MK-677 (Ibutamoren) FDA Approval History

MK-677 Has Never Been FDA Approved

No FDA approval for MK-677 exists. The compound was developed by Merck Research Laboratories in the early 1990s as an orally active growth hormone secretagogue, but the company halted clinical development before filing a new drug application. MK-677 remains classified as an investigational compound with no approved labeling, no approved indication, and no marketing authorization from any major regulatory body worldwide [1].

No NDA Has Been Filed

The FDA's Drugs@FDA database contains no record of an NDA or biologics license application (BLA) for ibutamoren. A search of the FDA's Orange Book yields the same result. Without an NDA, MK-677 has no approved prescribing information, no FDA-reviewed safety data package, and no approved manufacturing process under current Good Manufacturing Practice (cGMP) standards [2].

Why Development Stalled

Merck's decision to discontinue MK-677 development appears linked to clinical endpoints. While the compound reliably increased growth hormone (GH) and insulin-like growth factor 1 (IGF-1) levels, the two-year study by Murphy et al. (1998) showed that sustained GH elevation in older adults did not translate into the functional improvements the program needed for regulatory approval. Body composition changed modestly. Fat-free mass increased by 1.6 kg over two years in the MK-677 group compared to placebo, but this failed to produce meaningful gains in strength or physical performance [1].

The FDA requires that drugs demonstrate not just biomarker changes but clinically meaningful outcomes. A rise in IGF-1 alone does not satisfy approval criteria for indications such as sarcopenia or frailty. That gap between biomarker response and functional benefit is the core reason MK-677 never advanced.

Clinical Trial Record

MK-677's investigational history spans roughly a decade, from first-in-human pharmacokinetic studies in the early 1990s through longer-duration efficacy trials published by 2008. The compound showed consistent pharmacologic activity but no clear path to a registrational endpoint.

Early Phase I/II Studies (1995-1998)

Chapman et al. (1996) published one of the earliest controlled studies. In a cohort of obese males, a single oral dose of MK-677 (25 mg) increased 24-hour mean GH concentrations by approximately 55% and peak GH levels by 79% compared to placebo [3]. The GH response was dose-dependent and reproducible across repeated dosing.

The Murphy et al. Two-year trial enrolled 65 healthy older adults (ages 60 to 81) and remains the longest published controlled study of MK-677. At 25 mg daily, ibutamoren increased serum IGF-1 levels to those typical of younger adults. Specifically, mean IGF-1 rose by approximately 40% from baseline and remained elevated throughout the study period [1]. Fasting glucose increased modestly (by about 0.3 mmol/L), a signal that would later become a regulatory concern.

The Nass et al. Two-Year Extension

Nass et al. (2008) conducted a separate two-year, randomized, double-blind trial in 65 healthy older adults ages 60 to 81. MK-677 at 25 mg/day increased GH pulse amplitude by 1.8-fold and IGF-1 by 40.4% at 12 months [4]. Body weight increased, driven by both fat-free mass gains (approximately 1.1 kg) and fluid retention. Fasting blood glucose rose significantly, with two subjects developing glucose levels meeting diabetes diagnostic criteria during the treatment period [4]. The authors concluded that while GH and IGF-1 restoration was achievable, "the anabolic effects were modest and the metabolic effects raise safety concerns" for chronic use in elderly populations.

What the FDA Has Said About MK-677

The FDA has addressed MK-677 through enforcement actions rather than approval proceedings. Because the compound lacks any approved status, companies selling it for human consumption operate outside the legal framework for drugs and dietary supplements.

Warning Letters and Enforcement

The FDA has issued warning letters to multiple companies marketing selective androgen receptor modulators (SARMs) and growth hormone secretagogues, including MK-677, as dietary supplements. These letters cite violations of the Federal Food, Drug, and Cosmetic Act. The FDA's position is that MK-677 is a new drug under Section 201(p) of the Act because it is intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease [2].

In a 2017 advisory, the FDA stated: "Products marketed as dietary supplements that contain SARMs, including ostarine, andarine, and compounds such as ibutamoren, pose significant safety concerns. These products are not dietary supplements and are unapproved new drugs" [5].

DSHEA Does Not Protect MK-677

The Dietary Supplement Health and Education Act (DSHEA) of 1994 allows marketing of substances that were sold as dietary supplements before that date or that qualify as dietary ingredients. MK-677 was not marketed as a supplement before 1994 and is a synthetic pharmaceutical compound. It does not occur naturally in food. The FDA has made clear that DSHEA protections do not apply to MK-677. Any product containing ibutamoren sold without an approved NDA is considered an adulterated and misbranded product under federal law [5].

MK-677 Label Status

No FDA-approved label for MK-677 exists. This is a direct consequence of no NDA ever being filed. Every product currently sold as "MK-677" or "ibutamoren" is either a research chemical not intended for human use or an illegally marketed product.

