- Last reviewed
- 28 Apr 2026
- Sources cited
- 10
- Residues
- 28
Thymosin Alpha-1
Last verified: 2026-04-24
At a glance
| Also known as | Tα1, TA1, thymalfasin, Zadaxin (brand name), prothymosin α fragment |
| Class | Synthetic 28-amino-acid peptide, derived from the prothymosin alpha protein naturally produced in the thymus gland |
| Typical route | Subcutaneous injection |
| Plasma half-life | ~2–3 hours; peak serum concentration within 2 hours; plasma levels return to baseline within 24 hours |
| Duration of effect | Immune signalling effects persist 48–72 hours through secondary messenger cascades |
| Molecular weight | 3,108 Da |
| Sequence | Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn (28 amino acids, N-terminally acetylated) |
What it is
This is the most clinically-established peptide in this encyclopedia. Thymosin Alpha-1 is not a research-chemical with thin human evidence — it’s an approved medicine in 35+ countries, including much of Europe, Asia, and Latin America. It has a 30+ year clinical track record with over 11,000 patients across more than 30 clinical trials. It holds FDA orphan drug designation (for specific rare conditions — malignant melanoma, chronic active hepatitis B, DiGeorge anomaly with immune defects, hepatocellular carcinoma) but does not have general FDA approval. The UK, EU, and US all lack full regulatory approval.
It was first isolated from the thymus gland in 1977, then synthesised and developed as a pharmaceutical. The thymus gland — which atrophies with age and is severely compromised by stress, chemotherapy, and HIV — produces thymosin family peptides that regulate T-cell development and immune function. Tα1 is the most clinically useful member of that family.
It’s used primarily for immune regulation: hepatitis B and C treatment, adjunctive cancer immunotherapy, sepsis, severe infections, and increasingly for post-viral immune dysregulation (long COVID, chronic fatigue syndrome, post-infectious autoimmune states). In the biohacker space it’s used for general immune optimisation, post-infection recovery, and immune resilience in ageing populations.
The evidence base is genuinely strong compared to everything else we’ve documented. That changes the tone of the discussion.
Mechanism
Tα1’s mechanisms are unusually well-characterised — because it has been a real medicine in development for over 40 years:
- Toll-like receptor (TLR) activation. Tα1 binds to TLR3, TLR4, TLR9, TLR2, and TLR7 on immune cells. Through TLR2/9 pathways it activates IRF3 and NF-κB signalling; through TLR2 it activates p38 MAPK; through TLR7 it activates MyD88 signalling. The net effect: enhanced innate and adaptive immune responses.1
- T-cell maturation and differentiation. Acts on precursor T-cells, promoting differentiation into mature CD8+ cytotoxic T lymphocytes. CD8+ T cells recognise virally-infected or low-MHC-I expressing cells and release IFN-γ to control viral replication.
- NK cell activation. Increases natural killer cell activity — first-line innate immune defence against viruses and tumour cells.
- Dendritic cell priming. Enhances antigen presentation capacity of dendritic cells, improving adaptive immune response to infections and vaccines.
- Cytokine modulation. Shifts Th1/Th2 balance toward Th1, which is pro-viral-clearance. Reduces pro-inflammatory cytokine storm in sepsis contexts while enhancing appropriate targeted immune response.
- Immune homeostasis restoration. In chronically dysregulated immune states (long COVID, ME/CFS, post-chemotherapy), Tα1 appears to restore balance rather than simply boosting — reduces exhausted T-cell populations, restores NK cytotoxicity, normalises cytokine patterns.2
The distinction that matters: Tα1 is an immune modulator, not an immune booster. It restores appropriate immune function rather than blindly amplifying it. This matters for autoimmune considerations.
Routes of administration
Subcutaneous injection
| Bioavailability | High; standard subQ efficiency. Peak serum levels within 2 hours. |
| Onset | Immune signalling effects detectable within hours; clinical benefit accumulates over weeks |
| Duration | Plasma half-life 2–3 hours; immune effects persist 48–72 hours per dose |
| Typical dose (this route) | 1.6–3.2 mg per dose, 2–3× weekly |
| Equipment | Insulin syringe (U-100), BAC water (or supplied sterile water for Zadaxin), alcohol wipes |
| When this route makes sense | The only route in clinical use. All approved indications use subQ injection. |
The only clinically-validated route. Zadaxin (the approved pharmaceutical formulation) is supplied as lyophilised powder with sterile water for reconstitution, delivered subQ. Research-chemical Tα1 uses the same route.
