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Research use only
· 7 min read
Most research-peptide names are marketing. "IGF-1 LR3" is closer to a spec sheet: the "LR3" encodes exactly two deliberate edits to native insulin-like growth factor I - a Long 13-residue N-terminal extension, and an arginine-for-glutamate swap at position 3 (Glu3 to Arg3). Native IGF-I runs to 70 residues; this engineered analogue runs to 83. The literature that matters for it is structural and in-vitro rather than clinical, and that is the lens this page takes: verified chemistry, the IGF-1-receptor-versus-binding-protein profile the structural work describes, the published study record by design and endpoint name only, and bench handling. Kovalabs supplies IGF-1 LR3 strictly as a research reagent; everything below describes what published studies investigated, not any human use.
| Compound | IGF-1 LR3 (Long-[Arg3]-IGF-I) |
|---|---|
| Synonyms / dev terms | Long R3 IGF-1, LR3-IGF-I, Long-[Arg-3]-insulin-like growth factor I |
| Class / mechanism | Recombinant IGF-I analogue; IGF-1 receptor (IGF-1R) ligand with reduced IGF-binding-protein (IGFBP) affinity |
| Molecular formula | C400H625N111O115S9 |
| Molecular weight | Approximately 9118 g/mol (about 9.1 kDa) |
| CAS number | 143045-27-6 |
| PubChem CID | Omitted (no PubChem record verifiably resolves to this 83-residue protein) |
On paper the chemistry is tidy. IGF-1 LR3 carries the molecular formula C400H625N111O115S9 and a molecular weight of approximately 9118 g/mol (about 9.1 kDa), figures that are mutually consistent and that agree across reference sources for an 83-residue protein. The Long 13-residue N-terminal extension is reported as the single-letter sequence MFPAMPLSSLFVN - the same Met-Phe-Pro-Ala-Met-Pro-Leu-Ser-Ser-Leu-Phe-Val-Asn extension spelled out in the primary literature (Zhao et al., Journal of Endocrinology, 1993). Chemistry references list the analogue under CAS number 143045-27-6, paired with the correct 83-residue sequence and the C400H625N111O115S9 formula.
The one identifier missing above is the PubChem CID, and its absence is deliberate. An adversarial cross-check could not resolve a single PubChem record that round-trips against the name, formula and mass at the same time: the candidate records returned by database cross-references either describe a small lipid-like molecule of a completely different formula and mass, or are empty and unverifiable. Following the omit-rather-than-guess rule, the CID is left out until a record can be confirmed to round-trip against the name, formula and weight. The molecule's identity itself is sound and corroborated by the primary structural literature; only the database accession is withheld. A supplier that quotes a confident CID for this particular analogue is worth a second look, because the obvious candidates do not survive the check. Purity and identity ship documented on every batch through the certificate of analysis.
| Feature | Native human IGF-I | IGF-1 LR3 (Long-[Arg3]-IGF-I) |
|---|---|---|
| Residue count | 70 residues | 83 residues |
| Position 3 residue | Glutamate (Glu3) | Arginine (Arg3) substitution |
| N-terminal extension | None | 13-residue hydrophobic extension |
| Receptor binding domain | IGF-1R binding domain | IGF-1R binding domain retained |
| IGFBP affinity (as described in the structural literature) | Binds IGF-binding proteins | Reported lower affinity for IGFBPs |
| Molecular origin | Endogenous / recombinant | Recombinant engineered analogue |
The two engineered features distinguish IGF-1 LR3 from native IGF-I cleanly, and each has a structural paper behind it. First, the Arg3 substitution and the N-terminal extension are reported, in the structural literature, to lower the analogue's affinity for the IGF-binding proteins relative to native IGF-I, while the IGF-1 receptor binding domain is retained (Laajoki et al., FEBS Letters, 1997). That is described as a molecular-pharmacology property of the construct - a receptor-versus-binding-protein interaction profile, nothing more. Second, the solution structure was resolved directly. Using 1H,15N multidimensional NMR spectroscopy on 15N-labelled material, the IGF-I domain of Long-[Arg-3]-IGF-I was found to adopt an almost identical secondary structure to native IGF-I; the first seven residues of the N-terminal extension are largely unstructured, while the following five form a turn-like element positioned spatially near the start of helix 1 of the IGF-I domain (Laajoki et al., 1997). In other words the bolt-on extension does not refold the protein - it mostly dangles. These are structural-characterisation findings about the molecule itself; no biological effect is asserted by them.
The published IGF-1 LR3 literature spans receptor pharmacology, cell-culture and animal models. Each item below is described strictly by what the study set out to measure - study design and endpoint name only, with no result, effect size or benefit asserted.
No registered human clinical trials of this specific analogue were found in a ClinicalTrials.gov search. Native IGF-1 (mecasermin) is a separate licensed molecule and must not be conflated with this analogue; the shared three letters in the name are where the resemblance ends. These entries are listed as research context, not as findings a reader should expect.
