IGF-1 LR3
Also known as: Long R3 IGF-1, IGF-1 Long Arg3
IGF-1 LR3 (also called Long R3 IGF-1 or IGF-1 Long Arg3) is a modified IGF-1 analog. IGF-1 LR3 is a modified analog carrying an arginine substitution for glutamate at position 3 plus a thirteen-residue N-terminal extension. Both changes reduce affinity for IGF binding proteins, which normally sequester the great majority of circulating IGF-1.
For research use only.
Key Facts
- CAS
- 143045-27-6
- Molecular Weight (MW)
- Reported ≈9.1 kDa (supplier-dependent)
- Half-life
- Longer than native IGF-1 in vitro; human PK not established in labels
- FDA status
- Not Approved
- Evidence level
- Insufficient Evidence
- Human dose established
- No
- Administration Route
- Not established in humans
- Frequency
- Not established in humans
- Last updated
- Sep 26, 2026
- Reviewed
- Aug 30, 2026
- Targets
- IGF-1 receptor
Vendor price snapshot
Each vendor counts once, at the median price per mg of its own listings; the typical range is the middle half of vendors. From public vendor listings collected between Dec 2025 and Oct 2026, so confirm the live price on the vendor site. Peptide Library does not sell peptides.
- Vendors listing this peptide
- 32
- Listed offers
- 63
- Median price per mg
- $74.99/mg
- Typical $61.50–$94.72/mg
Research summary
Modified analog of insulin-like growth factor 1 carrying an arginine substitution at position 3 plus a thirteen-residue N-terminal extension, both of which reduce binding to IGF binding proteins. With less of the peptide sequestered, a larger free fraction remains available to the IGF-1 receptor and activity persists longer than native IGF-1. It is a research reagent with no approved use and no controlled human safety data. Prohibited in sport under WADA class S2.
Peptide Library's IGF-1 LR3 profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
IGF-1 LR3 dosage: no established human dose
IGF-1 LR3 has no established human dosage. No trial of it is registered on ClinicalTrials.gov and no human study of it is indexed in PubMed. The published work is protein-expression and animal research. Its parent molecule, recombinant human IGF-1 (mecasermin), is a separate approved product with its own weight-based dosing, and that dosing does not transfer to this analogue.
No established human dosage.
Human clinical evidence: None identified.
Preclinical research: IGF-1 LR3 is an engineered analogue of insulin-like growth factor 1 with an arginine substitution and a 13-residue N-terminal extension, designed to reduce binding to IGF binding proteins and so extend its activity. It was developed as a cell-culture reagent for increasing recombinant protein yield, which is what most of the literature covers. No human study of it is indexed, so there is no human dose, route or interval to report, and animal IGF-1 dosing is not converted into one here.
Animal dosing is not converted into a human dose anywhere on this page. Where research figures appear below, they are reported as studied, not recommended.
| Human dosing established | No |
|---|---|
| Route | Not established in humans |
| Evidence level | Insufficient Evidence |
| Last reviewed | 2026-09-05 |
Preclinical and analog research
Not human dosing evidence. Listed for completeness and never extrapolated to a human dose.
| Study / context | Population | Dose | Route | Frequency | Duration | Outcome studied | Source |
|---|---|---|---|---|---|---|---|
| Recombinant expression researchPreclinical · Biotechnology study | Laboratory expression system | Not applicable — protein production study | Not applicable | — | — | Expression of IGF-1 and LR3 IGF-1 in Pichia pastoris | Recombinant expression of IGF-1 and LR3 IGF-1 fused with xylanase in Pichia pastoris. Appl Microbiol Biotechnol. 2023. |
| Animal growth study — recombinant IGF-1Preclinical · Preclinical, ovine recombinant IGF-1 rather than LR3Studied an analog, not IGF-1 LR3 itself | Fetal sheep | Model-specific; not convertible to a human dose | Infusion | — | — | Organ-specific growth | Sheep recombinant IGF-1 promotes organ-specific growth in fetal sheep. Front Physiol. 2022. |
Where sources disagree
- Protocols of 20–100 mcg daily are widely published for IGF-1 LR3. No human study of the analogue is indexed in PubMed and no trial is registered, so no primary source for those figures could be identified.
- Recombinant human IGF-1 (mecasermin) is an approved product with established weight-based dosing for severe primary IGF-1 deficiency. IGF-1 LR3 is a different, deliberately longer-acting molecule; mecasermin's labelling is not dosing evidence for it.