Injection technique matters — 4–6mm needle depth at 45-degree angle, abdomen or outer thigh, adequate adipose tissue. Too shallow (intradermal) causes local irritation and poor absorption; too deep (intramuscular) changes pharmacokinetics.
Intramuscular injection
| Bioavailability | Viable but not clinically preferred |
| Onset | Similar to subQ |
| Typical dose (this route) | Same dose range |
| When this route makes sense | Rarely. Zadaxin labelling specifies subcutaneous; IM changes PK and is not the validated route. |
Oral / sublingual / intranasal
| Bioavailability | Essentially none oral. Intranasal explored experimentally but not standard. |
| Typical dose (this route) | Not recommended |
| When this route makes sense | Never in standard clinical use. |
Tα1 is a 28-residue peptide and does not survive GI transit. Intranasal formulations have been explored in research settings but are not the clinical route. Oral Tα1 products are non-functional.
Cross-route comparison
SubQ is the clinically-validated route. No meaningful alternative exists. This is consistent with how the compound is used in its approved indications in 35+ countries.
What the evidence says
Honest summary: this is the best-evidenced peptide in this encyclopedia. 30+ years of clinical use, 35+ countries approved, 11,000+ patients across 30+ trials, orphan drug designation in the US. The evidence base is meaningfully different in kind from the research-chemical peptides.
Approved clinical indications (35+ countries):
- Chronic hepatitis B — the most extensively studied indication since 1991. Multiple randomised controlled trials demonstrating virologic response and ALT normalisation. Note: the review literature acknowledges Tα1 for HBV is “now obsolete in the era post-discovery of direct antiviral agents” — meaning modern antivirals are better, not that Tα1 doesn’t work.3
- Chronic hepatitis C — also approved; similar mechanism, also superseded by direct-acting antivirals
- Immune enhancement — broad approved indication in multiple jurisdictions for various immunodeficient states
Orphan drug indications (US FDA):
- Malignant melanoma
- Chronic active hepatitis B
- DiGeorge anomaly with immune defects
- Hepatocellular carcinoma
Sepsis: A large multicentre single-blinded RCT across 6 Chinese tertiary hospitals showed 9% lower mortality with Tα1 (1.6 mg twice daily for 5 days) vs standard care. This is substantial evidence for a compound.3
Cancer immunotherapy adjunct: Multiple trials demonstrating reduced chemotherapy toxicity and improved immune function across various malignancies. Trial sizes vary.
COVID-19: Emergency use during the 2020–2022 pandemic. Results mixed — Tα1 mitigated cytokine storm in blood cells from COVID-19 patients in one study,4 but another RCT found no beneficial effect on restoring CD4+/CD8+ T lymphocyte counts in COVID-19 patients.5 Honest read: possible benefit in specific subsets, not a reliable intervention across all COVID patients.
Long COVID / Post-Acute Sequelae (PASC):
- 2023 ex vivo study showed Tα1 restored appropriate immune response in lymphocytes from long COVID patients with chronically altered immune function. In PASC patients with systemic symptoms (asthenia, fever, myalgia, joint pain), Tα1 treatment decreased exhausted T-cell populations.2
- 51% of long COVID patients have ME/CFS — mechanistically relevant.
ME/CFS:
- Small controlled trials showing Tα1 can restore NK-cell activity and cytokine equilibrium
- One study (n=12) reported reduced fatigue and enhanced immune function after 8–12 weeks of Tα1 therapy
- Evidence remains limited — small sample sizes, not large RCTs
Community evidence (biohacker use):
- Used for general immune resilience, post-illness recovery, chronic low-grade infections
- Less polarised response pattern than most peptides — more users report at least some benefit, consistent with its documented immunomodulatory mechanism
- Often deployed in longevity stacks as the “immune pillar” alongside metabolic (MOTS-c) and cellular (Epithalon) pillars
Typical use patterns
Observations, not recommendations. Note that for Tα1, the clinical-use dosing is actually well-established, unlike most peptides in this encyclopedia.
