Thymosin Alpha-1 (Zadaxin): An Immunomodulatory Peptide for Adaptive Immune Function

This content is provided by Superpower Health for educational and informational purposes only. Superpower Health facilitates access to thymosin alpha-1 through licensed healthcare providers and compounding pharmacy partners. Compounded thymosin alpha-1 is not FDA-approved and has not been evaluated by the FDA for safety, effectiveness, or quality. A patient-specific prescription is required. This page is not a substitute for medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider. For full prescribing information, see the PubChem compound reference (CID 16132341).

Most immune-support compounds work by stimulating the immune system broadly. Thymosin alpha-1 does something more precise: it modulates how the immune system decides what kind of response to mount, and when. That distinction has drawn serious scientific interest for nearly five decades and produced one of the most globally approved peptides in this class.

Here is how thymosin alpha-1 works at the cellular level, what the clinical evidence shows across viral infections, sepsis, and oncology, and which biomarkers providers use to evaluate immune function before and during therapy.

Key Takeaways

• Regulatory Status: As of April 2026, thymosin alpha-1 is not FDA-approved in the United States. It is approved internationally under the brand name Zadaxin for chronic hepatitis B in more than 35 countries, including China and Italy. In the US, it holds FDA 503A Category 2 status following the February 2026 reclassification, meaning it is available by prescription only through licensed compounding pharmacies.
• Research Stage: Clinically studied across decades; internationally approved (Zadaxin); available through US compounding by prescription
• Availability: Not available through Superpower. Thymosin alpha-1 holds FDA 503A Category 2 status following the February 2026 reclassification; access, where available, is through licensed compounding pharmacies under a patient-specific prescription and varies by state.
• Prescribing information: View compound reference data (PubChem CID 16132341)
• How it works: Activates toll-like receptor 9 signaling on dendritic cells, driving Th1 polarization, T-cell maturation, and coordinated adaptive immune responses.
• What the research shows: In pivotal hepatitis B RCTs published in Hepatology, thymosin alpha-1 produced significantly higher rates of complete virological response compared to control, with a low adverse-event burden reported across four decades of clinical trial data.

What Is Thymosin Alpha-1?

Thymosin alpha-1 (Tα1) is a naturally occurring 28-amino-acid peptide, N-terminally acetylated, first isolated from calf thymus tissue in 1977 by Goldstein and colleagues at Abraham White's laboratory, as reported in Proceedings of the National Academy of Sciences. It is derived from the larger precursor protein prothymosin alpha and is the biologically active fragment responsible for the thymus gland's role in T-cell education and immune regulation. The synthetic version is structurally identical to the endogenous peptide and is produced by solid-phase synthesis. Thymosin alpha-1 is commercially available as thymalfasin (brand name Zadaxin), approved in more than 35 countries for the treatment of chronic hepatitis B. In the United States, it is available only by prescription through licensed compounding pharmacies under 503A regulations. A 2007 historical review by Goldstein and Badamchian in Annals of the New York Academy of Sciences traced the peptide's trajectory from its 1974 discovery through its development into Zadaxin. Garaci's 2018 career-spanning review in Expert Opinion on Biological Therapy — "From thymus to cystic fibrosis: the amazing life of thymosin alpha 1" — remains a canonical reference on the biology and clinical arc, and Dominari and colleagues produced a comprehensive 2020 literature review in World Journal of Virology covering the full indication landscape.

What Thymosin Alpha-1 May Support

1. Adaptive immune regulation via Th1 polarization

The core mechanism of thymosin alpha-1 was clarified through a series of landmark studies by Romani and colleagues. A 2004 paper published in Blood demonstrated that Tα1 activates toll-like receptor signaling on dendritic cells, driving those cells to mature and produce the cytokine environment necessary for Th1-polarized T-cell responses. A 2006 follow-up study, also in Blood, showed that Tα1 simultaneously activates tryptophan catabolism via the IDO (indoleamine 2,3-dioxygenase) pathway, which balances pro-inflammatory Th1 activity against immune tolerance. Garaci's 2018 review described this dual effect as the defining feature of Tα1's immunomodulatory profile: it amplifies the immune system's ability to respond to pathogens while maintaining the regulatory mechanisms that prevent excessive inflammation. Giacomini and colleagues published a 2015 study in Expert Opinion on Biological Therapy confirming these effects in human monocyte-derived dendritic cells stimulated with both viral and bacterial TLR agonists. A 2023 umbrella review by Tao and colleagues in Molecules situated these mechanisms within the broader antiviral literature, and a 2010 review by Li and colleagues in Peptides provided the earlier cross-indication synthesis spanning antiviral, anticancer, and adjuvant uses.

