PEG-MGF

What it is

FDA's official name is Mechano Growth Factor Pegylated, or PEG-MGF. That sounds exact; the reviewed record is not. A complete identity still needs the base sequence, PEG size and shape, attachment site, linker, conjugation pattern, counter-ion, and impurity profile. PEG-MGF is not the IGF1 gene, human IGF-1Ec, mature IGF-1, a non-pegylated 24-amino-acid MGF E peptide, or MGF-C25E.

FDA's compounding statement concerns drug products containing the nominated PEG-MGF name and does not authenticate every material carrying that label. Human exercise studies measured endogenous transcripts and administered no peptide. Cell and animal papers used non-pegylated or otherwise different MGF identities. No human route, formulation, or analytically characterized PEG-MGF product was established by the identified evidence.

Why people care

PEG-MGF is discussed in muscle-growth and recovery claims because human exercise studies report endogenous IGF-1Ec/MGF transcript changes and some cell and animal studies report effects from non-pegylated MGF E peptides. Those evidence identities are often transferred to an unspecified pegylated product even though the identified human studies did not administer PEG-MGF and the cell literature includes a failed independent replication.

What humans actually show

PEG-MGF is an incompletely specified pegylated conjugate name, not an interchangeable label for endogenous IGF-1Ec, mature IGF-1, full-length MGF, or non-pegylated MGF E peptides. FDA places exact PEG-MGF in a nominated-but-withdrawn compounding-safety table, says it has identified no human-exposure data for PEG-MGF drug products, and plans a future non-binding PCAC discussion about possible 503A-list inclusion. The dated exact ClinicalTrials.gov search found zero studies, and no original human-administration paper was identified.

• biomarker — Eight younger adults aged 25 to 36 and seven older adults aged 70 to 82 after a single-leg high-resistance exercise bout; Route: No MGF or PEG-MGF was administered; quadriceps MGF mRNA was measured 2.5 hours after exercise; Outcome: Exercise-associated change in endogenous MGF transcript expression: The study reported increased MGF mRNA in exercised muscle in the younger group but not the older group. The seam: Fifteen participants; Acute gene-expression endpoint; No administered peptide or pegylated conjugate; No patient-important muscle-growth, recovery, function, or safety outcome; A transcript change does not establish a therapeutic target or product effect.
• biomarker — Ten younger men aged 18 to 25 and ten older men aged 60 to 75 after three sequential resistance workouts; Route: No MGF or PEG-MGF was administered; serial vastus-lateralis biopsies measured IGF-1Ea and MGF mRNA and total IGF-1 peptides; Outcome: Endogenous MGF transcript and total IGF-1 peptide changes across workout time points: MGF mRNA increased at post-workout time points in the older group while total muscle IGF-1 peptides remained stable; the paper said the physiological consequences were unknown. The seam: Twenty participants; Biomarker study rather than an administered-product trial; No PEG-MGF identity, route, exposure, or comparator; Different sampling and exercise design did not simply reproduce the earlier age-group pattern; No patient-important efficacy or safety conclusion.

Mechanistic and nonhuman evidence

• cell — Primary human muscle-cell cultures derived from neonatal, young-adult, and older-adult donors; Route: In-vitro exposure to a non-pegylated 24-amino-acid MGF E-domain peptide; Outcome: Proliferative lifespan, senescence, activation, differentiation, and fusion-related measures: The investigators reported age-dependent effects on proliferative lifespan and senescence and changes in fusion-related outcomes. The seam: Cell culture is not administration to people; The tested peptide was not an analytically defined PEG-MGF conjugate; Cell endpoints do not establish muscle growth, recovery, or function in humans; The findings conflict with a later independent cell-study nonreplication; No human pharmacokinetic or safety information.
• cell — C2C12 cells, primary human skeletal-muscle myoblasts, primary mouse muscle stem cells, and cardiac-myocyte signaling assays; Route: In-vitro exposure to native or stabilized MGF peptides, with IGF-1 or full-length IGF-1Eb controls in relevant assays; Outcome: Proliferation, differentiation, and p-ERK signaling: The study reported no MGF-peptide increase in proliferation, no inhibition of differentiation, and no demonstrated p-ERK response, while control IGF-1 identities produced responses in relevant assays. The seam: Cell assays are not human clinical outcomes; The study did not test a fully specified PEG-MGF product; A negative cell result does not establish human safety; Assays cannot determine human pharmacokinetics or interaction risk; The conflicting literature requires identity-specific interpretation.
• animal — Rat Achilles-tendon injury model; Route: Experimental administration of synthetic non-pegylated MGF-C25E in the injured-tendon model; Outcome: Achilles functional index, stiffness, histology, and tissue-remodeling measures: The paper reported differences favoring MGF-C25E over saline in selected functional, mechanical, and histologic measures. The seam: Rat injury evidence cannot establish a human outcome; MGF-C25E is not an unspecified PEG-MGF conjugate; The tendon model does not establish general muscle growth or recovery; No human adverse-effect characterization; No product-equivalence or interaction conclusion.

FDA and U.S. status

An exact Drugs@FDA API active-ingredient search returned no matches, and no FDA-approved PEG-MGF prescribing information was identified, but negative database searches are not converted into an FDA approval, nonapproval, or legal determination. FDA's current safety page places exact PEG-MGF in its nominated-but-withdrawn table and retains potential immunogenicity, impurity, characterization, and missing-human-exposure concerns. The May 2026 503A PDF separately places non-pegylated MGF in category 3. FDA plans a PCAC discussion before the end of February 2027 about possible PEG-MGF inclusion on the 503A bulks list; the exact meeting details remain pending, advisory recommendations are non-binding, and no vote or final list action is recorded. None of these compounding records is a drug approval or a legal conclusion about a particular product.

