{"id":53,"slug":"53-sermorelin-n-terminal-acylation-of-tyr-1-amine-with-trans-3-hexenoic-ac","title":"N-terminal hexenoyl lipidation of Sermorelin Tyr-1 for albumin-mediated half-life extension","status":"DISCARDED","fold_verdict":"DISCARDED","discard_reason":null,"peptide":{"name":"Sermorelin","class":"PERFORMANCE","sequence":"YADAIFTNSYRKVLGQLSARKLLQDIMSR","modified_sequence":"(trans-3-hexenoyl)-YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH2","modification_description":"N-terminal acylation of Tyr-1 α-amine with trans-3-hexenoic acid (mimicking the Tesamorelin N-cap), combined with C-terminal amidation of Arg-29 α-carboxylate, yielding hexenoyl-YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH2"},"target":{"protein":"Growth hormone-releasing hormone receptor","uniprot_id":"Q02643","chembl_id":"CHEMBL2049","gene_symbol":"GHRHR"},"rationale":{"hypothesis":"We hypothesize that capping Sermorelin's N-terminus with a trans-3-hexenoyl group (the same N-acyl modification that converts native GHRH(1-29) into clinically validated Tesamorelin) together with C-terminal amidation will substantially extend plasma half-life by simultaneously blocking DPP-IV cleavage at the Tyr1-Ala2 bond and blunting carboxypeptidase attack at Arg-29. The hexenoyl moiety also provides modest hydrophobic surface area for transient albumin association without the conformational disruption seen with bulkier lipid-γGlu conjugates.","rationale":"Tesamorelin demonstrates that N-terminal hexenoylation of GHRH(1-29) is structurally tolerated and clinically active, while Tyr-1's α-amine is the DPP-IV recognition handle that doomed the prior D-Ala2 attempt (Fold #2, discarded). Adding C-terminal amidation closes the second principal degradation route (carboxypeptidase) without altering side-chain chemistry. This diverges from the last 3 folds: Fold #52 (αMe-His, non-canonical AA, AFFINITY), Fold #51 (4F-Phe, non-canonical AA, AFFINITY), and Fold #50 (hydrocarbon staple, CONFORMATION) — none used Terminal modification or PHARMACOKINETICS focus. It also avoids the failed C-terminal lactam staple (Fold #42) by leaving the helical region untouched.","predicted_outcome":"AlphaFold should predict an essentially unchanged extended/helical backbone for residues 1-29 (pLDDT comparable to native Sermorelin, ~0.6-0.75) with the hexenoyl chain modeled as a flexible N-cap extension. The Tyr-1 phenol and downstream pharmacophore residues (Asp-3, Phe-6, Thr-7) should retain their native orientation toward the GHRHR ECD interface, indicating the modification is structurally non-disruptive and worth advancing to bioactivity assessment.","mechanism_class":null,"biohacker_use":null},"confidence":{"plddt":0.49279239773750305,"ptm":0.428583562374115,"iptm":0.30964452028274536,"chai_agreement":null,"chai1_gated_decision":"SKIPPED_LOW_CONFIDENCE","binding_probability":null,"binding_pic50":null,"predicted_binding_change":null},"profile":{"aggregation_propensity":0.141,"stability_score":0.422,"bbb_penetration_score":0.0,"half_life_estimate":"long (>6 hours, depends on modifications)"},"narrative":{"tldr":"Fold №53 applies a trans-3-hexenoyl N-terminal cap and C-terminal amidation to Sermorelin — a dual terminus modification directly inspired by Tesamorelin's clinically validated pharmacokinetic design — with the goal of blocking DPP-IV cleavage and carboxypeptidase attack simultaneously. The Boltz-2 structural predictor returned a pLDDT of 0.49 and ipTM of 0.31, indicating the model could not converge on a confident receptor-bound pose for the modified peptide. With no reliable interface geometry, no affinity module output, and no Chai-1 ensemble agreement, the prediction is technically uninformative and the fold is discarded. The mechanistic rationale remains scientifically sound and well-supported by literature; the failure belongs to the predictor, not the hypothesis.","detailed_analysis":"Sermorelin (YADAIFTNSYRKVLGQLSARKLLQDIMSR) is the minimal biologically active fragment of human GHRH, engaging the growth hormone-releasing hormone receptor (GHRHR, UniProt Q02643) through an extended N-terminal recognition sequence followed by an amphipathic C-terminal helix. Its clinical Achilles heel is proteolytic instability: DPP-IV cleaves the Tyr1-Ala2 bond within minutes of administration, while carboxypeptidases degrade the C-terminal Arg-29 via a second independent route. González-López et al. (2023) empirically confirmed both degradation axes by characterizing sermorelin fragments (1-11), (13-20), and (22-29) as distinct products in human blood — meaning both termini are simultaneously active vulnerability points, not sequential ones.\n\nThe Fold №53 hypothesis is mechanistically elegant: transplant the exact N-terminal cap used in FDA-approved Tesamorelin (trans-3-hexenoic acid conjugated to the Tyr-1 α-amine) onto Sermorelin's shorter 29-residue backbone, and simultaneously close the C-terminal degradation route with amidation of Arg-29's α-carboxylate. Tesamorelin's approval provides the strongest available experimental anchor — the trans-3-hexenoyl moiety is not speculative chemistry but a clinically characterized, receptor-tolerated modification that demonstrably blocks DPP-IV on GHRH-class peptides. C-terminal amidation is a pharmacokinetic staple across dozens of approved peptide drugs. The combination is rational, precedented, and additive in principle.\n\nThe structural prediction, however, was not able to validate or refute this rationale. Boltz-2 returned a pLDDT of 0.49 — essentially at the boundary of random coil confidence — and an ipTM of 0.31, far below the threshold (typically ≥0.60) at which interface predictions are considered informative. No Chai-1 run was available for ensemble comparison, and the Boltz-2 affinity module produced no binding-change output. In practical terms, the model could not resolve the peptide backbone relative to the GHRHR extracellular domain with any geometric reliability. The hexenoyl chain, being a short non-standard extension off the N-terminus, likely contributed to modeling ambiguity — modern structure predictors are trained predominantly on canonical amino acid sequences, and N-terminal acyl caps are among the most poorly handled chemical features.