SS-31 (Elamipretide)
Also known as: Elamipretide · Bendavia · MTP-131
A mitochondrially-targeted tetrapeptide that binds cardiolipin on the inner mitochondrial membrane, studied for mitochondrial-dysfunction diseases and emerging cognitive-ageing research applications.
SS-31 (elamipretide) is a mitochondrially-targeted tetrapeptide that binds cardiolipin on the inner mitochondrial membrane; Phase III trials completed in mitochondrial diseases with challenging regulatory pathway.
Evidence tier: B — clinical evidence (trials or approved use in some jurisdictions)
- Category
- Neuroprotection
- Half-life
- Short plasma half-life; mitochondrial-retention persists
Section 1
Overview
SS-31 (elamipretide) is a synthetic tetrapeptide — D-Arg-dimethylTyr-Lys-Phe — engineered to selectively accumulate on the inner mitochondrial membrane by binding directly to cardiolipin, the mitochondrial-specific phospholipid. The peptide's positive charge concentration and hydrophobic residues drive selective mitochondrial targeting rather than accumulation in cytoplasm or other cellular compartments. This mitochondrial targeting is the compound's mechanistic hallmark.
SS-31 is developed by Stealth BioTherapeutics primarily for mitochondrial-dysfunction diseases including primary mitochondrial myopathies, Barth syndrome, and mitochondrial-related cardiovascular conditions. The clinical programme has been substantial, with multiple Phase II and Phase III trials completed, though regulatory approval has been challenging — the FDA declined the initial Barth syndrome NDA in 2020, and the compound's approval status remains in flux.
The cognitive-research relevance emerges from the observation that mitochondrial dysfunction is a shared upstream feature of Alzheimer's disease, Parkinson's disease, age-related cognitive decline, and multiple neurodegenerative processes. If a peptide can selectively restore mitochondrial function in stressed neurons, it becomes a candidate cognitive-therapeutic tool that operates on a mechanism distinct from the neurotrophin-induction pathway that dominates the cognitive-peptide field.
Section 2
Discovery & History
- Developed at Cornell University by the Szeto laboratory in the 2000s as part of a systematic effort to design mitochondrially-targeted small molecules for oxidative-stress and mitochondrial-dysfunction diseases.
- Licensed to Stealth BioTherapeutics for clinical development, with subsequent Phase II and Phase III trials across multiple mitochondrial-dysfunction indications.
- Received FDA fast-track and orphan drug designations for Barth syndrome and other rare mitochondrial conditions.
- FDA declined the initial Barth syndrome NDA in 2020 based on the trial data package; the compound's regulatory pathway has remained challenging in subsequent submissions.
- Cognitive-ageing research applications have emerged from academic groups extending the mitochondrial-mechanism angle into Alzheimer's model systems and age-related cognitive decline research.
Section 3
Mechanism of Action
- 1Selective binding to cardiolipin on the inner mitochondrial membrane — the mechanism-of-action hallmark and the property that distinguishes SS-31 from other mitochondrial-relevant compounds; the peptide's positive charge concentration drives selective accumulation on the mitochondrial-specific cardiolipin phospholipid rather than other cellular membranes.
- 2Preservation of mitochondrial membrane potential under stress — reduced membrane depolarisation, preserved electron transport chain function, and reduced mitochondrial permeability transition pore opening in stressed preparations across multiple cell types and injury models.
- 3Reduction of mitochondrial reactive oxygen species production — the cardiolipin-binding mechanism protects cardiolipin itself from peroxidative modification, which in turn preserves electron transport chain efficiency (particularly Complex I and IV activity) and reduces ROS generation at the source rather than downstream ROS scavenging.
- 4Preservation of ATP synthesis under stress conditions — measurable maintenance of cellular ATP levels in ischaemic, oxidative-stress, and disease-model preparations, providing the metabolic substrate for cellular survival and function under insult.
- 5Anti-apoptotic effects via preservation of mitochondrial membrane integrity and reduced cytochrome-c release, providing survival support to stressed cells and blocking the mitochondrial arm of the apoptotic cascade upstream of caspase-9 activation.
- 6Reported neuroprotective effects in preclinical models of cerebral ischaemia, Alzheimer's disease, Parkinson's disease, and traumatic brain injury — cognitive-ageing research applications extending from the mitochondrial-mechanism scaffold and providing empirical support for the cognitive-relevance research angle.
- 7Effects on mitochondrial biogenesis and mitochondrial-quality-control pathways at the cellular level, extending the pharmacology beyond acute preservation of existing mitochondria into support of the cellular mitochondrial-maintenance machinery.
- 8Reported effects on ischaemia-reperfusion injury outcomes in cardiovascular and renal tissue models, providing evidence that the mitochondrial-preservation mechanism operates across tissue systems rather than being CNS-specific.
Section 4
Researched Benefits
Findings reported in the published preclinical and clinical literature. Effects in research contexts do not constitute claims of therapeutic benefit in humans.
- 1Selective mitochondrial targeting providing a distinctive mechanism-of-action angle unavailable to any other peptide on this site — a mechanistically differentiated research tool.
- 2Preserved mitochondrial function under oxidative, ischaemic, and disease-related stress across multiple tissue systems, providing broad research applicability.
- 3Substantial preclinical evidence base in mitochondrial-dysfunction disease models — cardiovascular, muscular, and neurological — with reproducible findings across multiple independent research groups.
- 4Clinical trial evidence in primary mitochondrial myopathies and Barth syndrome — one of the more clinically-developed peptides on this reference, with Phase III trial data available for interpretation.
- 5Emerging cognitive-ageing research applications extending from the mitochondrial-mechanism angle — mitochondrial dysfunction is a shared upstream feature of multiple neurodegenerative processes.
