# TB-500 Detection, WADA Status, and Anti-Doping Testing

> TB-500 detection: the LC-MS and UHPLC-Orbitrap anti-doping methods, the equine LODs of 0.01-0.02 ng/mL, WADA-prohibited status, and how long TB-500 stays in the system. Cited.

The peptide that drove its own detection science — how anti-doping laboratories identify TB-500 and its metabolites, and why it is prohibited in sport.

## How TB-500 detection works

TB-500 detection is a solved analytical problem, and it is one of the better-documented facts in the whole record. Anti-doping laboratories detect the parent peptide and its metabolites by liquid chromatography–mass spectrometry [7]. The first method came out of equine sport: an LC-MS assay detected TB-500 and its metabolites in horse plasma and urine with limits of detection of 0.02 ng/mL in plasma and 0.01 ng/mL in urine — the first identification of TB-500 in post-administration horse samples, developed to control its misuse in equine competition [7].

That same work pinned down the compound's identity. TB-500 was defined as a synthetic version of LKKTETQ, the actin-binding active site within thymosin beta-4, supplied as a veterinary preparation with an artificially acetylated N-terminus [7]. A companion synthesis paper characterized the N-terminal acetylated 17-23 fragment precisely as a doping-control reference, anchoring its chemical identity [8].

The science has advanced since. A 2023 analytical study characterized the TB500/TB1000 and SGF1000 peptide preparations for anti-doping purposes — work aimed at the product class itself rather than its clinical efficacy [12]. A 2024 UHPLC-Q-Exactive Orbitrap MS/MS method then enabled simultaneous quantification of TB-500 and its metabolites in vitro and in rats, refining detection while also screening metabolite wound-healing activity in vitro [14].

## Why Is TB-500 Used in Racehorses?

TB-500 has been encountered as a designer substance in equine sport, which prompted the first LC-MS detection method in horse plasma and urine, reaching limits of detection of 0.01-0.02 ng/mL [7]. It is supplied as a veterinary preparation, and its use in horses is precisely what drove the development of anti-doping detection science for the compound [7]. Its presence in racing was an analytical and regulatory problem to be controlled, not an endorsement of efficacy.

## How Is TB-500 Detected in Doping Tests?

Anti-doping laboratories detect the parent peptide and its metabolites by liquid chromatography–mass spectrometry [7]. The original equine method reached limits of detection of 0.02 ng/mL in plasma and 0.01 ng/mL in urine [7]. Later UHPLC-Q-Exactive Orbitrap MS/MS work quantified TB-500 and its metabolites in vitro and in rats, advancing both sensitivity and metabolite coverage [14]. These are confirmatory analytical methods built specifically for the TB-500 product class [12].

## How Long Does TB-500 Stay in Your System?

No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide, so there is no honest single number for how long it stays in the body [6]. In the intravenous full-length thymosin beta-4 Phase 1 study, half-life increased with dose, but that is the parent protein, not the fragment [6]. The anti-doping LC-MS and Orbitrap work characterizes the peptide and its metabolites for detection rather than for human PK, which is why detection windows are an analytical-laboratory question, not a settled clinical one [7][14].

## Is TB-500 Banned by WADA and in Competitive Sports?

Yes. The World Anti-Doping Agency prohibits TB-500 and thymosin beta-4 under its prohibited peptide, growth-factor and tissue-repair categories, banned in and out of competition for the relevant classes [15]. The compound is detectable by the LC-MS anti-doping assays described above in both human and equine matrices [7][14]. The WADA Prohibited List is updated annually; TB-500 has fallen under these prohibited categories, and athletes in tested sport are subject to the detection methods built specifically for it.

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An evidence-graded review of the TB-500 record: each finding stamped verified, preclinical, or no-human-data and linked to its source, the Ac-LKKTETQ-versus-full-length-thymosin-beta-4 caveat marked on every claim, and the FDA 503A and WADA status read straight from the authorities — no clinic behind the dossier and nothing here dispensed or sold.