CJC-1295 + MK-677 (Ibutamoren) Stack: When to Pick One Over the Stack

Two receptors, two very different trial histories

CJC-1295 is a long-acting analogue of growth hormone-releasing hormone (GHRH). It acts on the pituitary like GHRH to raise the body's own growth hormone and, through GH, IGF-I, and it is given by subcutaneous injection [6][8]. The DAC form carries an extra maleimidopropionic acid-lysine unit at the C-terminal end that binds blood albumin, which lets it last much longer; its half-life is measured in days rather than minutes [1][9].

MK-677 is not a peptide. It is an oral small molecule that stimulates GH release through the ghrelin (growth hormone secretagogue) receptor; Merck first synthesized it in 1995 and discontinued development in 1999 [2]. A single oral dose is described as active for about 24 hours [2].

The two drugs act through different receptors, but no study has tested whether that difference makes combining them more effective than using either one alone [6][2].

What CJC-1295 has shown on its own

FDA identified only three published human studies of CJC-1295, all of the DAC form and all in healthy volunteers, and found no study of any form in people with a disease [1].

Teichman 2006 was a pair of randomized, double-blind, placebo-controlled ascending-dose trials lasting 28 and 49 days in healthy adults aged 21 to 61. It measured changes in GH and IGF-I, not improvement in a disease or health outcome [6]. After a single subcutaneous injection, mean plasma GH rose 2- to 10-fold for 6 days or more and mean IGF-I rose 1.5- to 3-fold for 9 to 11 days. The estimated half-life was 5.8 to 8.1 days, and after repeated doses IGF-I stayed above baseline for up to 28 days [6]. FDA counted 35 treated subjects and 7 on placebo in the first of the two trials [1][6]. No serious adverse reactions were reported [6].

Ionescu and Frohman 2006 gave healthy men aged 20 to 40 one injection of 60 or 90 micrograms/kg. A week later GH pulsatility was preserved, but trough GH was about 7.5-fold higher, mean GH 46% higher and IGF-I 45% higher, with no significant difference between the two doses [8].

Side effects in these studies, as FDA summarises them, were mainly injection-site reactions (about 70% in the first trial and all treated subjects in the second), headache (63% versus 14% on placebo), flushing, warmth and transient low blood pressure (about 30% of treated subjects in the first trial), transient diarrhea, and transient dizziness with low blood pressure in two subjects [1][6]. Most events were more common at 125 or 250 micrograms/kg [1].

The history behind that readout is less tidy. A phase 2 trial in HIV-associated lipodystrophy with 192 people enrolled was ended in 2006 after one participant died. FDA cites news reports that the person had chest discomfort two hours after an 11th weekly dose and that an ECG showed an acute heart attack, with undiagnosed coronary artery disease and plaque rupture the attending physician's most likely explanation. The data were never published, so a causal link is neither shown nor excluded [1]. FDA's compounding page still lists serious adverse events it identified with CJC-1295, including increased heart rate and a systemic vasodilatory reaction, and notes that available clinical data are limited [10].

What MK-677 has shown on its own

The MK-677 record is larger and longer. Trials consistently show rises in IGF-1, but the clinical findings are mixed: some measures improved, while other functional outcomes did not and important safety signals were reported [3][11][12][13][5].

Healthy older adults (Nass 2008): 65 people aged 60 to 81 took 25 mg daily or placebo, with outcomes at 12 months. Fat-free mass rose 1.1 kg versus a 0.5 kg fall on placebo, body weight rose 2.7 kg versus 0.8 kg, fasting glucose rose about 5 mg/dL (P=0.015) with lower insulin sensitivity, and strength and function did not improve [12]. The most frequent side effects were increased appetite, transient mild leg edema and muscle pain [12].

Hip fracture (Adunsky 2011): 123 patients aged 60 or older, 25 mg daily for 24 weeks. The trial was stopped early for a safety signal of congestive heart failure, which FDA's summary puts at 4 patients (6.5%) on MK-677 versus 1 (1.7%) on placebo. Systolic blood pressure rose 11.9 to 16.4 mmHg versus 2.3 to -2.3 mmHg on placebo, serious adverse events occurred in 24% versus 13%, and the authors concluded the drug has an unfavorable safety profile in this population [3][2]. Gait speed improved by a 0.7-score difference in the means, though several other functional performance measures did not improve [3].

A second hip-fracture trial (Bach 2004, 161 patients, 6 months) raised IGF-1 by 84% versus 17% on placebo with no significant functional benefit, and recorded more serious events (24% versus 18%), thrombosis in 4 versus 0 patients, and larger rises in glucose (+8.0 versus -1.6 mg/dL) and HbA1c (+0.7 versus +0.3 percentage points) [13][2].

