CRYSVITA: Uses, Dosage & Side Effects
A human monoclonal antibody targeting FGF23 for the treatment of X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO)
CRYSVITA (burosumab) is a first-in-class human monoclonal antibody that targets fibroblast growth factor 23 (FGF23). It is approved for the treatment of X-linked hypophosphatemia (XLH) in patients aged 1 year and older, and for tumor-induced osteomalacia (TIO) in patients whose tumors cannot be located or surgically removed. By blocking excess FGF23, CRYSVITA restores phosphate balance and improves bone mineralization.
Quick Facts: CRYSVITA
Key Takeaways
- CRYSVITA is the first targeted therapy for X-linked hypophosphatemia (XLH), working by blocking excess FGF23 to restore phosphate levels in the blood.
- It is administered as a subcutaneous injection every 2 weeks in children (ages 1–17) and every 4 weeks in adults, with dosing based on body weight.
- Patients must stop oral phosphate supplements and active vitamin D analogues (e.g., calcitriol) before starting treatment, as combining them is contraindicated.
- Regular blood and urine monitoring of phosphate, calcium, and parathyroid hormone levels is essential throughout treatment to prevent complications.
- Clinical trials have demonstrated significant improvements in phosphate homeostasis, bone healing, rickets severity, and physical function in both children and adults with XLH.
What Is CRYSVITA and What Is It Used For?
Quick Answer: CRYSVITA (burosumab) is a human monoclonal antibody that blocks fibroblast growth factor 23 (FGF23) to increase phosphate levels in the blood. It is used to treat X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO/OOM) in patients where the causative tumor cannot be located or surgically removed.
CRYSVITA contains the active substance burosumab, a recombinant human immunoglobulin G1 (IgG1) monoclonal antibody produced in Chinese hamster ovary (CHO) cells. It represents a paradigm shift in the treatment of FGF23-mediated hypophosphatemic conditions, as it directly targets the underlying pathophysiology rather than merely supplementing the deficient mineral.
The medication received its first regulatory approval from the European Medicines Agency (EMA) in February 2018, followed by approval from the U.S. Food and Drug Administration (FDA) in April 2018 for pediatric patients with XLH. It has since received expanded indications for adult XLH and tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia (OOM).
X-Linked Hypophosphatemia (XLH)
X-linked hypophosphatemia (XLH) is the most common hereditary form of rickets and osteomalacia, affecting approximately 1 in 20,000 individuals worldwide. It is caused by loss-of-function mutations in the PHEX gene located on the X chromosome, which leads to overproduction of fibroblast growth factor 23 (FGF23). This excess FGF23 causes the kidneys to excrete too much phosphate in the urine, resulting in chronically low blood phosphate levels (hypophosphatemia).
The low phosphate levels in XLH lead to impaired bone mineralization, which manifests differently depending on age. In children and adolescents, XLH causes rickets — a condition characterized by bowed legs, knock knees, short stature, skeletal deformities, and dental abscesses. In adults, XLH leads to osteomalacia (softening of bones), causing bone pain, muscle weakness, stress fractures, joint stiffness, enthesopathy (calcification of tendons and ligaments), and progressive hearing loss.
Before CRYSVITA, the standard treatment for XLH involved oral phosphate supplements combined with active vitamin D analogues (calcitriol or alfacalcidol). While this approach could partially correct phosphate levels, it often caused gastrointestinal side effects, required multiple daily doses, and carried risks of nephrocalcinosis (calcium deposits in the kidneys) and secondary hyperparathyroidism.
Tumor-Induced Osteomalacia (TIO/OOM)
Tumor-induced osteomalacia (TIO), also referred to as oncogenic osteomalacia (OOM), is a rare paraneoplastic syndrome caused by small, typically benign mesenchymal tumors that secrete excessive amounts of FGF23. These tumors can be extremely difficult to locate, as they may be very small and occur anywhere in the body, including the bones, soft tissues, and nasal sinuses.
