PEG-MGF

PEG-MGF at a Glance

PEG-MGF is a PEGylated version of the E-domain peptide from mechano-growth factor, a splice variant of IGF-1 (IGF-1Ec) that muscle produces in response to mechanical loading and damage. Attaching polyethylene glycol extends its otherwise very short half-life. It is injected as a research chemical for muscle repair on the basis of that endogenous role in regeneration; it has not been developed as a medicine and no human efficacy trial exists.

History & Development

PEG-MGF is a PEGylated version of the MGF E-domain peptide. The PEGylated molecule has never been studied - the research belongs to the uncapped peptide.

First described	Not established - no published study of the PEGylated molecule
Discovered / synthesised by	Not established in the sources consulted for this section
Institution	Not established in the sources consulted for this section
Origin	PEGylated form of the MGF (IGF-1Ec) E-domain peptide
Key patent	Not established in the sources consulted for this section
Assignee	Not established in the sources consulted for this section
Development status	Research chemical - the PEGylated form unstudied; never approved

Discovery

Mechano growth factor is a splice variant of IGF-1 - IGF-1Ec - produced by muscle in response to mechanical loading and damage. Its distinctive C-terminal E-domain is a peptide in its own right, and it appears to act through MAPK-ERK1/2 signalling largely independently of the IGF-1 receptor, which is what separates MGF from IGF-1 proper.

PEGylation - attaching polyethylene glycol - is a standard way to extend a short peptide’s half-life, and the E-domain peptide is cleared quickly.

Development & ownership

No development programme exists, and no study of the PEGylated molecule has been published. Its literature is on the unmodified E-domain peptide: MAPK-ERK signalling, anti-apoptotic effects through caspase-3 suppression, and satellite-cell proliferation, which is itself contested.

The inherited-evidence problem is acute here. PEGylation is not a neutral modification - a large polymer chain changes size, diffusion and receptor access, and in a peptide whose proposed action depends on local tissue signalling after mechanical damage, adding bulk could plausibly impair the very thing being sought. Nobody has measured whether PEG-MGF retains the parent’s activity.

How it reached the market

PEG-MGF is sold as an injectable for muscle repair, typically post-workout on the theory that it mimics the body’s own response to loading. It has never been approved anywhere, the parent peptide’s key claim is contested, and the modified molecule in the vial has no published study of any kind.

What It's Used For

The most important thing here is a molecular one, and everything else follows from it: there are three different substances in this story, and the gray market treats them as one. IGF-1 is the endogenous growth factor with an enormous literature and a genuinely approved recombinant drug (mecasermin/Increlex). MGF — mechano growth factor, or IGF-1Ec — is a splice variant of the IGF-1 gene that muscle transcribes locally after mechanical load or injury; its distinguishing feature is a unique C-terminal “E domain,” and a synthetic 24-amino-acid version of that E domain is what nearly all of the real research below actually used ^{1,2Reference 1Matheny RW Jr et al. · 2010ReviewMinireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration — reviewView study →Reference 2Dai Z et al. · 2010ReviewIGF-IEc expression, regulation and biological function in different tissues — reviewView study →}. PEG-MGF is a third thing: a polyethylene-glycol-conjugated synthetic construct that exists essentially only as a research-chemical product. No published study administered PEG-MGF. Not one of the animal or cell papers cited here used the PEGylated molecule; they used free E-peptide, full-length MGF, plasmid or transgenic gene delivery, or peptide loaded into a scaffold. An IGF-1 result is not an MGF result, and an MGF result is not a PEG-MGF result — that read-across is the entire basis of the product’s marketing, and it is not supported. Route is load-bearing: like all peptides of this size it is oral-inactive and injected, and its own pharmacokinetics are unstudied. There is no registered human trial of PEG-MGF or MGF for any indication, it has never been approved in any jurisdiction, and growth factors of this class are prohibited in sport at all times.

Evidence by IndicationStrength of support · Beta

Support is an experimental score I’m building — a composite weighted by study type (human > animal > in vitro > review) and study volume. It’s a beta: a fast way to rank strength of evidence at a glance, not a validated metric. Each application links down to its write-up. Every score here is capped hard, and for one reason: none of the evidence below was generated with PEG-MGF. It was generated with free MGF E-peptide, full-length MGF, or gene delivery. The scores describe how well an application is supported in animals for the MGF family — not how well the product sold as PEG-MGF is supported, which is not at all. Note also that the muscle score is low for a different reason than the others: it reflects a failed replication, not an absence of testing.

01Cardioprotection after myocardial infarctionShaky26%Replicated animal work (sheep/rat/mouse), multiple independent labs — but free E-peptide, not PEG-MGF; no human trial of any MGF form.