What Research-Grade Labels Contain

Research chemical suppliers typically label MK-677 as "for research purposes only, not for human consumption." These labels are not FDA-reviewed. They provide a chemical name (2-amino-2-methyl-N-[1-(1-methylsulfonylspiro[indoline-3,4'-piperidine]-1'-yl)-1-oxo-3-(phenylmethoxy)propan-2-yl]propanamide), a molecular weight, and sometimes a certificate of analysis showing purity by HPLC. They contain no dosing information, no contraindications, no drug interaction warnings, and no adverse event reporting requirements [2].

Contrast With Approved GH Therapies

For comparison, FDA-approved growth hormone therapies such as somatropin carry extensive prescribing information that includes boxed warnings, dosing by indication and body weight, monitoring parameters, and post-marketing safety data compiled over decades. The somatropin prescribing information runs over 30 pages. MK-677 has none of this infrastructure.

Safety Profile From Available Data

Clinical trial data on MK-677 is limited to studies involving fewer than 200 total subjects across all published trials. No Phase III safety database exists. The available evidence identifies several consistent adverse signals.

Common Adverse Effects

Across published trials, the most frequently reported side effects of MK-677 at 25 mg/day include increased appetite (reported in approximately 40% of subjects), transient lower-extremity edema, muscle pain, and joint stiffness [1][4]. Weight gain of 2 to 3 kg over the first 8 weeks was typical and appeared to reflect both fluid retention and increased caloric intake.

Metabolic Concerns

The glucose signal is the most clinically significant safety finding. In the Nass et al. Trial, fasting glucose increased from a baseline mean of 5.1 mmol/L to 5.7 mmol/L in the MK-677 group, compared to no change in the placebo arm [4]. Two participants (6.1% of the treatment group) developed fasting glucose values exceeding 7.0 mmol/L, consistent with a new diabetes diagnosis. HbA1c data was not systematically reported.

A separate analysis by Copinschi et al. (1997) confirmed that MK-677 increases cortisol levels acutely after dosing, with a mean rise of approximately 36% above baseline in the first two hours, though levels normalized by 8 hours post-dose [6]. The long-term implications of repeated cortisol spikes remain unstudied.

The Endocrine Society's 2011 clinical practice guideline on GH therapy in adults does not mention MK-677 as a therapeutic option, reflecting the compound's lack of an approved evidence base [7]. Dr. Hau Liu, writing in the Annals of Internal Medicine, noted that GH-axis interventions in healthy older adults "have not demonstrated a favorable risk-benefit ratio for broad clinical use" [8].

International Regulatory Status

MK-677 holds no marketing authorization from any major regulatory agency worldwide.

EMA and Other Agencies

The European Medicines Agency (EMA) has no European Public Assessment Report (EPAR) for ibutamoren. No marketing authorization application has been submitted. The Australian Therapeutic Goods Administration (TGA) includes MK-677 on its list of substances subject to import restrictions. Japan's Pharmaceuticals and Medical Devices Agency (PMDA) has issued no approval [2].

WADA Prohibition

The World Anti-Doping Agency (WADA) added MK-677 to its Prohibited List under Section S2 (Peptide Hormones, Growth Factors, Related Substances, and Mimetics) in 2013. It is prohibited both in competition and out of competition. Multiple athletes have received sanctions after testing positive for ibutamoren metabolites [9].

What This Means for Patients Considering MK-677

The regulatory void surrounding MK-677 creates real risks for anyone obtaining and using the compound.

Quality and Purity Risks

Without cGMP manufacturing requirements, research-grade MK-677 products have no guaranteed purity, potency, or sterility. A 2017 analysis of SARMs and related compounds sold online found that only 52% of products contained the ingredient listed on the label, 39% contained an unapproved drug not listed on the label, and 9% contained no active compound at all [10]. While this study focused primarily on SARMs, MK-677 is distributed through the same supply channels.

FDA-Approved Alternatives Exist

Patients with documented growth hormone deficiency have FDA-approved options. Recombinant somatropin has marketing authorization for adult GH deficiency, and the oral GH secretagogue receptor agonist macimorelin (Macrilen) received FDA approval in 2017 as a diagnostic agent for adult GH deficiency [11]. Tesamorelin (Egrifta), a synthetic growth hormone-releasing hormone analog, holds FDA approval for HIV-associated lipodystrophy [12].

For patients interested in GH-axis modulation, these approved therapies carry established safety profiles, standardized manufacturing, and regulatory oversight that MK-677 cannot provide. Any off-label use of an approved GH therapy should occur under physician supervision with appropriate monitoring of IGF-1, fasting glucose, and HbA1c at minimum every 3 to 6 months.