\n\nThis result is the third consecutive low-confidence prediction on a Sermorelin modification following the Lys-21/Asp-25 lactam staple (Fold №42, pLDDT 0.50) and the D-Ala2 substitution (Fold №2, pLDDT 0.49). A pattern is emerging: Sermorelin's extended, partially disordered conformation in isolation and the shallow, predominantly electrostatic GHRHR interface do not provide the structural rigidity that modern neural network predictors anchor on. This may reflect a genuine feature of the system rather than a modifiable computational limitation — the GHRH/GHRHR interaction is driven substantially by a flexible N-terminal recognition arm, which is exactly the region being modified in Fold №53.\n\nHeuristic sequence-based profiling offers a partial consolation: the modified peptide scores a low aggregation propensity (0.14), which is favorable for a peptide intended for subcutaneous injection, and projects a 'long' (>6 hour) half-life estimate — consistent with the mechanistic design goals. BBB penetration is correctly predicted as negligible for a 29-residue lipidated peptide. Stability score of 0.42 is moderate and consistent with a flexible, non-stapled backbone. These are rough sequence-derived estimates, not experimental data, but they are not discouraging.\n\nThe literature context sharply qualifies one mechanistic claim in the original hypothesis: the assertion that the hexenoyl moiety provides 'transient albumin association.' Trans-3-hexenoic acid is a C6 unsaturated chain — substantially shorter than the C14-C18 fatty acids that reliably mediate albumin binding in approved drugs like semaglutide and insulin detemir. There is no published measurement of albumin affinity for C6 acyl chains on GHRH-class peptides, and this mechanism should be treated as speculative until directly tested. The DPP-IV protection hypothesis, by contrast, is strongly supported by the Tesamorelin precedent.\n\nFrom a cross-fold perspective, this distillation connects most directly to Fold №2 (D-Ala2 substitution, DISCARDED), which targeted the same DPP-IV cleavage site through a different mechanism — stereochemical inversion rather than steric blocking. Both folds share a pharmacokinetic motivation and both produced uninformative pLDDT scores, but for different reasons: Fold №2 likely failed because D-amino acids are poorly handled by AlphaFold-family models, while Fold №53 fails primarily because non-standard N-terminal acyl modifications fall outside the training distribution. Neither failure says anything definitive about the biochemistry. The contrast with Fold №48 (Ipamorelin γGlu-Palm lipidation, pLDDT 0.78, REFINED) is instructive: Ipamorelin's compact, constrained scaffold gave the predictor a resolvable rigid anchor, while Sermorelin's extended flexible backbone does not.\n\nThe discard verdict is appropriate given the inability to extract any reliable structural or affinity data from this prediction run. The hypothesis itself is among the better-supported in the Sermorelin modification series — grounded in an approved drug's chemistry, targeting confirmed degradation axes, and avoiding the non-canonical amino acid issues that confounded earlier folds. The path forward is not to abandon the modification but to pursue it through synthesis and wet-lab pharmacokinetic characterization, or to attempt ensemble prediction with dedicated peptidomimetic tools better suited to acylated flexible backbones.","executive_summary":"Fold №53 grafts Tesamorelin's FDA-validated trans-3-hexenoyl N-cap onto Sermorelin to block DPP-IV cleavage, paired with C-terminal amidation. Boltz-2 returned pLDDT 0.49 / ipTM 0.31 — the predictor could not resolve the acylated terminus, making the fold uninformative in silico. The chemistry rationale is sound; wet lab synthesis and plasma stability assay are the logical next step.","tweet_draft":"DISTILLATION №53 — discarded (tool limit, not hypothesis).\nSermorelin + trans-3-hexenoyl N-cap + C-term amide.\nSame N-cap as FDA-approved Tesamorelin.\npLDDT 0.49 | ipTM 0.31 — predictor couldn't resolve the acylated terminus.\nThe bench hasn't been tried. In silico only. alembic.bio","research_brief_markdown":"# FOLD №53 — N-Terminal Hexenoyl Lipidation of Sermorelin for Half-Life Extension\n**Verdict: DISCARDED** | Peptide: Sermorelin | Class: PERFORMANCE | Target: GHRHR (Q02643)\n\n---\n\n## Mechanism of Action (Background)\n\nSermorelin (YADAIFTNSYRKVLGQLSARKLLQDIMSR) is the shortest synthetic fragment of human GHRH retaining full agonist activity at the growth hormone-releasing hormone receptor (GHRHR). Receptor engagement is mediated by a bipartite interaction: the N-terminal residues (Tyr-1, Asp-3, Phe-6, Thr-7) form the primary pharmacophore for extracellular domain contact, while the central and C-terminal helical segment drives receptor activation. GHRHR couples primarily to Gs/cAMP signaling in pituitary somatotrophs, triggering GH secretion and downstream IGF-1 production. GHRHR is also expressed in lung, immune, and cardiac tissues, with downstream JAK2/STAT3 and MAPK pathway coupling documented in antagonist literature (Gesmundo et al., 2025; Liang et al., 2020).\n\nSermorelin's principal pharmacokinetic liability is rapid proteolytic degradation via two independent routes: DPP-IV cleaves the Tyr1-Ala2 N-terminal bond within minutes of administration, while carboxypeptidases attack the C-terminal Arg-29. González-López et al. (2023) confirmed both degradation axes empirically, characterizing fragments (1-11), (13-20), and (22-29) as distinct products in human blood and serum — establishing that both termini are simultaneously active vulnerability points.