Mecasermin (Increlex): effects, uses and side effects
Clinical review pending
Mecasermin replaces IGF-1 in children with certain rare growth disorders. How it works, its US-approved uses and its risks.
Mecasermin may be used in children with certain rare growth disorders, particularly severe primary IGF-1 deficiency. It directly replaces the missing growth factor IGF-1. Ordinary growth hormone deficiency, by contrast, is treated with growth hormone. Mecasermin can lower blood glucose excessively and cause hypoglycemia. Its administration therefore needs to be timed around a meal.
What is mecasermin?
Mecasermin is a laboratory-made copy of insulin-like growth factor 1, or IGF-1. It is available under the brand name Increlex. IGF-1 mediates much of growth hormone’s effect: growth hormone stimulates the liver to produce IGF-1, which in turn promotes tissue growth.
When children cannot produce IGF-1, or their bodies do not respond to growth hormone, growth is impaired. Mecasermin supplies IGF-1 directly. The medicine was approved in the United States in 2005.
How does mecasermin work?
Mecasermin is identical to natural IGF-1. It binds to IGF-1 receptors—binding sites on cells throughout the body—and triggers a growth-promoting signal. Normally, this signal follows growth hormone stimulation of IGF-1 production. Children with severe primary IGF-1 deficiency have growth hormone, but their bodies do not produce IGF-1 in response. Mecasermin replaces the missing IGF-1, allowing growth that cannot be achieved with growth hormone alone.
In a study of children who did not respond to growth hormone, average growth velocity increased with IGF-1: it was about 2.8 cm per year before treatment and 8.0 cm per year during the first treatment year. These figures compare growth with the pretreatment period. 1
IGF-1 has some insulin-like effects. Mecasermin can therefore also lower blood glucose and is given shortly before or after a meal.
Is mecasermin FDA-approved?
Yes. The US Food and Drug Administration approved mecasermin in 2005 for growth failure in children with severe primary IGF-1 deficiency. Approval also covers children with a growth hormone gene deletion who have developed neutralizing antibodies to growth hormone. A deletion means that genetic material is missing. Neutralizing antibodies block growth hormone’s effects.
Mecasermin is injected under the skin twice daily. This information refers to the US approval. 2
What is mecasermin prescribed for?
Mecasermin is prescribed for children with severe primary IGF-1 deficiency. In this rare condition, the body does not produce IGF-1 despite normal or elevated growth hormone levels. In ordinary growth hormone deficiency, by contrast, growth hormone itself is missing. That deficiency is treated with growth hormone; mecasermin is not intended for it.
What side effects can occur?
The US prescribing information [2] lists common side effects including:
- Hypoglycemia. Administration must therefore be timed around a meal.
- Injection-site changes, such as lump-like thickening of fatty tissue.
- Enlargement of the tonsils or adenoids.
More serious risks include:
- Increased pressure inside the skull, medically called intracranial hypertension.
- Slipping of the femoral head at the growth plate and worsening of scoliosis, a sideways curvature of the spine.
- Cancers reported in children receiving mecasermin. Such reports alone do not establish that mecasermin caused the cancers.
Mecasermin must not be used when the growth plates have already closed. Children who have cancer or have previously had cancer must not receive it either.