AMPK-activation by Metformin in FSGS: AMP-FSGS

Focal Segmental glomerulosclerosis (FSGS) is currently the most common primary glomerular disease that progresses to ESKD in the US. FSGS is typified by significant proteinuria, and by disorganization of the actin cytoskeleton of highly specialized epithelial cells which support the glomerular capillary loop called podocytes. Podocytes are characterized by foot processes, whose disorganization with injury is visualized on electron microscopy as foot process effacement (FPE). Podocytes are also incapable of self-renewal, and podocyte loss over ~40% per glomerulus leads to proteinuria, the nephrotic syndrome (NS) and FSGS. Such critical podocyte loss alone is sufficient for progressive CKD and ESKD. Currently, the reported rate of complete and/or partial response is 40-70% in various series with a rate of progression to ESKD 30-53% in 5-10 years.

Distinct from FSGS, Minimal Change Disease (MCD), which despite showing similar diffuse FPE and NS, has preserved podocyte numbers and rare progression to ESKD (5-20% in 20 years). MCD can be morphologically indistinguishable from early FSGS, and some MCD cases reportedly transition to FSGS. Hence, identifying and targeting mechanisms in MCD that specifically promote survival of injured podocytes with FPE, could help switch an FSGS phenotype to an "MCD-like" phenotype, and prevent or retard progression of FSGS. Currently, therapeutics in FSGS focus on immune modulation, or on hemodynamic interventions used in generically all cases of NS. Specific strategies to directly promote podocyte survival and limit podocytopenia to within the critical threshold during injury, have not been pursued clinically. Hence, many FSGS cases will progress to ESKD or encounter dose limiting side-effects of immune therapies (corticosteroids, or other agents), representing a significant therapeutic gap in the field.

In this context, MF is an Ampk-activator that is widely used, demonstrably safe, and inexpensive with reported renal benefit in diabetic and non-diabetic CKD. Its specific utility to promote cell survival of injured podocytes in FSGS has never been tested. Our preclinical data shows that an "MCD-like" pathology with podocyte injury/FPE transitioned to podocytopenia and FSGS by AMPK inhibition, while AMPK activation with MF mitigated podocytopenia in FSGS models.

The purpose of this study is to test whether Metformin use in individuals with FSGS as an adjunct to standard -of-care (corticosteroids, anti RAAS measures, BP control) is safe and will activate kidney cell AMPK and reduce podocyte injury. The primary objective is to determine whether extended-release MF (in addition to standard of care (S-o-C)) is superior to placebo in reducing podocyte injury and promoting podocyte survival by 6-months in Focal Segmental Glomerulosclerosis (FSGS). Specifically, for this purpose, this study will primarily evaluate sequential urinary podocyte mRNA excretion to identify individual urinary mRNA trajectories representing podocyte injury/depletion and potential prognostic signals in the MF study limb vs control.

A secondary objective of this study is to use multiple blood, urine and biopsy assays to test whether the addition of Metformin ( to S-o-C) mitigates kidney disease progression parameters superior to placebo. These assays will include large scale urine and serum protein profiling, protein and RNA tests performed in kidney biopsies.

Another secondary objective of this study is to test whether the addition of Metformin ( to S-o-C) is safe in patients with proteinuria and FSGS. This will be accomplished by specific questionnaires and blood tests geared towards MF-associated adverse effects.

Results of this study will inform a larger, phase 2/3 randomized trial which will evaluate the efficacy of MF treatment versus placebo in attenuating proteinuria and kidney function decline in FSGS.