Risks and warning limits

• theoretical: FDA states that compounded PEG-MGF may present significant immunogenicity risk for certain routes of administration and may involve complexities in peptide-related impurities and active-pharmaceutical-ingredient characterization.
• not characterized: FDA says it has identified no human-exposure data for drug products containing PEG-MGF and lacks important information about whether PEG-MGF would harm humans. No FDA-approved label was identified, so this draft assigns no labeled contraindications, warnings, or adverse-reaction frequencies.

What remains unknown

• The complete molecular identity of material described only as PEG-MGF, including base sequence, PEG chemistry, attachment site, conjugation distribution, counter-ion, and impurity profile, remains unresolved by the name alone.
• Human pharmacokinetics, pharmacodynamics, exposure, metabolism, immunogenicity, and patient-important efficacy outcomes for an exact analytically characterized PEG-MGF conjugate remain unestablished by the identified evidence.
• Acute, chronic, immune, metabolic, reproductive, proliferative, and interaction risks in humans are not characterized by the identified human biomarker, cell, or animal records.
• Whether non-pegylated E-peptide findings transfer to a specified pegylated conjugate, and whether endogenous transcript changes predict any administered-product outcome, remain unknown.
• The future PCAC vote or recommendation, any final FDA 503A bulks-list action, and the exact identity described in future meeting materials remain pending.

Product identity and quality limits

• PEG-MGF is not a complete analytical identity without the base sequence, PEG molecular characteristics, attachment chemistry, conjugation distribution, counter-ion, concentration, purity, sterility, aggregation state, stability, and storage history.
• The IGF1 gene, endogenous IGF-1Ec transcript, full-length IGF-1Ec, mature IGF-1, a 24-amino-acid E peptide, MGF-C25E, a stabilized non-pegylated peptide, and a pegylated conjugate are not interchangeable evidence identities.
• A product name or certificate cannot establish equivalence to an original experiment or an FDA-reviewed drug identity.

What has been studied together

• PEG-MGF with exercise — no direct evidence: The human exercise studies changed mechanical exposure and measured endogenous MGF transcripts. They did not administer PEG-MGF and therefore do not establish a PEG-MGF/exercise coadministration effect or interaction.
• PEG-MGF with IGF-1 products, growth hormone-axis substances, anabolic agents, other peptides, or medicines — no direct evidence: The exact ClinicalTrials.gov and PubMed screens did not identify adequate direct human PEG-MGF coadministration or interaction evidence. No approved label supplies interaction instructions. Missing evidence does not establish compatibility or safety.

What people are hearing

These are claims this profile checks, not established conclusions.

• Claim under review: “An endogenous MGF mRNA response to resistance exercise proves that administering PEG-MGF increases muscle growth or recovery.”
• Claim under review: “A result with full-length IGF-1Ec or a non-pegylated MGF E peptide transfers to any material labeled PEG-MGF.”
• Claim under review: “FDA compounding-list consideration or a planned advisory-committee meeting means PEG-MGF is FDA approved or has received a final favorable FDA decision.”

Questions readers raise

• No reproducible community sample was collected for this profile.

The community-signal layer is not efficacy or safety evidence. Its current limits are:

• No reproducible community sample has been collected for this profile.
• Self-reports would be subject to selection and reporting bias.
• A PEG-MGF name would not verify the base sequence, PEG chemistry, purity, sterility, or exposure.
• Concurrent medicines, substances, health conditions, diet, and training could confound an anecdote.
• Reported outcomes and adverse effects could not be independently verified.
• Anecdotes cannot establish efficacy, safety, approval, product identity, or interaction compatibility.

What would change this answer

• A registered controlled human trial administering a fully specified and analytically characterized PEG-MGF conjugate with posted or peer-reviewed outcomes would change the current no-administered-human-evidence boundary for that exact intervention and population.
• Validated structural and quality documentation defining the base peptide, PEG chemistry, conjugation site and distribution, counter-ion, impurity profile, sterility, and stability would narrow the current product-identity uncertainty for the tested material.
• A completed PCAC meeting, exact voting question, committee vote, written FDA rationale, and later final bulks-list action would update the current pending-compounding boundary; none would by itself constitute drug approval.
• An FDA approval action and final prescribing information for an exact PEG-MGF drug product would change the current not-verified boundary and establish product-specific indications, identity, warnings, and adverse reactions.

Sources and records

• WADA — 2026 Prohibited List

• Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks — U.S. Food and Drug Administration
• Bulk Drug Substances Nominated for Use in Compounding Under Section 503A, updated May 14, 2026 — U.S. Food and Drug Administration
• Upcoming Pharmacy Compounding Advisory Committee meeting on five 503A bulk drug substances — U.S. Food and Drug Administration
• Drugs@FDA API exact active-ingredient search for PEG-MGF and Mechano Growth Factor — U.S. Food and Drug Administration
• ClinicalTrials.gov exact-variant search for PEG-MGF — ClinicalTrials.gov
• PubMed exact-variant title and abstract search for PEG-MGF — National Library of Medicine
• IGF1 insulin like growth factor 1, human Gene ID 3479 — National Center for Biotechnology Information
• Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise — PubMed
• IGF-1 splice variant and IGF-1 peptide expression patterns in young and old human skeletal muscle prior to and following sequential exercise bouts — PubMed
• 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 — Mechanisms of Ageing and Development / PubMed
• 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 — American Journal of Physiology-Endocrinology and Metabolism / PubMed
• Mechano-growth factor E peptide promotes healing of rat injured tendon — PubMed