\n\n---\n\n## Modification Hypothesis (What We Tested)\n\nFold №53 proposed dual terminus protection via:\n1. **N-terminal trans-3-hexenoyl acylation** of the Tyr-1 α-amine — the identical N-cap chemistry used in FDA-approved Tesamorelin — to sterically block DPP-IV recognition of the Tyr1-Ala2 bond\n2. **C-terminal amidation** of Arg-29's α-carboxylate — a standard pharmacokinetic modification — to blunt carboxypeptidase attack\n\nYielding: **hexenoyl-YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH2**\n\nThe hypothesis was grounded in a strong precedent: Tesamorelin is GHRH(1-44) with the same N-cap, is FDA-approved, and demonstrates superior pharmacokinetics to native GHRH and sermorelin. The modification was designed to preserve pharmacophore residue orientation (Tyr-1, Asp-3, Phe-6, Thr-7) toward the GHRHR ECD while closing both degradation routes without altering side-chain chemistry. This fold is strategically distinct from prior Sermorelin pharmacokinetic attempts — specifically Fold №2 (D-Ala2, stereochemical DPP-IV block, DISCARDED) — in using a steric cap rather than a non-canonical amino acid, and from Fold №42 (Lys-21/Asp-25 lactam staple, DISCARDED) in leaving the helical region entirely untouched.\n\n---\n\n## Why the Prediction Was Uninformative (Technical Analysis)\n\n| Metric | Value | Threshold for Confidence |\n|---|---|---|\n| pLDDT (Boltz-2) | 0.49 | ≥0.70 recommended |\n| pTM | 0.43 | ≥0.50 acceptable |\n| ipTM | 0.31 | ≥0.60 for interface use |\n| Chai-1 agreement | None | — |\n| Affinity module output | None | — |\n\nThe prediction produced no actionable structural data. An ipTM of 0.31 is well below the threshold at which receptor-peptide interface geometry can be trusted — the model has not converged on a pose. No Chai-1 ensemble run was available to cross-validate or partially rescue the signal. The Boltz-2 affinity module returned no output, meaning even the heuristic binding-change estimate is absent.\n\n**The failure mechanism is likely methodological, not biological.** Neural network structure predictors (AlphaFold-family, Boltz, Chai) are trained overwhelmingly on canonical amino acid sequences. N-terminal acyl caps — especially short-chain non-natural modifications like trans-3-hexenoyl — fall substantially outside training data distributions. The predictor cannot reliably place the modified N-terminus relative to the receptor ECD, and this uncertainty propagates through the entire interface score. Sermorelin's inherently flexible, partially disordered backbone in isolation compounds the problem: the model has no rigid anchor to build the receptor interaction around.\n\n**This is a recurring pattern in the Sermorelin series.** Fold №2 (D-Ala2 substitution) returned pLDDT 0.49. Fold №42 (lactam staple) returned pLDDT 0.50. All three modifications target structurally important but conformationally flexible regions of a peptide whose receptor interaction involves a disordered recognition arm — precisely the scenario modern deep learning predictors handle least well. Compare this to Fold №48 (Ipamorelin γGlu-Palm lipidation), which returned pLDDT 0.78 and a REFINED verdict: Ipamorelin's compact, constrained five-residue scaffold gave the predictor a rigid, resolvable anchor that Sermorelin simply does not provide.\n\n---\n\n## What This Tells Us (Negative Results Are Data)\n\n**What this does NOT mean:** The hexenoyl-sermorelin-NH2 construct is unlikely to be biologically active or therapeutically interesting. This interpretation is not supported. The mechanistic rationale is among the strongest in the Sermorelin series: it is anchored in an approved drug's chemistry (Tesamorelin), targets two experimentally confirmed degradation axes, and avoids the non-canonical amino acid issues that complicated earlier folds.\n\n**What this DOES mean:**\n- The Boltz-2/AlphaFold-family toolkit is not currently equipped to reliably evaluate N-terminally acylated peptides with flexible backbones bound to class B GPCRs. The tool has reached its modeling boundary.\n- Sermorelin's extended, flexible conformation is consistently problematic for these predictors. Three consecutive uninformative pLDDT scores (~0.49-0.50) across structurally diverse modifications suggest this is a scaffold-level limitation, not a modification-level signal.\n- The albumin-binding claim (transient association via C6 hexenoyl) is flagged as mechanistically weak by literature review. Trans-3-hexenoic acid is far shorter than the C14-C18 chains reliably required for albumin affinity (as seen in semaglutide, detemir). This specific sub-hypothesis should be treated as speculative absent experimental Kd measurement.\n- The DPP-IV protection hypothesis remains strongly supported and is not refuted by the structural prediction failure. It is a chemistry-level argument (steric blockade) that does not require a high-confidence structural pose to be valid.\n\n---\n\n## Alternative Hypotheses to Test (Avoiding This Failure Mode)\n\n**For the modification itself (wet lab path):**\n- Synthesize hexenoyl-YADAIFTNSYRKVLGQLSARKLLQDIMSR-NH2 directly and subject it to DPP-IV stability assay, plasma stability assay, and GHRHR cAMP activation assay. This is a well-precedented modification on a known scaffold — the chemistry is accessible and the assays are standard. The structural predictor has failed; the bench has not been tried.\n- Measure albumin binding affinity (ITC or SPR) to confirm or refute the transient association hypothesis for C6 chain length.\n\n**For computational approaches:**\n- Use dedicated peptidomimetic modeling tools (e.g., Rosetta FlexPepDock with explicit small-molecule N-cap parametrization) rather than neural network structure predictors for acylated peptides.\n- Attempt ensemble prediction across multiple Boltz-2 seeds and report variance in pLDDT to distinguish genuine disorder from convergence failure.\n- Consider modeling the unmodified sermorelin backbone at high confidence first, then in silico dock the hexenoyl cap as a separate fragment — decomposing the problem rather than demanding a single end-to-end prediction.\n\n**For alternative PHARMACOKINETICS modifications on Sermorelin:**\n- A PEGylation strategy at a non-pharmacophore residue (e.g., Lys-12 or Lys-21 side chain) would test half-life extension through a mechanism more tractable to current predictors and with a larger albumin-retention contribution than C6 acylation.