Bestatin (Ubenimex) vs Thymosin Alpha-1
Natural dipeptide analogue aminopeptidase inhibitor with dual immunostimulatory and antitumor activity, approved in Japan as adjuvant cancer therapy
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
Bestatin (Ubenimex)
30–30 mg
Thymosin Alpha-1
1.6–1.6 mg
Frequency
Bestatin (Ubenimex)
Once daily
Thymosin Alpha-1
Twice weekly
Administration
Bestatin (Ubenimex)
Oral (capsule)
Thymosin Alpha-1
Subcutaneous injection
Cycle length
Bestatin (Ubenimex)
12+ weeks
Thymosin Alpha-1
8-12 weeks
Onset speed
Bestatin (Ubenimex)
Moderate (1-2 weeks)
Thymosin Alpha-1
Moderate (1-2 weeks)
Evidence level
Bestatin (Ubenimex)
Moderate human trials (Phase 1-2)
Thymosin Alpha-1
Moderate human trials (Phase 1-2)
Benefit ratings
Immune
Healing & Recovery
Anti-Aging
Immune Activation
Infection Fighting
Immune Balance
Compound specifications
Bestatin (Ubenimex)
Molecular formula
C16H24N2O4
Molecular weight
308.37 g/mol
Half-life
Approximately 2-3 hours (oral administration)
Bioavailability
Well absorbed orally; peak plasma concentration reached within 1-2 hours
CAS number
58970-76-6
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
Bestatin (Ubenimex)
Oral
30 mg
Once daily · Long-term, alongside maintenance chemotherapy
30 mg by mouth once daily is the approved Japanese dose used as add-on therapy after leukemia remission. It helped patients, especially older adults, stay in remission longer [4][1].
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
Some immune-adjuvant and acute protocols front-load with daily dosing before settling to the standard twice-weekly schedule [4][6].
Best suited for
Bestatin (Ubenimex)
Adjunctive AML Immunotherapy
Bestatin is specifically approved in Japan for patients with acute non-lymphocytic leukemia who have achieved complete remission after induction chemotherapy. [10] Clinical trials demonstrated significant prolongation of disease-free survival when bestatin was added to standard maintenance therapy [3][4].
Post-Chemotherapy Immune Recovery
By stimulating bone marrow stem cell proliferation and enhancing T-lymphocyte and macrophage function, bestatin supports immune system recovery in patients whose immune function has been suppressed by cytotoxic chemotherapy [1][3].
Pulmonary Arterial Hypertension (Investigational)
Through inhibition of LTA4 hydrolase and reduction of pro-inflammatory leukotriene B4, [5] bestatin is being investigated as a novel approach to PAH. Eiger BioPharmaceuticals conducted Phase 2 trials (NCT02664558) [7] and received FDA orphan drug designation for this indication [9].
Lymphedema Management (Investigational)
The anti-inflammatory properties of bestatin via LTB4 pathway inhibition have led to Phase 2 investigation (NCT02700529) [8] for lymphedema, a condition with limited treatment options where inflammation plays a key role in disease progression.
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
Bestatin (Ubenimex)
Common
- Gastrointestinal discomfort
- Skin rash or pruritus
- Facial flushing
- Fatigue
Uncommon
- Elevated liver enzymes
- Mild leukopenia
Serious
- Severe allergic reaction
Thymosin Alpha-1
Common
- Injection site reactions
- Mild fatigue
- Flu-like symptoms
Uncommon
- Mild fever
- Lymph node awareness
Serious
- Allergic reaction
Safety & evidence
Bestatin (Ubenimex)
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
Bestatin (ubenimex) has an established safety profile based on decades of clinical use in Japan for AML maintenance therapy at 30 mg daily. [3][10] The compound is generally well-tolerated, with the most common side effects being mild gastrointestinal symptoms and skin reactions. [10] Japanese post-marketing surveillance and long-term clinical studies have not identified major safety concerns at standard doses. Phase 2 trials in the US for PAH and lymphedema [7][8] also demonstrated acceptable safety profiles at higher doses.
Contraindications
- Known hypersensitivity to bestatin or any component of the formulation
- Pregnancy and breastfeeding (insufficient safety data)
- Severe hepatic impairment
- Active autoimmune diseases in flare
Thymosin Alpha-1
Evidence level
Moderate human trials (Phase 1-2)
FDA status
FDA approved for other use
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 Bestatin (Ubenimex) if...
- Adjunctive immunotherapy following chemotherapy for acute leukemia
- Restoring immune function during and after cancer treatment
- Supporting bone marrow recovery post-chemotherapy
- Emerging treatment for pulmonary arterial hypertension (PAH)
Choose Thymosin Alpha-1 if...
- Immune system strengthening
- Chronic infection support
- Cancer adjunct therapy
- Healthy aging immune support