2. Chronic hepatitis B viral suppression

Thymosin alpha-1 has the most robust clinical evidence base in chronic hepatitis B, where its immune-modulating mechanism addresses a core pathological feature of the disease: immune exhaustion that permits ongoing viral replication. The clinical program began with Mutchnick and colleagues, whose 1991 placebo-controlled pilot trial in 12 chronic HBV patients published in Hepatology randomized 7 patients to thymosin (fraction 5 or Tα1, twice weekly for 6 months) and 5 to placebo: 6/7 (86%) thymosin-treated patients cleared serum HBV DNA versus 1/5 (20%) placebo patients (P < 0.04), with significant ALT improvements and sustained clinical, biochemical, and serological benefit across 26 ± 3 months of follow-up; no significant adverse effects were reported. The very small cohort limits precision of the estimate, but the signal was sufficient to launch the Phase II program. Chien, Liaw, and colleagues published a pivotal 1998 RCT in Hepatology randomizing 98 chronic HBV patients to thymosin alpha-1 1.6 mg subcutaneously twice weekly for 26 weeks, the same regimen for 52 weeks, or untreated control. At 18 months post-entry, complete virological response (clearance of serum HBV DNA and HBeAg) reached 40.6% in the 26-week group and 26.5% in the 52-week group versus 9.4% in controls (26-week vs. control P = .004). No significant adverse effects were observed. Andreone and colleagues published a 1996 multicenter RCT in Hepatology that randomized 33 anti-HBe-positive chronic hepatitis B patients to Tα1 900 μg/m² subcutaneously twice weekly (n = 17) or interferon alfa 5 MU three times weekly (n = 16) for 6 months, with 6 additional months of follow-up. Complete response (ALT normalization plus HBV DNA loss) at the end of follow-up was 7/17 (41.2%) with Tα1 versus 4/16 (25%) with IFN-alfa, a non-significant difference; Tα1 tolerability was markedly superior, with injection-site discomfort the only reported adverse effect, versus substantial constitutional toxicity on IFN-alfa. The small sample limits statistical power to detect efficacy differences. A 2005 multicenter randomized comparative trial by Iino and colleagues in the Journal of Viral Hepatitis enrolled 316 Japanese chronic hepatitis B patients (HBV DNA-positive with elevated ALT) and compared Tα1 0.8 mg versus 1.6 mg subcutaneously twice weekly for 24 weeks with 72-week total observation. At 72 weeks on the 1.6 mg regimen, ALT normalized in 36.4%, HBV DNA cleared in 30% (branched DNA assay) or 15% (transcription-mediated amplification), and HBeAg cleared in 22.8%; patients with advanced fibrosis responded significantly better on 1.6 mg. Adverse events were mild and most commonly transient liver-enzyme fluctuations consistent with the immune-mediated response. These data reinforced the East Asian approval context for Zadaxin. A 2001 meta-analysis by Chan and colleagues in Alimentary Pharmacology and Therapeutics synthesized the trial data and concluded that Tα1 was associated with suppression of viral replication, with a characteristic delayed response pattern in which the full response often emerges approximately 12 months after therapy cessation. A 2004 review by Sjogren in the Journal of Gastroenterology and Hepatology — written by a principal investigator in the hepatitis program — framed thymalfasin as an immune-system enhancer for chronic liver disease and anchors the international approval narrative.

