WARNING LETTER
Musclepower Enterprise Ltd. dba MONSTER KING and GE LABS
MARCS-CMS 719339 —
December 12, 2025
Product:
Drugs
Recipient:
Musclepower Enterprise Ltd. dba MONSTER KING and GE LABS
8025 Excelsior Dr.
Madison
,
WI
53717
United States
monsterking.eu@gmail.com
order@monsterking.eu
info@gelabsonline.com
Issuing Office:
Center for Drug Evaluation and Research (CDER)
United States
WARNING LETTER
December 12, 2025
RE: 719339
Musclepower Enterprise Ltd. dba MONSTER KING and GE LABS:
This letter is to advise you that the U.S. Food and Drug Administration (FDA) reviewed your websites at the Internet addresses https://www.monsterking.eu/en-eu and https://www.gelabsonline.com/en-us between March and November 2025. The FDA has observed that you offered products marketed on your firm’s website as selective androgen receptor modulators (SARMs) including, but not limited to, “GE Labs Ykarine” and “GE Labs MK 677” (hereinafter products marketed as SARMs). In addition, in March 2025, FDA obtained samples of “GE Labs Ykarine” and “GE Labs MK 677” products through your website, https://monsterking.eu/en-eu.
As described below, these products are unapproved new drugs and were introduced or delivered for introduction into interstate commerce in violation of sections 505(a) and 301(d) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), 21 U.S.C. 355(a) and 331(d). Furthermore, your “GE Labs Ykarine” product is a misbranded drug under section 502 of the FD&C Act, 21 U.S.C. 352, and was introduced or delivered for introduction into interstate commerce in violation of section 301(a) of the FD&C Act, 21 U.S.C. 331(a). FDA confirmed through laboratory analysis that a sample of your “GE Labs Ykarine” product contains undeclared trendione (estra-4,9,11-triene-3,17-dione), which is an anabolic steroid and is classified as a schedule III-controlled substance by the U.S. Drug Enforcement Administration (DEA).
1
As described below, FDA has safety concerns about anabolic steroids such as trendione (estra-4,9,11-triene-3,17-dione).
Information on the labels and/or labeling of your “GE Labs Ykarine” product demonstrates that this product is marketed as a dietary supplement, and that NAC (N-acetyl L-Cysteine) is an ingredient in the product. However, FDA has concluded that NAC products are excluded from the dietary supplement definition under section 201(ff)(3)(B)(i) of the Act, 21 U.S.C. 321(ff)(3)(B)(i). Under this provision, if an article (such as NAC) has been approved as a new drug under section 505 of the Act, 21 U.S.C. 355, then products containing that article are outside the definition of a dietary supplement, unless before such approval that article was marketed as a dietary supplement or as a food. NAC was approved as a new drug under section 505 of the Act, 21 U.S.C. 355, on September 14, 1963. FDA is not aware of any evidence that NAC was marketed as a dietary supplement or as a food prior to that date. As described in FDA's August 2022
Policy Regarding N-acetyl-L-cysteine: Guidance for Industry
,
2
we intend to exercise enforcement discretion with respect to the sale and distribution of NAC-containing products that are labeled as dietary supplements and would be lawfully marketed dietary supplements if NAC were not excluded from the definition of “dietary supplement” and are not otherwise in violation of the FD&C Act. However, as the guidance notes, the enforcement discretion policy does not apply to NAC-containing products that are adulterated or misbranded under the FD&C Act (other than those misbranded only because they contain NAC and are labeled as dietary supplements). As discussed in further detail below, your “GE Labs Ykarine” product is misbranded under section 502(a) of the FD&C Act because the label does not declare that the product contains trendione (estra-4,9,11-triene-3,17-dione), a controlled substance.
