PEG-MGF
Pegylated Mechano Growth Factor
Evidence grade 1 of 5, Untested. Read how the Atlas grades evidence.
PEG-MGF is a pegylated form of mechano growth factor (the IGF-1Ec splice variant discovered by Goldspink and Yang) engineered to extend a several-minute half-life into hours for once-weekly research dosing. No human clinical trial of injected MGF or PEG-MGF has been published; the muscle-repair and satellite-cell claims rest on animal and in-vitro work such as Hill and Goldspink's satellite-cell studies and the SOD1G93A mouse model, so an honest grade is 1 (animal-only / anecdotal).
Counted on the record: 0 human studies, 0 randomized trials, 0 participants, 0 animal studies, 2 lab studies.
The zeroes apply to administered PEG-MGF human studies. Endogenous MGF expression research is excluded.
- FDA
- Not Approved
- WADA
- Prohibited at all times (WADA S2.2 growth factors, MGFs named explicitly)
Reference only. Not medical advice.
What can go wrong
WADA-prohibited; no human data; PEGylation raises its own safety questions.
Talk to a clinician before taking this, particularly if you have any history of cancer. The Atlas can tell you what has been studied about PEG-MGF. It cannot tell you how it would interact with your body, your history, or anything else you are taking, and nothing on this page is a reason to start.
A PEGylated MGF with a dramatically extended half-life (days vs. minutes), allowing once-weekly dosing. No clinical data.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
How it is supposed to work
PEG-MGF is Mechano Growth Factor with a polyethylene-glycol chain attached to slow its breakdown. Plain MGF lasts only minutes; pegylation extends that to days and lets it circulate systemically, binding where muscle damage has occurred. The intended effect is the same as MGF, activating muscle satellite cells to drive repair and growth, but with a longer, body-wide window rather than a brief local pulse.
- Step 1PEG chainA polyethylene-glycol chain slows its breakdown, extending its life from minutes to days.
- Step 2Systemic reachIt circulates body-wide and binds where muscle damage has occurred.
- Step 3Satellite cellsThe intended effect matches MGF: activating muscle satellite cells to drive repair and growth.
MGF with a polyethylene glycol coat attached.
- Type
- Pegylated MGF
- Parent
- IGF-1 splice variant
- Modification
- Polymer coat for half-life
- Human trials
- None
- Approved
- No
- Sport
- Prohibited
A Longer-Lasting MGF, With All Of MGF’s Unknowns
PEG-MGF adds nothing new to the science beyond duration, so the MGF entry covers what matters. MGF is a real, well-mapped splice variant of a growth factor, with a coherent biological story about muscle repair, and essentially no human trial evidence to support the muscle-building claims made for the injected peptide. Pegylation makes it last longer, which is a manufacturing and delivery refinement, not new proof of benefit. It also does not change, and arguably sharpens, the central caution: this is a member of the insulin-like growth factor family, and that family promotes cell growth and proliferation, which is why a cancer-risk question hangs over it. It remains unapproved and prohibited in sport.
How it is taken
Research
A patent names PEG-MGF as one possible PEGylated therapy used after a separate anti-PEG-antibody hydrogel. This does not establish PEG-MGF product contents, vial form, administration formulation, or storage stability. Patent concept only; no direct PEG-MGF preparation or experiment is described.
Injection
Recorded because this entry documents injectable use. The Atlas holds no vial, reconstitution or storage detail for it.
The listing's pharmacokinetics text refers to subcutaneous injection
Safety in detail
- It belongs to the insulin-like growth factor family, which promotes cell growth, so a cancer question hangs over it.
- Preparations vary widely in PEG size and linker chemistry, so batches differ from each other.
Children and teenagers
PEG-MGF has no validated pediatric use and is an unapproved injected growth-factor peptide. There is no appropriate pediatric use.
What people get wrong
Often saidPEG-MGF has human muscle-building trials
ActuallyNo direct human intervention study of PEG-MGF was found. Human evidence in this area measures the body's own MGF-related expression after exercise rather than administering PEG-MGF.
Often saidPEGylation only makes natural MGF last longer without changing anything else
ActuallyPEGylation changes exposure and distribution. Direct pharmacokinetic and safety data for PEG-MGF are absent, so a longer half-life and its consequences cannot be treated as established facts.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
PEG-MGF reaches users through the gray-market peptide economy aimed at muscle growth and recovery, the same channels as MGF and the regenerative peptides. There is no approved product, and its market runs on a coherent biological story without human proof.