Dose (clinical, from Zadaxin labelling and trials):
- Hepatitis B/C: 1.6 mg (900 mcg/m²) subQ twice weekly
- Sepsis: 1.6 mg twice daily for 5 days (acute protocol)
- Cancer adjunctive: varies by protocol; 1.6 mg 2–3× weekly common
- Long COVID / ME/CFS: 1.6 mg 2× weekly, 8–12 week cycles (from small trial data)
Dose (community/biohacker):
- Standard: 1.6 mg subQ 2–3× weekly
- Higher-intensity: 3.2 mg 2× weekly
- Maintenance after initial course: 1.6 mg 1–2× weekly
Timing:
- Morning is typical; no strong evidence on optimal time
- Injection timing relative to meals doesn’t matter
Cycle:
- Acute/treatment courses: 8–12 weeks is the standard duration in clinical trials
- Maintenance/longevity use: ongoing low-frequency dosing is documented as safe across 6 months to several years without significant toxicity or immune exhaustion
- Post-infection recovery: typically 4–12 weeks following acute illness
Tα1 is one of the few peptides where continuous long-term use is reasonably well-characterised and not reflexively discouraged. The approved-medicine status gives real-world long-term safety data most biohacker peptides don’t have.
Stacking:
- Thymalin — related thymic peptide, sometimes stacked with Tα1 for layered immune effect
- LL-37 — another antimicrobial/immunomodulatory peptide; complementary mechanism
- BPC-157 — general healing + immune; commonly run together post-surgery or post-infection
- Epithalon + MOTS-c + Tα1 — the “longevity trinity” in anti-ageing protocols: telomere/circadian + metabolic + immune
- Vaccine timing — Tα1 is sometimes used around vaccination to enhance response, based on its dendritic cell/T-cell mechanisms. Clinically explored in hepatitis B vaccination contexts.
For sensitive systems
This is where Tα1 gets genuinely interesting for the Rest Reclaimed audience. Long COVID, ME/CFS, post-viral syndromes, autoimmune conditions, chronic infection patterns — these are exactly the use-cases the research community is actively exploring for Tα1.
Start dose. 800 mcg (half standard dose) subQ, 1× weekly for 2 weeks. If tolerated, increase to 1.6 mg 1× weekly, then 1.6 mg 2× weekly.
Ramp. Slow. Tα1 modulates immune function broadly, and sensitive users are often the users where immune reactions matter most. Do not rush.
Expected adjustment profile:
- Mild injection site reactions (most common, transient)
- Transient fatigue in the first 1–2 weeks — as immune function shifts, some users report a “feeling under the weather” period before settling into benefit
- Mild flu-like symptoms (fever, muscle aches) in rare cases, particularly at higher doses
- Temporary symptom flare in autoimmune users — see the autoimmune section below; genuinely important caveat
- No documented histamine/mast cell provocation — Tα1 is not mast-cell active
What’s not normal and warrants stopping: persistent fever, severe flu-like symptoms lasting more than a few days, clear worsening of autoimmune symptoms, new immune-mediated symptoms.
Why Tα1 may be the single most relevant peptide for the Rest Reclaimed audience:
- Long COVID and ME/CFS evidence exists — not large trials, but real studies showing restoration of immune homeostasis, reduced exhausted T-cell populations, improved NK activity
- Post-viral syndromes fit the mechanism — Tα1 restores appropriate immune function after chronic viral perturbation
- HPA-axis dysregulation often overlaps with immune dysregulation — Tα1’s immune-balancing effect is mechanistically relevant even where autoimmunity isn’t diagnosed
- Longest clinical track record of any peptide here — 40+ years of human use gives safety confidence that research chemicals can’t match
- MCAS overlap — immune dysregulation is central to MCAS; Tα1’s modulatory (not boosting) effect is theoretically well-suited, though no specific MCAS trials exist
The autoimmune consideration (genuinely important)
Tα1 enhances immune responses broadly. In users with pre-existing autoimmune conditions, this creates a theoretical risk of symptom flare.
