SS-31, also called elamipretide, is a mitochondria-targeting tetrapeptide that localises to the inner mitochondrial membrane and binds cardiolipin. Unlike most research peptides it has been studied in human clinical trials, and in September 2025 the US Food and Drug Administration granted it accelerated approval for one rare mitochondrial disease, Barth syndrome, on an intermediate endpoint and subject to a confirmatory trial. Its approved form is a ready-to-use solution for subcutaneous injection.
By Tessaro Pty Ltd, the maker of Pepti · Last reviewed
This page is a reference, not a protocol. It sets out what SS-31 is, what the human and laboratory evidence actually shows, what its approval does and does not mean, and why — despite being an approved injectable — the FDA label we reviewed gives no elimination half-life to build a decay curve from. It contains no dose figures and no schedule, and a section further down explains why that is deliberate rather than an omission.
| Property | Value |
|---|---|
| Class / type | Mitochondria-targeting tetrapeptide — binds cardiolipin in the inner mitochondrial membrane |
| Evidence base | Human clinical trials; accelerated approval for one rare-disease indication on an intermediate endpoint. Supporting mechanism work is largely cell and animal |
| Half-life | The FDA label we reviewed (DailyMed, Oct 2026) does not state an elimination half-life. |
| Regulatory status | Accelerated approval in the United States (2025) for Barth syndrome, continued approval contingent on a confirmatory trial; not approved for any other use |
SS-31 (elamipretide) is a mitochondria-targeting tetrapeptide. Its mechanism is described in the US label as a mitochondrial cardiolipin binder that localises to the inner mitochondrial membrane and improves mitochondrial morphology and function (DailyMed). Cardiolipin is a lipid specific to that inner membrane, and binding it is the proposed basis for the compound's effect on mitochondrial energy production.
Human evidence. SS-31 is unusual among research peptides in having a human clinical record, including studies in Barth syndrome. On 19 September 2025 the US Food and Drug Administration (FDA) granted it accelerated approval — described by the agency as the first treatment for Barth syndrome — to improve muscle strength in adults and children with that disorder (FDA; DailyMed). The approval rests on an intermediate clinical endpoint, an improvement in knee extensor muscle strength, and the label states that continued approval may be contingent on verification of benefit in a confirmatory trial (DailyMed).
How to read that record. Two things matter. An accelerated approval on an intermediate endpoint is a conditional result, not a final one: the confirmatory trial is what determines whether the benefit holds. And the approval covers one rare genetic disorder only — it is not a general-purpose endorsement, and the wider claims circulating about SS-31 for other uses rest largely on cell and animal work, not approved human outcomes (DailyMed).
The FDA label we reviewed (DailyMed, Oct 2026) does not state an elimination half-life. It reports that peak concentrations are reached within the first hour of a subcutaneous injection (a time to peak of roughly 0.5 to 1 hour), that absolute bioavailability is about 92 percent, and that the compound and its two metabolites are recovered in the urine — but it gives no elimination or terminal half-life (DailyMed). A half-life is the time taken for half of what is present to clear; without a stated value, there is nothing to anchor a decay curve to.
So even though SS-31 is an approved injectable, the honest position on decay is the same as for an unstudied peptide: if a specific value has been given to you for the material you hold, the half-life decay calculator can work from the number you enter; absent that, the record is a dated history of entries, not a modelled curve drawn from a guessed number that looks precise and tells you nothing.
The approved form of SS-31 is, per the US label, a ready-to-use sterile solution in single-patient-use vials for subcutaneous injection — already liquid, and not reconstituted (DailyMed). The label directs that it be stored refrigerated and not frozen, and that an opened vial may be kept refrigerated or at room temperature, then discarded after the number of days the label specifies (DailyMed).
Material outside approved supply may instead be a lyophilised powder — a different physical product, inert until a diluent is added and carrying none of the label's storage guarantees. The record-keeping point holds either way: note the form you have, the date you opened or reconstituted it, and the conditions you kept it in.
Pepti is a record-keeping and measurement tool, and SS-31 is logged like anything else: each administration on a dated timeline, so the history is written down rather than remembered.
If your material is the approved ready-to-use solution, there is nothing to mix: the record is the figure you have, the date and the site. If instead you hold a lyophilised powder, the reconstitution calculator converts the figures you already have into a draw volume and a count of doses per vial. The arithmetic is held as variables, never as numbers we supply: the concentration is the amount in the vial divided by the volume of water you add; the draw volume is your figure divided by that concentration; and the syringe units are the draw volume multiplied by one hundred.
Because an injected compound should move around the body rather than landing in the same spot, the injection site rotation guide sets out how to rotate sites systematically, and Pepti keeps a 12-site sequence so the next injection goes somewhere new. And because the FDA label we reviewed states no elimination half-life for SS-31, the half-life decay calculator is meaningful only if you enter a value you have been given for your own material — it will not supply one.
SS-31 is approved for one rare disorder, and the dosing for that indication belongs in the approved label and with the clinician directing that care — not on a general reference page. For every other use there is no approved label at all: no authorised amount, no approved schedule, and no clinician-facing guidance outside a trial protocol. Any figure published as a “typical” amount for those other uses is not drawn from an approved source, because none exists.
Pepti is a measurement and record-keeping tool. It converts a figure you already have into a draw volume and syringe units, tracks what is left in each vial, and remembers where the last injection went. It does not supply the figure, and it will not, for this compound or any other. The figure belongs to you and whoever directs your use. The arithmetic is what we are for.
A record worth keeping comes down to the few fields that stay useful months later.
SS-31, also called elamipretide, is a mitochondria-targeting tetrapeptide. It localises to the inner mitochondrial membrane and binds cardiolipin, a lipid found there, which is the basis proposed for its effects on mitochondrial function. It has been studied in human clinical trials, which is unusual for a research peptide.
In part. In September 2025 the US Food and Drug Administration granted elamipretide accelerated approval to improve muscle strength in people with Barth syndrome, a rare mitochondrial disorder, based on an intermediate endpoint and subject to a confirmatory trial. It is not approved for any other condition, and most other uses discussed online rest on cell and animal data rather than approved human outcomes.
The FDA label we reviewed (DailyMed, Oct 2026) does not state an elimination half-life. It reports that the drug reaches peak levels within about an hour of a subcutaneous injection and is cleared in the urine. Without a stated value you cannot plot a decay curve, so a half-life calculator is only useful with a number you have been given for your own material.
Yes. SS-31 and elamipretide are two names for the same tetrapeptide. SS-31 is the original research designation; elamipretide is the international non-proprietary name used in clinical trials and in its approved form. This page uses SS-31 and elamipretide only, and avoids trade names.
No. Pepti supplies no amount figures for SS-31 or anything else. It records the figure you already have from whoever directs your use, converts it into a draw volume and syringe units, tracks what is left in each vial, and keeps the site sequence. The arithmetic is ours; the figure is not.
This page is a reference on published evidence and record-keeping. It does not recommend SS-31 or any other substance, and it provides no amount, no titration figure, and no schedule. SS-31 is approved only for one rare disorder; for any other use it is investigational.
The Pepti peptide tracker for iPhone keeps the dated log, the site sequence, the vial count and your own outcome notes in one place.
Not medical advice. Pepti is a record-keeping and measurement tool, not a medical device.
Get Pepti on the App Store