# How to read a peptide study

> To judge a peptide study, check whether it tested people, how many and for how long, whether it had a comparison group, what it measured and who paid for it. Most treatments tested in animals do not reach approval: a 2024 review of 367 found that 14 had.

The journal is published by Rovere, a telehealth service that sells some of the treatments discussed here. Articles are general information, not medical advice. Only a licensed clinician can say whether a treatment is right for you.

- Topic: Research
- Web page: https://roverehealth.com/journal/how-to-read-a-peptide-study

## Key points

- Results in cells or animals are a reason to test a substance in people, not proof that it works in people. Of 367 treatments tested in animals, 14 had been approved, a 2024 review found.
- Small, short studies can miss side effects. For a medicine taken long term for a condition that is not life-threatening, guidance adopted by the FDA expects about 1,500 people to have taken it before approval.
- Without a comparison group, a study cannot separate a treatment’s effect from the placebo effect. A 2015 analysis of 149 knee osteoarthritis trials found that a placebo injected into the knee eased pain more than a placebo pill.
- A change in a lab value does not show that people feel or function better. In a placebo-controlled trial in older adults, a year of ibutamoren, an unapproved drug, raised growth hormone and blood sugar without improving strength or function.
- PubMed flags a paper as retracted when its journal publishes a retraction notice. ClinicalTrials.gov shows whether a trial was registered before it began and whether it posted results. Both are free to search.

## Was it done in cells, animals or people?

Studies of cells in a dish (lab studies) and of animals cannot show what a substance does in people. A 2024 review of 122 earlier reviews tracked 367 treatments tested in animals, for 54 diseases. Of these, 165 had been tested in people and 132 in a randomized trial, where chance decides who gets the treatment. Only 14 were approved. [1]

For 62 treatments with five or more animal studies, results were positive in about four in five animal studies but only half of randomized trials. Even so, the authors concluded that animal results may carry over to people more often than widely claimed. They suggest weak design in animal studies and early trials explains why so few win approval. [1]

Most research on the peptide BPC-157 is in animals or cells (preclinical research). Of 36 studies in a 2025 review of its use for sports injuries, 35 were preclinical. BPC-157 is not part of any FDA-approved drug. [2, 3]

A title can claim more than the study tested. A 2019 paper on MOTS-c, a peptide not part of any FDA-approved drug, has a title that begins “MOTS-c accelerates bone fracture healing”. The paper reports only experiments on rat stem cells in a dish. It was retracted in 2021 over errors in its images. [4, 5, 6]

## How many people, and for how long?

The FDA describes three phases of testing in people before approval. Phase 1 trials enroll 20 to 100 people for several months to study safety and dosage. Phase 2 trials, with up to several hundred, “aren’t large enough to show whether the drug will be beneficial”, the FDA says. Phase 3 trials enroll 300 to 3,000 people for 1 to 4 years, so rare or long-term side effects are more likely to show up. [7]

International guidance the FDA adopted in 1995 covers medicines taken for over six months for conditions that are not life-threatening. It expects about 1,500 people to take such a medicine before approval, 100 of them for a year. If none of those 100 has a serious side effect, that gives reasonable assurance the true one-year rate is no higher than 3 in 100. Testing before approval is not expected to measure side effects rarer than 1 in 1,000. [8]

The FDA’s 2026 review lists five published studies of BPC-157 in people. Two were randomized enema trials with a placebo group, from 2002 to 2005, known only from conference abstracts (short meeting summaries). The other three, from 2021 to 2025, were small studies with no comparison group at private clinics in Florida, all with the same lead author. [3, 9, 13, 29]

The 2025 study followed two people for three days, and its authors wrote it showed BPC-157 was safe in humans. Reviewing all five, the FDA found no reported serious side effects but called the studies short and small, with limited safety information and, for most, unclear monitoring. It concluded there is not enough safety information from people to describe BPC-157’s safety. [9, 3]

## Was the same thing tested, the same way?

None of the five studies used a form proposed for compounding: capsules, injections under the skin, nasal sprays, skin creams or rectal suppositories. Nor did they say clearly whether they used BPC-157 itself or its acetate salt, a different chemical form the FDA treats as a separate ingredient. [3]

