Kyowa Kirin expands FDA-approved use of Crysvita for adults with XLH

JAPAN—Kyowa Kirin has received US Food and Drug Administration approval to update the prescribing information for Crysvita (burosumab-twza), expanding dosing flexibility for adults living with X-linked hypophosphataemia (XLH).

The decision provides clinicians with an additional pathway to manage patients whose serum phosphorus levels remain below normal despite initial therapy.

 XLH is a rare, progressive genetic disorder that affects both children and adults, weakening bone structure and muscle function due to impaired phosphate retention.

Adjusted dosing for improved patient control

Under the revised guidance, healthcare providers can adjust Crysvita dosing based on patient response and laboratory results.

Patients who do not achieve normal serum phosphorus levels after initial treatment may transition to a 0.5 mg/kg dose, not exceeding 90 mg, administered every two weeks.

If further clinical improvement is required after four weeks, the dose may be increased to 1 mg/kg every two weeks, with the same maximum limit of 90 mg.

This structured flexibility allows physicians to fine-tune therapy while maintaining safety parameters and closely monitoring biochemical response.

Targeted mechanism supporting bone health

Crysvita is a recombinant, fully human monoclonal immunoglobulin G1 (IgG1) antibody designed to inhibit fibroblast growth factor 23 (FGF23), a key driver of hypophosphataemia in XLH.

By blocking FGF23 activity, the therapy restores renal phosphate reabsorption and increases active vitamin D levels, which are both essential for maintaining bone strength and metabolic balance.

The treatment is approved in the United States for adults and pediatric patients aged six months and older, making it one of the few targeted therapies available for this condition.

Company perspective on personalized care

Kyowa Kirin senior vice-president and head of the rare disease franchise, Richard Wilson, stated that the company remains committed to advancing therapies that improve outcomes for people living with XLH.

He noted that Crysvita already plays a central role in treatment as the only FDA-approved therapy for the condition, and emphasized that updated dosing options give clinicians greater flexibility to support individualized patient care.

He further highlighted that while many adults maintain stable phosphorus levels with dosing every four weeks, some patients require closer adjustment to achieve optimal control.

Broader rare disease pipeline developments

In a separate regulatory milestone, Japan’s Ministry of Health, Labour and Welfare granted orphan regenerative medicine designation in October 2025 to Kyowa Kirin and Orchard Therapeutics’ ex vivo autologous haematopoietic stem cell gene therapy OTL-200 for metachromatic leukodystrophy (MLD).

The recognition reflects ongoing efforts to accelerate innovation in rare and genetic diseases, aligning with the company’s broader focus on cell and gene therapies.