IGF-1 LR3

What is IGF-1 LR3 and how does it differ from approved IGF-1?

IGF-1 LR3 is a modified, longer-acting version of insulin-like growth factor 1, sold online as a research peptide. The only FDA-approved IGF-1 product is Increlex (mecasermin), a recombinant human IGF-1 approved in 2005 for growth failure in children with severe primary IGF-1 deficiency or growth-hormone gene deletion with neutralizing antibodies [1]. Increlex's label carries warnings for severe hypoglycemia that can lead to seizures, intracranial hypertension, and tonsillar or adenoidal hypertrophy, and notes postmarketing reports of malignant neoplasms in children who received it [1]. IGF-1 LR3 is not that approved product and is not FDA-approved itself.

Is IGF-1 LR3 tested in humans or regulated by FDA?

A 2010 case report found that a black-market injection vial sold as an IGF-1 product actually contained a His-tagged form of "Long-R³-IGF-I," a variant the authors say is "usually produced for biochemical studies"; they concluded its effects "in humans have not been elucidated" and that the product "may rather be a by-product from biochemical studies than synthesized for injection purposes" [2]. IGF-1 LR3 does not appear on FDA's May 2026 list of substances nominated for compounding [3]. Insulin-like growth factor 1 and its analogues are prohibited at all times under the 2026 WADA list [4].