A PEG-coated version of a 24-amino-acid peptide from an IGF-1 splice variant, sold for muscle repair. It has never been tested in humans.
Also called Pegylated Mechano Growth Factor, PEGylated MGF, Mechano Growth Factor, Pegylated, MGF E-peptide (PEGylated), IGF-1Ec peptide
When a muscle is stretched or damaged, it makes a slightly different version of the IGF-1 gene message, called IGF-1Ec in humans. British physiologist Geoffrey Goldspink's group cloned it in 1996 and called it mechano growth factor (MGF). The product sold as MGF is not that whole protein. It is a synthetic copy of the last 24 amino acids of the variant, the part that differs from regular IGF-1. PEG-MGF is that peptide with a polyethylene glycol chain attached, which is meant to slow its breakdown in the blood.
The evidence is all from cells and animals, and it conflicts. Early lab work reported that the peptide made myoblasts divide and delayed their fusion into muscle fibers, and animal studies reported less damage after heart attacks in sheep and mice. In 2014 scientists at two drug companies tried to repeat the muscle-cell results and could not: the peptide did nothing to myoblasts or muscle stem cells at concentrations up to 500 ng/mL. A 2010 review in Endocrinology also noted that nobody has ever found a natural MGF peptide in cells, tissue or blood.
No study of the PEGylated version has been published at all, in animals or people. In its April 2026 compounding update, FDA said it had found no human exposure data for PEG-MGF and flagged a significant risk of immune reactions. WADA has banned mechano growth factors since 2005.
What it binds to, and what happens inside the body after that, step by step.
The claim is that the MGF E-peptide works through a receptor other than the IGF-1 receptor to wake up muscle stem cells and protect stressed cells from dying. Some cell studies support this; independent attempts to reproduce it did not. The short MGF peptide does not activate the IGF-1 receptor. PEGylation is added to extend how long the peptide survives in the blood, but no data show what it does to activity.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
No human has been given MGF or PEG-MGF in a published study. Animal and cell results are mixed: some labs report muscle stem cell and heart protection effects, but an independent two-company replication found no effect on myoblasts or muscle stem cells. Nothing has been published on the PEGylated form specifically.
8 young (25-36) and 7 older (70-82) adults, muscle biopsies (no MGF was given)
Heavy knee-extension exercise raised MGF mRNA in the young group but not the older group; resting MGF mRNA was about 100 times lower than the main IGF-1 form.
Read the studyC2C12 mouse myoblasts, primary human myoblasts and mouse muscle stem cells
Up to 500 ng/mL of MGF peptide did not increase cell division or slow differentiation, while mature IGF-1 did.
Read the studyMyoblast cell line
The MGF E-domain raised myoblast proliferation and blocked terminal differentiation through a receptor other than IGF-1R.
Read the studySheep with induced heart attacks
The MGF E-domain preserved heart function and left 35% less damaged heart muscle than controls.
Read the studyMice with induced heart attacks plus heart cell cultures
The E-peptide reduced cell death and preserved heart contractility two weeks after the infarct, without activating the IGF-1 receptor.
Read the studyReceptor activation bioassays
The short MGF peptide and the stabilized Goldspink-MGF did not activate the IGF-1 receptor at all; only the full-length protein did.
Read the studyThese are questions the published research has not answered.
No product containing PEG-MGF is approved as a medicine by the FDA.
Never developed as a drug and no human trial is registered. WADA lists mechano growth factors under S2.3 of the 2026 Prohibited List, banned in and out of competition; they have been prohibited since 2005.
No human half-life has been published for PEG-MGF, so we do not draw a clearance curve. Half-lives quoted online for it are usually estimates from animal data.
No human study or approved label has published a dose for PEG-MGF, so there is no table to show.
No dose of PEG-MGF has been tested in a published human study or approved on a label. Numbers that circulate online come from animal studies scaled up by guesswork or from sellers. We do not reproduce them.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
Some early cell work reported this, but a two-company replication found no effect on human myoblasts or mouse muscle stem cells, and no human or PEG-MGF study exists.
Muscle makes more IGF-1Ec mRNA after exercise, but no natural 24-amino-acid MGF peptide has ever been found in tissue or blood. The product is a synthetic fragment with PEG attached.
PEGylation is meant to make molecules circulate longer, which argues against local-only action. No distribution study has been done.
Unpegylated E-peptide reduced damage in sheep and mice. It has never been tested in humans, and the PEGylated product has not been tested even in animals.
The short MGF peptide does not activate the IGF-1 receptor in receptor assays. Only the full-length protein did.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
Promoted on bodybuilding forums as a repair peptide plus a growth peptide.
EvidenceNo human data exist for either one, and no study has combined them.
No manufacturer or published stability data. Freeze-dried peptides are generally kept cold, dry and out of light.
No published stability data for any reconstituted solution.
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