02Neuroprotection & motor-neuron rescueShaky20%Rat nerve-avulsion, ALS-mouse and aging-brain models; mostly plasmid/transgenic gene delivery, not injected peptide. No human data.

03Skeletal-muscle repair & satellite-cell activationShaky18%The marketed use. Human/porcine primary-cell positives directly contradicted by a pharmaceutical-lab replication failure. No human trial; no PEG-MGF study.

04Bone & fracture healingShaky15%Osteoblast cell lines + rabbit radial-defect models, free E-peptide, from a narrow literature. No human fracture data.

Mechanisms

The last row is the one that matters. Every mechanism above was demonstrated with the free peptide or with gene delivery. PEGylation is a covalent modification that can change a peptide’s receptor binding, tissue penetration and cellular uptake, and none of that has been characterized here.

Pharmacokinetics

This is the decision-relevant section, and it is almost entirely empty. MGF is a peptide with negligible oral bioavailability, so all research and community use is by injection (subcutaneous or intramuscular); the product ships as a lyophilized powder for reconstitution. Native MGF is cleared very rapidly — on the order of minutes — and that instability is the entire stated rationale for PEGylation: attaching a polyethylene-glycol chain increases hydrodynamic radius, slows renal clearance and shields the peptide from proteases, which for other pharmaceutical peptides genuinely does extend half-life into hours or days.

But that is PEGylation in general, not PEG-MGF in particular. No peer-reviewed pharmacokinetic study of PEG-MGF could be located: no absorption fraction, no half-life, no clearance, no tissue distribution, and — critically — no test of whether the PEGylated peptide retains E-domain activity at all. The half-life claim on vendor pages is an inference from the chemistry, presented as a measurement. It may well be directionally right; it has simply never been shown for this molecule. Nor is there any published characterization of the marketed material: PEG chain length, attachment site, degree of conjugation and mono- versus poly-PEGylation all change the pharmacology substantially, and none of them are disclosed or verifiable.

The doses and exposure profiles in the cited animal work therefore do not translate. Those studies used free peptide, direct local delivery, or genetic overexpression, all of which produce exposure patterns unrelated to a subcutaneous injection of a PEGylated conjugate. Practical stability and reconstitution parameters for gray-market product are also undocumented.

Clinical & regulatory status

PEG-MGF is an unapproved research chemical. It has never held a marketing authorization from the FDA, EMA, TGA, PMDA or any other regulator, as a drug or as anything else, and it is not a lawful dietary-supplement ingredient in the US, UK or EU — a synthetic analogue of a human growth factor does not meet the dietary-ingredient definition. It is sold labeled “for research use only / not for human consumption.”

There are no registered human clinical trials of PEG-MGF or of MGF. I searched ClinicalTrials.gov directly against the v2 API in July 2026 for “mechano growth factor” and “PEG-MGF”; the returned records are all unrelated studies of IGF-1, recombinant growth hormone, PEG-somatropin or IGF-1R oncology agents that match on keyword only. None is an MGF study. The compound appears in the clinical literature essentially once: a 2026 narrative review in Frontiers in Endocrinology that catalogues unregulated GH–IGF-1-axis performance peptides and lists PEG-MGF among the “IGF-1 analogues” alongside IGF-1 LR3, explicitly stratifying such compounds into evidence tiers down to “a complete absence of human studies” ^{19Reference 19Dominikowski A et al. · 2026ReviewThe emerging landscape of performance-enhancing peptides modulating the GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — review (names PEG-MGF among unregulated IGF-1 analogues)View study →}. That is a review citing it as a clinical problem, not as a therapy.

As a growth factor, MGF falls under the World Anti-Doping Agency Prohibited List Section S2 (peptide hormones, growth factors, related substances and mimetics) and is banned at all times, in and out of competition.

Last checked: July 2026.

Sourcing, Route & Legal Status

Regulatory status. PEG-MGF has no marketing approval anywhere and never has had one — not FDA, EMA, TGA or PMDA, not as a drug and not as a supplement. There is no label, no approved indication, no approved dose, and no pharmacy anywhere in the world that can lawfully dispense it. Unlike compounds with a withdrawn approval or a foreign one, there is no jurisdiction in which a legitimate PEG-MGF product exists. It is not a scheduled substance in the US, but “not scheduled” is not “approved”: marketing it for human use is unlawful in most Western jurisdictions.