The excess FGF23 produced by these tumors causes the same biochemical disturbance as XLH — renal phosphate wasting and low blood phosphate levels. This leads to progressive bone softening, severe muscle weakness, fatigue, bone pain, and an increased risk of fractures. When the tumor can be identified and completely removed through surgery, the condition is typically cured. However, in many patients, the tumor either cannot be found or cannot be completely excised, necessitating long-term medical treatment.
How CRYSVITA Works
CRYSVITA binds specifically to FGF23 in the bloodstream, preventing it from interacting with its receptor complex (FGFR1c/Klotho) on the surface of kidney cells. By neutralizing excess FGF23, CRYSVITA increases tubular reabsorption of phosphate in the kidneys, raises the serum concentration of 1,25-dihydroxyvitamin D (the active form of vitamin D), and enhances intestinal absorption of phosphate and calcium. Together, these effects restore phosphate homeostasis and allow proper bone mineralization.
In clinical trials, CRYSVITA demonstrated significant increases in serum phosphate levels, improvements in rickets severity scores in children, enhanced bone healing, improved linear growth, and reductions in bone pain and fatigue in adults. The targeted mechanism of action provides a more physiologic correction of phosphate balance compared to traditional oral phosphate supplementation.
What Should You Know Before Taking CRYSVITA?
Quick Answer: CRYSVITA must not be used if you have hyperphosphatemia (high blood phosphate), severe kidney disease, or if you are taking phosphate supplements or active vitamin D analogues. Your doctor will perform regular blood tests to monitor your phosphate, calcium, and parathyroid hormone levels during treatment.
Contraindications
- You are allergic to burosumab or any other ingredient in CRYSVITA (L-histidine, D-sorbitol, polysorbate 80, L-methionine, hydrochloric acid, water for injections)
- You are taking oral phosphate supplements or active vitamin D analogues (such as calcitriol or alfacalcidol)
- You already have high phosphate levels in the blood (hyperphosphatemia)
- You have severe kidney disease or kidney failure
These contraindications exist for important safety reasons. Combining CRYSVITA with phosphate supplements or active vitamin D can lead to dangerously elevated phosphate and calcium levels in the blood, increasing the risk of ectopic mineralization — a condition where calcium and phosphate crystals deposit in soft tissues such as the kidneys, blood vessels, and other organs. In patients with severe kidney impairment, the drug cannot be safely eliminated and phosphate balance cannot be properly managed.
Allergic Reactions
- Skin rash and itching over the entire body
- Severe swelling of the eyelids, mouth, or lips (angioedema)
- Shortness of breath or difficulty breathing
- Rapid heartbeat or palpitations
- Excessive sweating
Hypersensitivity reactions, including serious allergic reactions, have been reported with CRYSVITA use. While most injection site reactions are mild and transient, healthcare providers should be prepared to manage anaphylaxis if it occurs. Patients who experience severe allergic reactions should not receive further doses of CRYSVITA.
Warnings and Precautions
Before and during treatment with CRYSVITA, your doctor will perform regular laboratory tests and monitoring. These include measurements of serum phosphate and calcium levels, urine calcium and phosphate excretion, serum parathyroid hormone (PTH) levels, and renal ultrasound examinations. This monitoring is essential to detect and manage several potential complications:
- Hyperphosphatemia: Elevated phosphate levels can occur if the dose is too high. Your doctor will adjust the dose based on regular fasting serum phosphate measurements, targeting levels within the lower end of the normal range.
- Hypercalcemia and hypercalciuria: Elevated calcium in the blood or urine can increase the risk of nephrocalcinosis (calcium deposits in the kidneys) and kidney stones.
- Ectopic mineralization: Excessive phosphate and calcium levels can lead to calcification of soft tissues, including the kidneys, blood vessels, and other organs.
- Hyperparathyroidism: Changes in parathyroid hormone levels may occur during treatment and require monitoring.
Children under 1 year of age should not receive CRYSVITA, as the safety and efficacy have not been studied in this age group. For children and adolescents, growth, dental health, and bone development should be monitored alongside laboratory parameters.