- 6Substantial acute safety database from the completed clinical trials at doses studied — the Stealth BioTherapeutics-sponsored trials generated multi-year safety data at 40 mg/day dosing.
- 7Reported effects on ischaemia-reperfusion injury outcomes providing cardiovascular-adjacent research applications extending the mitochondrial-preservation mechanism beyond pure cognitive applications into broader tissue-injury research contexts.
Section 5
Theoretical Dosing & Protocols
| Route | Dosage | Frequency | Duration |
|---|---|---|---|
| Subcutaneous injection (research and clinical trials) | 40 mg subcutaneously once daily in the primary clinical trial programme; some earlier protocols used lower doses (10–20 mg range) during pharmacokinetic characterisation | Once daily in the licensed-indication trial protocols | Long-term chronic dosing in the licensed-indication trials (24+ months); shorter research protocols for mechanistic characterisation range from weeks to months |
Note: Not approved for cognitive indications; the cognitive-ageing research applications are entirely investigational, and cognitive-endpoint dose selection should be informed by the mitochondrial-myopathy trial dose range as the reference point given the shared underlying mitochondrial-preservation mechanism.
Section 6
Administration Routes
- Subcutaneous injection — the primary route in the clinical trial programme and the practical route for reproducible pharmacokinetic characterisation.
- Intravenous administration is used in acute-injury research contexts.
- The peptide is not orally viable — the tetrapeptide is efficiently degraded by gastrointestinal proteases.
- Intranasal administration has been explored preclinically but is not the standard clinical route.
Section 7
Safety Profile
Commonly reported
- · Injection-site reactions with subcutaneous administration — the most common tolerability signal in the completed clinical trials.
- · Mild transient effects on blood pressure reported at low frequency.
- · Occasional headache or fatigue during dose titration.
- · Well-tolerated in the completed clinical-trial evidence base at the studied doses.
Rare / theoretical
- · Long-term safety data beyond the clinical-trial evidence base is limited; multi-year chronic-use safety in cognitive-endpoint applications is not characterised.
- · Theoretical mitochondrial-effect concerns in tissues where mitochondrial-turnover regulation is finely balanced — no documented clinical events but a plausible mechanism-based consideration.
- · Rare hypersensitivity reactions — theoretical concern based on peptide chemistry.
- · No documented dependence, tolerance, or withdrawal phenomena in the clinical-trial evidence base.
- · Theoretical interaction with mitochondrially-active pharmaceuticals or supplements should be evaluated in research protocols involving co-administration.
Contraindications
- · Not authorised for human use in the UK — supply for human consumption is prohibited under the Human Medicines Regulations 2012.
- · Pregnancy and lactation — insufficient controlled data.
- · Known hypersensitivity to peptide components.
- · Severe mitochondrial-disease pathology outside the specific licensed-development indications should be evaluated for suitability before research use.
Section 8
UK & EU Regulatory Context
United Kingdom
Not a licensed medicine in the UK. Research chemical only.
European Union
Not approved by the EMA. Development-programme evaluations ongoing in specific indications.
Section 9
Clinical Studies Summary
SS-31 in primary mitochondrial myopathies — Phase II/III trials
Multiple randomised controlled trials evaluating SS-31 in primary mitochondrial myopathy patient populations across the Stealth BioTherapeutics-sponsored clinical development programme, reporting mixed but generally positive effects on functional-endpoint measures (six-minute walk distance, muscle function scoring) and biomarker outcomes. The largest clinical evidence base for the compound and the basis for the FDA submission pathway.
SS-31 in Barth syndrome
Clinical trial programme in Barth syndrome — a rare X-linked cardiolipin-metabolism disorder where the mechanism-of-action rationale for cibinetide is most direct — reporting functional improvements over long-term dosing. Formed the basis of the initial FDA submission (declined in 2020 based on the trial data package) and the ongoing regulatory-pathway development following the initial NDA decision.
SS-31 in Alzheimer's model systems
Preclinical characterisation of SS-31 effects in APP/PS1 transgenic Alzheimer's disease mouse models, reporting preserved cognitive performance on hippocampus-dependent learning tasks, reduced amyloid-beta accumulation, and preserved hippocampal mitochondrial function versus vehicle controls. Provides the extension of the mitochondrial-mechanism into AD-relevant research and the mechanistic scaffold for the cognitive-ageing research applications.
SS-31 mechanism — cardiolipin binding and mitochondrial protection
Foundational biochemistry characterisation of SS-31's selective cardiolipin binding on the inner mitochondrial membrane using lipid-binding assays, molecular dynamics simulations, and cellular localisation studies. Provides the molecular scaffold for the compound's selective mitochondrial targeting and its distinctive mechanism-of-action profile that distinguishes it from other mitochondrially-relevant peptides.
SS-31 in cognitive-ageing rodent models
Behavioural pharmacology characterisation of SS-31's effects in aged rodent cognitive-decline models, reporting preserved cognitive performance on hippocampus-dependent learning tasks alongside preserved hippocampal mitochondrial function and reduced age-related oxidative-stress markers in treated cohorts. Directly supports the cognitive-ageing research application angle.
Section 10
Frequently Asked Questions
Section 10a
Practical Research Guidance
Cycle guidance
Reconstitution & storage
UK sourcing notes
Section 11
Sourcing for Laboratory Research
Sourcing SS-31 (Elamipretide) for laboratory research
Researchers in the United Kingdom and elsewhere typically obtain SS-31 (Elamipretide) from specialist research-chemical suppliers. Purity, third-party testing, and supplier transparency are the principal differentiators worth evaluating before placing an order. The two suppliers below are commonly referenced in UK research contexts.
Reminder: research peptides are sold strictly for in vitro and preclinical laboratory purposes. Importation or supply for human consumption is not permitted under UK medicines legislation.