How we got here
Mechano growth factor was identified in the late 1990s by Geoffrey Goldspink and Shi Yu Yang at University College London as a locally acting IGF-1 splice variant (IGF-1Ec) whose C-terminal E-peptide is upregulated in skeletal muscle after mechanical loading and is proposed to activate satellite cells. Native MGF has a half-life of only minutes, so a synthetic version was attached to a polyethylene-glycol chain to slow renal clearance and proteolysis, producing PEG-MGF for once-weekly dosing. The pegylated product never advanced through human drug development; it moved instead into the grey research-chemical and bodybuilding supply chain, where it is sold in lyophilized vials labeled for research use only, and it is named alongside its parent MGF on the WADA Prohibited List.
PEG-MGF arose from the practical problem that native MGF, a muscle-derived splice variant of insulin-like growth factor 1, lasts only minutes in circulation. Pegylation, a routine half-life-extending modification, was applied to make a systemically usable version, which entered the gray market alongside MGF itself.
Related MGF evidence
2002 to 2014
The evidence concerns endogenous or non-PEGylated MGF, not direct PEG-MGF administration.
- 2002An early cell study reports myoblast effectsThe experiment compared non-PEGylated MGF-related peptide with mature IGF-I. It did not study PEG-MGF.
- 2003Exercise-associated MGF expression is measured in human muscleResearchers measured the body's own splice-variant expression after resistance exercise. No MGF or PEG-MGF was administered.
- 2014A replication study reports no measurable MGF effectSynthetic MGF did not increase proliferation, change differentiation, or activate the tested signaling response. PEG-MGF was not tested.
Patent filings
- not present in artifactUS10532097B2 names PEG-MGF as one possible PEGylated payload in an anti-PEG-antibody and hydrogel delivery system, without any PEG-MGF preparation or experiment.
The numbers behind the grade
- Type
- Pegylated MGF
- Half-life
- Days (vs minutes)
- Effect
- Satellite-cell activation
- WADA
- Prohibited (S2)
- Approved
- No
- Variability
- High (PEG chemistry)
The people taking it
Users are bodybuilders and people focused on muscle growth, drawn by the muscle-repair story.
The longer-acting, more popular form of MGF in bodybuilding circles, valued for needing less frequent injection, though no better supported by human evidence.
PEG-MGF’s users are bodybuilders and muscle-growth-focused users in the gray-market peptide community, drawn by the muscle-repair narrative.
Used illicitly in bodybuilding for muscle repair and growth, gray-market only, with a longer duration than plain MGF. Banned in sport; not an approved therapy.
Set against the alternatives
PEG-MGF is simply the longer-acting form of MGF, and its closest relatives are the other growth-factor compounds, including the IGF-1 analog covered elsewhere, all of which share the proliferation concern. Against the regenerative peptides it is marketed alongside, such as TB-500 and BPC-157, it is the one most directly tied to the growth-factor cancer question. Its profile is the MGF profile with a longer half-life.
What we do not know
- Whether the sustained, systemic exposure of PEG-MGF is more effective or simply riskier than the natural brief pulse.
- How much batch variability undermines any claimed effect.
- Whether the IGF-1-family cancer concern matters in practice.
Legal status
Not approved for human use in any jurisdiction; sold as a research-use-only chemical and used illicitly in bodybuilding, where its longer half-life makes it the preferred form over plain MGF. Banned in sport at all times.
Status current as of July 2026. Regulatory positions change, sometimes quickly.
The market for this
What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.
Available only as research-use-only material from peptide vendors, not for human use and banned in sport. The high batch variability and absence of human data make it a risky, unsupported choice.
Synthesized and pegylated overseas, mostly in China, and sold as research material with notable batch-to-batch variability; an independent certificate of analysis is the only check, and even it cannot standardize the pegylation chemistry.
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about PEG-MGF.
- Supply chain. We have not mapped where it is made.
- What could change. No forward-looking summary yet.
