Focal Segmental Glomerulosclerosis (FSGS) Clinical Trials

Focal Segmental Glomerulosclerosis describes a pattern of kidney damage visible under the microscope, where only some glomeruli (and only segments of those glomeruli) show scarring and dysfunction. The disease can be primary, arising from an intrinsic kidney abnormality, or secondary to systemic conditions such as HIV infection, obesity, reflux nephropathy, or certain medications. Primary FSGS is thought to result from dysfunction of podocytes, specialized cells that form the filtering barrier in the glomerulus.

The most common symptoms of Focal Segmental Glomerulosclerosis include Heavy proteinuria leading to foamy urine, Swelling in the face, hands, feet, and legs from fluid retention, Weight gain from fluid accumulation, High blood pressure, Fatigue and weakness, among others. Approximately 7% of all kidney biopsies in the United States show FSGS; incidence is 0.2-1.7 cases per 100,000 person-years. Symptoms can range from mild to severe and may vary between individuals.

Trial Friend lists all active clinical trials for Focal Segmental Glomerulosclerosis from ClinicalTrials.gov, with eligibility criteria translated into plain English. Patients can filter by trial phase and recruitment status, search by location, and use the Match Me tool to score trials against their profile. On April 13, 2026, Filspari (sparsentan) became the first FDA-approved therapy for Focal Segmental Glomerulosclerosis, cleared for patients ages 8 and older without nephrotic syndrome to reduce proteinuria. It is a once-daily oral dual endothelin and angiotensin receptor blocker, dispensed through a restricted REMS program because of liver safety requirements, and it must not be taken during pregnancy.

On April 13, 2026, the FDA approved Filspari (sparsentan) as the first therapy specifically indicated for FSGS, covering adult and pediatric patients aged 8 and older without nephrotic syndrome (a condition where protein loss is severe enough to cause low blood albumin and significant swelling). Filspari is a once-daily oral pill that blocks two damage signals at once: endothelin and angiotensin. Because of the risk of liver injury, it is dispensed only through the FILSPARI REMS, a restricted program with regular liver tests. The label also carries a boxed warning that it can harm an unborn baby and must not be used during pregnancy. ACE inhibitors and angiotensin receptor blockers (ARBs), common blood pressure pills, remain the foundation for reducing protein in urine. SGLT2 inhibitors (originally diabetes drugs that also protect the kidneys) are increasingly used for additional kidney protection. For primary FSGS, doctors often add immunosuppressants including steroids, cyclosporine, tacrolimus, mycophenolate, or rituximab. Always consult a nephrologist about which combination fits your specific FSGS subtype, biopsy findings, and APOL1 status.

FSGS happens when injury hits the podocytes, the specialized cells that form your kidney's filtering barrier. Primary FSGS is thought to involve a "circulating permeability factor" that scientists have not yet identified. Secondary FSGS has many causes including HIV, obesity, urine reflux back to the kidneys (reflux nephropathy), sickle cell disease, certain medications, and APOL1 high-risk gene variants common in patients of African ancestry. Familial FSGS comes from inherited mutations in podocyte structural genes including NPHS2 (which makes a protein called podocin), TRPC6, INF2, ACTN4, WT1, and over 50 others. The result is loss of the filtering seal that normally keeps protein out of urine. Once protein leaks heavily, it is itself toxic to remaining podocytes, creating a self-amplifying cycle that drives focal scarring and progressive kidney function loss. Roughly half of untreated patients reach kidney failure within 5 to 10 years.

Genetic testing is increasingly important for FSGS because monogenic forms (FSGS caused by a single inherited gene defect) typically do not respond to immunosuppressants and may progress more quickly to transplant. Comprehensive nephrotic-syndrome gene panels test 30 to 70 or more genes, including NPHS1, NPHS2 (podocin), TRPC6, INF2, ACTN4, WT1, COL4A3 to A5 (the Alport syndrome genes), MYH9, and others. APOL1 genotyping identifies the high-risk G1 and G2 gene variants common in patients of African ancestry, which carry roughly 10 times higher FSGS risk and faster progression. Knowing your APOL1 status opens specific genotype-targeted trials (inaxaplin and others). Labs offering nephrotic-syndrome panels include GeneDx, Invitae, PreventionGenetics, and Blueprint Genetics. Genetic counseling, a meeting with a specialist who explains what test results mean for you and your family, is recommended, especially in early-onset FSGS or families with multiple affected members.

Eligibility for Focal Segmental Glomerulosclerosis clinical trials depends on factors like age, diagnosis, treatment history, and overall health. Each trial sets its own inclusion and exclusion criteria. Trial Friend translates these requirements from medical language into plain English so patients can review them more easily. The Match Me tool can score your profile against active trials to help identify studies that may be a fit.

Participating in a Focal Segmental Glomerulosclerosis clinical trial typically involves scheduled visits, medical tests, and close monitoring by a research team. Depending on the study phase, you may receive an investigational treatment, a placebo, or the current standard of care. Trials may last from a few weeks to several years. Study participation is voluntary, and you can withdraw at any time.

FSGS clinical trials commonly require maximum-tolerated ACE inhibitor or ARB therapy as background but exclude or require a washout from competing investigational agents, recent Filspari (sparsentan), prior atrasentan, and certain immunosuppressant combinations. SGLT2 inhibitors may be required as background or excluded depending on the trial. Immunosuppressant washouts vary widely: rituximab typically 6 or more months off, calcineurin inhibitors (tacrolimus, cyclosporine) 4 to 12 weeks, high-dose steroids 4 to 8 weeks, and cyclophosphamide 12 or more weeks. Trial Friend's medication conflict checker scans each trial's exclusion criteria against common FSGS medications including endothelin antagonists, RAAS blockers (the ACE/ARB family), corticosteroids, calcineurin inhibitors, mycophenolate, rituximab, cyclophosphamide, and SGLT2 inhibitors. The checker flags the specific drug, the trial's exclusion language, and a confidence level so you can plan a washout strategy with your nephrologist.

Key questions to ask your nephrologist about FSGS clinical trials: Was my FSGS classified on biopsy as primary, secondary, or genetic, and should APOL1 gene testing be done? Is my current protein-in-urine level and kidney function (eGFR) at the level the trials I am interested in require, or am I close to the cutoff? Now that Filspari is approved, should I start it now, or hold off and try a trial of a different mechanism (atrasentan, complement inhibitors, podocyte-protective drugs) first? Should we run a comprehensive genetic panel to rule out an inherited cause, since genetic FSGS often does not respond to immunosuppressants? What washout would I need from my current ACE inhibitor, ARB, or immunosuppressant before a trial, and what are the risks of stopping treatment during the washout?