Ogsiveo (nirogacestat)
An approved treatment for Desmoid Tumors.
Drug facts
The same compound appears under different names depending on the context. Here is how to identify Nirogacestat wherever you encounter it, plus the key facts at a glance.
- Generic name
- Nirogacestat
- Brand name
- Ogsiveo
- Drug class
- Gamma secretase inhibitor
- Manufacturer
- SpringWorks Therapeutics (part of Merck KGaA, Darmstadt, Germany)
- How it's taken
- Oral tablet twice a day
A twice-daily pill and the first FDA-approved treatment for desmoid tumors, for adults whose tumors are growing and need systemic treatment. In its placebo-controlled trial, the tumor grew in 17% of people on Ogsiveo against 51% on placebo.
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Where Nirogacestat fits
Before Ogsiveo, people with desmoid tumors were treated with surgery, radiation or medicines approved for other conditions; in DeFi, 33% had already taken a tyrosine kinase inhibitor and 36% chemotherapy.
How Nirogacestat works
Nirogacestat blocks gamma secretase, an enzyme that switches on the Notch receptor by cutting it. When Notch signaling is out of balance, it can activate pathways that help tumors grow[1]. Most desmoid tumors in its trial carried a change in the CTNNB1 gene (81% of those tested) and some an APC change (21%)[1].
Side effects and safety
- Diarrhea. In 84% of trial patients, grade 3 in 16%, starting a median of 9 days in; managed with antidiarrheal medicines and dose changes.
- Ovarian toxicity. In 75% of women who could become pregnant, including missed periods, early menopause and ovarian failure; effects may continue after stopping, and long-term effects on fertility are not established.
- Liver enzyme rises. ALT rose in 30% and AST in 33%; grade 3 rises in 6% and 2.9%.
- Non-melanoma skin cancers. Squamous cell carcinoma in 2.9% and basal cell carcinoma in 1.4%; skin checks before and during treatment.
- Low phosphate and potassium. Low phosphate in 65% and low potassium in 22%; levels are checked and supplemented as needed.
- Allergic reactions. Severe hypersensitivity reactions have been reported since approval.
- Pregnancy. Can harm an unborn baby; contraception during treatment and for 1 week after the last dose.
- Liver tests regularly
- Phosphate and potassium regularly
- Skin exams before starting and during treatment
- Menstrual changes and symptoms such as hot flashes, night sweats or vaginal dryness
Ogsiveo has no boxed warning and no contraindications. In the DeFi trial, diarrhea affected 84% of patients (grade 3 in 16%), and ovarian toxicity, such as missed periods, early menopause or ovarian failure, affected 75% of women who could become pregnant; the label says the long-term effects on fertility have not been established and that these effects may continue after stopping[1].
Other warnings are liver enzyme rises (ALT in 30%, AST in 33%), new non-melanoma skin cancers (squamous cell in 2.9%, basal cell in 1.4%), low phosphate (65%) and low potassium (22%), severe allergic reactions reported after approval, and harm to an unborn baby[1]. Other common side effects were rash (68%), nausea (54%), fatigue (54%), mouth sores (39%), headache (30%), abdominal pain (22%), cough (20%), hair loss (19%), upper respiratory infection (17%) and shortness of breath (16%), and 20% of patients stopped Ogsiveo because of a side effect[1].
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 Nirogacestat
The dose is 150mg by mouth twice a day, with or without food, until the tumor progresses or side effects become unacceptable[1]. Tablets are swallowed whole and never broken, crushed or chewed. After vomiting or a missed dose, the next dose is taken at its usual time. For several severe side effects the drug is paused and restarted at 100mg twice a day[1].
Availability and cost
Only available as the brand-name product.
Help paying for Ogsiveo
With private insurance, the drugmaker's copay card can lower what you pay for Ogsiveo. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE, but charity funds often can. The charity fund for Desmoid Tumors was not taking new applications on November 2, 2026. Pick your insurance below to see which offers fit you.
- Copay help
Commercial Copay Program: people with commercial insurance may pay as little as $0. An annual benefit maximum applies, and full terms are given at enrollment.
For: private insurance · source - Insurance and case manager help
Nurse Advocates answer questions about desmoid tumors, help with dosing reminders and coordinate with the doctor's office and pharmacy. Call 844-227-3755, Monday to Friday, 8 AM to 10 PM ET.
The official page does not say who qualifies. Ask the program. · source
Good to know: The Ogsiveo support page does not describe a free drug or bridge program, though the Gomekli page from the same company does; none is recorded for Ogsiveo until SpringWorks publishes one. Checked on November 2, 2026.
Charity funds for Desmoid Tumors
No charity fund for this condition is open right now. Funds reopen when they receive new donations; the foundations let you sign up to be told when one opens.
Access and eligibility
Adults with progressing desmoid tumors who need systemic treatment. The trial enrolled people whose tumors had grown within the previous 12 months and who could not have surgery.
Source: SpringWorks CareConnections
Access program details are provided for informational purposes and may vary based on insurance coverage, geographic location, and individual circumstances. Confirm current eligibility directly with the manufacturer or your specialty pharmacy.
