Peptides
Mitochondria-related peptide biology, human evidence and regulatory status.
A mitochondria-targeted peptide blunted semaglutide-linked lean-mass loss — in aged mice
Lean-mass loss is the shadow side of GLP-1 weight-loss drugs, especially in older adults. Eos SENOLYTIX announced on November 9, 2026 that its mitochondria-targeted MitoXcel geropeptide PTC-2105 — a once-weekly subcutaneous injection aimed at age-related decline in mitochondrial membrane potential — will be presented at the 19th SCWD conference (December 10-12, Washington, DC; upgraded to a plenary Rapid Fire session on December 11). In aged, high-fat-fed mice, PTC-2105 monotherapy reversed the terminal lean-mass trajectory from -0.002 g per week on saline to +0.005 g per week; in a second cohort, semaglutide alone produced the steepest terminal lean-mass decline (-0.055 g per week) and shorter survival (p=0.038), while co-administering PTC-2105 at 10 and 25 mg per kg reduced late-life lean-mass loss relative to semaglutide alone (+0.126 and -0.011 g per week). One treated mouse, 'Speedy,' treated from about 80 weeks, is now turning 170 weeks — more than 7.6 months past the last untreated control (137 weeks). All of this is company-reported preclinical data in mice; PTC-2105 is investigational and has not been tested in humans.
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Peptides copied from a mitochondrial DNA helicase kill multidrug-resistant bacteria — in lab tests
Mitochondria began as bacteria — and their targeting signals still speak a bacterial dialect. A study in ACS Omega (Porritiello, Galatola, Agrillo and colleagues, Gianna Palmieri's group; published November 3, 2026) exploits the structural resemblance between mitochondrial targeting sequences and antimicrobial peptides. Using an in-silico design strategy, the team built two 18-residue peptides, TAMP1 and the optimized TAMP2, from the mitochondrial targeting sequence of the Twinkle helicase — the protein that unwinds mitochondrial DNA — taken from the Antarctic fish Notothenia coriiceps. Both peptides fold into stable amphipathic alpha-helices, the classic membrane-attacking shape. TAMP2 kept its potency against an extended panel of spoilage, foodborne and multidrug-resistant pathogens, with minimum bactericidal concentrations of 0.5 to 32 micromolar. Microscale thermophoresis and molecular-dynamics simulations supported strong interactions with bacterial-membrane mimics, and the paper reports no toxic effects in its in vitro and in vivo assays. It is a proof of concept: no infected animal model and no human data.
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HHS opens a limited compounding path for six peptides — including mitochondria-derived MOTS-c — without FDA approval
On October 30, 2026, the Federal Register published an HHS draft policy (91 FR 68526, Doc. 2026-22192, Docket HHS-OASH-2026-0496) stating that the department does not intend to take enforcement action against state-licensed pharmacies, federal facilities or licensed physicians compounding drug products with six peptide bulk substances while the 503A bulks list is developed through rulemaking: BPC-157, Epitalon, KPV, MOTS-c, Semax and TB-500. A seventh peptide from the same advisory process, emideltide, is not included. MOTS-c is the mitochondria-derived peptide in the group — a small peptide encoded in the mitochondrial genome and studied for metabolic effects. The discretion is narrow and conditional: only the listed substance, identity and route (for example, MOTS-c acetate by subcutaneous or intramuscular injection only; Semax intranasal only; KPV topical or oral only); bulk material from an FDA-registered facility with a valid certificate of analysis; an original manufacturer that is FDA-registered and compliant with current good manufacturing practice; serious adverse events reported to FDA MedWatch; the label statement 'This is a compounded drug product. Not for resale.'; a single active ingredient; and a patient-specific prescription, as section 503A requires. The Federal Register text is explicit about what this is not: compounded drugs are not FDA-approved, the policy 'does not establish any rights for any person and is not binding on HHS or the public,' and HHS may revisit it if a safety signal or quality issue arises. Public comments on the draft are being taken until 11:59 PM Eastern on November 13, 2026. None of the six peptides currently qualifies for the bulks list by the standard routes — no USP/NF monograph, not a component of an FDA-approved drug, not already listed — which is precisely why an enforcement-discretion policy, rather than a listing, is the instrument being used.
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A mitochondria-targeted geropeptide preserved movement in super-aged rats — in rats, in small interim groups
PTC-2105 is a once-weekly injected peptide from Eos SENOLYTIX's MitoXcel program, designed to target the age-related decline in mitochondrial membrane potential — improving mitochondrial efficiency in aging cells and, the company says, selectively eliminating senescent cells through mitochondria-mediated apoptosis. On October 30, 2026 the company reported early interim results from a 32-week study run externally at the Albert Einstein College of Medicine's BIO-VITAL preclinical testing core in the Bronx: in the oldest rats, about 24 to 26 months old at enrollment, once-weekly subcutaneous PTC-2105 preserved Rotarod and treadmill motor performance at Week 16 and increased fat-mass loss at Week 8 compared with vehicle, in small interim groups. Reported figures for the 0.5 mg/kg group include Rotarod latency near baseline versus an approximately 76% decline in vehicle animals — a 78.4-percentage-point difference drawn from groups of 3 and 4 animals. The study is an IND-enabling program with first-in-human trials targeted for 2027, initially for sarcopenia and sarcopenic obesity. Every number here is from rats and mice, released by the company, and has not been tested in a single human.
