Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of SS-31 and Thymulin — mechanism, dosing, side effects, legal status, and pricing.
SS-31 (elamipretide) is a mitochondria-targeted tetrapeptide (D-Arg-Dmt-Lys-Phe-NH2) developed by Hazel Szeto (Cornell) and clinically advanced by Stealth BioTherapeutics. It concentrates in the inner mitochondrial membrane by binding cardiolipin. In September 2025, the FDA granted accelerated approval to elamipretide (brand name FORZINITY) as the first therapy for Barth syndrome — the first FDA-approved mitochondria-targeted drug. It remains investigational for other indications.
Thymulin is a zinc-dependent nonapeptide (pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) secreted by thymic epithelial cells, originally isolated by Bach and colleagues in the 1970s as 'facteur thymique sérique' (FTS). It is NOT the same compound as Thymalin (a Russian bovine thymus extract) or Thymosin alpha-1 (a separate 28-amino-acid thymic peptide). Thymulin is not FDA-approved; use is research/investigational only.
SS-31
Thymulin
Category
Legal Status
Mechanism
Dose Range
Route
Frequency
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
SS-31
Thymulin
COA corpus from Disclosed Labs — independently tested batches only.
SS-31
65
COAs
99.8%
Avg purity
12
Labs
Thymulin
5
COAs
99.5%
Avg purity
4
Labs
The original SS-peptide class was described by Zhao, Szeto and colleagues (J Biol Chem 2004, PMID 15178689), showing ~1000-fold concentration at the inner mitochondrial membrane and protection against oxidative cell death. Szeto's 2014 review (Br J Pharmacol, PMID 24117165) reframed the mechanism as cardiolipin-binding rather than antioxidant scavenging. The TAZPOWER trial (NCT03098797) in Barth syndrome, with its 168-week open-label extension (Thompson et al., Genet Med 2024, PMID 38602181), supported FDA accelerated approval of FORZINITY in September 2025 at 40 mg SubQ daily. The Phase 3 MMPOWER-3 trial in primary mitochondrial myopathy (Karaa et al., Neurology 2023, PMID 37268435) FAILED co-primary endpoints of 6-minute walk test and fatigue score, though a post-hoc nuclear-DNA subgroup showed improvement. Phase 2 ReCLAIM-2 in geographic atrophy missed primary endpoints but reduced ellipsoid-zone attenuation; a Phase 3 trial is ongoing. Earlier heart failure trials (PROGRESS-HF) showed only modest signals.
Key references
Bach and Dardenne originally characterized FTS/thymulin and its absolute zinc dependency (Bach & Dardenne, Med Oncol Tumor Pharmacother 1989, PMID 2657247). Prasad et al. (J Clin Invest 1988, PMID 3262625) showed that serum thymulin activity falls in human zinc deficiency and recovers with zinc supplementation. Mocchegiani et al. (Int J Immunopharmacol 1995, PMID 8582782) demonstrated partial reversal of thymic involution with zinc in aged mice. Dardenne & Pleau reviewed zinc-thymulin interactions (Met Based Drugs 1994, PMID 18476235). Safieh-Garabedian et al. (Br J Pharmacol 2002, PMID 12110619) reported analgesic/anti-inflammatory activity of a thymulin-related peptide in rats. There are NO large, modern RCTs of exogenous thymulin in humans; clinical use is experimental.
SS-31 (Recovery) and Thymulin (Immune) are in different categories and target different biological pathways. This is a common pattern in multi-compound research protocols. Researchers should monitor the biomarkers from both profiles and watch for interactions listed in each compound’s contraindications. Consult a licensed healthcare provider before combining any research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Dosing Notes
Half-life
Side Effects
Contraindications
Lab Testing
Key references
Disclosed Labs