Clinical Takeaway — Series Overview
What You Need to Know Before Reading Further
FDA-Approved on This List
1 of 17
(PT-141 / Bremelanotide)
Phase 3 Completed — Failed
1 of 17
(AOD-9604 — no efficacy)
Zero Published Human Trials
5 of 17
(MOTS-C, KPV, Epitalon, LL-37, MT-II)
Phase 1–2 Data Only
4 of 17
(CJC-1295, Ipamorelin, GHRP-2/6)
Category 2 means a compounding pharmacy cannot legally make it— it does not mean the compound is dangerous, and it does not mean it is safe.
RFK Jr.'s proposed reclassification to Category 1 allows legal compounding with a prescription. It does not constitute FDA approval, and does not change the evidence base one iota.
The wellness claims being marketed for most of these peptides — tissue repair, cognitive enhancement, longevity, fat loss —have not been tested in controlled human trials for any of these compounds.
The FDA's three-phase approval standard exists because animal studies routinely look better than human outcomes. Most of these compounds have never left the animal data phase.
After my recent piece on my own low-dose tirzepatide use brought hundreds of new readers to this newsletter — and more than a few uncomfortable conversations with colleagues — I wanted to follow up by examining another topic generating enormous attention in exactly the same clinical circles: the rapidly growing, politically charged, and deeply under-evidenced world of compounded peptides. If the GLP-1 piece was about a drug with overwhelming clinical trial data that I was using off-label, this one is about compounds where the clinical trial data is largely absent — and the political momentum to prescribe them widely is accelerating anyway. The contrast is instructive.
On February 27, 2026, HHS Secretary RFK Jr. announced on Joe Rogan's podcast that approximately 14 of 17 peptides the FDA placed on its "do not compound" list would be moving back to Category 1. The wellness community erupted. The medical skeptic community groaned. Both responses missed the point. The real question is what the human clinical evidence actually looks like for these compounds, measured against standards that exist for good reason.
The Regulatory Landscape: What These Categories Actually Mean
The compounding debate generates so much heat because it conflates three categorically different things. Being moved to Category 1 is an access decision. It has nothing to do with whether a compound is safe or effective. That evidence is what it is, regardless of which regulatory row it sits in.
Status | What It Means | Evidence Required | Example |
|---|---|---|---|
FDA-Approved Drug | Reviewed for safety and efficacy across Phase 1–3 trials; approved for a specific indication | Two adequate, well-controlled RCTs. Thousands of subjects. Independent replication. | Semaglutide, PT-141 |
Category 1 (Compoundable) | FDA permits licensed pharmacies to prepare it for individual patients with a prescription. Not FDA approval. | Component of approved drug, USP monograph, or PCAC review. Not an efficacy standard. | GHK-Cu (topical), Sermorelin |
Category 2 (Banned) | FDA has identified significant safety risks or insufficient human data. Pharmacies face enforcement risk. | None — these failed to meet the Category 1 threshold. | BPC-157, MOTS-C, Melanotan II |
Research Use Only | Legal for laboratory research only. Illegal to administer to humans. No quality oversight enforced. | None. | Most gray-market peptide vendors |
The Drug Approval Standard — And Why It Exists
The FDA's phased approval process was built in response to historical catastrophe. The thalidomide disaster — prescribed to pregnant women for morning sickness, causing severe birth defects in thousands of children — drove the 1962 Kefauver-Harris Amendment, which first required drugs to demonstrate efficacy. Before that, the bar was essentially: does it kill people quickly? A 2014 analysis found only ~14% of drugs entering Phase 1 ever receive FDA approval — not because the science was sloppy, but because humans are not mice.
Phase 1 — Safety 20–100 healthy subjects. Establish tolerability, pharmacokinetics, and safe dosing range. Tells you: rough dose range. Does not tell you: whether it works. | Phase 2 — Signal 100–300 patients with the target condition. Does it do anything measurable? Explore dosing. Does not tell you: whether the effect is clinically meaningful or durable. | Phase 3 — Proof 1,000–10,000+ subjects. At least two blinded, placebo-controlled RCTs with pre-specified endpoints. This is the bar for widespread prescription. |
Preclinical promise does not substitute for clinical evidence. This is not philosophical — it is a pattern repeated so often in drug development that it qualifies as a law.
