Peptifact

SS-31 Dosage: The Molecule Sold as a Research Peptide Now Has an FDA Label

SS-31 is elamipretide. In 2025 it was approved as FORZINITY at 40 mg once daily — so for the first time a compound in this catalogue has a labelled dose. We read the label and compared it with what research pages state.

Robert F · Edited by Caroline S · Published 2026-09-11

Illustration: A clear glass vial with white powder sits next to an open precision scale on a grey lab bench.
Illustration

Almost every page in this catalogue reports the same shape of finding: no label, no registration, a figure that circulates without a source. SS-31 has become the exception. In 2025 the molecule was approved by the FDA, and there is now a dose for it that a regulator has read.

That does not make the research-market figures correct. It makes them checkable for the first time. This page reports what the label states and does not recommend anything. Our page on the questions we ask of any dosage figure sets out what separates a label figure from a convention. How brands appear on this site is set out on our disclosure page.

One molecule, four names

SS-31 comes from the Szeto-Schiller series of mitochondria-targeting tetrapeptides. The same compound has carried the development code MTP-131, the name Bendavia, and — as its international nonproprietary name — elamipretide. Chemically it is D-Arg-2',6'-dimethyltyrosine-Lys-Phe-NH2.

The naming matters practically. The clinical literature and the registry file this compound under elamipretide; the research market sells it as SS-31. A buyer searching one name sees almost none of what exists under the other.

What the label states

DailyMed returned one record for the compound on 2026-09-11: FORZINITY (elamipretide hydrochloride) injection, Stealth BioTherapeutics, SPL version 10, published 12 December 2025, initial US approval 2025.

Item What the label states
Recommended dosage 40 mg subcutaneously once daily, patients ≥ 30 kg
Timing Same time each day
Missed dose Skip it; do not double
eGFR ≥ 30 mL/min 40 mg once daily
eGFR < 30 mL/min, not on dialysis 20 mg once daily
eGFR < 30 mL/min, on dialysis Insufficient information to recommend a regimen
Presentation 280 mg/3.5 mL (80 mg/mL), single-patient-use vials, four per carton
Storage 2°C to 8°C; do not freeze; discard 8 days after first opening
Preservative Benzyl alcohol

This is the first figure in this catalogue's dosage cluster that came from a reviewed application rather than from a page quoting another page.

What the approval actually covers

The indication is narrow and the label says so in unusual detail. FORZINITY is indicated to improve muscle strength in adult and paediatric patients with Barth syndrome weighing at least 30 kg — a rare X-linked mitochondrial disorder.

It was granted under accelerated approval, based on an improvement in knee extensor muscle strength, which the label itself describes as an intermediate clinical endpoint. Continued approval "may be contingent upon verification and description of clinical benefit in a confirmatory trial."

And the clinical experience section rests on a very small group:

In the FORZINITY clinical development program, 12 male patients aged 12 to 35 years with genetically-confirmed Barth syndrome received treatment with daily subcutaneous injections of 40 mg FORZINITY. Eleven of these 12 patients were Caucasian.

Twelve patients, one sex, one rare disease, one intermediate endpoint. That is what stands behind the 40 mg figure. It is still more than any unlabelled research peptide has, and it is a great deal less than "FDA-approved" tends to imply when it appears in marketing copy.

The literature, counted

A title-and-abstract PubMed search for elamipretide[tiab] OR "SS-31"[tiab] OR "MTP-131"[tiab] OR bendavia[tiab] returned 466 records on 2026-09-11.

Measure Count
Title/abstract records 466
Human-tagged 192
Randomised-controlled-trial publication type 18
ClinicalTrials.gov registrations 21

For comparison, the same three searches against the compounds on this site's other dosage pages return counts in the tens, and randomised-trial counts of zero. SS-31 is the best-studied molecule in this catalogue by an order of magnitude. That is a statement about the file, not an endorsement of any use of it.

The formulation gap, which is where the arithmetic goes wrong

The approved product is a solution. Research-market SS-31 is a powder. The molecule is the same; nothing else about handling it is.

  • FORZINITY is 80 mg/mL, already in solution, so the labelled 40 mg is 0.5 mL.
  • A research-market 50 mg lyophilized vial reconstituted in 2 mL of bacteriostatic water is 25 mg/mL, at which 40 mg would be 1.6 mL — more than a 1 mL insulin syringe holds in one draw.

Our reconstitution page carries the arithmetic for other vial-and-volume combinations, and our what the unit markings on an insulin syringe mean covers what the unit markings mean and where dead space goes at small volumes.

The preservative is a second gap. The approved solution contains benzyl alcohol, which is what makes an eight-day in-use window possible after the vial is first opened, and which carries the label's neonatal warning. Bacteriostatic water is also benzyl-alcohol-preserved, at 0.9%; sterile water is not preserved at all. Our bacteriostatic water page covers that difference and what it does to an in-use window.

