MK-777 (Acetamoren)

MK-777, listed as Acetamoren, is Free Muscle's own product designation for a capsule in our Bioreactive Series, placed in the growth hormone secretagogue category alongside MK-677 (ibutamoren). It is important to say at the outset what that name is and is not: MK-777 and Acetamoren are not names that appear in the published pharmacological literature, and there are no trials under them. Other sellers use the same names, often with "next-generation MK-677" claims that no published study supports. This page lists every MK-777 product we stock, compared on pack size and batch testing, and explains what can and cannot be verified. Research use only, 18+.

What is MK-777?

MK-777 (Acetamoren) is a product designation, not an established compound name. The letters and numbers echo the Merck development codes used for ibutamoren (MK-677, MK-0677), and the suffix "-moren" echoes the growth hormone secretagogue naming pattern, but neither MK-777 nor Acetamoren has an International Nonproprietary Name, a CAS registry entry under that label, or a development history you can look up. If you search the medical databases for it you will find nothing, and any website that presents a detailed pharmacology for MK-777 is describing something it cannot source.

Two CAS numbers are often printed beside the name online, and neither leads to MK-777. In PubChem, checked on 2 October 2026, CAS 950841-87-9 is registered to N-acetyl ibutamorelin (CID 57595228, C29H38N4O6S, molecular weight 570.7), which is ibutamoren carrying an acetyl group on its amine and is linked to patents but to no published papers. CAS 1797406-69-9 belongs to MZ1 (CID 122201421, C49H60ClN9O8S2, molecular weight 1002.6), a protein-degrader research compound with no connection to growth hormone. Neither record lists MK-777 or Acetamoren as a synonym. A number printed on a listing does not show what a batch contains; the identity result on its certificate of analysis does.

What can be said is limited to the classification and the testing. Free Muscle places MK-777 within the growth hormone secretagogue category of the Bioreactive Series, our own-brand line that also includes RAD-150 (TLB-150) and NitraGlyc. Each Bioreactive Series batch is assayed by Janoshik Analytical, and the Certificate of Analysis for a batch is the one document that states what was identified in the capsules and at what purity. We do not attach a receptor profile, a half-life or a trial record to MK-777, because none has been published under that name.

The class it sits in does have a literature. Growth hormone secretagogues act at the growth hormone secretagogue receptor GHS-R1a, cloned in 1996 and later identified as the receptor for the stomach hormone ghrelin. The compound in that class with the deepest human record is MK-677, and if a published trial history matters to your research, that is the compound to look at. Our MK-677 collection compares every brand of it we stock.

What the published research reports

There is no published research on MK-777 or Acetamoren, and this page will not pretend otherwise. What exists is the literature on the receptor class the product is filed under, summarised here so the classification means something.

Howard and colleagues (1996) cloned a G protein-coupled receptor from pig and human pituitary and hypothalamus and showed it to be the target of the synthetic growth hormone secretagogues, defining a neuroendocrine pathway for pulsatile growth hormone release that was distinct from growth hormone releasing hormone. Kojima and colleagues (1999) then purified the receptor's endogenous ligand from rat stomach, a 28-amino-acid acylated peptide they named ghrelin, and showed that the acyl group at serine 3 was essential for activity.

For the class in humans, the two-year randomised trial of MK-677 in 65 healthy older adults by Nass and colleagues (2008) is the reference point. Fat-free mass rose by about 1.1 kg against a 0.5 kg fall on placebo, with no change in visceral fat, strength or function; fasting glucose and cortisol rose, insulin sensitivity fell, and increased appetite, transient oedema and muscle pain were the most frequent side effects. Those results belong to MK-677 in that trial population. They cannot be transferred to MK-777, and none of this is a claim about the product listed below.

Brands of MK-777 we stock

• MK-777 (Acetamoren) Bioreactive Series: Free Muscle brand, capsule form, 60 capsules per bottle. Each batch is assayed for identity and purity by Janoshik Analytical, with the certificate sent on request. The listing states the declared quantity per capsule where one is given; if it is not given, we do not invent one here.

Other sellers also use the MK-777 and Acetamoren names, and a shared name is not evidence of shared contents: compare the identity result on each batch certificate, not the label. This collection holds our single listing. The Bioreactive Series as a whole, including RAD-150 and NitraGlyc, is at Bioreactive Series.

How to compare them

With one product in the collection, the comparison that matters is against MK-677. Take the strength per capsule from each listing, multiply by the capsule count to get total milligrams per bottle, and divide the price on the listing by that total. Then ask a harder question than price: which product has a published record that lets you interpret your results? MK-677 has one; MK-777 does not. A batch certificate tells you what is in the bottle, but it cannot supply a literature that does not exist. Our article on price per milligram covers the arithmetic.

Batch testing and certificates of analysis

For a product with no published literature, the Certificate of Analysis carries more weight than usual, because it is the only independent statement about what the capsules contain. Every Free Muscle batch, including every Bioreactive Series batch, is sent to Janoshik Analytical, an independent laboratory. The certificate names the batch, reports the identity of the compound found against a reference standard and states the measured purity, with the test date and laboratory details. Email us the batch number printed on your label together with the product name and we send the certificate for that batch. A generic PDF without a batch number, or one that predates the batch in your hand, is not a batch certificate. See how we test and how to read a COA.

Legal status in the UK

MK-777 (Acetamoren) is not a licensed medicine in the UK and has no MHRA marketing authorisation. It is not an authorised food supplement or novel food, and it cannot be sold for human consumption. Free Muscle supplies it for laboratory research only, to adults aged 18 or over. The WADA Prohibited List bans growth hormone secretagogues as a class under section S2, listing ibutamoren by name and covering related compounds with similar biological effect, so anyone subject to anti-doping rules should treat any product in this category as prohibited at all times. Our MK-677 legal status page sets out the UK position for the class.

Storage and handling

Keep the bottle sealed in a cool, dry place away from light and heat, and reseal after opening. Do not decant capsules into unlabelled containers. Record the batch number on receipt so a certificate request can be matched to the exact material. Keep out of reach of children and pets and apply normal laboratory good practice when handling.

Delivery and returns

Free Muscle is the trading name of FreeMuscle, a business registered in Andorra, with UK operations and dispatch in Scunthorpe. Orders ship with free tracked UK delivery in plain packaging, and orders placed before 2pm Monday to Friday are processed the same working day. EU delivery takes 3 to 7 working days. Unopened items can be returned within 30 days. See delivery and our 30-day guarantee.

Related reading

• MK-777 (Acetamoren): what the name means and how it relates to MK-677
• MK-677 (Ibutamoren): What the Research Says
• How to Read a Certificate of Analysis (COA)
• What Is Janoshik Analytical? Third-Party Testing Explained
• Price per milligram: the only honest way to compare SARMs and peptides

• MK-677 (Ibutamoren), all brands
• Bioreactive Series
• RAD-150 (TLB-150)
• Ipamorelin

References

• Howard AD, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996;273(5277):974-977. PMID: 8688086.
• Kojima M, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402(6762):656-660. PMID: 10604470.
• Nass R, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149(9):601-611. PMID: 18981485.

Last reviewed: October 2026.

Research compounds sold by Free Muscle are supplied for laboratory research use only and are not for human consumption. They are not authorised as medicines by the MHRA, EMA or FDA, are not food supplements, and are sold only to adults aged 18 or over. Nothing on this page is medical or dosing advice. Summaries of published research describe study findings and are not claims about any product.