Pregnancy and Breastfeeding
CRYSVITA is not recommended during pregnancy because the effects on the developing baby have not been adequately studied. Women of childbearing potential should use effective contraception during treatment and for at least 14 weeks after the last dose. Discuss family planning with your doctor before starting treatment.
Monoclonal antibodies like CRYSVITA are known to cross the placenta, particularly during the third trimester. While animal studies have not shown direct harmful effects on reproductive function, the absence of controlled human data means that potential risks to the fetus cannot be excluded.
Regarding breastfeeding, monoclonal antibodies are known to pass into breast milk during the first few days after birth. However, after this initial period, CRYSVITA may be used during breastfeeding. This is because large protein molecules like monoclonal antibodies are likely degraded in the infant's gastrointestinal tract and are unlikely to be absorbed systemically. Discuss the benefits and risks of breastfeeding while on CRYSVITA with your healthcare provider.
Driving and Operating Machinery
Dizziness has been reported as a very common side effect of CRYSVITA. If you experience dizziness, you should avoid driving, cycling, operating machinery, or performing other activities that require alertness until the symptoms resolve.
Important Information About Excipients
CRYSVITA contains sorbitol (45.91 mg per vial), which is a source of fructose. If you have been diagnosed with hereditary fructose intolerance (HFI), a rare genetic condition, speak with your doctor before receiving this medication. CRYSVITA also contains polysorbate 80 (0.5 mg per vial), which can cause allergic reactions in some individuals. Inform your doctor if you have any known allergies to these excipients.
How Does CRYSVITA Interact with Other Drugs?
Quick Answer: CRYSVITA has critical contraindicated interactions with oral phosphate supplements and active vitamin D analogues (e.g., calcitriol). These must be discontinued before starting treatment. Calcimimetics may require closer calcium monitoring. No other clinically significant drug interactions have been identified.
Because burosumab is a monoclonal antibody, it is not metabolized by cytochrome P450 (CYP) enzymes and is therefore unlikely to interact with most conventional medications through traditional pharmacokinetic drug-drug interaction mechanisms. However, there are important pharmacodynamic interactions that must be considered due to CRYSVITA's effects on phosphate and calcium metabolism.
Contraindicated Combinations
| Medication | Interaction Type | Clinical Significance |
|---|---|---|
| Oral phosphate supplements | Contraindicated | Risk of hyperphosphatemia, ectopic mineralization, and nephrocalcinosis. Must be discontinued before starting CRYSVITA. |
| Active vitamin D analogues (calcitriol, alfacalcidol, paricalcitol) | Contraindicated | Risk of hypercalcemia, hypercalciuria, and ectopic mineralization. Must be stopped before treatment initiation. |
Interactions Requiring Monitoring
| Medication | Interaction Type | Clinical Significance |
|---|---|---|
| Calcimimetics (cinacalcet, etelcalcetide) | Monitor closely | These medications affect calcium signaling and may alter calcium levels. Your doctor may need to monitor calcium more frequently. |
| Inactive vitamin D supplements (cholecalciferol, ergocalciferol) | Generally safe | Non-active vitamin D supplements can usually be continued or started during CRYSVITA treatment. Your doctor will advise which specific products are appropriate. |
| Tumor treatments (radiation therapy, surgery) | Timing adjustment | In patients with TIO/OOM, CRYSVITA treatment should not begin until after tumor treatment is completed. If tumor treatment is needed during CRYSVITA therapy, the drug will be paused and restarted after treatment if phosphate levels remain low. |
It is important to note that the distinction between active and inactive vitamin D supplements is clinically significant. Active vitamin D analogues (calcitriol, alfacalcidol, paricalcitol) directly raise calcium and phosphate absorption and are contraindicated. In contrast, inactive vitamin D supplements (cholecalciferol, also known as vitamin D3, and ergocalciferol, known as vitamin D2) require hydroxylation in the liver and kidney before becoming active, and their use may be appropriate during CRYSVITA therapy at the discretion of the prescribing physician.