What the evidence shows:
- Clinical evidence for autoimmune flare risk is “limited, but caution is warranted” — per the literature
- Paradoxically, long-term users often report reduced autoimmune flare frequency — consistent with the “modulation not boosting” framing, where immune homeostasis rather than amplification is the actual effect
- The risk is probably real for some users with some autoimmune conditions, and probably low in aggregate
- Use in diagnosed autoimmune disease should be under physician supervision — this isn’t the peptide to trial alone against an active autoimmune flare
Practical guidance:
- Stable autoimmune disease on treatment: reasonable to consider, starting low and monitoring closely
- Active autoimmune flare: defer until stable
- Undiagnosed autoimmune pattern (suspected Hashimoto’s, suspected lupus-spectrum, etc): proceed only with appropriate testing and ideally clinical input
- Concurrent immunosuppressants (biologics, methotrexate, steroids): Tα1 may counteract their effect. Not a contraindication in all cases, but requires clinical coordination.
What to have on hand:
- Baseline immune markers if possible (CBC with differential, inflammatory markers)
- Wearable data for sleep, HRV, RHR — Tα1’s effects on energy and recovery often show up in these metrics before subjective clarity emerges
Interactions worth considering:
- Immunosuppressants (biologics for autoimmune disease, chemotherapy, high-dose steroids): Tα1 counteracts mechanism. Clinical coordination needed.
- Immunotherapy for cancer (checkpoint inhibitors, CAR-T): mechanistic complement but complex; oncology input needed, not self-directed use
- Vaccines: potential enhancement; commonly timed around vaccination in clinical practice
- Antibiotics/antivirals for acute infection: complementary; Tα1 used adjunctively in sepsis protocols
- LDN: different mechanism, commonly combined in integrative medicine for chronic illness
- Standard peptides (BPC, TB, KPV): no documented interactions; compatible stacking
Long COVID / PASC practical note: for users exploring Tα1 for long COVID, the 2023 evidence suggests 8–12 weeks is the minimum reasonable trial period. Effects are gradual; expecting dramatic early improvement will disappoint. Track HRV, sleep quality, PEM threshold, and post-exertional recovery rather than subjective “feeling better” assessments.
PMDD note: no specific PMDD research. Immune-modulatory mechanism theoretically relevant given emerging research on neuroinflammation and luteal-phase immune activation in PMDD, but speculative.
Reasonable expectations
Onset. Clinical effects emerge over weeks, not days. Immune markers may shift within 2–4 weeks; subjective benefit typically reported at 4–8 weeks; meaningful clinical improvement (for conditions being treated) at 8–12 weeks. This is a slow, cumulative compound.
Response rate. Higher than most peptides in this encyclopedia because the evidence base is stronger. For approved indications (hepatitis B, sepsis adjunct), clinical trial response rates are documented at meaningful levels. For off-label use (long COVID, ME/CFS, general immune enhancement), community response rates are harder to estimate but reports are more consistently positive than most peptides.
What the literature actually supports.
- Chronic hepatitis B treatment (approved indication, 30+ years of use): strong evidence
- Sepsis mortality reduction (large RCT): strong evidence
- Cancer chemotherapy adjunct (multiple trials): good evidence
- Post-viral immune restoration including long COVID: emerging evidence, promising
- ME/CFS immune function improvement: limited but positive small-trial data
- Vaccine response enhancement: modest supporting evidence
- General longevity/anti-ageing immune benefit: mechanistically plausible, not directly demonstrated
What not to expect.
- A cure for autoimmune disease. Tα1 modulates; it does not treat established autoimmune pathology in the way conventional DMARDs do.
- Rapid subjective change. Unlike Semax’s 30-minute focus hit, Tα1 works on timescales the immune system operates on — weeks.
- A substitute for hepatitis antiviral therapy, chemotherapy, or standard immunotherapy for cancer. Adjunctive, not replacement.
- Miracle results for long COVID or ME/CFS. Results are promising but modest; realistic expectation is partial improvement in a subset of users.
- Protection against all infections. Tα1 supports immune function; it doesn’t make you immortal to pathogens.
Cost
Approximate as of April 2026. Tα1 is unusual in this encyclopedia — both research-chemical and pharmaceutical (Zadaxin) forms exist, with very different prices.
