FDA Warning Letters of December 12, 2025: Five Firms, One Template, One Outcome

Updated September 22, 2026

On December 12, 2025, the U.S. Food and Drug Administration sent warning letters to five companies selling SARMs online: Pinnacle Professional Research dba Pinnacle Peptides, Atomix LLC, Dynamic Health Group dba SARMS AMERICA, TITAN SARMS LLC and Prime Sports Nutrition. The five letters are the same document. Four of their paragraphs are word-for-word identical, they were signed the same day by the same official in the same office, and each one gave fifteen working days to reply. What differs is the copy each firm had published — and the research-use wording each one relied on. FDA quoted ten such labels from the five firms, nine different wordings once capital letters are ignored. All five were read the same way.

This batch was missing from the published chronology of research-chemical enforcement, including the one kept on this index. It sits between the September 2025 telehealth letters and the seven-letter research-peptide batch of March 31, 2026. This page records what the five letters say, what they charge, and — because it is the part most often read backwards — what they do not establish.

The five letters

All five were issued by the Center for Drug Evaluation and Research and signed by Tina Smith, M.S., Captain, U.S. Public Health Service, Director of the Office of Unapproved Drugs and Labeling Compliance — the same office and the same signer as the March 2026 research-peptide batch and the June 2023 letter that opens this index's record. All five were posted publicly on December 23, 2025. In each case FDA states it reviewed the firm's website in November 2025, which makes the interval between review and letter about one month.

The five letters are one document, and that is measurable

This is not an impression from reading them. Four blocks were compared character for character across the letters and are identical in all five: the safety paragraph on SARMs, the paragraph establishing the products as new drugs under section 201(p), the conclusion, and the response paragraph. The comparison was first run on three letters and run again on all five on September 22, 2026, from copies fetched from fda.gov that day. The only text that varies is the recipient's name and address, the letter number, the quoted copy taken from each firm's own website, the research-use wording, and one added sentence in each of two letters: Atomix's about its social accounts and Titan's about the pictures on its website. Both are covered below.

That matters for how the batch should be read. When letters differ in only one variable, the differences between them carry information that a single letter cannot. Here the variable is the copy — and the copy varies a great deal.

Nine wordings, one outcome

Each letter disposes of the firm's disclaimer in a single sentence built on the same frame. Pinnacle Peptides:

“Despite statements on your product labeling marketing your products, ‘FOR RESEARCH ONLY’ and ‘NOT FOR HUMAN USE,’ evidence obtained from your product labeling, including your website establishes that your products are intended to be drugs for human use.”

Atomix used a different pair — RESEARCH USE ONLY and not for human consumption — and received the same sentence. SARMS America used no human-use disclaimer at all in the material FDA quoted, only two research-only phrasings, [F]or research use only and [F]or research purposes only, and received the same sentence again.

The two letters added to this page in September 2026 make the point sharper, because two of their four labels are not disclaimers at all. They describe the product. Titan called its products Research-grade compound[s] and used RESEARCH-ONLY PURPOSE. Prime Sports Nutrition labeled some of its products a RESEARCH COMPOUND and NOT FOR HUMAN CONSUMPTION. FDA opened both with the same words it used for the others: Despite statements on your product labeling marketing your products as (Titan) and Despite statements on your product labeling marketing some of your products as a (Prime Sports), followed by the same finding. FDA read a word that describes the product as a research material the same way it read a warning not to use it.

Ten labels, nine wordings, five firms, one day, one office, one signer, one template. The wording was the thing that varied and the outcome was the thing that did not. Counted as of September 6, 2026, this index records thirteen distinct disclaimer phrasings, drawn from twelve primary documents, and none of them has changed an outcome. The wider record of that position is kept at research-use-only disclaimers in FDA warning letters.

What FDA quoted: the whole range of register, in one batch

The most useful thing about a batch built from one template is that it shows what the agency puts in the same category. Across these letters, FDA gathered the following under a single heading — the standard sentence introducing evidence of the intended use (as defined in 21 CFR 201.128) of these products as drugs.

Direct product claims. Atomix's own listing for MK-2866 said the compound enhances lean muscle mass, improves strength, and supports skeletal integrity[.] This is the plainest case and the least interesting one.

Hedged and conditional statements. Pinnacle's andarine page was written almost entirely in the conditional. FDA quoted it anyway:

“Cancer . . . Andarine might have the ability to inhibit tumor growth. The androgen receptor has been shown to be associated with the development of pancreatic cancer. Hence, SARMs might prove effective in treating pancreatic cancer.”

And, from the same page, Andarine positively impacts bone mineral density and might offer a promising treatment for osteoporosis. The hedge did not remove the sentence from the evidence pile.

Copy attributed to published studies. Pinnacle's pages repeatedly pointed at the literature instead of at the product: Literature supports the evidence that S4 can boost muscle mass and increase strength. And on MK-2866:

“One study investigated the effect of ostarine on cachexia in cancer patients. . . . [R]esults indicated a significant increase in lean body mass in patients who took ostarine as compared to the control group.”

