Side-by-side · Research reference
PEG-MGFvsSS-31
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
AAnimal-MechanisticHUMAN-REVIEWED2/69 cited
BPhase 3HUMAN-REVIEWED9/43 cited
PEG-MGF
IGF-1Ec Splice Variant · PEGylated
~2 hrHalf-life (PEG)
~7 minNative MGF t½
IGF-1EcSplice variant
SQ · Research Protocol
SS-31
Cardiolipin-binding · Mitochondrial protective
SQ · Abdomen · Once daily
01Mechanism of Action
Parameter
PEG-MGF
SS-31
Primary target
IGF-1 receptor on muscle satellite cells and myocytes
Cardiolipin in inner mitochondrial membraneSzeto 2014
Pathway
IGF-1R → PI3K/Akt → mTOR activation → Satellite cell proliferation & myoblast fusion
Cardiolipin binding → cristae stabilisation → ETC integrity → reduced ROS + preserved ATP synthesisSzeto 2014Szilagyi 2009
Downstream effect
Satellite cell activation, muscle fiber repair, localized hypertrophy signaling
Mitochondrial bioenergetic preservation; cardio-, neuro-, and reno-protective effects in animal + clinical studiesSzeto 2014
Feedback intact?
Partially bypassed — does not require hepatic IGF-1 synthesis
—
Origin
IGF-1Ec splice variant (exon 4–6) conjugated to polyethylene glycol for extended circulation
Synthetic tetrapeptide D-Arg-Dmt-Lys-Phe-NH₂; cell-permeable, mitochondrial-selectiveSzeto 2014
Antibody development
Unknown — no long-term human immunogenicity data
—
02Dosage Protocols
Parameter
PEG-MGF
SS-31
Research dose range
100–200 mcg
Extrapolated from animal models; no validated human protocols.
—
Frequency
Post-training or daily
Timing to match endogenous MGF pulse post-exercise.
Once daily
Half-life
~2 hours (PEGylated)
Native MGF: ~7 min; PEGylation extends circulation.
~3 h plasma; tissue uptake longer
Evidence basis
Animal / mechanistic
Multiple Phase 3 trials (Barth, AMD, ischemia-reperfusion)Szeto 2014Szilagyi 2009
Reconstitution
Sterile bacteriostatic water
Lyophilized form; store reconstituted at 2–8 °C.
Bacteriostatic water
PEG molecular weight
Typically 5–30 kDa
Higher MW = longer t½, greater steric hindrance.
—
Timing
Within 30–60 min post-training
Aligns with endogenous MGF window.
Morning fasted preferred; pre-workout for exercise-induced mitochondrial stress
Standard dose
—
40 mg / day SQ (clinical trials)Szeto 2014
Anecdotal community range 5-10 mg/day. Phase 3 trials use 40 mg.
Lower / starter dose
—
5 mg / day (anecdotal)
Duration
—
Indefinite for mitochondrial disease; cycled for healthspan use
03Metabolic / Fat Loss Evidence
Parameter
PEG-MGF
SS-31
Primary target
Muscle tissue (satellite cells, myocytes) — not adipose-specific
—
Indirect metabolic effect
IGF-1 signaling may modulate insulin sensitivity and lipid metabolismRen 2015
Mechanism distinct from direct lipolytic peptides.
