Who is Eligible for Voxzogo (Vosoritide) Treatment?

Voxzogo (vosoritide) is a daily injection approved for children with achondroplasia whose growth plates (the physes) are still open ^[1][2][3]. If your child has a confirmed diagnosis of achondroplasia and is still growing, they are likely eligible to be evaluated for this treatment. Eligibility is primarily determined by whether the bones still have the capacity to lengthen, rather than by a strict age limit ^[2].

Age Approvals for Voxzogo

When Voxzogo was first approved by the FDA in 2021, it was restricted to children aged 5 years and older ^[1][3]. However, based on successful clinical trials showing it is safe and effective in younger children, the FDA and the European Medicines Agency (EMA) have expanded their approvals ^[4][5].

Today, Voxzogo is approved for use in infants and toddlers. In the United States, there is no longer a lower age limit; children of all ages (from birth) with open growth plates are eligible ^[4]. Studies show that starting treatment earlier offers advantages for long-term growth and might theoretically help reduce future complications like spinal stenosis, though long-term data proving this prevention is still maturing ^[6][7].

The Key Requirement: Open Growth Plates

The most important factor in determining eligibility is whether your child’s growth plates (the areas of active growth at the ends of long bones) are “open.” Voxzogo works by stimulating these specific areas to create new bone ^[2][3]. Doctors confirm this by looking for open epiphyses (the rounded ends of the bones next to the growth plate) on an X-ray ^[1].

Once a child goes through puberty and reaches their final adult height (typically between ages 14 and 17), these growth plates fuse or “close.” Once the growth plates are closed, Voxzogo can no longer increase bone length, and the treatment must be stopped ^[1][2].

Who Determines Eligibility?

Eligibility is usually determined and managed by specialists who have deep experience with bone growth and genetic conditions:

• Pediatric Endocrinologists: Doctors who specialize in hormones and physical growth.
• Clinical Geneticists: Doctors who specialize in genetic conditions like achondroplasia.

These specialists work as a team to ensure safe clinical rollout and ongoing monitoring ^[8][9][10]. They will also coordinate training on how to safely and comfortably give the medication, which is a subcutaneous injection (a small shot given into the fatty layer just under the skin) administered by parents or caregivers at home ^[1][11].

Baseline Tests Needed Before Starting

If you decide to explore Voxzogo, your child will need several baseline assessments:

• Bone X-rays: To definitively confirm that the growth plates are still open ^[1][2].
• Baseline Growth Measurements: The doctor will measure your child’s height, sitting height, and head circumference to calculate their growth velocity (how fast they are currently growing) ^[12][5].
• Blood Pressure and Cardiovascular Evaluation: Voxzogo works by relaxing blood vessels, which can cause transient hypotension (temporary low blood pressure) ^[1][13]. Doctors will evaluate your child’s baseline cardiovascular health, which is especially critical for infants ^[13][8].

A Note on Daily Routine and Side Effects

Because of the risk of temporary low blood pressure after the injection, patients aged 2 years and older must eat a meal and drink 8 to 10 ounces (240–300 mL) of fluid within the hour before their daily dose ^[1][14].

Important for infants: Do not attempt to force an infant to drink 8 to 10 ounces of fluid in a single hour. For infants and toddlers under 2 years old, the medical team will help you time the injection around their normal, adequate feeding schedule to safely prevent blood pressure drops ^[13].

Finally, because this is a daily injection, minor injection site reactions (such as redness, slight swelling, or pain at the spot of the shot) are common ^[3]. Your medical team will monitor these and teach you techniques to minimize discomfort.