. Treatment with APP-103 resulted in reduced intragraft mRNA levels of the pro-inflammatory cytokines TNF-a and IL-6, inhibition of T cell proliferation cytokine IL-2, and a significant increase of the anti-inflammatory cytokine IL-10.Of further clinical relevance, APP-103 had no associated toxicity at the highest administrable dose. Flow cytometry revealed a significant decrease in surface expression of activation and maturation markers including CD40, CD80, and CD86 on DCs treated with APP-103 during stimulation with LPS. Moreover, flow cytometry indicated that frequencies of CD4⁺ and CD8⁺ IFNγ⁺ cells were significantly reduced when DCs were cocultivated in presence of APP-103.
Conclusion: APP-103 is a novel and safe therapeutic that targets on-site ROS showing impressive preservation of graft structure and function while dampening the initial inflammatory response linked to IRI.