Research-chemical grade (UK research-chemical market)
| 5 mg lyophilised vial | £35–70 |
| 10 mg vial (bulk) | £70–130 |
| Cost per 8-week cycle (1.6 mg × 2/week = 25.6 mg total) | ~£180–330 |
| Cost per month, long COVID protocol (1.6 mg × 2/week) | ~£100–180 |
| Cost per month, maintenance (1.6 mg × 1/week) | ~£50–90 |
Zadaxin (approved pharmaceutical, where available)
| Zadaxin 1.6 mg vial | £50–150 per vial (varies widely by jurisdiction; often imported) |
| Monthly cost at 1.6 mg × 2/week | ~£400–1,200 |
The pharmaceutical (Zadaxin) costs 3–5× more than research-chemical Tα1 for the same compound. In the UK, Zadaxin is not routinely prescribed because it’s not MHRA-approved for general use — specific-indication use would be under named-patient or specialist consultant pathways. Most UK users accessing Tα1 do so as research-chemical grade.
Reconstitution
5 mg lyophilised Tα1 (research-chemical):
- Reconstitute in 2.5 mL bacteriostatic water → 2 mg/mL
- 1.6 mg dose = 0.8 mL = 80 IU on a U-100 insulin syringe
- 3.2 mg dose = 1.6 mL
Alternative — 5 mg in 5 mL BAC water → 1 mg/mL:
- 1.6 mg dose = 1.6 mL
- Easier precise dosing; larger injection volume
Zadaxin: comes with its own supplied sterile water. Follow package insert instructions (typically 1 mg in 1 mL).
Reconstituted Tα1 is stable in BAC water, refrigerated, for ~30 days. Lyophilised Tα1 is stable at room temperature for months; refrigeration extends shelf life. Avoid vigorous shaking — swirl gently.
Areas of concern ⚠
Autoimmune flare risk (the main caveat)
Tα1 enhances immune responses. In users with autoimmune disease, this creates a theoretical risk of symptom flare.
What the evidence shows:
- Clinical evidence for flare risk is “limited but caution warranted”
- Long-term users often report reduced autoimmune flare frequency — consistent with immune modulation rather than amplification
- Risk is probably real for some users with some conditions; not universal
Practical implication:
- Stable autoimmune disease on treatment → reasonable to consider with monitoring
- Active autoimmune flare → defer
- Undiagnosed autoimmune patterns → investigate before starting
- On immunosuppressants → requires clinical coordination
Safety profile is genuinely favourable
Unlike most peptides in this encyclopedia where “safety is assumed because nothing bad has been documented in small samples,” Tα1 has 30+ years of documented clinical safety. Mild injection site reactions (most common), transient fatigue, occasional flu-like symptoms. Rarely: fever, muscle aches, nausea in combination treatments (often attributable to the co-administered agent).
No serious adverse events in approved-indication clinical use. This is an unusually reassuring safety picture compared to research-chemical peptides.
Quality and sourcing matter more for Tα1 than for many peptides
- The molecule is complex (28 amino acids, N-terminally acetylated) — synthesis quality affects product purity and potency
- Research-chemical Tα1 varies; some suppliers are notably more reliable than others
- Genuine Zadaxin is expensive but has pharmaceutical quality control
- Counterfeit Zadaxin exists in markets where authentic product is expensive
- Storage: lyophilised room-temp stable; reconstituted refrigerated 30 days
Long-term safety is actually characterised
- Users tracked 6 months to several years in clinical contexts without significant toxicity or immune exhaustion
- This is unique among peptides in this encyclopedia — most have no long-term human data at all
- The main long-term caveat is autoimmune flare risk, not general toxicity
Cost vs the research-chemical tier
- Zadaxin is 3–5× more expensive than research-chemical Tα1
- For users wanting pharmaceutical-grade quality assurance, this is a meaningful premium
- For users comfortable with research-chemical-grade, savings are substantial
- This tier choice doesn’t exist for most peptides in this encyclopedia
Populations where caution is warranted
- Active autoimmune flare — defer until stable
- Undiagnosed autoimmune pattern — investigate before starting
- Concurrent immunosuppressants (biologics, methotrexate, high-dose steroids): clinical coordination needed
- Active cancer on checkpoint inhibitor therapy — specialist oncology input required
- Organ transplant recipients — would theoretically work against immunosuppression required to prevent rejection; clinical contraindication
- Pregnancy and breastfeeding — insufficient data; default contraindication