3. Chronic hepatitis C: signal in treatment-failure populations

The hepatitis C evidence base is less definitive than the hepatitis B data, but a meaningful signal exists in specific populations. Rasi and colleagues published early combination work in 1996 in Gut, an open-label trial pairing Tα1 1 mg subcutaneously twice weekly with lymphoblastoid interferon 3 MU three times weekly for 12 months in 15 chronic HCV patients (11 treatment-naïve, 4 interferon-failures; predominantly HCV genotype 1b). Serum HCV RNA was undetectable in 7/15 (47%) at month 6 and 11/15 (73%) at month 12, with sustained virological response in 6/15 (40%) at 6-month post-treatment follow-up. The small, uncontrolled design precludes efficacy inference versus interferon monotherapy. A 2003 review by Rasi in International Immunopharmacology summarized the rationale for Tα1-based combination strategies in chronic viral hepatitis and HCC prevention. The most clinically relevant finding comes from Poo and colleagues, whose 2008 open-label study in Annals of Hepatology enrolled 40 Hispanic chronic HCV patients who had failed prior interferon alfa/ribavirin and treated them for 48 weeks with thymalfasin 1.6 mg twice weekly, peginterferon alfa-2a 180 μg weekly, and ribavirin 800–1,000 mg daily. Early virological response reached 52.5% at week 12 and 50% at week 24; end-of-treatment response was 52.6%; per-protocol sustained virological response at week 72 was 21.1% overall and 23.5% in genotype 1 patients. Thymalfasin was well tolerated and did not require dose reduction, though peginterferon and ribavirin did. The open-label, single-arm design cannot isolate Tα1's contribution from pegylated interferon/ribavirin alone, but the signal is directionally consistent with the hypothesis that Tα1's immune-enhancing effect is most relevant in patients whose own immune response to HCV has been insufficient, rather than in treatment-naive patients with intact immune function.

4. Sepsis survival and immune reconstitution

Sepsis creates a state of immune paralysis in which T-cell function collapses. Thymosin alpha-1's mechanism of restoring T-cell maturation and Th1 responsiveness has been evaluated in multiple sepsis trials. The foundational clinical evidence comes from Wu and colleagues, whose 2013 ETASS trial published in Critical Care was a multicenter, single-blind RCT enrolling 361 severe sepsis patients across six Chinese ICUs, comparing Tα1 (subcutaneous injection) plus standard care with standard care alone. Twenty-eight-day all-cause mortality was 26.0% in the Tα1 group versus 35.0% in controls, a difference that reached statistical significance only by log-rank analysis (P = 0.049) and was marginal in the primary non-stratified analysis (P = 0.062); improvements in monocyte HLA-DR expression were more consistently significant than the mortality signal. No serious adverse events were attributed to Tα1. The single-blind design and single-country setting limit external validity. Liu and colleagues published a 2016 systematic review in BMC Infectious Diseases examining the quality of RCT evidence for Tα1 in sepsis, providing methodological framing for interpreting the accumulated trial data. The most current and highest-quality evidence is the TESTS trial published in BMJ in 2025 by Wu, Pei, and colleagues: a multicenter, double-blind, placebo-controlled phase 3 RCT in 1,089 adult sepsis patients across 22 Chinese medical centers, comparing subcutaneous Tα1 every 12 hours for seven days against placebo. Twenty-eight-day all-cause mortality was 23.4% in the Tα1 group (127/542) versus 24.1% in the placebo group (132/547), hazard ratio 0.99 (95% CI 0.77–1.27, P = 0.93 by log-rank). No secondary or safety outcome differed significantly. The authors concluded there was no clear evidence that Tα1 reduces 28-day mortality in sepsis, and this adequately powered, double-blind result should now weigh more heavily than earlier positive signals. A 2018 review by Pei and colleagues in Expert Opinion on Biological Therapy examined the mechanism-level rationale for Tα1 in sepsis treatment from the perspective of the principal ETASS investigators.

