IGF-1 LR3 vs PEG-MGF
IGF-1 LR3 (IGF-1 analog (Long R3 IGF-1 variant)) and PEG-MGF (IGF-1 splice variant analog (PEGylated Mechano Growth Factor)) are documented as co-studied in the PeptiDex library. This page puts the two entries side by side on class, molecular weight, half-life, origin, mechanism and studied research areas — every value taken from the entry it belongs to.
Why these two are co-studied
Cross-referenced for research context — not a usage or combination recommendation.
At a glance
| Attribute | IGF-1 LR3 | PEG-MGF |
|---|---|---|
| Compound class | IGF-1 analog (Long R3 IGF-1 variant) | IGF-1 splice variant analog (PEGylated Mechano Growth Factor) |
| Research category | Growth & GH-Axis | Growth & GH-Axis |
| Length (amino acids) | 83 amino acids | 24 amino acids |
| Molecular weight | Approximately 9111 g/mol | ~2867 Da (peptide core, excluding PEG) |
| Half-life | Substantially longer than native IGF-1; reported on the order of many hours (approximately 20-30 hours) due to reduced IGFBP binding | Extended relative to unmodified MGF due to PEGylation (reported on the order of days), though precise values are not well established |
| Origin | 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. | PEG-MGF is a PEGylated form of Mechano Growth Factor (MGF), a splice variant of insulin-like growth factor 1 (IGF-1Ec in humans) produced in response to mechanical loading and muscle damage. The MGF peptide corresponds to the unique C-terminal E-domain of this IGF-1 splice variant; PEGylation is added to extend its otherwise very short half-life. |
“Not documented” means the PeptiDex entry records no value for that field. Nothing on this page is estimated, and no figure is carried over from one compound to the other.
How IGF-1 LR3 works
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.
How PEG-MGF works
MGF is a splice variant of IGF-1 whose distinctive C-terminal E-domain is implicated in activating muscle satellite (stem) cells and promoting local muscle repair and hypertrophy after mechanical stress, with actions that appear partly independent of the classical IGF-1 receptor. PEGylation (attachment of polyethylene glycol) protects the peptide from rapid degradation and clearance, substantially extending its half-life compared with native MGF. Much of the mechanistic detail remains at the preclinical/research level.
Mechanistic descriptions reflect published research-literature understanding and are quoted from each compound's own entry. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
Where each one appears in the literature
The research contexts each entry documents. Listing a research area is not a claim of efficacy or a therapeutic indication, and the two lists are not scored against each other.
IGF-1 LR3
PEG-MGF
What sets each apart
IGF-1 LR3
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.
PEG-MGF
PEG-MGF is based on a mechanically induced IGF-1 splice variant (MGF) rather than mature IGF-1, and PEGylation gives it a long half-life while the peptide's focus is local muscle repair via satellite cells.
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 is PEG-MGF?
PEG-MGF is a pegylated form of Mechano Growth Factor (MGF), itself a 24-amino-acid C-terminal splice variant of IGF-1 (IGF-1Ec) produced in response to mechanical stress. Attaching a polyethylene glycol (PEG) group greatly extends its otherwise very short circulating half-life.
How does PEG-MGF differ from regular MGF?
Native MGF has a half-life of only about 5-7 minutes, limiting it to localized action. PEGylation extends the half-life substantially (reported hours to days), so PEG-MGF is studied for systemic subcutaneous administration rather than the site-specific injection unmodified MGF requires.
How does MGF relate to IGF-1?
MGF is an alternative splice variant of the IGF-1 gene (IGF-1Ec) with a unique C-terminal peptide. It is studied for a distinct role in activating muscle satellite cells and tissue repair, separate from the systemic growth signaling of mature IGF-1.
Answers are the ones published on each compound's own PeptiDex entry. They are educational summaries of research-literature context and are not medical advice.