TB-500 + CJC-1295 Stack: Safety Monitoring, Dosing, and What the Evidence Actually Shows

What human data exist for each peptide?

CJC-1295 has three published human studies, and FDA identified all three: Teichman 2006, Ionescu and Frohman 2006, and Sackmann-Sala 2009. Every one used the DAC form and every one enrolled healthy volunteers; FDA found no study of any form of CJC-1295 in people with a disease [1]. The DAC form is the peptide with an extra maleimidopropionic acid-lysine unit at the C-terminal end that lets it bind blood albumin, so it lasts days rather than minutes [1][7].

For TB-500, FDA's July 2026 review searched PubMed, Embase, ClinicalTrials.gov and other sources and found no article in which TB-500 was given to a human. None of the three papers the nominator cited involved TB-500 in people [2].

Is TB-500 the same thing as thymosin beta-4?

No. TB-500 is a synthetic 7-amino-acid fragment (residues 17 to 23) of the 43-amino-acid protein thymosin beta-4, with a molecular weight of about 889 g/mol [2]. It is not full-length thymosin beta-4 and not thymosin alpha-1, and FDA found several salts and derivatives, including different active moieties, sold under the same name [2].

The full-length protein has been given to people, but none of those studies is a TB-500 study. A phase 1 trial in 54 healthy Chinese volunteers used intravenous recombinant human thymosin beta-4 at 0.05 to 25 micrograms/kg in single doses, with adverse events described as mild to moderate and no dose-limiting toxicity or serious adverse events [8]. Two phase 2 dry-eye trials used a 0.1% thymosin beta-4 eye drop, and a 2025 trial in 96 people after a heart attack used the recombinant protein [9][10][11]. These are data on a different product, not on TB-500.

TB-500 itself has thin laboratory data. In an in-vitro scratch-wound test, TB-500 at 50 micrograms/mL did not induce wound closure in fibroblast cultures; a shorter metabolite did show activity in vitro, and FDA found no in-vivo animal study of TB-500 for wound healing [2].

What the CJC-1295 studies actually measured

Teichman 2006 ran two randomized, placebo-controlled, double-blind, ascending-dose trials of 28 and 49 days in healthy adults aged 21 to 61, with a single dose in the first study and two or three weekly or biweekly doses in the second [3]. After one subcutaneous injection, the estimated half-life was 5.8 to 8.1 days, mean plasma growth hormone rose 2- to 10-fold for 6 days or more, and mean IGF-I rose 1.5- to 3-fold for 9 to 11 days; after multiple doses, IGF-I stayed above baseline for up to 28 days [3]. No serious adverse reactions were reported [3].

Ionescu and Frohman 2006 gave healthy men aged 20 to 40 a single injection of 60 or 90 micrograms/kg. A week later, GH pulsatility was preserved, trough GH rose about 7.5-fold, mean GH rose 46% and IGF-I rose 45%, with no difference between the two doses [4].

These trials did not show a health benefit, and FDA found no trial of the version sold as CJC-1295 without DAC [1][3].

The CJC-1295 trial that was stopped

CJC-1295 DAC was withdrawn from clinical trials in 2006 after a participant in a phase 2 trial in HIV lipodystrophy, which enrolled 192 people, died [1]. FDA cites anecdotal news reports: the person had chest discomfort 2 hours after an 11th weekly dose, an ECG showed an acute heart attack, and the attending physician's most likely explanation was undiagnosed coronary artery disease with plaque rupture. The data were never published, so a causal link is neither shown nor excluded [1].

Side effects recorded with CJC-1295

In Teichman 2006, per FDA's summary: injection-site reactions in about 70% in study 1 and in all treated subjects in study 2; headache in 63% versus 14% on placebo in study 1; flushing, warmth and transient low blood pressure in about 30% of treated subjects in study 1; transient diarrhea; and transient dizziness and low blood pressure in two subjects. Most events were more common at the higher doses of 125 or 250 micrograms/kg, and no serious adverse reactions were reported [1][3].

In Ionescu and Frohman 2006 there were no serious adverse events, with dose-dependent increases in heart rate and transient injection-site redness and tenderness [1].