## Was there a comparison group?

A comparison group (a control group) shows what happens to similar people who do not get the treatment. Assigning people by chance makes the groups alike, so they can be compared more fairly. The comparison group often gets a placebo, an inactive look-alike given the same way. [10, 11]

Blinding keeps people from knowing who got what. In a double-blind study, neither participants nor researchers know until the trial ends, which makes biased results less likely. [12]

The 2021 knee study reviewed records of 17 patients at one clinic. Researchers phoned 16, most six months to a year after their injections, and asked them to recall their pain before and how much the injection helped. Four had also received a second substance, thymosin beta-4, which the FDA has not approved. [13, 14]

Most said their pain had eased. With no comparison group, the study cannot separate that from a placebo effect. In a 2015 analysis of 149 randomized trials in knee osteoarthritis, a placebo injected into the knee relieved pain more than a placebo pill. [13, 15]

## What was measured?

A clinical outcome, the FDA explains, measures directly whether people feel or function better, or live longer. A surrogate endpoint, such as a lab value, is expected to predict a benefit but does not measure one. Some surrogates have earned that trust: in the FDA’s example, lowering systolic blood pressure (the top number in a reading) reduced stroke risk in many trials. [16, 17]

Ibutamoren (MK-677), an experimental drug taken by mouth, makes the body release more growth hormone. It is not a peptide, and no FDA-approved drug contains it. In a randomized, double-blind trial published in 2008, 65 healthy adults aged 60 to 81 finished a year of ibutamoren or a placebo. Growth hormone, IGF-1 (insulin-like growth factor 1, a protein that stimulates cell growth) and fat-free mass rose, but strength and function did not. Blood sugar rose, and the body’s response to insulin weakened. The authors said the trial was too small and too short to judge function. [18, 19, 20]

In a 2011 randomized trial in 123 older adults recovering from hip fractures, IGF-1 again rose but most measures of function did not improve. The trial was stopped early because of a safety signal: heart failure in four people taking ibutamoren and one taking a placebo. Citing that trial, the FDA lists ibutamoren among raw ingredients for compounded medicines that “may present significant safety risks”. The National Cancer Institute notes that higher than normal IGF-1 levels may raise the risk of several cancers. [21, 18, 22, 20]

A trial names its most important measure in advance: its primary outcome. The peptide elamipretide (SS-31) was tested in 12 people with Barth syndrome, a rare genetic disorder. In a double-blind crossover trial, each took the drug and a placebo for 12 weeks apiece, in random order. It did not beat the placebo on either primary outcome: distance walked in six minutes and a fatigue score. [23, 24, 25]

The strength of the thigh muscles that straighten the knee, a lower-ranked measure (a secondary outcome), did not rise during that trial. It rose later, in an extension where everyone knowingly took the drug. Based on that measure, the FDA granted elamipretide accelerated approval in 2025 to improve muscle strength in Barth syndrome. This pathway, for serious conditions with an unmet medical need, allows approval on a measure reasonably likely to predict a benefit. A trial to confirm the benefit began in 2026, and the FDA may withdraw approval if such trials fail. Compounded versions of elamipretide are not FDA-approved. [24, 25, 23, 17, 26, 27]

## Absolute and relative risk

Absolute risk is how often something happens in a group over a set time. Relative risk divides one group’s risk by another’s. In November 2026 the FDA reported an analysis combining 126 randomized trials of GLP-1 drugs, which mimic a gut hormone. It counted cases of a rare condition that can cause sudden, sometimes permanent vision loss in one eye (NAION). There were 6.4 cases for every 100,000 people treated for a year with the drugs, against 3.8 with a placebo or another diabetes drug. [44, 45, 46]

Dividing 6.4 by 3.8 gives the relative risk: about 1.7 times as high with the drugs. Subtracting 3.8 from 6.4 gives the absolute difference: 2.6 extra cases for every 100,000 people treated for a year. Both figures rest on 15 probable cases, 10 on the drugs and 5 on a placebo. The FDA calls the risk potential but now requires a label warning. [46]

