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Thymosin Alpha-1 Compounding Pharmacy FDA and State Board Enforcement History

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7 linked public sourcesEditorial, sourcing, and corrections policy

At a glance

  • FDA approval / None; no US marketing application for Ta1 [1]
  • Advisory committee vote / 4 yes, 17 no on both the free base and the acetate, December 4, 2024 [5]
  • Safety-risk listing / Moved to the 'nominated but withdrawn' table after the nominators withdrew [4]
  • State-licensed pharmacy list / In none of the three categories, updated May 14, 2026 [2]
  • Outsourcing facility list / Category 3, 'nominated without adequate support' [3]
  • HHS peptide policy / October 2026 draft covers six other peptides, not Ta1 [6]
  • Orphan designations / Four in the US; a designation is not an approval [1]

What has FDA actually done about thymosin alpha-1?

Thymosin alpha-1 is a 28-amino-acid peptide; thymalfasin is the synthetic version with the same sequence, sold outside the US as Zadaxin 1.6 mg injection [1]. It has no FDA approval and no US marketing application [1]. FDA has assessed Ta1 for its compounding bulk-substance lists and raised safety concerns [4][5].

FDA's page on bulk substances that may present significant safety risks, with content dated April 22, 2026, lists Ta1 in the 'nominated but withdrawn' table: it had been in category 2 and came off when the nominators withdrew [4]. FDA's stated concerns remain posted — 'significant risk for immunogenicity for certain routes of administration', peptide-impurity and characterization problems, and safety information the agency called 'inadequate for the agency to sufficiently understand the extent of any safety issues' [4].

Why did the 2024 advisory committee vote against it?

FDA proposed that Ta1 not be added to the pharmacy bulk substances list. On December 4, 2024, its Pharmacy Compounding Advisory Committee voted 4 yes and 17 no, with no abstentions, on both the free base and the acetate [5]. Members who voted no cited no compelling evidence of clinical effectiveness and safety; some who voted yes said patients should have access [5].

Separately, a 2026 Cochrane review of 10 randomized trials in 1,349 adults with chronic hepatitis B found possible lower all-cause mortality with Ta1 (risk ratio 0.53, 95% CI 0.29 to 0.96; 3 trials, 907 people), but the certainty was very low. It found little to no effect on quality of life or liver histology, and the reviewers said they are 'not sure' Ta1 helps [7].

Where Ta1 sits on FDA's lists today

  • State-licensed pharmacies and physicians: in none of the three categories on the list updated May 14, 2026 [2].
  • Outsourcing facilities: category 3, 'nominated without adequate support', list updated March 21, 2025 [3].
  • Category 1 policy: the policy of generally taking no action against compounders who meet its conditions does not apply to Ta1 [2][3].
  • HHS: the October 2026 draft enforcement-discretion policy names six peptides — BPC-157, epitalon, KPV, MOTS-c, Semax and TB-500 — and Ta1 is not among them [6].

Frequently asked questions

Is thymosin alpha-1 approved by the FDA?
No. There is no US marketing application for it, and four US orphan drug designations are not approvals [1]. It is authorized in some other countries, including Italy, India and Hong Kong, as listed in FDA's December 2024 review [1].
Can a state-licensed pharmacy compound thymosin alpha-1?
Ta1 is in none of the three categories on FDA's list for state-licensed pharmacies and physicians, updated May 14, 2026 [2]. FDA proposed that it not be added to the pharmacy bulk substances list, and the advisory committee voted 4 yes and 17 no on both forms in December 2024 [5]. No FDA or HHS action allowing Ta1 compounding was found.
Is thymosin alpha-1 on FDA's significant-safety-risk list now?
It sits in the 'nominated but withdrawn' table. It had been in category 2 and came off when the nominators withdrew, and FDA's concerns about immunogenicity and peptide impurities are still posted [4].
Does the October 2026 HHS peptide policy cover thymosin alpha-1?
No. The draft enforcement-discretion policy names six peptides: BPC-157, epitalon, KPV, MOTS-c, Semax and TB-500. Ta1 is not one of them [6].

References

  1. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  2. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  3. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  4. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks | FDA. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks | FDA
  5. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  6. Official web page. Official web page
  7. Naing C, Ni H, Aung HH, Aye SN, Nikolova D, Poovorawan Y, et al. Thymosin-ɑ1 for people with chronic hepatitis B. Cochrane Database Syst Rev. 2026. Thymosin-ɑ1 for people with chronic hepatitis B
Evidence overview for Thymosin Alpha-1 Compounding Pharmacy FDA and State Board Enforcement History