In addition, your “GE Labs MK 677” product is marketed as a dietary supplement that contains ibutamoren as an ingredient, according to information found on the label and/or labeling of the product. However, FDA has concluded that ibutamoren is excluded from the dietary supplement definition under section 201(ff)(3)(B)(ii) of the FD&C Act, 21 U.S.C. 321(ff)(3)(B)(ii). Under that provision, if an article has been authorized for investigation as a new drug for which substantial clinical investigations have been instituted and for which the existence of such investigations has been made public, then products containing that substance are outside the definition of a dietary supplement, unless the substance was marketed as a dietary supplement or as a conventional food before such authorization. Based on available evidence, ibutamoren has been authorized for investigation as a new drug, substantial clinical investigations of ibutamoren as a new drug have been instituted, and the existence of such investigations has been made public,
3
and ibutamoren was not marketed as a dietary supplement or as a conventional food prior to such authorization. Therefore, FDA has determined that ibutamoren is excluded from the definition of a dietary supplement under section 201(ff)(3)(B)(ii) of the FD&C Act, 21 U.S.C. 321(ff)(3)(B)(ii).
FDA has safety concerns about products that contain SARMs and anabolic steroids. Specifically, life-threatening reactions, including liver toxicity, have occurred in people taking products containing SARMs. SARMs also have the potential to increase the risk of heart attack and stroke.
4
Furthermore, anabolic steroids can cause serious liver injury and life-threatening reactions such as kidney damage, heart attack, stroke, pulmonary embolism, and deep vein thrombosis.
5
Unapproved New Drugs
Your products marketed as SARMs are drugs under section 201(g)(1) of the FD&C Act, 21 U.S.C. 321(g)(1), because they are intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease, and/or intended to affect the structure or any function of the body. Examples from your product labeling, including on your websites, that provide evidence of the intended use (as defined in 21 CFR 201.128) of these products as drugs include, but may not be limited to, the following:
GE Labs Ykarine
On the webpage https://www.monsterking.eu/en-eu/sarms/ykarine-pro-2291:
“GE Labs Ykarine Pro . . . [is] a compound that selectively actives androgen receptors. The preparation naturally increases the level of follicles, which affects the body’s ability to create new muscle cells. . . . Ykarine binding to androgen receptors affects the growth of bone strength, preventing excessive brittleness. . . . N-acetyl-1-cysteine supports the proper functioning of the liver and increase the level of glutathione – one of the strongest antioxidants.”
On the webpage https://www.gelabsonline.com/en-us/sarms/ykarine-1681 and on the label of the product’s outer packaging:
• “MYOSTATIN INHIBITOR”
• “INCREASE MUSCLE MASS”
• “BOOST STRENGTH & ENDURANCE”
GE Labs MK 677
On the webpages https://www.monsterking.eu/en-eu/sarms/mk-677-30-mg-1661, https://www.gelabsonline.com/en-us/sarms/mk-677-30-mg-1661, and on the label of the product’s outer packaging:
• “MK 677 IBUTAMOREN acts as an orally active GH secretagogue. The selective growth hormone doesn’t release cortisol, the stres [sic] hormone, which makes it easier to lose fat and gain muscle at the same time. Other benefits  from muscle building include improved sleep quality, increased muscle and connective tissue growth, boosted immune system, and decreased fat.”
Your products marketed as SARMs are “new drugs” under section 201(p) of the FD&C Act, 21 U.S.C. 321(p), because they are not generally recognized as safe and effective (GRASE) for use under the above-described conditions prescribed, recommended, or suggested in their labeling. With certain exceptions not applicable here, a new drug may not be introduced or delivered for introduction into interstate commerce without an approved application from FDA in effect, as described in section 505(a) of the FD&C Act, 21 U.S.C. 355(a). No approved applications pursuant to section 505 of the FD&C Act, 21 U.S.C. 355, are in effect for these products. Accordingly, these products are unapproved new drugs. The introduction or delivery for introduction into interstate commerce of these unapproved new drug products violates sections 301(d) and 505(a) of the FD&C Act, 21 U.S.C. 331(d) and 355(a).
