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Immune and respiratory research.
A small category where the most interesting compound is approved almost everywhere except here.
3 compounds tracked in this category
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In theory, this class is designed to restore immune function that declines with age, supplying thymic peptides to support T-cell maturation as the thymus involutes and immune diversity narrows. The underlying observation is real and well documented. Whether supplying these peptides meaningfully reverses it in humans is the part the evidence does not currently answer.
Unmarked, FDA approved° legal over the counter† under FDA review, not yet permitted* not FDA approved‡ documented safety concern
| Compound | What is known |
|---|---|
| Thymosin Alpha-1* | Removed from Category 2 in April 2026 but not moved to Category 1. Approved in some other countries, not the US. |
| VIP* | Unapproved. Limited data outside niche indications. |
| Vitamin B12 | Approved and widely available. Oral supplementation is legal and unremarkable. |
The science behind this category
This is the substantive entry. It is a thymic peptide with a real mechanism in T-cell maturation, and it is approved in a number of countries for hepatitis B and as an adjunct in other indications. It is not approved in the United States. It was placed in Category 2 in 2023 and removed in April 2026 without being moved to Category 1, so it occupies the same limbo as CJC-1295, neither prohibited nor authorised.
A drug approved in another country has not been reviewed by FDA. Regulatory agencies reach different conclusions on the same data, and approval abroad does not create a US pathway. It does mean the compound has a real safety record somewhere, which distinguishes it from the preclinical entries on this site. But it does not make it legal or reviewed here.
The category rests on a real observation: the thymus involutes with age, T-cell diversity narrows, and immune function declines. Whether supplying thymic peptides meaningfully reverses that in humans is a separate question, and one the evidence does not currently answer.
Vasoactive intestinal peptide has genuine physiological roles in immune and respiratory regulation. Its use outside narrow research and specific clinical contexts is not supported by controlled data.
Included here in most catalogues, though it belongs to a different conversation entirely. It is approved, widely available, well understood, and unremarkable. Deficiency is worth testing for and correcting. Supplementation in the absence of deficiency has little to recommend it.
Understanding a category is the first step. Whether any of it applies to you is a question for a licensed physician who knows your history.
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