An advisory committee to the Food and Drug Administration convened Thursday to evaluate whether compounding pharmacies should be allowed to produce seven peptides that were previously banned over safety concerns.

Despite being prohibited, some of these peptides have become increasingly popular among consumers who purchase them from longevity clinics, alternative health providers, biohacking influencers and even TikTok. The peptides may be produced in unregulated labs, often in China, and sold as “research grade” compounds.

The F.D.A. is evaluating the peptides for specific uses, like treating ulcerative colitis, insomnia and osteoporosis. But they are marketed and used for many other purposes, which could be permitted off-label if the drugs were cleared.

F.D.A. staff scientists reviewed the research on the peptides and have recommended against clearing the peptides, citing a lack of safety and efficacy data in humans. Here’s what they found.

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BPC-157

BPC-157, sometimes referred to as Body Protection Compound or bepecin, is one of the most popular “gray market” peptides.

The F.D.A. is evaluating it to treat ulcerative colitis, and it is also marketed as helping to reduce gastrointestinal inflammation and prevent ulcers. Another common use is to support muscle and joint healing — it is sometimes referred to as the “Wolverine compound,” after the Marvel superhero, especially when taken in combination with another peptide, TB-500.

A few small studies in humans have suggested BPC-157 might have benefits for knee pain, bladder-related pain or ulcerative colitis symptoms. But these had notable limitations: Two lacked a placebo group, and another was not published in a peer-reviewed journal.

Research in animals suggests that BPC-157 could be helpful for healing stomach and small intestine lesions and for musculoskeletal damage, among other things.

No serious side effects were reported in the human studies, but a few adverse events, including one that led to an emergency room visit, have been reported to the F.D.A. Limited safety data from animal studies suggest the peptide could affect blood clotting and liver function.

The F.D.A. report also mentions a general concern that the peptides being evaluated could trigger a potentially dangerous immune reaction, particularly when injected or inhaled.

KPV

The F.D.A. is evaluating KPV, a peptide derived from a hormone made by the pituitary gland, for wound healing and inflammatory skin conditions. It is administered in a cream or gel.

Other promoted uses of KPV include strengthening the immune system, treating inflammatory bowel diseases, protecting against nerve damage and stroke and aiding recovery from Covid-19, Lyme disease and mold toxicity.

A few studies in mice and cells have suggested KPV has some anti-inflammatory properties.

F.D.A. scientists could not find any published data on KPV safety or efficacy in patients. However, one study tested the peptide on human cadaver skin and found that it wasn’t very good at permeating the skin, which the report noted could “limit the potential usefulness of KPV as a topical therapeutic.”

TB-500

TB-500 was initially developed as a veterinary drug “marketed to boost performance in equine and greyhound sports,” the F.D.A. report said.

The advisory committee is evaluating the injected peptide for wound healing. It is also marketed online for promoting tissue repair and regeneration, reducing inflammation and improving endurance, among other claims.

The report references one mouse study suggesting TB-500 improved wound healing and another in cells that showed no effect.

The experts could not find any articles about use of the peptide in humans, and they warned that there is a general lack of safety information.

MOTS-c

MOTS-c is a peptide created from mitochondria DNA that appears to play a role in cellular metabolism.

The F.D.A. committee is evaluating the peptide for obesity and osteoporosis; it is also promoted for metabolic, liver and muscle health, among other uses.

A handful of studies in animals and cells have suggested the peptide could help with weight loss, blood sugar control and bone growth.

But the F.D.A. advisers cautioned against making too much of those findings, since there is no published research available in humans. There is also virtually no data on either the short-term or the long-term safety of the peptide.

Emideltide

Emideltide, also known as the delta sleep-inducing peptide, is naturally produced in the brain. Levels fluctuate throughout the day, which suggests it is connected to circadian rhythms, and it has been shown to increase deep sleep in animals.

The F.D.A. is considering an emideltide injections for insomnia, narcolepsy and opioid withdrawal. (Scientists think it acts through the opioid system.) It’s also marketed for stress, pain, cancer and neurodegenerative diseases, including Alzheimer’s and Parkinson’s.

There are several human studies of emideltide, most from the 1980s involving intravenous infusions. The research has generally suggested that emideltide helps people with insomnia fall asleep faster and stay asleep longer compared with a placebo. But the studies were very small and had limitations and did not all show a clear benefit.

The human data was even more limited for narcolepsy — just a single case report in one patient.

Two small studies on opioid withdrawal found that emideltide at least temporarily improved symptoms in a majority of people, but neither included a placebo control.