Always inform your healthcare provider about all medications, supplements, and herbal products you are taking before starting CRYSVITA, as well as any new treatments initiated during the course of therapy.
What Is the Correct Dosage of CRYSVITA?
Quick Answer: CRYSVITA dosage is based on body weight. Children aged 1–17 receive injections every 2 weeks, while adults receive injections every 4 weeks. The dose is adjusted based on regular fasting serum phosphate measurements. Maximum doses depend on the indication and age group.
CRYSVITA is administered as a subcutaneous injection into the upper arm, abdomen, buttock, or thigh. The injection may be given by a healthcare professional or, after appropriate training, self-administered by the patient or caregiver. The first self-administered injection after treatment initiation or any dose change should be performed under the supervision of a healthcare professional.
Dosing for Children and Adolescents (Ages 1–17)
Pediatric XLH Dosing
Starting dose: Approximately 0.8 mg/kg body weight, administered subcutaneously every 2 weeks.
Dose adjustments: Based on fasting serum phosphate levels, the dose may be increased in increments of 0.4 mg/kg up to approximately 2 mg/kg, not exceeding a maximum single dose of 90 mg.
Target: Fasting serum phosphate within the lower end of the normal reference range for age.
Pediatric TIO/OOM Dosing (Ages 1–12)
Dosing regimen: Same weight-based dosing as XLH, administered every 2 weeks.
Maximum single dose: 90 mg
Adolescent TIO/OOM Dosing (Ages 13–17)
Dosing regimen: Weight-based dosing, administered every 2 weeks.
Maximum single dose: 180 mg
Dosing for Adults
Adult XLH Dosing
Starting dose: Approximately 1 mg/kg body weight, administered subcutaneously every 4 weeks.
Maximum single dose: 90 mg
Dose adjustments: Based on fasting serum phosphate levels measured at specified intervals. The target is fasting serum phosphate within the lower end of the normal reference range.
Adult TIO/OOM Dosing
Starting dose: Approximately 0.5 mg/kg body weight, administered subcutaneously every 4 weeks.
Maximum single dose: 180 mg
Dose adjustments: Based on serum phosphate levels. The dose may be titrated up in increments to achieve target phosphate levels.
Dosing Summary Table
| Patient Group | Indication | Frequency | Max Single Dose |
|---|---|---|---|
| Children 1–12 years | XLH | Every 2 weeks | 90 mg |
| Adolescents 13–17 years | XLH | Every 2 weeks | 90 mg |
| Adults (≥18 years) | XLH | Every 4 weeks | 90 mg |
| Children 1–12 years | TIO/OOM | Every 2 weeks | 90 mg |
| Adolescents 13–17 years | TIO/OOM | Every 2 weeks | 180 mg |
| Adults (≥18 years) | TIO/OOM | Every 4 weeks | 180 mg |
Patients with Tumor-Induced Osteomalacia (TIO/OOM)
If you have TIO/OOM and require treatment for the underlying tumor (surgery or radiation therapy), your doctor will pause CRYSVITA treatment before the tumor procedure. After the tumor treatment is completed, your doctor will recheck your serum phosphate levels. CRYSVITA will only be restarted if phosphate levels remain low, indicating that the tumor has not been fully eliminated or that another tumor is present.
Missed Dose
If a dose of CRYSVITA is missed, contact your doctor immediately. The missed dose should be administered as soon as possible, and your doctor will determine the appropriate schedule for subsequent doses. Do not double the dose to make up for a missed injection.
Overdose
If you believe you have received too much CRYSVITA, contact your healthcare provider immediately. Overdose may lead to elevated serum phosphate levels (hyperphosphatemia), which can increase the risk of ectopic mineralization. There is no specific antidote for CRYSVITA overdose; management is supportive and may include monitoring of serum phosphate and calcium levels and temporary withholding of subsequent doses until levels normalize.