The 17 Peptides: Evidence by Tier
Organized not alphabetically or by hype, but by strength of human evidence against the Phase 1/2/3 benchmark. "Claimed uses" reflect wellness market marketing, not approved indications. This installment covers Tiers I–III — the compounds where at least some human data exists. Part II covers Tiers IV and V: the compounds where it largely doesn't.
I Approved or Phase 3 Completed Has cleared or attempted the full evidentiary standard |
|---|
PT-141 / Bremelanotide MC3/4R agonist · Brand: Vyleesi ✓ FDA Approved The one unambiguous success on this list. Two Phase 3 RCTs (~1,200 subjects) supported FDA approval in 2019 for hypoactive sexual desire disorder in premenopausal women. Its Category 2 compounding status is a commercial pathway issue — protecting the approved product — not a safety concern about the molecule. Its presence here tells us almost nothing about the other 16. |
AOD-9604 C-terminal GH fragment · lipolytic signaling Phase 3 — Negative Perhaps the most instructive entry on this entire list: it actually went through clinical trials and failed. The METRO trial (Phase 2b/3, n>900) showed no significant weight loss versus placebo at 24 weeks. The program was abandoned as a pharmaceutical candidate — then migrated into the wellness market, where it is still marketed for fat loss. AOD-9604 is not a case of insufficient evidence. It is a case where the evidence was obtained and it was negative. |
II Phase 2/3 Data — Wrong Indication Controlled trials exist, but not for the uses being marketed |
|---|
Thymosin Alpha-1 (Tα1) T-cell modulator · Brand: Zadaxin Phase 2/3 (Narrow Indication) Tα1 has the most substantial legitimate clinical trial history of any non-approved compound on this list — approved in 30+ countries for hepatitis B/C. A 2013 Chinese RCT in critically ill patients showed reduced 28-day mortality. The evidence is real. But those were specific infectious disease indications. The compounding market prescribes it for immune "optimization" and post-COVID syndrome — indications with essentially zero controlled trial data. |
III Phase 1–2 Only Human data exists — but only early-phase safety/PK, no Phase 3 |
|---|
CJC-1295 GHRH analogue — stimulates pituitary GH release Phase 1 Only The most-cited human study (Teichman et al., 2006) enrolled 21 healthy subjects confirming biological activity and a prolonged half-life. That is real Phase 1 data — and nothing more. No Phase 3 trial has been completed for any indication. The anti-aging and body composition uses being marketed have not been subjected to any randomized controlled trial. |
Ipamorelin Ghrelin receptor agonist — growth hormone secretagogue Phase 1/2 + Safety Signal Developed by Novo Nordisk, Phase 1/2 studies established its PK and GH-stimulating profile. A Phase 2 in post-operative ileus — entirely different from wellness uses — was ultimately deprioritized. The FDA's Category 2 designation cited a reported death linked to ipamorelin via IV infusion outside clinical protocols. No controlled trials exist for anti-aging or body composition indications. |
GHRP-2 & GHRP-6 Ghrelin mimetics — GH and cortisol secretagogues Phase 1/2 + Safety Concerns Both compounds have a legitimate Phase 1/2 human pharmacology literature — GH and cortisol responses, appetite effects, and PK profiles well-characterized. GHRP-2 specifically had adverse events including deaths flagged by the FDA in critically ill patients, along with cortisol elevation and glucose dysregulation signals. Neither has completed Phase 3. Neither has controlled efficacy data for any of the muscle, anti-aging, or performance uses being marketed. |
Coming in Part II
The compounds with almost no human data at all — and one with an active safety concern
Part II covers Tiers IV and V: BPC-157 (~30 total human subjects ever), MOTS-C and KPV (zero published human trials), Melanotan II (melanoma case reports), and six others. Plus the full 17-compound scorecard and the policy argument — why a procedural win for RFK Jr. doesn't answer the scientific question.
