Mecasermin

Increlex

Mecasermin is recombinant human insulin-like growth factor-1 (rhIGF-1), a laboratory-produced copy of the natural IGF-1 hormone. IGF-1 is the principal mediator of growth: much of what growth hormone (GH) does to promote childhood growth, it does indirectly, by stimulating the liver and other tissues to produce IGF-1, which then drives the growth of bone, muscle, and other tissues. Mecasermin supplies IGF-1 directly, bypassing the GH step entirely. This direct replacement is exactly what is needed in severe primary IGF-1 deficiency (SPIGFD), a rare condition in which children make plenty of growth hormone but cannot produce IGF-1 in response — for example because of defects in the GH receptor (as in Laron syndrome) or in the downstream signaling. In these children, giving more growth hormone does not work, because the problem is downstream of GH. Mecasermin replaces the missing IGF-1 and can meaningfully improve growth. It was approved by the FDA in 2005 (Increlex) for long-term treatment of growth failure in children with severe primary IGF-1 deficiency, and for IGF-1 gene deletion with neutralizing antibodies to GH. Because IGF-1 is structurally related to insulin and shares some of its actions, the most important and predictable side effect of mecasermin is hypoglycemia (low blood sugar). For this reason it must be given with a meal or snack shortly before or after each dose, and children are monitored, especially at the start of treatment. Other considerations include enlargement of the tonsils and lymphoid tissue, and the need for careful patient selection. It is given by subcutaneous injection twice daily under the care of a pediatric endocrinologist, and it is a prescription hormone-replacement medicine — distinct from growth hormone itself and from research 'IGF-1' products, which are unapproved and unsafe to self-source.