Mecasermin

Mecasermin is a laboratory-produced copy of IGF-1, a major mediator of growth-hormone action. Normally GH stimulates liver IGF-1 production; direct IGF-1 replacement bypasses that step when a child cannot make IGF-1 or respond adequately to GH. The brand Increlex received US approval in 2005.

The molecule is identical to natural IGF-1 and activates IGF-1 receptors throughout the body. Severe primary IGF-1 deficiency can occur despite normal or high GH, so extra GH alone may not restore growth. Direct replacement delivers the missing signal.

IGF-1 also has insulin-like actions and may lower glucose, which is why injections are timed shortly before or after food. In the pivotal GH-insensitivity study, mean height velocity increased from about 2.8 cm/year before treatment to 8.0 cm/year during the first treatment year.

FDA approved mecasermin in 2005 for growth failure with severe primary IGF-1 deficiency, or GH-gene deletion accompanied by neutralizing antibodies against GH. The product is administered subcutaneously twice daily.

Its principal population is children with severe primary IGF-1 deficiency. It is not a substitute for GH in ordinary growth-hormone deficiency, where replacement of GH itself is the appropriate category of treatment.

Hypoglycemia is a central risk and explains meal-linked administration. Other common effects include fatty injection-site lumps and enlargement of tonsils or adenoids. Serious concerns include intracranial hypertension, slipped hip growth plate, worsening scoliosis and reported cancers in treated children. Use is contraindicated after growth plates close and in children with cancer or a cancer history.