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SS-20

SBT-20

C
Animal replicated
Research chemicalSzeto-Schiller PeptideMitochondria-Targeted PeptideCardiolipin Binder
RouteInjectableGray-market only
C
Evidence grade: Animal replicated

Effect demonstrated in multiple animal studies; human data sparse or extrapolated. Grades summarize evidence quality, not whether a compound is appropriate, legal, or risk-free.

At a glance
What it is
Phe-D-Arg-Phe-Lys-NH₂ — Szeto-Schiller Peptide 20 (SBT-20) — Szeto-Schiller Peptide, Mitochondria-Targeted Peptide, Cardiolipin Binder.
Why people use it
Parkinson's Disease · Kidney Ischemia-Reperfusion Injury · Cardiac Ischemia-Reperfusion · Neurodegenerative Disease Models · Aging and Sarcopenia
What the evidence supports
No completed human clinical trial specifically for SS-20/SBT-20 published as of May 2026. All clinical-grade evidence for the SS peptide class comes from SS-31 (Elamipretide, FORZINITY). SS-20 remains a research compound with animal and cell culture evidence base only.
If you only read one thing

SS-20 and SS-31 are sister compounds from the same lab, the same design philosophy, and the same mitochondrial targeting mechanism. The community often treats them as interchangeable or views SS-20 as a weaker version of SS-31. The more accurate framing: SS-20 and SS-31 are pharmacological twins with different tools in their kit. SS-31 adds direct antioxidant chemistry (Dmt-mediated ROS scavenging) on top of the structural cardiolipin mechanism both compounds share. SS-20 uses only the structural mechanism. In conditions where oxidative stress is the primary driver of pathology, SS-31's antioxidant advantage may matter. In conditions where the primary problem is structural — cristae disorganization, ETC supercomplex destabilization, mitochondrial membrane potential collapse — both compounds may be equivalently effective because both address the root structural problem. SS-20 proved this. Whether that means SS-20 is appropriate for specific applications where SS-31's antioxidant activity is redundant or even unnecessary — that question has no human clinical data to answer it.

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Published literature
0human trials0human studies4animal4in vitro

No completed human clinical trial specifically for SS-20/SBT-20; clinical-grade SS peptide evidence comes from SS-31, not SS-20.

Evidence reality check
Human evidence
No human studies
0 observational; RCT evidence not present in corpus.
Preclinical base
8 lab signals
4 animal; 4 in-vitro/mechanistic.
Best-supported use
Parkinson's/dopaminergic neuroprotection
B grade · SS-20 ≈ SS-31 efficacy despite no antioxidant activity; proves structural mechanism primary. SS-31 has more extensive published data; no head-to-head advantage for either
Indication map
Supported / plausible / speculative / avoid
Supported
Parkinson's/dopaminergic neuroprotection
B grade · SS-20 ≈ SS-31 efficacy despite no antioxidant activity; proves structural mechanism primary. SS-31 has more extensive published data; no head-to-head advantage for either
Supported
Kidney ischemia-reperfusion
B grade · Reduced tubular injury, restored mitochondrial function, reduced fibrosis. SS-31 more extensively studied; similar mechanisms expected
Supported
Cardiac ischemia-reperfusion
C grade · Protection comparable to other SS peptides. SS-31 has more published cardiac data including some human-adjacent data
Supported
Aging mitochondrial function
D grade · Theoretical application based on cardiolipin mechanism. SS-31 has Siegel 2023 human ex vivo ADP sensitivity data — stronger evidence

SS-20 is the compound that taught the field how SS-31 actually works. Its value to science is established. Its value to the community user — relative to its more extensively studied sister compound SS-31 — is the question this chapter can clarify but not fully answer.

The central tension resolved: SS-20 and SS-31 share cardiolipin-binding IMM targeting. SS-31 adds antioxidant chemistry (Dmt). SS-20 does not (Phe). In the Parkinson's model — where MPTP causes oxidative stress through Complex I inhibition — SS-20 and SS-31 were comparably neuroprotective. This finding established that the cardiolipin structural mechanism, not antioxidant scavenging, is the primary driver of SS peptide efficacy. SS-20 is a cleaner pharmacological probe of the structural mechanism; SS-31 is the compound with both the structural mechanism and the antioxidant chemistry add-on. SS-31 has Phase 2/3 clinical trials, FDA approval, and human tissue data. SS-20 has animal models and cell culture. For community use, SS-31 is the better-evidenced choice. For mechanistic curiosity about what the cardiolipin structural mechanism specifically does in your biology — SS-20 is the tool.