There is little safety data on the compound. One rat study suggested it slightly lowered heart rate and increased body temperature. No significant adverse events were reported in the insomnia trials, according to the F.D.A. report, but some patients in the withdrawal studies reported low blood pressure, headaches, nausea and other side effects.

Semax

The F.D.A. is evaluating an injection and nasal spray of semax for three conditions: cerebral ischemia (impaired blood flow to the brain), migraine and trigeminal neuralgia (episodic facial pain).

Wellness clinics also market the peptide as a treatment for mental health disorders including anxiety, depression and A.D.H.D., as well as neurological diseases such as A.L.S. and Parkinson’s.

Semax is available as an intranasal drug in Russia, and much of the human research is published in Russian or in conference presentations that don’t offer complete data. One of the few studies available in English found that a nasal spray decreased pain scores in 12 people with migraine, but the peptide wasn’t compared with a placebo. The same study found no benefit for trigeminal neuralgia.

A few rodent studies reported that semax limited the damage from ischemia. Researchers think the peptide may have an anticoagulant effect. Another proposed benefit is that it increases levels of growth factors in the brain associated with neuroplasticity. Other studies in rats suggest semax has a pain-relieving effect, though scientists don’t know how it might be helping.

There is one report of an adverse event involving a semax nasal spray: A woman reported eye pain and burning that resulted in hospitalization. The anti-clotting effects of semax could increase the risk of bleeding, the F.D.A. report warned.

Epitalon

Epitalon is a derivative of a substance extracted from the pineal glands of cattle. The pineal gland controls the sleep-wake cycle, and the peptide is proposed to help with insomnia.

One human study suggested that epitalon may increase melatonin production, a finding backed up by research in monkeys, which showed that it could help regulate circadian rhythms.

Epitalon is also marketed as a longevity peptide, with claims that it slows aging, improves skin health, increases energy and prevents a number of age-related diseases.

The longevity claims stem from epitalon’s reported ability to lengthen telomeres, part of DNA chromosomes that are thought to be involved in longevity. A few mouse studies suggest that epitalon can extend life span, potentially by restricting tumor development.

However, scientists have flagged concerns generally (outside of the research on epitalon) that long telomeres may be linked to cancer. And the F.D.A. report cautioned that long-term, continuous exposure to epitalon could be carcinogenic.

On Thursday, a majority of members on the F.D.A. advisory committee voted in favor of wider access to BPC-157, KPV, TB-500 and MOTS-c. The committee will meet again on Friday to vote on the other peptides.

Christina Jewett contributed reporting.

A Food and Drug Administration advisory committee hearing on Thursday and Friday may set Health and Human Services Secretary Robert F. Kennedy Jr., known for embracing unproven wellness trends, on a collision course with agency scientists who have deep expertise on drug safety.

At issue is whether the F.D.A. should allow specialized pharmacies to produce seven peptide injections that the agency banned three years ago over safety concerns. The injections, some of which Mr. Kennedy has used and trumpeted, are currently sold as “research grade” products not meant for widespread use. Despite the restriction, they are marketed online for a wide range of claimed benefits, from tendon repair to brain health.

In documents prepared for the hearing, F.D.A. scientists advise against allowing broader use, saying that the risks and benefits of the peptide drugs under consideration are poorly understood and have not been sufficiently studied.

The 19-member committee evaluating that data and other information includes a traditional roster of pharmacists and academic scientists and doctors — but also six people who sell or dispense peptides. F.D.A. advisory panels are intended to be neutral bodies of outside experts; it is highly unusual to appoint people to them who market the products that they are voting on.

“There seems to be a fingerprint of R.F.K. on this committee, is my impression,” said Paul Knoepfler, a University of California at Davis biologist who studies F.D.A. oversight of unproven treatments. He added: “To me, the makeup of this committee seems pretty striking.”

The Department of Health and Human Services defended the selections. “All committee members underwent the same ethics review and vetting process required of all FDA advisory committee members,” the department said in a statement. “Candidates that could not meet existing ethics requirements were removed from consideration.”

Soon after President Trump tapped Mr. Kennedy to take a health leadership role, Mr. Kennedy pledged to end the F.D.A.’s “war” on peptides and other restricted items. Thursday’s hearing begins the first potent test of whether he will follow through.

The outcome carries incredible weight, said Dr. Pieter Cohen, an associate professor of medicine at Harvard Medical School who studies agency oversight.

“It’s going to reposition the F.D.A. in a much weaker position if they cave to this kind of political pressure,” he said. “Because there’s no reason these peptides should be approved.”

F.D.A. advisory committee votes are nonbinding. A committee’s input is typically considered by F.D.A. scientists and officials who make a final recommendation to the agency’s commissioner. However, the health and human services secretary has the authority to overrule the agency’s decision.

