A research-tier construct: the 24-aa MGF E-peptide of IGF-1Ec conjugated to polyethylene glycol. Zero PubMed papers on PEG-MGF as a discrete entity. Inherits the contested Goldspink / Fornaro reproducibility debate and adds an unmeasured PEGylation layer on top.
PEG-MGF is a research-chemical construct: the synthetic 24-amino-acid C-terminal E-peptide of human IGF-1Ec (an alternative-splice product of the IGF-I gene), conjugated to a polyethylene glycol (PEG) moiety. The molecule isn't endogenous and has never appeared in any human or animal tissue — pegylation is a synthetic post-translational modification, and "PEG-MGF" exists only because someone made it.
Three identity layers are easy to confuse and worth keeping separate. First, endogenous IGF-1Ec mRNA and pre-pro-IGF-1Ec protein — an alternative splice variant of the IGF1 gene, transcribed by mechanically loaded skeletal muscle. Cloned from rabbit muscle by the Goldspink group (Yang 1996, PMID 8884603). Translated as a 113-aa pre-pro-IGF-1Ec, then post-translationally cleaved into mature native IGF-1 plus the unique E-peptide tail. Second, the cleaved 24-aa E-peptide — hypothesized by the Goldspink group to act on satellite cells via a non-IGF-1R receptor. The proposed "MGF receptor" has never been cloned, named, or characterized in any peer-reviewed paper; it's an inferred entity, not a defined molecular target. Third, synthetic PEG-MGF (the research chemical) — the 24-aa E-peptide solid-phase-synthesized, then conjugated to PEG. Legitimate research suppliers (Bachem, Tocris) document PEG molecular weight, attachment chemistry, and stoichiometry per-batch; black-market PEG-MGF doesn't, and Esposito 2012 (PMID 22328223) characterized vendor analogs with undisclosed D-Arg, His-substitution, amidation, and variable PEG attachment.
PEG-MGF inherits all the mechanistic claims of the underlying 24-aa MGF E-peptide. There's no additional PEG-MGF-specific mechanism — the PEG is held to be pharmacologically inert, only extending the kinetic window.
The Goldspink-group narrative goes like this: mechanical loading or muscle damage drives IGF-1 pre-mRNA to splice toward the Ec (MGF) isoform for ~24 hr (Hill 2003 PMID 12692175 in rodents; Hameed 2003 PMID 12562960 in humans, with upregulation in young but not old men). The pre-pro-IGF-1Ec is then cleaved into mature IGF-1 plus the 24-aa Ec E-peptide. The E-peptide is hypothesized to act independently of IGF-1R — Dłużniewska 2005 (PMID 16144956) reported neuroprotection that persisted under IGF-1R blockade, motivating the proposal of a distinct receptor that's never been cloned. Downstream, the E-peptide is said to activate quiescent satellite cells, driving proliferation and delaying terminal differentiation (Mills 2007 PMIDs 17156777, 17845560; Ates 2007 PMID 17531227; Kandalla 2011 PMID 21354439). Splicing then reverts toward Ea, supporting differentiation and fusion.
Fornaro et al. 2014 (PMID 24253050) is a joint Novartis + GSK study using the same MGF-Ct24E peptide as the Goldspink-group studies. Tested on C2C12, primary human myoblasts, and primary mouse muscle stem cells, up to 500 ng/mL. They found no proliferative or anti-differentiation effect. The full-length IGF-I positive control worked as expected. The accompanying Mol Endocrinol editorial — Rotwein 2014 (PMID 24460193), titled "The fall of mechanogrowth factor?" — framed it as a serious challenge to the canonical narrative.
The Fornaro paper hasn't been refuted by an equally rigorous follow-up. Honest position: the proliferative E-peptide effect is contested. PEG-MGF is the proposed long-acting clinical version of a molecule whose underlying bioactivity hasn't been independently reproduced at industrial-lab rigor.
What PEG conjugation adds is generic class theory, per Veronese & Mero 2008 (PMID 18778113, the canonical PEG-biologics review): increased hydrodynamic radius, reduced renal filtration, longer plasma half-life, shielded backbone, lower immunogenicity for foreign-sequence biologics (weaker for endogenous-sequence peptides like the human MGF E-peptide), and potential for accelerated clearance via anti-PEG antibodies on chronic dosing. None of these effects has been measured for PEG-MGF specifically.
