Pronunciation: fil-spah-ree
Generic name: sparsentan
Dosage form: oral tablet (200 mg, 400 mg)
Drug classes: Miscellaneous cardiovascular agents, Miscellaneous genitourinary tract agents

Medically reviewed by Carmen Pope, BPharm. Last updated on Sep 5, 2025.

What is Filspari? IgA Nephropathy Treatment

Filspari is used to treat immunoglobulin A nephropathy (IgAN) to slow kidney function decline in adults with primary IgA nephropathy who are at risk for disease progression. It is an FDA-approved, non-immunosuppressive, oral tablet that is taken once a day.

Key Facts About Filspari:

• Generic name: Sparsentan
• Drug class: Dual Endothelin Angiotensin Receptor Antagonist (DEARA)
• Administration: Oral tablet taken once daily
• FDA approval: Full approval received September 5, 2024
• Previous status: Accelerated approval since February 2023.

How Does Flispari Work?

Filspari works by blocking two pathways thought to contribute to kidney function decline in IgAN, the endothelin-1 and angiotensin II pathways. It helps reduce inflammation in the kidneys and protein in the urine while helping maintain blood pressure. Filspari belongs to the drug class called endothelin and angiotensin II receptor antagonists.

Clinical Evidence: The PROTECT Study

Filspari's effectiveness is backed by the PROTECT study (NCT03762850), a Phase 3 clinical trial involving 404 patients with IgA nephropathy. This head-to-head trial demonstrated that Filspari delivered superior long-term kidney function preservation compared to irbesartan over 110 weeks.

Key PROTECT Study Results:

• Significant reduction in proteinuria (protein in urine)
• Better preservation of kidney function over 2+ years
• 95% of patients (192 of 202) successfully reached the target 400 mg dose.

Filspari Side Effects

Most Common Side Effects

• Peripheral edema (swelling of hands, legs, ankles, and feet)
• Anemia (low red blood cell count)
• Dizziness.

Serious Side Effects and Boxed Warnings

Liver Toxicity (Boxed Warning)

Filspari can affect your liver. Liver failure was not observed in people treated with Filspari in clinical studies, but some medicines that are like Filspari can cause liver failure.

Your healthcare provider will do blood tests to check your liver before starting treatment with Filspari, then every 3 months during treatment. Your healthcare provider may temporarily stop or permanently stop treatment with Filspari if you have changes in your liver tests. Stop taking Filspari and get immediate medical attention for: 

• Nausea, vomiting, or stomach pain (upper right)
• pain on the upper right side of your stomach
• tiredness
• loss of appetite
• yellowing of your skin or the white part of your eyes (jaundice)
• dark “tea-colored” urine
• fever
• itching.

Pregnancy Risks (Boxed Warning)

Filspari can cause serious birth defects if taken during pregnancy.

• Patients who can become pregnant must not be pregnant when they start taking Filspari or become pregnant during treatment with Filspari or for two weeks after stopping treatment.
• Monthly pregnancy tests are required during treatment and for 2 weeks after stopping treatment.
• Not recommended during breastfeeding.

Low Blood Pressure

Low blood pressure is common during treatment with Filspari and can also be serious. Tell your healthcare provider if you feel dizzy, light-headed, or faint. Stay hydrated during treatment.

Worsening of Kidney Function

Your healthcare provider will check your kidney function during treatment with Filspari.

Increased Blood Potassium

This is common during treatment with Filspari and can also be serious. Your healthcare provider will check your potassium blood level during treatment.

Fluid Retention

Filspari can cause your body to hold too much water. Tell your healthcare provider right away if you have any unusual weight gain or swelling of your ankles or legs.

These are not all the possible side effects of Filspari. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Related/similar drugs

Filspari REMS Program

Because of the risk of liver toxicity, Filspari is only available through a restricted program called the Filspari REMS.

• Under the Filspari REMS, prescribers, patients, and pharmacies must enroll in the program.
• Pharmacies that dispense Filspari must be certified with the Filspari REMS and must dispense only to patients who are authorized to receive this medication.
• Further information is available at www.filsparirems.com or 1-833-513-1325

Before taking

Absolute Contraindications

Do NOT take Filspari if you:

• Are pregnant or planning to become pregnant
• Have severe liver problems
• Are breastfeeding
• Have had allergic reactions to sparsentan, Filspari, or any of the inactive ingredients in the tablets
• Are under the age of 18.