5. COVID-19 and immune reconstitution in severe viral illness

Thymosin alpha-1 was repurposed for COVID-19 based on its known ability to restore lymphocytopenia and reverse T-cell exhaustion, two hallmarks of severe SARS-CoV-2 infection. Liu and colleagues published the foundational COVID-19 evidence in a 2020 retrospective cohort in Clinical Infectious Diseases across 76 severe COVID-19 patients from two Wuhan hospitals (December 2019–March 2020) comparing Tα1-treated versus untreated cases. Twenty-eight-day mortality was 11.1% on Tα1 versus 30.0% in controls (P = 0.044), with the benefit concentrated in patients with CD8+ counts below 400/μL or CD4+ counts below 650/μL; Tα1 raised T-cell numbers, increased TREC-measured thymic output, and reduced PD-1 and Tim-3 expression on CD8+ T cells — a signature consistent with reversal of T-cell exhaustion. The retrospective, non-randomized design with potential confounding by indication limits causal inference. Wu and colleagues published a 2020 multicenter retrospective cohort study in International Immunopharmacology of 334 critically ill COVID-19 patients across eight Chinese treatment centers, reporting a significantly lower 28-day mortality in Tα1-treated patients in the adjusted model (P = 0.016); the retrospective, non-randomized design limits causal inference. A 2021 multicenter retrospective study by Sun and colleagues in the same journal added confirmatory observational evidence. A 2021 mechanistic study by Matteucci and colleagues published in Open Forum Infectious Diseases provided ex-vivo evidence that Tα1 mitigates cytokine storm in COVID-19 patient blood cells, bridging the observational cohort data to a plausible biological mechanism. Shang and colleagues published a 2023 systematic review and meta-analysis in International Immunopharmacology synthesizing Tα1 outcomes across adult COVID-19 patients. Espinar-Buitrago and colleagues framed the COVID-19 data within the immunosenescence context in a 2023 review published in Immunity and Ageing, noting that Tα1's benefits in severe viral illness may be amplified in older patients whose thymic output has declined with age.

6. Cancer-adjuvant immunotherapy

The oncology evidence base for thymosin alpha-1 is extensive, particularly in Chinese clinical settings, and is being reconsidered in the context of modern immune-checkpoint immunotherapy. Maio and colleagues published the landmark oncology RCT in 2010 in the Journal of Clinical Oncology: a randomized multicenter Phase II trial in 488 metastatic melanoma patients across five arms (dacarbazine with interferon alfa plus Tα1 at 1.6, 3.2, or 6.4 mg; dacarbazine plus Tα1 3.2 mg without IFN; and dacarbazine plus IFN alone as control). The primary endpoint was best overall response at 12 months; 10 responses were recorded in the DTIC + IFN + Tα1 3.2 mg arm and 12 in the DTIC + Tα1 3.2 mg arm versus 4 in the control arm. Median overall survival was 9.4 months on Tα1-containing arms versus 6.6 months on control (HR 0.80, 95% CI 0.63–1.02, P = 0.08), with a similarly directional PFS signal (HR 0.80, 95% CI 0.63–1.01, P = 0.06). The results fell short of conventional significance and the trial was not designed as a confirmatory Phase III, so the survival signal remains hypothesis-generating. Danielli and colleagues reviewed the translation of that trial data to clinical practice in a 2012 paper in the Annals of the New York Academy of Sciences. Guo and colleagues published a 2021 propensity-score-matched analysis in the Chinese Medical Journal showing that Tα1 adjuvant immunotherapy improved long-term survival in non-small cell lung cancer (NSCLC) patients following R0 resection. A PRISMA-compliant systematic review and meta-analysis by Zeng and colleagues, published in 2019 in International Immunopharmacology, analyzed 27 RCTs of synthetic thymic peptides combined with chemotherapy in NSCLC patients in China. Costantini and colleagues published a 2019 reappraisal of Tα1 in cancer therapy in Frontiers in Oncology, and Mao published a 2023 review in International Immunopharmacology situating Tα1 within the current era of immune-checkpoint inhibitor strategies.