A 2011 Cochrane review, which gathers all studies that meet rules set in advance, pooled 23 studies of how persuasive relative and absolute figures are. Asked to make hypothetical choices, health professionals and the public found the same drop in risk more persuasive when stated in relative terms. Low-quality evidence from four studies suggests relative figures may also make the drop seem larger. The authors argue that relative figures alone do not allow a fair comparison of benefits and harms. [47]

## Has anyone else found the same thing?

For BPC-157, independent teams have rarely repeated the work. A 2026 review estimated more than four in five published BPC-157 studies came from one group at the University of Zagreb, where the peptide was first made. It called the lack of independent replication a serious limitation by current standards. [28]

Small trials can also suggest a benefit that a larger trial does not confirm. Thymosin alpha-1, a peptide first isolated from the thymus gland, is not part of any FDA-approved drug. In sepsis, a life-threatening reaction to infection, a 2016 analysis of 10 small randomized trials, 530 patients in all, suggested on low-quality evidence that it reduced deaths. The TESTS trial, published in 2025, randomly assigned 1,106 adults in China to thymosin alpha-1 or a placebo, double-blind. It found no clear reduction in deaths at 28 days. [30, 31, 32]

## Who paid for it?

The International Committee of Medical Journal Editors (ICMJE) asks authors to name each funder and any role it had in the design, data or writing. They should also disclose ties such as employment, consulting, stock and patents, which do not always mean the work was influenced. [33]

A 2017 Cochrane review included 75 papers, each comparing studies funded by a drug or device maker with other studies. Maker-funded studies more often reported favorable efficacy results and conclusions. They were no worse at randomization and were more often well blinded. Their conclusions agreed with their own results less often, so compare a paper’s conclusion with its numbers. [34]

## Where to find the study itself

PubMed, a free index run by the US National Library of Medicine, holds more than 40 million citations and abstracts. It does not hold full papers but often links to them. [35]

A trial should also be in a public registry, such as ClinicalTrials.gov. The ICMJE asks journals to consider publishing a trial only if it was registered by the time its first participant agreed to join. Registration aims to stop whole trials or some outcomes from going unpublished. So compare the main outcome in the record with the one in the paper. [36]

US rules require many controlled drug trials to post results, usually within a year of the last measurement of the main outcome. Phase 1 trials are exempt. A placebo-controlled phase 1 trial of BPC-157 tablets, planned for 42 healthy volunteers in Mexico, lists October 2015 as its start but was first registered that December. Its record, not updated since, shows no results. The FDA could find no published report of it. [23, 37, 3]

## Is it a full paper, and does it still stand?

A conference abstract is not a full report. The FDA found that the 2005 colitis abstract did not clearly describe its main outcome, who could enroll or how data were analyzed. It judged the data inadequate to support the treatment’s effectiveness or safety. [3]

A preprint is a complete draft posted before peer review, the check by outside experts that journals use. The preprint server medRxiv says preprints should not guide clinical practice or health-related behavior. PubMed also lists some preprints, so being in PubMed does not mean a study was peer reviewed. [38, 39]

When a journal retracts (withdraws) a paper and publishes a notice, PubMed links the two and tags the paper as a retracted publication. It links corrections (errata) the same way: the TESTS paper was corrected in 2025 for data errors, and its conclusion did not change. The free Retraction Watch Database, searchable by title, author or PubMed ID, gathers retractions from publishers and other sources. [40, 41, 32, 42, 43]

## Questions to ask of any study

- Was it done in cells, animals or people?
- How many people, and for how long?
- Was the same form tested, given the same way?
- Was there a comparison group, chosen by chance?
- Who knew who got what?
- Was the main result something people notice, or a lab value?
- Are risks given as absolute numbers, or only as relative ones?
- Has an independent team repeated it?
- Who paid, and what was the funder’s role?
- Was it registered before it began, and does the paper match the record?
- Is it a full paper, a preprint or a conference abstract?
- Has it been corrected or retracted?

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