- Expanded dosing options support individualized treatment for adults with XLH
PRINCETON, N.J., May 14, 2026 (GLOBE NEWSWIRE) -- Kyowa Kirin, Inc., a wholly owned subsidiary of Kyowa Kirin Co. Ltd., today announced the U.S. Food and Drug Administration (FDA) has approved a dosing update to the CRYSVITA (burosumab-twza) Prescribing Information for adults living with X-linked hypophosphatemia (XLH), a rare, progressive, genetic disease that impacts the bones and muscles in both children and adults. Healthcare providers now have the option to increase the dose and frequency of CRYSVITA for patients whose serum phosphorus is below the normal range after the initial treatment period. These patients may be transitioned to a dosage of 0.5 mg/kg, not to exceed 90 mg, once every 2 weeks. If further dosage increase is needed after 4 weeks of treatment with 0.5 mg/kg every 2 weeks, the dosage can be increased to 1 mg/kg, not to exceed 90 mg, administered every 2 weeks.
"Kyowa Kirin is committed to delivering solutions that make a meaningful difference for people living with XLH. As the only FDA-approved treatment for XLH, CRYSVITA plays a critical role in care, and it's essential that clinicians have the flexibility to support optimal patient outcomes," said Richard Wilson, Senior Vice President, Rare Disease Franchise Head. "While most adults with XLH maintain normal serum phosphorus levels with CRYSVITA administered every four weeks, this update enables a more personalized approach for those who need additional support to reach and maintain serum phosphorus levels within normal range."
To review the new dosing guidance, please see the full Prescribing Information for CRYSVITA, Section 2.3 (Recommended Dosage for Adult Patients with X-linked Hypophosphatemia, 18 years of age and older).
About X-linked hypophosphatemia
X-linked hypophosphatemia is a rare, lifelong, genetic disease that can impact the bones and muscles in both children and adults. In individuals with XLH, the body doesn't hold on to enough phosphorus, which is an essential mineral for bone health. This is due to the production of excess fibroblast growth factor 23 (FGF23), causing the body to release too much phosphorus through the urine. When phosphorus levels are too low (hypophosphatemia), it can cause the softening and weakening of growing bones in children (rickets) and of mature bones in children and adults (osteomalacia).
About CRYSVITA (burosumab-twza) Injection
CRYSVITA is a recombinant, fully human monoclonal IgG1 antibody, discovered by Kyowa Kirin, which binds to and inhibits the biological activity of FGF23, the underlying cause of hypophosphatemia in XLH. By blocking FGF23, CRYSVITA helps to restore renal phosphorus reabsorption and increase the serum concentration of active vitamin D.
U.S. CRYSVITA Indication
CRYSVITA is a fibroblast growth factor (FGF23) blocking antibody indicated for the treatment of X-linked hypophosphatemia (XLH) in adult and pediatric patients 6 months of age and older.
Important Safety Information
CONTRAINDICATIONS
CRYSVITA is contraindicated:
In concomitant use with oral phosphate and/or active vitamin D analogs (e.g., calcitriol, paricalcitol, doxercalciferol, calcifediol) due to the risk of hyperphosphatemia.
When serum phosphorus is within or above the normal range for age.
In patients with severe renal impairment or end stage renal disease because these conditions are associated with abnormal mineral metabolism.
WARNINGS AND PRECAUTIONS
Hypersensitivity
Hypersensitivity reactions (e.g., rash, urticaria) have been reported in patients with CRYSVITA. Discontinue CRYSVITA if serious hypersensitivity reactions occur and initiate appropriate medical treatment.
Hyperphosphatemia and Risk of Nephrocalcinosis
Increases in serum phosphorus to above the upper limit of normal may be associated with an increased risk of nephrocalcinosis. For patients already taking CRYSVITA, dose interruption and/or dose reduction may be required based on a patient's serum phosphorus levels.
Hypercalcemia
Increases in serum calcium have been reported in patients treated with CRYSVITA. Patients with risk factors such as pre-existing hyperparathyroidism, prolonged immobilization, dehydration, hypervitaminosis D, or renal impairment, are at higher risk of hypercalcemia. Monitor these patients for serum calcium and parathyroid hormone levels before and during CRYSVITA treatment for moderate to severe hypercalcemia. In patients with moderate to severe hypercalcemia, CRYSVITA should not be administered until hypercalcemia is adequately managed.
Injection Site Reactions
Administration of CRYSVITA may result in local injection site reactions. Discontinue CRYSVITA if severe injection site reactions occur and administer appropriate medical treatment.
ADVERSE REACTIONS
Pediatric Patients
Adverse reactions reported in 10% or more of CRYSVITA-treated pediatric XLH patients across three studies are: pyrexia (55%, 44%, and 62%), injection site reaction (52%, 67%, and 23%), cough (52%), vomiting (41%, 48%, and 46%), pain in extremity (38%, 46%, and 23%), headache (34% and 73%), tooth abscess (34%, 15%, and 23%), dental caries (31%), diarrhea (24%), vitamin D decreased (24%, 37%, and 15%), toothache (23% and 15%), constipation (17%), myalgia (17%), rash (14% and 27%), dizziness (15%), and nausea (10%).
Adult Patients
Adverse reactions reported in more than 5% of CRYSVITA-treated adult XLH patients and in at least 2 patients more than placebo in one study are: back pain (15%), headache (13%), tooth infection (13%), restless legs syndrome (12%), vitamin D decreased (12%), dizziness (10%), constipation (9%), muscle spasms (7%), and blood phosphorus increased (6%).
Spinal stenosis is prevalent in adults with XLH, and spinal cord compression has been reported. It is unknown if CRYSVITA therapy exacerbates spinal stenosis or spinal cord compression.
USE IN SPECIFIC POPULATIONS
There are no available data on CRYSVITA use in pregnant women to inform a drug-associated risk of adverse developmental outcomes. Serum phosphorus levels should be monitored throughout pregnancy. Report pregnancies to the Kyowa Kirin, Inc. Adverse Event reporting line at 1-844-768-3544.
There is no information regarding the presence of CRYSVITA in human milk or the effects of CRYSVITA on milk production or the breastfed infant. Therefore, the developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for CRYSVITA and any potential adverse effects on the breastfed infant from CRYSVITA or from the underlying maternal condition.
PATIENT COUNSELING INFORMATION
Advise patients not to use any oral phosphate and/or active vitamin D analog products.
Instruct patients to contact their physician if hypersensitivity reactions, injection site reactions, and restless legs syndrome induction or worsening of symptoms occur.
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 full Prescribing Information for CRYSVITA.
About Kyowa Kirin
Kyowa Kirin aims to discover and deliver novel medicines and treatments with life-changing value. As a Japan-based Global Specialty Pharmaceutical Company, Kyowa Kirin has invested in drug discovery and biotechnology innovation for more than 70 years and is currently working to engineer the next generation of antibodies and cell and gene therapies with the potential to help patients with high unmet medical needs, such as bone & mineral, intractable hematological diseases/hemato-oncology and rare diseases. A shared commitment to Kyowa Kirin's values, to sustainable growth, and to making people smile unites Kyowa Kirin across the globe. You can learn more about the business of Kyowa Kirin at www.kyowakirin.com.
