How CRYSVITA works

CRYSVITA is a prescription medicine used to treat adults and children 6 months of age and older with X-linked hypophosphatemia, or XLH.

When a person has X-linked hypophosphatemia, or XLH, the levels of phosphorus in their body are very low.

Phosphorus is a mineral that is important to the health and function of bones, muscles, and teeth. Having too little phosphorus—a condition known as hypophosphatemia—can cause bones to soften and weaken over time, leading to conditions such as rickets in children and osteomalacia in adults.

Under normal conditions, a protein called fibroblast growth factor 23, or FGF23, helps maintain just the right amount of phosphorus in the body.

In XLH, FGF23 activity is increased, leading to low levels of phosphorus.

CRYSVITA is an antibody that blocks FGF23. By keeping FGF23 activity in check, CRYSVITA restores phosphorus absorption in the kidneys. Phosphorus can then be deposited into bones, making them stronger and healthier.

Ask your doctor if CRYSVITA is right for you or your child.

What is CRYSVITA?

CRYSVITA is a prescription medicine used to treat adults and children 6 months of age and older with X-linked hypophosphatemia (XLH).

Important Safety Information

You should not take CRYSVITA if:

• You take an oral phosphate supplement and/or a specific form of vitamin D supplement (such as calcitriol, paricalcitol, doxercalciferol, calcifediol).
• Your phosphorus levels from a blood sample are within or above the normal range for age.
• You have kidney problems.

What is the most important information you should know about CRYSVITA?

• Some patients developed allergic reactions (e.g., rash and hives) while taking CRYSVITA. Your doctor will monitor you for symptoms of an allergic reaction while you are taking CRYSVITA. Your treatment may need to be discontinued for serious allergic reactions.
• High levels of phosphorus in the blood have been reported in some patients taking CRYSVITA. This may be related to a risk of high calcium levels in the kidneys. Your doctor will collect blood samples to monitor your levels. If you are already taking CRYSVITA, dose interruption and/or dose reduction may be required based on your serum phosphorus levels.
• High levels of calcium in the blood have been reported in patients taking CRYSVITA. The risk is greater in patients with pre-existing hyperparathyroidism (overactive parathyroid glands), for those who are unable to move for extended periods of time, become dehydrated, have high vitamin D levels, or have kidney issues. If you are at greater risk, your doctor will monitor your blood calcium and parathyroid hormone levels before you start and while taking CRYSVITA. If you develop high levels of blood calcium, your doctor may need to stop your treatment until it is adequately managed.
• Administration of CRYSVITA may result in reactions at the injection site, such as hives, reddening of the skin, rash, swelling, bruising, pain, severe itching of the skin, and collection of blood outside of a blood vessel (i.e., hematoma). Call your doctor if you develop an injection site reaction. CRYSVITA may be discontinued if severe injection site reactions occur.

What are the possible side effects of CRYSVITA?

• Adverse reactions that were seen in children with XLH are:
  • Fever
  • Injection site reaction
  • Cough
  • Vomiting
  • Pain in arms and legs
  • Headache
  • Tooth abscess
  • Dental cavities
  • Diarrhea
  • Decreased vitamin D levels
  • Toothache
  • Constipation
  • Muscle pain
  • Rash
  • Dizziness
  • Nausea
• Adverse reactions that were seen in adults with XLH are:
  • Back pain
  • Headache
  • Tooth infection
  • Restless legs syndrome
  • Decreased vitamin D levels
  • Dizziness
  • Constipation
  • Muscle spasms
  • Phosphorus levels increased in the blood
• Narrowing of the spaces within the spine is common in adults with XLH, and pressure on the spinal cord has been reported in adults taking CRYSVITA. It is not known if taking CRYSVITA worsens the narrowing of the spaces within the spine or the pressure on the spinal cord.

Before taking CRYSVITA, tell your doctor about all of your medications (including supplements) and medical conditions, including if you: 

• Are taking oral phosphate and/or active vitamin D (such as calcitriol, paricalcitol, doxercalciferol, calcifediol). 
• Are pregnant, think you may be pregnant, or plan to become pregnant. There is not enough experience to know if CRYSVITA may harm your unborn baby. Report pregnancies to the Kyowa Kirin, Inc. Adverse Event reporting line at 1-844-768-3544. 
• Are breastfeeding or plan to breastfeed. There is not enough experience to know if CRYSVITA passes into your breast milk. Talk with your doctor about the best way to feed your baby while you receive CRYSVITA. 

While taking CRYSVITA, tell your doctor if you experience: 

• An allergic reaction such as rash or hives 
• A rash, swelling, bruising, or other reaction at the injection site 
• New or worsening restless legs syndrome 

These are not all the possible side effects of CRYSVITA. Call your doctor for medical advice about side effects. 

You may report side effects to the FDA at (800) FDA-1088 or www.fda.gov/medwatch. You may also report side effects to Kyowa Kirin, Inc. at 1-844-768-3544.

For important risk and use information, please see the accompanying full Prescribing Information for CRYSVITA.