IGF-1 LR3: Compound Profile

IGF-1 LR3 is one of the more extensively referenced analogues of insulin-like growth factor 1 in the growth-factor and cell-culture literature. The two structural edits that define it change how the molecule interacts with the IGF-binding proteins that normally chaperone native IGF-1, which is why it recurs so often in receptor-signaling and serum-free culture research. This profile covers what it is relative to its parent protein, the mechanism the literature attributes to it, and where it sits among IGF-1 analogues. For the adjacent upstream axis, see the growth-hormone secretagogues overview.

What is IGF-1 LR3?#

IGF-1 LR3 is a synthetic analogue of insulin-like growth factor 1 (IGF-1), the anabolic growth factor encoded by the human IGF1 gene. It differs from native IGF-1 in two ways. First, the glutamate at position 3 is replaced by arginine, the substitution the "R3" in the name records. Second, a 13-residue peptide (MFPAMPLLSLFVN) is fused to the N-terminus, giving the "Long" prefix and taking the chain to 83 residues. Together these edits are reported to lower the analogue's affinity for the IGF-binding proteins that sequester native IGF-1 in solution, which is the property that makes it a common tool in cell-culture research. The reference identity anchor here is the parent protein IGF-1 itself, since that sequence and annotation are canonical.

What does the research literature study?#

The mechanistic backdrop is the IGF-1 receptor. Recent work characterizes how IGF1R-dependent signaling regulates cellular events such as blastocyst formation in early embryonic models, a representative example of the receptor biology the analogue is used to probe. Against that backdrop, the IGF-1 LR3 literature clusters into a few areas. In protein-expression research, one study reports the recombinant expression of IGF-1 and LR3 IGF-1 in Pichia pastoris, fusing the analogue to xylanase to study yield in a yeast system. In cell-proliferation modeling, IGF-1 signaling is examined for its role in collagen deposition by dermal fibroblasts in a tissue-engineering context. And in whole-animal physiology, the analogue itself has been used as an experimental probe: a fetal-sheep study reports that IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetuses, a related model examines glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion, and a rodent study tracks intranasal long R3 IGF-1 and amyloid-plaque remodeling in a transgenic model. All of this is preclinical research in cell culture and animals, and none of it speaks to effects in people.

Where IGF-1 LR3 sits among IGF-1 analogues#

IGF-1 LR3 is a downstream effector analogue: it engages the IGF-1 receptor directly. That places it a step below the growth-hormone secretagogues, which act upstream on the pituitary rather than at the growth-factor receptor. Within the IGF-1 analogue family itself, the two common laboratory variants take opposite structural approaches. IGF-1 LR3 adds mass and charge (an N-terminal extension plus the R3 substitution) to reduce binding-protein affinity, whereas the truncated IGF-DES analogue removes the first three N-terminal residues to the same functional end. Both are studied as tools for reading IGF-1R signaling in serum-free systems where native IGF-1 would otherwise be tied up by its binding proteins.

Handling and storage#

IGF-1 LR3 is supplied as a lyophilized solid and dissolved prior to use. As a larger protein analogue rather than a short linear peptide, it is more prone to shear and aggregation, so gentle handling matters: the reconstitution primer covers solvent selection and swirling rather than vortexing, while the cold-chain article covers how stability changes once the powder is in solution and why freeze-thaw cycles are minimized.

Sources and further reading#

• Insulin-like growth factor 1, UniProt P05019: canonical sequence and annotation for the parent protein of the LR3 analogue.
• IGF1R-dependent signaling regulates blastocyst formation during early embryonic development (PMID 41799434): a mechanistic account of IGF-1 receptor signaling in a developmental model. Frontiers in Cell and Developmental Biology 2026.
• Recombinant expression of IGF-1 and LR3 IGF-1 fused with xylanase in Pichia pastoris (PMID 37261455): protein-expression research on the LR3 analogue in a yeast system. Applied Microbiology and Biotechnology 2023.
• IGF-1 increases collagen deposition by dermal fibroblasts: applications for tissue engineering (PMID 42274614): a cell-proliferation model of IGF-1 signaling in cultured fibroblasts. Cells 2026.
• IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep (PMID 39679943): a preclinical whole-animal study using the LR3 analogue as an experimental probe. American Journal of Physiology-Endocrinology and Metabolism 2025.
• Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep (PMID 37114757): a preclinical infusion model examining islet signaling. Journal of Developmental Origins of Health and Disease 2023.
• Intranasal long R3 IGF-1 treatment promotes amyloid plaque remodeling in cerebral cortex of 5XFAD mice (PMID 39610283): a rodent CNS model using the LR3 analogue. Journal of Alzheimer's Disease 2025.