MK-677 Regulatory Status in 2026
A plain-language look at where a widely discussed compound actually stands with regulators.
TL;DR
MK-677 (ibutamoren, an oral compound studied for growth hormone support) is not FDA-approved as a drug. It was not removed from FDA's Category 2 in April 2026. As of September 14, 2026, MK-677 is in FDA's 503A Category 2, and it is not on the 503A bulk drug substances list.
MK-677 regulatory status: is MK-677 FDA approved?
MK-677 is not FDA-approved as a drug for any use, including growth hormone support or muscle preservation. A pharmaceutical company studied it for frailty in older adults years ago. That program ended before the FDA reviewed it for approval (FDA PCAC Briefing Document, 2026). A 2008 randomized trial of MK-677 in 65 older adults found it roughly doubled IGF-1 levels over two years, a marker physicians use to track growth hormone activity (Nass et al., Annals of Internal Medicine, 2008). No approved, mass-manufactured MK-677 drug exists.
Is MK-677 legal in 2026?
MK-677 is still in FDA's 503A Category 2. Category 2 lists substances FDA says raise significant safety risks. FDA placed MK-677 there in September 2023. On April 22, 2026, FDA removed 12 other peptides from Category 2 after their nominations were withdrawn. MK-677 was not one of them. On April 15, 2026, a post on X by the Secretary of the U.S. Department of Health and Human Services (HHS, the federal agency that oversees the FDA) wrongly listed ibutamoren (MK-677) among the 12. As of September 14, 2026, MK-677 is in Category 2 and is not on the 503A bulks list.
Why isn't MK-677 on the 503A bulk drug list yet?
The 503A bulk drug substances list (in plain English: the FDA's roster of raw ingredients pharmacies can compound with) does not include MK-677. Getting added requires review by the Pharmacy Compounding Advisory Committee (PCAC), an outside panel of experts who evaluate the science and vote on a recommendation. At its October 29, 2024 meeting, the PCAC voted against adding ibutamoren (MK-677) to the list. MK-677 was not on the agenda of the committee's July 23–24, 2026 meeting.
Who asks about MK-677's regulatory status
People come to this topic wanting a straight answer before starting a protocol: is this legal, is it approved, and what happens if the rules change. Regulatory status for compounded peptides has shifted multiple times in two years, and knowing where a compound sits today helps set realistic expectations.
The Halftime POV
We would rather explain a regulatory gray zone honestly than paper over it. MK-677's story right now is "still in Category 2." That status matters if you are deciding whether to start a protocol. We track FDA and HHS updates closely so our guidance reflects where things actually stand.
Related reading:
- Who Asks About MK-677
- What Is a 503A Pharmacy
- 503A Pharmacy Regulations: The DQSA Framework
- Sermorelin Regulatory Status
FAQ
Is MK-677 FDA approved? No. MK-677 (ibutamoren) is not FDA-approved as a drug for any use. It was studied for muscle wasting and frailty, but that development program was dropped before approval. No approved, manufactured MK-677 drug product exists.
Is MK-677 legal in 2026? MK-677 (ibutamoren) is not FDA-approved. FDA placed it in 503A Category 2 in September 2023, and FDA did not remove it in 2026. As of September 14, 2026, MK-677 is in Category 2, which lists substances FDA says raise significant safety risks. It is not on the 503A bulk drug substances list.
Why isn't MK-677 on the 503A bulk drug list yet? Getting onto that list requires a scientific review by the FDA's Pharmacy Compounding Advisory Committee (PCAC). At its October 29, 2024 meeting, the committee voted against adding ibutamoren (MK-677) to the list. MK-677 was not among the 12 peptides FDA removed from Category 2 in April 2026, and it was not on the agenda of the committee's July 23–24, 2026 meeting.
What is MK-677 studied for? MK-677 is studied as a ghrelin receptor agonist, activating the same receptor as the hunger hormone ghrelin to signal the pituitary gland to release more growth hormone. A 2008 randomized trial in older adults found it roughly doubled IGF-1 levels over two years.
Disclaimer
This article is educational and is not medical advice. Compounded medications are not FDA-approved. Clinical outcomes depend on individual factors and require physician evaluation. Results vary.
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We share what we learn along the way — the research, the regulations, the real-world trade-offs. Get started with Halftime Health.
Sources
- U.S. Food and Drug Administration, Pharmacy Compounding Advisory Committee Briefing Document, 2026: https://www.fda.gov/media/182087/download
- Nass, R., et al. "Effects of an Oral Ghrelin Mimetic on Body Composition and Clinical Outcomes in Healthy Older Adults." Annals of Internal Medicine, 2008: https://pubmed.ncbi.nlm.nih.gov/18981487/
- U.S. Food and Drug Administration, Bulk Drug Substances Nominated for Use in Compounding: https://www.fda.gov/drugs/human-drug-compounding/bulk-drug-substances-nominated-use-compounding
Frequently asked questions
Is MK-677 FDA approved?
No. MK-677 (ibutamoren) is not FDA-approved as a drug for any use. It was studied by a pharmaceutical company for muscle wasting and frailty, but that development program was dropped before approval. No approved, manufactured MK-677 drug product exists.
Is MK-677 legal in 2026?
MK-677 (ibutamoren) is not FDA-approved. FDA placed it in 503A Category 2 in September 2023, and FDA did not remove it in 2026. As of September 14, 2026, MK-677 is in Category 2, which lists substances FDA says raise significant safety risks. It is not on the 503A bulk drug substances list.
Why isn't MK-677 on the 503A bulk drug list yet?
Getting onto that list requires a scientific review by the FDA's Pharmacy Compounding Advisory Committee (PCAC), a panel of outside experts who evaluate the evidence and vote on a recommendation. At its October 29, 2024 meeting, the committee voted against adding ibutamoren (MK-677) to the list. MK-677 was not among the 12 peptides FDA removed from Category 2 in April 2026, and it was not on the agenda of the committee's July 23–24, 2026 meeting.
What is MK-677 studied for?
MK-677 is studied as a ghrelin receptor agonist, meaning it activates the same receptor as the hunger hormone ghrelin, which in turn signals the pituitary gland to release more growth hormone. A 2008 randomized trial in older adults found it roughly doubled IGF-1 levels over two years, a marker physicians use to track growth hormone activity.
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