This means there is no legitimate source at all, and that is the spine of this section. Because no approved product has ever existed, there is no diverted-pharmaceutical channel, no compounded-from-an-approved-drug channel, and no genuine article for a counterfeit to imitate. 100% of the PEG-MGF supply reaching members of the public is unregulated research-chemical material, synthesized by an unaccountable manufacturer with no GMP oversight and no pharmacopoeial standard. There is no version of buying this compound that is a pharmaceutical.

PEG-MGF carries a verification problem that ordinary gray-market peptides do not. With a simple linear peptide, a mass-spectrometry identity check at least establishes what is in the vial. Here there are two claims to verify and the harder one is routinely unaddressed: that the vial contains the MGF E-domain sequence, and that it is actually PEGylated — at the stated chain length, at the intended attachment site, at a consistent degree of conjugation. PEGylation is the entire product differentiator and the sole justification for the price premium over plain “MGF,” and it is the one attribute a buyer has no realistic means of checking. Nothing about a white lyophilized powder distinguishes PEGylated from non-PEGylated material. Certificates of analysis in this market typically report peptide purity by HPLC, which does not establish conjugation state, and the certificate is supplied by the seller in any case. Independent testing of gray-market peptides routinely finds mislabeled identity, absent or incorrect active content, and bacterial endotoxin — all of which is amplified here because the product is injected rather than swallowed.

How it is supplied and administered. Lyophilized white powder, typically in 2 mg vials, reconstituted by the user with bacteriostatic water and injected subcutaneously or intramuscularly. Oral and transdermal routes cannot deliver an intact peptide of this size, so any oral “MGF” product is pharmacologically inert regardless of the label. Reconstituted material is unstable and is generally refrigerated; the powder is stored cold and protected from light. Self-reconstitution transfers sterile handling, concentration arithmetic and dose measurement to the buyer — all of which a pharmaceutical supply chain exists to remove.

This page does not recommend, review, rank, or link any vendor, and no request will change that. Every result cited here was produced with a characterized research-grade peptide in a laboratory. None of it transfers to a vial of unknown provenance and unverifiable conjugation.

Safety

No human safety data exist for PEG-MGF or for MGF, so “well tolerated” would be a finding and nothing has been measured — its risks are unknown rather than low. For a gray-market injectable, the infection and contamination risks are more probable than any effect of the molecule itself.

Safety at a Glance

❔ Toxicity unknownCardiac caution

• No human safety data at all. No controlled trial of PEG-MGF or MGF has ever been run.
• Theoretical mitogenic concern. Growth-factor signaling could support the growth of a pre-existing or occult tumor.
• Not assessed in pregnancy or breastfeeding. No human or animal reproductive data — see the box below.
• Injection risk is the likely real-world harm. Non-sterile technique and contaminated product cause abscess, cellulitis, sepsis and endotoxin reactions.
• Interactions not assessed. Overlap with GH, IGF-1 or GH secretagogues is class reasoning only.
• The PEGylation itself cannot be verified. Anti-PEG antibody formation and tissue accumulation are unstudied for an undisclosed conjugation chemistry.

Full Safety & Interactions Detail

Human safety data for PEG-MGF do not exist — and neither do they for MGF. No controlled human trial of either molecule has been conducted, so the adverse-effect profile, dose-limiting toxicity and interaction risks in people are genuinely unknown. “Well tolerated” would be a finding; nothing has been measured, so the honest statement is that nothing is known. What class-level observation exists comes from the 2026 review of GH–IGF-1-axis research peptides, which reports that agents in this group are associated as a class with endocrine and metabolic disturbances (including prolactin and cortisol elevations, appetite changes and dysglycemia), fluid-retention syndromes, myalgia and arthralgia, and injection-site reactions ^{19Reference 19Dominikowski A et al. · 2026ReviewThe emerging landscape of performance-enhancing peptides modulating the GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — review (names PEG-MGF among unregulated IGF-1 analogues)View study →} — a class observation drawn largely from other peptides in the same review, not PEG-MGF data.

Mechanism-based concerns (inferred, not observed). MGF signals through proliferative ERK/MAPK pathways within the IGF-1 family. Growth-factor stimulation of cell proliferation carries a theoretical mitogenic and oncogenic risk — the concern is not that it causes cancer but that it could support the growth of a pre-existing or occult tumor. The IGF-1Ec transcript is itself over-expressed in several human cancers in the source literature, which is a flag rather than proof of harm; note the counter-argument from within that literature is that MGF might avoid the oncogenic effects seen with IGF-1 ^{3Reference 3Kandalla PK et al. · 2011In vitroMechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages — in vitro (human primary cells)View study →}, and that too is speculation. Because MGF acts on cardiac tissue, chronic exogenous exposure raises a theoretical cardiac remodeling concern, and one mouse study specifically found that E-peptide treatment did not prevent pathologic hypertrophy post-MI ^{8Reference 8Shioura K et al. · 2014AnimalAdministration of a synthetic peptide derived from the E-domain region of mechano-growth factor delays decompensation following myocardial infarction — animal (mouse)View study →}. None of this is quantified in humans.

