Thymosin Alpha-1 and Pancreatic Cancer Risk: What Is Known
At a glance
- Drug / thymosin alpha-1 (thymalfasin), a 28-amino-acid synthetic peptide [2]
- Action / immune modulator that augments T-cell function [1]
- Hepatitis B evidence / 10 randomized trials, 1,349 adults, reviewed 2026 [3]
- Outcomes reported / death, hepatitis B illness, quality of life, liver histology, adverse events [3]
- US status / not FDA-approved; four orphan drug designations are not approvals [2]
- Approved elsewhere / Zadaxin in Italy and Hong Kong; India for chronic hepatitis B [2]
- Half-life / about 1.8 to 2.6 hours after subcutaneous injection [2]
Does Thymosin Alpha-1 Raise Pancreatic Cancer Risk?
The answer is not known. The hepatitis B trials described here did not report on cancer risk, so they cannot answer this question. The largest randomized evidence base for the peptide is chronic hepatitis B: a 2026 Cochrane review pooled 10 trials with 1,349 adults, published 1991 to 2018 in Bangladesh, China, Italy, Korea, Singapore and Taiwan [3]. Its reported outcomes were death, hepatitis B illness, quality of life, liver histology and adverse events [3]. The reviewers said they were 'not sure' thymosin alpha-1 helps [3].
The review found possible lower all-cause mortality (risk ratio 0.53, 95% CI 0.29 to 0.96; 3 trials, 907 people) at very low certainty, and little to no effect on quality of life or liver histology [3]. On harms, the peptide may have caused fewer serious adverse events than comparison treatments (risk ratio 0.72, 95% CI 0.53 to 0.99; 5 trials, 1,056 people; low-certainty evidence) and fewer non-serious events (risk ratio 0.47, 95% CI 0.27 to 0.83; very low-certainty evidence) [3].
What the Adverse-Event Record Shows
FDA searched its adverse-event database on April 22, 2024 and found zero reports for thymosin alpha-1 [2]. That finding does not establish whether the peptide causes harm. Authors tied to the manufacturer of Zadaxin report more than 4,400 people enrolled in trials and more than 17 million doses given after marketing, describing adverse experiences as 'infrequent and mild' [2]. Treat that as company-linked data.
What the Italian Label Says
There is no US label. The Italian Zadaxin label covers a 1.6 mg powder given subcutaneously or intramuscularly twice weekly for 4 weeks from the first vaccination, repeated weeks 8 to 12 at the second [2]. That label says the product is not for children, is contraindicated in pregnancy and breastfeeding, and advises caution in people with allergies or autoimmune disease and with other immune-modulating drugs [2].
Regulatory Status
Thymosin alpha-1 is not FDA-approved: a Drugs@FDA search found no US application, and FDA's December 2024 review lists four US orphan drug designations, which are a separate process from approval [2]. Italy authorizes Zadaxin as an adjuvant to influenza vaccination in immunocompromised people, India approves it for chronic hepatitis B in adults 18 or older with compensated liver disease and virus replication, and Hong Kong authorizes it [2]. In December 2024 FDA's Pharmacy Compounding Advisory Committee voted 4 yes and 17 no on adding the peptide to the bulk substances list for compounding [4].
Frequently asked questions
Does thymosin alpha-1 cause pancreatic cancer?
What is the strongest evidence for thymosin alpha-1?
Is thymosin alpha-1 FDA-approved?
What side effects showed up in the hepatitis B trials?
References
- Ancell CD, Phipps J, Young L. Thymosin alpha-1. Am J Health Syst Pharm. 2001;58(10):879-85; quiz 886-8. Thymosin alpha-1
- U.S. Food and Drug Administration. U.S. Food and Drug Administration
- 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;9(9):CD014610. Thymosin-ɑ1 for people with chronic hepatitis B
- U.S. Food and Drug Administration. U.S. Food and Drug Administration