Who discovered thymosin alpha 1? Allan L. Goldstein and his colleagues identified the specific molecule in 1977. The earlier thymosin work began with Goldstein, Abraham White and Florence D. Slater in New York in 1966.
Thymosin alpha-1 is a peptide, a short chain of amino acids, the building blocks of proteins. Its sequence, the order of its 28 parts, became the basis for the synthetic medicine thymalfasin, marketed abroad as Zadaxin.
Who discovered thymosin alpha 1, and where?
The starting point was the Albert Einstein College of Medicine in New York. Goldstein, White and Slater were studying whether the thymus released material that influenced immune cells. The thymus is a small organ in the chest where T cells, a type of immune cell, mature.
Their 1966 PNAS paper described extracting and partly purifying material from calf thymus. They called the active preparation thymosin. They tested it in animals and isolated cells, well before it became a prescription-drug question.
A larger team reported alpha-1 itself in PNAS in February 1977. Goldstein and Teresa L. K. Low worked at the University of Texas Medical Branch in Galveston. Collaborators included Chun-Yen Lai and Su-Sun Wang at Roche institutions in Nutley, New Jersey.
That paper established the complete 28-amino-acid sequence. White helped launch the earlier research; the 1977 paper lists a different team.
Why it was called thymosin alpha-1
The thymosin name points back to the thymus. Fraction means a separated portion of an extract. The original 1966 purification diagram ended with fraction 4; later work used the mixture called thymosin fraction 5.
In 1977, researchers isolated alpha-1 from that mixture. The paper grouped thymosin peptides as alpha, beta or gamma according to their behavior during separation by electrical charge. Alpha was the most acidic group. The number identified an individual peptide once its complete sequence was known.
Neither number describes a dose. Fraction 5 contained many peptides; alpha-1 was one defined molecule within it. Promise's thymosin alpha-1 overview explains its identity and later trial record.
From calf tissue to a synthetic molecule
Once the team knew the sequence, chemists could build the chain rather than keep extracting it from animal tissue. FDA's 2024 historical review traces published synthesis work to 1979.
A 1980 Biochemistry paper by T. W. Wong and R. B. Merrifield described making thymosin alpha-1 by solid-phase synthesis. That means assembling the chain on a solid support, then separating and purifying the finished peptide. The resulting material had activity in the laboratory test used by the investigators.
This was a manufacturing milestone. It gave researchers a defined substance to study, rather than a variable tissue extract. It did not establish which illnesses the molecule could help in people. Today's thymalfasin follows that synthetic route, so calf thymus describes the discovery source rather than the contents of the medicine.
The early human chapter: cancer trials
FDA's historical review places the National Cancer Institute's early alpha-1 trial program in 1980. These were studies of people with cancer, not routine immune support in healthy adults.
An early safety report appeared in 1982. In Dillman and colleagues' phase 1 study, meaning an initial study focused on safety, 22 people with advanced cancer received either fraction 5 or alpha-1. Each received a single injection into muscle.
The authors reported no toxic effects from alpha-1 at the doses tested. That observation describes a small study with brief exposure. It cannot establish long-term safety or show that alpha-1 treated the cancer.
Later studies moved into viral hepatitis, vaccine responses and other disease settings. The thymosin alpha-1 benefits guide walks through those later findings. By then, a specific molecule had moved from the lab into human testing.
Thymalfasin and Zadaxin: the overseas route
Thymalfasin is the medicine's non-brand name; Zadaxin is a brand. Country-specific permissions followed, with different uses in different places.
SciClone's 2007 annual report documented authorization in China for hepatitis B, a viral liver infection, and as a vaccine adjuvant, an aid to the vaccine response. FDA's 2024 review also documented an Italian authorization as an aid to flu vaccination in people with weakened immunity.
As of September 30, 2026, the day this article was written, Singapore's registry lists Zadaxin as a prescription medicine. Its National Drug Formulary entry, marked “Last updated 16 September 2026,” lists chronic hepatitis B and combination treatment for hepatitis C.
Those are permissions for particular products and uses. They do not transfer to every preparation carrying the molecule's name.
Why it never became a U.S. drug
The U.S. story includes development efforts that did not become a marketed product. FDA granted thymalfasin an orphan-drug designation for chronic hepatitis B on May 3, 1991. That designation offers incentives for developing a rare-disease treatment; it is not permission to market the medicine.
Confirmatory evidence was uneven. A 1999 phase 3 hepatitis B trial, a larger study designed to test treatment effectiveness, did not confirm earlier favorable findings. SciClone later reported that two hepatitis C trials completed in 2005 and 2006 did not show a clear benefit over the comparison treatment.
Development continued beyond those two results: the 2007 report described an ongoing European combination-treatment trial. Those records describe a development effort that never resulted in U.S. marketing authorization.
Where the discovery stands today
As of September 30, 2026, the day this article was written, the discovery story includes a new receptor finding. A study first published September 3 in Advanced Science reported binding to HCRTR1, a docking protein on nerve cells. Its human portion measured blood from 28 stroke patients and 15 healthy volunteers; treatment experiments involved mice and cells. It did not test alpha-1 as a stroke treatment in people.
As of September 30, 2026, the day this article was written, a September 9 Cochrane review had revisited the hepatitis B evidence. It gathered 10 trials with 1,349 adults. Some results favored treatment when trials were combined, but the authors rated most evidence very uncertain.
As of September 30, 2026, the day this article was written, thymosin alpha-1 prescribed through Promise is dispensed by a licensed U.S. compounding pharmacy as a compounded medication. That means a pharmacy prepares it for an individual prescription. It is different from an FDA-approved product: the formulation offered here is not FDA-approved. FDA's orphan record still lists the hepatitis B indication as not approved. The U.S. regulatory timeline follows the separate compounding reviews.
What the prescription route adds
A licensed provider may still prescribe a compounded formulation; that decision is between the patient and the doctor. At Promise, a licensed U.S. provider reviews every request and not everyone qualifies.
The review connects the intended use with the person's medical history, current medicines and evidence from relevant patients. If a prescription is written, a licensed U.S. compounding pharmacy prepares and dispenses it. The prescription, pharmacy label and follow-up record identify who is responsible for that care.
The provider's job is to explain whether the human evidence fits this person's situation and what remains uncertain. A discovery date, a foreign brand name and a new laboratory finding each supply context for that conversation.