That rarely happens, but in conversations about peptides, Mr. Kennedy has expressed an interest in making the final decision and has leaned toward adding the peptides back to the compounding list, according to two people familiar with the matter who were not authorized to speak publicly.

Peptides are chains of amino acids that prompt cells to perform actions like decreasing inflammation or increasing collagen production. Some peptides that have been fully vetted by the F.D.A. include drugs like insulin or GLP-1s.

But unproven peptides with names like BPC-157 and MOTS-c have gained a foothold on social media, where users show off their “stacks,” or combinations of peptides, and extol their virtues for weight loss, muscle building and glowing skin. They are often referred to as “peppers” to avoid content moderation.

Some are backed by studies in rodents or in a petri dish suggesting that they could help with wound healing, osteoporosis or inflammation. But a similarly limited set of studies suggests they could cause harm, such as severe allergic reactions or the potential to enhance tumor growth.

There is little to no data on how these peptides work in humans.

“We’re missing safety, we’re missing efficacy — we’re missing the critical evidence,” said Dr. Eric Topol, a cardiologist and the founder of the Scripps Research Translational Institute.

“I don’t have a bias that the peptides are bad, necessarily,” he added. “I just want to see the evidence, and we don’t have any.”

F.D.A. records show that the six committee members who sell peptides include self-described longevity physicians who market peptides for overall health, and even for some specific diseases. Some of their clinics also offer other unproven treatments such as ozone therapy and energy healing.

One member, Dr. Gabriel Alizaidy, is the scientific director at Maximus, a telehealth company that sells growth hormone peptides for about $200 per month. The company received a warning letter from the F.D.A. over its claims about compounded weight-loss medications.

Another panelist is Bobby Harshbarger, a Tennessee state senator and pharmacist. His mother, Representative Diana Harshbarger, Republican of Tennessee, who is also a pharmacist, wrote to Mr. Kennedy in November urging him to allow wider use of some of the peptides under consideration Thursday and Friday.

On a podcast last year with Gary Brecka, a biohacker who sells peptides on his website, Mr. Kennedy said the F.D.A. should “just do the science” on items like peptides and unproven stem cell treatments, “but not tell people, and not tell physicians, what they can and cannot prescribe.”

“If you want to take an experimental drug, you can do that,” Mr. Kennedy said. “You ought to be able to do that.”

More recently, Mr. Kennedy has said that the 2023 ban on the peptides has forced people to use gray-market peptides that present safety concerns. Adding them to the list of compounds that can be made in regulated pharmacies would increase safety, he has argued.

But Scott Brunner, the chief executive of the Alliance for Pharmacy Compounding, said that traditional manufacturers of pharmaceutical ingredients had never made these peptides.

He said that would be unlikely to change if Mr. Kennedy reverses the ban, given widespread jitters among compounding pharmacies about using peptides that were “never authorized for use in human drugs.”

Mr. Brunner said he would propose at the hearing on Thursday that the peptides be added to the list of items that pharmacies can compound, but in a process that includes guardrails such as safety tracking, disclosures about risks and mandatory reporting of serious adverse events.

Doing so, he said, would mean “allowing state-licensed pharmacies to prepare the substances as a means of blunting the illicit markets.”

To prepare for the two-day meeting, F.D.A. scientists performed reviews of each of the seven peptides. One initial obstacle they discovered was that even though each peptide had a single name, in practice, it tended to refer to a mixed bag of formulations.

What patients actually get “may offer distinct properties,” the F.D.A. said in its analysis of one peptide, and “represent a safety risk for patients” who get a different substance than what a doctor had in mind.

Scientists also noted that some peptides marketed as longevity tonics may also promote cancerous tumor growth.

They also suggested that patients pursuing peptide therapy for serious conditions could miss out on treatments that were carefully reviewed and deemed effective. They flagged one small study of the peptide BPC-157 for people with ulcerative colitis that suggested benefits that the agency scientists found unconvincing for “a serious chronic disease that may cause life-threatening complications.”

Dr. Pinchas Cohen, the dean of the University of Southern California Leonard Davis School of Gerontology, is scheduled to present his research at the meeting but said he is “very conflicted” about the issue.

Dr. Cohen (no relation to Dr. Pieter Cohen) was the first to publish on one of the peptides being debated, MOTS-c. He thinks the peptide is safe and may be beneficial for muscle and metabolic health, but he would prefer to develop the molecule as a drug through the traditional pathway.

Still, he added, “Since tens of thousands of people want this and other peptides, to protect them, I think it will be beneficial to semi-legalize this process.”