Effect of Novel Biotherapeutic Elevating Angiopoietin 1 on Progression of Diabetic Nephropathy in Diabetic/Obese Mice.

Diabetic nephropathy is a leading cause of end-stage renal disease, characterized by endothelial dysfunction and a compromised glomerular permeability barrier. Dysregulation of the angiopoietin 1 (ANGPT1)/angiopoietin 2 (ANGPT2) signaling axis is implicated in disease progression. We recently described the discovery of an IgG antibody, O010, with therapeutic potential to elevate circulating endogenous ANGPT1, a tyrosine kinase with Ig and epidermal growth factor (EGF) homology domains-2 (TIE2) agonist. Studies are described that detail the effect of various ANGPT1-elevating strategies to limit progression of renal dysfunction in diabetic-obese (db/db) mice. Results demonstrate that adeno-associated virus- or DNA minicircle-directed overexpression of ANGPT1 elicits a reduction in albuminuria (56%-73%) and an improvement in histopathology score (18% reduction in glomerulosclerosis). An improved acetylcholine response in isolated aortic rings was also observed indicative of a benefit on vascular function. In separate pharmacokinetic studies, an efficacious dose of the ANGPT1 DNA minicircle increased circulating levels of the protein by >80%, resulting in a concomitant suppression of ANGPT2. At a dose of O010-producing maximal elevation of circulating ANGPT1 achievable with the molecule (60% increase), no suppression of ANGPT2 was observed in db/db mice, suggesting insufficient pathway engagement; no reduction in albuminuria or improvement in histopathological outcomes were observed. To pinpoint the mechanism resulting in lack of efficacy, we demonstrate, using confocal microscopy, an interference with TIE2 translocation to adherens junctions, resulting in a loss of protection against vascular permeability normally conferred by ANGPT1. Results demonstrated the essential importance of ANGPT1 to maintain the glomerular permeability barrier, and, due to interference of O010 with this process, led to the discontinuation of the molecule for clinical development. SIGNIFICANCE STATEMENT: This body of original research demonstrates that elevation of systemic angiopoietin 1 (ANGPT1) is protective against diabetic nephropathy. However, using a novel biotherapeutic approach to elevate systemic ANGPT1 renoprotection was not observed; we demonstrate that protection was lost due to interference of the therapeutic with ANGPT1/ tyrosine kinase with Ig and EGF homology domains-2 translocation to adherens junctions. Thus, the clinical development of the antibody was terminated.