Filspari (sparsentan)
An approved treatment for IgA Nephropathy and Focal Segmental Glomerulosclerosis.
The same compound appears under different names depending on the context. Here is how to identify Sparsentan wherever you encounter it, plus the key facts at a glance.
- Generic name
- Sparsentan
- Brand name
- Filspari
- Development code
- TSP-0005
- Drug class
- Dual endothelin/angiotensin receptor antagonist
- Manufacturer
- Travere Therapeutics
- How it's taken
- Filspari is taken as a tablet by mouth once daily, swallowed with water before the morning or evening meal.
A non-immunosuppressive pill that blocks two molecules (angiotensin and endothelin) driving kidney damage, allowing kidneys to filter better and slowing disease progression. Approved by the FDA for IgA nephropathy in February 2023 (accelerated) and September 2024 (full), and on April 13, 2026 became the first-ever FDA-approved treatment for Focal Segmental Glomerulosclerosis (FSGS) in patients ages 8 and older without nephrotic syndrome.
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Where Sparsentan fits
The first and only FDA-approved therapy for Focal Segmental Glomerulosclerosis, approved April 13, 2026, and a leading non-immunosuppressive option for IgA nephropathy. Combines endothelin ETA and angiotensin AT1 receptor blockade in one pill, replacing the need for two separate medicines in some patients.
How Sparsentan works
Filspari uses a dual-action approach to protect the kidneys. It blocks two different receptors that drive kidney damage: endothelin A and angiotensin II. Blocking both pathways at once in a single pill reduces the pressure inside the tiny filters of the kidney, lowers inflammation, and cuts the amount of protein leaking into urine.
In both IgA nephropathy and Focal Segmental Glomerulosclerosis, heavy proteinuria is the main driver of long-term kidney scarring, which is why reducing it is the main goal of treatment.
Mechanism: Dual antagonist blocking both angiotensin II AT1 receptors and endothelin ETA receptors, reducing vasoconstriction and kidney scarring
Side effects and safety
Common side effects include high potassium, low blood pressure, swelling in the legs, dizziness, anemia, and in IgA nephropathy, sudden kidney injury. Filspari has a boxed warning for liver injury and for harm to an unborn baby. Because of the liver risk, it is only available through a restricted program called the FILSPARI REMS. Liver tests are done before starting and then every 3 months. A pregnancy test is needed before starting, and people who can become pregnant must use effective birth control during treatment and for 2 weeks after stopping. It must not be taken with angiotensin receptor blockers (ARBs), other endothelin receptor antagonists, or aliskiren.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Sparsentan
Filspari is taken as a tablet by mouth once daily, swallowed with water before the morning or evening meal. People who cannot swallow tablets can crush the tablet and mix it in water right before taking it. For IgA nephropathy, adults start at 200 mg and increase to 400 mg after 14 days. For FSGS (adults and children 8 and older), people over 50 kg start at 400 mg and increase to 800 mg after 14 days, and people 50 kg or less start at 200 mg and increase to 400 mg. Before starting, doctors stop other medicines that act on the same blood pressure hormone system, such as ACE inhibitors and ARBs, and any endothelin receptor antagonist. Everyone on Filspari must be enrolled in the FILSPARI REMS program, which covers the required liver monitoring.
Availability and cost
Only available as the brand-name product.
Dual-acting angiotensin and endothelin receptor antagonist in a single molecule. Orphan drug designations in both IgA nephropathy and Focal Segmental Glomerulosclerosis.
Help paying for Filspari
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Copay help
$0 copay program for eligible commercially insured patients; annual maximum benefit applies.
For: private insurance · source - Insurance and case manager help
Dedicated Nurse Educator helps with starting treatment, financial support, refills, and help for government-insured and uninsured patients.
The official page does not say who qualifies. Ask the program. · source - Other support
REMS liver lab testing at home at no cost for eligible patients.
The official page does not say who qualifies. Ask the program. · source
Good to know: Uninsured patients: nurse educator checks whether more support is available.
- From a charity · NORD RareCareIgA Nephropathy Medical Assistance fundOpen
Pays for: Medical and medication costs.
The foundation says: “Accepting new applications and re-enrollments for current year” - From a charity · NORD RareCareIgA Nephropathy Premium Copay Assistance fundOpen
Pays for: Insurance premiums and copays.