- Under 18 — limited paediatric data outside specific clinical indications
FDA / regulatory status
| Jurisdiction | Status | Last verified |
|---|---|---|
| US (FDA) | Not approved for general use. Orphan drug designation for malignant melanoma, chronic active hepatitis B, DiGeorge anomaly with immune defects, hepatocellular carcinoma. FDA placed additional compounding restrictions in 2023. | 2026-04-24 |
| UK (MHRA) | Not licensed as medicine. Not a controlled substance. Sold as research chemical with “not for human consumption” labelling. Zadaxin is not routinely available in the UK. | 2026-04-24 |
| EU (EMA) | Not approved centrally. Some EU member states have national approvals. | 2026-04-24 |
| Approved countries (Zadaxin) | 35+ countries including China, Italy, India, South Korea, the Philippines, multiple Latin American countries, Middle East, Southeast Asia. Approved indications: chronic hepatitis B, chronic hepatitis C, immune enhancement. | 2026-04-24 |
| WADA (sport) | Not explicitly listed as prohibited. Immunomodulatory peptides occupy a grey zone in anti-doping; athletes subject to testing should check current WADA list rather than rely on this summary. | 2026-04-24 |
Narrative. Tα1’s regulatory story is genuinely unusual for this encyclopedia. It’s a real medicine in 35+ countries, holds specific orphan drug designations in the US, has 30+ years of clinical evidence — but lacks full approval in the UK, EU centrally, or US general use. The April 2026 PCAC meeting does not include Tα1 — it’s not on that list, which is a separate regulatory track from the research-chemical reclassifications.
For UK readers: Tα1 is legally available as a research chemical from UK-based suppliers. Not a controlled substance. Personal possession is not an offence. Sale for human consumption is not permitted. Named-patient importation of Zadaxin through specialist pathways is theoretically possible but not standard practice.
What to track in Peptrax
Thymosin α-1 is taken on the immunomodulatory thesis — for chronic infection load, post-viral recovery, autoimmune flare frequency, or general immune resilience — and the signal is necessarily slow. The honest tracking question is whether illness pattern actually changed over months, not weeks. A weekly note covering colds, flu-like episodes, autoimmune flares (joint, skin, gut, fatigue — depending on your condition), and any infection-related downtime is the readout that lets a 6-month cycle answer that question.
For users running Tα1 for a specific condition (chronic Lyme, post-COVID, hepatitis context, autoimmune), the symptom-set is condition-specific and the relevant log is whatever is actually moving — Lyme symptom rotation, PEM frequency in long COVID, joint counts, GI flares. A generic “felt better” rating is the wrong tool here; structured symptom tracking that matches the condition is what makes the compound’s effect visible against the underlying disease’s own variability.
Cycle structure is unusually long compared to most peptides — months of continuous dosing rather than 2–4 week cycles — and the cost reflects that. Logging total spend per month against the symptom log is the honest cost-vs-effect view. The compound is also where regulatory framing matters most for the reader: Tα1 is an approved medicine in 35+ countries, and a meaningful conversation with a UK or US clinician about whether named-patient importation is appropriate becomes possible only with months of structured symptom data.
For personal tracking and informational purposes only — not medical advice.
Sources
- Thymosin α1 and Its Role in Viral Infectious Diseases: The Mechanism and Clinical Application — PMC 2023
- Thymosin alpha 1 restores the immune homeostasis in lymphocytes during Post-Acute sequelae of SARS-CoV-2 infection — PMC 2023
- Thymosin alpha 1: A comprehensive review of the literature — PMC 2020 (primary source, read in full via WebFetch)
- Thymosin Alpha 1 Mitigates Cytokine Storm in Blood Cells From COVID-19 Patients — Open Forum Infectious Diseases 2020
- Thymosin Alpha-1 Has no Beneficial Effect on Restoring CD4+/CD8+ T Lymphocyte Counts in COVID-19 Patients — Frontiers in Immunology 2021
- Pharmacokinetics of thymosin alpha1 after subcutaneous injection — PubMed
- Thymalfasin (Thymosin Alpha 1) to Treat COVID-19 Infection — ClinicalTrials.gov NCT04487444
- Thymosin alpha-1 — AJHP 2001
- Thymosin alpha 1: A comprehensive review — WJG 2020
- Zadaxin (Thymalfasin) — RxList prescribing information