Self-Injection Instructions
If your doctor determines that you or your caregiver can administer CRYSVITA injections at home, proper training from a healthcare professional is required. Key points for self-injection include:
- Remove vials from the refrigerator 30 minutes before use and allow them to reach room temperature naturally. Do not heat them in warm water, a microwave, or direct sunlight.
- Inspect the solution visually before use. CRYSVITA should be clear to slightly opalescent, colorless to slightly brownish-yellow. Do not use if the solution is discolored, cloudy, or contains visible particles.
- Use a larger-gauge needle to withdraw the solution from the vial and switch to a thinner needle for injection.
- Rotate injection sites (abdomen, upper thighs, upper arms, or buttocks) to avoid repeated injections in the same location.
- Do not inject into areas that are tender, red, bruised, or damaged, or into stretch marks, scars, or birthmarks.
- Record the date, injection site, medication name, and batch number for each injection.
- Each vial is for single use only. Dispose of used needles, syringes, and vials in a sharps container according to local regulations.
What Are the Side Effects of CRYSVITA?
Quick Answer: The most common side effects of CRYSVITA include injection site reactions, headache, dizziness, dental problems, nausea, rash, muscle pain, and fever. In adults, restless legs syndrome and back pain are also very common. Serious but rare side effects include hypercalcemia and allergic reactions.
Like all medicines, CRYSVITA can cause side effects, although not everyone will experience them. The frequency and types of side effects differ between children/adolescents and adults, and also between XLH and TIO/OOM indications. Below is a comprehensive overview of reported side effects organized by frequency.
Side Effects in Children and Adolescents with XLH
Very Common
May affect more than 1 in 10 patients
- Tooth abscess (dental infection)
- Cough
- Headache
- Dizziness
- Vomiting
- Nausea
- Diarrhea
- Constipation
- Dental caries (tooth decay)
- Skin rash
- Muscle pain (myalgia) and pain in hands and feet
- Injection site reactions (redness, rash, pain, itching, swelling, bleeding, bruising)
- Fever
- Low vitamin D levels in blood
Common
May affect up to 1 in 10 patients
- Urticaria (hives)
- Increased parathyroid hormone levels in blood
Uncommon
May affect up to 1 in 100 patients
- High calcium levels in blood (hypercalcemia)
Not Known
Frequency cannot be estimated from available data
- High calcium levels in urine (hypercalciuria)
- Increased phosphate levels or high parathyroid hormone in blood
Side Effects in Adults with XLH and TIO/OOM
Very Common
May affect more than 1 in 10 patients
- Tooth abscess (dental infection)
- Headache
- Dizziness
- Restless legs syndrome (strong urge to move legs, especially at night)
- Constipation
- Back pain
- Muscle spasms (involuntary muscle twitching)
- Injection site reactions (pain, swelling)
- Low vitamin D levels in blood
Common
May affect up to 1 in 10 patients
- Increased or high parathyroid hormone levels in blood
- High calcium levels in blood or urine
- Skin rash
- Urticaria (hives)
- Increased phosphate levels in blood
Injection Site Reactions
Injection site reactions are among the most frequently reported side effects and may include redness, rash, pain, itching, swelling, bleeding, or bruising at the injection site. These reactions are generally mild to moderate in severity, typically appear within one day of the injection, and usually resolve within 1 to 3 days. Rotating injection sites and applying a cold compress after injection may help reduce these reactions.
Dental Side Effects
Dental complications, including tooth abscesses and dental caries, are very common in patients receiving CRYSVITA, particularly in the pediatric population. This is partly related to the underlying disease (XLH causes defective dentin and enamel formation) and partly to changes in mineral metabolism during treatment. Regular dental check-ups and good oral hygiene are recommended for all patients on CRYSVITA.
Contact your healthcare provider if you experience persistent or severe side effects, signs of allergic reactions (widespread rash, swelling of the face or throat, breathing difficulties), or if injection site reactions do not resolve within a few days. Regular monitoring blood tests will help your doctor detect and manage metabolic side effects such as elevated calcium or phosphate levels.
