SS-31 (Elamipretide) Dosage Protocol

Elamipretide (SS-31, Bendavia, MTP-131) is a water-soluble, mitochondria-targeted tetrapeptide (D-Arg-Dmt-Lys-Phe-NH2) that selectively binds cardiolipin on the inner mitochondrial membrane and has been evaluated in ten-plus clinical trials across Barth syndrome, primary mitochondrial myopathy, age-related macular degeneration, and heart failure with preserved ejection fraction [1,2]. The pivotal TAZPOWER trial in Barth syndrome (NCT03098797) delivered 40 mg subcutaneously once daily for 36 weeks, and the MMPOWER-3 trial in primary mitochondrial myopathy (NCT03323749) used the same 40 mg daily subcutaneous dose over 24 weeks [3,4]. Elamipretide has not received U.S. regulatory approval; the FDA rejected the Barth syndrome New Drug Application in 2024 and requested additional confirmatory trial data, leaving the peptide in advanced clinical development rather than on-market status [5].

How SS-31 Works: Mechanism of Action

In short: SS-31 accumulates in the inner mitochondrial membrane by binding cardiolipin, stabilizing the electron transport chain and reducing reactive oxygen species leak.

Elamipretide was developed by Hazel Szeto and Peter Schiller at Cornell University as a lead compound in the Szeto-Schiller ("SS") peptide series, engineered to selectively accumulate in the inner mitochondrial membrane in a membrane-potential-independent manner [1]. The defining structural feature is an alternating aromatic-cationic sequence that drives binding to cardiolipin, the signature phospholipid of the inner mitochondrial membrane.

The proposed mechanism involves stabilization of cardiolipin-cytochrome c interactions, preservation of supercomplex assembly in the electron transport chain, and reduction of electron leak and downstream reactive oxygen species generation [1,2]. In cardiolipin-deficient mitochondria (such as those in Barth syndrome, caused by TAZ gene mutations that impair cardiolipin remodeling), elamipretide has been reported to improve supercomplex stability and restore normal respiratory function in muscle biopsy samples [3,6].

Pharmacokinetic data support subcutaneous administration as the primary clinical route. Peak plasma concentrations occur approximately 1 to 2 hours after subcutaneous injection, with a plasma half-life of roughly 1.9 to 3.7 hours [2,7]. Elamipretide is not metabolized by cytochrome P450 enzymes and has low potential for pharmacokinetic drug-drug interactions at that pathway. Renal excretion is the dominant clearance route.

The clinical trial record is broad. Cardiovascular trials including EMBRACE-STEMI (reperfusion injury during acute myocardial infarction) and PROGRESS-HF (heart failure) produced mixed primary-endpoint results despite mechanistic plausibility [2,8]. Ophthalmology trials in geographic atrophy and dry age-related macular degeneration have been conducted. The ultra-rare mitochondrial myopathy and Barth syndrome programs have been the closest to regulatory approval, with MMPOWER-3 missing its primary endpoint but showing signals on secondary measures [4].

SS-31 Dose Ranges in the Peer-Reviewed Literature

In short: the trial-standard chronic dose is 40 mg SC once daily. IV dosing (0.25 mg/kg/hr × 1 hr) has been used in acute reperfusion studies.

Elamipretide clinical trials have converged on a relatively narrow daily dose range, reflecting pharmacokinetic and tolerability data rather than a broad therapeutic window exploration.

Four distinct dose tiers appear across the published program: low-dose IV for acute reperfusion (0.25 mg/kg/hr), low-dose subcutaneous maintenance (4 mg daily, used in some heart failure dose-ranging), mid-dose subcutaneous (20 mg daily in some earlier trials), and the current standard 40 mg daily subcutaneous. Chronic dosing at 80 mg daily has been explored in specific cardiac trials but has not become the standard for Barth syndrome or MMPOWER protocols.

Community self-report protocols for research-chem SS-31 are less extensive than for peptides like BPC-157 because elamipretide is not typically sold through non-prescription peptide channels in the same volume. Where community reports do exist, they describe daily subcutaneous doses in the 5 to 20 mg range for "mitochondrial health" indications — ranges that do not match the clinical protocols and are not supported by outcome data.

SS-31 Reconstitution: Math and Worked Examples

In short: 40 mg vial + 1 mL BAC water = 40 mg/mL. The trial dose is effectively the whole vial (1 mL SC).

Elamipretide in clinical trials has been supplied as a pre-filled syringe or a single-dose vial at 40 mg/mL concentration. Research-chem vials from peptide suppliers typically come as lyophilized 40 mg or 60 mg powder.