The two names sit on top of three actually-different molecules. Don't conflate them.
| Name | Molecule | Half-life claim | Anchored? |
|---|---|---|---|
| Endogenous MGF / IGF-1Ec mRNA | Spliced IGF-1 mRNA + cleaved E-peptide in muscle | ~1 day mRNA pulse post-injury | Yes (mRNA only) |
| Synthetic non-PEG MGF | 24-aa E-peptide | Vendor-cited "5–7 min" | No |
| Synthetic PEG-MGF | 24-aa E-peptide + PEG (5–40 kDa) | Vendor-cited "48–72 hr" | No (T2 class rationale only) |
Two facts worth keeping in view: every Goldspink-group preclinical positive finding used non-PEG synthetic 24-aa E-peptide — no published preclinical study has compared PEG-MGF to non-PEG MGF head-to-head. And the Fornaro 2014 reproducibility failure was on the non-PEG E-peptide. By the Goldspink logic that PEG is pharmacologically inert, PEG-MGF would behave like non-PEG MGF for longer — meaning PEG-MGF inherits the reproducibility problem without independent positive evidence to offset it.
Two more identity confusions to defuse: PEG-MGF is not PEG-IGF-1. PEG-IGF-1 (Kletzl 2017, Braun 2018) is full-length recombinant 70-aa human IGF-I with PEG; PEG-MGF is the 24-aa C-terminal E-peptide with PEG. Their proposed pharmacologies are mechanistically distinct (IGF-1R agonism vs hypothesized non-IGF-1R "MGF receptor"). And PEG-MGF is not IGF-1 LR3. LR3 is full-length IGF-1 with N-terminal extension and Arg³ substitution — not pegylated, not the E-peptide. Some bodybuilding-community summaries blur PEG-MGF and LR3 as "long-acting IGF family" — they aren't interchangeable.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeNo published trial of PEG-MGF for any indication. No PK study, no safety study, no efficacy study. The dosing below is vendor and community convention.
| Parameter | Common Range |
|---|---|
| Dose per injection | 200–400 µg |
| Frequency | 1–2× per week (the long-half-life rationale) |
| Timing | Post-workout (community) |
| Cycle length | 4–8 weeks on / similar off |
| Route | SC standard; the longer half-life makes the post-workout ultra-local IM rationale of non-PEG MGF largely irrelevant |
The 200–400 µg range and twice-weekly cadence both come from vendor / community sources, not from a Phase 1 dose-finding study. The numbers aren't anchored.
For a 2 mg vial in 2 mL bacteriostatic water: 1 mg/mL (1000 µg/mL), so 1 unit on a U-100 syringe = 10 µg. A 200 µg dose is 20 units; a 400 µg dose is 40 units.
Lyophilized vials are stable at room temperature short-term; refrigerate for longer. Reconstituted vials should be refrigerated and used within 28 days. PEG conjugation generally improves stability vs unmodified peptide (Veronese 2008), but PEG-MGF-specific stability data isn't published.
For the full reconstitution protocol, see the Bacteriostatic Water guide.
Pre-filled with a typical PEG-MGF setup. Edit any field — the draw updates live.
Insulin syringe — 100 units = 1 mL
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No published safety data on PEG-MGF. No FAERS, EudraVigilance, or Yellow Card entries because the molecule has never been approved.
Class concerns worth noting:
Community user reports describe mild injection-site irritation as the most common acute issue. None of this is anchored in a peer-reviewed safety paper.
PEG-MGF's evidence base is unusually thin even by gray-market peptide standards. Three things to know before committing time or money.
One: zero PubMed-indexed primary studies on PEG-MGF. Verified 2026-05-07 — PubMed search for "PEG-MGF" returns 0 hits. Search for "pegylated mechano growth factor" returns 4 hits, all about PEG-IGF-1 or PEG-rhGH (different molecules entirely). The 48–72 hour half-life claim, the satellite-cell mechanism claim, the dosing convention — none of it is anchored to PEG-MGF-specific peer-reviewed data.
Two: the underlying non-PEG MGF E-peptide bioactivity is contested. Goldspink-group positive findings (Mills 2007 PMIDs 17156777 / 17845560; Ates 2007 PMID 17531227; Kandalla 2011 PMID 21354439; Carpenter 2008 PMID 17581790) all predate the Fornaro 2014 reproducibility failure (PMID 24253050) by Novartis + GSK. The Fornaro paper hasn't been refuted by an equally rigorous follow-up.
Three: the pharma industry pursued PEG-IGF-1 but didn't pursue PEG-MGF. Roche / Genentech and others took PEG-IGF-1 into Phase 1 (Kletzl 2017, PMID 28110155). No equivalent program exists for PEG-MGF, even though the underlying MGF concept has been around since 1996. The lack of pharma uptake is a real signal about how the proposition looks to internal scientific review.