A PEGylation-specific unknown. Repeated administration of PEGylated therapeutics is associated in the pharmaceutical literature with anti-PEG antibody formation and, for some products, PEG accumulation in tissue. Whether either applies here is unstudied, and cannot be assessed for a product whose conjugation chemistry is undisclosed.

Injection-specific risks — the most likely real-world harm. Non-sterile technique and contaminated product cause local and systemic infection (abscess, cellulitis, sepsis), injection-site pain, nodules and bruising, and endotoxin reactions. For a gray-market injectable these are more probable than any pharmacological effect of the molecule itself.

Interactions. Not assessed. No controlled interaction data exist. On mechanism alone, overlap with other GH/IGF-axis compounds (exogenous GH, IGF-1 or IGF-1 LR3, GH secretagogues) could compound growth-factor and glucose/insulin effects — that is class reasoning, not an assessed interaction.

Who should avoid it. There is no established safe-use population, so the honest answer is everyone — but the specific flags are: anyone with a current or prior cancer diagnosis or strong family history (proliferative mechanism); anyone pregnant, breastfeeding or trying to conceive; children and adolescents; anyone with cardiac disease; anyone subject to anti-doping testing, since this is a bannable substance under WADA S2; and anyone unwilling to inject a product whose defining chemical feature cannot be verified.

Scope disclosure (honesty, not a claim):

• Human data? None — for PEG-MGF or for MGF. Every study here is animal, cell-culture or gene-delivery work, and none used the PEGylated molecule.
• Interactions assessed? No — none, for any drug class.
• Pregnancy/lactation assessed? No — no human or animal reproductive data located.
• Long-term safety established? No. The absence of adverse-event reports reflects the absence of study, not evidence of safety.

Never imply safety from silence. Where PEG-MGF has not been studied — which is everywhere — the correct statement is “not assessed,” not “safe.”

Pregnancy & Lactation

? Not established in pregnancy? Not established in lactation

Not assessed / not established. There are no human pregnancy or lactation data and no animal reproductive-toxicity data for PEG-MGF or MGF in the accessible literature. Given a growth-factor mechanism and a total absence of safety data, treat as contraindicated by default in pregnancy and breastfeeding.

Dosage

There is no established human dose for PEG-MGF, and none is recommended here. No human trial of PEG-MGF or of MGF has ever been run, so there is no dose-finding data, no maintenance schedule, and no bioavailability figure from which one could be derived. Milligram protocols timed around training sessions circulate widely in vendor copy and forum posts; those are not dose data, they have no experimental basis, and reproducing them here would launder marketing as evidence — so they are not given.

Nor is there a defensible way to back one out of the animal literature. The published doses belong to a different molecule delivered by different routes: 200 nM of free E domain infused in a sheep infarct model ^{6Reference 6Carpenter V et al. · 2008Mechano-growth factor reduces loss of cardiac function in acute myocardial infarction — animal (sheep)View study →}, peptide eluted locally from implanted microrods ^{10Reference 10Peña JR et al. · 2015AnimalLocalized delivery of mechano-growth factor E-domain peptide via polymeric microstructures improves cardiac function following myocardial infarction — animal (mouse)View study →}, plasmid DNA transfected into muscle ^{11,12Reference 11Aperghis M et al. · 2004AnimalDifferent levels of neuroprotection by two insulin-like growth factor-I splice variants — animal (rat, facial-nerve avulsion; cDNA delivery)View study →Reference 12Riddoch-Contreras J et al. · 2009AnimalMechano-growth factor, an IGF-I splice variant, rescues motoneurons and improves muscle function in SOD1(G93A) mice — animal (ALS mouse; plasmid delivery)View study →}, peptide injected directly into a rabbit bone defect ^{14Reference 14Deng M et al. · 2011In vitroMechano growth factor E peptide promotes osteoblasts proliferation and bone-defect healing in rabbits — in vitro + animal (rabbit)View study →}. Converting any of those into a subcutaneous milligram figure for a PEGylated conjugate of unknown half-life is not an estimate, it is a guess. Oral MGF products cannot deliver intact peptide at all (see Pharmacokinetics). This entry is informational only and is not an endorsement of use.

