An Open-Label Phase 2 Study of N-Acetyl-D-Mannosamine (ManNAc) in Subjects With Podocyte Diseases

Background: Podocyte diseases are a group of kidney conditions that include focal segmental glomerulosclerosis (FSGS), minimal change disease (MCD), and membranous nephropathy (MN). In these conditions, specialized kidney cells called podocytes, which help prevent protein from leaking into the urine, are damaged. This can result in high levels of protein in the urine and, over time, worsening kidney function. In some people, the disease may progress to kidney failure requiring dialysis or a kidney transplant. Several treatments are currently available and can be beneficial, but they may cause significant side effects and may not work well for everyone. Therefore, there is a need for safer and more effective treatments for people with these types of kidney conditions. Objective: To test a study drug (ManNAc) in people with a podocyte disease, that includes Focal Segmental Glomerulosclerosis (FSGS), Minimal Change Disease (MCD), or Membranous Nephropathy (MN). Eligibility: People aged 18 years and older with a podocyte disease, that includes Focal Segmental Glomerulosclerosis (FSGS), Minimal Change Disease (MCD), or Membranous Nephropathy (MN). Design: Participants will have 5 to 6 clinic visits over 14 weeks. Two of the visits will require overnight stays for 2 or 3 nights. ManNAc is a white powder that comes in a sachet. It is dissolved in water and taken twice a day by mouth. Participants will take their first dose at the clinic. They will learn how to store ManNAc and prepare each dose. They will record their doses in a diary. They will also write down any adverse effects or troubles they have using the drug at home. During clinic visits, participants will have physical exams with blood and urine tests. They will complete questionnaires about their health, sleep habits, and fatigue symptoms. During overnight visits, participants will also have 24-hour urine collection. A study team member will call participants 1 week after the first dose to check on their health. Follow-up phone calls will then be every 2 weeks after each clinic visit. Participants may meet with a dietitian to discuss nutrition while taking the ManNAc. Participants may choose to have genetic tests.