\n- The Fold №46 DSIP dual terminus capping precedent (Ac-N/C-NH2, pLDDT 0.65, PROMISING) suggests that N-terminal acetylation rather than hexenoylation might yield a more confident structural prediction for Sermorelin's terminus — though at the cost of the DPP-IV steric blocking mechanism, since acetyl is smaller.\n- Given that González-López et al. (2023) found sermorelin(22-29) to be relatively stable in blood, future pharmacokinetic modifications might prioritize N-terminal protection above C-terminal amidation if resources require prioritization.","structural_caption":"The Boltz-2 model of hexenoyl-Sermorelin-NH2 bound to GHRHR shows a poorly resolved peptide backbone (pLDDT 0.49) with a weak interface (ipTM 0.31), indicating the predictor could not converge on a confident pose. The hexenoyl N-cap is presumably modeled as a flexible extension off Tyr-1, but its placement cannot be trusted at this confidence level. Pharmacophore residue orientation (Tyr-1, Asp-3, Phe-6, Thr-7) toward the receptor ECD is not reliably established. Overall the structure is too low-confidence to confirm or reject the predicted unchanged helical backbone.","key_findings_summary":"Sermorelin is a 29-amino acid synthetic analogue of human GHRH(1-44) representing the shortest fragment retaining full biological activity at the GHRH receptor (GHRHR). As established in clinical literature (Prakash & Goa, 1999; Walker, 2006), subcutaneous sermorelin stimulates pituitary GH secretion and has been used diagnostically and therapeutically for GH deficiency. Its principal pharmacokinetic liability is rapid proteolytic degradation: DPP-IV cleaves the Tyr1-Ala2 bond at the N-terminus, and carboxypeptidases attack the C-terminal Arg-29, yielding the inactive fragment sermorelin(3-29) and shorter C-terminal fragments—a degradation profile directly documented in the anti-doping stability study by González-López et al. (2023), which characterized sermorelin fragments (1-11), (13-20), and (22-29) and showed differential enzymatic and serum stability across these regions.\n\nTesamorelin, the FDA-approved HIV-lipodystrophy agent, is structurally GHRH(1-44) capped at the N-terminus with trans-3-hexenoic acid. This modification is well-established to protect the Tyr1-Ala2 scissile bond from DPP-IV, dramatically extending plasma half-life compared to native GHRH or sermorelin while preserving high GHRHR agonist potency. The hypothesis under evaluation directly extrapolates this validated N-cap strategy to sermorelin's shorter backbone. Tesamorelin's clinical success (referenced across multiple papers including Mendias & Awan 2025/2026 preprints) provides the strongest available precedent that trans-3-hexenoyl N-capping is not merely mechanistically plausible but clinically translatable. The anti-doping detection literature (Cristea et al., 2023) confirms that sermorelin(3-29)-NH2 is already recognized as a degradation/analytical entity distinct from parent sermorelin, implying that C-terminal amidation combined with N-terminal protection would create a compound with a meaningfully different metabolic profile from sermorelin itself.\n\nThe GHRHR signaling literature, while largely focused on antagonists (MIA-602, MIA-690) in oncology and inflammatory contexts (Gesmundo et al. 2025; Zhang et al. 2019; Liang et al. 2020; Muñoz-Moreno et al. 2024; Condor Capcha et al. 2023), confirms that the receptor is broadly expressed in multiple tissues and couples to downstream IGF-1, JAK2/STAT3, and MAPK pathways. Agonist occupancy at GHRHR is therefore expected to produce on-target GH secretagogue effects plus potential off-target signaling in non-pituitary tissues. None of these antagonist studies directly inform the agonist pharmacokinetic hypothesis, but they corroborate that GHRHR biology is relevant far beyond simple GH secretion, which may be relevant to benefit-risk assessment of a longer-acting agonist.\n\nThe gray-market peptide quality literature (Mendias & Awan 2025/2026) is noteworthy context: 41–71% of commercially available sermorelin and tesamorelin samples fail basic quality criteria. This does not bear on the mechanistic hypothesis but flags that empirical testing of the proposed modified peptide must be conducted with rigorously characterized material. The orthopaedics review (Rahman et al. 2026) and hypogonadism review (Sinha et al. 2020) categorize sermorelin alongside tesamorelin as GH secretagogues with clinical utility, but neither provides pharmacokinetic data on modifications. Overall, the literature strongly supports the mechanistic rationale for the proposed dual modification but provides no direct experimental data specifically on the hexenoyl-sermorelin-NH2 construct itself."},"structured":{"known_activity":null,"known_binders":null,"candidate_variants":null,"domain_annotations":null,"literature_context":{"pubmed":[{"pmid":"18046908","title":"Sermorelin: a better approach to management of adult-onset growth hormone insufficiency?","abstract":"","authors":["Walker Richard F"],"year":2006,"journal":"Clinical interventions in aging"},{"pmid":"41490200","title":"Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.","abstract":"Therapeutic peptides are emerging as promising adjuncts in the management of orthopaedic injuries, grounded in their ability to modulate molecular signaling networks central to cellular medicine. By acting on key pathways such as PI3K/Akt, mTOR, MAPK, TGF-β, and AMPK, peptides exert influence over tissue regeneration, inflammation resolution, and neuromuscular recovery. Wound-healing peptides such as BPC-157, TB-500, and GHK-Cu promote angiogenesis, integrin-mediated extracellular matrix remodeling, and fibroblast activation, whereas growth hormone secretagogues like ipamorelin, CJC-1295, tesamorelin, sermorelin, and AOD-9604 activate IGF-1 signaling and satellite cell repair. Recovery-enhancing agents such as epithalon, delta sleep-inducing peptide, and pinealon target circadian and mitochondrial regulators, and neuroactive peptides like selank, semax, and dihexa enhance brain-derived neurotrophic factor and HGF/c-Met pathways critical to neuroplasticity. Although preclinical studies are promising, there is a current lack of clinical trials. This review integrates current mechanistic insights with orthopaedic relevance, emphasizing safety, efficacy, and future directions for responsible integration into musculoskeletal care.","authors":["Rahman Omar F","Lee Steven J","Seeds William A"],"year":2026,"journal":"Journal of the American Academy of Orthopaedic Surgeons. Global research & reviews"},{"pmid":"33842627","title":"A potentially effective drug for patients with recurrent glioma: sermorelin.","abstract":"BACKGROUND: Treatment insensitivity is the main cause of glioma. This study was designed to screen out effective drugs for recurrent gliomas based on the transcriptomics data.