Recombinant IGF-1 · growth failure
A lab-made copy of human insulin-like growth factor 1 (IGF-1), produced with recombinant DNA. It is the active ingredient in Increlex, a prescription injection for children whose growth is held back because their bodies make too little IGF-1 even though growth hormone is present.
Normally, growth hormone from the pituitary signals the liver and other tissues to make IGF-1, and IGF-1 carries out much of the actual work of growth. It binds the type 1 IGF receptor, a close relative of the insulin receptor, on cartilage cells at the growth plates and on many other tissues, driving cell division and bone lengthening. Some children have normal or high growth hormone but very low IGF-1, often because their growth hormone receptor does not work (Laron syndrome), or because they have lost the growth hormone gene and formed antibodies to replacement hormone. Supplying IGF-1 directly bypasses the broken step. Because IGF-1 also acts like insulin, lowering liver glucose output and increasing glucose uptake, it can drop blood sugar.
Human data come mainly from children with severe primary IGF-1 deficiency. In a long-term, mostly open-label study of 76 children with growth hormone insensitivity, average height velocity rose from about 2.8 to 8.0 cm per year in the first year and stayed above baseline for up to eight years, though gains were smaller after year one2. The label's pooled analysis of five studies in 71 children found similar results: height standard deviation scores improved by about 1.4 by year three, while average height remained far below the population mean1. Hypoglycemia was the most common adverse event, reported by about half of treated children in the long-term study (it was also seen before treatment began), with injection-site fat thickening and tonsil or adenoid enlargement also common2.
FDA-approved in 2005 as Increlex, now marketed by Ipsen, for growth failure in children 2 years and older with severe primary IGF-1 deficiency, or with growth hormone gene deletion and neutralizing antibodies to growth hormone. The label states it is not a substitute for growth hormone where growth hormone is the approved treatment.
The label warns of hypoglycemia, including seizures, because IGF-1 acts like insulin. Other warnings: allergic reactions including anaphylaxis, raised pressure around the brain, tonsil and adenoid enlargement (snoring, sleep apnea, ear fluid), slipped capital femoral epiphysis, worsening scoliosis, and malignant tumors reported in treated children. It is contraindicated with active or past cancer and after growth plates close, and its benzyl alcohol preservative makes it unsuitable for infants.
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