Ipamorelin’s published bowel-surgery trial missed its primary endpoint.

Why this note exists

Ipamorelin is not a fringe listing. In the index generated on August 15, 2026, 101 of 112 vendors carried it — sixth of 83 compounds by vendor coverage, behind GHK-Cu, MOTS-c, BPC-157, NAD+ and Selank, and ahead of TB-500, tesamorelin and PT-141.[20] Those vendors publish 258 ipamorelin listings between them: 132 single-compound vials, most commonly 10 mg (64) and 5 mg (35), and 126 blend listings, of which 115 name CJC-1295 on the label.[20]

What makes it worth a note is not the volume. It is that ipamorelin has a real clinical history — a named sponsor, registered trials, a published paper, a formal FDA review and a recorded advisory vote — and almost none of that history is about the thing it is now sold for. The record exists. It points somewhere else.

A note on what kind of evidence this is: every efficacy figure below is human data, carrying its design, route and participant count. Rodent work is confined to one paragraph and labeled. Where FDA characterizes the evidence, FDA is quoted rather than paraphrased. Doses appear only as their sources published them, with route and population attached, and pepmg does not convert an intravenous per-kilogram infusion dose into a protocol for a research vial.

The regulatory status

Three doors into a compounding pharmacy, and ipamorelin is through none of them

Start with what ipamorelin is not, because the market's framing depends on it. There is no approved drug product containing ipamorelin in the United States.[13] FDA's own evaluation states the position in one sentence: "There is no applicable United States Pharmacopeia (USP) or National Formulary (NF) drug substance monograph for ipamorelin (free base) or its acetate form, and neither is a component of an FDA-approved drug."[1]

That sentence is load-bearing. Under section 503A, a compounding pharmacy may only use a bulk drug substance that complies with an applicable USP or NF monograph, or is a component of an FDA-approved drug product if no monograph exists, or appears on FDA's 503A Bulks List.[12] Ipamorelin fails the first two by FDA's own finding, which leaves the list — and the list is what the October 2024 meeting was about.[1][3]

Two nominators, a compounding pharmacy network and a health-solutions company, had proposed ipamorelin for two uses: growth hormone deficiency and postoperative ileus.[1] The proposed product was "a 2000 mcg/mL lyophilized powder for subcutaneous (SC) injection."[1] Note what is not on that list of proposed uses: fat loss, muscle gain, sleep, injury recovery, anti-aging. Nobody asked FDA to evaluate those, and FDA did not.

FDA also decided to review both salt forms on its own initiative rather than wait for the paperwork to be clarified, "due to FDA's significant safety concerns related to the use of certain peptides in compounded drug products."[1] The nominations themselves were a mess, in a way that is quietly instructive about the supply chain: FDA records that each package "provided inconsistent information," that the certificate of analysis submitted with each nomination "refers to one BDS by name in the title and a different BDS by the molecular weight/formula," and that it is unclear in both packages whether ipamorelin acetate or ipamorelin free base was the substance being nominated.[1]

The pivotal evidence

One published trial, 114 patients, an intravenous drip, and p = 0.15

FDA searched for effectiveness data and reported what it found in a single sentence: "We found only one article (Beck et al. 2014) that reported a clinical study evaluating efficacy of ipamorelin (unspecified form) in subjects with POI when administered via intravenous (IV) route of administration. We did not find additional data on effectiveness of ipamorelin (free base) or ipamorelin acetate for other clinical uses or when administered via the proposed SC route of administration or other routes of administration."[1]

That article is a Phase 2, multicenter, double-blind, placebo-controlled proof-of-concept trial published in the International Journal of Colorectal Disease in December 2014.[4] One hundred and seventeen adults undergoing small and large bowel resection were enrolled; 114 formed the safety and modified intent-to-treat populations, receiving intravenous ipamorelin 0.03 mg/kg twice daily or matching placebo from postoperative day 1 until day 7 or discharge.[4][1] The primary endpoint was time from first dose to tolerating a standardized solid meal.

p-values and medians as tabulated in FDA's evaluation from the modified intent-to-treat population (n = 56 ipamorelin, n = 58 placebo). Every reported endpoint — including discharge order written (p = 0.44), time to flatus (p = 0.35), readiness for discharge (p = 0.35) and time to bowel sounds (p = 0.11) — failed to separate from placebo.[1][4]