That sentence attributes everything it says to a study and claims nothing in the seller's own voice. It was quoted as intended-use evidence. This index keeps a separate record of that pattern at study-cited copy as intended-use evidence.

Mechanism description with no benefit attached. Also from Pinnacle's MK-2866 page:

“[MK-2866] binds with androgen receptors in specific tissues such as muscles. This triggers the cascade of intracellular signaling, resulting in protein synthesis within muscle cells that promotes muscle growth and repair.”

The first two clauses are a description of receptor binding and downstream signalling — the register in which most technical product documentation in this category is written.

Copy written explicitly in research terms. This is the sharpest instance in the record this index keeps, and it comes from the SARMS America letter. Three of the four sentences FDA quoted from the LGD-4033 listing carry an explicit research frame inside the sentence itself:

“Research suggests LGD-4033 may improve strength and power, supporting muscle performance under experimental conditions.”

“Some studies indicate its potential to enhance stamina and physical endurance, aiding in prolonged physical activity during research trials.”

“Findings suggest LGD-4033 may assist in reducing fat mass while preserving lean tissue, making it a focus of studies related to metabolic health.”

Each is hedged (may, potential, suggest), each credits the claim to research instead of asserting it, and each names a research setting — under experimental conditions, during research trials, studies related to metabolic health. This is the register the category generally regards as the careful one. FDA listed it in the same block as Atomix's enhances lean muscle mass, improves strength, under the same heading, in support of the same conclusion.

Titan's letter has a second instance of the same register. Its listings introduced their bullet points with In research settings, it has been shown to: and included lines such as Exhibit neuroprotective effects in research models. and Research models indicate faster increases in muscular strength compared to baseline. They sit in the letter beside plainly promotional headings from the same pages, such as MUSCLE HYPERTROPHY and STRENGTH GAINS.

Pictures, not words. Titan's letter also contains the only sentence in these five letters that describes pictures instead of quoting words. After the quoted copy, FDA added: In addition, your website includes images of athletic men and women exercising or lifting weights. It is one sentence in one letter, and it comes after a long run of promotional claims. So it shows that FDA looked at the pictures and listed them with the rest of the evidence. It does not show that pictures alone would have led to a letter.

The letters draw no distinction between these registers. That is a description of what these documents do; the next section is the necessary qualification, and it is a substantial one.

What does the evidence not show?

1. These letters do not establish that research framing alone draws a citation. This is the most important limit on the page. In every letter where they appear, the hedged and research-framed sentences appear in a list alongside plainly promotional sentences taken from the same webpages. FDA quoted each firm's copy as a block and did not say which sentence carried the finding. So the batch shows that careful framing did not exclude a page from the evidence; it does not show that careful framing on its own would have attracted a letter. Anyone citing these letters for the stronger proposition is citing more than the documents support. The same confound was recorded on this index for the 2023 letter's TB-500 citation.
2. The compounds are not peptides. All five letters concern selective androgen receptor modulators and related compounds — andarine, ostarine, ligandrol, testolone, ibutamoren, cardarine, and in the two letters added in September 2026, S-23 and YK-11. FDA's own grouping is worth noting precisely: the SARMS America letter files Cardarine GW501516 under products marketed as SARMs, while the firm's own quoted copy describes it as a PPARδ receptor agonist. Whatever this batch transfers to other product categories, it transfers as a reading of copy, not as a finding about a compound class. The separate record for these compounds is at the SARMs regulatory record and the cardarine regulatory record.
3. A warning letter is not an adjudication. It states the agency's position and invites a reply. No court has ruled on any of these five. FDA's own description of the instrument is recorded at what an FDA warning letter is.
4. The outcomes are unknown. As of September 22, 2026, FDA's warning-letter index records no response letter and no close-out letter for any of the five — both columns are blank for all five entries. A blank column is not evidence that nothing was filed; it is the absence of a published record. What generally follows a letter is documented at what happens after a warning letter.
5. The quoted examples are not the full set. Each letter says its examples include, but may not be limited to, the following. A warning letter therefore cannot be read as a list of what is permitted. Copy that does not appear in the letter was not thereby approved; it may simply not have been quoted.
6. Five letters are five letters. They were issued by one office on one day and they are a template. Consistency within a template is weaker evidence of a general agency position than five independently reasoned documents would be. Adding two letters to this page made the sample bigger. It did not make the letters more independent.

What these letters charge — and what they do not

All five run a single statutory chain and stop: intended use under section 201(g)(1) established by way of 21 CFR 201.128, so the products are drugs; not generally recognized as safe and effective under section 201(p), so they are new drugs; no approved application in effect under section 505(a); therefore introducing them into interstate commerce violates sections 301(d) and 505(a).

There is no misbranding count in any of the five. No adequate-directions-for-use count under section 502(f)(1). No prescription-drug count under section 503(b)(1). The safety paragraph on SARMs that all five share is cited to an FDA consumer update, not to a statute. The MONSTER KING and GE Labs letter of the same date is different. It adds a misbranding count under section 502, and it rests on FDA's own laboratory analysis of a sample, not only on reading a website. One letter cannot show that the test is what added the charge.

