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Research profile · Peptide

MGF

Also known as Mechano growth factor, IGF-1Ec E-domain peptide

Animal — evidence level 2 of 4: Animal evidenceExperimental — UK regulatory status: Experimental — not authorised for human use in the UK

Overview

A peptide from a splice variant of IGF-1 whose foundational finding failed independent replication.

Category
Peptide
Highest evidence level identified
Animal evidence
Last scientifically reviewed
20 August 2026
Last regulatory review
20 August 2026

Mechanism under investigation

MGF is the C-terminal E-domain peptide of a splice variant of insulin-like growth factor 1 that is upregulated in skeletal muscle after mechanical loading or damage. It has been proposed that this peptide acts distinctly from mature IGF-1 by activating quiescent satellite cells and promoting myoblast proliferation while delaying fusion. That proposal is contested: a 2014 replication attempt by two pharmaceutical companies failed to reproduce the effect and concluded that the findings call into question whether the peptide has a physiological role at all.

Research areas

  • Muscle biology
  • Growth factor signalling

These are fields in which the compound has been investigated. Listing a field is not a statement that anything was demonstrated within it.

Current evidence

In-vitro evidence

Cells, tissues or biochemical systems outside a living organism.

Present but contradictory, and the contradiction is the important part. The original 2002 work reported that the E-domain peptide affected myoblast proliferation and differentiation differently from mature IGF-1. A 2014 replication attempt across four separate cell systems found the peptide failed to increase proliferation, failed to inhibit differentiation and failed to activate the expected signalling — while mature IGF-1 produced robust responses in the same systems.

Animal evidence

Studies in living non-human animals.

Limited and mostly low-citation. Rodent and rabbit studies exist, but much of the animal literature measures endogenous expression rather than administering the peptide. No large or replicated efficacy programme was located.

Human observational evidence

Studies observing people without assigning an intervention.

Exists, but only for endogenous expression rather than administration. Human muscle biopsy work has measured splice-variant messenger RNA after resistance exercise. The peptide was measured, never given.

Clinical-trial evidence

Studies assigning an intervention to human participants.

None. No registered interventional study was found, and a search of the indexed literature returned no human interventional trial.

Study limitations

  • The foundational satellite-cell finding failed independent replication in a well-powered multi-system attempt by two separate pharmaceutical companies.
  • No human has ever been administered this peptide in a registered trial. All human data concern endogenous expression after exercise.
  • Much of the supporting literature comes from a single research lineage, which limits evidential independence.
  • Animal studies are heterogeneous in species, model and endpoint, with small samples and no replication programme.

UK regulatory context

Experimental — not authorised for human use in the UK

A compound appearing in research literature that holds no UK authorisation for human use in any indication.

Source: The Human Medicines Regulations 2012, regulation 46 — prohibition on sale or supply of an unauthorised medicinal product (opens legislation.gov.uk in a new tab) (legislation.gov.uk)

Regulatory classification is jurisdiction-specific. A compound authorised elsewhere is not thereby authorised in the UK, and a supplier’s description of a substance does not determine how it is classified in law. See safety and regulation for the framework and the authoritative sources.

Safety and interpretation

No safety data from controlled human administration exist, because no such study has been conducted. Because the peptide sits on the IGF-1 axis, mitogenic concerns are biologically plausible but unproven and unquantified. Material supplied outside a regulated chain has no assured composition or purity.

References