Mecasermin: What It Is and How Recombinant IGF-1 Works

At a glance

What is mecasermin?

Mecasermin, sold under the brand Increlex, is a laboratory-made copy of insulin-like growth factor 1 (IGF-1), the hormone that actually carries out much of growth hormone's work in the body. Growth hormone stimulates the liver to make IGF-1, and IGF-1 then drives tissue growth. Children who cannot make IGF-1, or who cannot respond to growth hormone, do not grow normally; mecasermin provides the IGF-1 directly. It was approved in the United States in 2005.

How does mecasermin work?

Mecasermin is identical to natural IGF-1 and binds the IGF-1 receptor on cells throughout the body, directly delivering the growth-promoting signal that would normally follow growth hormone action. In children with severe primary IGF-1 deficiency, growth hormone is present but the body cannot generate IGF-1 in response, so replacing IGF-1 restores growth that growth hormone therapy alone cannot achieve. Because IGF-1 shares actions with insulin, mecasermin can lower blood sugar, which is why it is dosed shortly before or after a meal. In the pivotal study of children with growth hormone insensitivity, IGF-1 raised average height velocity from about 2.8 cm per year at baseline to 8.0 cm per year in the first year of treatment.

Is it FDA-approved?

Yes. Mecasermin was approved by the FDA in 2005 for growth failure in children with severe primary IGF-1 deficiency, or with growth hormone gene deletion who have developed neutralizing antibodies to growth hormone. It is given as a twice-daily subcutaneous injection.

What is mecasermin prescribed for?

Mecasermin is prescribed for children with severe primary IGF-1 deficiency, a rare condition in which the body cannot produce IGF-1 despite normal or high growth hormone. It is not a treatment for ordinary growth hormone deficiency, which is treated with growth hormone itself.

What are the side effects?

According to the prescribing information, common side effects include:

• Low blood sugar, which is why dosing is tied to meals
• Injection-site changes such as fatty lumps
• Enlargement of the tonsils or adenoids More serious considerations include:
• Increased pressure around the brain (intracranial hypertension)
• Slipped hip growth plate and worsening scoliosis
• Cancers, which have been reported in children treated with mecasermin Mecasermin is contraindicated once the growth plates have closed and in children with cancer or a history of cancer.

Evidence strength

FDA approved: Mecasermin is FDA-approved for severe primary IGF-1 deficiency, supported by clinical studies showing increased growth velocity in affected children.

Sources: FDA prescribing information for Increlex; a long-term study of IGF-1 therapy (Chernausek et al., Journal of Clinical Endocrinology and Metabolism, 2007, DOI: 10.1210/jc.2006-1610), indexed on PubMed. This document is educational and does not constitute medical advice.