Growth & GH-AxisListed — currently OOS

IGF-1 LR3

IGF-1 analog (Long R3 IGF-1 variant)

A long-acting analog of insulin-like growth factor-1 studied in IGF-axis research.

Also referenced as: Long R3 IGF-1, LR3-IGF-1

83 aat½ Substantially longer than native IGF-1; reported on the order of many hours (approximately 20-30 hours) due to reduced IGFBP binding

Overview

IGF-1 LR3 (Long R3 IGF-1) is a synthetic analog of insulin-like growth factor 1 with an arginine substituted for glutamate at position 3 and a 13-amino-acid N-terminal extension, giving an 83-residue peptide. It was originally developed for cell-culture applications.

At a glance

ClassIGF-1 analog (Long R3 IGF-1 variant)

CategoryGrowth & GH-Axis

Chain length83 amino acids

Molecular weightApproximately 9111 g/mol

Half-lifeSubstantially longer than native IGF-1; reported on the order of many hours (approximately 20-30 hours) due to reduced IGFBP binding

Typical formLyophilized powder

AliasesLong R3 IGF-1, LR3-IGF-1

Use designationResearch / in-vitro only

Regulatory statusIGF-1 LR3 is not approved by the FDA or EMA as a medicine; it is marketed as a cell-culture reagent and used in research contexts only.

What IGF-1 LR3 does

IGF-1 LR3 (Long R3 IGF-1) is an engineered analog of insulin-like growth factor 1 designed for potency and durability. It carries two modifications: an arginine substituted for glutamic acid at position 3 (the R3), and a 13-amino-acid N-terminal extension (the Long). Like IGF-1 DES it is a direct effector — it binds and activates the IGF-1 receptor itself, driving anabolic PI3K/Akt and MAPK signaling in muscle and other tissues — rather than acting through the pituitary GH axis. This makes it, mechanistically, a downstream anabolic agent independent of GH.

The two modifications serve distinct purposes. The R3 substitution sharply reduces binding to IGF binding proteins, so the analog escapes the IGFBP buffering that normally restrains free IGF-1; the N-terminal extension further stabilizes the molecule against clearance. The combined result is a dramatically longer functional half-life than native IGF-1 or DES(1-3)IGF-1 — on the order of many hours rather than minutes — producing sustained, systemic IGF-receptor activation. That durability and systemic reach are what distinguish LR3 from the short-acting, locally-acting DES variant.

IGF-1 LR3 is widely used as a laboratory reagent for cell culture (where its potency and stability are advantageous) and studied preclinically for anabolic effects on muscle. It is not an approved human therapeutic, and human efficacy or safety for performance/body composition is not established.

Effects reported in research

Directly activated the IGF-1 receptor to drive anabolic PI3K/Akt and MAPK signaling, independent of the GH/pituitary axis (in-vitro).
Bound IGF binding proteins with greatly reduced affinity (R3 substitution), leaving it free and active.
Resisted clearance via the N-terminal extension, giving a much longer half-life (hours vs. minutes for native IGF-1/DES).
Produced sustained, systemic IGF-receptor activation rather than a brief local effect.
Stimulated cell proliferation and protein synthesis — widely exploited as a cell-culture growth reagent.
Promoted muscle-cell anabolism and hypertrophy signaling in preclinical models.
Human efficacy/safety for muscle growth is unproven; research-use only.

Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.

Mechanism of action

IGF-1 LR3 is an agonist of the IGF-1 receptor, driving the same anabolic and proliferative signaling as native IGF-1. The Arg3 substitution and N-terminal extension sharply reduce its affinity for IGF-binding proteins (IGFBPs), leaving more peptide free and biologically active and greatly extending its functional half-life relative to native IGF-1.

Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.

What it's studied for

Research contexts in which IGF-1 LR3 appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.

Key characteristics

Arg-3 substitution plus 13-residue N-terminal extension (83 aa total)
Greatly reduced IGFBP binding extends half-life well beyond native IGF-1
Longer-acting than IGF-1 DES, which is truncated and short-acting
Widely used as a cell-culture growth supplement
Acts through the IGF-1 receptor, downstream of GH

Reported research dosing reference only

Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. IGF-1 LR3 is a research compound.

IGF-1 LR3 is referenced in the research literature in the low-microgram-per-day range, supported by its long half-life. These are reference figures for research context only, not dosing guidance for humans.