How Should You Store CRYSVITA?
Quick Answer: Store CRYSVITA in a refrigerator at 2°C to 8°C (36°F to 46°F). Do not freeze. Keep the vial in the outer carton to protect from light. Allow the vial to reach room temperature for 30 minutes before injection.
Proper storage of CRYSVITA is essential to maintain the medication's efficacy and safety. As a biologic product (monoclonal antibody), CRYSVITA is sensitive to temperature extremes, light, and physical agitation. Follow these storage guidelines carefully:
- Refrigerate: Store vials at 2°C to 8°C (36°F to 46°F) in a refrigerator. Do not store in the freezer compartment.
- Do not freeze: Freezing can damage the protein structure of the monoclonal antibody, rendering it ineffective or potentially harmful.
- Protect from light: Keep the vials in the original outer carton to protect from light exposure, which can degrade the active substance.
- Do not shake: Avoid shaking the vial, as this can cause protein aggregation and reduce the drug's effectiveness.
- Before use: Remove the vial from the refrigerator 30 minutes before injection to allow it to reach room temperature. Do not heat the vial using warm water, a microwave, or direct sunlight.
- Inspect before use: Check that the solution is clear to slightly opalescent and colorless to slightly brownish-yellow. Do not use if it contains visible particles or is discolored.
- Single use only: Each vial is intended for single use. Do not save unused medicine for future use or give it to others.
- Expiry date: Do not use after the expiry date printed on the carton and label. The expiry date refers to the last day of the stated month.
Keep CRYSVITA and all medicines out of sight and reach of children. Dispose of used vials, needles, and syringes in an appropriate sharps disposal container according to local regulations. Do not dispose of medicines via wastewater or household waste.
What Does CRYSVITA Contain?
Quick Answer: Each vial of CRYSVITA contains burosumab as the active substance (10 mg, 20 mg, or 30 mg per vial). Inactive ingredients include L-histidine, D-sorbitol, polysorbate 80, L-methionine, hydrochloric acid, and water for injections.
Active Substance
The active ingredient in CRYSVITA is burosumab, a recombinant human IgG1 monoclonal antibody directed against fibroblast growth factor 23 (FGF23). CRYSVITA is available in three vial strengths:
- 10 mg/mL — each vial contains 10 mg burosumab in 1 mL solution
- 20 mg/mL — each vial contains 20 mg burosumab in 1 mL solution
- 30 mg/mL — each vial contains 30 mg burosumab in 1 mL solution
Inactive Ingredients (Excipients)
| Excipient | Function | Amount per Vial |
|---|---|---|
| L-Histidine | Buffer (maintains pH stability) | Part of buffer system |
| D-Sorbitol (E 420) | Stabilizer / tonicity agent | 45.91 mg |
| Polysorbate 80 (E 433) | Surfactant (prevents protein aggregation) | 0.5 mg |
| L-Methionine | Antioxidant (protects protein stability) | Part of formulation |
| Hydrochloric acid (10%) | pH adjustment | As needed for pH |
| Water for injections | Solvent | To 1 mL |
Appearance and Packaging
CRYSVITA is a clear to slightly opalescent, colorless to slightly brownish-yellow solution for injection. It is supplied in single-use glass vials sealed with a rubber stopper and aluminum crimp seal. Each carton contains 1 vial. The medication is manufactured by Kyowa Kirin Holdings B.V. (Hoofddorp, Netherlands) and allphamed PHARBIL Arzneimittel GmbH (Gottingen, Germany).
Frequently Asked Questions About CRYSVITA
CRYSVITA (burosumab) is used to treat X-linked hypophosphatemia (XLH), the most common form of hereditary rickets, in patients aged 1 year and older. It is also approved for the treatment of tumor-induced osteomalacia (TIO/OOM) in children, adolescents, and adults when the causative tumor cannot be located or surgically removed. CRYSVITA works by blocking excess FGF23, a hormone that causes the kidneys to excrete too much phosphate, thereby restoring normal phosphate levels and improving bone health.
