Thymopentin (TP-5) vs Thymosin Alpha-1
Immune-boosting pentapeptide fragment that enhances T-cell function and dendritic cell maturation
Your immune system's master trainer—a naturally occurring thymus peptide that wakes up tired immune cells, helps your body fight infections, and keeps your defenses sharp as you age.
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
Thymopentin (TP-5)
50–50 mg
Thymosin Alpha-1
1.6–1.6 mg
Frequency
Thymopentin (TP-5)
Once daily
Thymosin Alpha-1
Twice weekly
Administration
Thymopentin (TP-5)
Subcutaneous injection
Thymosin Alpha-1
Subcutaneous injection
Cycle length
Thymopentin (TP-5)
4-6 weeks
Thymosin Alpha-1
8-12 weeks
Onset speed
Thymopentin (TP-5)
Moderate (1-2 weeks)
Thymosin Alpha-1
Moderate (1-2 weeks)
Evidence level
Thymopentin (TP-5)
Moderate human trials (Phase 1-2)
Thymosin Alpha-1
Moderate human trials (Phase 1-2)
Benefit ratings
Immune Enhancement
Cardiovascular Support
Post-Recovery Support
Immune Activation
Infection Fighting
Immune Balance
Compound specifications
Thymopentin (TP-5)
Molecular formula
C30H49N9O9
Molecular weight
679.8
Half-life
30 seconds to few minutes in plasma
Bioavailability
Sustained release via subcutaneous route
CAS number
69558-55-0
Thymosin Alpha-1
Molecular formula
C129H215N33O55
Molecular weight
3108.32 g/mol
Half-life
Approximately 2 hours
Bioavailability
High when injected subcutaneously (rapid absorption, peak at ~2 hours)
CAS number
62304-98-7
Dosing compared
Thymopentin (TP-5)
Subcutaneous injection
50 mg
Three times weekly · 6 weeks to 48 weeks depending on indication
Dose used in controlled clinical trials, e.g. 50 mg SC three times weekly in HIV and atopic dermatitis studies [5].
Intravenous injection
50 mg by slow IV
Repeated injections (e.g. three times weekly) · Several weeks
Slow intravenous infusion was used in rheumatoid arthritis trials and may enhance in-vivo potency versus bolus dosing [5].
Thymosin Alpha-1
Subcutaneous injection
1.6 mg
Twice weekly (3-4 days apart) · 6-12 months
Established clinical dose for thymalfasin (Zadaxin); body-surface-scaled as 900 mcg/m2 [4][6]. Phase III chronic hepatitis B trials used 1.6 mg SC twice weekly for 6-12 months [4].
1.6 mg daily, then 1.6 mg twice weekly
Daily for an initial loading period, then twice weekly · 12+ weeks
The schedule used in a randomized trial in HBV-related acute-on-chronic liver failure: 1.6 mg daily for the first week, then twice weekly to week 12 [3].
Best suited for
Thymopentin (TP-5)
Immune System Enhancement
Thymopentin directly increases T-cell function and promotes dendritic cell maturation, making it ideal for people seeking to boost immune response naturally
Cardiac Health Support
Clinical trials show thymopentin improves ejection fraction and exercise capacity in elderly heart failure patients while enhancing immune markers
Post-Surgery Recovery
Helps restore immune function after major surgery and protects important immune responses during recovery period
Thymosin Alpha-1
Chronic Hepatitis B or C Support
Thymosin Alpha-1 has its strongest clinical evidence here. Multiple trials show it helps clear viral loads and normalize liver enzymes, especially when combined with antiviral medications. It's approved in over 30 countries specifically for hepatitis treatment.
Cancer Treatment Support
When used alongside chemotherapy, Thymosin Alpha-1 may help maintain immune function that chemo tends to suppress. Research in lung cancer, melanoma, and liver cancer shows improved outcomes when added to standard treatments. It helps your immune system keep fighting even during tough treatments.
Age-Related Immune Decline
As you age, your thymus shrinks and produces less thymosin naturally—a process called immunosenescence. Supplementing with Thymosin Alpha-1 may help compensate, keeping your immune defenses more youthful and responsive. Think of it as replacing what your body makes less of over time.
Severe Infection Recovery
In sepsis and critical infections, Thymosin Alpha-1 has shown promise for reducing mortality by helping restore immune balance. It's particularly interesting because it modulates immunity rather than just boosting it—calming overreaction while enhancing pathogen-fighting ability.
Side effects
Thymopentin (TP-5)
Common
- Local injection site reaction
- Mild fatigue
- Transient fever
Uncommon
- Muscle aches
- Mild headache
Serious
- Allergic reaction
Thymosin Alpha-1
Common
- Injection site reactions
Uncommon
- Mild fatigue
- Flu-like symptoms
- Mild fever
- Lymph node awareness
Serious
- Allergic reaction
Safety & evidence
Thymopentin (TP-5)
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
Thymopentin is well-tolerated with minimal side effects reported in clinical trials. Most adverse events are mild and local. No serious safety concerns have emerged from decades of clinical use in China and Europe.
Contraindications
- Pregnancy and breastfeeding
- Active malignancy (without medical supervision)
- Severe immunosuppression
- Hypersensitivity to peptide medications
Thymosin Alpha-1
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Not FDA approved. There is no thymalfasin application in Drugs@FDA. It is used outside the US (as Zadaxin) for chronic hepatitis B and as an immune adjuvant.
Safety overview
Thymosin Alpha-1 has one of the most extensive safety records of any peptide, with decades of clinical use across multiple countries. Studies consistently report minimal side effects—mostly limited to mild injection site reactions. The 2-hour half-life means it doesn't accumulate in your system. It's been used safely in thousands of patients with hepatitis, cancer, and other serious conditions.
Contraindications
- Organ transplant recipients on immunosuppressants
- Active autoimmune disease flares
- Known allergy to thymosin peptides
- Pregnancy or breastfeeding
- Children under 18 without medical supervision
Which is right for you?
Choose Thymopentin (TP-5) if...
- Immune system strengthening
- Recovering from illness or surgery
- Managing autoimmune conditions
- Supporting cardiac health in elderly patients
Choose Thymosin Alpha-1 if...
- Immune system strengthening
- Chronic infection support
- Cancer adjunct therapy
- Healthy aging immune support