- Database searches for "LR3" return a large number of unrelated results from liver imaging classification (LI-RADS LR-3), which inflates apparent evidence volume for this compound.
Reconstitution
Common research vial sizes: 1 mg.
| Vial | Bacteriostatic water | Concentration | Per 0.01 mL |
|---|---|---|---|
| 1 mg | 1 mL | 1 mg/mL | 10 mcg per 0.01 mL |
These figures are arithmetic only — they convert a vial and a volume into a concentration. They are not a recommendation to take any dose.
Calculate reconstitution & dose →Handling & administration
- Timing Notes
- Not an approved drug; variable quality on the gray market
Sequence & molecular data
| Molecular formula | Reported ≈C400H625N111O115S9 (recombinant analog) |
|---|---|
| Molecular weight | Reported ≈9.1 kDa (supplier-dependent) |
| CAS number | 143045-27-6 |
| Half-life | Longer than native IGF-1 in vitro; human PK not established in labels |
| Appearance | White lyophilized powder (recombinant protein/peptide) |
| Formulation | Lyophilized Powder |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
IGF-1 LR3 is a modified analog carrying an arginine substitution for glutamate at position 3 plus a thirteen-residue N-terminal extension. Both changes reduce affinity for IGF binding proteins, which normally sequester the great majority of circulating IGF-1. With less of the peptide bound, a larger free fraction remains available to activate the IGF-1 receptor, and the effective duration of bioactivity is longer than native IGF-1 despite similar receptor affinity. The trade-off is loss of the buffering that binding proteins normally provide. It is a research reagent with no approved use and no controlled human safety data.
Origin
Engineered IGF-1 analog.
Targets
Studies
- IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep
- Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration
- Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets
- The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration
- Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice
Regulatory & research status
IGF-1 LR3 is not an FDA-approved product. It is sold for laboratory research and has no approved medical use.
| FDA status | Not Approved |
|---|---|
| Availability | Research-Only |
| WADA (sport) | Banned in Sport |
| Library classification | Research-Only |
Benefits
IGF-1 LR3 side effects
IGF-1 LR3 has no controlled human safety data. The effects below are reported, not established, and absence from the list is not evidence of safety.
Side Effects
- Hypoglycemia risk
- Uncharacterized human AE profile
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
IGF-1 LR3: frequently asked questions
What is IGF-1 LR3?
Modified analog of insulin-like growth factor 1 carrying an arginine substitution at position 3 plus a thirteen-residue N-terminal extension, both of which reduce binding to IGF binding proteins. With less of the peptide sequestered, a larger free fraction remains available to the IGF-1 receptor and activity persists longer than native IGF-1. It is a research reagent with no approved use and no controlled human safety data. Prohibited in sport under WADA class S2.
What are the side effects of IGF-1 LR3?
IGF-1 LR3 has no controlled human safety data, so its side-effect profile is not well established. Effects recorded on this profile include hypoglycemia risk. It is on the WADA Prohibited List for athletes. This is reference information, not medical advice.
How does IGF-1 LR3 work?
IGF-1 LR3 is a modified analog carrying an arginine substitution for glutamate at position 3 plus a thirteen-residue N-terminal extension. Both changes reduce affinity for IGF binding proteins, which normally sequester the great majority of circulating IGF-1.
Is IGF-1 LR3 FDA approved?
No. IGF-1 LR3 is not approved by the FDA for any indication and is categorised as research-only. It has not been reviewed for safety or efficacy as a medicine, and published research should be read as investigation rather than established use.
What is the half-life of IGF-1 LR3?
Reported half-life for IGF-1 LR3 is Longer than native IGF-1 in vitro; human PK not established in labels. Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.
Is IGF-1 LR3 banned in sport?
IGF-1 LR3 is recorded here as prohibited in sport. Athletes subject to anti-doping rules should check the current WADA Prohibited List directly, since it is revised annually and classifications change.
What peptides are similar to IGF-1 LR3?
Compounds most often compared with IGF-1 LR3 include IGF-1 (overview), Mecasermin, IGF-1 DES and MGF. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.
References
- WADA Prohibited List 2026External reference
- IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep — Am J Physiol Endocrinol Metab, 2025External reference
- Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration — Int J Biol Macromol, 2025External reference
- Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets — J Dev Orig Health Dis, 2023External reference
- The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — Front Endocrinol (Lausanne), 2026External reference
- Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice — J Alzheimers Dis, 2025External reference
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Sep 26, 2026 · Version 4
This IGF-1 LR3 profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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