Peptides Similar to Ibutamoren (MK-677)
Compare Ibutamoren (MK-677) with related peptides and alternatives
📌TL;DR
- •3 similar peptides identified
- •Sermorelin: Moderate - Both stimulate endogenous GH release, but through different receptor mechanisms (GHRH-R vs GHS-R1a)
- •Tesamorelin: Moderate - Both increase GH and IGF-1 levels, targeting age- and disease-related GH deficiency
Quick Comparison
| Peptide | Similarity | Key Differences |
|---|---|---|
| Ibutamoren (MK-677) (current) | - | - |
| Sermorelin | Moderate - Both stimulate endogenous GH release, but through different receptor mechanisms (GHRH-R vs GHS-R1a) | Sermorelin is a GHRH analog that acts through the GHRH receptor, while ibutamoren acts through the ghrelin receptor. Sermorelin is injectable while ibutamoren is orally active. Sermorelin was previously FDA-approved for GH deficiency diagnosis. |
| Tesamorelin | Moderate - Both increase GH and IGF-1 levels, targeting age- and disease-related GH deficiency | Tesamorelin is a GHRH analog (trans-3-hexenoic acid-GHRH) that is FDA-approved for HIV-associated lipodystrophy. It acts via the GHRH receptor rather than the ghrelin receptor. |
| Hexarelin | High - Both are growth hormone secretagogues that act on the ghrelin receptor (GHS-R1a) | Hexarelin is a synthetic hexapeptide GH secretagogue that requires injection, while ibutamoren is a non-peptide small molecule with oral bioavailability. Hexarelin shows tachyphylaxis with chronic use. |
SermorelinModerate - Both stimulate endogenous GH release, but through different receptor mechanisms (GHRH-R vs GHS-R1a)
Differences
Sermorelin is a GHRH analog that acts through the GHRH receptor, while ibutamoren acts through the ghrelin receptor. Sermorelin is injectable while ibutamoren is orally active. Sermorelin was previously FDA-approved for GH deficiency diagnosis.
Advantages
Sermorelin has regulatory precedent (was FDA-approved), does not significantly affect appetite or glucose metabolism, and has a cleaner safety profile
Disadvantages
Sermorelin requires subcutaneous injection, has a very short half-life (~10-20 minutes), and is less potent for GH stimulation than ibutamoren
TesamorelinModerate - Both increase GH and IGF-1 levels, targeting age- and disease-related GH deficiency
Differences
Tesamorelin is a GHRH analog (trans-3-hexenoic acid-GHRH) that is FDA-approved for HIV-associated lipodystrophy. It acts via the GHRH receptor rather than the ghrelin receptor.
Advantages
Tesamorelin is FDA-approved with established safety data, specifically reduces visceral adipose tissue, and does not significantly affect appetite or glucose metabolism
Disadvantages
Requires daily subcutaneous injection, approved only for a narrow indication (HIV lipodystrophy), more expensive as a prescription medication
HexarelinHigh - Both are growth hormone secretagogues that act on the ghrelin receptor (GHS-R1a)
Differences
Hexarelin is a synthetic hexapeptide GH secretagogue that requires injection, while ibutamoren is a non-peptide small molecule with oral bioavailability. Hexarelin shows tachyphylaxis with chronic use.
Advantages
Hexarelin has a more selective GH-releasing profile and may have cardioprotective properties independent of GH release
Disadvantages
Requires injection, shorter duration of action, demonstrates tachyphylaxis (loss of GH-stimulating effect with repeated dosing), never reached late-stage clinical development
Peptides Related to Ibutamoren (MK-677)#
Ibutamoren belongs to the growth hormone secretagogue class, compounds that stimulate endogenous GH release rather than directly replacing GH with exogenous administration. This class includes both peptide-based agents (GHRP-6, GHRP-2, hexarelin) and non-peptide agents (ibutamoren), as well as GHRH analogs (sermorelin, tesamorelin) that work through a complementary mechanism. The following comparisons highlight the key differences among these approaches to GH axis stimulation.
Sermorelin#
Sermorelin is a synthetic 29-amino-acid peptide analog of GHRH(1-29) that stimulates GH release through the GHRH receptor, a different mechanism from ibutamoren's ghrelin receptor agonism. Sermorelin was previously FDA-approved for diagnostic testing of GH deficiency (Geref) and was used clinically for GH stimulation before being voluntarily withdrawn from the market due to manufacturing issues rather than safety concerns.
Key differences: Sermorelin requires subcutaneous injection and has a very short half-life (~10-20 minutes), requiring multiple daily doses for sustained effect. It does not increase appetite or significantly affect glucose metabolism. The GHRH and ghrelin receptor pathways are synergistic, and their combined activation produces greater GH release than either alone.
Tesamorelin (Egrifta)#
Tesamorelin is a modified GHRH analog conjugated with trans-3-hexenoic acid for improved stability. It is the only currently FDA-approved GHRH analog, indicated specifically for reducing excess abdominal fat in HIV-infected patients with lipodystrophy (marketed as Egrifta).
Key differences: Tesamorelin has a proven safety record in its approved population and specifically reduces visceral adipose tissue, a distinct advantage over ibutamoren which did not significantly affect visceral fat in the Nass et al. trial. However, tesamorelin's approved indication is narrow and it requires daily subcutaneous injection.
Hexarelin#
Hexarelin (examorelin) is a synthetic hexapeptide GH secretagogue that, like ibutamoren, acts on the GHS-R1a receptor. It was one of the earliest peptide-based GH secretagogues studied clinically.
Key differences: Hexarelin requires parenteral administration (subcutaneous or intranasal), has a shorter duration of action, and demonstrates significant tachyphylaxis with chronic use, meaning its GH-stimulating effect diminishes over days to weeks of continuous administration. Ibutamoren does not appear to exhibit this tachyphylaxis to the same degree. Hexarelin may have GH-independent cardioprotective effects mediated through cardiac-specific scavenger receptors (CD36).
Summary Comparison#
| Feature | Ibutamoren | Sermorelin | Tesamorelin | Hexarelin |
|---|---|---|---|---|
| Chemical type | Small molecule | Peptide (29 aa) | Modified peptide | Peptide (6 aa) |
| Receptor target | GHS-R1a (ghrelin) | GHRH-R | GHRH-R | GHS-R1a (ghrelin) |
| Administration | Oral | SC injection | SC injection | SC/IN |
| Half-life | 4-6 h (functional 24 h) | ~10-20 min | ~26 min | ~20 min |
| FDA status | Never approved | Withdrawn (mfg) | Approved (HIV lipo) | Never approved |
| Appetite effect | Significant increase | Minimal | Minimal | Modest increase |
| Glucose effects | Adverse (insulin resistance) | Minimal | Minimal | Minimal |
| Tachyphylaxis | Limited | Possible | Possible | Significant |
Related Reading#
Frequently Asked Questions About Ibutamoren (MK-677)
Explore Further
Disclaimer: For educational purposes only. Not medical advice. Read full disclaimer