Clinical trial results
DeFi (NCT03785964) randomly assigned 142 adults with desmoid tumors that had grown within the previous 12 months and could not be treated with surgery to Ogsiveo or placebo. The tumor progressed in 17% of the Ogsiveo group and 51% of the placebo group (hazard ratio 0.29), and median progression-free survival was not reached with Ogsiveo, against 15.1 months with placebo[1].
Tumors responded in 41% of people on Ogsiveo, including 7% complete responses, against 8% on placebo[1]. The median age was 34, and 65% of patients were women.
Development history
The FDA approved Ogsiveo on November 27, 2023 as the first treatment for desmoid tumors[2][3]. SpringWorks Therapeutics became part of Merck KGaA, Darmstadt, Germany on July 1, 2025[4], and the label was last updated in September 2026[1].
Explore Desmoid Tumors trials
Common questions about Nirogacestat
▸What is Nirogacestat (Ogsiveo)?
A twice-daily pill and the first FDA-approved treatment for desmoid tumors, for adults whose tumors are growing and need systemic treatment. In its placebo-controlled trial, the tumor grew in 17% of people on Ogsiveo against 51% on placebo.
▸How does Nirogacestat work?
Nirogacestat blocks gamma secretase, an enzyme that switches on the Notch receptor by cutting it. When Notch signaling is out of balance, it can activate pathways that help tumors grow[1]. Most desmoid tumors in its trial carried a change in the CTNNB1 gene (81% of those tested) and some an APC change (21%)[1].
▸What are the side effects of Nirogacestat?
Ogsiveo has no boxed warning and no contraindications. In the DeFi trial, diarrhea affected 84% of patients (grade 3 in 16%), and ovarian toxicity, such as missed periods, early menopause or ovarian failure, affected 75% of women who could become pregnant; the label says the long-term effects on fertility have not been established and that these effects may continue after stopping[1]. Other warnings are liver enzyme rises (ALT in 30%, AST in 33%), new non-melanoma skin cancers (squamous cell in 2.9%, basal cell in 1.4%), low phosphate (65%) and low potassium (22%), severe allergic reactions reported after approval, and harm to an unborn baby[1]. Other common side effects were rash (68%), nausea (54%), fatigue (54%), mouth sores (39%), headache (30%), abdominal pain (22%), cough (20%), hair loss (19%), upper respiratory infection (17%) and shortness of breath (16%), and 20% of patients stopped Ogsiveo because of a side effect[1].
▸How is Nirogacestat taken?
The dose is 150mg by mouth twice a day, with or without food, until the tumor progresses or side effects become unacceptable[1]. Tablets are swallowed whole and never broken, crushed or chewed. After vomiting or a missed dose, the next dose is taken at its usual time. For several severe side effects the drug is paused and restarted at 100mg twice a day[1].
▸Is Nirogacestat FDA approved?
Yes, Nirogacestat (Ogsiveo) is FDA approved (2023) for the treatment of Desmoid Tumors.
▸Does Ogsiveo affect fertility?
It can. In the DeFi trial, ovarian toxicity, such as missed periods, early menopause or ovarian failure, occurred in 75% of women who could become pregnant, and the label says these effects may continue after stopping and that long-term effects on fertility have not been established[1].
Before starting: the label advises discussing the risk to fertility.
During treatment: doctors watch for changes in periods and for symptoms such as hot flashes, night sweats and vaginal dryness.
Pregnancy: Ogsiveo can harm an unborn baby, and the label advises effective contraception during treatment and for 1 week after the last dose.
Research: SpringWorks is studying Ogsiveo in women who have not gone through menopause (NCT07176689).
Source: Ogsiveo prescribing information, September 2026.
▸How well did Ogsiveo work in its trial?
In the DeFi trial of 142 adults with growing desmoid tumors, the tumor progressed in 17% of people on Ogsiveo and 51% on placebo[1].
Tumor shrinkage: 41% responded on Ogsiveo, including 7% whose tumors disappeared, against 8% on placebo.
Time on treatment: the median was 20.6 months.
Side effects: 20% stopped Ogsiveo because of a side effect, most often diarrhea, ovarian toxicity or liver enzyme rises.
Source: Ogsiveo prescribing information, September 2026.
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.
- SpringWorks Therapeutics via DailyMed · 2026-09-02. Ogsiveo (nirogacestat) tablets prescribing information. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f172e6ff-3190-41b0-b95a-58a7ef9e9e1e
- FDA · 2023-11-27. FDA approves nirogacestat for desmoid tumors. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-nirogacestat-desmoid-tumors
- FDA. Ogsiveo approval history. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=217677
- Merck KGaA, Darmstadt, Germany · 2025-07-01. Merck KGaA, Darmstadt, Germany completes acquisition of SpringWorks Therapeutics. https://www.emdgroup.com/en/news/springworks-acquisition-completed-01-07-2025.html
- SpringWorks Therapeutics. Ogsiveo patient support program. https://www.ogsiveo.com/patient-support-program/