§ — Researched for · Immune function & inflammation
Thymosin alpha-1 is the only immune peptide with randomized trials behind it, and it is approved in over 30 countries — but not by the FDA or EMA. LL-37 and KPV remain at animal or early-phase stage; FDA proposed in 2026 not to list KPV, and will reconsider LL-37 in early 2027.
Reviewed September 2026 · Sources: FDA, EMA
02 — What is being studied
Research here splits between immune modulation and antimicrobial defence. Thymosin alpha-1 has been studied in sepsis, hepatitis B and as a vaccine adjuvant, with randomised trials and mortality endpoints in critical care. LL-37 is a human cathelicidin studied for direct antimicrobial activity and wound colonisation; KPV is an alpha-MSH fragment studied for mucosal inflammation in colitis models.
The endpoints under study are infection rates, mucosal healing and inflammatory markers rather than the general 'immune support' language used in marketing. Human data outside thymosin alpha-1 is early-phase or absent, and the concept of boosting an immune system that is not deficient has no measured endpoint at all. FDA has scheduled LL-37 for reconsideration in early 2027, so the regulatory picture in this group is expected to move.
03 — The table
| Peptide | Researched for | Evidence | Regulatory status | As of |
|---|---|---|---|---|
| Thymosin alpha-1 | Hepatitis B and C adjunct, sepsis, vaccine response, cancer adjunct, COVID-19. | B | Not FDA-approved. Placed in 503A Category 2 in 2023. Current category must be verified against the FDA bulks list before publication. | 2026-09-06 |
| BPC-157 | Tendon, ligament and muscle healing; gastrointestinal mucosal protection; ulcerative colitis (the indication FDA reviewed in 2026). | C | Not FDA-approved for any use. Placed in 503A Category 2 in 2023 over immunogenicity and impurity concerns; removed from Category 2 on April 15, 2026 after nomination withdrawal — which is not a listing in Category 1. Reviewed by the Pharmacy Compounding Advisory Committee on July 23, 2026; FDA proposed not to add it to the 503A Bulks List. Compounding remains outside the 503A exemption until rulemaking concludes. | 2026-09-06 |
| KPV | Inflammatory bowel disease, skin inflammation. | C | Not FDA-approved. Reviewed by PCAC on July 23, 2026; FDA proposed not to add it to the 503A Bulks List. | 2026-09-06 |
| LL-37 | Chronic wound infection, biofilm disruption, venous leg ulcers. | C | Not FDA-approved. Previously withdrawn from review; FDA has announced a further PCAC meeting before the end of February 2027 to reconsider it for the 503A Bulks List. | 2026-09-06 |
04 — Per peptide
Regulatory status · United States · as of September 2026
Not FDA-approved. Placed in 503A Category 2 in 2023. Current category must be verified against the FDA bulks list before publication.
Source: FDA 503A Bulks List · PCAC meeting records · verified September 2026
Researched forHepatitis B and C adjunct, sepsis, vaccine response, cancer adjunct, COVID-19.
Full profile: Thymosin alpha-1 →Regulatory status · United States · as of September 2026
Not FDA-approved for any use. Placed in 503A Category 2 in 2023 over immunogenicity and impurity concerns; removed from Category 2 on April 15, 2026 after nomination withdrawal — which is not a listing in Category 1. Reviewed by the Pharmacy Compounding Advisory Committee on July 23, 2026; FDA proposed not to add it to the 503A Bulks List. Compounding remains outside the 503A exemption until rulemaking concludes.
Source: FDA 503A Bulks List · PCAC meeting records · verified September 2026
Researched forTendon, ligament and muscle healing; gastrointestinal mucosal protection; ulcerative colitis (the indication FDA reviewed in 2026).
Full profile: BPC-157 →Regulatory status · United States · as of September 2026
Not FDA-approved. Reviewed by PCAC on July 23, 2026; FDA proposed not to add it to the 503A Bulks List.
Source: FDA 503A Bulks List · PCAC meeting records · verified September 2026
Researched forInflammatory bowel disease, skin inflammation.
Full profile: KPV →Regulatory status · United States · as of September 2026
Not FDA-approved. Previously withdrawn from review; FDA has announced a further PCAC meeting before the end of February 2027 to reconsider it for the 503A Bulks List.
Source: FDA 503A Bulks List · PCAC meeting records · verified September 2026
Researched forChronic wound infection, biofilm disruption, venous leg ulcers.
Full profile: LL-37 →05 — What the data does not show
General immune 'boosting' in healthy adults and immune rejuvenation with age have not been shown.
06 — Questions for your physician
Listing in the registry is not an endorsement of any substance or protocol, and it is not a statement that a treatment is approved.
Reviewed September 2026 · Sources: FDA, EMA
This page reports on the state of research and regulation for orientation. It is not medical advice, not a recommendation for or against any substance, and not an offer. Regulatory status changes; the date shown is the date of our last verification. Discuss any treatment with a licensed physician.