Head to head

IGF-1 LR3 against Mecasermin

An approved IGF-1 medicine and a grey-market analogue of the same hormone. Mecasermin is approved only for growth failure in children with severe primary IGF-1 deficiency, where 49 percent of patients had hypoglycaemia; IGF-1 LR3 has animal work and no approval, and the hypoglycaemia risk does not disappear because the label does.

Column A

IGF-1 LR3

Long R3 Insulin-like Growth Factor 1

A long-acting analogue of IGF-1 studied in animal models for muscle growth and tissue repair.

Column B

Mecasermin

Mecasermin (Increlex), recombinant human IGF-1

An approved medicine, and only for a rare paediatric deficiency. In 76 children with severe IGF-1 deficiency, height velocity rose from 2.8 cm per year at baseline to 8.0 cm per year in the first year, and 49 percent had hypoglycaemia. Among registry patients followed to the end of puberty, mean height moved from about 3.7 to about 2.6 standard deviations below the mean in boys: better, still short.

Side by side, on the facts we can check

Attribute	IGF-1 LR3	Mecasermin
Category	Growth Hormone	Growth Hormone
FDA status	Not FDA-approved	FDA-approved. INCRELEX (mecasermin), BLA 021839, sponsor Ipsen, original approval 30 August 2005, prescription only. Indicated for growth failure in children with severe primary IGF-1 deficiency and in children with growth hormone gene deletion who have developed neutralising antibodies to growth hormone. It is not approved for adults, for sarcopenia, for recovery or for any performance use.
Half-life	~20-30 hours	Short, and shorter in the patients it treats. The circulating hormone is normally bound almost entirely to its binding protein and the acid-labile subunit, which extends its persistence enormously; in severe primary deficiency those binding proteins are low, so the administered hormone is cleared faster. This is why the approved product is injected twice daily with food rather than once a day.
Molecular weight	9,111 Da	7,649 Da. A single chain of 70 amino acids with three intramolecular disulfide bridges, per the INCRELEX product label.
Mechanism	Activates the IGF-1 receptor, driving cellular growth, proliferation, and protein synthesis; reduced binding-protein affinity prolongs activity.	Mecasermin binds the IGF-1 receptor, a receptor tyrosine kinase, activating PI3K/Akt and MAPK signalling to drive cell growth, protein synthesis and, at the growth plate, linear bone growth. It also has meaningful affinity for the insulin receptor, which is the direct reason hypoglycaemia is the principal adverse effect and why the product is dosed with a meal. Endogenous IGF-1 circulates almost entirely bound to IGFBP-3 and the acid-labile subunit, a complex whose formation depends on growth hormone signalling. In severe primary IGF-1 deficiency that signalling is broken, so the binding proteins are low, free IGF-1 exposure after a dose is higher and clearance faster than the endogenous hormone would suggest. That is the pharmacological difference between replacing IGF-1 and having made it yourself.
Human studies cited	0	5
Legal status, US	Not approved; research use only	FDA-approved, prescription only

open the IGF-1 LR3 profile open the Mecasermin profile

Frequently asked questions

What is the difference between IGF-1 LR3 and Mecasermin?

IGF-1 LR3: A long-acting analogue of IGF-1 studied in animal models for muscle growth and tissue repair. Mecasermin: An approved medicine, and only for a rare paediatric deficiency. In 76 children with severe IGF-1 deficiency, height velocity rose from 2.8 cm per year at baseline to 8.0 cm per year in the first year, and 49 percent had hypoglycaemia. Among registry patients followed to the end of puberty, mean height moved from about 3.7 to about 2.6 standard deviations below the mean in boys: better, still short.

Which has stronger research evidence, IGF-1 LR3 or Mecasermin?

This database does not grade compounds. It counts what was run in people: 0 of the 3 studies cited on the IGF-1 LR3 profile were human work, against 5 of 5 for Mecasermin. Those counts are of our own citation lists and understate any larger literature, and neither is a recommendation.

Are IGF-1 LR3 and Mecasermin FDA-approved?

IGF-1 LR3: Not FDA-approved. Mecasermin: FDA-approved. INCRELEX (mecasermin), BLA 021839, sponsor Ipsen, original approval 30 August 2005, prescription only. Indicated for growth failure in children with severe primary IGF-1 deficiency and in children with growth hormone gene deletion who have developed neutralising antibodies to growth hormone. It is not approved for adults, for sarcopenia, for recovery or for any performance use..

Reviewed Sep 2026. This page sets two published records side by side. It is educational, it is not medical advice, and it contains no dosing protocols or recommendations for personal use.