Mecasermin

Mecasermin (Increlex) is a real, FDA-approved recombinant IGF-1 analog for a rare pediatric growth-failure condition — approved on evidence that, honestly, lacked a randomized control group, and carrying a genuine hypoglycemia risk given IGF-1's insulin-like effects.

Bypassing the GH axis entirely

Mecasermin is recombinant human insulin-like growth factor 1 (IGF-1), produced in E. coli. Where drugs like sermorelin or tesamorelin stimulate the body's own GH release, and pegvisomant blocks the GH receptor, mecasermin skips the GH axis altogether — it directly supplies the downstream hormone (IGF-1) that GH signaling is ultimately supposed to produce, for children whose bodies can't make or use enough of their own, whether from primary IGF-1 deficiency or from neutralizing antibodies against GH itself.

The approval, and an honest evidence gap

The FDA approved mecasermin (as Increlex) on 30 August 2005 for growth failure in children 2 and older with severe primary IGF-1 deficiency, or with GH gene deletion and neutralizing antibodies to GH — both genuinely rare conditions. The core supporting evidence (Chernausek et al., J Clin Endocrinol Metab 2007, PMID 17192294; 76 children followed up to 12 years) is real and long-running, but a fair thing to say plainly: per a CADTH pharmacoeconomic review of the registration dataset, it lacked a randomized control group, meaning a causal treatment effect versus the natural course of the disease couldn't be as rigorously established as a placebo-controlled trial would allow. This is a genuine, citable evidentiary limitation for a rare-disease approval, not an editorial dig — regulators reasonably approved it anyway given how few options exist for these children.

The hypoglycemia risk

Increlex carries a boxed warning for hypoglycemia, including reported hypoglycemic seizures — an expected risk given IGF-1's structural and receptor overlap with insulin. The label recommends dosing with food and monitoring blood glucose closely, especially when starting treatment or adjusting the dose.

A discontinued sibling product

A related product, mecasermin rinfabate (Iplex, an IGF-1/IGFBP-3 complex), was approved in December 2005 but pulled from the US market in 2007 — not for a safety reason, but as part of a patent-infringement lawsuit settlement between the two companies involved, with the maker agreeing to stop US sales as part of the deal. Worth knowing if you encounter references to Iplex — it's a real, related, but now-unavailable product with a business-dispute origin story, not a safety withdrawal.