Sources
MGF is the IGF-1Ec splice variant that activates muscle satellite cells; discovered by Goldspink group
Yang & Goldspink, satellite-cell mechano growth factor research (PubMed)
Human MGF/IGF-1 splice-variant expression rises after resistance exercise (observational human data on endogenous MGF, not injected peptide)
Mechano-growth factor rescues motoneurons and improves muscle function in an ALS mouse model (animal-only evidence)
Riddoch-Contreras et al., Experimental Neurology 2008 (ScienceDirect)
Mechano Growth Factors are named on the WADA Prohibited List under S2.2 growth factors, prohibited at all times
S2 peptide hormones, growth factors and related substances (including growth factors affecting muscle) are prohibited at all times
PEG-MGF is a preclinical research compound with no FDA approval, no human clinical trials, WADA-prohibited, half-life extended from minutes to hours by pegylation, not for human consumption
PEG-MGF is a pegylated variant of the IGF-1Ec MGF splice variant; PEGylation raises half-life from about 5 to 7 minutes to roughly 48 to 72 hours
PEG-MGF marketed as a research chemical (not for human use); FDA status unapproved
PEG-MGF sold as export research peptide 2mg vials without approved human indication
A 2002 cell study from Geoffrey Goldspink's group tested the E domain, the part of MGF that distinguishes it from mature IGF-I, in mouse myoblast cultures. The E domain increased myoblast proliferation while suppressing their differentiation into mature muscle cells, effects that did not occur with mature IGF-I alone. When the researchers blocked the IGF-I receptor with a specific antibody, MGF's effects persisted, indicating that the E domain's function is mediated through a different receptor, though the paper did not identify which one. These findings come from cell culture only, with no human data, animal studies, or quantitative results reported in the abstract.
A direct replication study found no effect of non-PEGylated MGF peptide in mouse or human muscle-cell systems.
A patent names PEG-MGF as a possible therapy but provides no direct PEG-MGF experiment or product formulation.
WO2018130660A1. Reloadable hydrogel system for treating myocardial infarction.
The ALS mouse study did not inject MGF peptide, and it did not use PEG-MGF. The researchers injected a plasmid, a small ring of DNA, into the hind-leg muscles of SOD1G93A mice. The plasmid carried either the MGF gene or, for comparison, the IGF-I gene. The paper describes SOD1G93A mice as a mouse model of ALS. Treatment began at 70 days of age, when symptoms start.
Riddoch-Contreras et al., Experimental Neurology 2008 (ScienceDirect)
On WADA's Prohibited List page as read in this run, mechano growth factors (MGFs) appear in subsection S2.3, Growth Factors and Growth Factor Modulators. They are listed next to IGF-1 and its analogues under the words 'including, but not limited to'. On this page, subsection S2.2 covers peptide hormones such as growth hormone and the factors that release it. The page text read names MGFs as a group and does not name PEG-MGF separately. The page read does not state which year's list it shows.
In a 1999 paper in the Journal of Anatomy, Geoffrey Goldspink described a form of the IGF-1 growth factor that overloaded muscle makes through alternative gene splicing, called mechano growth factor or MGF, which appears designed to act locally on the muscle cell that produces it and nearby cells rather than through the bloodstream. This muscle form contains a 52-base insert in the gene message that shifts the reading frame, altering the tail end of the peptide compared to the liver form of IGF-1; the paper proposes this probably changes how the peptide binds to receptors and binding proteins, likely binding a different binding protein found in muscle tissue spaces, though these are proposals rather than measured binding results. Goldspink placed MGF within a broader observation that several cell types including bone-building cells, fibroblasts, and smooth, heart and skeletal muscle cells respond to mechanical strain, with mounting evidence linking this response to the cytoskeleton and suggesting the connection between mechanical pull and gene activity is a new and important area of study.
Researchers at two pharmaceutical companies tried to repeat earlier reports that the MGF peptide makes muscle stem cells multiply more and delays their fusion into muscle fibres. They tested MGF peptides on lab-grown mouse and human muscle cells, including a mouse muscle cell line called C2C12, primary human skeletal muscle cells and primary muscle stem cells. This was cell work, not a study in animals or people, and the peptide had no PEG attached.
In a 1996 study on rabbit muscle, active stretch induced rapid muscle growth and led to expression of a second IGF-1 isoform (IGF-1Eb) alongside the single form (IGF-1Ea) found in resting muscle. Stretched muscle strongly expressed two types of IGF-1 gene message, with tissue staining indicating that IGF-1 was produced within the muscle fibres themselves.
A 2010 minireview in Endocrinology describes the hypothesis that the IGF-I gene can be spliced to produce mechano-growth factor, a unique peptide with a role in myoblast growth. The review presents research suggesting that one IGF-I splice form, IGF-IEb, rises first after skeletal muscle injury, while another form, IGF-IEa, rises at later time points; these are measurements of gene messages in injured muscle, not results from administering a peptide.
In a sheep study with induced heart attacks, the MGF E domain peptide improved heart function in a first experiment and preserved it in a second experiment, where treated animals had 35% less damaged heart muscle than controls after eight days. Heart function was assessed by ultrasound and heart tissue was examined for markers of cell survival and cell death. These are animal results with no direct implications for humans.
