Quick answer: All three were pharmaceutical programs, not community discoveries. One completed Phase 2 trials with positive results and then ran out of company. One failed its pivotal trial outright and was abandoned in 2007. One spent two decades missing endpoints and then won an FDA approval in 2025. Knowing which is which tells you more than any mechanism summary.
Why development history is the useful thing to know
Most peptide content describes mechanisms. Mechanisms are interesting, and they are also the easiest part to write, because a plausible pathway can be assembled from preclinical papers for almost any compound.
Clinical development history is harder to spin. A trial either met its primary endpoint or it did not. A company either continued the program or it stopped. These are matters of public record, and they tell you where a compound actually sits - which is usually somewhere less exciting than the mechanism suggests.
These three are worth putting side by side because they occupy three genuinely different positions, and because all three are frequently discussed as though they occupied the same one.
ARA-290: the program that worked and then stopped
ARA-290, generic name cibinetide, is an 11-amino-acid peptide with the sequence pGlu-Glu-Gln-Leu-Glu-Arg-Ala-Leu-Asn-Ser-Ser. CAS 1208243-50-8, formula C₅₁H₈₄N₁₆O₂₁, molecular weight approximately 1257. It also appears in the literature as pHBSP - pyroglutamate helix B surface peptide.
The origin is a genuinely elegant piece of pharmacology. Michael Brines and Anthony Cerami were investigating erythropoietin's non-hematopoietic effects. The central finding, reported by Leist and colleagues in Science in 2004, was that chemically modifying EPO to eliminate its red-blood-cell-stimulating activity did not eliminate its tissue-protective properties. That implied two distinct receptor systems doing two different jobs.
ARA-290 was engineered from the helix-B surface of the EPO molecule to activate only the second one: the innate repair receptor, a heterocomplex of the EPO receptor and the β-common receptor, CD131. It is non-erythropoietic - it does not raise hematocrit, and it does not carry EPO's associated thrombotic and hypertensive concerns.
The mechanistic evidence is unusually clean. After sciatic nerve injury, ARA-290 produced relief of mechanical and cold allodynia in normal mice - but produced no effect in animals with a β-common receptor knockout. When a compound stops working in animals lacking the specific receptor you claim it acts on, that is about as direct as target validation gets.
Where it stands. Phase 2 randomized controlled trials were completed in small fiber neuropathy associated with sarcoidosis and with type 2 diabetes, reporting improvements in neuropathic and autonomic symptoms and measurable regrowth of corneal small nerve fibers, without significant adverse effects. It received US orphan drug designation. No Phase 3 trial was ever completed, and Araim Pharmaceuticals closed.
That is an unusual profile: positive mid-stage data, a clean mechanism, and no path forward - not because the science failed, but because the company did.
AOD-9604: the program that failed
AOD-9604 - the name stands for Anti-Obesity Drug 9604 - is a synthetic fragment from the C-terminal region of human growth hormone, with a tyrosine at the N-terminus and a disulfide bridge between its two cysteine residues. That cyclization improves resistance to enzymatic breakdown.
The work originated at Monash University in the early 1990s with Frank Ng and colleagues, asking whether the lipolytic activity of full-length human growth hormone could be isolated from its insulin-antagonizing and growth-promoting effects. Notably, the fragment does not activate the growth hormone receptor. Metabolic Pharmaceuticals Ltd. licensed the technology and advanced it through clinical development.
The preclinical data was consistent and encouraging. Multiple rodent studies from independent investigators showed reduced fat mass, increased fat oxidation, and reduced body weight gain without glucose intolerance.
The human data was not. AOD-9604 went through six clinical trials involving roughly 893 participants - a level of clinical development that is genuinely unusual for a compound in this category. The pivotal 24-week Phase 2b trial, with 536 subjects, failed to demonstrate statistically significant weight loss versus placebo. Development for obesity was terminated in 2007.
Worth noting what the trials did establish: the safety profile was indistinguishable from placebo, with no IGF-1 elevation and no glucose disruption. The compound was well tolerated. It simply did not do the thing it was designed to do, at the doses tested, in humans.
Since 2007 the research has shifted context rather than stopped. The more active line of preclinical inquiry now concerns cartilage and joint tissue rather than adipocyte metabolism.
Anyone presenting AOD-9604 as an established fat-loss compound is describing the rodent data and omitting the trial that was run specifically to test that claim.
