Peptides and Cancer: MSK Oncologist on Unanswered Questions

Memorial Sloan Kettering Cancer Center, a leading U.S. cancer center, published a reality check on Sept 3, 2026, addressing a question its doctors increasingly hear: what do people with cancer need to know about the wellness peptides marketed online?[1] The answer from Dr. Larry Norton, a breast medical oncologist, senior vice president at MSK, and medical director of the Evelyn H. Lauder Breast Center, is that the evidence gap is the story: “We don’t know what these products actually do in the body, because there have not been appropriate scientific experiments.”[1]

What MSK’s oncologist said about the evidence gap

Peptides are short chains of amino acids — generally up to 50 — that act as chemical signals in the body, while proteins run several hundred amino acids long.[1] Some peptide drugs are thoroughly vetted: insulin, growth hormones, GLP-1 agonists such as Ozempic and Wegovy, and hormone-blocking medications used against hormone-driven prostate and breast cancers.[1]

The products Norton is skeptical of are the newer wellness peptides promoted by influencers and sold widely online for benefits such as “boosting” immunity, raising energy, or speeding muscle recovery. “To verify such claims, a peptide would need to be rigorously tested in the lab and then in controlled clinical trials with adequate follow-up time to look for longer-term side effects,” he said. “That foundational research is limited for many of the products currently being marketed.”[1]

The distinction matters to how the FDA treats the two categories: approved peptide drugs passed premarket scrutiny for specific conditions, while the promoted peptides have not been evaluated for safety or efficacy in humans.[1] PeptidesBeat has documented the same gap in UCLA Health’s six-peptide review and in Stanford clinicians’ warnings about the hype cycle.

What is different for people with cancer

Norton said the effects of unstudied peptides on cancer cells are an open question. Some marketed peptides claim to reduce inflammation or promote wound healing — the sort of claims attached to BPC-157 and TB-500 — which “could possibly impact the growth of cancer cells,” in his words.[1] He stressed that this is unknown, not established: “We don’t really know, because what many of these compounds actually do in the body and how they affect cells remains an open question.”[1]

He also flagged two non-tumor risks for people coping with a diagnosis. First, quality: products sold online as injectables, nasal sprays, creams, or powders are of unknown manufacturing, storage, and shipping quality — they could lose effectiveness in transit or contain impurities.[1] Second, delay: a patient may take a peptide for a symptom of an undiagnosed or progressing condition, postponing the moment a care team investigates it. MSK’s guidance is to raise symptoms with the treating team rather than order untested products, pointing patients to its integrative medicine service for evidence-based options such as acupuncture.[1]

Compounding access is not FDA approval

MSK’s piece also wades into the regulatory question PeptidesBeat has tracked all summer: an FDA advisory committee’s vote to allow compounding pharmacies to make certain peptides. In late July, the Pharmacy Compounding Advisory Committee voted to recommend six peptides — BPC-157, KPV, TB-500, MOTS-c, Semax, and Epitalon — for the FDA’s 503A Bulks List, while rejecting a seventh (our explainer of the vote). The FDA has not made a final ruling.

Norton’s caution applies to that debate: “Even an FDA decision to allow compounding is not the same thing as an FDA approval based on rigorous clinical trials.”[1] Opponents of the vote made a related argument — that pharmacy access would give unproven peptides “the appearance of legitimacy.”[1] See Do doctors recommend peptides?.

The bottom line from MSK

“These are potentially potent substances that could have both short-term and long-term harms,” Norton said. “Any peptide that has a positive effect can also have a negative effect.”[1] His example: insulin controls diabetes at the right dose for the right patient, and can be fatal at the wrong dose or in someone without diabetes.[1] “With these products, there are too many questions about safety. Until these products are properly studied, the risks are too great to ignore.”[1]

Frequently asked questions

Do peptides cause cancer?

No clinical trial has established that any wellness peptide causes cancer. Memorial Sloan Kettering’s Dr. Larry Norton said the effects of unstudied peptides on cancer cells remain unknown, and that peptides marketed for inflammation or wound healing could theoretically influence tumor growth — a question he says only controlled trials can answer.[1]

Are peptides safe for cancer patients?

MSK advises caution: the wellness peptides sold online have not been studied in clinical trials, manufacturing quality is unverified, and effects on cancer cells are unknown. MSK recommends that cancer patients discuss symptom management with their care team instead of ordering untested products.[1]

Are peptides approved by the FDA?

Some peptide drugs are FDA-approved — insulin, growth hormones, GLP-1 agonists, and certain hormone-blocking cancer therapies. The wellness peptides marketed online are not. An FDA advisory committee’s July 2026 vote to recommend six peptides for the compounding list is not approval; the FDA has not made a final ruling.[1]

Sources

[1] Memorial Sloan Kettering Cancer Center, Julie Grisham: Reality Check: What You Should Know About Peptides and Cancer — interview with Dr. Larry Norton (published Sept 3, 2026)

Nothing in this article is medical advice. PeptidesBeat is an independent editorial publication covering peptide policy, research, and industry developments. We do not sell peptides, recommend dosing, or provide medical advice. All content is informational. Peptides referenced may be subject to FDA restrictions; consult a licensed healthcare provider for any therapeutic question.