The foundation says: “Accepting new applications and re-enrollments for current year” - From a charity · The Assistance FundImmunoglobulin A Nephropathy (IgAN) fundOpen
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
The foundation says: “OPEN — Accepting New Patients. TAF is currently accepting new patient enrollments for this program.” - From a charity · IgA Nephropathy FoundationIgA Nephropathy Foundation Patient Aid Grant fundApply directly
Pays for: Out-of-pocket medical costs and non-medical costs of treatment such as childcare or transportation (Foundation membership required).
The foundation says: “Status not shown on page” - From a charity · The Assistance FundFocal Segmental Glomerulosclerosis (FSGS) fundOpen
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
The foundation says: “OPEN — Accepting New Patients. TAF is currently accepting new patient enrollments for this program.”
How IgA nephropathy treatments compare
As of 2026, five FDA-approved medicines are available for IgA nephropathy, plus active investigational programs. The right choice depends on your proteinuria level, kidney function (eGFR), prior treatments, biopsy findings, and personal preferences around oral pills versus injections. Your nephrologist will help match a treatment to your specific situation. This chart compares the practical differences between options.
5 FDA-approved iga nephropathy treatments are available: Tarpeyo (budesonide (delayed release), approved 2021); Filspari (sparsentan, approved 2023); Fabhalta (iptacopan, approved 2024); Vanrafia (atrasentan, approved 2025); Voyxact (sibeprenlimab, approved 2025); BHV-1400 (BHV-1400, Phase 1). Tarpeyo is typically used as standard corticosteroid considerations apply (immunosuppression, infection risk, glucose changes); first disease-modifying therapy approved specifically for igan.
| Drug | What makes it different | How it works | How it’s given | How often | Where you get it | Safety highlights | FDA approved |
|---|---|---|---|---|---|---|---|
Tarpeyo budesonide (delayed release) | Targets the disease at its source in the gut | Targeted-release corticosteroid that suppresses Gd-IgA1 antibody production in gut-associated lymphoid tissue (Peyer’s patches) | Oral capsule (taken on an empty stomach) | Once daily | Home (specialty pharmacy delivery) | Standard corticosteroid considerations apply (immunosuppression, infection risk, glucose changes); first disease-modifying therapy approved specifically for IgAN | 2021 |
Filspari sparsentan You are here | Dual ETA + AT1 receptor block in one pill (non-immunosuppressive) | Dual endothelin-A and angiotensin-II AT1 receptor antagonist that reduces glomerular pressure and proteinuria | Oral tablet (REMS program) | Once daily | Home (REMS-certified specialty pharmacy) | Boxed warnings for hepatotoxicity and major birth defects; monthly liver enzyme monitoring; confirmed contraception required (pregnancy contraindicated) | 2023 |
Fabhalta iptacopan | First oral complement inhibitor for IgAN | Selective oral inhibitor of complement factor B that blocks alternative-pathway activation driving kidney inflammation | Oral capsule (REMS program) | Twice daily | Home (REMS-certified specialty pharmacy) | Boxed warning for serious encapsulated-bacteria infections; meningococcal, pneumococcal, and Hib vaccinations required at least 2 weeks before starting | 2024 |
Vanrafia atrasentan | Selective ETA blocker, no REMS or routine liver monitoring required | Selective endothelin-A receptor antagonist that reduces glomerular hypertension and fibrosis | Oral tablet (no REMS required) | Once daily | Home (specialty pharmacy delivery) | Boxed warning for major birth defects (pregnancy contraindicated); contraception required during and for 2 weeks after treatment; warnings include hepatotoxicity, fluid retention, and decreased sperm counts | 2025 |
Voyxact sibeprenlimab | First APRIL antagonist; self-injected at home once a month | Monoclonal antibody that blocks APRIL signaling, reducing B-cell production of pathogenic Gd-IgA1 antibodies | Subcutaneous injection (self-administered, no REMS required) | Every 4 weeks | Home (after training from care team) | Routine vaccinations should be up-to-date before starting; live vaccines avoided during treatment; immunoglobulin levels are monitored periodically | 2025 |
BHV-1400 BHV-1400 | Selectively removes only the disease-driving antibody; spares normal immunity | TRAP degrader that selectively binds Gd-IgA1 and routes it to the liver for clearance, sparing normal antibodies | Subcutaneous injection | Phase 1 expansion cohort enrolling IgAN patients; pivotal regimen TBD | Clinical trial site only (not commercially available) | Investigational — Phase 1 healthy-volunteer single-dose data showed up to 81% Gd-IgA1 reduction; spares normal IgA, IgG, IgE, and IgM; pivotal trial planned for 2026 | Phase 1 |
This chart compares FDA-approved IgA nephropathy treatments and one advanced investigational program (BHV-1400). It is not medical advice. All approved IgAN therapies require background renin-angiotensin system (RAS) blockade with an ACE inhibitor or ARB, and many patients also take an SGLT2 inhibitor. Treatment selection should be made with your nephrologist based on your kidney function, biopsy results, proteinuria level, comorbidities, and prior therapies.
