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Comparison

Tesamorelin vs ipamorelin

Tesamorelin and ipamorelin both lead to growth hormone release, but they act on different receptors, they differ greatly in size, and their regulatory status and evidence base are very different[1,4,11].

By Tesamorelin.app editorial teamSources reviewed How we source

Tesamorelin compared with ipamorelin
AttributeTesamorelinIpamorelin
ClassGHRH analogue[1]Growth hormone secretagogue, ghrelin-receptor agonist[4,6]
ReceptorGHRH receptor (GHRHR), coupled to adenylyl cyclase[2]Ghrelin receptor (GHSR), coupled to G(q)[3]
Size44 amino acids + N-terminal hexenoyl group[1]5 residues (Aib-His-D-2-Nal-D-Phe-Lys-NH2)[4]
Molecular formulaC221H366N72O67S[7]C38H49N9O5[8]
Molecular weight5135.9 Da (free base, FDA label); 5136 g/mol (PubChem)[7]711.9 g/mol (PubChem)[8]
FDA statusApproved 2010 for one indication[9]No FDA-approved application found[10]
Compounding statusNot applicable (approved product)Listed by FDA in category 2 of bulk substances that may present significant safety risks (503B), added September 2023[11]
Human trials with published results11 in this database, including two phase 3 trialsHuman PK/PD in volunteers and a phase 2 trial in postoperative ileus[5,6]

Two receptors, two pathways

Tesamorelin binds the GHRH receptor with potency similar to the natural hormone[1]. That receptor activates adenylyl cyclase through G proteins[2]. Ipamorelin was described in 1998 as a selective GH secretagogue acting through a GHRP-like receptor[4]. That receptor is the ghrelin receptor (GHSR), which is coupled to G(q)[3]. The mechanism explorer shows where each acts.

In rat and swine studies, ipamorelin did not raise FSH, LH, prolactin or TSH. Unlike GHRP-6 and GHRP-2, it did not release ACTH or cortisol at levels significantly different from GHRH stimulation[4]. Those findings come from animal studies, not human trials.

Size of the human evidence base

Tesamorelin has two multicentre phase 3 trials behind its approval, plus several smaller randomized studies (see the trial explorer). The published human data on ipamorelin come from intravenous pharmacokinetic studies in healthy volunteers[5]. They also include a phase 2 trial in postoperative ileus after bowel surgery, which found no significant efficacy difference from placebo[6]. No human trial of ipamorelin on body composition was identified.

Regulatory difference

Tesamorelin is an approved prescription drug[9]. No FDA approval was found for ipamorelin[10]. FDA places ipamorelin acetate in category 2 of bulk drug substances for compounding that may present significant safety risks. FDA's listed concerns include immunogenicity and a reported serious adverse event with intravenous use[11].

References

  1. 1.EGRIFTA WR (tesamorelin) for injection, Prescribing Information. Revised 03/2025; DailyMed SPL version 2 (published 2026-08-03). DailyMed · accessed 2026-11-11
  2. 2.UniProtKB Q02643. Growth hormone-releasing hormone receptor (GHRHR), Homo sapiens. UniProt · accessed 2026-11-11
  3. 3.UniProtKB Q92847. Growth hormone secretagogue receptor type 1 (GHSR), Homo sapiens. UniProt · accessed 2026-11-11
  4. 4.Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139:552-61. PubMed · PMID 9849822 · doi:10.1530/eje.0.1390552 · accessed 2026-11-11
  5. 5.Gobburu JV, et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. 1999;16:1412-6. PubMed · PMID 10496658 · doi:10.1023/a:1018955126402 · accessed 2026-11-11
  6. 6.Beck DE, et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis. 2014;29:1527-34. PubMed · PMID 25331030 · doi:10.1007/s00384-014-2030-8 · accessed 2026-11-11
  7. 7.PubChem Compound Summary for CID 16137828, Tesamorelin. National Center for Biotechnology Information. PubChem · accessed 2026-11-11
  8. 8.PubChem Compound Summary for CID 9831659, Ipamorelin. National Center for Biotechnology Information. PubChem · accessed 2026-11-11
  9. 9.U.S. Food and Drug Administration. Approval letter, NDA 022505, EGRIFTA (tesamorelin for injection). November 10, 2010. FDA approval letter (PDF) · accessed 2026-11-11
  10. 10.openFDA Drugs@FDA API query for generic name "ipamorelin". The API returns "No matches found" (no approved application). api.fda.gov · accessed 2026-11-11
  11. 11.U.S. Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks (category 2 list; content current as of 04/22/2026). fda.gov · accessed 2026-11-11