Crysvita® Approved Across the EU for Infants Living with X-Linked Hypophosphataemia
Kyowa Kirin EMEA, a wholly owned subsidiary of Kyowa Kirin Co., Ltd., has announced that the European Commission (EC) has approved an expanded indication for Crysvita® (burosumab), allowing the therapy to be used in infants aged one month to one year with X-linked hypophosphataemia (XLH) across all European Union (EU) and European Economic Area (EEA) member states. The regulatory decision represents a significant advancement in the treatment of one of the most challenging inherited metabolic bone disorders, enabling clinicians to begin therapy during the earliest stages of life when skeletal development is most vulnerable.
The expanded approval marks an important milestone for children born with XLH, a rare, lifelong genetic disease characterized by phosphate wasting that disrupts normal bone mineralization. By extending eligibility to infants as young as one month old, healthcare providers now have the opportunity to intervene earlier in the disease process, with the goal of reducing complications that often begin during infancy and continue throughout childhood and adulthood.
Earlier Treatment Opportunities for a Progressive Genetic Disease
X-linked hypophosphataemia is a rare inherited disorder caused by mutations in the PHEX gene, resulting in elevated levels of fibroblast growth factor 23 (FGF23). Increased FGF23 activity causes excessive phosphate loss through the kidneys while simultaneously reducing active vitamin D production. Since phosphate is essential for healthy bone formation, persistent phosphate deficiency leads to defective mineralization of bones and teeth.
Although XLH is present from birth, many clinical symptoms become increasingly evident during infancy and early childhood. Without appropriate treatment, affected children may develop bowed legs, skeletal deformities, delayed growth, impaired mobility, bone pain, dental abnormalities, and muscle weakness. As the disease progresses, patients frequently experience lifelong orthopedic complications, chronic pain, reduced physical function, and diminished quality of life.
Because skeletal development occurs rapidly during infancy, medical experts have increasingly emphasized the importance of diagnosing and treating XLH as early as possible. The European Commission’s latest approval reflects this evolving clinical understanding and recognizes that intervention before significant skeletal damage develops may improve long-term outcomes.
Expanding Access Across Europe
The new indication authorizes Crysvita for infants between one month and one year of age throughout all EU and EEA countries. Previously, treatment options for this youngest patient population were limited, leaving physicians to manage the disease primarily through conventional phosphate supplementation and active vitamin D analogs before patients became eligible for targeted therapy.
The expanded approval provides clinicians with an evidence-based treatment option specifically designed to address the underlying biological mechanism responsible for XLH rather than simply managing phosphate deficiency.
Healthcare providers across Europe can now incorporate burosumab into treatment strategies at an earlier stage, potentially reducing disease progression before irreversible skeletal complications occur.
Addressing the Underlying Cause of XLH
Crysvita (burosumab) is a monoclonal antibody that specifically targets fibroblast growth factor 23 (FGF23), the hormone primarily responsible for phosphate wasting in XLH.
Rather than replacing phosphate alone, burosumab works by neutralizing excess FGF23 activity. This mechanism helps restore phosphate reabsorption by the kidneys while increasing active vitamin D production. The resulting improvements in phosphate balance support healthier bone mineralization and more normal skeletal development.
This targeted therapeutic approach distinguishes Crysvita from conventional treatment strategies, which typically require multiple daily doses of oral phosphate supplements combined with active vitamin D therapy and may be associated with treatment burden and variable effectiveness.
By correcting the biological pathway driving disease progression, burosumab offers a more precise therapeutic strategy aimed at addressing the root cause of XLH.
Supporting Evidence from Clinical Research
The European Commission based its approval on clinical evidence generated by the BUR-CL207 study (NCT04188964), a Phase 1/2, open-label, multicenter clinical trial evaluating burosumab in pediatric patients from birth through one year of age.
The study investigated several important clinical endpoints, including:
- Safety and tolerability
- Pharmacokinetics
- Treatment efficacy
- Overall clinical response in infants with XLH
The results demonstrated that the safety profile observed in infants was consistent with the already established safety profile of burosumab in older pediatric populations.
The findings provided regulators with confidence that treatment could safely be extended to younger patients while maintaining a benefit-risk profile comparable to previous clinical experience.
Importantly, the study contributes valuable evidence regarding therapeutic intervention during one of the earliest stages of disease progression.
Building on Earlier Regulatory Momentum
The European Commission’s decision follows a positive recommendation issued in April 2026 by the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP).
CHMP opinions represent a critical step in the European regulatory process, as the committee evaluates scientific evidence regarding a medicine’s quality, safety, and efficacy before recommending approval to the European Commission.
Following review of the BUR-CL207 clinical data, CHMP concluded that extending the indication to include infants was supported by sufficient scientific evidence.
The Commission’s final authorization now formalizes that recommendation across all participating European countries.
Company Perspective
Commenting on the expanded approval, Myriam Hakim, Regional Franchise Head at Kyowa Kirin EMEA, highlighted the significance of making treatment available earlier in life.
She noted that families often begin confronting the effects of XLH within the first months after birth, making early intervention particularly meaningful. According to Hakim, allowing healthcare professionals to initiate burosumab therapy from one month of age creates new opportunities to address disease progression before significant skeletal complications develop.
She emphasized that the expanded indication represents meaningful progress not only for infants diagnosed with XLH but also for parents and caregivers navigating the challenges of managing a rare genetic disorder.