Clinical trial results
2 pivotal trials supported approval. In IgA nephropathy, the Phase 3 PROTECT trial (n=404) compared sparsentan with irbesartan. At the 36-week interim analysis, urine protein fell 45% with sparsentan versus 15% with irbesartan. Over 110 weeks, kidney function (eGFR) declined 3.0 points a year on sparsentan versus 4.2 on irbesartan, and the FDA label now says Filspari slows kidney function decline in IgA nephropathy[5].
In Focal Segmental Glomerulosclerosis, the Phase 3 DUPLEX trial (n=371, 108 weeks) missed its primary eGFR slope endpoint but showed a durable and substantial reduction in proteinuria versus irbesartan. At the prespecified 36-week interim analysis, 42.0% of patients on sparsentan reached partial remission of proteinuria versus 26.0% on irbesartan[3]. At 108 weeks, sparsentan delivered a 48% reduction vs 27% with irbesartan in patients without nephrotic syndrome, the FDA-approved population[5]. FDA accepted the proteinuria benefit as evidence of meaningful clinical value for a rare progressive disease with no other approved therapy[1].
Development history
Sparsentan was originally developed by Retrophin (renamed Travere Therapeutics in 2020) and is headquartered in San Diego, California. The FDA gave accelerated approval for IgA nephropathy in February 2023 and full approval in September 2024. The road to FSGS approval was much harder: DUPLEX missed its primary eGFR endpoint in 2023, and Travere did not file for FSGS until 2025, when the FDA accepted its application based on the full 2-year DUPLEX data and the Phase 2 DUET study.
In January 2026 the FDA extended its review by 3 months after Travere submitted requested information on the drug's clinical benefit. On April 13, 2026, the FDA granted Filspari its FSGS indication, making it the first drug ever approved for the disease[1].
Explore IgA Nephropathy and Focal Segmental Glomerulosclerosis trials
Other IgA Nephropathy & Focal Segmental Glomerulosclerosis treatments
Sparsentan in Trial Friend News and Guides
- Your Insurer Denied a Rare Disease Drug and Fewer Than 1 in 100 People Appeal, So Here Is the PlaybookSeptember 26, 2026
- Filspari Is the First FDA-Approved Treatment for FSGS. Here's What That Actually Means for Patients.April 14, 2026
- A Quiet Crisis in Rare Disease Research: Trial Enrollment Is Slowing Just as Treatments Start WorkingApril 13, 2026
- From Zero Treatments to 5 in 3 Years: The IgA Nephropathy Breakthrough Nobody Saw ComingMarch 31, 2026
Common questions about Sparsentan
▸What is Sparsentan (Filspari)?
A non-immunosuppressive pill that blocks two molecules (angiotensin and endothelin) driving kidney damage, allowing kidneys to filter better and slowing disease progression. Approved by the FDA for IgA nephropathy in February 2023 (accelerated) and September 2024 (full), and on April 13, 2026 became the first-ever FDA-approved treatment for Focal Segmental Glomerulosclerosis (FSGS) in patients ages 8 and older without nephrotic syndrome.
▸How does Sparsentan work?
Filspari uses a dual-action approach to protect the kidneys. It blocks two different receptors that drive kidney damage: endothelin A and angiotensin II. Blocking both pathways at once in a single pill reduces the pressure inside the tiny filters of the kidney, lowers inflammation, and cuts the amount of protein leaking into urine.
In both IgA nephropathy and Focal Segmental Glomerulosclerosis, heavy proteinuria is the main driver of long-term kidney scarring, which is why reducing it is the main goal of treatment.
▸What are the side effects of Sparsentan?
Common side effects include high potassium, low blood pressure, swelling in the legs, dizziness, anemia, and in IgA nephropathy, sudden kidney injury. Filspari has a boxed warning for liver injury and for harm to an unborn baby. Because of the liver risk, it is only available through a restricted program called the FILSPARI REMS. Liver tests are done before starting and then every 3 months. A pregnancy test is needed before starting, and people who can become pregnant must use effective birth control during treatment and for 2 weeks after stopping. It must not be taken with angiotensin receptor blockers (ARBs), other endothelin receptor antagonists, or aliskiren.
