Bestatin (Ubenimex) vs Thymalin
Natural dipeptide analogue aminopeptidase inhibitor with dual immunostimulatory and antitumor activity, approved in Japan as adjuvant cancer therapy
Russian thymic peptide complex that rejuvenates immune function and supports healthy aging
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
Thymalin
5–10 mg
Frequency
Bestatin (Ubenimex)
Once daily
Thymalin
Once daily
Administration
Bestatin (Ubenimex)
Oral (capsule)
Thymalin
Intramuscular injection
Cycle length
Bestatin (Ubenimex)
12+ weeks
Thymalin
4-6 weeks
Onset speed
Bestatin (Ubenimex)
Moderate (1-2 weeks)
Thymalin
Moderate (1-2 weeks)
Evidence level
Bestatin (Ubenimex)
Moderate human trials (Phase 1-2)
Thymalin
Limited human trials
Benefit ratings
Immune
Healing & Recovery
Anti-Aging
Immune Restoration
Longevity Support
Disease Prevention
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
Thymalin
Molecular formula
Complex mixture; active dipeptide EW: C16H19N3O5
Molecular weight
Polypeptide complex; components 250-1000 Da; active dipeptide EW ~321 Da
Half-life
Not precisely characterized for complex; immune effects persist weeks post-administration
Bioavailability
High via intramuscular or subcutaneous injection
CAS number
63958-90-7
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].
Thymalin
Intramuscular injection
5-10 mg reconstituted in saline
Once daily · 5-10 day course, often repeated every 6 months
Reflects the Russian clinical course used in immune-restoration and gerontology protocols, typically 10 mg IM daily for 5-10 days [1].
Subcutaneous injection
10 mg
Once daily · Up to 20 day course, repeated every 6 months
Subcutaneous administration is used in community practice at the same 10 mg daily dosing; longer 20-day courses are described for cyclical immune support [1].
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.
Thymalin
Aging Adults Seeking Immune Support
Thymalin is especially valuable for people over 55 whose thymus gland has naturally shrunk with age. By stimulating thymic function, it helps restore the immune training center that your body relies on to fight infections and stay healthy.
Longevity and Anti-Aging Protocols
Clinical studies tracking patients for 6-8 years showed Thymalin reduced mortality by 2.0-2.1-fold. Combined with Epitalon, the mortality reduction reached an impressive 4.1-fold, making this combination one of the most studied longevity peptide protocols.
Seasonal Illness Prevention
Research shows Thymalin cuts respiratory infection rates by 2.0-2.4-fold. A short 10-day course before cold and flu season can significantly boost your immune defenses for months afterward.
Side effects
Bestatin (Ubenimex)
Common
- Gastrointestinal discomfort
- Skin rash or pruritus
- Facial flushing
- Fatigue
Uncommon
- Elevated liver enzymes
- Mild leukopenia
Serious
- Severe allergic reaction
Thymalin
Common
- No side effects in most patients
- Mild injection site reaction
Uncommon
- Transient low-grade fever
- Mild flu-like symptoms
- Temporary headache
Serious
- Severe 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
Thymalin
Evidence level
Limited human trials
FDA status
Research compound
Safety overview
Thymalin has an excellent safety profile based on over 40 years of clinical use in Russia. Most patients experience zero side effects, and the peptide complex has been described as 'practically non-toxic' in research literature. It has been used safely in thousands of patients, including elderly populations over extended periods.
Contraindications
- Active thymic tumors or malignancies
- Known hypersensitivity to animal-derived peptide products
- Pregnancy and breastfeeding (insufficient safety data)
- Severe uncontrolled autoimmune disease 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 Thymalin if...
- Immune system restoration in aging adults
- Longevity and healthy aging support
- Reducing infection frequency and severity
- Multi-system health optimization