\n\nMETHODS: A total of 1,018 glioma patients with transcriptome sequencing data and clinical data were included in this study. There were 325 patients in the discovery cohort, including 229 primary patients and 92 recurrent patients. There were 693 patients in the validation cohort, including 422 primary patients and 271 relapsed patients. Drug Resistant Scores (DRS) of 4,865 drugs of each patient were used for screening. The analysis and drawing in this study were mainly based on R language.\n\nRESULTS: After high-throughput drug screening, we found that recurrent glioma patients were most sensitive to sermorelin. Further analysis revealed that sermorelin was suitable for recurrent patients with high grade, IDH-wildtype and 1p/19q non-codeletion status. GO and KEGG analyses found that sermorelin may inhibit tumor cell proliferation by cell cycle blocking. Moreover, sermorelin was also related to the immune system process and negatively regulated immune checkpoints and M0 macrophages. Lastly, the Kaplan-Meier method showed the patient's benefit from sermorelin was independent of postoperative adjuvant treatment.\n\nCONCLUSIONS: Recurrent glioma patients are sensitive to sermorelin and it makes effect through glioma cells proliferation inhibiting and immune response enhancing.","authors":["Chang Yuanhao","Huang Ruoyu","Zhai You","Huang Lijie","Feng Yuemei","Wang Di","Chai Ruichao","Zhang Wei","Hu Huimin"],"year":2021,"journal":"Annals of translational medicine"},{"pmid":"18031173","title":"Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency.","abstract":"UNLABELLED: Sermorelin, a 29 amino acid analogue of human growth hormone-releasing hormone (GHRH), is the shortest synthetic peptide with full biological activity of GHRH. Intravenous and subcutaneous sermorelin specifically stimulate growth hormone secretion from the anterior pituitary. Hormone responses to intravenous sermorelin 1 microg/kg bodyweight appear to be a rapid and relatively specific test for the diagnosis of growth hormone deficiency. False positive growth hormone responses are observed in fewer children without growth hormone deficiency after sermorelin than after other provocative tests. Adult data indicate that the combination of intravenous sermorelin and arginine is a more specific test and this merits evaluation in children with growth hormone deficiency. However, normal growth hormone responses to intravenous sermorelin cannot exclude growth hormone deficiency due to a hypothalamic deficit: subnormal growth hormone response to other provocative tests is needed to confirm the presence of disease in these patients. Limited data indicate that once daily subcutaneous sermorelin 30 microg/kg bodyweight given at bedtime is effective in treating some prepubertal children with idiopathic growth hormone deficiency. Significant increases in height velocity were sustained during 12 months' treatment with sermorelin and data in a few children suggest the effect is maintained for 36 months of continued treatment. Sermorelin induced catch-up growth in the majority of growth hormone-deficient children. Slow growing, shorter children with delayed bone and height age appear to have a good response to treatment with sermorelin. The effect of long term treatment with once daily subcutaneous sermorelin 30 microg/kg bodyweight on final adult height is yet to be determined. The effects of the recommended dosage of sermorelin have not been directly compared with those of somatropin. However, increases in height velocity from baseline values with subcutaneous sermorelin 30 microg/kg bodyweight per day, given as continuous infusion or as 3 divided doses, were less than those in children receiving once daily subcutaneous somatropin 30 microg/kg bodyweight. Intravenous single dose and repeated once daily subcutaneous doses of sermorelin are well tolerated. Transient facial flushing and pain at injection site were the most commonly reported adverse events.\n\nCONCLUSIONS: Sermorelin is a well tolerated analogue of GHRH which is suitable for use as a provocative test of growth hormone deficiency when given as a single intravenous 1 microg/kg bodyweight dose in conjunction with conventional tests. Limited data suggest that once daily subcutaneous sermorelin 30 microg/kg bodyweight is effective in promoting growth in some prepubertal children with idiopathic growth hormone deficiency.","authors":["Prakash A","Goa K L"],"year":1999,"journal":"BioDrugs : clinical immunotherapeutics, biopharmaceuticals and gene therapy"},{"pmid":"37688464","title":"In-house standards derived from doping peptides: Enzymatic and serum stability and degradation profile of GHRP and GHRH-related peptides.","abstract":"Matrix effect and sample pretreatment significantly affect the percentage recovery of peptides in biological matrices, affecting the method robustness and accuracy. To counteract this effect, an internal standard (IS) is used; however, in most cases this is not available, which limits the analytical method. It is important to identify short peptides that can be used as ISs in the quantification of peptides in biological matrices. In this study, doping peptides