TB-500 in Adults 65 and Older: What Geriatric Patients Need to Know

What is TB-500, exactly?

TB-500 is a synthetic 7-amino-acid fragment of the 43-amino-acid protein thymosin beta-4, specifically residues 17 to 23, N-acetylated, with a molecular weight of about 889 g/mol [1]. It is not full-length thymosin beta-4, and it is not thymosin alpha-1 [1]. TB-500 is a common name rather than an official drug name, and FDA found several salts and derivatives with different active moieties sold under it [1].

The peptide sold online as a 2 mg to 15 mg vial, alone or blended with BPC-157, is therefore not the protein used in the published thymosin beta-4 trials [1].

Is there any TB-500 research in people over 65?

No. FDA searched PubMed, Embase, ClinicalTrials.gov and other sources for its July 2026 evaluation, and none of the three papers the nominator cited involved TB-500 in humans [1]. FDA also found no human pharmacokinetic or pharmacodynamic data for TB-500 by any route [1]. That means there is no information on how an older adult's blood levels, or an older adult's response, would differ from a younger adult's.

Why the thymosin beta-4 studies do not answer the question

Several human trials exist for full-length recombinant thymosin beta-4 or for thymosin beta-4 eye drops. They tested a different molecule [1].

A first-in-human phase 1 study gave recombinant human thymosin beta-4 intravenously to 54 healthy Chinese volunteers in single ascending doses from 0.05 to 25 micrograms/kg, plus 30 volunteers who received 0.5, 2 or 5 micrograms/kg daily for 10 days [6]. Adverse events were mild to moderate, with no dose-limiting toxicity and no serious adverse events, and no obvious accumulation with repeated dosing [6].

In dry eye, a phase 2 trial randomised 72 adults to 0.1% thymosin beta-4 drops or placebo for 28 days; neither primary endpoint, ocular discomfort or inferior corneal staining, differed significantly between groups, though some secondary endpoints did [7]. A much smaller phase 2 trial treated 9 patients with severe dry eye (12 eyes on active drops, 6 on vehicle) and reported a 35.1% reduction in ocular discomfort and a 59.1% reduction in total corneal staining versus vehicle at day 56 [8]. In 96 patients after a heart attack, a placebo-controlled trial found no significant overall difference in infarct area, although the subgroup given the first dose within 8 hours (n=43) had a smaller infarct area at 90 days [9].

None of this describes what the fragment does in an older adult.

What the laboratory and animal data show

FDA found no in-vivo animal study of TB-500 for wound healing, the use it evaluated [1]. In an in-vitro scratch-wound test, TB-500 at 50 micrograms/mL did not induce wound closure in fibroblast cultures; a shorter metabolite, N-acetylated LKKTE, did show activity in vitro [1]. In animals, TB-500 given subcutaneously or intraperitoneally reaches the bloodstream and is broken down into smaller peptides, and no intramuscular animal studies were found [1].

What is known about risk from an injected peptide

FDA's stated concern for injectable TB-500 is immunogenicity, an immune reaction, potentially amplified by peptide aggregation and impurities; it found no study of TB-500 immunogenicity or aggregation and no nonclinical toxicity studies [1]. FDA's safety-risk page gives the same immunogenicity concern for injectable peptides [10].

FDA's adverse-event database search through March 26, 2025 retrieved no TB-500 reports. Its food and supplement complaint system, searched from January 1, 2004 to March 10, 2025, retrieved two cases involving a blended TB-500 and BPC-157 product, with no safety assessment [1]. FDA found no published case reports [1]. Safety in humans is unknown [1].

One case appears in FDA's separate BPC-157 review: a 40-year-old woman injected a research-purposes BPC-157 plus TB-500 product (5 mg/5 mg) subcutaneously twice daily and developed widespread skin hyperpigmentation and gum darkening within a week, which recurred when she re-tried the product two weeks later [11]. Because the product contained two peptides, FDA said it cannot tell whether either caused the reaction [11].

Is TB-500 approved, legal, or available by prescription?

TB-500 is not an FDA-approved drug. FDA's July 2026 review found no USP or National Formulary monograph for it, no FDA-approved drug containing it, no listing in the European or Japanese pharmacopeias, and no approved product in Canada, Australia, the UK, Belgium, Ireland, France, Norway, Germany, Spain or Italy, or authorised by the European Medicines Agency [1].

It appears in the nominated-but-withdrawn table on FDA's page about bulk substances that may present significant safety risks. That table holds substances previously placed in category 2 whose nominators withdrew them [10]. FDA's stated concerns there are that it has not identified any human exposure data on the fragment, lacks important safety information, and that injectable peptides may pose immunogenicity risk [10]. Removal from category 2 was not a finding that TB-500 is safe [10].

TB-500 appears in none of the three categories on FDA's list for state-licensed pharmacies and physicians (updated May 14, 2026) or on FDA's list for outsourcing facilities (updated March 21, 2025), so FDA's category 1 policy of generally not acting against compounders does not cover it [2][3][4]. FDA staff proposed in July 2026 that neither the free base nor the acetate be added to the pharmacy bulks list. They cited inconsistent naming, missing impurity, aggregate and endotoxin data, unclear historical use, no evidence of effectiveness for wound healing, no human data of any kind, immunogenicity risk, and the existence of FDA-approved wound treatments [1]. The Pharmacy Compounding Advisory Committee voted on July 23, 2026 in favour of adding it, against staff's recommendation. That vote is non-binding advice; TB-500 is not on the list, and adding it takes formal rulemaking [12][13].

HHS has filed a draft enforcement-discretion policy naming TB-500 among six peptides, with the others being BPC-157, epitalon, KPV, MOTS-c and Semax; it covers TB-500 acetate given by subcutaneous or intramuscular injection [13][14]. Publication was scheduled for October 30, 2026, with comments due two weeks after publication [13]. Under the draft, HHS says it does not intend to take enforcement action against a state-licensed pharmacy, federal facility or licensed physician compounding with the peptide if conditions are met, such as a single active ingredient, a patient-specific prescription, and an FDA-registered manufacturer supplying a certificate of analysis [13][14]. The notice states that it establishes no rights for any person and is not binding on HHS or the public [13]. Compounded drugs are not FDA-approved, and FDA does not review their safety, effectiveness or quality before marketing [13].

WADA's Prohibited List names 'Thymosin-beta4 and its derivatives e.g. TB-500' in class S2.3, growth factors and growth factor modulators, prohibited at all times in and out of competition; it is on the 2026 List and stays on the 2027 List [5][15].

What about the human data often cited for TB-500?

The closest thing to human experience is a 2021 retrospective chart review from one Florida clinic: 16 patients were reached by phone after intra-articular peptide injections, 12 had BPC-157 alone and 4 had BPC-157 plus thymosin beta-4, with the form not specified [16]. Three of the 4 in the combination group reported significant improvement, against 11 of 12 on BPC-157 alone. There was no control group and no validated measurement tool, and most patients were recalling results from six months to a year earlier [16]. It cannot show that TB-500 works.

Is there a geriatric TB-500 dose?

There is no approved dose for TB-500 at any age [1]. The nomination FDA reviewed proposed a 3 mg/mL lyophilised powder for subcutaneous or intramuscular injection, which is a proposed product description rather than a recommended regimen [1]. Doses used in trials of recombinant full-length thymosin beta-4 are doses of a different molecule and do not apply to TB-500 [1].