Compare prices and buy IGF-1 LR3 from 31 research peptide vendors - also called suppliers or sources. Updated daily.
An 83-residue recombinant analog of insulin-like growth factor-1 (CAS 143045-27-6) combining a Glu3->Arg substitution with a 13-residue N-terminal extension (MFPAMPLSSLFVN) on native IGF-1's 70-residue sequence. Both changes cut its affinity for the IGF binding proteins while leaving receptor binding slightly weaker than native IGF-1's. Because it stays largely free in plasma, it is cleared from blood faster than native IGF-1 in rats. Sold as a cell-culture reagent, where it substitutes for insulin in serum-free media. No published human studies or FDA approval, and distinct from mecasermin (Increlex) and mecasermin rinfabate (Iplex).
For research purposes only. Not medical advice.
IGF-1 LR3, also written Long [Arg3] IGF-I or LR3IGF-I, is a recombinant analog of human insulin-like growth factor 1. FDA's substance registry lists it as an 83-residue protein with three disulfide links, under UNII M9L22Y19H9. Mature native IGF-1 is 70 residues.
Two changes separate them. Glutamate at position 3 of the IGF-1 chain is replaced by arginine, and a 13-residue extension sits on the N-terminus. Francis and colleagues, describing the molecule in the Journal of Molecular Endocrinology in 1992, built that extension from the first 11 amino acids of methionyl porcine growth hormone followed by valine and asparagine. It was built at the CSIRO Division of Human Nutrition and the University of Adelaide, and published methods name Gropep of Adelaide as the original commercial source.
Its documented use is cell culture, where Voorhamme and Yandell reported it supporting Chinese hamster ovary cells in serum-free media at concentrations at least 200-fold lower than insulin requires (Molecular Biotechnology, 2006). Repligen sells it as LONG R3 IGF-1.
Both modifications loosen the molecule's grip on the IGF binding proteins instead of tightening its grip on the receptor. King and colleagues (Journal of Molecular Endocrinology, 1992) found [Gly3] and [Arg3] IGF-I bound IGFBP-2 very poorly while binding the type 1 receptor on rat L6 myoblasts slightly less well than IGF-1, and named the weaker binding-protein association as the likely source of the greater potency. Ballard and colleagues (Growth Regulation, 1993) put the affinity gap at roughly 1000-fold against IGFBP-3, IGFBP-4 and total rat plasma binding proteins. The negative control is the clearest evidence: in chicken embryo fibroblasts, which secrete no detectable binding proteins, Long [Arg3] IGF-I was less potent than native IGF-1 (Francis, 1992).
Clearance follows from the same property. Native IGF-1 circulates mostly in a large ternary complex with IGFBP-3, and Guler and colleagues measured its apparent half-life in that complex at 12 to 15 hours in two healthy adults (Acta Endocrinologica, 1989). The analog stays largely free, so it leaves the circulation faster. Bastian and colleagues measured metabolic clearance in rats at 0.90 ml per minute per kg for IGF-1 against 9.19 for LR3IGF-I (Journal of Endocrinology, 1993).
The animal record is 1990s rodent and livestock work.
The binding proteins themselves differ by species. Lord and colleagues found the variants bound measurably in sheep, human, pig and chicken plasma while binding extremely weakly in rat plasma (Journal of Endocrinology, 1994), so the rat is where escape from the binding proteins counts for most.
Human data is absent. A 2026 narrative review in Frontiers in Endocrinology places IGF-1 LR3 in its lowest evidence tier, no peer-reviewed human studies, alongside PEG-MGF, and records its half-life as undocumented. ClinicalTrials.gov returns no registered study of the compound as of October 2026.
No FDA-approved drug contains the analog, and a drugsfda search returns no matching application. Mecasermin, recombinant human IGF-1 with the endogenous sequence, has been approved since August 2005 as Increlex, and its label contraindicates use in malignant neoplasia and warns of severe hypoglycemia leading to seizures. Mecasermin rinfabate, recombinant IGF-1 complexed with IGFBP-3, was approved as Iplex in December 2005, and under a March 2007 settlement with Tercica and Genentech, Insmed stopped supplying it for short-stature indications. Drugsfda lists it as discontinued as of October 2026.
