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Thymosin Alpha-1 Compounding Pharmacy: How to Read a Certificate of Analysis

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8 linked public sourcesEditorial, sourcing, and corrections policy

At a glance

  • US approval status / None. Four orphan designations, which are not approvals [1]
  • Foreign finished product / Zadaxin 1.6 mg injection; not interchangeable with bulk powder [1]
  • FDA list, state-licensed pharmacies / In none of the three categories [3]
  • FDA list, outsourcing facilities / Category 3, nominated without adequate support [4]
  • Advisory committee vote, December 2024 / 4 yes, 17 no, no abstentions [5]
  • FDA's stated concerns / Immunogenicity for certain routes, peptide impurities, inadequate safety data [6]
  • Peptide / 28 amino acids, acetylated N-terminal end [1]

What a COA can and cannot do

A COA reports the tests a laboratory ran on one lot of material, the methods used, the results, and a lot number. That lot may be the bulk Ta1 powder or the finished vial, and the two are not the same thing. Compounded drugs are not FDA-approved, and FDA does not review them for safety, effectiveness or quality before they reach patients [2]. Federal law separates compounding for individual prescriptions from registered outsourcing facilities, which must follow current good manufacturing practice requirements [2].

Why a Ta1 COA is harder to read

Drugs@FDA lists no US application for thymosin alpha-1, and its four orphan drug designations are a separate process, not approvals [1], so there is no US-approved Ta1 specification to check a batch against. Zadaxin, the finished 1.6 mg injection sold outside the US, is not interchangeable with bulk Ta1 powder, so its specification does not carry over to a compounded lot [1].

FDA has also posted its concerns about the substance: significant risk for immunogenicity for certain routes of administration, peptide-impurity and characterization problems, and safety information inadequate for the agency to understand the extent of any safety issues [6]. Ta1 was previously in category 2 of FDA's significant-safety-risk list and now appears in the nominated-but-withdrawn table because the nominators withdrew it [6]. Identity and impurity results can help describe a batch, but they do not resolve those concerns.

The fields that carry weight

  • Identity. The material should match the Ta1 sequence: 28 amino acids with an acetylated N-terminal end [1].
  • Impurity profile, not just the purity figure. FDA's concern is peptide-related impurities [6].
  • Endotoxin and sterility. Check whether the COA reports these tests, and which laboratory ran them.
  • Lot number. For a finished-vial COA, the lot number should match the vial. For a bulk-powder COA, the lot belongs to the ingredient, so look for a record connecting that ingredient lot to the finished vial. Test dates help show when the material was tested.

The question that comes before the COA

Thymosin alpha-1 is not FDA-approved [1]. FDA lists approvals in Italy, where Zadaxin is authorized as an adjuvant to influenza vaccination in immunocompromised people, India for chronic hepatitis B in adults with compensated liver disease and virus replication, and Hong Kong [1]. In December 2024 FDA's Pharmacy Compounding Advisory Committee voted 4 yes and 17 no on both the free base and the acetate [5]. No FDA or HHS action allowing its compounding is known, and it is not among the peptides in HHS's October 2026 draft policy [7].

What the COA cannot tell you

FDA's April 2024 search of its adverse-event database returned zero reports for Ta1 [1]. That is a count of reports, not a finding of no risk. A 2026 Cochrane review of 10 randomized trials in 1349 adults with chronic hepatitis B found possible lower all-cause mortality (risk ratio 0.53, 95% CI 0.29 to 0.96; 3 trials, 907 people) but rated the certainty very low [8]. A purity result says nothing either way.

Frequently asked questions

Does the COA cover the bulk powder or the finished vial?
Check the document. A COA may describe the bulk Ta1 powder or the finished vial. A finished-vial COA should carry the lot number on your vial. A bulk-powder COA carries the ingredient lot, so look for a record linking it to the finished vial. Zadaxin, the finished injection sold elsewhere, is not interchangeable with bulk Ta1 powder [1].
Is there a US-approved thymosin alpha-1 to compare a COA against?
No. Drugs@FDA lists no application for thymosin alpha-1, and its orphan drug designations are not approvals [1]. Zadaxin, the finished injection sold elsewhere, is not interchangeable with bulk Ta1 powder, so its specification does not transfer to a compounded batch [1].
Can an outsourcing facility compound thymosin alpha-1?
On FDA's list for outsourcing facilities, Ta1 sits in category 3, nominated without adequate support [4]. No FDA or HHS action allowing its compounding is known, and it is not among the six peptides in HHS's October 2026 draft enforcement-discretion policy [7].
Does a COA tell you whether thymosin alpha-1 works?
No. Identity and purity results say nothing about efficacy. A 2026 Cochrane review of 10 randomized trials in 1349 adults with chronic hepatitis B rated the evidence very low certainty and the reviewers said they were not sure Ta1 helps [8].

References

  1. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  2. Human Drug Compounding Laws | FDA. Human Drug Compounding Laws | FDA
  3. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  4. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  5. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  6. 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
  7. Official web page. Official web page
  8. 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: How to Read a Certificate of Analysis