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Abstract: FR-OR33

A ROBO2 Fusion Protein (PF-06730512) Traps SLIT Ligands and Therapeutically Ameliorates Podocyte Injury

Session Information

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Berasi, Stephen, Pfizer Inc, Cambridge, Massachusetts, United States
  • Buhlmann, Janet E., Pfizer Inc, Cambridge, Massachusetts, United States
  • Shamashkin, Michael, Pfizer Inc, Cambridge, Massachusetts, United States
  • Russo, Matthew V., Pfizer Inc, Cambridge, Massachusetts, United States
  • Yang, Hongying, Pfizer Inc, Cambridge, Massachusetts, United States
  • Knowlton, Kelly M., Pfizer Inc, Cambridge, Massachusetts, United States
  • Higginson-Scott, Nathan, Pfizer Inc, Cambridge, Massachusetts, United States
  • Lin, Hank, Pfizer Inc, Cambridge, Massachusetts, United States
  • Andresen, Catharine, Pfizer Inc, Cambridge, Massachusetts, United States
  • Jones, Rhys, Pfizer Inc, Cambridge, Massachusetts, United States
  • Fan, Xueping, Boston University Medical School, Boston, Massachusetts, United States
  • Kumar, Sudhir, Boston University Medical School, Boston, Massachusetts, United States
  • Sharma, Richa, Boston University Medical School, Boston, Massachusetts, United States
  • Pydi, Aneesha, Boston University Medical School, Boston, Massachusetts, United States
  • Salant, David J., Boston University Medical School, Boston, Massachusetts, United States
  • Lu, Weining, Boston University Medical School, Boston, Massachusetts, United States
Background

ROBO2/SLIT2 signaling negatively regulates nephrin-induced actin polymerization and destabilizes podocyte focal adhesions and attachment to the glomerular basement membrane (GBM) by inhibiting non-muscle myosin IIA. Mice lacking ROBO2 in podocytes are protected from podocyte injury. Based on these findings we hypothesized that blocking this pathway might have therapeutic potential in podocytopathies. Here we provide evidence to support that hypothesis from a case with a genetic defect in ROBO2 and a rodent model of podocyte injury.

Methods

We investigated a patient with a chromosomal translocation that disrupted the ROBO2 gene, produced transcripts encoding dominant negative proteins, and caused high-grade vesicoureteral reflux (VUR). We designed a novel therapeutic ROBO2 fusion protein (ROBO2-Fc, PF-06730512) that inhibits the ROBO2/SLIT2 pathway. In vivo efficacy of ROBO2-Fc was tested in the rat Passive Heymann Nephritis (PHN) model. We also studied the molecular and cellular functions of SLIT2 in kidney glomeruli.

Results

In contrast to most adults with long-standing VUR that develop focal and segmental glomerulosclerosis (FSGS) and proteinuria, the patient with a disrupted ROBO2 gene had stable renal function without proteinuria. In vitro, ROBO2-Fc bound to SLIT ligands with high affinity and dose-dependently inhibited SLIT binding to cell surface ROBO2, and it inhibited ROBO2-dependent cell migration ex vivo. ROBO2-Fc has a terminal half-life of about 5 days in rat and 8 days in monkey. Treatment with ROBO2-Fc reduced proteinuria, shortened podocyte foot process width, and increased slit-diaphragm density in the rat PHN model. Mechanistically, we found that SLIT2 is localized to the GBM and binds to COL4A3/laminin to inhibit podocyte adhesion.

Conclusion

We have generated a novel therapeutic ROBO2 fusion protein that functions as a SLIT ligand trap to treat podocyte injury in a pre-clinical animal model. Inhibiting the ROBO2/SLIT2 pathway therapeutically reduces proteinuria and improves podocyte ultrastructure. A phase 2 clinical trial to evaluate the safety and efficacy of ROBO2-Fc (PF-06730512) in patients with FSGS is currently ongoing (NCT03448692).

Funding

  • Other NIH Support