Mechano-growth factor reduces loss of cardiac function in acute myocardial infarction - PubMed
A 2012 laboratory study tested mechano growth factor (MGF) on pig satellite cells grown in dishes and found that MGF strongly stimulated the cells to multiply while inhibiting their maturation into muscle cells by quickly lowering the activity of myogenic determination factors, the genetic switches that push satellite cells toward becoming muscle. The study did not report the MGF concentration used or how the peptide was made, and no human data were provided.
A cell study from the Institute of Myology in Paris, with Geoffrey Goldspink among the authors, grew muscle cells taken from healthy people of different ages, from newborns to older adults. The researchers treated the cells with a 24-amino-acid MGF E peptide, called MGF-24aa-E. The abstract does not say how many donors were used. This was lab cell work, and the peptide had no PEG attached.
A 2016 laboratory study comparing full-length MGF protein with human IGF-I on the human IGF-I receptor found that at high equal concentrations, full-length MGF reached a maximum activation effect similar to IGF-I (89-fold compared with 77-fold), though it required a higher concentration to reach half its maximum effect (7.83 nanomoles per litre compared with 0.86 for IGF-I). In the same study, the short human MGF peptide and its stabilised version called Goldspink-MGF produced no activation of the IGF-I receptor. The authors state that more research is needed to understand what full-length MGF does in the living body and whether these test-tube findings matter.
A 2012 study by Esposito, Deventer and Van Eenoo analysed two black market preparations containing an unknown MGF analogue using liquid chromatography and mass spectrometry. Both products were identified as MGF analogues with a chemically amidated tail end, neither as a PEG-MGF conjugate, so the result does not show what products labelled PEG-MGF contain. Although WADA had banned MGF, no routine detection method had been reported; the authors identified a potentially diagnostic mass spectrometry signal (m/z 717.8 to 431.1 transition) for the amidated analogue they found.
A 2012 article asks whether mechano growth factor is a real part of the body's tissue repair system or a loose part that does little.
Mechano-Growth Factor: an important cog or a loose screw in the repair machinery? - PMC
A 2014 paper by Thevis, Thomas, Geyer and Schänzer at the German Sport University Cologne used mass spectrometry to characterise a biotechnologically produced, full-length MGF protein, for use in doping controls. The material was a modified full-length MGF protein, not the short PEGylated peptide sold as PEG-MGF, and the paper does not measure PEG-MGF detection, effects or clearance from the body.
A 2017 study identified a variant of MGF called MGF R23H in confiscated vials alongside the peptide BPC 157; however, this finding does not show what products labelled PEG-MGF contain, as MGF R23H is a different analogue. Test-tube experiments in blood plasma showed that MGF R23H had good stability and should be detectable in urine, though this was a laboratory experiment on a different analogue, not a measured half-life in people or a result for PEG-MGF.
An FDA list of bulk drug substances nominated for use in pharmacy compounding under Section 503A, printed as updated May 14, 2026, states that the nomination for PEG-MGF was withdrawn and that PEG-MGF was removed from category 2 of FDA's interim compounding policy. A search listing described this same address as a September 2024 update that placed PEG-MGF in category 2, so the listing and the opened document disagree. The document records a nomination status and does not approve PEG-MGF for any use.
FDA has not identified human exposure data for drug products containing PEG-MGF, according to its page on bulk drug substances that may present significant safety risks in pharmacy compounding. The agency raised concerns in its review about possible immunogenicity and characterization challenges for this substance, though the page does not report that these harms occurred in people.
FDA, Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks
An FDA Pharmacy Compounding Advisory Committee page announces a planned committee discussion of PEG-MGF before the end of February 2027. The page is an announcement of a future discussion, not an advisory recommendation and not an FDA decision.
Meeting of the Pharmacy Compounding Advisory Committee. U.S. Food and Drug Administration.
A 2026 narrative review in Frontiers in Endocrinology examined pegylated mechano growth factor (PEG-MGF) among IGF-1 analogues used off-label, comparing clinical evidence with self-administration protocols from grey literature to help clinicians counsel patients. However, the review reports no peer-reviewed human studies of PEG-MGF and no measured half-life for it, and the proposed receptor pathway for PEG-MGF does not derive from experiments using PEG-MGF itself.
A US patent, US10532097B2, names PEG-MGF as one possible PEGylated medicine that its multi-drug delivery system could carry.
The studies that matter
Pegylation pharmacology2000s-2010s
Attaching PEG to MGF increased its size and half-life, reducing kidney clearance and sustaining activity over days rather than minutes.
Animal hypertrophy studies2010s
PEG-MGF produced measurable muscle hypertrophy after intramuscular injection in mice, with effects lasting days.
Human efficacy trialsnone
As with MGF, no completed human efficacy trials of PEG-MGF exist.