References

1. Matheny RW Jr, et al. (2010). Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration — review. Endocrinology. https://pubmed.ncbi.nlm.nih.gov/20130113/
2. Dai Z, et al. (2010). IGF-IEc expression, regulation and biological function in different tissues — review. Growth Hormone & IGF Research. https://pubmed.ncbi.nlm.nih.gov/20494600/
3. Kandalla PK, et al. (2011). Mechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages — in vitro (human primary cells). Mechanisms of Ageing and Development. https://pubmed.ncbi.nlm.nih.gov/21354439/
4. Qin LL, et al. (2012). Mechano growth factor (MGF) promotes proliferation and inhibits differentiation of porcine satellite cells — in vitro. Molecular and Cellular Biochemistry. https://pubmed.ncbi.nlm.nih.gov/22875667/
5. Fornaro M, et al. (2014). Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cells — in vitro (replication failure). American Journal of Physiology — Endocrinology and Metabolism. https://pubmed.ncbi.nlm.nih.gov/24253050/
6. Carpenter V, et al. (2008). Mechano-growth factor reduces loss of cardiac function in acute myocardial infarction — animal (sheep). Heart, Lung & Circulation. https://pubmed.ncbi.nlm.nih.gov/17581790/
7. Stavropoulou A, et al. (2009). IGF-1 expression in infarcted myocardium and MGF E peptide actions in rat cardiomyocytes in vitro — animal (rat) + in vitro. Molecular Medicine. https://pubmed.ncbi.nlm.nih.gov/19295919/
8. Shioura K, et al. (2014). Administration of a synthetic peptide derived from the E-domain region of mechano-growth factor delays decompensation following myocardial infarction — animal (mouse). International Journal of Cardiovascular Research. https://pubmed.ncbi.nlm.nih.gov/25606570/
9. Mavrommatis E, et al. (2013). The E-domain region of mechano-growth factor inhibits cellular apoptosis and preserves cardiac function during myocardial infarction — in vitro + animal (mouse). Molecular and Cellular Biochemistry. https://pubmed.ncbi.nlm.nih.gov/23712705/
10. Peña JR, et al. (2015). Localized delivery of mechano-growth factor E-domain peptide via polymeric microstructures improves cardiac function following myocardial infarction — animal (mouse). Biomaterials. https://pubmed.ncbi.nlm.nih.gov/25678113/
11. Aperghis M, et al. (2004). Different levels of neuroprotection by two insulin-like growth factor-I splice variants — animal (rat, facial-nerve avulsion; cDNA delivery). Brain Research. https://pubmed.ncbi.nlm.nih.gov/15120599/
12. Riddoch-Contreras J, et al. (2009). Mechano-growth factor, an IGF-I splice variant, rescues motoneurons and improves muscle function in SOD1(G93A) mice — animal (ALS mouse; plasmid delivery). Experimental Neurology. https://pubmed.ncbi.nlm.nih.gov/19038252/
13. Tang JJ, et al. (2017). Mechano growth factor, a splice variant of IGF-1, promotes neurogenesis in the aging mouse brain — animal (mouse, transgenic). Molecular Brain. https://pubmed.ncbi.nlm.nih.gov/28683812/
14. Deng M, et al. (2011). Mechano growth factor E peptide promotes osteoblasts proliferation and bone-defect healing in rabbits — in vitro + animal (rabbit). International Orthopaedics. https://pubmed.ncbi.nlm.nih.gov/21057789/
15. Wei W, et al. (2020). MGF-19E peptide promoted proliferation, differentiation and mineralization of MC3T3-E1 cell and promoted bone repair — in vitro + animal (rabbit). Gene. https://pubmed.ncbi.nlm.nih.gov/32339623/
16. Wei X, et al. (2022). Improved muscle regeneration into a joint prosthesis with mechano-growth factor loaded within mesoporous silica — animal (in vivo, scaffold delivery). ACS Nano. https://pubmed.ncbi.nlm.nih.gov/36053268/
17. Sun KT, et al. (2018). Overexpression of mechano-growth factor modulates inflammatory cytokine expression and macrophage resolution in muscle injury — animal (mouse, overexpression). Frontiers in Physiology. https://pubmed.ncbi.nlm.nih.gov/30140235/
18. Iida K, et al. (2004). Muscle mechano growth factor is preferentially induced by growth hormone in growth hormone-deficient lit/lit mice — animal (mouse, regulation). The Journal of Physiology. https://pubmed.ncbi.nlm.nih.gov/15308683/
19. Dominikowski A, et al. (2026). The emerging landscape of performance-enhancing peptides modulating the GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — review (names PEG-MGF among unregulated IGF-1 analogues). Frontiers in Endocrinology. https://pubmed.ncbi.nlm.nih.gov/42395176/

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