Alzheimer's disease (Sevigny 2008, 563 patients, 12 months): IGF-1 rose 72.9%, but there was no effect on any progression measure. Drug-related adverse events were 35.5% versus 23.9%, blood glucose increases 15.4% versus 4.6% and HbA1c increases 11.1% versus 1.4% [5].

In 292 postmenopausal women with osteoporosis, MK-677 25 mg plus alendronate 10 mg raised femoral neck bone density 4.2% versus 2.5% with alendronate alone, with no extra gain at the spine, total hip or total body [11].

In 24 obese men given 25 mg daily for 8 weeks, IGF-1 rose about 40% and fat-free mass increased, but total and visceral fat did not change and an oral glucose tolerance test showed impaired glucose handling at 2 and 8 weeks [14].

Doses used in the trials

MK-677 trials used fixed oral doses of 2 to 50 mg per day, 25 mg once daily in most adult trials, for up to two years [2]. CJC-1295 human doses were single subcutaneous injections of about 30 to 250 micrograms/kg, or two to three doses given weekly or every two weeks [1][6]. Neither has an approved dose [1][2].

What actually decides one over the other

The evidence supports comparing route, duration of hormone changes, and documented harms; it does not support choosing the stack as more effective than either drug alone [6][2][3].

How it is taken. CJC-1295 is a subcutaneous injection; MK-677 is taken by mouth [6][2].

Duration of action. The estimated half-life of CJC-1295 DAC was 5.8 to 8.1 days, with IGF-1 still above baseline up to 28 days after repeated dosing [6]; a single MK-677 dose is active for about 24 hours [2].

How much is known. CJC-1295 has three published studies in healthy volunteers measuring GH and IGF-1, the Teichman trials lasting 28 and 49 days [1][6][8]. MK-677 has trials of 24 to 563 people lasting up to two years, with functional and clinical endpoints reported in several studies [12][13][5][14].

Glucose. MK-677 raised fasting glucose and lowered insulin sensitivity in healthy older adults, and raised glucose and HbA1c in the hip-fracture and Alzheimer's trials [12][13][5], and FDA lists hyperglycemia among the serious safety concerns from the trials [2]. The CJC-1295 adverse events FDA summarises are injection-site reactions, headache, flushing, transient low blood pressure, diarrhea and dizziness [1][6].

Heart and fluid. The MK-677 hip-fracture trial was stopped for a congestive heart failure signal [3], and FDA places ibutamoren mesylate in its category 2 list of bulk substances that may present significant safety risks 'due to the potential for congestive heart failure in certain patients' [10]. For CJC-1295, FDA lists increased heart rate and a systemic vasodilatory reaction among serious adverse events, and a phase 2 trial ended after a participant died [1][10].

Appetite. Increased appetite was reported in healthy older adults, and FDA's review identified it as the most common drug-related event in a 6-month trial of LUM-201, an oral growth hormone secretagogue, in 68 children with growth hormone deficiency [2][16][12].

Sport. Both are named in WADA's Prohibited List under S2.2.4, prohibited at all times in and out of competition [7][17].

Regulatory status

Neither is FDA-approved for any use [1][2]. In December 2024 FDA found no approved product containing any form of CJC-1295 in the 12 countries it searched and none authorized by the European Medicines Agency [1].

MK-677 is on FDA's category 2 list of bulk substances that may present significant safety risks when compounded, which is the list where FDA names safety problems and says its category 1 no-action policy does not apply. Ibutamoren mesylate was added December 29, 2022 for outsourcing facilities and September 29, 2023 for state-licensed pharmacies and physicians, and was still on both lists in 2026 [10][18][19]. On October 29, 2024 the Pharmacy Compounding Advisory Committee voted 1 yes, 13 no against adding it to the pharmacy bulks list [20].

CJC-1295 sits elsewhere: it was in category 2 but now appears in the 'nominated but withdrawn' table because the nominators withdrew, and it is in none of the three categories, so the category 1 policy does not cover it either [10][18][19]. FDA's safety concerns remain posted [10]. In December 2024 the advisory committee voted 0 yes, 13 no on CJC-1295 free base, 1 yes, 12 no on the acetate, and 0 yes, 13 no on each of the three DAC forms [21]. Neither substance is among the six peptides in HHS's October 2026 draft enforcement-discretion policy [22][23].

FDA's December 12, 2025 warning letter to a supplement seller states that ibutamoren is excluded from the dietary supplement definition, and that products marketed with drug claims are unapproved new drugs [4]. In September 2025 FDA warned that a children's growth product contained undeclared ibutamoren, and listed the risks it associates with the ingredient: increased appetite, water retention, fatigue, muscle pain, changes in glucose metabolism and insulin sensitivity, and a possible increased potential for congestive heart failure in certain individuals [24]. Compounded drugs are not FDA-approved; FDA does not review their safety, effectiveness or quality before marketing [25].