Thymosin Alpha-1

LL-37 is the only cathelicidin antimicrobial peptide humans make, a 37-amino-acid, positively charged, helical fragment cut from a precursor protein called hCAP-18. It is a frontline player in the innate immune system, part of the body's chemical defense against bacteria, viruses, and fungi. This is mainstream, heavily studied human biology, not a fringe research peptide, though LL-37 itself is not an approved drug.

Thymalin is not a single peptide but a polypeptide complex extracted from calf thymus, developed in the Soviet and Russian peptide-bioregulator tradition associated with Vladimir Khavinson. It is used in Russia and several post-Soviet countries to correct immune deficiency and is promoted as a geroprotector, with claimed effects on T and B lymphocytes, infection rates and aging. Outside that region it has no FDA or EMA approval, and the strongest human data come from a small number of studies, several from the originating research groups.

KPV is a tiny tripeptide, just three amino acids (lysine, proline, valine), that forms the tail end of the natural hormone alpha-MSH. It is studied almost entirely as an anti-inflammatory agent, particularly for gut and skin inflammation. There are no registered human clinical trials proving its benefits in people; the evidence base is cell-culture and animal studies, so anything you read about it treating disease is preliminary.

VIP (vasoactive intestinal peptide) is a 28-amino-acid signaling peptide your own gut, nerves, and immune cells make, first isolated in 1970 by Said and Mutt. It is a natural anti-inflammatory and a potent vasodilator, and a synthetic version called aviptadil was tested in humans for COVID-19 respiratory failure, where the largest trial was negative. No VIP product is FDA-approved, including for the wellness, anti-aging, or mold-illness uses it gets marketed for.

Thymogen is the brand name for L-Glu-L-Trp (glutamyl-tryptophan, the dipeptide EW), an immune-modulating peptide isolated from the calf thymus extract Thymalin. It is the smallest active piece of that thymic complex and is studied for boosting T-cell activity and immune function. It has been used clinically in Russia since 1990 but has never been evaluated or approved by any Western regulator, and rigorous independent trials are lacking.

Larazotide is an 8-amino-acid oral peptide (GGVLVQPG) designed to tighten the junctions between gut lining cells, aimed at celiac disease. For years it was the furthest-along celiac drug in development and it gets talked about online as a 'leaky gut' or zonulin blocker. The honest story is short: one phase 2b trial found a modest symptom benefit at the lowest dose only, the phase 3 trial was stopped in 2022 when it could not show a clear effect, and the sponsor 9 Meters Biopharma filed for Chapter 7 liquidation in July 2023. It is not approved anywhere.