The practical point that sets IGF-1 LR3 apart from the short peptides elsewhere in the catalogue is size: at roughly 9.1 kDa it is a small protein, not a 6-to-10-residue peptide, and proteins denature under mechanical and shear stress that a short peptide shrugs off. IGF-1 LR3 is supplied as a lyophilised (freeze-dried) powder. As a sealed lyophilate it is generally reported stable for extended periods when held frozen, and for shorter periods at refrigerator temperature, kept dry and protected from repeated warming. Reconstitution is a routine dissolution step in which an appropriate laboratory solvent is added slowly down the inner wall of the vial and the powder is allowed to dissolve without agitation - precisely because shear can denature a protein of this size. Once in solution it is kept cold and used promptly for analysis; as a protein it is sensitive to repeated freeze-thaw cycles, heat and prolonged light or oxidative exposure, and oxidised forms have been documented analytically. None of this constitutes a preparation method for any use in humans or animals; it is bench handling of a reagent. Exact shelf life depends on buffer, concentration and aseptic conditions and should be validated by the end user. See the reconstitution guide for general laboratory handling.
With a protein reagent, purity and identity should be verifiable rather than assumed: every Kovalabs batch ships with a certificate of analysis, so the mass and purity of the material in hand can be checked against the documented identifiers (formula C400H625N111O115S9, CAS 143045-27-6) rather than taken on trust. Researchers working across the same axis may also reference tesamorelin, a growth-hormone-releasing-hormone analogue that acts upstream on a distinct receptor, within the GH-axis research peptides catalogue.
As a regulatory note rather than any statement about use, IGF-1 LR3 falls within Section S2 of the WADA Prohibited List (Peptide Hormones, Growth Factors, Related Substances and Mimetics) as an IGF-1 / IGF-1-receptor agonist, prohibited at all times, in and out of competition. This is included strictly as an anti-doping classification. IGF-1 LR3 is a research-use compound and no human use is implied or endorsed by stating its regulatory status.
Tier one is solid: the chemistry. The C400H625N111O115S9 formula, the approximately 9118 g/mol mass, the CAS 143045-27-6 listing and the 83-residue sequence agree across references, the solution structure has been resolved directly by NMR, and the molecule has been detected and characterised by high-resolution mass spectrometry. Tier two is the middle ground: the mechanism work is real but lives in cell culture and animal models - receptor and binding-protein interaction profiles, phosphorylation and proliferation endpoints, and assorted reproductive and physiology readouts. A cell in a dish is not a person, and several of those endpoints are named, not shown, with at least one explicit null result on record. Tier three is the weakest: human evidence is absent - no registered clinical trials of this specific analogue were found. It is not a licensed medicine, and it has not been shown to produce defined outcomes in humans. Curiosity is warranted; certainty is not.
IGF-1 LR3 is supplied by Kovalabs for laboratory and in-vitro research only. It is not a medicine, not a supplement, and not for human or veterinary use, and nothing on this page describes a dose, a route, a schedule or an outcome. It is a research compound that has not been evaluated by the MHRA or any comparable regulator for safety or efficacy in humans or animals. Every batch is third-party tested with a certificate of analysis. See the full research disclaimer for terms.
No. IGF-1 LR3 (Long-[Arg3]-IGF-I) is a research compound. It has not been approved as a medicine by the MHRA or any comparable regulator, and Kovalabs supplies it strictly as a research reagent for laboratory use, not for human or veterinary use. Native IGF-1 (mecasermin) is a separate licensed molecule and should not be confused with this analogue.
It is an engineered recombinant analogue of human insulin-like growth factor I. It is an 83-residue construct carrying the IGF-I sequence with an arginine-for-glutamate substitution at position 3 and a 13-residue hydrophobic N-terminal extension, first characterised in vitro by Francis et al. (1992) and Zhao et al. (1993).
By residue count and binding profile. Native IGF-I is 70 residues; IGF-1 LR3 is 83 residues with the Arg3 substitution and the N-terminal extension. The structural literature reports that those changes lower its affinity for the IGF-binding proteins relative to native IGF-I, while the IGF-1 receptor binding domain is retained (Laajoki et al., 1997).
Its molecular formula is C400H625N111O115S9 with a molecular weight of approximately 9118 g/mol (about 9.1 kDa), and chemistry references list the CAS number 143045-27-6. No PubChem CID is published here, because no PubChem record could be verified to resolve to this specific 83-residue protein; it is omitted rather than guessed.
As bench handling of a research reagent only. The lyophilised powder is generally held frozen for longer-term storage and protected from repeated warming, with care taken over freeze-thaw cycles. Reconstitution is a dissolution step in a suitable laboratory solvent, added gently to avoid shear stress on a protein of this size, after which the solution is kept cold and used promptly. None of this is a preparation method for any use in humans or animals; see the reconstitution guide for general laboratory handling.
It falls within Section S2 of the WADA Prohibited List as an IGF-1 / IGF-1-receptor agonist, prohibited at all times, in and out of competition. This is stated only as a regulatory classification for a research-use compound, not as a comment on any use.