—
Body composition
Lean mass preservation / hypertrophy focus
—
Fat loss evidence
No direct human or animal RCT data for PEG-MGF-driven fat reduction
—
04Side Effects & Safety
Parameter
PEG-MGF
SS-31
Injection site reaction
Erythema, induration (common with SQ peptides)
Erythema, mild pruritus
Hypoglycemia risk
IGF-1 axis activation can lower blood glucose
—
IGF-1R overstimulation
Theoretical risk of aberrant cell proliferation with chronic supraphysiological exposure
—
Fluid retention
Possible with IGF-1 pathway activation (dose-dependent)
—
PEG accumulation
Chronic high-dose PEGylated proteins may accumulate in tissues; clearance slower in renal impairment
—
Antibody formation
PEGylated proteins can elicit anti-PEG antibodies (neutralizing potential unknown)
—
Cancer risk
IGF-1 axis stimulation contraindicated in active malignancy
—
Human safety data
Absent — no published human trials for PEG-MGF
—
GI symptoms
—
Nausea (uncommon)
Headache
—
Reported in some Phase 3 trials
Cardiovascular
—
Cardio-protective in studies; no signal of harm
Pregnancy / OB
—
Avoid — insufficient data
Absolute Contraindications
PEG-MGF
- ·Active malignancy or history of cancer (IGF-1R proliferative signaling)
- ·Known hypersensitivity to PEGylated compounds
- ·Pregnancy / lactation (no reproductive toxicity data)
SS-31
- ·Pregnancy / breastfeeding
- ·Hypersensitivity to peptide
Relative Contraindications
PEG-MGF
- ·Diabetes (monitor glucose closely)
- ·Renal impairment (PEG clearance reduced)
- ·Retinopathy (IGF-1 axis effects on vascular proliferation)
SS-31
- ·None established
05Administration Protocol
Parameter
PEG-MGF
SS-31
1. Reconstitution
Add 1–2 mL bacteriostatic water to lyophilized vial. Swirl gently — do not shake. Solution should be clear to slightly opalescent.
Add bacteriostatic water per label. Light-protected handling.
2. Injection site
Subcutaneous — abdomen or thigh. Rotate sites to avoid lipodystrophy. Avoid areas with scar tissue or active inflammation.
SQ — abdomen or thigh. Rotate sites.
3. Timing
Post-training preferred (within 30–60 min) to align with endogenous MGF expression window. Alternatively, daily morning dose on non-training days.
Morning fasted; pre-workout for exercise-augmented mitochondrial stress.
4. Storage
Lyophilized: room temperature, light-protected, desiccated. Reconstituted: refrigerate 2–8 °C, use within 14–21 days.
Lyophilised: refrigerate, light-protected. Reconstituted: refrigerate ≤30 days.
5. Needle
29–31G insulin syringe, 8–12 mm length. Pinch skin fold, insert at 45° angle for subcutaneous delivery.
29–31G, 4–8 mm insulin syringe.
06Stack Synergy
PEG-MGF
+ BPC-157
ModerateBPC-157 promotes angiogenesis and tendon/ligament repair via VEGF and growth factor modulation, while PEG-MGF targets satellite cell activation and myocyte proliferation. Complementary pathways for comprehensive tissue repair post-injury or intensive training. BPC-157's systemic stability and oral bioavailability contrast with PEG-MGF's localized IGF-1R signaling.
- PEG-MGF
- 100–200 mcg SQ post-training
- BPC-157
- 250–500 mcg SQ or oral, twice daily
- Duration
- 4–6 weeks (injury-dependent)
- Primary benefit
- Accelerated muscle and connective tissue repair, enhanced recovery
+ TB-500
StrongTB-500 (Thymosin Beta-4 fragment) upregulates actin polymerization, cell migration, and anti-inflammatory pathways, while PEG-MGF drives satellite cell proliferation via IGF-1R/mTOR. Synergistic for muscle regeneration: TB-500 mobilizes progenitor cells, PEG-MGF stimulates their differentiation into myocytes. Both have overlapping but distinct repair cascades.
- PEG-MGF
- 100–200 mcg SQ post-training
- TB-500
- 2–5 mg SQ, 2× per week (loading), then weekly
- Timing
- Stagger injections by 6–12 hours
- Primary benefit
- Maximal satellite cell recruitment and myogenic differentiation, injury repair
SS-31
+ MOTS-c
ModerateSS-31 and MOTS-c address mitochondrial decline through complementary axes. SS-31 protects existing mitochondrial structure (cardiolipin binding, cristae stabilisation). MOTS-c upregulates AMPK/PGC-1α, triggering biogenesis of new mitochondria. Together they pair preservation with renewal — anecdotally favoured in healthspan and post-cardio-event recovery protocols.
- SS-31
- 5–10 mg SQ · daily morning
- MOTS-c
- 5 mg SQ · 2× per week pre-workout
- Primary benefit
- Mitochondrial preservation + biogenesis