Thymosin Alpha-1

In 1977 the group around Allan Goldstein isolated a heat-stable peptide of 28 amino acids from thymosin fraction 5 of calf thymus and worked out its sequence. Thymosin alpha-1 thus became one of the first defined thymus peptides, and it remains among the longest studied. In the body it arises from the precursor protein prothymosin alpha; the N-terminal end carries an acetyl group.

Mechanistically the peptide acts on antigen-presenting cells. It activates Toll-like receptors, above all TLR9 and TLR2, on dendritic cells. In preclinical work this leads to a stronger Th1 response, altered cytokine patterns and reinforced cellular immunity; more thymocytes also matured into finished T-cells. That is why the peptide regularly appears as a reference in studies on adaptive immunity, viral infection and immune ageing.

Clinical data exist for several fields:

• Chronic hepatitis B: in a randomised trial with 98 participants, the complete virological response rate 18 months after enrolment was 40.6 percent versus 9.4 percent in the control group, following a 26-week course.
• Severe sepsis: the multicentre ETASS trial with 361 participants found a 28-day mortality of 26.0 versus 35.0 percent, a difference at the edge of statistical significance.
• The peptide has also been studied in hepatitis C, in immune reconstitution models and in connection with COVID-19, there with a view to markers of T-cell exhaustion.

You get thymosin alpha-1 here strictly as a research compound. The text places the evidence in context and is not a guide to use.

In the clinical trials thymosin alpha-1 was regarded as well tolerated. A few points still deserve attention:

• Injection site: mild redness, tenderness or a brief irritation is the most frequent observation, as with most subcutaneously given peptides.
• Intervention in the immune system: the peptide shifts T-cell maturation and strengthens the Th1 response. That matters in settings with an autoimmune component.
• Flu-like reactions: now and then the clinical literature mentions mild, passing fatigue.
• Evidence base: the studies are numerous but cover defined conditions and limited periods. They say little about longer use outside those frames.

This summary is no substitute for medical advice.

• Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide - the first description from 1977, from calf thymus.
• Efficacy of thymosin alpha1 in patients with chronic hepatitis B: a randomized, controlled trial - randomised 1998 hepatitis B trial with 98 participants.
• The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trial - 2013 sepsis trial with 361 participants.