7. HIV immune reconstitution in immunological non-responders

A distinct application exists in HIV patients who achieve virological suppression on antiretroviral therapy but fail to reconstitute CD4+ T-cell counts, a condition called immunological non-response. Chadwick and colleagues published a 2003 Phase II randomized, controlled, open-label pilot in Clinical and Experimental Immunology that enrolled 20 HAART-suppressed HIV patients (viral load <400 copies/mL, CD4 <200 cells/μL) and randomized 13 to Tα1 3.2 mg subcutaneously twice weekly plus HAART and 7 to HAART alone for 12 weeks. CD4, CD8, and CD45 lymphocyte subset changes at week 12 did not differ significantly between arms, but peripheral blood mononuclear cell sjTREC levels — a marker of thymic output — rose significantly in the Tα1 arm versus controls; Tα1 was well tolerated with no serious adverse events. The small sample and short duration constrain clinical interpretation, but the TREC signal provided the mechanistic anchor for subsequent immunological-non-responder work. Matteucci and colleagues provided a modern evidence review in 2017 in Future Microbiology examining Tα1 in HIV and emerging research directions. Chen and colleagues published the most current clinical evidence in 2024 in BMC Infectious Diseases, examining the role of Tα1 in restoring immune response in immunological non-responders living with HIV, establishing a contemporary evidence anchor for this indication.

8. Immunosenescence and the aging immune system

Thymic involution, the progressive reduction in functional thymic tissue that begins in early adulthood and accelerates with age, reduces the daily output of naive T cells and contributes to the immune vulnerability associated with aging. Thymosin alpha-1, derived from the thymus itself, has been studied in the context of reversing or mitigating this decline. Simonova and colleagues published the most current and comprehensive review of this angle in 2025 in the International Journal of Molecular Sciences, situating Tα1 within the biology of immunosenescence and thymic involution.

Thymosin Alpha-1 vs. Nonspecific Immune Stimulants: Key Differences

Thymosin alpha-1 modulates immune signaling through specific receptor-mediated pathways; most over-the-counter immune products work through nonspecific stimulation without receptor-targeted effects. This distinction produces meaningfully different outcomes. Compounds that broadly stimulate immune activity may worsen inflammatory conditions by amplifying cytokine production indiscriminately. Tα1's TLR9-mediated dendritic cell activation drives coordinated Th1 responses while simultaneously upregulating the IDO tolerance pathway, producing context-appropriate immune engagement rather than generalized amplification. This bidirectional regulation, documented in the Romani group's 2004 and 2006 studies in Blood, is why Tα1 has been studied in both immunodeficiency states (where the goal is to restore immune competence) and inflammatory states like sepsis (where the goal is to restore immune balance, not amplify activity). The clinical implication is that Tα1 is not simply an immune-stimulating compound and should not be evaluated using the same framework applied to nonspecific stimulants.

Biomarkers to Monitor With Thymosin Alpha-1

Thymosin alpha-1 acts on immune cell populations and downstream inflammatory markers. The most clinically relevant monitoring markers reflect T-cell dynamics, immune activation, and organ safety. Every marker below should be established at baseline before therapy begins so that changes during treatment are interpretable.

• Absolute lymphocyte count: The total count of circulating lymphocytes provides the most direct readout of Tα1's effect on T-cell pool restoration. In the COVID-19 cohort studies, lymphocytopenia reversal was the primary biomarker of clinical response. Low baseline absolute lymphocyte counts are the clearest indicator that the mechanism of Tα1 is engaged, and upward movement during therapy confirms the intended biological effect. Test at baseline and at 4- to 8-week intervals during therapy.
• CD4+ and CD8+ T-cell counts: CD4+ and CD8+ T-cell subsets are the specific populations Tα1 is designed to restore. In HIV immunological non-responders and in severe viral illness, the CD4:CD8 ratio and absolute CD4+ count are the primary outcome markers. CD4+ counts below age-adjusted norms are the clinical criterion most directly tied to candidacy for Tα1 therapy in immune-reconstitution contexts. Test at baseline and monitor throughout therapy.
• High-sensitivity CRP (hs-CRP): Thymosin alpha-1 modulates the inflammatory cytokine environment. Tracking hs-CRP alongside therapy provides an objective measure of whether systemic inflammation is changing in the intended direction. In sepsis and severe illness applications, CRP trajectories are among the most practical indicators of clinical response. Test at baseline and during therapy.
• Neutrophil-to-lymphocyte ratio (NLR): The neutrophil-to-lymphocyte ratio reflects the balance between innate immune activation and adaptive immune competence. Elevated NLR is a marker of immune imbalance and is predictive of poor outcomes in both infection and oncology settings. Tα1 therapy that restores lymphocyte populations should produce a falling NLR over time, making this a useful composite index for tracking treatment effect.
• White blood cell differential: A complete white blood cell differential provides the cellular context for interpreting lymphocyte and NLR changes. Shifts in monocyte, granulocyte, and lymphocyte fractions during therapy reflect the cellular rebalancing that Tα1 is designed to produce. Test at baseline and during therapy.
• ALT (alanine aminotransferase): In the hepatitis B and C evidence base, ALT normalization is one of the primary efficacy endpoints. Elevated ALT reflects hepatic inflammation driven by viral replication or immune-mediated hepatocyte injury. Tracking ALT over the course of therapy, alongside viral load where available, confirms whether the intended antiviral immune response is translating to reduced hepatic inflammation. Consult the GGT and ALT biomarker guide for reference range context.
• Comprehensive metabolic panel: Covers liver and kidney function baselines. Relevant for monitoring hepatic metabolism of any compounded peptide formulation and for establishing organ function context when evaluating therapy in patients with chronic viral infection or oncologic disease.
• Inflammatory markers panel (IL-6, ferritin): In sepsis and severe COVID-19 applications, IL-6 and ferritin are among the most sensitive markers of cytokine storm activity. Where available, tracking these alongside Tα1 therapy provides a more detailed picture of the inflammatory trajectory. These are particularly relevant when the primary goal is cytokine storm mitigation rather than T-cell restoration.

