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IGF-1 LR3 1 mg — Peptides Only, research use only
Peptides · GH Axis

IGF-1 LR3

Third-party tested · COA with every order
CAS946870-92-4FormulaC400H625N111O115S9MW9117.60

Long-acting IGF-1 analogue with reduced binding-protein affinity.

  • Independently tested
  • Lot-matched COA
  • Lyophilized for stability
  • Ships from the USA
Research use only. Not for human or veterinary use. Sold to qualified researchers aged 21+.
$175.002 for $175 — $87.50 per vial
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IGF-1 LR3$175.002 for $175
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About IGF-1 LR3

Long-acting IGF-1 analogue with reduced binding-protein affinity.

Supplied as

1 mg per vial, as a lyophilized powder in a sealed glass vial with a crimped cap. The lot number on the label matches the certificate of analysis in the COA library.

Storage and handling

Store lyophilized powder frozen (−20 °C) or refrigerated, sealed and away from light. Once reconstituted, keep refrigerated (2–8 °C).

Handle in a laboratory setting using appropriate protective equipment. Consult the certificate of analysis and safety data for lot-specific information.

Important research notice. This product is intended solely for in-vitro and laboratory research. It is not a drug, food, supplement or cosmetic, has not been evaluated by the FDA, and must not be used in humans or animals. Peptides Only does not provide usage or dosing information.

Research summary

IGF-1 LR3 (Long R3 IGF-I) is an 83-amino-acid analog of human insulin-like growth factor-I with arginine in place of glutamate at position 3 and a 13-residue N-terminal extension. Both changes sharply reduce binding to IGF-binding proteins, which makes it more potent than native IGF-I in many systems and explains its long-standing use as a growth-factor supplement in serum-free cell culture and bioprocessing.

Also known as
Long R3 IGF-I · LongR3 IGF-1 · LR3-IGF-1 · Long-[Arg3]-IGF-I · LR3IGF-I
Sequence
Met-Phe-Pro-Ala-Met-Pro-Leu-Ser-Ser-Leu-Phe-Val-Asn-Gly-Pro-Arg-Thr-Leu-Cys-Gly-Ala-Glu-Leu-Val-Asp-Ala-Leu-Gln-Phe-Val-Cys-Gly-Asp-Arg-Gly-Phe-Tyr-Phe-Asn-Lys-Pro-Thr-Gly-Tyr-Gly-Ser-Ser-Ser-Arg-Arg-Ala-Pro-Gln-Thr-Gly-Ile-Val-Asp-Glu-Cys-Cys-Phe-Arg-Ser-Cys-Asp-Leu-Arg-Arg-Leu-Glu-Met-Tyr-Cys-Ala-Pro-Leu-Lys-Pro-Ala-Lys-Ser-Ala

What is IGF-1 LR3?

IGF-1 LR3 came out of work in Adelaide in the early 1990s by Francis, Ballard and colleagues on recombinant IGF-I fusion analogs. It joins the first 11 amino acids of methionyl porcine growth hormone and a Val-Asn linker (13 residues) to the 70-residue human IGF-I sequence carrying an Arg3 substitution, giving 83 residues in all1.

The design rests on one observation: IGF-I analogs that bind poorly to IGF-binding proteins (IGFBPs) are more potent than IGF-I wherever those proteins are present. [Arg3]-IGF-I bound very poorly to IGFBP-2 and only slightly less well than IGF-I to the type-1 IGF receptor, so reduced IGFBP binding, rather than stronger receptor binding, explained its higher potency in rat L6 myoblasts2. Adding the N-terminal extension produced Long [Arg3]-IGF-I, which matched des(1-3)IGF-I as the most potent analog in cell lines that secrete IGFBPs; in chicken embryo fibroblasts, which secrete none detectably, it was less potent than IGF-I1.

IGF-1 LR3 in cell culture and bioprocessing

Most published use of IGF-1 LR3 is in vitro. In serum-free Chinese hamster ovary (CHO) cell lines producing recombinant proteins, LongR3 sustained viability under production conditions better than insulin, the growth factor most often used in that setting3. A transcriptome study of CHO cells cultured with or without LongR3 linked it to enhanced growth and delayed cell death4, and in in vitro maturation of bovine oocytes it performed comparably to native IGF-I and fetal bovine serum5.

The property that matters in culture is the one seen in the original experiments: the analog's advantage over IGF-I appears in cells that secrete IGFBPs into the medium and disappears in cells that do not1.

What animal studies have examined

  • Dexamethasone-treated rats: LR3IGF-I was about 2.5-fold more potent than IGF-I in partially reversing glucocorticoid-induced catabolism, despite binding the type-1 IGF receptor three-fold less well6.
  • Growing female rats: LR3IGF-I was substantially more potent than IGF-I for body-weight gain and nitrogen retention over 14 days7.
  • Pigs and marmosets: IGF-I variants with low IGFBP affinity, including LR3IGF-I, lowered plasma glucose more potently and for longer than native IGF-I8.
  • Gut and muscle: radiolabeled LR3IGF-I reached rat gastrointestinal tissue in higher amounts than IGF-I9, and in dystrophic mdx mice four weeks of an LR IGF-I analog reduced contraction-induced muscle damage10.