Standard reconstitution for a 40 mg vial:

• Vial: 40 mg SS-31 powder
• BAC water added: 1 mL
• Concentration: 40 mg/mL (40,000 µg/mL)
• 40 mg target dose (trial-standard): 40 mg ÷ 40 mg/mL = 1.0 mL = 100 units on a U-100 insulin syringe (essentially the entire vial volume)
• 20 mg target dose: 20 mg ÷ 40 mg/mL = 0.5 mL = 50 units

Alternative reconstitution for finer dose control (60 mg vial):

• Vial: 60 mg SS-31 powder
• BAC water added: 3 mL
• Concentration: 60 mg ÷ 3 mL = 20 mg/mL (20,000 µg/mL)
• 40 mg target dose: 40 mg ÷ 20 mg/mL = 2.0 mL (requires a larger syringe or split administration)
• 20 mg target dose: 20 mg ÷ 20 mg/mL = 1.0 mL = 100 units on a U-100 insulin syringe

A unique feature of elamipretide is that the trial-standard daily dose (40 mg) is relatively large on a per-injection basis compared to most peptides on the market (which dose in the microgram range). This means that a 5 mg or 10 mg vial — a common size for other peptides — is insufficient for a single trial-standard dose. Users sourcing research-chem product must confirm vial size before calculating cycle length.

How SS-31 Is Administered

In short: subcutaneous once daily for chronic mitochondrial indications. IV used only in acute cardiac research.

The dominant clinical route is subcutaneous injection. The TAZPOWER and MMPOWER-3 trials both used once-daily subcutaneous administration in the abdomen, anterior thigh, or upper arm [3,4]. Site rotation is standard clinical practice, with the abdomen (avoiding a 2-inch radius around the umbilicus) as the preferred site in the trial protocols. Injection-site reactions are the most commonly reported adverse event and are discussed in the side-effect section.

Intravenous administration has been used in reperfusion and acute cardiac trials as a short infusion over 1 hour [8]. IV is not the maintenance route for chronic mitochondrial indications.

Intravitreal administration has been studied for ocular indications in preclinical work; clinical ophthalmology trials have generally used subcutaneous systemic dosing rather than intravitreal injection.

Timing relative to meals is not critical. Timing relative to time of day has not been systematically varied; trial protocols have typically instructed morning administration. The 1.9- to 3.7-hour plasma half-life suggests that once-daily dosing provides intermittent rather than continuous plasma exposure; the drug's accumulation in mitochondrial membranes is thought to provide effective tissue-level coverage despite the short plasma half-life [2,7].

Syringe selection for 40 mg doses at 40 mg/mL concentration is a 1 mL syringe (not an insulin syringe, which tops out at 1 mL but has finer gauge and shorter needle than ideal for 1 mL subcutaneous administration in some anatomical sites). A 29 or 30 gauge, 1/2 inch needle is appropriate.

SS-31 Cycle Structure and Protocol Duration

In short: continuous daily dosing for the duration of the indication. Open-label extensions have run multi-year in responders.

Registered clinical trials have used continuous daily dosing for durations of 24 to 48 weeks [3,4,9]. The open-label extension phases of TAZPOWER and MMPOWER-3 extended treatment to multi-year follow-up in responders. There is no evidence for intermittent or pulsed dosing in the registered trial program; the mitochondrial-membrane accumulation mechanism argues for continuous rather than cyclic dosing in chronic conditions.

Tolerance or tachyphylaxis has not been documented in the published clinical trial record. The open-label extension data from Barth syndrome patients suggest that functional benefits, where observed, are maintained over extended continuous dosing rather than declining with time [3].

For community self-experimenters, cycle-design data are thin because the cleanest clinical data come from ultra-rare disease populations and are not directly transferable to healthy subjects or to non-mitochondrial indications. Extrapolation from a Barth syndrome dose to a general "mitochondrial health" use case assumes that the cardiolipin-binding mechanism provides a similar benefit in healthy mitochondria to the one it provides in cardiolipin-deficient ones, and this assumption has not been tested in a controlled trial.

Cost is a practical consideration not often discussed in peptide dosing literature but relevant for elamipretide specifically: the trial-standard 40 mg daily subcutaneous dose consumes substantially more peptide mass per month than microgram-scale peptides, making month-over-month supply cost materially higher even at research-chemical pricing. A 40 mg daily dose requires 1.2 grams of peptide per 30 days, versus milligrams or fractions of a milligram for many other peptides covered in this series.

SS-31 Side Effects and Safety Profile

In short: injection-site reactions dominate. Systemic adverse events uncommon; serious adverse events rare in chronic SC dosing.

