Atebrioz

Atebrioz is used in fibrodysplasia ossificans progressiva (FOP) to reduce new abnormal bone growth outside of the skeleton (heterotopic ossification [HO]) in adults and children 12 years and older. FOP is a rare inherited condition in which bone gradually forms in soft tissues such as muscles, tendons, and ligaments. This abnormal bone growth is called heterotopic ossification.

Atebrioz is taken once daily and works by blocking ALK2, a receptor that is overactive in FOP, which helps limit how much new abnormal bone forms outside the skeleton.

Atebrioz (zilurgisertib) received FDA approval on September 25, 2026.

Atebrioz reduced the volume of new abnormal bone growth (heterotopic ossification) compared with placebo in a 24-week clinical trial of 63 people with FOP aged 12 years and older.

New bone growth was measured using whole-body CT scans (excluding the head) and included both growth of existing bone lesions and any new lesions. On average, the volume of new bone changed by -3.2 cm³ in people taking Atebrioz and increased by 24.6 cm³ in people taking placebo.

It is not known if Atebrioz is safe and effective in children younger than 12 years of age.

Serious side effects

Atebrioz can cause serious side effects, including:

• Harm to your unborn baby, including birth defects, if taken during pregnancy. Females who are pregnant must not take Atebrioz. Females who can become pregnant or plan to become pregnant: Your healthcare provider will ask you to take a pregnancy test before starting treatment with Atebrioz to verify that you are not pregnant. Use effective birth control (contraception) during treatment with Atebrioz and for 1 week after the last dose of Atebrioz. Talk to your healthcare provider about birth control methods that may be right for you. If you become pregnant or think you may be pregnant during treatment with Atebrioz, stop taking Atebrioz immediately and call your healthcare provider right away.

• Take Atebrioz exactly as your healthcare provider tells you.
• Do not change your dose or stop taking Atebrioz without first talking to your healthcare provider.
• Take Atebrioz 1 time each day with or without food.
• For people who are unable to swallow whole tablets, Atebrioz may be crushed and mixed in 4 tablespoons of water, orange juice, applesauce, or plain yogurt. Do not take Atebrioz with grapefruit, pomelo, or juices containing these fruits.

• Avoid becoming pregnant while taking Atebrioz. (See "What is the most important information I should know about Atebrioz?")
• Do not breastfeed while taking Atebrioz. (See "Before you take Atebrioz, tell your healthcare provider about all of your medical conditions, including if you:")

Do not take Atebrioz if you are pregnant. (See "What is the most important information I should know about Atebrioz?", above).

Before you take Atebrioz, tell your healthcare provider about all of your medical conditions, including if you:

• are breastfeeding or plan to breastfeed. It is not known if Atebrioz passes into your breast milk. Breastfeeding is not recommended during treatment with Atebrioz and for at least 1 week after the last dose of Atebrioz. Talk to your healthcare provider about the best way to feed your baby during this time.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Atebrioz and certain other medicines can interact with each other, sometimes causing serious side effects.

Know the medicines you take. Keep a list of them to show to your healthcare provider and pharmacist when you get a new medicine.

Atebrioz may cause serious side effects, including: "What is the most important information I should know about Atebrioz?" above.

The most common side effects of Atebrioz include:

• headache
• joint pain (arthralgia)
• common cold, sinus infections, or sore throat (upper respiratory tract infections)
• nosebleed (epistaxis)
• nausea.

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

How common are Atebrioz side effects?

The table below shows side effects reported in at least 10% of people taking Atebrioz, and more often than with placebo, during the 24-week clinical trial.

Less common side effects included gastroenteritis, gastroesophageal reflux disease, iron deficiency anemia and rash (3 people each), and hair loss (alopecia) (2 people). None of these were reported with placebo.

Atebrioz contains zilurgisertib, an activin receptor-like kinase-2 (ALK2) inhibitor. FOP is caused by a change (mutation) in the ACVR1 gene, which makes the ALK2 receptor. In people with FOP, ALK2 is switched on all the time, which causes abnormal bone growth outside of the skeleton. Zilurgisertib blocks both normal ALK2 and the mutated form (R206H) that causes FOP. This reduces ALK2 signaling and reduces the formation of new bone.

Zilurgisertib has an elimination half-life of about 27.4 hours, and Atebrioz is taken once a day.

• Store Atebrioz tablets between 68°F and 77°F (20°C and 25°C) in the original container.
• Keep Atebrioz and all medicines out of reach of children.

Active ingredient: zilurgisertib

Inactive ingredients: colloidal silicon dioxide, crospovidone, magnesium stearate, mannitol, and microcrystalline cellulose. The tablet coating contains polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.