thymosin alpha 1: what tests found in people with hepatitis, sepsis, and weaker defenses with age.

What can thymosin alpha 1 research tell you?

A bad infection can drain your strength or keep coming back. Your doctor may then talk about the immune system, which guards you from germs and infected cells. Thymosin alpha 1 is a lab-made drug also called thymalfasin. Scientists call it a peptide, meaning a short piece of protein.

Your body builds protein by linking tiny parts called amino acids; this drug is one 28-amino-acid piece. The first report of thymosin alpha 1 came from calf thymus tissue in 1977 ^[16]. The thymus is a gland that trains some cells to fight germs. Scientists use daltons to weigh very small protein pieces. Thymosin alpha 1 weighs 3,108 daltons. It has no sulfur bonds holding its parts together ^[16]. Those details describe its make-up, not how well it works. Thymosin alpha 1 tests later included hepatitis, sepsis, HIV, COVID-19, cancer, and weak defenses in old age.

The best early results came from people with hepatitis B. They got 1.6 mg into the fat below the skin, two times each week for 6 months. At the 12-month check, 55.6% had a blood result meaning the virus had gone quiet and the body had made defenses against it. The same change appeared in 27.3% with interferon-alpha, an older drug that helps fight viruses, and 3.3% with no care ^[1]. A review joined 8 tests with 583 people. The drug plus lamivudine, a drug that stops the virus making copies, reached that result in 45.1%. Lamivudine alone reached 15.2% ^[15]. The findings helped Zadaxin gain approval in 35 or more nations.

Sepsis is a harsh response to an infection that can damage the body. One 2013 test found a 9-point drop in deaths by the 28-day mark: death rates were 26.0% with the drug versus 35.0% without it ^[2]. A 2016 review joined 19 tests with 1,354 people and also found fewer deaths with the drug ^[3].

The largest sepsis test didn't repeat the early result. In 2025, a late-stage Phase 3 test enrolled 1,106 people at 22 hospitals. Death rates were 23.4% in the drug group and 24.1% with placebo, a look-alike shot with no drug ^[4]. The test didn't prove that any one sort of patient gains from it.

As of 2025, the FDA hadn't cleared thymosin alpha 1 for any use in the United States. You can read where results look hopeful and where the answer is still no.

Where did thymosin alpha 1 come from?

A shot of thymosin alpha 1 leaves the blood fairly fast. One human test found that about half was gone after 2 hours ^[17]. The lab adds a small chemical piece to one end of the drug. That end piece slows how fast the body breaks it down. The drug also lacks sulfur bonds that air can damage.

Goldstein and his team first found the protein piece while studying calf thymus tissue ^[16]. Lab-made thymosin alpha 1 has the same 28-amino-acid order as the body-made form. Zadaxin, also called thymalfasin, is now made in a lab. It doesn't contain calf tissue.

The scientists were sorting thymus material into groups when they found it. Their group was called fraction 5. That old name only tells where the drug was found; it says nothing about the drug’s effect on you. Thymosin beta-4, called TB-500 in research sales, is another short protein piece. Tests of the beta form asked about skin and tissue repair. Tests of thymosin alpha 1 asked how the body fights germs. The names sound alike because both came from thymus tissue.

Your thymus makes thymosin alpha 1 throughout life, but the gland shrinks after youth, makes less, and sends out fewer new T cells that help fight germs in your body ^[14]. That may be one reason infections hit harder with age.

Why have doctors tested thymosin alpha 1?

People may first hear about thymosin alpha 1 after a hard infection or a weak reply to a vaccine. Human tests cover five main areas.

Hepatitis. Thymosin alpha 1, sold as Zadaxin, is approved in 35+ nations for hepatitis B and C. Some tests compared it with interferon-alpha, an older virus drug. Others added a drug that stops the virus making copies ^[1][15].

Sepsis. This grave illness can wear out cells that fight germs. A 2013 test found fewer deaths with thymosin alpha 1 ^[2]. A much larger 2025 test didn't find fewer deaths in all patients ^[4]. Doctors still don't know whether one group gains.

HIV. HIV is the virus that harms the body's defenses. Some people still have too few T cells after virus drugs work. In one test, people got thymosin alpha 1 at 1.6 mg twice weekly for 24 weeks. Helper T cells rose from 17.2% to 29.1% ^[10]. These cells help lead the fight against germs.

Cancer care. Cancer tests combined thymosin alpha 1 with other care; none used the drug alone. In one liver-cancer test, half the patients lived longer than 110.3 weeks with the added drug and 57.0 weeks without it ^[6]. A skin-cancer report found a 38.4-month middle survival with thymosin alpha 1 before later cancer care, compared with 8 months for that cancer care alone ^[7]. The two results can't tell us that each kind of cancer gains.

Older age. A 2025 review found better vaccine replies in some older people. Work in animals and lab-grown cells also found signs of more new T cells ^[14]. Those lab findings can't predict your own result.

The full page on thymosin alpha-1 and your immune system explains each result and its limits.

Are Zadaxin and thymosin alpha 1 the same drug?

Zadaxin is a brand name for the lab-made drug thymalfasin. It is approved in 35 or more nations. Its active part has the same 28-amino-acid order first found in calf thymus in 1977 ^[16]. SciClone Pharmaceuticals holds rights in many places. The drug is cleared in China, Italy, and 33 more nations.

By 2025, no company had sent the FDA a full request to sell it as a US drug. In 2023, the FDA also limited one route for pharmacies to make it. The common questions page explains what that does and doesn't tell a patient.

Can thymalfasin calm some defenses and wake others?

Some drugs slow your immune system. Others push it harder. Thymosin alpha 1 may do either job, based on what the body lacks. That idea still needs good human tests.

One study checked blood from 320 people with psoriatic arthritis, rheumatoid arthritis, or lupus. Their own thymosin alpha 1 levels were lower than levels in healthy people ^[9]. Finding less in the blood can't tell us whether treatment will ease those illnesses.

Lab work in cells from donated blood found more T cells, B cells, and natural killer cells after thymosin alpha 1 was added ^[8]. The last two kinds also help attack infected or harmful cells. This happened in a lab dish, not in a person's body. It may help explain why doctors study the drug for both weak defenses and defenses that attack the body.

The page on how the drug may work separates dish findings from results in people.