The strongest argument for SS-20: pure structural mechanism with no antioxidant chemistry confounds. In applications where the primary benefit of SS peptides is structural — cristae organization, ETC supercomplex stability, mitochondrial bioenergetics under chronic structural degradation — SS-20 may produce equivalent results to SS-31. Lower cost than SS-31. No Dmt oxidation concern in solution. Mechanistically clean.

The strongest argument for SS-31 over SS-20: more published evidence. Human clinical trial data. FDA approval for one indication. Siegel 2023 human ex vivo ADP sensitivity finding. The antioxidant chemistry dimension is likely additive in aging and metabolic disease contexts where oxidative stress contributes to pathology alongside structural mitochondrial decline. For most anti-aging and longevity applications, the combination of structural + antioxidant mechanisms in SS-31 is probably better than structural alone in SS-20.

Categories
Muscle & PerformanceCognition & MoodLongevity & Anti-agingMitochondrial & Energy
Properties
Active malignancy: hard stopNot injectable
Molecular weight
~580 Da. Compare to SS-31's ~639 Da. The difference reflects SS-31's dimethyltyrosine (Dmt) vs SS-20's phenylalanine at the position-2 residue.
Half-life
Plasma half-life: estimated at 30-60 minutes after SubQ injection (comparable to SS-31)
Evidence
CAnimal replicated
Sequence
Phe-D-Arg-Phe-Lys-NH₂. The D-arginine at position 2 provides proteolytic stability. The two phenylalanine residues provide aromatic membrane-intercalating character. Net charge +3 at physiological pH — same as SS-31.
Naming Aliases
SS-20 = SBT-20. 'SBT-20' appears in some clinical and regulatory contexts. Same compound, different designation. Unlike SS-31, which accumulated a large family of aliases (Elamipretide, Bendavia, MTP-131, FORZINITY), SS-20 primarily circulates under its two designations.
THE KEY DISTINCTION FROM SS-31
SS-31 has dimethyltyrosine (Dmt) at position 2. Dmt is a potent free radical scavenger — it directly neutralizes superoxide, hydrogen peroxide, and peroxynitrite. SS-20 has phenylalanine (Phe) at position 2. Phe does not scavenge free radicals. SS-20 therefore lacks the direct antioxidant chemistry that was originally proposed as SS-31's primary mechanism. Both peptides accumulate in the IMM, both bind cardiolipin, and both produce cytoprotection in multiple models. SS-20's comparable efficacy despite lacking ROS-scavenging activity proved that cardiolipin structural interaction — not antioxidant chemistry — is the primary mechanism of both peptides.
Mechanism (What It Actually Does)
IMM accumulation via membrane potential (same driving force as SS-31). Cardiolipin binding and membrane interaction (same structural target). Stabilization of ETC supercomplex organization through membrane biophysical effects. No direct radical scavenging (no Dmt). Result: improved mitochondrial bioenergetics, reduced electron leak, cytoprotection — through pure structural/membrane mechanism without antioxidant chemistry.
Animal Evidence
Parkinson's disease model (MPTP): SS-20 and SS-31 provided comparable neuroprotection. Kidney ischemia-reperfusion: SS-20 (as SBT-20) reduced injury, restored mitochondrial function, reduced fibrosis. Cardiac ischemia-reperfusion: cytoprotection documented. Multiple models where SS-20 matches SS-31 efficacy despite lacking antioxidant activity.
Community Use
Small but growing community following, largely from users of SS-31 exploring the broader SS peptide family. Community dose: 5-10 mg SubQ daily (mirroring SS-31 protocols). Limited comparative experience vs SS-31. Why Use SS-20 vs SS-31? Community rationale: different receptor interaction profile means potentially different clinical applications; some users report SS-20 produces a 'cleaner' energy effect without the flush sometimes noted with higher SS-31 doses; the absence of antioxidant chemistry may be relevant in contexts where radical scavenging is not the primary therapeutic goal. None of this has controlled human evidence.
FDA / Regulatory
Not FDA-approved. Not PCAC-reviewed. Research chemical only. Not a controlled substance.
WADA
Not listed on the 2026 WADA Prohibited List. Unlike MOTS-c (S4.4), SS-20 has not been specifically targeted. Verify current status before competition use.
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