Injection-site reactions are the most common adverse event across the elamipretide trial database. In MMPOWER-3, injection-site erythema, induration, and pruritus occurred in a majority of subjects and were generally mild to moderate [4]. The reaction pattern is consistent with local immune response to peptide injection rather than systemic allergy.

Other reported adverse events include headache, nausea, mild gastrointestinal discomfort, and transient hypertension during IV infusion [2,7,8]. Serious adverse events in the chronic subcutaneous trials have been uncommon and generally unrelated to the study drug.

Contraindications in the clinical trial protocols have included known hypersensitivity, pregnancy, lactation, severe renal impairment (given renal clearance), and active malignancy. Drug interactions are theoretically limited because elamipretide is not a CYP substrate or inhibitor at therapeutic concentrations.

A specific cardiovascular consideration: elamipretide's reperfusion studies used IV dosing and found mixed primary-endpoint results, with some signals of blood-pressure change during infusion [8]. The subcutaneous-maintenance dosing pattern does not reproduce this acute IV exposure and has not been associated with the same hemodynamic effects.

Long-term safety data in the Barth syndrome open-label extension — which represents some of the longest continuous elamipretide exposure in the published record — have been consistent with the shorter-term safety profile, with injection-site reactions the dominant persistent adverse event and no new safety signals emerging over multi-year treatment [3]. Cumulative dose toxicity concerns have not been raised in the published record to date, though the aggregate treated population remains small given the ultra-rare target indications.

Special-population data are limited to the studied indications. Pediatric Barth syndrome patients as young as 11 to 12 years have been enrolled in TAZPOWER, establishing pediatric safety data in the adolescent range; younger pediatric exposure has not been published. Geriatric data come from the heart failure and geographic atrophy trials and support adult dosing without age-specific adjustment [2,9]. Pregnancy and lactation data are absent from the published record.

SS-31 Vendor Ratings: Who Publishes Lab Data at ≥99% Purity?

TriedRx aggregates publicly available third-party lab reports, identity-confirmation data, and reputation signals for vendors distributing SS-31 (elamipretide). Because elamipretide contains D-amino acids, stereochemical confirmation — not just mass and purity — is a meaningful quality question. We compile what vendors publish and what independent testing groups have reported.

See all SS-31 vendors we've rated →

Related: SS-31 Research Profile and Vendor Rankings

For the full research background on elamipretide, including the Szeto-Schiller peptide series, the cardiolipin-binding mechanism, and the Barth syndrome and primary mitochondrial myopathy clinical history, see the TriedRx SS-31 peptide profile. The profile covers the FDA 2024 Complete Response Letter, the ongoing confirmatory trial design, and the cardiovascular program results.

References

1. Szeto HH. First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol. 2014;171(8):2029-2050. PMID: 24117165.
2. Daubert MA, Yow E, Dunn G, et al. Novel mitochondria-targeting peptide in heart failure treatment: a randomized, placebo-controlled trial of elamipretide. Circ Heart Fail. 2017;10(12):e004389. PMID: 29217757.
3. Reid Thompson W, Hornby B, Manuel R, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism. Genet Med. 2021;23(3):471-478. PMID: 33077847. NCT03098797.
4. Karaa A, Haas R, Goldstein A, et al. Randomized dose-escalation trial of elamipretide in adults with primary mitochondrial myopathy. Neurology. 2018;90(14):e1212-e1221. PMID: 29500292. NCT03323749.
5. Stealth BioTherapeutics. Complete Response Letter for elamipretide NDA in Barth syndrome. Company filings 2024. (regulatory correspondence)
6. Allen ME, Pennington ER, Perry JB, et al. The cardiolipin-binding peptide elamipretide mitigates fragmentation of cristae networks following cardiac ischemia reperfusion. Commun Biol. 2020;3(1):389. PMID: 32680997.
7. Stealth BioTherapeutics. Phase 1 safety and pharmacokinetics of elamipretide in healthy subjects. NCT01572909-linked publication. 2014. PMID: 24976725.
8. Gibson CM, Giugliano RP, Kloner RA, et al. EMBRACE STEMI study: a phase 2a trial to evaluate the safety, tolerability, and efficacy of intravenous MTP-131 on reperfusion injury in patients undergoing primary percutaneous coronary intervention. Eur Heart J. 2016;37(16):1296-1303. PMID: 26586787. NCT01572909.
9. Wong WT, Allikmets R, Hubschman JP, et al. ReCLAIM-2: phase 2 randomized trial of elamipretide in dry age-related macular degeneration with geographic atrophy. Ophthalmol Sci. 2023;3(2):100260. NCT03891875. DOI: 10.1016/j.xops.2022.100260.