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Federal regulators will not act against licensed compounders making six peptides, including mitochondrial MOTS-c — for now
On October 28, 2026, the U.S. Department of Health and Human Services published an enforcement-discretion policy in the Federal Register: the FDA will not take action against state-licensed pharmacies, federal facilities or licensed physicians that compound six peptides — BPC-157, TB-500, epitalon, KPV, MOTS-c and Semax — while formal rulemaking on the 503A bulk substances list continues. Discretion is conditional, not a free pass: ingredients must come from FDA-registered, CGMP-compliant manufacturers with certificates of analysis and testing, preparations must be single-API and patient-specific, and compounders must meet labeling and adverse-event reporting requirements, with specified routes for each peptide (MOTS-c: subcutaneous or intramuscular injection only). Two facts belong beside the headline. First, this is not FDA approval — none of the six has been reviewed and approved for safety or effectiveness. Second, the agency's own scientific staff had recommended against allowing them, while a July advisory panel recommended allowing all six; HHS describes the policy as interim and open to public comment, and says it may revisit it if safety signals arise. For readers of this site, the mitochondrial name on the list is MOTS-c — a peptide encoded in mitochondrial DNA and studied for metabolic and exercise-related effects, whose human evidence base remains small and early.
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A safety group asked the FDA to block compounding of seven peptides — including MOTS-c
The peptide access fight now has a formal counter-petition. On October 21, 2026, the Partnership for Safe Medicines filed a citizen petition urging the FDA to block compounding of seven unapproved substances — BPC-157, KPV, TB-500, MOTS-c, emideltide, semax and epitalon — and to disregard the July Pharmacy Compounding Advisory Committee vote that recommended allowing six of the seven, arguing the committee was constituted in violation of federal conflict-of-interest laws. FDA scientists had recommended against bulk compounding of all seven, citing no adequate characterization, extremely limited safety data and no meaningful human evidence. MOTS-c is the mitochondria-derived peptide on the list.
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A mitochondrial 'geropeptide' kept very old mice moving and living longer — in company data presented in Berlin
At the 17th World Congress on Targeting Mitochondria in Berlin on October 22, 2026, Eos SENOLYTIX chief executive Dr Kevin Slawin presented company-generated, not peer-reviewed, data for PTC-2105, a mitochondrial-targeted geropeptide in the SS-31/elamipretide lineage. In naturally aged mice, weekly dosing was associated with improved survival at the 25 mg/kg dose (log-rank p=0.0142), dose-dependent gains on a functional composite score, an approximately 70% reduction in a kidney-stress urine marker in aged high-fat-diet mice, and lower inflammatory markers IL-6, TNF-alpha and CXCL10. The reporting itself stresses the caveats: some monitored arms held only 3–5 animals, and one standout 167-week-old mouse is an anecdote, not cohort evidence.
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A possible temporary path for compounded peptides — including mitochondria's own MOTS-c — reaches the White House
Federal officials have submitted an 'interim access policy for compounding using certain peptides' to the White House for review, according to reporting October 15, 2026. Sources familiar with the plan say it could let compounding pharmacies temporarily make popular peptides including BPC-157 through enforcement discretion. Nothing is final, peptides are not FDA-approved as safe or effective, and a July advisory panel's 6-of-7 recommendation — against FDA staff scientists — is still not law.
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Mitochondrial peptide MOTS-c shielded retinal blood vessels in diabetes — in lab models
Researchers at Nanjing Drum Tower Hospital found that MOTS-c, a peptide encoded by the mitochondrial genome, protected retinal blood-vessel cells from high-glucose injury in cell culture and preserved the blood-retinal barrier in diabetic mice.
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A mitochondria-targeting peptide reversed egg aging — in mice and, early on, in human eggs
A week of elamipretide restored youthful fertility in middle-aged mice by rescuing mitochondrial energy in oocytes; in a small human experiment, eggs from women 35 and older matured and fertilized better. The benefit faded after a month, and the human sample was tiny.
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FDA advisers voted to clear six peptides for legal compounding — including one made by your mitochondria
The FDA’s Pharmacy Compounding Advisory Committee voted to recommend BPC-157, TB-500, KPV, MOTS-c, Semax, and Epitalon for the 503A bulk list — against the unanimous recommendation of the FDA’s own scientists. The vote changes nothing yet: compounding these substances remains unlawful until formal rulemaking is complete.
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A mitochondria-targeted peptide restored fertility in aged mice — in mice
Seven days of elamipretide (SS-31) — the cardiolipin-binding peptide already approved for Barth syndrome — more than doubled egg yield in 10-month-old mice, but the small human-egg experiments don't yet clear the statistical bar.
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MOTS-c “exercise mimetic”: the first human trial is recruiting — everything else is still mice
The MOTS-MET Phase 2a trial (NCT07505745) is recruiting adults with prediabetes for 12 weeks of investigational MOTS-c. No completed human trial shows it improves endurance, strength, or weight — and it's WADA-prohibited.
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SS-31 protects ovaries from chemotherapy damage — in mice
Three weeks of the mitochondria-targeted peptide SS-31 restored follicle counts, hormones, and mitochondrial membrane potential in a mouse model of cisplatin-induced premature ovarian failure.
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Mitochondria-targeted peptides take the stage — from FORZINITY to XPRIZE Healthspan
Eos SENOLYTIX will present MitoXcel mitochondria-targeted geropeptides at the 17th World Congress on Targeting Mitochondria; a Mighty Therapeutics/UW elamipretide team won an XPRIZE Healthspan Milestone 2 Award.
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MOTS-c is intriguing biology—not an approved therapy
Animal and observational human studies have generated attention, but no completed human intervention trial proves performance, fat-loss or longevity benefits.
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