What Thymosin Alpha-1 Is Typically Prescribed For

Providers evaluating thymosin alpha-1 therapy typically focus on documented immune dysfunction rather than subjective wellness goals. The clearest candidacy signal is a depressed absolute lymphocyte count or CD4+ T-cell count, particularly in the setting of persistent viral infection, post-viral immune reconstitution, or age-related immune decline. In oncology adjuvant contexts, providers evaluate whether the patient's immune profile suggests impaired response to standard therapies. Patients with evidence of chronic low-grade immune activation, reflected in persistently elevated inflammatory markers alongside low lymphocyte counts, represent the population most likely to demonstrate a measurable response. Thymosin alpha-1 requires a prescription from a licensed provider, and eligibility is determined by individual clinical evaluation. Reference ranges vary by lab and individual; your provider will interpret your specific results in context.

Who Should Not Use Thymosin Alpha-1

A licensed provider will evaluate individual risk factors before prescribing. The following are generally considered contraindications or conditions requiring additional clinical scrutiny:

• Active autoimmune disease with significant immune activity, where Th1 polarization may worsen the underlying inflammatory process
• Organ transplant recipients on immunosuppressive therapy, where immune enhancement may increase rejection risk
• Pregnancy or breastfeeding, as safety has not been established in these populations
• Known hypersensitivity to thymosin alpha-1 or excipients in the compounded formulation
• Patients unwilling to undergo baseline and follow-up immune marker testing, as safe and appropriate monitoring requires objective data

This is not an exhaustive list. A licensed provider will conduct a full clinical evaluation, including baseline bloodwork, before determining eligibility. Because thymosin alpha-1 modulates rather than broadly stimulates immune function, the contraindication profile is narrower than that of nonspecific immune stimulants, but individual assessment remains essential.

Side Effects and Safety Considerations

Thymosin alpha-1 has a low adverse-event burden across published clinical trials of prescription immunomodulatory compounds. Dinetz and Lee published a comprehensive review of safety and efficacy across human clinical trials in 2024 in Alternative Therapies in Health and Medicine, documenting that the reported side effect burden across decades of trials was low. The Dominari 2020 review similarly noted the absence of significant toxicity across the broad clinical literature.

Common (reported in clinical studies):

• Injection-site reactions, including mild redness or transient soreness at the subcutaneous injection site
• Transient fatigue in the days following the first injections, consistent with immune activation
• Mild flu-like symptoms, reported infrequently in the initial weeks of therapy

Less common but reported:

• Elevated liver enzymes in patients with pre-existing hepatic disease, particularly when Tα1 produces a robust immune response directed at hepatic viral infection; this reflects intended mechanism rather than drug toxicity, but requires monitoring
• Potential for immune activation that exceeds the intended therapeutic range in patients with autoimmune predisposition; contact provider if symptoms of new or worsening inflammatory conditions develop

Is Thymosin Alpha-1 Legal?

