Relaxin-2 (Serelaxin) vs Thymosin Beta-4
Recombinant human relaxin-2 studied for acute heart failure recovery and cardiovascular support
The body's natural healing peptide that accelerates tissue repair and reduces inflammation
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
Relaxin-2 (Serelaxin)
30–30 mcg/kg/day
Thymosin Beta-4
2–5 mg
Frequency
Relaxin-2 (Serelaxin)
Once daily
Thymosin Beta-4
Twice weekly
Administration
Relaxin-2 (Serelaxin)
Intravenous (IV) infusion
Thymosin Beta-4
Subcutaneous injection
Cycle length
Relaxin-2 (Serelaxin)
8-12 weeks
Thymosin Beta-4
8-12 weeks
Onset speed
Relaxin-2 (Serelaxin)
Moderate (1-2 weeks)
Thymosin Beta-4
Moderate (1-2 weeks)
Evidence level
Relaxin-2 (Serelaxin)
Limited human trials
Thymosin Beta-4
Moderate human trials (Phase 1-2)
Benefit ratings
Cardiovascular Function
Heart Failure Support
Acute Medical Management
Wound Healing
Inflammation Reduction
Tissue Regeneration
Compound specifications
Relaxin-2 (Serelaxin)
Molecular formula
C256H408N74O74S8
Molecular weight
5,963 Da (Daltons)
Half-life
Varies by route of administration
Bioavailability
Varies by route of administration
CAS number
See PubChem for identifiers
Thymosin Beta-4
Molecular formula
C212H350N56O78S
Molecular weight
4963
Half-life
Dose-dependent (increases with higher doses)
Bioavailability
100% (subcutaneous and intravenous)
CAS number
77591-33-4
Dosing compared
Relaxin-2 (Serelaxin)
Intravenous
30 mcg/kg/day
Continuous IV infusion · 48 hours
Weight-adjusted continuous IV infusion used across the RELAX-AHF programme for acute heart failure; improved dyspnea but did not reduce mortality in RELAX-AHF-2 [3][5]. Hospital administration only.
Thymosin Beta-4
Subcutaneous injection
2-5 mg (community injectable practice for 'TB-500')
Once or twice weekly · 4-6 week loading phase, then weekly maintenance
Documented community/research-practice injectable dosing for tissue repair; thymosin beta-4 has ~100% bioavailability by the subcutaneous route [1]. Not an FDA-approved use.
Topical ophthalmic (eye drops)
0.1% (1 mg/mL) RGN-259 solution, 1 drop
Several times daily (e.g. up to 5x/day) · 4 weeks
0.1% RGN-259 ophthalmic solution used in phase III neurotrophic keratopathy and dry-eye trials, applied as eye drops several times daily for ~4 weeks [5].
Intravenous injection
450-1200 mg
IV push daily for the first 3 days, then weekly · Total of 7 doses over ~5 weeks
Doses studied in the RGN-352 acute myocardial infarction clinical program, given IV after PCI [6].
Best suited for
Relaxin-2 (Serelaxin)
Acute heart failure symptom management
Relaxin-2 (Serelaxin) is particularly effective for individuals focused on acute heart failure symptom management. Research supports its use in this area [5][9].
Cardiovascular recovery and support
Relaxin-2 (Serelaxin) is particularly effective for individuals focused on cardiovascular recovery and support. Research supports its use in this area [2].
Hospital-based therapeutic interventions
Relaxin-2 (Serelaxin) is particularly effective for individuals focused on hospital-based therapeutic interventions. Research supports its use in this area [3][15].
Thymosin Beta-4
Post-Surgery Recovery
Accelerates healing of surgical wounds and reduces post-operative inflammation and scarring
Chronic Wound Management
Helps pressure ulcers, venous stasis ulcers, and other slow-healing wounds progress faster
Tissue Regeneration
Supports repair of damaged tissues from injury, burns, or degenerative conditions
Side effects
Relaxin-2 (Serelaxin)
Common
- Hypotension (low blood pressure) - most common
- Tachycardia (increased heart rate)
- Headache
- Nausea
- Dizziness
- Peripheral edema (swelling)
- Increased creatinine levels
- Hyperkalemia (high potassium)
- Syncope (fainting)
- Atrial fibrillation
- Blood pressure checks every 2-4 hours during infusion
- Kidney function (creatinine and eGFR)
- Electrolytes, particularly potassium
- Heart rate and cardiac rhythm
- Urine output
Serious
- Severe cardiovascular events
Thymosin Beta-4
Common
- Injection site redness
- Injection site swelling
Uncommon
- Temporary mild headache
- Mild bruising at injection site
- Transient fatigue
Serious
- Allergic reaction
Safety & evidence
Relaxin-2 (Serelaxin)
Evidence level
Limited human trials
FDA status
Research compound
Safety overview
Serelaxin (recombinant relaxin-2) completed Phase III heart failure trials with favorable safety profile and cardiovascular benefit signals. [3][5][9] Hypotension occurs in 20-25% of subjects requiring hemodynamic monitoring; no serious adverse events directly attributable to serelaxin beyond expected vasodilatory effects. [11] Flushing and headaches mild and transient. No serious immunogenicity despite being recombinant human peptide; repeat dosing shows consistent response [12].
Contraindications
- Severe hypotension or hemodynamic instability
- Pregnancy (despite relaxin's natural role)
- Acute kidney injury or severe renal dysfunction
- Recent myocardial infarction (within 7 days)
- Uncontrolled arrhythmias
Thymosin Beta-4
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
Thymosin Beta-4 is a naturally occurring peptide found in all cells and body fluids in the human body. Clinical trials have demonstrated excellent safety even at very high doses. IV studies showed doses up to 1260 mg were well tolerated with no serious adverse events.
Contraindications
- Active systemic infections
- Severe immunosuppression
- Hypersensitivity to thymosin or any component
- Pregnancy (insufficient safety data)
Which is right for you?
Choose Relaxin-2 (Serelaxin) if...
- Acute heart failure symptom management
- Cardiovascular recovery and support
- Hospital-based therapeutic interventions
Choose Thymosin Beta-4 if...
- Recovering from injuries or surgery
- Improving wound healing speed
- Reducing inflammation
- Minimizing scar formation