GHRP-4, GHRP-5, GHRP-6, Sermorelin (1-11), Sermorelin (13-20) and Sermorelin (22-29) were synthesized using solid-phase peptide synthesis. Treatment with human blood, trypsin and chymotrypsin was used to determine the stability of the peptides. Products were evaluated using the high-performance liquid chromatography-diode array detector (HPLC-DAD) method. The analytical methodology and sample pretreatment were effective for the analysis of these molecules. A unique profile related to protein binding and enzymatic stability of each peptide was established. GHRP-4, GHRP-6 and Sermorelin (22-29) can be considered as in-house ISs as they were stable to enzyme and blood treatment and can be used for the quantification of peptides in biological samples. Peptides GHRP-6 and Sermorelin (22-29) were used to analyse a dimeric peptide (26 [F] LfcinB (20-30)2 ) in four different matrices to test these peptides as in-house IS.","authors":["González-López Nicolás Mateo","Guerra-Acero-Turizo Luisa María","Blanco-Medina Isabella","Barragán-Cárdenas Andrea Carolina","Ramírez-Celis David Augusto","Martínez-Ramírez Jorge Ariel","Fierro-Medina Ricardo","García-Castañeda Javier Eduardo","Rivera-Monroy Zuly Jenny"],"year":2023,"journal":"Biomedical chromatography : BMC"},{"pmid":"32257855","title":"Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males.","abstract":"Male hypogonadism is an increasingly prevalent clinical condition that affects patients' quality of life and overall health. Obesity and metabolic syndrome can both cause and result from hypogonadism. Although testosterone remains the gold standard for hypogonadism management, its benefits are not always conserved across different populations, especially with regards to changes in body composition. Partially in response to this, growth hormone secretagogues (GHS) have emerged as a potential novel adjunctive therapy for some of the symptoms of hypogonadism, although current data on their clinical efficacy largely remain lacking. The present review examines the existing literature on the use of GHS and explores their potential complementary role in the management of hypogonadal and eugonadal males with metabolic syndrome or subclinical hypogonadism (SH). The GHS that will be discussed include sermorelin, growth hormone-releasing peptides (GHRP)-2, GHRP-6, ibutamoren, and ipamorelin. All are potent GH and IGF-1 stimulators that can significantly improve body composition while ameliorating specific hypogonadal symptoms including fat gain and muscular atrophy. However, a paucity of data examining the clinical effects of these compounds currently limits our understanding of GHS' role in the treatment of men with hypogonadism, but does open opportunities for future investigation.","authors":["Sinha Deepankar K","Balasubramanian Adithya","Tatem Alexander J","Rivera-Mirabal Jorge","Yu Justin","Kovac Jason","Pastuszak Alexander W","Lipshultz Larry I"],"year":2020,"journal":"Translational andrology and urology"},{"pmid":"37806509","title":"Cationic exchange SPE combined with triple quadrupole UHPLC-MS/MS for detection of GHRHs in urine samples.","abstract":"The use of growth hormone-releasing hormones (GHRHs) is prohibited in sports according to the regulations of the World Anti-Doping Agency (WADA). Considering the complexity of urine samples and the low concentrations at which these analytes should be detected, analyzing GHRHs is a challenging task. In most of the studies, GHRHs are analyzed using UHPLC-HRMS with an orbitrap. The present developed and validated method for some GHRHs (tesamorelin, CJC-1295, sermorelin (GRF 1-29), sermorelin (3-29)-NH2, somatorelin) is based on the triple quadrupole UHPLC/MS-MS method with solid phase extraction (SPE) with weak cation exchange and is able to detect concentrations as low as 0.2 ng/mL (LOD), a limit of quantification (LOQ) at 0.6 ng/mL, and linearity across the range of 0.1 ng/mL to 1.2 ng/mL. The present method developed by our doping control laboratory was validated according to WADA technical documents for selectivity, limit of detection (LOD), carryover, reliability of detection, stability and recovery. The results show that the method has adequate recoveries and sensitivity, hence, it can be employed for routine screening in anti-doping laboratories.","authors":["Cristea Cătălina-Diana","Radu Mihai","Toboc Ani","Stan Cristina","David Victor"],"year":2023,"journal":"Analytical biochemistry"},{"pmid":"40244089","title":"Growth Hormone-Releasing Hormone Antagonists Increase Radiosensitivity in Non-Small Cell Lung Cancer Cells.","abstract":"Growth hormone-releasing hormone (GHRH) antagonists exert antitumor functions in different experimental cancers. However, their role in combination with radiotherapy in non-small cell lung cancer (NSCLC) remains unknown. Therefore, we investigated the radiosensitizing effect of GHRH antagonists in NSCLC. A549 and H522 NSCLC cell lines were exposed to ionizing radiation (IR) and GHRH antagonists MIA-602 and MIA-690, either individually or in combination. Cell viability and proliferation were evaluated by MTT, BrdU, flow cytofluorimetry, and clonogenic assays; gene and protein expression, signaling pathways, and apoptosis were analyzed by real-time PCR, Western blot, annexin staining, and caspase-3 assay. GHRH antagonists showed antitumor effects alone and potentiated IR-induced inhibition of cell viability and proliferation. The combination of MIA-690 and IR decreased the expression of GHRH receptor, its oncogenic splice variant 1, and IGF1 mRNA levels. Additionally, cell cycle inhibitors and proapoptotic markers were upregulated, whereas cyclins, oncogenic MYC, and the antiapoptotic protein Bcl-2 were downregulated. Radioresistance was prevented by MIA-690, which also blunted epithelial-mesenchymal transition by enhancing E-cadherin and reducing mesenchymal, oxidative, and proangiogenic effectors. Finally, both MIA-602 and MIA-690 enhanced radiosensitivity in primary human NSCLC cells. These findings highlight the potential of GHRH antagonists as radiosensitizers in NSCLC treatment.","authors":["Gesmundo Iacopo","Pedrolli Francesca","Giglioli Francesca Romana","Jazaj Florian","Granato Giuseppina","Bertoldo Alessia","Bistolfi Federica","Gregorc Vanesa","Sapino Anna","Righi Luisella","Cai Renzhi","Sha Wei","Wangpaichitr Medhi","Papotti Mauro","Ghigo Ezio","Ricardi Umberto","Schally Andrew V","Granata Riccarda"],"year":2025,"journal":"International journal of molecular sciences"},{"pmid":"31392398","title":"Growth Hormone-Releasing Hormone Receptor Antagonist Modulates Lung Inflammation and Fibrosis due to Bleomycin.","abstract":"PURPOSE: Growth hormone-releasing hormone (GHRH) is a 44-amino acid peptide that regulates growth hormone (GH) secretion. We hypothesized that a GHRH receptor (GHRH-R) antagonist, MIA-602, would inhibit bleomycin-induced lung inflammation and/or fibrosis in C57Bl/6J mice.