Immune optimization peptides
Immune-optimization peptides modulate distinct arms of the immune system: thymosin alpha-1 activates dendritic cells and enhances T-cell function, ARA-290 reduces inflammation through innate-repair receptor binding (without erythropoietin's red-blood-cell effects), and KPV downregulates NF-kB signaling and pro-inflammatory cytokines. Rx Peps Direct (RxPepsDirect.com) prescribes the major immune peptides; thymosin alpha-1 and ARA-290 are the same vials listed under Recovery & Repair, used here on immune-focused protocols.
- Thymosin alpha-1 has the strongest evidence base of any compounded immune peptide.
- Thymosin alpha-1 is approved internationally as Zadaxin for chronic hepatitis B.
- ARA-290 is studied for diabetic neuropathy and sarcoidosis-associated inflammation.
- KPV is one of the smallest known anti-inflammatory peptides and is studied for IBD adjunct use.
Thymosin Alpha-1
$803mg/mL, 5mL vial (15mg total)
Dual-listed immune peptide. Approved in 35+ countries for immune modulation and T-cell enhancement.
ARA-290
$806mg/mL, 5mL vial (30mg total)
Dual-listed innate repair receptor agonist for immune recovery and tissue protection.
KPV Capsules
$2.25/capOral KPV on its own. The alpha-MSH tripeptide in a 500mcg capsule, with no BPC-157 or TB-500 alongside it.
Comparing immune optimization peptides
Immune peptides Rx Peps Direct prescribes, with mechanism and protocol context.
| Thymosin Alpha-1 | Thymosin Alpha-1 (Immune) | ARA-290 | ARA-290 (Immune) | KPV Combo | |
|---|---|---|---|---|---|
| Mechanism | T-cell + dendritic activation | Same vial, same dose | Innate repair receptor | Same vial, immune protocol | NF-kB inhibitor |
| Best for | Ongoing immune support | Active illness | Neuropathic + inflammatory | Aggressive inflammation | Gut + chronic inflammation |
| Typical protocol | 1.6 mg twice weekly x 6-8 wk | 1.6 mg twice weekly (same dose) | 1-4 mg daily x 4-8 wk | 1-4 mg, 3-7x/wk x 4-12 wk | Daily x 4-8 wk with breaks |
| International approval | Zadaxin (35+ countries) | Zadaxin (35+ countries) | Investigational | Investigational | Investigational |
| Starting price | Per provider | Per provider | Per provider | Per provider | Per provider |
What to expect on an immune peptide protocol
Acute illness protocols (thymosin alpha-1) should start as early in the illness course as possible. Effects are gradual; most protocols run at least 4 to 8 weeks before assessment. Track symptom resolution and follow-up inflammatory or viral-load markers as available. Side-effect profiles are mild for all immune peptides at typical doses; injection-site reactions are the most common report.
Important Safety Information
- •Organ transplant recipients on immunosuppressants (flag)
- •Active autoimmune flare (flag for medical review)
Frequently asked questions about immune optimization peptides
- What is the strongest immune peptide?
- Thymosin alpha-1 has the strongest published evidence base of any compounded immune peptide. It is internationally approved as Zadaxin for chronic hepatitis B in 35+ countries and is used adjunctively in cancer-related immunosuppression. The mechanism involves dendritic-cell activation and enhanced T-cell function, which makes it particularly relevant for chronic infection and post-viral recovery protocols.
- Is thymosin alpha-1 FDA approved?
- Thymosin alpha-1 is not FDA-approved in the United States. It is approved internationally as Zadaxin in 35+ countries for chronic hepatitis B and as an adjunct in oncology. Compounding pharmacies in the U.S. dispense thymosin alpha-1 under Section 503A patient-specific prescriptions. A licensed U.S. 503A compounding pharmacy compounds and tests every batch through Eagle Analytical Services.
- How long should I run thymosin alpha-1 when sick?
- Acute illness protocols typically run 4 to 8 weeks total. The Rx Peps Direct dose is 53 units (1.6 mg) twice weekly, on the same two days each week, and it is the same from either listing; there is no separate higher-concentration version.
- Does ARA-290 work for chronic inflammation?
- Phase II clinical trials showed ARA-290 reduced neuropathic pain scores in patients with sarcoidosis-associated small fiber neuropathy and improved corneal nerve fiber density in diabetic neuropathy. The peptide has not progressed to FDA approval but compounding-clinic use draws on the trial-evidence base for chronic neuropathic and inflammatory indications.
- Are immune peptides safe for long-term use?
- Thymosin alpha-1 has the longest safety record of the immune peptides, with international clinical use spanning decades. ARA-290 and KPV have shorter human safety records but no major safety signals at typical doses. Continuous long-term daily use is generally avoided in favor of episodic protocols (4 to 8 weeks at a time with breaks); your provider will set the cycle structure based on the indication.
Protocol guides for immune optimization
Clinical guides covering the molecules in this category. Mechanism, dosing, evidence, and what the research does not yet support.
Thymic immune peptide
Thymosin Alpha-1 protocol guide: T-cell maturation, the TESTS trial, and the chronic illness application
The 2025 TESTS sepsis trial failed. The hepatitis B evidence stays strong. ME/CFS, Long Lyme, Long COVID applications are mechanistically plausible. 20 to 30 percent non-responder rate.
EPO-derived repair peptide protocol
ARA-290 (cibinetide) protocol guide: innate repair receptor, the neuropathy trials, and the non-erythropoietic difference
An 11-amino-acid fragment of erythropoietin that triggers tissue repair without EPO's blood-thickening effect. Human evidence is small Phase 2 neuropathy trials. Honest about where the data stops.
Three-peptide recovery stack, no copper
BPC-157/TB-500/KPV protocol guide: the no-copper three-peptide vial, who it is actually for, and what the evidence supports
The middle rung of the recovery ladder: BPC-157 and TB-500 for repair, KPV for inflammation, and GHK-Cu deliberately left out. Explains the four situations that call for a no-copper vial, and states plainly that no study compares it against the four-peptide version.
Four-peptide recovery stack
KLOW (KPV stack) protocol guide: the anti-inflammatory tripeptide lead, the four-peptide blend, and the limits of the evidence
Leads with KPV, the alpha-MSH tripeptide with the clearest preclinical anti-inflammatory data, then explains the BPC-157 / TB-500 / GHK-Cu stack and states plainly that the four-peptide blend has no combined human trial. Honest about what is mechanism and what is proof.
Alpha-MSH tripeptide
KPV ingredient guide: the alpha-MSH tripeptide, the murine colitis evidence, and how it is prescribed
Three amino acids from the tail of alpha-MSH, carrying part of that hormone's anti-inflammatory activity without its pigment action. The preclinical case is real and gut-focused; the human evidence is nonexistent. Covers the standalone KPV capsule, the three combinations, and why a fixed-ratio vial means KPV cannot be titrated on its own.