The analog appears in neither table of FDA's Category 2 page of bulk drug substances that may present significant safety risks in compounding (content current as of April 22, 2026), and not on the 503A bulks list. The World Anti-Doping Agency covers it as a class member: section S2.3 prohibits insulin-like growth factor 1 and its analogs at all times, naming mecasermin as its example, in both the list in force and the 2027 list.
No published human study of it exists. A 2026 narrative review of growth hormone and IGF-1 axis compounds in Frontiers in Endocrinology assigns IGF-1 LR3 to its lowest evidence tier, defined as no peer-reviewed human studies, and records its half-life in humans as undocumented. ClinicalTrials.gov returns no registered study of the compound under any of its names as of October 2026. The published record is cell culture and animal work from the 1990s in rats, pigs, sheep, guinea pigs, calves, marmosets and chickens, so any statement about effects in people is an extrapolation from those models.
No. Increlex is mecasermin, recombinant human IGF-1 whose amino acid sequence is identical to the endogenous hormone, 70 residues and 7649 daltons according to its FDA label. It was approved in August 2005 for growth failure in children two years and older with severe primary IGF-1 deficiency or a growth hormone gene deletion who have developed neutralizing antibodies to growth hormone. IGF-1 LR3 is a different molecule, 83 residues, carrying an arginine substitution at position 3 and a 13-residue N-terminal extension. It holds no FDA approval and no approved drug contains it.
The primary pharmacokinetic work points the other way. Native IGF-1 circulates mostly bound in a large complex with IGFBP-3 and an acid-labile subunit, and that complex is what gives the 12 to 15 hour figure measured by Guler and colleagues in 1989. Free IGF-1 tracer in the same study had an apparent half-life of 10 to 12 minutes. Because IGF-1 LR3 binds the IGF binding proteins about 1000-fold more weakly, it stays largely free and is cleared faster. Bastian and colleagues measured metabolic clearance in rats at roughly ten times the rate of native IGF-1.
Voorhamme and Yandell describe it as engineered for that use. Writing in Molecular Biotechnology in 2006, they reported that it supports growth and survival of Chinese hamster ovary cells in serum-free media at concentrations at least 200-fold lower than insulin requires, and that it outperformed both insulin and native IGF-1 in serum-free culture of human embryonic kidney cells. Repligen's product page lists LONG R3 IGF-1 as a cell-culture supplement used to support the growth of recombinant cell lines, suited to serum-free or low-serum media. Published methods sections from the 1990s name Gropep of Adelaide, where the molecule originated, as the supplier.
Yes, by class. The World Anti-Doping Agency's Prohibited List does not name IGF-1 LR3, but section S2.3 covers insulin-like growth factor 1 and its analogs among growth factors, giving mecasermin as the named example, and the same entry appears in the list currently in force and in the 2027 list published in September 2026. Everything in section S2 is prohibited at all times, in and out of competition. The section also sweeps in mechano growth factors and other growth factor modulators affecting muscle, tendon or ligament protein synthesis.
IGF-1 LR3 is sold by 31 research peptide vendors indexed on PeptideScouter, with 44 tracked listings compared per vendor in the table above. Pricing is normalized and refreshed daily.
26 of the 31 indexed vendors currently have IGF-1 LR3 in stock. The comparison table marks out-of-stock listings, and stock state is refreshed daily.
Glow Aminos currently lists IGF-1 LR3 at $35.40/mg, the lowest listed price across 31 tracked research peptide vendors. With current vendor discount codes applied, the lowest effective price is $30.09/mg.
Discount codes are issued per vendor rather than per peptide, so any code applies across that vendor's whole catalog. All 31 vendors listing IGF-1 LR3 publish a PeptideScouter code, worth 5% to 25% off. Applied, the lowest effective price falls from $35.40/mg listed to $30.09/mg at Glow Aminos. Each vendor's code is shown beside its price in the table above.
IGF-1 LR3 ranges from $35.40/mg to $299.90/mg across 44 listings from 31 research peptide vendors, normalized to USD per milligram and refreshed daily.
31 research peptide vendors currently list IGF-1 LR3 on PeptideScouter, with 26 in stock right now. We track 44 listings across size and kit variants.
IGF-1 LR3's CAS Registry Number is 143045-27-6. It is also sold as IGF-LR3, IGF1-LR3, IGF-1LR3.