If you decide to use PEG-MGF anyway, do so with eyes open about what the literature actually supports and what it doesn't.
MGF (non-PEG) — same 24-aa E-peptide, no PEG. Vendor-claimed 5–7 min half-life vs PEG-MGF's claimed 48–72 hr. Both half-life figures are unanchored.
IGF-1 LR3 — full-length 70-aa IGF-I with N-terminal extension and Arg³ substitution. Not pegylated, not the E-peptide. Different mechanism.
IGF-1 DES — full-length 67-aa IGF-I missing N-terminal Gly-Pro-Glu. Not pegylated, not the E-peptide. Different mechanism.
PEG-IGF-1 (Roche / Genentech pharma program) — full-length recombinant human IGF-I PEGylated. Real pharmaceutical development category. Not what you buy as "PEG-MGF" from a research-chemical vendor.
Mecasermin (Increlex) — FDA-approved recombinant native IGF-I for severe primary IGF-I deficiency. Not MGF, not pegylated. Increlex's existence does not give regulatory cover to PEG-MGF.
HGH / Somatropin — recombinant human growth hormone, full 191-aa protein. Different molecule, different receptor, different regulation.
PEG-MGF is a research peptide not approved by the FDA for human use. It is sold only as a research chemical, and StackTrax does not endorse or facilitate personal use.
Quality varies enormously among research-chemical suppliers. At minimum, look for:
StackTrax’s preferred partner NextGen Peptides does not currently carry PEG-MGFin their catalog, which is why you don’t see a direct purchase link here. Other major research-chemical suppliers carry it; we don’t specifically recommend one for this compound.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeNo. PEG-MGF has never been FDA, EMA, or any other regulatory authority approved. It is a PEGylated version of the synthetic MGF E-peptide, designed for longer systemic exposure than unmodified MGF. The PEG-MGF-specific Tier-2 (peer-reviewed) evidence record is essentially empty — every PEG-MGF-specific pharmacological claim is vendor extrapolation from the contested MGF E-peptide literature plus the general PEGylation class rationale.
Community-practice dosing is 200–400 mcg subcutaneously, 1–2 times per week. The "48–72 hour half-life" widely cited for PEG-MGF is also vendor/community-tier — no peer-reviewed human PK study of PEG-MGF specifically exists. The biochemical rationale (PEGylation extends plasma half-life of peptides 10–100×) is class-valid; the specific 48–72 hour number for PEG-MGF is not.
PEG-MGF requires 0.6% acetic acid (NOT bacteriostatic water). BAC water degrades the peptide. A typical reconstitution is 2 mg of PEG-MGF + 2 mL of 0.6% acetic acid, yielding 1 mg/mL (1000 mcg/mL). A 200 mcg dose draws to 0.20 mL (20 units on a 100-unit insulin syringe), 400 mcg = 0.40 mL (40 units).
MGF (the unmodified synthetic 24-amino-acid E-peptide) is the post-workout-IM-into-trained-muscle option — community framing is "high local exposure with rapid systemic clearance." PEG-MGF adds polyethylene glycol modification claimed to extend half-life for systemic 1–2× weekly subcutaneous dosing. Neither has peer-reviewed human PK or efficacy data. PEG-MGF is the more vendor-tier-claim-dependent of the two — even the underlying mechanism (E-peptide receptor, satellite-cell activation) is contested in the peer-reviewed literature.
The endogenous IGF-1Ec splice variant exists and is upregulated by mechanical loading in animal muscle. Whether the synthetic 24-aa E-peptide reproduces that biology has been disputed (Fornaro et al. 2014 contested the reproducibility of earlier Goldspink-group findings). Whether PEGylation preserves whatever bioactivity the synthetic E-peptide has is even less established. No human RCT exists.
Yes. WADA explicitly names "mechano growth factors (MGFs)" in S2.3 (Growth Factors and Growth Factor Modulators) — the PEG conjugation does not exempt it. Prohibited at all times. No therapeutic-use exemption available.
Disclaimer: This guide is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. The compounds discussed are not FDA approved for human use. Always consult a qualified healthcare provider before starting any new supplement or peptide protocol. StackTrax does not sell peptides or supplements directly — purchase links go to third-party vendors. StackTrax is not responsible for the products, quality, or business practices of any third-party vendor. This page contains affiliate links — StackTrax may earn a commission on purchases at no extra cost to you.
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StackTrax guides cover peptides and compounds that are not FDA-approved for the uses discussed. The dosing, reconstitution, and safety information is compiled from published research and community protocols for educational purposes only.
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