# Thymosin Alpha-1: the sepsis survival trials

> Thymosin Alpha-1 trials | Peptide Empire — Peptide Empire follows Thymosin Alpha-1 from the earlier sepsis survival signal to TESTS, alongside immune-cell biology, safety and US non-approval.

**The survival question**

The earlier sepsis figures offered encouragement. The larger trial brought the survival rates close together.

## The earlier sepsis result

The earlier numbers explain the hope. In [ETASS, a randomized trial involving 361 patients with severe sepsis](https://pubmed.ncbi.nlm.nih.gov/23327199/), 28-day mortality was 26.0% with thymosin alpha-1 and 35.0% in controls. Sepsis is the dangerous response to infection that can damage organs. A possible survival difference in that setting deserves attention.

The statistical result was awkward: the nonstratified analysis gave P=0.062 and the log-rank analysis P=0.049. Those analyses ask related questions in different ways, leaving an uncertain result close to a conventional significance threshold. I share the impulse to investigate a gap like that, while the uncertain statistics leave the claim of better survival provisional.

## TESTS and 28-day mortality

That stronger test arrived in [TESTS, the double-blind, placebo-controlled phase 3 trial](https://pubmed.ncbi.nlm.nih.gov/39814420/). It included 1,106 adults at 22 centres. Mortality at 28 days was 23.4% with thymosin alpha-1 and 24.1% with placebo. The study found no statistically significant difference.

The earlier trial’s apparent gap had provided a reason to investigate. TESTS supplies the more substantial answer to the sepsis survival question. I favour TESTS when judging sepsis survival. Ordinary respiratory infections, cancer care and chronic viral illness remain separate clinical questions, each with its own evidence.

![Paired mortality percentages for ETASS and TESTS sepsis trials](images/sepsis-mortality.svg)

*28-day mortality in [ETASS](https://pubmed.ncbi.nlm.nih.gov/23327199/) and [TESTS](https://pubmed.ncbi.nlm.nih.gov/39814420/). ETASS had an uncertain earlier result; TESTS found no statistically significant survival difference. The groups and trial designs differed, so this is a comparison of each trial’s own arms.*

## The immune biology

Thymosin alpha-1 was [isolated from calf thymus and its sequence described in 1977](https://pubmed.ncbi.nlm.nih.gov/265536/). It contains 28 amino acids; thymalfasin is the synthetic version with the same sequence. Its history begins with a particular molecule purified from gland material, rather than with a general-purpose immune remedy.

The laboratory biology is more complicated than the phrase “immune boost.” In [experiments involving mouse and human dendritic cells](https://pubmed.ncbi.nlm.nih.gov/16741252/), thymosin affected the breakdown of tryptophan and helped establish a regulatory immune environment alongside immune activation. Dendritic cells present pieces of a threat to other immune cells. Here the research also involved restraint of inflammation.

That regulatory immune behaviour is why thymosin interests me. It makes the ambition to improve immune function biologically interesting, while the sepsis results show how difficult it is to turn the biology into a clinical benefit.

## COVID-19 cohorts; cancer combinations

A [retrospective study of 76 people with severe COVID-19](https://pubmed.ncbi.nlm.nih.gov/32442287/) reported mortality of 11.11% in the treated group and 30.00% in the comparison group, with changes in T-cell numbers and markers of exhaustion. Treatment was not randomly assigned. Differences in illness and accompanying care could have contributed to the association.

Cancer research adds another context. A [review of thymosin alpha-1 in cancer therapy](https://pubmed.ncbi.nlm.nih.gov/31555601/) discusses it alongside chemotherapy and immunotherapy. That is research into an additional treatment within an existing care programme. It leaves a broad claim about treating cancer far beyond the evidence described here.

## Thymalfasin safety and US status

The [comprehensive clinical review](https://pubmed.ncbi.nlm.nih.gov/33362999/) describes local injection-site irritation, redness and discomfort as the common adverse effects. Thymalfasin has approvals abroad and lacks United States marketing approval. Those positions can coexist; a product outside the approved medicine supply brings its own identity, purity and sterility questions.

Pregnancy and breastfeeding safety remain poorly established. Autoimmune disease and medicines deliberately suppressing immunity create further questions about changing immune activity. The [regulatory effects seen in laboratory immune experiments](https://pubmed.ncbi.nlm.nih.gov/16741252/) cannot settle those clinical questions.

Community accounts mention fewer colds, steadier energy, no noticeable benefit, headache or brief flu-like feelings. These are anecdotal accounts, not clinical evidence. On sepsis survival, I put TESTS ahead of the community accounts. A tolerable injection and a season that happened to go well tell a different kind of story. The sepsis trials tested a much more demanding ambition.

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