As of April 2026, thymosin alpha-1 is not FDA-approved in the United States for any indication. Internationally, it is approved under the brand name Zadaxin in more than 35 countries, including China, Italy, and the Philippines, primarily for chronic hepatitis B. The US regulatory pathway has not included an NDA submission by the international manufacturer.

In the United States, thymosin alpha-1 was previously available through 503A compounding pharmacies as a Category 1 bulk substance. As of the February 2026 FDA reclassification, thymosin alpha-1 holds Category 2 status under the 503A bulk substance framework, meaning it remains available by prescription through licensed compounding pharmacies but under more restricted conditions. Any prescribing represents the independent clinical judgment of the provider, not an FDA-approved indication. Thymosin alpha-1 is not available in all states; availability depends on the compounding pharmacy network and applicable state laws.

Understanding Your Baseline Before Starting Thymosin Alpha-1

Because thymosin alpha-1 works by modulating specific immune cell populations, the baseline bloodwork is directly predictive of who is most likely to respond. Absolute lymphocyte count and CD4+ T-cell count tell you where the adaptive immune system is starting from. Hs-CRP and the neutrophil-to-lymphocyte ratio establish the inflammatory background. ALT establishes hepatic baseline in any patient with a history of viral hepatitis. Without these baselines, changes during therapy lack a reference point, and the clinical signal is difficult to separate from background variation. The immune system biomarker guide provides broader context on the markers that reflect adaptive immune competence, innate immune activation, and the interaction between the two.

That principle, establishing where your biology sits before making any clinical decision, is central to Superpower's approach to preventive health: objective data comes first, and every subsequent decision should be grounded in what your bloodwork actually shows.

IMPORTANT SAFETY INFORMATION

Thymosin alpha-1 is not FDA-approved for any indication in the United States. As of April 2026, it holds Category 2 status under the FDA 503A bulk substance framework following the February 2026 reclassification. Superpower Health does not prescribe, sell, compound, or facilitate access to thymosin alpha-1; this page is provided for educational and informational purposes only. Internationally, thymosin alpha-1 is approved as Zadaxin in more than 35 countries for chronic hepatitis B; this international approval status does not constitute FDA approval.

Contraindications: Active autoimmune disease with significant immune activity; organ transplant recipients on immunosuppressive therapy; pregnancy or breastfeeding (safety not established); known hypersensitivity to thymosin alpha-1 or compounded formulation excipients.

Warnings: Potential for immune activation exceeding therapeutic range in patients with autoimmune predisposition; elevated liver enzymes may occur in patients with pre-existing hepatic disease as a consequence of immune-mediated response to viral infection rather than direct drug toxicity; monitoring of absolute lymphocyte count, liver enzymes, and inflammatory markers is warranted throughout therapy.

Common side effects: Injection-site redness or soreness, transient fatigue, mild flu-like symptoms in initial weeks of therapy.

Long-term safety data from randomized controlled trials are available across four decades of clinical use; however, the compound is not FDA-approved, and long-term safety and efficacy have not been established through FDA's review process. Not available in all states. This compound is not available over the counter.

Compound reference data: PubChem CID 16132341.

Additional Questions

Are peptides legal in 2026?

The legality of specific peptides in the United States depends on their individual regulatory status. Some peptides are FDA-approved drugs, available by prescription through standard pharmacy channels. Others are available through licensed 503A compounding pharmacies by prescription, which requires a patient-specific prescription from a licensed provider. As of April 2026, thymosin alpha-1 falls into the compounded prescription category under Category 2 status. No peptide in this class is available over the counter in the United States; all access requires a valid prescription from a licensed provider.

Can you get thymosin alpha-1 without a prescription?

No. Thymosin alpha-1 is not available over the counter in any legally recognized formulation in the United States. It is accessible only by prescription through a licensed 503A compounding pharmacy, dispensed pursuant to a patient-specific prescription from a licensed healthcare provider. Any product marketed as thymosin alpha-1 without a prescription requirement in the US is operating outside the legal compounding framework and should be approached with caution.