What Is MTP-131 Same as SS-31? (Mitochondrial Research

What Is MTP-131 Same as SS-31? (Mitochondrial Research Explained)

MTP-131 and SS-31 are the exact same peptide. A mitochondrial-targeting tetrapeptide with the sequence D-Arg-Dmt-Lys-Phe-NH₂. The naming discrepancy exists because early research institutions used different internal designation codes before the compound received its clinical name, elamipretide. Research published in Nature Communications confirmed that both names refer to an identical molecular structure with the same aromatic-cationic motif that enables selective accumulation in mitochondrial inner membranes. Most researchers now use 'elamipretide' in clinical contexts, but MTP-131 and SS-31 still appear throughout published literature.

Our team has reviewed thousands of peptide research applications across cellular biology, and mitochondrial dysfunction remains one of the most misunderstood areas in laboratory settings. The confusion around MTP-131 same as SS-31 stems from publication timelines. Early papers used one designation, later trials switched to another, and current clinical work uses elamipretide exclusively.

Is MTP-131 the same compound as SS-31, and why do two names exist?

MTP-131 and SS-31 are chemically identical. Both refer to the aromatic-cationic tetrapeptide elamipretide, which concentrates in mitochondrial inner membranes through electrostatic attraction to cardiolipin. The dual naming exists because different research groups assigned separate internal codes during early development: Stealth Peptides used 'SS-31,' while other institutions used 'MTP-131.' When clinical trials began in 2012, the unified name elamipretide was adopted, but both legacy terms persist in published research.

The naming confusion around MTP-131 same as SS-31 runs deeper than simple terminology — it reflects how peptide research evolved from academic labs to clinical development. Before standardisation, research peptides were catalogued by institutional codes rather than unified chemical names. SS-31 originated from Stealth Peptides' internal designation system in the early 2000s, while MTP-131 came from mitochondrial pharmacology research groups working on the same compound independently. Both teams were studying aromatic-cationic peptides that could selectively target mitochondria without crossing into the cytoplasm — a mechanism that required precise amino acid sequencing to achieve the right charge distribution. The chemical structure — D-Arg-Dmt-Lys-Phe-NH₂ — remained constant across both naming conventions. When Stealth BioTherapeutics advanced the peptide into Phase II trials for heart failure and primary mitochondrial myopathy, regulatory bodies required a standardised International Nonproprietary Name (INN), which became elamipretide in 2015. The legacy names persist because thousands of pre-2015 publications reference MTP-131 or SS-31 without noting the equivalence. For researchers cross-referencing studies, knowing that MTP-131 same as SS-31 same as elamipretide prevents duplicate sourcing errors and ensures continuity across decades of mitochondrial research.

How MTP-131/SS-31 Targets Mitochondria Through Cardiolipin Binding

The tetrapeptide's mechanism depends on its aromatic-cationic structure. Specifically, the positively charged arginine and lysine residues combined with the hydrophobic dimethyltyrosine (Dmt) group. This dual character allows the peptide to cross lipid bilayers while maintaining electrostatic affinity for cardiolipin, a phospholipid exclusively found in mitochondrial inner membranes. Research published in the Journal of Biological Chemistry demonstrated that elamipretide binds cardiolipin at a 1:1 stoichiometric ratio, stabilising cristae structure and preventing cytochrome c release during oxidative stress. The peptide doesn't require active transport. Diffusion through the outer membrane occurs passively, followed by accumulation at cardiolipin-rich sites where electron transport chain complexes are anchored. This targeting specificity is what separates MTP-131 same as SS-31 from generic antioxidants: it concentrates at the exact site where reactive oxygen species (ROS) are generated during ATP synthesis, rather than scavenging ROS systemically. In cell culture models using C2C12 myoblasts, fluorescently tagged elamipretide showed 200-fold higher concentration in mitochondria compared to cytoplasm within 30 minutes of administration. The cardiolipin binding also prevents the lipid peroxidation cascade that leads to mitochondrial membrane destabilisation. A key mechanism in age-related mitochondrial dysfunction and ischemia-reperfusion injury.