SS-31: two decades, mostly misses, one approval
SS-31 is a tetrapeptide from the Szeto-Schiller family, and its defining property is not a receptor but a destination. We have covered its mechanism in depth separately in SS-31: the peptide targeting the powerhouse of the cell; this section is about its development record.
Its alternating aromatic-cationic structure causes it to accumulate in the inner mitochondrial membrane at concentrations 1,000 to 5,000-fold above the surrounding cytoplasm - and critically, it does so without requiring a membrane potential, meaning it can reach depolarized, already-damaged mitochondria. Once there it binds cardiolipin, the signature phospholipid of the inner membrane that organizes electron transport chain complexes and the cristae folds where ATP is produced.
Targeting a lipid rather than a protein is genuinely unusual. The overwhelming majority of drug compounds are designed against specific proteins.
The clinical record is mixed, and the mixture is the point. Stealth BioTherapeutics ran trials across primary mitochondrial myopathy, heart failure, ischemia-reperfusion injury and dry age-related macular degeneration. In the larger, better-powered trials for heart failure and mitochondrial myopathy, the compound largely missed its primary endpoints.
Then, on September 19, 2025, FDA granted accelerated approval to elamipretide HCl under the brand name FORZINITY for Barth syndrome - an ultra-rare inherited mitochondrial disease - making it the first FDA-approved therapy for any mitochondrial disease.
Two things about that approval are worth stating precisely. It covers one ultra-rare genetic condition and nothing else - not heart failure, not kidney disease, not aging, not performance. And accelerated approval is a conditional pathway: FDA still requires a confirmatory trial before the approval is settled.
What these three teach you about reading claims
Positive Phase 2 data is not a finish line. ARA-290 has it and still has no Phase 3 and no company.
Preclinical consistency does not predict clinical success. AOD-9604's rodent data was replicated across independent groups and still did not translate.
An approval is scoped. SS-31's approval is real, specific, conditional, and covers one ultra-rare disease. "FDA-approved peptide" as a marketing phrase collapses all of that.
Names multiply, and the multiplication hides things. Every compound here has several. ARA-290 is also cibinetide and pHBSP. SS-31 is also elamipretide, MTP-131, Bendavia and Forzinity. AOD-9604 is closely related to - but not identical with - the material sold as HGH Fragment 176-191; they differ structurally, and some vendors list both at different prices, which tells you something about that vendor either way.
Frequently asked questions
Is ARA-290 FDA-approved?
No. It received orphan drug designation and completed Phase 2 trials, but no Phase 3 was completed and it was never submitted for approval.
What is the innate repair receptor?
A heterocomplex of the EPO receptor and the β-common receptor (CD131). It mediates EPO's tissue-protective signaling, separately from the receptor that drives red blood cell production.
Did AOD-9604 work for weight loss?
Not in its pivotal human trial. The 24-week Phase 2b study in 536 subjects failed its primary endpoint and development was discontinued in 2007, despite consistent positive rodent data.
Is AOD-9604 the same as HGH Fragment 176-191?
They are closely related but structurally different. AOD-9604 is a modified version with a tyrosine addition and a disulfide bridge affecting its stability.
Is SS-31 FDA-approved?
Elamipretide received accelerated approval in September 2025 as FORZINITY for Barth syndrome only. That approval is conditional on a confirmatory trial and does not extend to any other use.
Why does SS-31 have so many names?
SS-31 is the research code, elamipretide the generic name, FORZINITY the approved brand name, and MTP-131 and Bendavia are earlier development codes.
Which of these has the strongest evidence?
They are not comparable on a single scale. SS-31 has an approval for one rare disease and misses elsewhere. ARA-290 has positive Phase 2 data and no further development. AOD-9604 has a well-documented failed trial. Different kinds of evidence, different conclusions.
Where we stand
These three are among the less-covered compounds we supply, and the reason we wrote about their development histories rather than their mechanisms is that the histories are where the honest information lives.
Given the naming multiplicity described above, identity documentation matters more here than usual. Ask for the CAS number, the molecular formula and the molecular weight, and check them against what you intended to order. Our API is synthesized at a WHO/GMP and ISO 9001 certified laboratory in California and tested to greater than 99% purity, with analytical documentation available on request.
Our team is in Chandler, Arizona: (888) 745-1505 or our contact page.
All products sold by BioPure Peptides are intended strictly for in-vitro laboratory and research use only. They are not for human or animal consumption. These statements have not been evaluated by the U.S. Food and Drug Administration, and these products are not intended to diagnose, treat, cure, or prevent any disease.