Talk to Your Doctor if You Have:

• Liver problems
• Kidney disease progression
• Low blood pressure
• High potassium levels.

Pregnancy Considerations

Filspari can cause serious birth defects. Patients who can become pregnant must have a negative pregnancy test before starting Filspari and must have a monthly negative pregnancy test during treatment and 2 weeks after stopping treatment with Filspari.

Patients who can become pregnant must use effective birth control before starting treatment with Filspari, during treatment with Filspari, and for two weeks after stopping Filspari because the medicine may still be in your body.

• If you have had a tubal sterilization or have an IUD (intrauterine device) or progesterone implant, these methods may be used alone, and no other form of birth control is needed.
• Talk with your healthcare provider or gynecologist (a healthcare provider who specializes in reproduction) to find out about options for effective forms of birth control that you may use to prevent pregnancy during treatment with Filspari.
• If you decide that you want to change the form of birth control that you use, talk with your healthcare provider or gynecologist to be sure that you choose another effective form of birth control.

See the Filspari Package Insert for acceptable birth control options during treatment with Filspari. Do not have unprotected sex. Talk to your healthcare provider or pharmacist right away if you have unprotected sex or if you think your birth control has failed. Your healthcare provider may talk with you about using emergency birth control.

Tell your healthcare provider right away if you miss a menstrual period or think you may be pregnant.

Breastfeeding Considerations

It is not known if Filspari passes into your breast milk. Do not breastfeed during treatment with Filspari. Talk to your healthcare provider about the best way to feed your baby during treatment with Filspari.

Dosage and Administration

Standard Filspari Dosing Schedule:

• Starting dose: 200 mg once daily
• Target dose: 400 mg once daily (after 14 days, if tolerated)
• Timing: Take before the same meal each day (morning or evening)
• Important: Swallow whole - do not crush, break, or chew

Special Considerations:

• If taking antacids: Take Filspari 2 hours before or after antacid use
• Your doctor may need to discontinue other medications (ARBs, ERAs, or aliskiren) before starting Filspari
• When resuming after interruption: May require dose re-titration.

What happens if I miss a dose?

If you miss a dose, take the next dose at the regularly scheduled time. Do not take 2 doses at the same time or take extra doses.

What happens if I overdose?

 If you take too much Filspari, call your healthcare provider or go to the nearest hospital emergency room right away.

What other drugs affect this medicine?

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, herbal supplements, and grapefruit. Filspari and other medicines may affect each other and cause side effects. Do not start any new medicine until you check with your healthcare provider.

Especially tell your healthcare provider if you take:

• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Potassium-containing medicines, potassium supplements, or salt substitutes containing potassium
• Blood pressure medicines
• H2 receptor blocker medicine or proton pump inhibitor (PPI) medicine
• Grapefruit products.

Ask your healthcare provider or pharmacist if you are not sure if you take one of these medicines.

Storage

Store at room temperature between 68°F to 77°F (20°C to 25°C).

Store in the original container. The bottle has a child-resistant closure.

Keep out of the reach of children.

Filspari Ingredients

Active ingredient: sparsentan

Inactive ingredients: colloidal silicon dioxide, lactose anhydrous, magnesium stearate, silicified microcrystalline cellulose, and sodium starch glycolate. Tablets are film-coated with material containing macrogol/polyethylene glycol, polyvinyl alcohol-partially hydrolyzed, talc, and titanium dioxide.

Available as 200 mg and 400 mg tablets

Manufacturer

Filspari (sparsentan) is manufactured by Travere Therapeutics, a biopharmaceutical company headquartered in San Diego, California. Travere Therapeutics (formerly known as Retrophin) focuses on developing treatments for rare diseases, with a particular emphasis on kidney and liver disorders.

Frequently Asked Questions

Is Filspari safe for children?

It is not known if Filspari is safe and effective in children under 18.

How long does it take to see results?

Clinical benefits on proteinuria can be seen within weeks, with kidney function preservation benefits demonstrated over months to years.

Can I stop taking Filspari suddenly?

No, do not stop taking Filspari without consulting your healthcare provider.

What should I do if I miss a dose?

Take your next dose at the regularly scheduled time. Do not double up on doses.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer