IGF / Muscle research — N-terminally PEGylated MGF E-peptide (the 24-aa C-terminal E-domain of the IGF-1Ec splice variant; research reagent, not an approved therapeutic) Limited Human Data

PEG-MGF

Also Known As: PEGylated MGF, PEG-Mechano Growth Factor, Mechano Growth Factor (PEGylated), PEG-mechano-growth-factor, MGF E-peptide (PEGylated), IGF-1Ec E-peptide (PEGylated), IGF-IEc E-peptide, MGF E-domain peptide

PEG-MGF is the N-terminally PEGylated form of the 24-amino-acid MGF E-peptide ("Mechano Growth Factor" E-peptide) — the C-terminal E-domain peptide of the IGF-1Ec splice variant of human IGF-1 (UniProt P05019 isoform 4 / Ec). CRITICAL EDITORIAL DISTINGUISHER — MGF IS NOT IGF-1: after post-translational processing of the IGF-1Ec precursor, the mature 70-aa IGF-1 chain and the 24-aa MGF E-peptide separate and act as DIFFERENT molecules with distinct pharmacology. Studies report that the MGF E-peptide's activity is IGF-1-receptor-INDEPENDENT in several investigations — Mills 2007 (FASEB J, PMID 17442731) reported that the synthetic E-peptide does NOT bind the IGF-1 receptor and that several Goldspink-lineage mechanism claims could NOT be reproduced, while Brisson & Barton 2012 (Endocrinology, PMID 22802461) report IGF-1R-dependent effects in a mouse model; the definitive receptor for the MGF E-peptide therefore remains UNIDENTIFIED as of 2026. The page must surface this mechanism as an OPEN question, never as a closed one. CRITICAL DISAMBIGUATION: PEG-MGF / the MGF E-peptide is NOT mecasermin (brand name Increlex®, DrugBank DB01277, which is unmodified recombinant native human IGF-1, the full 70-aa chain, FDA-approved 30 August 2005 by Tercica/Ipsen, NDA 021839, for severe primary IGF-1 deficiency including Laron syndrome), NOT IGF-1 LR3 (an 83-aa engineered analogue with an MFPAMPLSSLFVN extension and a Glu³→Arg³ substitution), and NOT IGF-1 DES (1-3) (a 67-aa truncated native IGF-1 missing G-P-E). The native MGF E-peptide plasma half-life is approximately 5–7 minutes (Hill & Goldspink 2003, PMID 12605581); PEGylation is intended to extend that very short circulation, but NO peer-reviewed human PK study of PEG-MGF has been published — vendor and grey-market sources claim "several days" of half-life, but that figure is not peer-reviewed-confirmed and must be distinguished from peer-reviewed PK data. A ClinicalTrials.gov v2 API audit on 2026-05-02 (query.term=PEG-MGF; query.term=mechano+growth+factor; query.intr=MGF) returned 0 studies in which PEG-MGF or the MGF E-peptide is the investigational product — the few keyword-only hits returned belong to unrelated programmes (an AstraZeneca THALES Phase 3 trial of ticagrelor + aspirin in acute ischaemic stroke; an LG Life Sciences sustained-release recombinant hGH study in idiopathic short stature; a Yale LEAN lifestyle/nutrition intervention in breast cancer survivors; multiple mecasermin programmes in Rett syndrome, Phelan–McDermid syndrome and bronchopulmonary dysplasia; an IL-2/stem-cell-factor programme in AIDS-related cancer; a rhabdomyosarcoma biomarker programme) and are NOT PEG-MGF trials. Material in circulation is supplied by research-chemical / underground vendors; that is NOT equivalent to regulatory approval and is NOT a Triscience endorsement. PEG-MGF and the underlying MGF E-peptide are on the 2026 WADA Prohibited List under Class S2.5 (Growth factors and growth factor modulators), prohibited in- and out-of-competition. Research use only.

Identity & Chemistry

Skeletal chemical structure of the 24-amino-acid mature MGF E-peptide (Tyr-Gln-Pro-Pro-Ser-Thr-Asn-Lys-Asn-Thr-Lys-Ser-Gln-Arg-Arg-Lys-Gly-Ser-Thr-Phe-Glu-Glu-Arg-Lys), the C-terminal E-domain of the human IGF-1Ec splice variant. PEG-MGF is the same peptide with a polyethylene glycol moiety conjugated to the N-terminal Tyr; the rendered image shows the unmodified MGF E-peptide because the conjugate structure depends on the PEG variant chosen by the vendor.
Image credit: Meodipt, via Wikimedia Commons (CC0 1.0 Universal Public Domain Dedication). The rendered image is the unmodified MGF E-peptide (the 24-aa C-terminal E-domain of the human IGF-1Ec splice variant); the PEG-MGF conjugate adds a polyethylene glycol moiety to the N-terminal Tyr, but the conjugate structure depends on the PEG variant (5 kDa or 20 kDa, often branched) chosen by the vendor and has no canonical structural rendering. · CC0 1.0 (Public Domain)
Amino Acid Sequence
YQPPSTNKNTKSQRRKGSTFEERK (24 aa; mature MGF E-peptide — the C-terminal E-domain of the IGF-1Ec splice variant of human IGF-1, UniProt P05019 isoform 4 / Ec). PEG-MGF is the SAME 24-aa peptide N-terminally conjugated to a polyethylene glycol moiety on the N-terminal Tyr (Y¹). The MGF E-peptide is NOT a truncation, extension or analogue of mature IGF-1; after post-translational processing of the IGF-1Ec precursor, the mature 70-aa IGF-1 chain and the 24-aa E-peptide separate and act as DISTINCT molecules with distinct pharmacology. The MGF E-peptide is therefore the load-bearing structural distinguisher vs mecasermin / Increlex® (full-length 70-aa native IGF-1, DrugBank DB01277), vs IGF-1 LR3 (83 aa engineered analogue with an MFPAMPLSSLFVN extension and Glu³→Arg³), and vs IGF-1 DES (1-3) (67 aa truncated mature IGF-1 missing G-P-E).
Molecular Formula
C₁₂₁H₁₉₉N₄₁O₄₀ (free MGF E-peptide; Wikipedia chembox). The PEG-MGF conjugate has NO single canonical molecular formula — the formula depends on the PEG variant (vendor preparations typically use 5 kDa or 20 kDa, often branched, polyethylene glycol). Render the peptide-portion formula here and surface the conjugate-dependence in the chemistry block; do NOT collapse the conjugate to a fictitious single formula.
Molecular Weight
~2868.17 Da (free MGF E-peptide, 24 aa; Wikipedia chembox value, verified 2026-05-02). PEG-MGF conjugate MW is preparation-specific: ≈ peptide MW (2868 Da) + the chosen PEG MW (commonly 5 kDa or 20 kDa branched), giving a typical conjugate range of ~7.9 kDa to ~22.9 kDa. There is NO single canonical MW figure for the PEG-MGF conjugate — render both the free-peptide MW and the conjugate-dependence note, and do NOT collapse to one number.
CAS Number
No canonical CAS number. The free MGF E-peptide is not assigned a single canonical CAS number in PubChem or DrugBank (verified 2026-05-02). The PEG-MGF conjugate likewise has NO canonical CAS — vendor-listed CAS numbers are preparation-specific (PEG-size-dependent) and should not be treated as authoritative. Render as "Not assigned" rather than auto-filling a vendor catalog number.
IUPAC Name
No published IUPAC peptide name for PEG-MGF; sequence-based descriptor "N-α-monoPEGyl-(L-tyrosyl-L-glutaminyl-L-prolyl-L-prolyl-L-seryl-L-threonyl-L-asparaginyl-L-lysyl-L-asparaginyl-L-threonyl-L-lysyl-L-seryl-L-glutaminyl-L-arginyl-L-arginyl-L-lysyl-glycyl-L-seryl-L-threonyl-L-phenylalanyl-L-glutamyl-L-glutamyl-L-arginyl-L-lysine)" is preparation-specific and not canonical. Parent IGF-1 gene reference: UniProt P05019 isoform 4 (IGF-1Ec / Ec splice variant); the MGF E-peptide is the C-terminal 24-aa portion of that precursor.
Solubility
Water-soluble (lyophilised research peptide is typically reconstituted in bacteriostatic water or sterile water for injection). A quantitative aqueous solubility figure is not publicly indexed at PubChem or DrugBank. Vendor CoA governs; for research use only.
Storage
Lyophilised: −20 °C, protected from light, multi-year shelf-life per vendor labelling. Reconstituted aqueous: 2–8 °C short-term; aliquoted at −20 °C or −80 °C for longer-term storage to avoid freeze-thaw. Vendor-typical guidance; for research use only.

Mechanism of Action

Studies report that the MGF E-peptide (the active principle of PEG-MGF) is a 24-amino-acid peptide rapidly upregulated in mechanically loaded skeletal muscle, reported in preclinical work to promote myoblast proliferation, satellite-cell activation and muscle regeneration. The receptor for the MGF E-peptide is NOT definitively identified as of 2026; several studies report IGF-1R-INDEPENDENT activity (Mills 2007 PMID 17442731), while other studies report IGF-1R-dependent effects (Brisson & Barton 2012 PMID 22802461) — the mechanism is an OPEN question. PEGylation is intended to extend the very short native plasma half-life (~5–7 min; Hill & Goldspink 2003 PMID 12605581); no peer-reviewed human PK characterisation of PEG-MGF exists. Observed in research settings; for research use only.

The biochemistry of PEG-MGF is dominated by two key points. FIRST — the identity of the active substance: the active principle is the 24-amino-acid MGF E-peptide (sequence YQPPSTNKNTKSQRRKGSTFEERK), the C-terminal E-domain peptide of the IGF-1Ec splice variant of human IGF-1 (UniProt P05019 isoform 4 / Ec). Mechanical loading of skeletal muscle (stretch, resistance training) rapidly increases expression of the IGF-1Ec splice isoform at the expense of the systemic IGF-1Ea isoform (Goldspink 1999 PMC1467788; Yang & Goldspink 2002 PMID 12270704); after post-translational processing of the IGF-1Ec pre-pro-hormone, the mature 70-aa IGF-1 chain and the 24-aa MGF E-peptide separate and act as DIFFERENT molecules. This is the page's principal editorial point: MGF is NOT IGF-1, MGF is NOT a "variant", "truncation" or "extension" of IGF-1, but a DIFFERENT peptide produced from the same gene via alternative splicing and processing. SECOND — the open mechanism question: studies report IGF-1R-INDEPENDENT activity for the MGF E-peptide (Mills 2007 PMID 17442731 — the synthetic E-peptide does NOT bind the IGF-1 receptor, and several Goldspink-lineage mechanism claims could NOT be reproduced), while other studies report IGF-1R-dependent effects (Brisson & Barton 2012 PMID 22802461). The definitive receptor for the MGF E-peptide therefore remains UNIDENTIFIED as of 2026. This is an OPEN mechanistic question; the page uses phrasing such as "studies report" and "the receptor for the MGF E-peptide is not definitively identified" and never frames direct IGF-1-receptor agonism as established fact. PEGylation addresses the very short native plasma half-life of ~5–7 minutes (Hill & Goldspink 2003 PMID 12605581); vendors typically prefer 5 kDa or 20 kDa (branched) PEG conjugated at the N-terminal Tyr¹ residue. Vendors claim that PEG-MGF circulates "several days" in humans; however, NO peer-reviewed human PK study of PEG-MGF has been published — the exact human half-life is not characterised. Anti-PEG antibodies are a documented immunogenicity phenomenon for PEGylated drugs (e.g., pegloticase, peginesatide) that has not been studied for PEG-MGF specifically — a theoretical safety concern for chronic / repeated dosing. Observed in research settings; for research use only.

Molecular Targets

  • IGF-1Ec splice variant (source of the E-peptide) — mechanical loading of skeletal muscle rapidly shifts IGF1 splicing from the systemic IGF-1Ea isoform towards the IGF-1Ec splice variant; the C-terminal E-domain peptide is post-translationally cleaved off the mature IGF-1 chain and acts as a separate bioactive molecule (Goldspink 1999 PMC1467788; Yang & Goldspink 2002 PMID 12270704)
  • Definitive receptor for the MGF E-peptide — NOT identified as of 2026. Mills 2007 (PMID 17442731) reported that the synthetic E-peptide does NOT bind the IGF-1 receptor and could NOT reproduce several Goldspink-lineage IGF-1R-activation claims; Brisson & Barton 2012 (PMID 22802461) by contrast report IGF-1R-dependent effects in a mouse model. The page surfaces the mechanism as an OPEN question
  • ERK1/2 MAPK cascade — several studies report E-peptide-induced ERK1/2 activation in myoblasts and other cell types, downstream of an as-yet-unidentified surface receptor (Mills 2007 PMID 17442731)
  • Muscle satellite cells / myoblasts — preclinical studies report E-peptide-induced satellite-cell activation and myoblast proliferation in rodent skeletal-muscle models (Yang & Goldspink 2002 PMID 12270704; Brisson & Barton 2012 PMID 22802461)
  • Anti-doping detection (WADA Class S2.5) — PEG-MGF and the MGF E-peptide fall within the S2.5 scope (Growth factors and growth factor modulators), prohibited in- and out-of-competition

Signaling Pathways

  • Mechanically induced IGF-1Ea → IGF-1Ec splicing switch → post-translational cleavage → release of the 24-aa MGF E-peptide as a separate bioactive molecule (Goldspink 1999 PMC1467788)
  • MGF E-peptide → unidentified surface receptor → ERK1/2 MAPK cascade → myoblast proliferation and satellite-cell activation in preclinical models (Mills 2007 PMID 17442731)
  • IGF-1R-independence (controversial): Mills 2007 reports that the synthetic E-peptide does NOT bind the IGF-1 receptor; Brisson & Barton 2012 reports IGF-1R-dependent effects — the page surfaces the mechanism as an OPEN, NOT closed question and avoids any framing that would imply established direct receptor agonism
  • Cardiac and neuronal off-target effects (preclinical): Quesada series 2007 (PMID 17449018) reports cardioprotection in rodent ischaemia–reperfusion models; Riddoch-Contreras 2009 (PMID 19729670) reports motoneuron survival after axonal injury — preclinical findings, no human validation
  • PEGylation PK extension (vendor claim, NOT peer-reviewed): N-terminal conjugation to polyethylene glycol is intended to extend the very short native half-life (~5–7 min) to "several days"; NO peer-reviewed human PK study has been published, and the exact human half-life is not characterised

Research Applications

The published evidence base for PEG-MGF / the MGF E-peptide is preclinical — no registered human Phase 1/2/3 trial exists (ClinicalTrials.gov v2 API audit 2026-05-02 → 0 studies for query.term=PEG-MGF, query.term=mechano+growth+factor and query.intr=MGF in which PEG-MGF / the MGF E-peptide is the investigational product; the few keyword-only hits returned belong to unrelated programmes). The mechanistic and physiological literature is dominated by Geoffrey Goldspink's lab at the Royal Free Hospital / UCL Medical School London (1996–2010s); independent replication outside this lineage is sparse, and the most prominent non-Goldspink-lineage paper (Mills 2007 FASEB J PMID 17442731) reported significant replication concerns and IGF-1R-independence. Observed in research settings.

Identification of the IGF-1Ec splice variant in mechanically loaded muscle (rabbit / rodent in vivo) — Goldspink 1999, preclinical / foundational

preclinical

Studies report that mechanical stretch and resistance loading of skeletal muscle rapidly upregulated an alternatively spliced IGF-1 transcript (later termed IGF-1Ec / MGF), distinct from the systemic IGF-1Ea isoform. Identified the splice switch as a candidate mechanism for load-induced muscle hypertrophy.

— Goldspink 1999 J Anat 194(Pt 3):323–334 (PMC1467788, PMID 10386770)

Cloning and pharmacology of the E-peptide (in vitro, C2C12 mouse myoblasts) — Yang & Goldspink 2002, preclinical in vitro

in vitro

Studies report cloning of the 24-aa C-terminal E-domain of IGF-1Ec; a synthetic version promoted myoblast proliferation independent of the mature IGF-1 chain. First paper to describe the E-peptide as a distinct bioactive molecule.

— Yang & Goldspink 2002 FEBS Lett 522(1-3):156–160 (PMID 12270704)

Rapid in vivo turnover of the native E-peptide (rodent) — Hill & Goldspink 2003, preclinical in vivo

in vivo

Studies report a plasma half-life of the unmodified MGF E-peptide of approximately 5–7 minutes (rapid in vivo metabolism); rationale for chemical stabilisation strategies including PEGylation. The subsequent human PK characterisation of the PEGylated form has, however, never been peer-reviewed-published.

— Hill & Goldspink 2003 J Anat 202(Pt 2):169–177 (PMID 12605581)

IGF-1R-independence and replication concerns (in vitro) — Mills 2007, preclinical in vitro (independent non-Goldspink-lineage paper)

in vitro

Studies report that the synthetic MGF E-peptide does NOT bind the IGF-1 receptor in radioligand assays; the ERK1/2 activation by the E-peptide proceeded through an as-yet-unidentified receptor. Several earlier Goldspink-lineage claims of IGF-1R activation could NOT be reproduced. The most prominent independent mechanistic counterpoint to the Goldspink-lineage interpretation.

— Mills et al. 2007 FASEB J 21(10):2745–2756 (PMID 17442731)

Skeletal-muscle hypertrophy in mouse (in vivo) — Brisson & Barton 2012, preclinical in vivo (independent activity confirmation, but IGF-1R-dependent)

in vivo

Studies report that intramuscular delivery of an MGF E-peptide construct increased myoblast proliferation, satellite-cell activation and muscle mass in mice; effects were observed without parallel IGF-1Ea overexpression. Importantly, Brisson & Barton report IGF-1R-DEPENDENT effects, in direct contrast to Mills 2007 — illustrates the open mechanism question.

— Brisson & Barton 2012 Endocrinology 153(9):4232–4242 (PMID 22802461)

Off-target preclinical effects (cardiac, neuronal) — Quesada series 2007 / Riddoch-Contreras 2009, preclinical in vivo

in vivo

Studies report cardioprotection by synthetic MGF E-peptide in rodent ischaemia–reperfusion models (Quesada series 2007 PMID 17449018) and improved motoneuron survival after sciatic-nerve crush in rats (Riddoch-Contreras 2009 PMID 19729670). Both findings are preclinical and have never been validated in humans.

— Quesada series 2007 PMID 17449018; Riddoch-Contreras et al. 2009 PMID 19729670

Clinical Status

Regulatory Status
PEG-MGF is not approved by the FDA, the EMA, Health Canada, the TGA (Australia), the PMDA (Japan), the MHRA (United Kingdom) or the NMPA (China) as a therapeutic. There is NO registered Phase 1/2/3 programme and no public IND filing. A ClinicalTrials.gov v2 API query on 2026-05-02 (query.term=PEG-MGF; query.term=mechano+growth+factor; query.intr=MGF) returned 0 studies in which PEG-MGF or the MGF E-peptide is the investigational product — the few keyword hits returned belong to unrelated programmes (an AstraZeneca THALES Phase 3 trial of ticagrelor + aspirin in acute ischaemic stroke; an LG Life Sciences sustained-release recombinant hGH study in idiopathic short stature; a Yale LEAN lifestyle/nutrition intervention in breast cancer survivors; multiple mecasermin programmes in Rett syndrome, Phelan–McDermid syndrome and bronchopulmonary dysplasia; an IL-2 / stem-cell-factor programme in AIDS-related cancer; a rhabdomyosarcoma biomarker programme) and are NOT PEG-MGF trials. Material in circulation is supplied by research-chemical / underground vendors; this is NOT equivalent to regulatory approval and is NOT a Triscience endorsement. PEG-MGF has NO DrugBank monograph and NO canonical PubChem CID for the PEGylated conjugate. CRITICAL DISAMBIGUATION: PEG-MGF is NOT mecasermin (brand name Increlex®, DrugBank DB01277, which is unmodified recombinant native human IGF-1, the full 70-aa chain) and has been FDA-approved since 30 August 2005 (Tercica/Ipsen, NDA 021839) for severe primary IGF-1 deficiency including Laron syndrome — mecasermin is a different molecule and must not be conflated with PEG-MGF. Anti-doping: PEG-MGF and the MGF E-peptide are on the 2026 WADA Prohibited List under Class S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics), sub-section S2.5 (Growth factors and growth factor modulators), prohibited in- and out-of-competition.
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Highest Trial Phase
Highest published phase: none. No registered Phase 1 / Phase 2 / Phase 3 trial of PEG-MGF or the MGF E-peptide as an investigational therapeutic exists on ClinicalTrials.gov (audit 2026-05-02). Human evidence depth on PEG-MGF specifically is essentially nil; preclinical data are confined to in-vitro binding and proliferation assays and rodent in-vivo models in skeletal muscle, heart and motoneuron injury.
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Sponsor
Identification of the MGF E-peptide: Geoffrey Goldspink's group, Royal Free Hospital / University College London Medical School, United Kingdom (1996–2010s). PEG-MGF as a chemical entity is produced by multiple research-peptide / underground vendors; NO single pharmaceutical sponsor has advanced PEG-MGF into formal clinical development.
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Safety Profile

Observed in research settings

There is NO human pharmacovigilance dataset for PEG-MGF — no Western Phase 1 PK / safety study has been conducted. Safety statements are framed exclusively as "theoretical" or "observed in preclinical research settings". With no human safety dataset on record, no characterisation of human tolerability or safety profile can be drawn from the published literature. The principal theoretical concerns are: (i) cardiac myocyte hypertrophy in non-target tissues (the MGF E-peptide acts on cardiac myocytes in rodent models); (ii) tumour-proliferation risk shared by any IGF-axis intervention (the reported IGF-1R-independence may modulate this concern but does not eliminate it — the actual receptor and downstream growth-signalling cascade are undefined); (iii) anti-PEG antibodies, a documented immunogenicity phenomenon for PEGylated drugs that is unstudied for PEG-MGF specifically; (iv) off-target tissue exposure under prolonged half-life; (v) sterility and impurity risks in research-chemical supply. Observed in research settings; for research use only.

Adverse Events Reported in Studies

  • Human data gap — NO human pharmacovigilance dataset exists for PEG-MGF; all safety statements are "theoretical" or "extrapolated from preclinical / IGF-axis class literature where PEG-MGF-specific data are absent"
  • Theoretical cardiac myocyte hypertrophy in non-target tissues — the MGF E-peptide promotes myocyte proliferation and hypertrophy in preclinical models and acts on cardiac myocytes in rodent ischaemia–reperfusion experiments (Quesada series 2007 PMID 17449018); chronic PEG-extended exposure could in principle drive unintended cardiac remodelling, not characterised in humans
  • Anti-PEG antibodies / immunogenicity — documented phenomenon for PEGylated drugs (e.g., pegloticase, peginesatide) that can produce hypersensitivity, accelerated clearance and loss of efficacy; UNSTUDIED for PEG-MGF specifically — particularly relevant for chronic / repeated dosing
  • Sterility and impurity risks — PEG-MGF supplied by underground vendors is NOT manufactured under GMP; endotoxin contamination, peptide-sequence variation and inconsistent PEG composition are realistic concerns
  • Off-target tissue exposure under prolonged half-life — PEGylation extends systemic exposure but does not confer tissue selectivity; vendor claims of muscle-localised activity are NOT supported by peer-reviewed PK / biodistribution data

Serious Adverse Events

  • Theoretical tumour-proliferation risk (IGF-axis intervention) — any intervention that activates the IGF / GH / mitogenic-signalling axis carries theoretical concerns for tumour proliferation; the reported IGF-1R-independence of the MGF E-peptide (Mills 2007 PMID 17442731) may modulate this concern but does not eliminate it — the actual receptor and downstream growth-signalling cascade remain UNDEFINED
  • Anti-PEG hypersensitivity — documented phenomenon for PEGylated drugs upon repeated dosing (pegloticase, peginesatide); UNSTUDIED for PEG-MGF, possible serious hypersensitivity reactions cannot be excluded
  • Human data gap: NO long-term pharmacovigilance dataset for PEG-MGF — multi-month or multi-year human safety data have not been published. Safety statements framed exclusively as "theoretical" or "observed in preclinical research settings"
  • No reproductive-toxicity, pregnancy / lactation data and no drug-interaction studies in humans; PEG-MGF has NOT been tested for human use
  • Anti-doping: PEG-MGF is prohibited under WADA Class S2.5 (Growth factors and growth factor modulators) — in- and out-of-competition; positive tests result in sanctions in WADA-Code jurisdictions

References

  1. Goldspink G Changes in muscle mass and phenotype and the expression of autocrine and systemic growth factors by muscle in response to stretch and overload Journal of Anatomy 1999;194(Pt 3):323–334. 1999 .

    PMID: 10386770 View Source

  2. Yang SY, Goldspink G Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation FEBS Letters 2002;522(1-3):156–160. 2002 .

    DOI: 10.1016/S0014-5793(02)02918-6 PMID: 12270704 View Source

  3. Hill M, Goldspink G Expression and splicing of the insulin-like growth factor gene in rodent muscle is associated with muscle satellite (stem) cell activation following local tissue damage Journal of Anatomy 2003;202(Pt 2):169–177. 2003 .

    PMID: 12605581 View Source

  4. Mills P, Dominique JC, Lafrenière JF, Bouchentouf M, Tremblay JP A synthetic mechano growth factor E peptide enhances myogenic precursor cell transplantation success FASEB Journal 2007;21(10):2745–2756. 2007 .

    DOI: 10.1096/fj.06-7990com PMID: 17442731 View Source

  5. Brisson BK, Barton ER Insulin-like growth factor-I E-peptide activity is dependent on the IGF-I receptor Endocrinology 2012;153(9):4232–4242. 2012 .

    DOI: 10.1210/en.2012-1268 PMID: 22802461 View Source

  6. Quesada A, Micevych P, Handforth A Inversion of the muscle insulin-like growth factor isoform expression in old age and immobilization in rats; companion MGF cardioprotection rodent series Cardiovascular Research / companion series 2007. 2007 .

    PMID: 17449018 View Source

  7. Riddoch-Contreras J, Yang SY, Dick JR, Goldspink G, Orrell RW, Greensmith L Mechano-growth factor, an IGF-I splice variant, rescues motoneurons and improves muscle function in SOD1(G93A) mice Journal of Histochemistry and Cytochemistry / Experimental Neurology companion 2009. 2009 .

    PMID: 19729670 View Source

  8. Wikipedia contributors Mechano growth factor — chembox source for the 24-aa MGF E-peptide sequence YQPPSTNKNTKSQRRKGSTFEERK, molecular formula C₁₂₁H₁₉₉N₄₁O₄₀, molecular weight 2868.17 g·mol⁻¹, the rapid-in-vivo-metabolism PK note, and the N-terminal Tyr PEGylation site Wikipedia. 2026 .

    View Source

  9. World Anti-Doping Agency The 2026 Prohibited List — International Standard. Effective 1 January 2026. Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics), §S2.5 (Growth factors and growth factor modulators); MGF and PEG-MGF fall within scope, prohibited in- and out-of-competition WADA. 2026 .

    View Source

  10. UniProt Consortium P05019 — IGF1_HUMAN: Insulin-like growth factor I (Homo sapiens). Parent gene reference; the MGF E-peptide is the C-terminal 24-aa portion of the IGF-1Ec splice variant (P05019 isoform 4 / Ec) UniProt KB. 2026 .

    View Source

  11. U.S. Food and Drug Administration / Tercica Inc. Drugs@FDA: Increlex (mecasermin) injection — NDA 021839, initial approval 30 August 2005. For DISAMBIGUATION ONLY: mecasermin (DrugBank DB01277) is unmodified rh-IGF-1 (the full-length 70-aa native chain), distinct from the 24-aa MGF E-peptide / PEG-MGF — must not be conflated FDA Drugs@FDA. 2005 .

    View Source

Frequently Asked Questions

Is PEG-MGF the same as IGF-1?
No. PEG-MGF is the PEGylated form of the MGF E-peptide — a 24-amino-acid peptide (sequence YQPPSTNKNTKSQRRKGSTFEERK) that is the C-terminal E-domain of the IGF-1Ec splice variant of the human IGF1 gene (UniProt P05019 isoform 4). After post-translational processing, the mature 70-aa IGF-1 hormone and the 24-aa MGF E-peptide separate and act as DIFFERENT molecules with distinct pharmacology. Mature IGF-1 binds the IGF-1 receptor (IGF1R); the MGF E-peptide's actual receptor is NOT definitively identified, and several studies report that its activity is IGF-1R-INDEPENDENT (Mills 2007 PMID 17442731). Calling MGF "an IGF-1 variant" is therefore misleading at the level of pharmacology, even though both peptides arise from the same gene.
What does the PEG do?
PEG (polyethylene glycol) is a water-soluble polymer covalently attached to the peptide — for PEG-MGF, vendors typically PEGylate the N-terminal Tyr residue. The PEG moiety increases hydrodynamic radius (slowing renal filtration) and partially shields the peptide from proteolysis, extending systemic exposure. The native MGF E-peptide has a plasma half-life of ~5–7 minutes (Hill & Goldspink 2003 PMID 12605581); PEG-MGF is claimed by vendors to circulate for "several days", but NO peer-reviewed human PK study of PEG-MGF has been published, and the exact human half-life is not well-characterised. PEG itself is not pharmacologically active for the MGF target, but it can be IMMUNOGENIC — anti-PEG antibodies have been documented for other PEGylated drugs and could in principle develop with PEG-MGF, although this has not been studied.
Is PEG-MGF FDA-approved?
No. PEG-MGF has never been approved by the FDA, EMA, Health Canada, MHRA, TGA or any other major Western regulator for any indication. It has NO DrugBank monograph and NO canonical PubChem CID for the PEGylated conjugate. As of 2 May 2026, NO PEG-MGF or MGF interventional trial is registered on ClinicalTrials.gov (a v2 API audit returned only incidental keyword matches to unrelated studies — see the Clinical Status section above). PEG-MGF is sold only as a research chemical and is NOT legal for human consumption in the US, EU or UK.
Is PEG-MGF banned in sport?
Yes. PEG-MGF and the underlying MGF E-peptide are prohibited at all times (in- and out-of-competition) under the World Anti-Doping Agency 2026 Prohibited List, section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics), sub-section S2.5 (Growth factors and growth factor modulators). Athletes in WADA-Code jurisdictions face anti-doping sanctions for use, possession or trafficking.
How does PEG-MGF differ from the unmodified MGF E-peptide?
They share an identical 24-amino-acid sequence (YQPPSTNKNTKSQRRKGSTFEERK) but differ in three respects: (i) MOLECULAR WEIGHT — the conjugate adds the PEG molecule's MW (typically 5 kDa or 20 kDa branched PEG) to the peptide's ~2868 Da, giving a typical conjugate range of ~7.9 kDa to ~22.9 kDa; (ii) PLASMA HALF-LIFE — native ~5–7 min vs vendor-claimed "several days" for PEG-MGF (the PEG-MGF half-life is NOT peer-reviewed-confirmed in humans); (iii) CANONICAL CHEMISTRY — the free 24-aa peptide has a defined formula (C₁₂₁H₁₉₉N₄₁O₄₀, MW 2868.17 Da) while PEG-MGF has NO canonical CAS number, NO canonical PubChem CID and NO DrugBank monograph because the conjugate's MW depends on the PEG size chosen by the vendor.
What is the evidence base for PEG-MGF, and why is the page Limited-Data?
The mechanistic and physiological literature on the MGF E-peptide is dominated by Geoffrey Goldspink's lab at the Royal Free Hospital / UCL Medical School London (1996–2010s). Independent replication outside this lineage is sparse, and the most prominent non-Goldspink-lineage paper (Mills 2007 FASEB J PMID 17442731) reported that the synthetic E-peptide does NOT bind the IGF-1 receptor and raised replication concerns about earlier mechanism claims — i.e., the proposed mechanism of action itself is contested. There are ZERO registered Western clinical trials of PEG-MGF, no peer-reviewed human PK study and no DrugBank monograph. Combined, this is why the page carries the Limited Data Badge.

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