▸How is Sparsentan taken?
Filspari is taken as a tablet by mouth once daily, swallowed with water before the morning or evening meal. People who cannot swallow tablets can crush the tablet and mix it in water right before taking it. For IgA nephropathy, adults start at 200 mg and increase to 400 mg after 14 days. For FSGS (adults and children 8 and older), people over 50 kg start at 400 mg and increase to 800 mg after 14 days, and people 50 kg or less start at 200 mg and increase to 400 mg. Before starting, doctors stop other medicines that act on the same blood pressure hormone system, such as ACE inhibitors and ARBs, and any endothelin receptor antagonist. Everyone on Filspari must be enrolled in the FILSPARI REMS program, which covers the required liver monitoring.
▸Is Sparsentan FDA approved?
Yes, Sparsentan (Filspari) is FDA approved (2023) for the treatment of IgA Nephropathy and Focal Segmental Glomerulosclerosis.
▸Is Filspari the first FDA-approved treatment for FSGS?
Yes. On April 13, 2026, the FDA approved Filspari (sparsentan) to reduce proteinuria in adults and pediatric patients ages 8 and older with Focal Segmental Glomerulosclerosis (FSGS) without nephrotic syndrome. Before this approval, no therapy was specifically approved for FSGS, and patients were treated with off-label ACE inhibitors, angiotensin receptor blockers, steroids, and other immunosuppressants.
▸How long will it take for FSGS patients to actually get Filspari?
Filspari is already commercially available for IgA nephropathy through the FILSPARI REMS program, so the distribution system exists on day one. Patients with FSGS can be prescribed the drug immediately, but practical access usually takes weeks to a few months. Your nephrologist must enroll you in the REMS, the central pharmacy will ship the medicine, and commercial or Medicare insurance typically requires prior authorization. Travere TotalCare offers a $0 copay program for eligible commercially insured patients, and its nurse educators can help if you have government insurance or none; independent kidney foundations may also help with costs.
▸Why was Filspari approved for FSGS even though the DUPLEX trial missed its primary goal?
The DUPLEX trial's primary endpoint was the rate of kidney function decline (eGFR slope) over 108 weeks, and sparsentan did not meet statistical significance on that specific measure. However, the trial showed a large and sustained reduction in proteinuria, which is the most important driver of long-term kidney damage in FSGS. Because FSGS is a rare, progressive disease with no other approved therapy, and because patient advocacy groups like NephCure have worked with the FDA on the PARASOL project to formally evaluate proteinuria as a surrogate endpoint, the agency accepted the proteinuria data as evidence of clinical benefit.
▸Does Filspari cure FSGS?
No. Filspari is not a cure. It is designed to reduce proteinuria and slow the progression of kidney damage, which can delay or prevent the need for dialysis or a kidney transplant for many patients. It does not reverse kidney scarring that has already occurred, and it has to be taken continuously to maintain its effect. Filspari is one part of a treatment plan that also includes blood pressure control, dietary changes, and regular nephrology follow-up.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- Travere Therapeutics · April 13, 2026. Travere Therapeutics Announces FDA Approval of FILSPARI (sparsentan) for Focal Segmental Glomerulosclerosis (FSGS). https://ir.travere.com/press-releases/news-details/2026/Travere-Therapeutics-Announces-Full-FDA-Approval-of-FILSPARI-sparsentan-the-First-and-Only-Approved-Medicine-for-FSGS/default.aspx
- The American Journal of Managed Care · April 14, 2026. FDA Approves Sparsentan for Focal Segmental Glomerulosclerosis. https://www.ajmc.com/view/fda-approves-issues-crl-for-sparsentan-for-focal-segmental-glomerulosclerosis
- New England Journal of Medicine 2023;389:2436-2445 · 2023. Sparsentan versus Irbesartan in Focal Segmental Glomerulosclerosis. https://pubmed.ncbi.nlm.nih.gov/37921461/
- The Lancet · 2023. Efficacy and safety of sparsentan versus irbesartan in patients with IgA nephropathy (PROTECT): 2-year results from a randomised, active-controlled, phase 3 trial. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(23)02302-4/fulltext
- U.S. Food and Drug Administration · April 2026. FILSPARI (sparsentan) tablets, Prescribing Information. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d7354af1-f304-f4d9-e053-2995a90ab219
- NephCure Kidney International. PARASOL: Proteinuria and GFR as Clinical Trial Endpoints in Focal Segmental Glomerulosclerosis. https://nephcure.org/parasol/