Expert View on Early Intervention
Medical experts specializing in pediatric endocrinology and rare bone diseases have increasingly recognized the importance of initiating treatment before substantial skeletal abnormalities emerge.
Professor Agnès Linglart of AP-HP and Paris Saclay University emphasized that XLH is inherently progressive, with disease manifestations often beginning during infancy.
She explained that earlier access to evidence-based therapy offers physicians an opportunity to intervene while skeletal development remains highly active, potentially reducing long-term disease burden and improving future physical function.
According to Professor Linglart, the approval represents an important advancement in the clinical management of infants affected by XLH by enabling treatment during the earliest stages of disease.
Importance of Early Diagnosis
The expanded indication also reinforces the importance of early diagnosis.
Because XLH is inherited, children born into affected families may undergo genetic testing or receive clinical evaluation shortly after birth. Earlier therapeutic availability increases the value of timely diagnosis, allowing physicians to begin targeted treatment before significant complications become established.
This shift toward proactive disease management aligns with broader trends in rare disease care, where advances in genetics, newborn screening initiatives, and precision medicine increasingly support intervention before irreversible organ damage occurs.
Strengthening Long-Term Patient Care
Early therapeutic intervention may offer several potential long-term advantages, including improved skeletal mineralization, healthier growth trajectories, reduced orthopedic complications, enhanced mobility, and better physical development throughout childhood.
Although continued long-term follow-up remains important, expanding access during infancy gives clinicians additional opportunities to influence disease progression during a critical developmental window.
The approval therefore represents not only a regulatory milestone but also an important evolution in the standard of care for pediatric XLH management.
Extension of Orphan Market Exclusivity
In addition to expanding the approved patient population, the European Commission’s decision provides Crysvita with an additional two years of orphan market exclusivity within the European Union.
The regulatory protection for the medicine will now extend from February 2028 through February 2030.
Orphan drug exclusivity serves as an important incentive for pharmaceutical companies developing therapies for rare diseases, helping encourage continued investment in research, clinical development, manufacturing, and post-marketing studies despite relatively small patient populations.
The extension further strengthens Kyowa Kirin’s position in the rare disease market while supporting continued innovation for individuals living with XLH.
The European Commission’s approval represents a significant advancement in pediatric rare disease treatment by allowing Crysvita to be administered to infants from one month of age. Supported by clinical evidence demonstrating an acceptable safety profile and regulatory endorsement from the European Medicines Agency, the expanded indication enables physicians across Europe to intervene earlier in the course of X-linked hypophosphataemia.
As understanding of XLH continues to evolve, early diagnosis and targeted treatment are increasingly viewed as critical components of disease management. By extending access to younger patients, Kyowa Kirin aims to support earlier intervention, reduce the long-term impact of skeletal complications, and improve outcomes for children living with this rare inherited disorder. The approval also reinforces the growing role of precision therapies in rare metabolic bone diseases while highlighting ongoing efforts to bring innovative treatments to patients at the earliest possible stage of disease progression.
About CRYSVITA® (burosumab)
Burosumab is a recombinant human monoclonal antibody that binds to the protein fibroblast growth factor 23 (FGF23). This has the impact of inhibiting the action of FGF23, allowing phosphate regulation in the body to be restored.2
Following the latest approval, burosumab is authorised in the European Union for the treatment of XLH in infants from 1 month to 1 year of age with hypophosphataemia, children and adolescents aged 1 to 17 years with radiographic evidence of bone disease, and adults.
In 2018, the European Commission granted a conditional marketing authorisation for burosumab for the treatment of XLH with radiographic evidence of bone disease in children one year of age and older and in adolescents with growing skeletons.2 Following this, the European Commission granted burosumab a conditional marketing authorisation in 2020, for the treatment of adolescents regardless of growth status and adults with XLH.3 The licence was then converted from a conditional to a full standard marketing authorisation in 2022.2
Burosumab is now reimbursed in several European countries for both paediatric and adult XLH populations, including France, Germany, Italy, Spain and the UK.
Burosumab received European Commission approval in tumour induced osteomalacia (TIO) in August 2022 and is indicated for the treatment of FGF23-related hypophosphatemia in TIO associated with phosphaturic mesenchymal tumours that cannot be curatively resected or localised in children and adolescents aged 1 to 17 years and in adults.4
About X-linked Hypophosphataemia (XLH)
XLH is caused by a genetic mutation which leads to overexpression of the protein FGF23, a protein involved in the regulation of phosphate concentration in the blood. In XLH, FGF23 is produced in excess leading to depletion of phosphate in the blood, known as hypophosphataemia.5
Individuals living with the disease may display a multitude of symptoms including short stature, limb deformities, bone and joint pain, oral abscesses, and hearing loss.6 To manage this wide variety of symptoms, the disease is managed through multi-disciplinary teams.7
About Kyowa Kirin
Kyowa Kirin aims to discover novel medicines with life-changing value. As a Japan-based global specialty pharmaceutical company, we have invested in drug discovery and biotechnology innovation for more than 75 years and are currently working to engineer the next generation of antibodies and cell and gene therapies with the potential to help patients affected by severe and rare diseases. A shared commitment to our values, to sustainable growth, and to making people smile unites us across our four regions—Japan, Asia Pacific, North America, and EMEA/International.