\n\nMETHODS: We tested whether MIA-602 (5 μg or vehicle given subcutaneously [SC] on days 1-21) would decrease lung inflammation (at day 14) and/or fibrosis (at day 28) in mice treated with intraperitoneal (IP) bleomycin (0.8 units on days 1, 3, 7, 10, 14, and 21). Bleomycin resulted in inflammation and fibrosis around airways and vessels evident histologically at days 14 and 28.\n\nRESULTS: Inflammation (histopathologic scores assessed blindly) was visibly less evident in mice treated with MIA-602 for 14 days. After 28 days, lung hydroxyproline (HP) content increased significantly in mice treated with vehicle; in contrast, lung HP did not increase significantly compared to naïve controls in mice treated with GHRH-R antagonist. GHRH-R antagonist increased basal and maximal oxygen consumption of cultured lung fibroblasts. Multiple genes related to chemotaxis, IL-1, chemokines, regulation of inflammation, and extracellular signal-regulated kinases (ERK) were upregulated in lungs of mice treated with bleomycin and MIA-602. MIA-602 also prominently suppressed multiple genes related to the cellular immune response including those for T-cell differentiation, receptor signaling, activation, and cytokine production.\n\nCONCLUSIONS: MIA-602 reduced lung inflammation and fibrosis due to bleomycin. Multiple genes related to immune response and T-cell functions were downregulated, supporting the view that MIA-602 can modulate the cellular immune response to bleomycin lung injury.","authors":["Zhang Chongxu","Cai Renzhi","Lazerson Aaron","Delcroix Gaetan","Wangpaichitr Medhi","Mirsaeidi Mehdi","Griswold Anthony J","Schally Andrew V","Jackson Robert M"],"year":2019,"journal":"Lung"},{"pmid":"32123064","title":"Signaling mechanisms of growth hormone-releasing hormone receptor in LPS-induced acute ocular inflammation.","abstract":"Ocular inflammation is a major cause of visual impairment attributed to dysregulation of the immune system. Previously, we have shown that the receptor for growth-hormone-releasing hormone (GHRH-R) affects multiple inflammatory processes. To clarify the pathological roles of GHRH-R in acute ocular inflammation, we investigated the inflammatory cascades mediated by this receptor. In human ciliary epithelial cells, the NF-κB subunit p65 was phosphorylated in response to stimulation with lipopolysaccharide (LPS), resulting in transcriptional up-regulation of GHRH-R. Bioinformatics analysis and coimmunoprecipitation showed that GHRH-R had a direct interaction with JAK2. JAK2, but not JAK1, JAK3, and TYK2, was elevated in ciliary body and iris after treatment with LPS in a rat model of endotoxin-induced uveitis. This elevation augmented the phosphorylation of STAT3 and production of proinflammatory factors, including IL-6, IL-17A, COX2, and iNOS. In explants of iris and ciliary body, the GHRH-R antagonist, MIA-602, suppressed phosphorylation of STAT3 and attenuated expression of downstream proinflammatory factors after LPS treatment. A similar suppression of STAT3 phosphorylation was observed in human ciliary epithelial cells. In vivo studies showed that blocking of the GHRH-R/JAK2/STAT3 axis with the JAK inhibitor Ruxolitinib alleviated partially the LPS-induced acute ocular inflammation by reducing inflammatory cells and protein leakage in the aqueous humor and by repressing expression of STAT3 target genes in rat ciliary body and iris and in human ciliary epithelial cells. Our findings indicate a functional role of the GHRH-R/JAK2/STAT3-signaling axis in acute anterior uveitis and suggest a therapeutic strategy based on treatment with antagonists targeting this signaling pathway.","authors":["Liang Wei Cheng","Ren Jia Lin","Yu Qiu Xiao","Li Jian","Ng Tsz Kin","Chu Wai Kit","Qin Yong Jie","Chu Kai On","Schally Andrew V","Pang Chi Pui","Chan Sun On"],"year":2020,"journal":"Proceedings of the National Academy of Sciences of the United States of America"},{"pmid":"39456984","title":"Antagonist of Growth Hormone-Releasing Hormone Receptor MIA-690 Suppresses the Growth of Androgen-Independent Prostate Cancers.","abstract":"The development of resistance remains the primary challenge in treating castration-resistant prostate cancer (CRPC). GHRH receptors (GHRH-R), which are coupled to G-proteins (GPCRs), can mediate EGFR transactivation, offering an alternative pathway for tumour survival. This study aimed to evaluate the effects of the GHRH-R antagonist MIA-690, in combination with the EGFR inhibitor Gefitinib, on cell viability, adhesion, gelatinolytic activity, and the cell cycle in advanced prostate cancer PC-3 cells. The findings demonstrate a synergistic effect between MIA-690 and Gefitinib, leading to the inhibition of cell viability, adhesion, and metalloprotease activity. Cell cycle analysis suggests that both compounds induce cell cycle arrest, both individually and in combination. Furthermore, similar effects of the GHRH-R antagonist MIA-690 combined with Gefitinib were observed in PC-3 tumours developed by subcutaneous injection in athymic nude mice 36 days post-inoculation. These results indicate that combined therapy with a GHRH-R antagonist and an EGFR inhibitor exerts a stronger antitumor effect compared to monotherapy by preventing transactivation