Description
PrymaLab · Research use only
YK-11 5mg Capsules
A steroidal partial agonist of the androgen receptor, 5 mg per capsule
YK-11 is a synthetic steroid that acts as a partial agonist of the androgen receptor and is usually sold with the selective androgen receptor modulators (SARMs). It is not a peptide. This listing is a bottle of hard gelatin capsules, each holding 5 mg of YK-11 blended with microcrystalline cellulose. All of the published work on YK-11 in the references here was done in cell culture, in reporter-gene assays and in C2C12 myoblasts, and none of it in animals or people.
Specifications
| Property | Value |
|---|---|
| Compound | YK-11 (YK11, steroidal SARM / myostatin inhibitor) |
| CAS number | 1370003-76-1 |
| Molecular formula | C25H34O6 |
| Contents | YK-11: 5 mg per capsule |
| Form | Hard gelatin capsules containing the active substance blended with microcrystalline cellulose, packed in a sealed bottle |
| Storage, sealed | Store at room temperature (15–25 °C) in the tightly closed original container, dry and protected from light |
| Safety data sheet | PL-SDS-189 |
What is in each capsule
The safety data sheet gives 5 mg of YK-11 per capsule, about 1.2% of the capsule contents by weight, with microcrystalline cellulose filling the rest of a gelatin shell. The compound’s full name is (17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester, a modified 19-norpregnane steroid with the formula C25H34O6. It is classified as suspected of damaging fertility or the unborn child (H361), and the sheet asks for the bottle to be stored locked up. Keep it tightly closed in the original container at 15 to 25 °C, dry and away from light.
What the research covers
A partial agonist that skips a receptor step
Kanno and colleagues reported in 2011 that YK-11, a new steroid compound, was a partial agonist of the androgen receptor in a luciferase reporter assay1. It sped up the receptor’s move into the nucleus but did not induce the interaction between the receptor’s amino- and carboxy-terminal domains, and it blocked that interaction when DHT was present1. The authors linked the missing N/C interaction to the partial agonism1. In MDA-MB 453 cells the size of YK-11’s effect relative to a full androgen varied from gene to gene, which led them to suggest it might act as a SARM1.
The myostatin link, and how indirect it is
In 2013 the same group found that YK-11 drove C2C12 myoblasts to differentiate, inducing the myogenic regulatory factors MyoD, Myf5 and myogenin more strongly than DHT did2. YK-11, unlike DHT, raised expression of follistatin, and an antibody against follistatin reversed the differentiation2. Follistatin binds myostatin directly and with high affinity, and in chick limb cultures it blocked myostatin’s inhibition of muscle differentiation3. That chain is why YK-11 is sold as a myostatin inhibitor. If it acts on myostatin at all, it does so one step removed, through follistatin: none of these references reports YK-11 binding myostatin or shows the follistatin effect outside a culture dish.
What is not established
No animal or human study of YK-11 is among the references here, so nothing is known from them about its absorption, metabolism, selectivity in a living animal or safety. Its classification as a SARM rests on reporter-gene behaviour in cell lines; structurally it is a steroid. The guide to SARMs versus peptides has a section on YK-11 and why the SARM label fits it poorly.
How each lot is tested
Every lot is tested in PrymaLab’s own laboratory in Ashland, Kentucky before release. Published certificates are listed on the results page and can be checked by number and key on the verify page. These are in-house results from PrymaLab Analytical, not an independent test, and the lab is not accredited to ISO 17025. The third-party testing guarantee on this page still applies: if any independent laboratory finds the wrong compound, or less than the stated purity or amount, the order is refunded and the cost of the test is reimbursed.
Frequently asked questions
Is YK-11 a SARM or a steroid?
Structurally it is a steroid, built on a 19-norpregnane skeleton. Its developers proposed it as a SARM because it activated the androgen receptor only partially and its effect varied from gene to gene in cell assays. Both labels appear in the literature, and they describe different things.
Does YK-11 inhibit myostatin?
Not directly, on the evidence cited here. In cultured myoblasts it raised follistatin, a protein that binds myostatin, and blocking follistatin reversed its effect on differentiation. No study cited here shows YK-11 binding myostatin, and none measured the effect in animals.
How should the bottle be stored?
Locked up and tightly closed in the original container at 15 to 25 °C, dry and protected from light, as the safety data sheet asks. The sheet classifies YK-11 as a suspected reproductive toxicant, so opened capsules should be handled with that in mind.
Has YK-11 been studied in animals or people?
Not in any reference on this page; the published work is cell culture only. There are therefore no animal or human safety data at all. The capsules are sold for laboratory research and must not be consumed by, or given to, people or animals.
References
- Kanno Y, Hikosaka R, Zhang SY, et al. (17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester (YK11) is a partial agonist of the androgen receptor. Biol Pharm Bull. 2011;34(3):318-23. DOI · PubMed
- Kanno Y, Ota R, Someya K, et al. Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression. Biol Pharm Bull. 2013;36(9):1460-5. DOI · PubMed
- Amthor H, Nicholas G, McKinnell I, et al. Follistatin complexes Myostatin and antagonises Myostatin-mediated inhibition of myogenesis. Dev Biol. 2004;270(1):19-30. DOI · PubMed
Research use only
For laboratory research use only. YK-11 5mg Capsules is not a drug, food, cosmetic or dietary supplement, is not approved by the FDA or any comparable authority for human or veterinary use, and must not be given to people or animals. It is sold to qualified researchers and institutions, and the buyer is responsible for lawful handling and disposal.
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