Part I References
Sources & Further Reading
Regulatory & Policy
U.S. Food and Drug Administration. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A — Category 2 List. September 2023. fda.gov
U.S. Food and Drug Administration. Pharmacy Compounding Advisory Committee (PCAC) Meeting, December 2024 — Category 2 Nominations Review. fda.gov
Joe Rogan Experience. Episode #2461 — RFK Jr. February 27, 2026.
Kefauver-Harris Drug Amendments of 1962. Pub. L. No. 87-781, 76 Stat. 780 (1962).
Drug Development & Approval Standards
Hay M, Thomas DW, Craighead JL, Economides C, Rosenthal J. Clinical development success rates for investigational drugs. Nat Biotechnol. 2014;32(1):40–51. doi:10.1038/nbt.2786 Source of the ~14% Phase 1 → FDA approval statistic.
PT-141 / Bremelanotide
Clayton AH, Althof SE, Kingsberg S, et al. Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial. Womens Health (Lond). 2016;12(3):325–337. doi:10.2217/whe-2016-0018
Simon JA, Kingsberg SA, Portman D, et al. Long-term safety and efficacy of bremelanotide for hypoactive sexual desire disorder. Obstet Gynecol. 2019;134(5):909–917. doi:10.1097/AOG.0000000000003514
U.S. Food and Drug Administration. FDA Approves New Treatment for Hypoactive Sexual Desire Disorder in Premenopausal Women. Press release, June 21, 2019. fda.gov
AOD-9604
Heffernan MA, Thorburn AW, Fam B, et al. Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone fragment 176–191. Int J Obes Relat Metab Disord. 2001;25(10):1442–1449. doi:10.1038/sj.ijo.0801740
Metabolic Pharmaceuticals Ltd. AOD9604 Phase 2b/3 Clinical Trial (METRO Study) — Results Summary. 2007. Trial terminated; results on file; no peer-reviewed publication.
Confirms negative primary outcome: no significant weight loss vs. placebo at 24 weeks.
Thymosin Alpha-1
Romani L, Bistoni F, Perruccio K, et al. Thymosin alpha1 activates dendritic cell tryptophan catabolism and establishes a regulatory environment for balance of inflammation and tolerance. Blood. 2006;108(7):2265–2274. doi:10.1182/blood-2006-02-004762
Wu J, Zhou L, Liu J, et al. The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trial. Crit Care. 2013;17(1):R8. doi:10.1186/cc11932
CJC-1295
Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. J Clin Endocrinol Metab. 2006;91(3):799–805. doi:10.1210/jc.2005-1536
Ipamorelin
U.S. Food and Drug Administration. Category 2 Bulk Drug Substance Safety Review — Ipamorelin. PCAC Briefing Document, 2024.
GHRP-2 & GHRP-6
Bowers CY, Momany FA, Reynolds GA, Hong A. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology. 1984;114(5):1537–1545. doi:10.1210/endo-114-5-1537
Arvat E, Maccario M, Di Vito L, et al. Endocrine activities of ghrelin, a natural growth hormone secretagogue (GHS), in humans: comparison and interactions with hexarelin, a nonnatural peptidyl GHS, and GH-releasing hormone. J Clin Endocrinol Metab. 2001;86(3):1169–1174. doi:10.1210/jcem.86.3.7293
U.S. Food and Drug Administration. Category 2 Bulk Drug Substance Safety Review — GHRP-2 / GHRP-6. PCAC Briefing Documents, 2024.
Disclosure: This post is for informational and educational purposes only. It does not constitute medical advice and should not be interpreted as a recommendation for or against any specific therapy. Drug development evidence and regulatory status can change. Always consult a licensed physician before making treatment decisions. The author has no financial relationship with any pharmaceutical, compounding pharmacy, or peptide vendor referenced in this article.