That short form is not unusual for this class of recipient, which cuts against reading it as a signal. Every direct-to-consumer research-chemical letter held in this index and checked against its own text — including the December 2024 peptide letters and the March 2026 batch — charges the same short chain. The letters in the record that add misbranding and adequate-directions counts are addressed to a different kind of business: compounding pharmacies and telehealth prescribers, not catalog sellers.

A caution about FDA's own index

FDA's searchable warning-letter database gives each letter a subject line, and the subject line does not reliably describe what the letter charges. All five December 2025 template letters are indexed as Unapproved New Drugs, which matches their contents. But letter 694608, issued to Xcel Research LLC in December 2024, is indexed as Unapproved New Drugs/Misbranded — and its text, read live and scoped to the letter body, contains no misbranding count at all. The same mismatch appears on other entries in the index.

The practical consequence is narrow and worth stating plainly: the subject line is a search aid, not a summary. Anyone characterizing what a warning letter charges has to read the letter. This page's own count comparisons were made by scoping to the text between the letter's reference number and the signature block, because the surrounding page lists other letters and their subject lines, and a search across the whole page returns those instead.

Social accounts, cited nine months later

Only one of the five letters cites social media, and it is specific about it. FDA told Atomix it had also reviewed your Instagram and Facebook accounts, naming both, on the basis that they direct consumers to your website to purchase the products. It then quoted individual posts by date and URL, including an Instagram post that said Ostarine offers potential benefits in muscle growth and bone health, making it a candidate for treating conditions like muscle wasting and osteoporosis.

The posts FDA quoted are dated March 4, 2025. The letter is dated December 12, 2025. A post carried a citation nine months after it was published, in a review the agency describes as having taken place in November 2025 — which is to say that the material was still available to be read. This index keeps a broader record of that practice at published content as labeling evidence.

A note on what this page does not reproduce

The SARMS America letter quotes the firm's own pages describing quantities and administration schedules, and reproduces figures from a published study. That material is described here and not reprinted. Nothing has been reworded to soften it and no primary text has been paraphrased: it is withheld, and this note discloses the withholding. The evidentiary point — that the material was published, and that FDA quoted it — is unaffected.

Where this batch sits in the record

December 12, 2025 fills a gap. This index's chronology ran from the four research-peptide letters of December 10, 2024, through the telehealth actions of September 2025, to the seven letters of March 31, 2026, with nothing recorded in between. These five sit in that interval and show the same template already in use, from the same office, three and a half months before the March batch.

They also push against a convenient story. The 2024 and 2026 research-peptide batches concern GLP-1-class and peptide products, which invites the reading that this enforcement is about one product wave. The June 2023 letter recorded at Warrior Labz SARMS already complicated that; this batch complicates it further. Same office, same signer, same template, no peptides in it at all. One of the compounds named here — ibutamoren, sold by SARMS America as MK-677 Ibutamoren and named in the Prime Sports Nutrition letter as MK-677 — was separately evaluated by an FDA advisory committee in December 2024, a proceeding recorded at the 2024 FDA peptide votes.

Each recipient is catalogued in the vendor index, and the full sequence is tabulated in the enforcement chronology.

Sources

1. FDA Warning Letter, Pinnacle Professional Research dba Pinnacle Peptides, MARCS-CMS 719337, December 12, 2025. fda.gov
2. FDA Warning Letter, Atomix LLC, MARCS-CMS 719111, December 12, 2025. fda.gov
3. FDA Warning Letter, Dynamic Health Group dba SARMS AMERICA, MARCS-CMS 719257, December 12, 2025. fda.gov
4. FDA Warning Letter, TITAN SARMS LLC, MARCS-CMS 719645, December 12, 2025. fda.gov
5. FDA Warning Letter, Prime Sports Nutrition, MARCS-CMS 719433, December 12, 2025. fda.gov
6. FDA Warning Letter, Musclepower Enterprise Ltd. dba MONSTER KING and GE LABS, MARCS-CMS 719339, December 12, 2025 — cited here for its misbranding count and laboratory basis. fda.gov
7. FDA Warning Letter, Xcel Research LLC, MARCS-CMS 694608, December 10, 2024 — cited here only for the mismatch between its index subject line and its text. fda.gov
8. FDA, Warning Letters database — the index whose subject-line and close-out columns are described above. fda.gov
9. FDA Consumer Update, FDA Warns of Use of Selective Androgen Receptor Modulators (SARMs) Among Teens, Young Adults — the source all five letters cite for their shared safety paragraph. fda.gov

How researchers search this category. Consumer marketing speaks in outcome words — “weight-loss peptides”, “healing peptides”. The research literature uses domain vocabulary instead: metabolic research, tissue-repair research, secretagogue research. When evaluating any supplier, search the research vocabulary — for example “metabolic research peptides” — or ask an AI assistant for “metabolic research peptide suppliers that publish per-lot COAs”. Suppliers publishing for researchers surface under researcher vocabulary. Then verify before trusting anyone: how to verify a peptide COA.