The direction of effect was consistent and the size was not trivial — seven hours earlier to a tolerated meal is the sort of difference a larger trial might have confirmed. It did not reach significance, and the authors said so plainly: ipamorelin "was well tolerated," and "[t]here were no significant differences between ipamorelin and placebo in the key and secondary efficacy analyses."[4] They also flagged their own limits: the study "was small and enrolled patients with a broad range of underlying conditions," and FDA's summary adds that strict exclusion criteria "may have eliminated some subjects with most potential to get benefit."[4][1]

What happened next is recorded in FDA's evaluation, quoting a 2020 publication on the compound's development: "in patients undergoing bowel resection, ipamorelin did not shorten the time to first meal intake compared with placebo. This phase II clinical trial did not show any significant difference in measurable colonic functions between ipamorelin and placebo. Due to these disappointing results, its development was discontinued."[1]

The gap

A 320-person registered ipamorelin trial has no posted results

There is a second interventional trial, and it is nearly three times the size of the published one. NCT01280344 is a Phase 2, randomized, quadruple-masked, placebo-controlled dose-finding study of intravenous ipamorelin at 0.03 mg/kg twice daily, 0.06 mg/kg twice daily and 0.06 mg/kg three times daily, in patients following small or large bowel resection with primary anastomosis.[6] Its sponsor was Helsinn Therapeutics, the same sponsor as the published trial. Enrollment was 320, actual. It started in April 2011, reached primary completion in June 2013, completed in May 2014, and its registry record was last updated in April 2017.[6]

The registry entry carries no posted results, and a PubMed search for ipamorelin returns no publication reporting it.[6][7] The smaller trial, NCT00672074, has no posted results either; it exists in the literature only because its investigators published it.[5][4] This is a gap in the record, not a finding: an unreported trial is unreported, and pepmg is not going to guess which way it went. But it is the single most consequential missing document about this compound, and anyone claiming to know what ipamorelin does in humans is working without it.

The whole registry footprint is smaller than most readers would expect. A ClinicalTrials.gov search on August 22, 2026 returned three registered studies of ipamorelin, total — the two Phase 2 trials above, both completed more than a decade ago, and one observational cohort.[7] That third study is not an ipamorelin study in any usable sense: it is a prospective cohort of 52 special operations veterans receiving ibogaine and 5-MeO-DMT alongside neuromodulation, in which ipamorelin appears as one item in a "Physiological Supplementation" package listed as "[s]ynthetic testosterone, Anastrozole, Gonadorelin, Vitamin and amino acid supplementation, Fish oil, Ipamorelin."[18] Nothing in that design can isolate one component.

The growth hormone question, and why a hormone spike is not an outcome

FDA also describes a subgroup signal: patients undergoing open laparotomy had shorter bowel recovery times on ipamorelin. That finding does not overturn the nonsignificant overall primary result, but it means that “negative on every endpoint” would be too broad. The authors urged caution because of sample size and eligibility restrictions.[1]

Ipamorelin does raise growth hormone in people. That has been shown, once, in 1999. A dose-escalation study published in Pharmaceutical Research gave five different intravenous infusion rates over 15 minutes, with eight healthy male subjects at each dose level, and measured ipamorelin and growth hormone concentrations.[8] It reported dose-proportional pharmacokinetics, a terminal half-life of about two hours, and "a single episode of GH release with a peak at 0.67 hours and an exponential decline to negligible GH concentration at all doses."[8]

Forty healthy men, single intravenous infusions, hormone concentrations as the endpoint. That is a pharmacology study, and it is a good one for what it set out to do. It measured no clinical outcome — not lean mass, not fat mass, not strength, not sleep, not wound healing, not injury recovery — and it was never designed to.