What is not established

  • The approval covers Barth syndrome and nothing else. The mitochondrial-function and anti-ageing claims attached to SS-31 on research pages were not what was reviewed.
  • The endpoint was intermediate. Knee extensor strength improved; the label does not claim a demonstrated clinical benefit, and says continued approval may depend on a confirmatory trial.
  • The safety data is twelve patients deep in the labelled programme, all male, one ethnicity for eleven of them.
  • No labelled figure exists for any other population, including anyone under 30 kg, anyone on dialysis, and anyone without Barth syndrome.
  • The research-market product is not the approved product. Different formulation, different preservative status, different storage, different in-use window, and no lot release under 21 CFR 211.84.

What a reader can check in five minutes

  1. Search DailyMed for elamipretide — one record, FORZINITY, Stealth BioTherapeutics.
  2. Open that label and read section 2.1 for the 40 mg figure and Table 1 for the renal reduction.
  3. Read section 6.1 and count the patients in the clinical development programme.
  4. Read section 1 and note the words "accelerated approval" and "intermediate clinical endpoint".
  5. Search PubMed for elamipretide and again for "SS-31" — and notice how much of the file each name alone would have hidden.

Injectable NAD+ is sold into the same mitochondrial-health market with no label at all, and its trial and clinic doses differ fifty-fold. Our AOD-9604 page is the opposite case: a compound whose literature is mostly about detecting it. How to read a dosing claim sets out the checks that separate a label figure from a convention, and our page on reading a certificate of analysis covers what a research-market document does and does not establish about what is in a vial.

Sources and dates

Opened 2026-09-11: the DailyMed SPL search API for elamipretide (one record, setid 146bf34c-76f2-48db-ac07-fb29cce2cd75, SPL version 10, published 12 December 2025) and the full structured product label for FORZINITY, from which every labelled figure, the indication wording, the accelerated-approval statement, the renal table, the storage and in-use conditions, the benzyl alcohol warning and the twelve-patient clinical experience section are taken verbatim; PubMed through the NCBI E-utilities for elamipretide[tiab] OR "SS-31"[tiab] OR "MTP-131"[tiab] OR bendavia[tiab] (466 records; 192 with the humans MeSH term; 18 under the randomised-controlled-trial publication type); the ClinicalTrials.gov v2 API for elamipretide (21 studies). Corrections go to the contact page.

Frequently asked questions

What is the standard SS-31 dose?

There is now a labelled one, which is new for this compound. FORZINITY, the approved elamipretide product, is labelled at 40 mg subcutaneously once daily for patients weighing at least 30 kg, reduced to 20 mg daily in adults with an eGFR below 30 mL/minute who are not on dialysis. That figure was reviewed by a regulator for one narrow indication — Barth syndrome — in a programme whose clinical experience section describes twelve patients. It is a labelled dose for that population, not a general-purpose figure, and this page reports it rather than recommending it.

Is SS-31 the same thing as elamipretide?

Yes. SS-31 is the original research designation from the Szeto-Schiller peptide series; elamipretide is the international nonproprietary name. The same molecule has also been called MTP-131 and Bendavia during development. Anyone comparing a research-market listing with the published literature should search both names, because the trial literature is filed almost entirely under elamipretide and the vendor literature almost entirely under SS-31.

Why does the approved product come as a liquid when research vials are powder?

They are different products built for different distribution. FORZINITY is supplied as a sterile aqueous solution at 80 mg/mL in 3.5 mL single-patient-use vials, refrigerated at 2°C to 8°C and discarded eight days after first opening, with benzyl alcohol as a preservative. Research-market SS-31 is typically a lyophilized powder that has to be reconstituted before use. The molecule is the same; the formulation, the preservative, the storage requirement and the in-use window are not, so a figure taken from the label does not carry its handling conditions across.

How much evidence is there behind elamipretide?

More than behind most compounds in this catalogue, and still less than the approval might suggest. PubMed returns 466 title-and-abstract records, 192 human-tagged, 18 with the randomised-controlled-trial publication type; ClinicalTrials.gov holds 21 studies. But the approval itself is accelerated, granted on an intermediate endpoint rather than a clinical one, and the label's clinical experience section describes twelve patients in a single rare disease. Depth of literature and strength of approval are two different measurements and this compound scores differently on each.

Does the Barth syndrome approval say anything about other uses?

No, and the label is explicit about the limits of what was demonstrated: improvement in knee extensor muscle strength, an intermediate clinical endpoint, in patients weighing at least 30 kg with genetically confirmed Barth syndrome, with continued approval contingent on verification in a confirmatory trial. Elamipretide has been studied in other settings — the registry holds 21 studies — but an approval covers what it covers. The mitochondrial and anti-ageing claims attached to SS-31 on research pages are not what the FDA reviewed.

What does a 40 mg quantity look like if the vial is a powder?

It depends entirely on the reconstitution. The approved solution is 80 mg/mL, so 40 mg is 0.5 mL. A research-market 50 mg lyophilized vial reconstituted in 2 mL of bacteriostatic water gives 25 mg/mL, at which 40 mg would be 1.6 mL — more than a 1 mL insulin syringe holds. The arithmetic is on our reconstitution page. The comparison is offered because the number on a label and the number on a syringe are not the same measurement, and the difference is where errors live.