FDA's wider concern is the hormone itself: raising GH and IGF-I carries the risks listed on approved growth hormone labels, such as glucose intolerance and diabetes, fluid retention and tumor growth concerns. FDA also called the human studies short, small and mostly single-dose, so long-term safety is unknown [1].

TB-500 side effects and the reported cases

FDA searched its adverse-event database through March 26, 2025 and retrieved no TB-500 reports; its food and supplement complaint system returned two cases between January 1, 2004 and March 10, 2025 concerning a blended TB-500 and BPC-157 product, with no safety assessment [2]. FDA found no published case reports, and safety in humans is unknown [2].

FDA's stated concern for injectable TB-500 is immunogenicity, potentially amplified by peptide aggregation and impurities. It found no study of TB-500 immunogenicity or aggregation, and no nonclinical toxicity studies [2].

One further case appears in FDA's review of a different peptide: a 40-year-old woman used a research-purpose 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. Because the product held two peptides, FDA said it cannot tell whether either caused it [5].

Dosing: what the studies used

There is no FDA-approved dose of either peptide [1][2]. Doses in the CJC-1295 human studies were single subcutaneous injections of about 30 to 250 micrograms/kg, or two to three doses given weekly or every two weeks [1][3]. Those are study doses, not recommendations.

For TB-500 the nomination FDA reviewed proposed a 3 mg/mL lyophilized powder for subcutaneous or intramuscular injection [2]. Any TB-500 schedule circulating online is untested in humans, and doses from trials of recombinant full-length thymosin beta-4 do not apply to TB-500 [2].

What can be measured

The measurable effect of CJC-1295 in the trials was a rise in GH and IGF-I [3]. The trials did not test a monitoring plan. For TB-500, FDA found no human pharmacokinetic or pharmacodynamic data by any route, and the animal work it reviewed covered subcutaneous and intraperitoneal dosing only [2].

Regulatory status

TB-500 is not on FDA's list of bulk drug substances that can be used in compounding. In July 2026 FDA staff proposed that neither TB-500 free base nor TB-500 acetate be added, citing inconsistent naming, missing impurity and aggregate data, no evidence of effectiveness for wound healing, no human data of any kind, immunogenicity risk for injection and the existence of approved wound treatments [2]. FDA's Pharmacy Compounding Advisory Committee reviewed TB-500 on July 23, 2026 and voted in favor of adding it, against staff's recommendation; that advice is not binding and the substance is not on the list [12][13].

HHS filed a draft enforcement-discretion policy on October 28, 2026 (Federal Register document 2026-22192, publication scheduled October 30, 2026) naming TB-500 among six peptides. It covers TB-500 acetate given subcutaneously or intramuscularly, and HHS says it does not intend to take enforcement action against a state-licensed pharmacy, federal facility or licensed physician compounding with it if the policy's conditions are met [13][14]. The notice says it does not establish rights for any person and is not binding on HHS or the public; it is not an approval and does not put TB-500 on any list [13]. Compounded drugs are not FDA-approved, and FDA does not review their safety, effectiveness or quality before marketing [13].

CJC-1295 sits in the nominated-but-withdrawn table of FDA's safety-risk page, previously in the significant-risk category until the nominators withdrew. FDA's stated concerns remain posted: possible immunogenicity for certain routes, impurity and characterization problems, serious adverse events including increased heart rate and systemic vasodilatory reaction, and limited clinical data [15]. It appears in none of the three categories on FDA's list for state-licensed pharmacies and physicians and is not on the outsourcing-facility list [16][17]. On December 4, 2024 the advisory committee voted 0 yes and 13 no on the free base, 1 yes and 12 no on the acetate, and 0 yes and 13 no on each of the three DAC forms [18]. It is not among the six peptides in the October 2026 HHS draft [14].

Both peptides are banned in sport

WADA's 2026 Prohibited List names CJC-1295 and CJC-1293 in S2.2.4 as growth hormone-releasing hormone analogues, and names thymosin-beta4 and its derivatives including TB-500 in S2.3. Both are prohibited at all times, in and out of competition, and S2 substances are non-Specified Substances [6]. Both remain on the 2027 List [19].