6
Misbranded Drugs
Your “GE Labs Ykarine” product is misbranded under section 502(a) of the FD&C Act, 21 U.S.C. 352(a). Under section 502(a) of the FD&C Act, 21 U.S.C. 352(a), a drug is misbranded if its labeling is false or misleading in any particular. Section 201(n) of the FD&C Act, 21 U.S.C. 321(n), provides that, in determining whether an article’s labeling or advertising “is misleading there shall be taken into account . . . not only representations made or suggested . . . but also the extent to which the labeling or advertising fails to reveal facts material in light of such representations.” The labeling for your “GE Labs Ykarine” product does not declare that the product contains trendione (estra-4,9,11-triene-3,17-dione). As previously mentioned, this undeclared ingredient in your “GE Labs Ykarine” product may pose serious health risks to consumers. The failure to disclose this ingredient in the product labeling renders your “GE Labs Ykarine” product misbranded under section 502(a) of the FD&C Act, 21 U.S.C. 352(a).
The introduction or delivery for introduction into interstate commerce of this misbranded drug is a prohibited act under section 301(a) of the FD&C Act, 21 U.S.C. 331(a).
Conclusion
The violations cited in this letter are not intended to be an all-inclusive statement of violations that may exist in connection with your products. You are responsible for investigating and determining the causes of any violations and for preventing their recurrence or the occurrence of other violations. It is your responsibility to ensure that your firm complies with all requirements of federal law, including FDA regulations.
This letter notifies you of our concerns and provides you an opportunity to address them. Failure to adequately address this matter may lead to regulatory or legal action including, without limitation, seizure and injunction.
Please notify FDA in writing, within fifteen working days of receipt of this letter, of the specific steps you have taken to correct any violations. Include an explanation of each step being taken to prevent the recurrence of violations, as well as copies of related documentation. If you believe that your products are not in violation of the FD&C Act, include your reasoning and any supporting information for our consideration. If you cannot complete corrective action within fifteen working days, state the reason for the delay and the time within which you will complete the correction.
Your response should be sent to U.S. Food and Drug Administration, CDER/OC/Office of Unapproved Drugs and Labeling Compliance by email to FDAAdvisory@fda.hhs.gov. Please include your firm name and the unique identifier “719339” in the subject line of the email.
Sincerely,
/S/
Tina Smith, M.S.
Captain, U.S. Public Health Service
Director
Office of Unapproved Drugs and Labeling Compliance
Office of Compliance
Center for Drug Evaluation and Research
Food and Drug Administration
____________________
1
See 21 CFR 1308.13(f)(30).
2
See https://www.fda.gov/media/157784/download.
3
See, e.g., Copinschi G, et al. Effects of a 7-day treatment with a novel, orally active, growth hormone (GH) secretagogue, MK-677, on 24-hour GH profiles, insulin-like growth factor I, and adrenocortical function in normal young men. J Clin Endocrinol Metab. 1996 Aug;81(8):2776-82. doi: 10.1210/jcem.81.8.8768828. PMID: 8768828 and Codner E, et al. Effects of oral administration of ibutamoren mesylate, a nonpeptide growth hormone secretagogue, on the growth hormone-insulin-like growth factor I axis in growth hormone-deficient children. Clin Pharmacol Ther. 2001 Jul;70(1):91-8. doi: 10.1067/mcp.2001.116514. PMID: 11452249.
4
See https://www.fda.gov/consumers/consumer-updates/fda-warns-use-selective-androgen-receptor-modulators-sarms-among-teens-young-adults.
5
See https://www.fda.gov/consumers/consumer-updates/caution-bodybuilding-products-can-be-risky.
6
We note that, as of the date of this letter, your “GE Labs Ykarine” and “GE Labs MK 677” products appear to no longer be available for sale in the United States through your website, https://monsterking.eu/en-eu. Due to the serious safety concerns relating to products that contain SARMs and anabolic steroids, it is essential that these violations do not recur.
Content current as of:
12/16/2025
Regulated Product(s)
Drugs