Common research-protocol reference: ~20-50 mcg per day

Reported frequencyReported approximately once daily in research protocols, reflecting the ~20-30 hour half-life

ReconstitutionLyophilized; typically reconstituted with bacteriostatic water or dilute acetic acid for research use

~3x more potent than native IGF-1 with very low IGFBP affinity; long half-life. Reference figures only, not human dosing guidance.

How it compares

IGF-1 LR3 is engineered for a long half-life via Arg3 substitution and an N-terminal extension that minimize IGFBP binding, contrasting with the short-acting, truncated IGF-1 DES.

Commonly studied alongside

Compounds frequently researched together with IGF-1 LR3 in the literature. Cross-referenced for research context — not a usage or combination recommendation.

IGF-1 DESLong-acting vs short-acting IGF-1 analogs are commonly compared/co-studied for IGF-1R activation.CJC-1295 (with DAC)GHRH-driven endogenous GH/IGF-1 elevation is studied alongside a direct long-acting IGF-1 receptor agonist.MK-677Oral GH secretagogue that raises IGF-1 is co-studied with a direct IGF-1R agonist for comparison.

Compare and calculate

Side-by-side pages for the pairings the literature already documents for IGF-1 LR3, plus the unit-conversion reference for a reconstituted vial. Factual comparisons of documented characteristics — not a recommendation to combine or use any compound.

IGF-1 LR3 reconstitution calculator → Concentration, volume per measured amount and syringe units for a stated vial mass and diluent volume. A unit-conversion reference, not a dosing recommendation.

Handling & Stability

Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.

Avoid repeated freeze-thaw cycles
Verify supplier lot and Certificate of Analysis
Follow institutional lab-safety protocols

Analytical & COA Concepts

Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:

Category Context

IGF-1 LR3 sits in the Growth & GH-Axis area of the PeptiDex library.

Research Supplier Listing

Where researchers source IGF-1 LR3

For researchers studying IGF-1 LR3, third-party suppliers such as Practically Natty Peptides offer research-grade material, third-party tests every batch and provides Certificates of Analysis on request, and ship from the US. This specific listing is currently marked out of stock — check the supplier site for current availability.

View research-supplier listing →

Outbound link to a third-party research supplier. Inclusion does not constitute endorsement; all editorial content is developed independently.

Frequently asked questions

What is IGF-1 LR3?

IGF-1 LR3 (Long R3 IGF-1) is an 83-amino-acid analog of insulin-like growth factor-1 with an arginine substituted at position 3 and a 13-amino-acid N-terminal extension. It is an IGF-1 receptor agonist engineered for very low IGF-binding-protein affinity and greatly extended stability.

How does IGF-1 LR3 differ from IGF-1 DES?

Both reduce IGFBP binding, but IGF-1 LR3's modifications give it a long half-life (~20-30 hours) versus IGF-1 DES's ~20-30 minutes. LR3 is studied for sustained systemic IGF-1 receptor activation, whereas DES is studied for short, localized action.

Why does IGF-1 LR3 have such an extended half-life?

The Arg3 substitution plus the N-terminal extension sharply lower its affinity for IGF-binding proteins while improving metabolic stability, so the peptide circulates far longer than native IGF-1. The research literature reports it is roughly three times more potent than native IGF-1.

What does the long half-life mean for research design?

Because IGF-1 LR3 persists ~20-30 hours, research protocols reference once-daily administration and sustained IGF-1 receptor tone, in contrast to the pulsatile or localized approaches used with short-acting IGF-1 variants.

Is IGF-1 LR3 an approved drug?

No. IGF-1 LR3 is not an approved medication; it is widely used as a cell-culture and preclinical research reagent and is sold only as a research chemical.

Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.

References

Primary literature indexed in PubMed for IGF-1 LR3. Listing a study records that it exists and is indexed — it is not a claim of efficacy, a therapeutic indication, or an endorsement of its conclusions. Much of this literature is preclinical (in-vitro or animal-model).

Design and characterisation of long-R3-insulin-like growth factor-I muteins which show resistance to pepsin digestion Growth Factors, 1996. PubMed 8919033
Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig J Endocrinol, 1995. PubMed 7561636

Each reference was checked against its PubMed record on 2026-07-28: the PMID resolves and the title, journal and year match. Where no indexed literature exists for a compound, PeptiDex says so rather than substituting a citation about a different molecule. See the editorial policy.