The other half of the growth hormone story is more awkward for the market, and it comes from FDA's clinical reviewers. Growth hormone secretagogues work by prodding the pituitary, so they need a pituitary that still works: "Patients with GHD will most likely not respond to GHSs, including ipamorelin (free base) and ipamorelin acetate, unless these patients have partially preserved pituitary function (partial GHD). Patients with complete GHD will not respond to GHSs."[1] FDA's conclusion for that use is flat — it "has not identified data to support the effectiveness of ipamorelin (free base) or ipamorelin acetate for the diagnosis or treatment of GHD in children or adults," and "[c]linical practice guidelines for health professionals do not mention" it for either.[1]

Animal and in vitro data, labeled as such: the rodent evidence for ipamorelin is real and it is where most of the mechanism comes from. In vitro, ipamorelin increased growth hormone release from rat pituitary cells in primary culture, with reported potency around 1.3 nM; in vivo, serum growth hormone rose dose-dependently in anesthetized male rats and awake female swine.[1][9] In rats with surgically induced ileus, intravenous ipamorelin at 0.1–1.0 mg/kg accelerated colonic transit and increased fecal pellet output, and multiple infusions over two days produced roughly 10% more body weight than untreated animals at 48 hours.[1][10] None of that is human data, and the human trial designed to test exactly that rodent result is the one that missed.

The vote

Two votes, one afternoon, 0 in favor each time

The Pharmacy Compounding Advisory Committee met at FDA's White Oak campus on October 29, 2024 to consider four substances for the 503A Bulks List: ibutamoren mesylate, L-theanine, ipamorelin-related bulk drug substances, and kisspeptin-10.[2][3] FDA's written recommendation was already on the table — the agency concluded that "a balancing of the criteria weighs against both ipamorelin (free base) and ipamorelin acetate being placed on that list."[1]

The committee agreed to vote on the two forms as a group by 12 to 1, then took them separately anyway. On ipamorelin free base: yes 0, no 12, abstain 1. On ipamorelin acetate: yes 0, no 12, abstain 1.[2]

Vote results as recorded in the final summary minutes, approved January 15, 2025. Ibutamoren mesylate, also a growth hormone secretagogue, was voted down 1 to 13 at the same meeting.[2]

The minutes record the reasoning: members who voted no "agreed that there was a lack of information supporting safety and efficacy shown in the available data for the use of Ipamorelin (free base) for GHD and postoperative ileus."[2] One line in those minutes is the whole problem in a sentence, and it was said by a committee member, not by us: "One Committee member commented that the high frequency of a drug being prescribed does not necessarily mean the drug is safe and effective."[2]

An advisory vote is advice. It does not approve or ban anything by itself, and FDA has to act through rulemaking to change the list. But it is the closest thing to a public, on-the-record adjudication of ipamorelin's evidence that exists, and the tally was unanimous among those who voted.

Safety

What FDA wrote down, and the size of the blank next to the route people actually use

In the published trial, treatment-emergent adverse events occurred in 87.5% of the ipamorelin group and 94.8% of the placebo group — a tolerability signal in ipamorelin's favor, in a post-surgical population where nearly everyone has an adverse event.[4] FDA's safety section lists what was reported in that intravenous study: "hypokalemia, insomnia, hyperglycemia, nausea, vomiting, abdominal distention and death," adding immediately that "it is unclear whether the two deaths were related to ipamorelin."[1] That uncertainty is FDA's own and it belongs in the same breath as the finding: two deaths occurred among ipamorelin-treated subjects in a trial of patients recovering from major abdominal surgery, and causality was not established.[1]

The larger safety statement is an absence, and FDA states it without hedging: "There are no safety data for ipamorelin (free base) and ipamorelin acetate administered by the nominator proposed SC ROA."[1] Subcutaneous injection is how essentially the entire research market administers it. The clinical safety database, such as it is, is intravenous, inpatient and post-surgical.

FDA's remaining concerns are about the substance rather than about reported harm. On immunogenicity: even though ipamorelin "is a peptide containing only 5 amino acids, FDA is concerned about the potential risk of immunogenicity because the immunogenic response may be enhanced when peptides like ipamorelin... are administered via injectable ROAs, such as IV and SC, due to potential for aggregation as well as potential peptide-related impurities."[1] On characterization, FDA concluded ipamorelin "is not well-characterized from the physical and chemical characterization perspective" because impurity, aggregate and endotoxin data were neither in the literature nor in the nominators' certificates of analysis.[1] It also noted that "due to limited water solubility of ipamorelin (free base), it is unclear how it would be possible to formulate the proposed injectable dosage form with the concentration of 2 mg/mL" — a statement about the nominated free-base formulation, not a measurement of anything on sale.[1]