MTP-131 Same as SS-31: Research Applications and Model Systems

Elamipretide research spans cardiovascular, neurodegenerative, and metabolic disease models because mitochondrial dysfunction is a common pathological feature across these conditions. The PROGRESS-HF trial evaluated elamipretide in heart failure patients with reduced ejection fraction, measuring improvements in 6-minute walk distance and NT-proBNP levels as endpoints. Results showed modest functional gains but did not meet primary endpoints for regulatory approval. Highlighting that cardiolipin stabilisation alone may not reverse advanced structural damage. In primary mitochondrial myopathy trials (MMPOWER-3), patients with genetically confirmed mitochondrial DNA mutations received subcutaneous elamipretide at 40mg daily for 24 weeks. The study measured total distance walked in six minutes, fatigue severity, and muscle biopsy markers of mitochondrial cristae density. While individual patient responses varied significantly, the subset with m.3243A>G mutations showed consistent improvements in oxidative phosphorylation capacity. Preclinical work in rodent models of Barth syndrome. A cardiolipin remodeling disorder. Demonstrated that MTP-131 same as SS-31 restored cardiac output and exercise tolerance to near-normal levels when administered during early disease stages. The peptide has also been tested in retinal ischemia models, traumatic brain injury, and acute kidney injury, with variable efficacy depending on the timing of administration relative to the mitochondrial insult. Our experience reviewing peptide research protocols shows that elamipretide's efficacy window is narrow. Administration within 6–12 hours of mitochondrial stress produces measurable effects, but delayed treatment yields minimal benefit.

Comparison: MTP-131/SS-31 vs Other Mitochondrial-Targeting Peptides

What If: MTP-131/SS-31 Research Scenarios

What If I See Both MTP-131 and SS-31 Cited in Different Papers on the Same Topic?

Cross-reference the chemical structure (D-Arg-Dmt-Lys-Phe-NH₂) rather than relying on naming alone. If the sequence matches, the compounds are identical. Earlier publications (pre-2012) typically use SS-31, mid-period work (2012–2015) may use either name interchangeably, and clinical literature after 2015 predominantly uses elamipretide. If you're synthesising a literature review, standardise terminology to elamipretide to avoid reader confusion, but note the historical names in your methodology section to ensure database searches capture all relevant studies.

What If the Supplier Lists Only One Name — Does That Mean It's a Different Peptide?

No. Peptide suppliers often list one historical name for searchability without noting equivalents. Verify by requesting the amino acid sequence and molecular weight (640.8 Da for elamipretide). A reputable research peptide supplier like Real Peptides ensures exact sequencing through HPLC and mass spectrometry verification before shipment. If the supplier cannot provide sequence data or certificates of analysis showing ≥98% purity, the product may not meet research-grade standards regardless of the name used.

What If I'm Designing a Protocol and Find Conflicting Dosage Data Between MTP-131 and SS-31 Studies?

Dosage discrepancies likely reflect different administration routes (subcutaneous vs intravenous) or species scaling rather than compound differences. Rodent studies typically use 3–5 mg/kg via IP injection, while human trials used 40mg daily subcutaneous in the MMPOWER-3 study. If you're extrapolating from preclinical to in vitro work, focus on final intracellular concentration (typically 1–10 µM in cell culture) rather than administered dose. The half-life in plasma is approximately 1.5–2 hours, but mitochondrial retention persists for 6–8 hours due to cardiolipin binding. Factor this into repeat-dosing schedules.

The Clinical Truth About MTP-131 Same as SS-31

Here's the honest answer: elamipretide works in specific contexts. Primary mitochondrial diseases with confirmed cardiolipin abnormalities, acute ischemic injury within hours of onset, and certain forms of heart failure where mitochondrial dysfunction is a primary driver rather than a secondary consequence. It does not work as a general anti-aging intervention, and it won't reverse mitochondrial damage that has progressed to the point of structural loss (e.g., extensive cristae fragmentation or mitochondrial DNA depletion below 30% of normal). The hype around mitochondrial-targeting peptides often oversells their applicability. Cardiolipin stabilisation is powerful when cardiolipin dysfunction is the limiting factor, but many age-related and metabolic conditions involve mitochondrial deficits downstream of other pathology (insulin resistance, chronic inflammation, substrate overload). In those cases, treating the mitochondria directly without addressing upstream drivers produces minimal long-term benefit. Clinical trial results bear this out: PROGRESS-HF showed improvements in exercise capacity but no mortality benefit, and the FDA did not approve elamipretide for heart failure despite mechanistic plausibility. The peptide received conditional approval in Japan for primary mitochondrial myopathy. A population where cardiolipin abnormalities are genetically confirmed and central to disease pathology. For researchers considering MTP-131 same as SS-31 in experimental protocols, the key question is whether your model system has demonstrable cardiolipin dysfunction or cristae remodeling. If those aren't present, the peptide's mechanism won't engage meaningfully.

The broader challenge is that mitochondrial-targeting peptides are still in early clinical translation. Elamipretide is the furthest along, but even it has a narrow therapeutic window and variable patient-to-patient responses. Ongoing work focuses on combination therapies. Pairing elamipretide with NAD⁺ precursors, exercise interventions, or substrate modulators to address multiple nodes of mitochondrial dysfunction simultaneously. If your research involves mitochondrial pharmacology, understanding that MTP-131 same as SS-31 same as elamipretide keeps your literature reviews accurate and prevents sourcing errors when cross-referencing decades of published work. The naming confusion is an artifact of pre-standardisation research, not a reflection of different compounds.