CRYSVITA is administered as a subcutaneous (under the skin) injection. In children and adolescents aged 1 to 17 years, it is given every 2 weeks. In adults, it is given every 4 weeks. The dose is calculated based on body weight. After proper training from a healthcare professional, patients or caregivers may administer the injection at home. Injection sites include the abdomen, upper thighs, upper arms, or buttocks, and should be rotated between injections.
No. Oral phosphate supplements and active vitamin D analogues (such as calcitriol) must be stopped before starting CRYSVITA treatment. Taking these medications together with CRYSVITA can cause dangerously high phosphate or calcium levels in the blood, leading to serious complications such as ectopic mineralization (calcium deposits in soft tissues like the kidneys). However, some inactive vitamin D supplements (such as cholecalciferol/vitamin D3) may be safe to continue — your doctor will advise you on this.
Regular monitoring is essential during CRYSVITA treatment. Your doctor will check fasting serum phosphate levels (to guide dosing), serum calcium levels, urine calcium and phosphate levels, serum parathyroid hormone (PTH) levels, and may perform renal ultrasound examinations to check for nephrocalcinosis. These tests help ensure that phosphate levels stay within the target range and that complications such as hypercalcemia or ectopic mineralization are detected early.
CRYSVITA has not been studied in children under 1 year of age and should not be used in this age group. The safety and efficacy data are based on clinical trials in patients aged 1 year and older. For infants with XLH, conventional treatment with oral phosphate supplements and active vitamin D remains the standard of care until the child is old enough for CRYSVITA therapy.
For XLH, treatment with CRYSVITA is typically long-term, as XLH is a chronic genetic condition that requires ongoing management. For TIO/OOM, treatment continues as long as the underlying tumor cannot be removed and serum phosphate levels remain low. If the tumor is successfully treated (through surgery or radiation), CRYSVITA may be discontinued if phosphate levels normalize. Your doctor will regularly assess whether continued treatment is needed.
References
- European Medicines Agency (EMA). CRYSVITA (burosumab) — Summary of Product Characteristics (SmPC). Last updated November 2025. Available at: www.ema.europa.eu/en/medicines/human/EPAR/crysvita
- U.S. Food and Drug Administration (FDA). CRYSVITA (burosumab-twza) — Prescribing Information. Revised 2024. Available at: www.accessdata.fda.gov
- Imel EA, Glorieux FH, Whyte MP, et al. Burosumab versus conventional therapy in children with X-linked hypophosphataemia: a randomised, active-controlled, open-label, phase 3 trial. Lancet. 2019;393(10189):2416-2427. doi:10.1016/S0140-6736(19)30654-3
- Portale AA, Carpenter TO, Brandi ML, et al. Continued Beneficial Effects of Burosumab in Adults with X-Linked Hypophosphatemia: Results from a 24-Week Treatment Continuation Period After a 24-Week Double-Blind Placebo-Controlled Period. Calcified Tissue International. 2019;105(3):271-284. doi:10.1007/s00223-019-00568-x
- Jan de Beur SM, Miller PD, Weber TJ, et al. Burosumab for the Treatment of Tumor-Induced Osteomalacia. Journal of Bone and Mineral Research. 2021;36(4):627-635. doi:10.1002/jbmr.4233
- Haffner D, Emma F, Eastwood DM, et al. Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia. Nature Reviews Nephrology. 2019;15(7):435-455. doi:10.1038/s41581-019-0152-5
- World Health Organization (WHO). WHO Model List of Essential Medicines — 23rd List, 2023. Geneva: World Health Organization; 2023.
- Carpenter TO, Whyte MP, Imel EA, et al. Burosumab Therapy in Children with X-Linked Hypophosphatemia. New England Journal of Medicine. 2018;378(21):1987-1998. doi:10.1056/NEJMoa1714641
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