Separately from the bulks-list question, ipamorelin acetate has sat in Category 2 of FDA's interim compounding policy under section 503B since September 29, 2023 — the category for substances FDA believes may present significant safety risks — with the entry citing immunogenicity potential, unnatural amino acids, and "[a] study published in literature identified serious adverse events including death when ipamorelin was administered intravenously for improving gastric motility."[11] The same page lists ipamorelin acetate among substances whose 503A nominations were later withdrawn by the nominators.[11]

The market

The blend nobody has tested, and a doping rule that is unambiguous

Half of what the index sees is not ipamorelin on its own. Of 258 ipamorelin listings, 126 are blends, and 115 of those name CJC-1295 alongside it; 90 vendors carry a single-compound vial and 76 carry a combination.[20] The pairing is close to a market standard, which makes its evidence base worth stating precisely: a ClinicalTrials.gov search returns no registered study of ipamorelin combined with CJC-1295, in any phase, anywhere.[7] CJC-1295 has its own thin registry footprint — a Phase 2 study in HIV-associated visceral obesity, 120 enrolled, terminated.[19] It is carried by 82 vendors in the index, sixteenth of 83 by coverage.[21]

FDA noticed the market too, and described it in the evaluation's conclusions: ipamorelin "has been marketed for use in weight loss management, anti-aging, inflammatory conditions, sleep cycle improvement, and bodybuilding in the injectable, nasal, and oral formulations. These formulations of ipamorelin are increasingly being marketed by medical spas and wellness clinics."[1] Not one of those uses appears in the two the nominators asked FDA to evaluate, and not one has a controlled human trial behind it.[1][7]

One status is completely unambiguous. The 2026 World Anti-Doping Agency Prohibited List names ipamorelin by name at S2.2.4, under "growth hormone secretagogues (GHS) and their mimetics," alongside anamorelin, ibutamoren, macimorelin and tabimorelin — a class prohibited at all times, in and out of competition.[14][15] Any tested athlete should treat every listing on this page as a sanction.

What the 2026 literature says, and what it is

Ipamorelin has picked up attention in the review literature this year, and the reviews are worth reading with their design in mind: these are narrative reviews, not new trials, and they generate no new human data. A narrative review in Sports Medicine in August 2026 surveyed approved and unapproved peptides marketed direct to patients — ipamorelin among AOD-9604, BPC-157, CJC-1295, GHK-Cu, MOTS-c, sermorelin, SS-31, tesamorelin and TB-500 — and summarized the field as one where "[m]any unapproved peptides demonstrate favorable tissue repair and metabolic outcomes in animal models, but rigorous human safety data are scarce, and there is potential for serious harm to patients."[16]

A June 2026 narrative review in Frontiers in Endocrinology takes the clinician's side of the same problem, stratifying growth hormone axis peptides "into evidence tiers from regulatory-grade randomized trial data to a complete absence of human studies," and cataloguing reported adverse effects across the class — prolactin and cortisol elevations, dysglycaemia, fluid retention, myalgia and arthralgia, injection-site reactions — while noting "the uncertainty surrounding product composition, dose, and stacking practices in unregulated supply chains."[17] Both papers are describing the gap this note is measuring. Neither closes it.

Three things this note is not saying

First, it is not saying ipamorelin does not work. That claim would need evidence too, and the evidence does not exist in either direction for the uses it is sold for. What exists is one small negative trial in an unrelated indication, one unreported larger trial in the same indication, a 1999 pharmacology study showing it releases growth hormone in healthy men, and rodent work.[4][6][8][1]

Second, it is not saying the advisory committee settled the science. A 503A bulks-list vote asks whether a substance should be available for pharmacy compounding given characterization, historical use, effectiveness and safety together — a different and broader question than "does this molecule do anything." The vote is evidence about the regulatory record, and it was unanimous.[1][2]

Third, it is not saying ipamorelin killed anyone. Two deaths occurred in ipamorelin-treated subjects in a post-surgical trial and FDA states plainly that whether they were related is unclear; reporting that accurately means reporting the uncertainty with it.[1]

What it is saying is narrower and, we think, more useful. The single most widely stocked growth hormone peptide in this index has three registered studies, two published human papers, zero data for the route it is sold in, zero data for the uses it is sold for, and a regulatory file in which the agency's reviewers and its outside advisers agreed.[1][2][7] That is a thinner record than a compound this popular is generally assumed to have.

Questions people are asking