When a desmoid tumor grows or returns, deciding on an effective treatment can be challenging. Nirogacestat (Ogsiveo), an oral medication that was approved by the U.S. Food and Drug Administration (FDA) for adults with progressing desmoid tumors, is one option.

This treatment option has raised questions for people living with desmoid tumors and their families. Read on to learn what researchers and doctors know about nirogacestat, who may benefit from the therapy, and possible side effects of this treatment.

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How Does Nirogacestat Differ From Other Targeted Therapy?

In cancer treatment, targeted therapy refers to medicine that stops the molecular pathways that make cancer grow. Desmoid tumors are soft-tissue tumors that are considered benign (not cancerous) and don’t spread to other parts of the body.

However, desmoid tumors can grow into nearby tissues and cause pain and other health complications. This is why certain medicines used to treat cancer can also help treat desmoid tumors.

Until nirogacestat, no targeted therapies were specifically FDA-approved to treat desmoid tumors. Targeted therapies approved for other conditions are sometimes used to treat desmoid tumors. This practice of prescribing a drug for a different use from its FDA-approved use is called off-label prescribing.

Who Might Benefit From Using Nirogacestat?

Nirogacestat is approved for adults who need systemic therapy — such as chemotherapy, immunotherapy, or targeted therapy — because their desmoid tumors are progressing. The growing tumors may be causing painful symptoms or other complications.

What Do Clinical Trials Show?

A clinical trial performed by researchers from around the world showed that nirogacestat slows desmoid tumor growth. The New England Journal of Medicine published the results of this phase 3 clinical trial, known as the Desmoid Fibromatosis (DeFi) trial, in 2023.

The DeFi trial involved 142 people with desmoid tumors. Half the participants received nirogacestat, and the other half got a placebo (a nonmedicated pill), twice a day until their disease progressed or they dropped out because of drug side effects.

Tumors Didn’t Get Worse and Actually Shrunk

The study found that nirogacestat led to less desmoid tumor progression and more improvement in people with desmoid tumors. After two years, people who took nirogacestat had a 71 percent lower risk of their tumor getting worse compared with people who took the placebo.

Also, about 41 percent of people taking nirogacestat had their tumors shrink or improve, compared to 8 percent of people taking the placebo.

People Felt Better Taking Nirogacestat

Participants took surveys on how they felt before, during, and after treatment. People who took nirogacestat consistently reported feeling better compared with people who received the placebo. Specifically, people taking nirogacestat reported:

• Experiencing less tumor pain
• Being more able to physically function
• Having a better quality of life

Benefits Remained With Continued Treatment

Long-term follow-up with people from the DeFi trial lasted for up to four years. This extended follow-up revealed that the benefits continued with ongoing treatment.

At least half of the people receiving nirogacestat did not have disease progression by the end of the follow-up period. And the longer people took nirogacestat, the more they saw their tumors shrink or improve. About 46 percent of people had tumor improvement after four years of treatment.

What Are Nirogacestat’s Side Effects?

Like other drugs, nirogacestat can lead to side effects. The most common side effects reported for nirogacestat include:

• Gastrointestinal symptoms, such as nausea, vomiting, stomach pain (stomatitis), and diarrhea
• Headache
• Skin and hair changes, such as rash and hair loss
• Breathing symptoms, such as cough, shortness of breath, and upper respiratory infections
• Mouth sores
• Ovarian toxicity (problems with the ovaries)

The long-term results of the DeFi trial showed that side effects generally improved over time as treatment continued.

Who Shouldn’t Take Nirogacestat?

Nirogacestat may not be an option for everyone. If you’re pregnant, you shouldn’t take nirogacestat because it can harm a developing baby. If you can become pregnant, your doctor may check to make sure you’re not pregnant before you start treatment.

Effective birth control is also necessary while taking nirogacestat and for one week after your final dose, if you or your partner can become pregnant.

Researchers do not know whether nirogacestat passes into breastmilk or how it may affect a breastfed baby. You shouldn’t breastfeed while taking nirogacestat and for one week after your final dose.

Before starting treatment, tell your doctor or pharmacist about all medicines, vitamins, and herbal supplements you’re taking so they can check for any possible interactions. Some medicines that affect CYP3A enzymes can change the amount of nirogacestat in your body. This change may affect how nirogacestat works or increase your risk of side effects.

Also, if you take antacids, take them at a different time from nirogacestat. Taking them at the same time can affect how your body absorbs nirogacestat. Doctors may recommend taking nirogacestat at least two hours before or two hours after taking antacids.

If you’re considering trying nirogacestat for your desmoid tumors, talk to your doctor. They’ll help you understand whether nirogacestat is right for you based on your overall health and treatment needs.