Side-by-side · Research reference
MK-677vsThymosin α-1
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 2Reviewed13/45 cited
BPhase 3Reviewed8/39 cited
MK-677
Oral GHS · Ibutamoren
Oral capsule · 1×/day
Thymosin α-1
Immune modulator · Approved (some countries)
SQ · 2× weekly · 6+ months for chronic indications
01Mechanism of Action
Parameter
MK-677
Thymosin α-1
Primary target
Ghrelin receptor (GHS-R1a)Murphy 1998
Toll-like receptor 9 (TLR9) + T-cell maturation pathwayCamerini 2001
Pathway
GHS-R1a → Gαq → Ca²⁺ → sustained GH pulses across 24 hrNass 2008
TLR9 activation → ↑ IFN-α + IL-2 + IFN-γ → enhanced T-cell function + dendritic cell maturationIyer 2007
Downstream effect
Sustained GH + IGF-1 elevation; appetite stimulation; lean mass preservationNass 2008
Restored T-cell function, improved viral clearance, anti-tumour adjuvant effectsIyer 2007
Origin
Non-peptide spiroindane-piperidine small molecule designed at MerckMurphy 1998
Synthetic 28-AA peptide identical to natural Tα-1 isolated from thymus extractCamerini 2001
Antibody development
—
—
02Dosage Protocols
Parameter
MK-677
Thymosin α-1
Standard dose
10–25 mg / day oralNass 2008
25 mg used in Nass 2008 elderly trial; 10–15 mg common community dose.
—
Frequency
Once daily, oral
2× weekly (Mon/Thu typical)
Lower / starter dose
5 mg / day
0.8 mg per injection
Evidence basis
Phase 2 trials (Nass 2008, Murphy 1998)Nass 2008Murphy 1998
Phase 3 + approved (35+ countries as Zadaxin)Iyer 2007
Duration
8–16 weeks per cycle (off-cycle to reset receptor sensitivity)
6–12 months for chronic indications
Reconstitution
Oral, no reconstitution
Sterile water for injection per vial label
Timing
Pre-sleep preferred for natural GH pulse alignment
No specific time
04Side Effects & Safety
Parameter
MK-677
Thymosin α-1
Increased appetite
Strong appetite increase via ghrelin agonism
—
Water retention
Mild edema, paresthesias
—
Cancer risk
Contraindicated in active malignancy (GH/IGF-1 axis)
No signal — used as adjuvant in oncology
Cardiovascular
No clear adverse signal in trials; congestive heart failure caution
—
Drowsiness
Common, especially during initial weeks
—
Pregnancy / OB
Avoid
Avoid
Injection site reaction
—
Erythema, mild discomfort
GI symptoms
—
Rare nausea
Fatigue
—
Common during initial weeks
Fever / flu-like
—
Mild interferon-like response possible
Autoimmune
—
Theoretical risk; caution in active autoimmune disease
Absolute Contraindications
MK-677
- ·Active malignancy
- ·Pregnancy / breastfeeding
- ·Disrupted hypothalamic-pituitary axis
- ·Congestive heart failure (caution)
Thymosin α-1
- ·Pregnancy / breastfeeding
- ·Hypersensitivity to peptide
- ·Concurrent immunosuppressant therapy (transplant patients)
Relative Contraindications
MK-677
- ·Untreated diabetes
- ·Pre-diabetes
- ·Severe insulin resistance
Thymosin α-1
- ·Active autoimmune disease
- ·Severe immunocompromised state without supervision
05Administration Protocol
Parameter
MK-677
Thymosin α-1
1. Form
Capsule or oral solution. No injection.
Add 1 mL sterile water per 1.6 mg vial → 1.6 mg/mL.
2. Site
Oral. Take with or without food.
SQ — abdomen, thigh, or upper arm. Rotate sites.
3. Timing
Pre-sleep preferred — aligns with natural GH pulse.
2× weekly, e.g. Monday + Thursday.
4. Storage
Capsule: room temp ≤25 °C, dry place.
Lyophilised: refrigerate. Reconstituted: refrigerate, use within 24 h.
5. Caveat
Monitor HbA1c every 8–12 weeks during chronic use.
27–31G, 4–8 mm insulin syringe.