Regulatory status

IGF-1 LR3 has never been approved as a medicine for human use. IGF-I and its analogs are prohibited in sport, and anti-doping laboratories have developed mass-spectrometry methods to detect LongR3-IGF-I and its breakdown products, reporting oxidized, lower-quality forms in black-market material11. Peptides Only supplies it only as a research reagent.

Limitations of the evidence

The core pharmacology comes largely from the group that developed the analog, and most in vivo data are from rats, pigs and mice in studies published in the 1990s and 2000s6,7,8. There are no controlled human studies. Because potency tracks how much IGFBP a system contains1, results from one cell type or species do not transfer automatically to another.

Quality also matters: oxidized forms have been found in black-market products11. Every Peptides Only lot ships with an independent, lot-matched certificate of analysis covering HPLC purity and mass-spec identity, and our guide on how to read a peptide COA explains what to check.

IGF-1 LR3 FAQ

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

Native IGF-I has 70 residues. IGF-1 LR3 adds a 13-residue N-terminal extension and swaps Glu3 for Arg, giving 83 residues. The changes cut binding to IGF-binding proteins, so the analog is more potent than IGF-I in systems that contain those proteins1,2.

Why is IGF-1 LR3 used in cell culture?

It is used in serum-free media as an alternative to insulin; in one CHO-cell study it sustained viability under production conditions better than insulin3. Reduced IGFBP binding is the usual explanation for its potency in cultures that secrete binding proteins1.

Is IGF-1 LR3 approved for human use?

No. It has never been approved as a medicine, and IGF-I analogs are prohibited in sport11. Peptides Only supplies it for laboratory research only.

Is IGF-1 LR3 the same as Long R3 IGF-I or LongR3?

Yes. LR3, Long R3, LongR3 and Long [Arg3]-IGF-I all refer to the analog described by Francis and colleagues in 19921.

How is lyophilized IGF-1 LR3 stored?

Lyophilized peptides are generally kept cold, dry and away from light. General guidance is in peptide storage and stability; Peptides Only does not give usage instructions.

References

  1. Francis GL, Ross M, et al. Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol. 1992;8(3):213-23. PubMed 1378742
  2. King R, Wells JR, et al. Production and characterization of recombinant insulin-like growth factor-I (IGF-I) and potent analogues of IGF-I, with Gly or Arg substituted for Glu3, following their expression in Escherichia coli as fusion proteins. J Mol Endocrinol. 1992;8(1):29-41. PubMed 1311930
  3. Morris AE, Schmid J. Effects of insulin and LongR(3) on serum-free Chinese hamster ovary cell cultures expressing two recombinant proteins. Biotechnol Prog. 2000;16(5):693-7. PubMed 11027158
  4. Becker J, Timmermann C, et al. Transcriptome analyses of CHO cells with the next-generation microarray CHO41K: development and validation by analysing the influence of the growth stimulating substance IGF-1 substitute LongR(3.). J Biotechnol. 2014;178:23-31. PubMed 24613301
  5. Araujo MS, Guastali MD, et al. Molecular and cellular effects of insulin-like growth factor-1 and LongR3-IGF-1 on in vitro maturation of bovine oocytes: comparative study. Growth Horm IGF Res. 2020;55:101357. PubMed 33038561
  6. Tomas FM, Knowles SE, et al. Insulin-like growth factor-I (IGF-I) and especially IGF-I variants are anabolic in dexamethasone-treated rats. Biochem J. 1992;282(Pt 1):91-7. PubMed 1371669
  7. Tomas FM, Knowles SE, et al. Anabolic effects of insulin-like growth factor-I (IGF-I) and an IGF-I variant in normal female rats. J Endocrinol. 1993;137(3):413-21. PubMed 8371075
  8. Tomas FM, Walton PE, et al. IGF-I variants which bind poorly to IGF-binding proteins show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys. J Endocrinol. 1997;155(2):377-86. PubMed 9415072
  9. Shoubridge CA, Read LC. Preferential intestinal delivery of long[Arg3] insulin-like growth factor (LR3IGF-I) over IGF-I in preweaning and adult rats. Endocrinology. 2003;144(5):1887-93. PubMed 12697696
  10. Gehrig SM, Ryall JG, et al. Insulin-like growth factor-I analogue protects muscles of dystrophic mdx mice from contraction-mediated damage. Exp Physiol. 2008;93(11):1190-8. PubMed 18567600
  11. Mongongu C, Coudoré F, et al. Detection of LongR(3) -IGF-I, Des(1-3)-IGF-I, and R(3) -IGF-I using immunopurification and high resolution mass spectrometry for antidoping purposes. Drug Test Anal. 2021;13(7):1256-1269. PubMed 33587816

Research summary reviewed 2026-10-26 against the cited literature.

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