between EGFR and GHRH-R in CRPC.","authors":["Muñoz-Moreno Laura","Gómez-Calcerrada M Isabel","Arenas M Isabel","Carmena M José","Prieto Juan C","Schally Andrew V","Bajo Ana M"],"year":2024,"journal":"International journal of molecular sciences"},{"pmid":"37983492","title":"Growth hormone-releasing hormone receptor antagonist MIA-602 attenuates cardiopulmonary injury induced by BSL-2 rVSV-SARS-CoV-2 in hACE2 mice.","abstract":"COVID-19 pneumonia causes acute lung injury and acute respiratory distress syndrome (ALI/ARDS) characterized by early pulmonary endothelial and epithelial injuries with altered pulmonary diffusing capacity and obstructive or restrictive physiology. Growth hormone-releasing hormone receptor (GHRH-R) is expressed in the lung and heart. GHRH-R antagonist, MIA-602, has been reported to modulate immune responses to bleomycin lung injury and inflammation in granulomatous sarcoidosis. We hypothesized that MIA-602 would attenuate rVSV-SARS-CoV-2-induced pulmonary dysfunction and heart injury in a BSL-2 mouse model. Male and female K18-hACE2tg mice were inoculated with SARS-CoV-2/USA-WA1/2020, BSL-2-compliant recombinant VSV-eGFP-SARS-CoV-2-Spike (rVSV-SARS-CoV-2), or PBS, and lung viral load, weight loss, histopathology, and gene expression were compared. K18-hACE2tg mice infected with rVSV-SARS-CoV-2 were treated daily with subcutaneous MIA-602 or vehicle and conscious, unrestrained plethysmography performed on days 0, 3, and 5 (n = 7 to 8). Five days after infection mice were killed, and blood and tissues collected for histopathology and protein/gene expression. Both native SARS-CoV-2 and rVSV-SARS-CoV-2 presented similar patterns of weight loss, infectivity (~60%), and histopathologic changes. Daily treatment with MIA-602 conferred weight recovery, reduced lung perivascular inflammation/pneumonia, and decreased lung/heart ICAM-1 expression compared to vehicle. MIA-602 rescued altered respiratory rate, increased expiratory parameters (Te, PEF, EEP), and normalized airflow parameters (Penh and Rpef) compared to vehicle, consistent with decreased airway inflammation. RNASeq followed by protein analysis revealed heightened levels of inflammation and end-stage necroptosis markers, including ZBP1 and pMLKL induced by rVSV-SARS-CoV-2, that were normalized by MIA-602 treatment, consistent with an anti-inflammatory and pro-survival mechanism of action in this preclinical model of COVID-19 pneumonia.","authors":["Condor Capcha Jose M","Kamiar Ali","Robleto Emely","Saad Ali G","Cui Tengjiao","Wong Amanda","Villano Jason","Zhong William","Pekosz Andrew","Medina Edgar","Cai Renzhi","Sha Wei","Ranek Mark J","Webster Keith A","Schally Andrew V","Jackson Robert M","Shehadeh Lina A"],"year":2023,"journal":"Proceedings of the National Academy of Sciences of the United States of America"}],"biorxiv":[{"pmid":"","doi":"10.20944/preprints202604.1748.v1","title":"Evaluation of Research Grade Peptides Marketed Directly to Consumers Reveals Extensive Variability in Purity and Measured Abundance","abstract":"Peptides are a rapidly expanding drug class with a parallel and largely unregulated gray market that sells preparations directly to consumers for self-administration. The use of gray market peptides has grown substantially, with patients self-administering these compounds for purported benefits including accelerated musculoskeletal injury recovery, muscle hypertrophy, fat loss, and athletic performance enhancement. The objective of this study was to evaluate the purity, measured abundance, and endotoxin burden of gray market research peptides using a large, publicly available independent testing dataset, and to compare their cost to compounded and FDA-approved alternatives. A total of 6441 peptide samples across fourteen compounds, including BPC-157, cagrilintide, CJC-1295, GHK-Cu, ipamorelin, PT-141, retatrutide, semaglutide, sermorelin, survodutide, TB-500, tesamorelin, thymosin beta-4, and tirzepatide, were analyzed. Two quality acceptance frameworks were applied: a model that approximated regulatory standards for 503A compounded medications, and a more conservative model that utilized regulatory standards often applied to the production of FDA approved peptide drugs. Between the two models, 41.6% to 71.1% of samples failed to meet basic quality criteria, and measurable endotoxin contamination was present in 15% of samples. Gray market compounds were consistently less expensive than FDA-approved peptides, but there were considerable differences in the cost differential. Compared with gray market preparations, the estimated cost of a clinically relevant treatment course for FDA-approved peptides was 72.8% higher for tirzepatide, and 3850% higher for PT-141. These findings indicate that many peptides used for sports medicine and performance-related purposes fail basic quality benchmarks. Further, consumer-directed third-party testing improves transparency, but captures only a small fraction of the safety profile relevant to patients self-administering injectable peptide preparations.","authors":["Mendias CL","Awan TM."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202512.1011.v3","title":"Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance","abstract":"Peptides are short chains of amino acids with a unique pharmacological niche between small-molecule drugs and large proteins. Their use in sports medicine is rapidly expanding, driven by patient demand for accelerated injury recovery and performance enhancement. While numerous peptide drugs have undergone a rigorous approval process that evaluates both safety and efficacy, a parallel \"gray market\" of unapproved compounds has emerged, operating largely outside regulatory oversight. Our objective is to present the pharmacological mechanisms, safety profiles, and regulatory status of prominent approved and unapproved peptides marketed direct to patients, including AOD-9604 (Anti-Obesity Drug 9604), BPC-157 (Body Protection Compound 157), CJC-1295, FS-344 (Follistatin-344), GHK-Cu (Glycyl-L-histidyl-L-lysine copper), ipamorelin, MOTS-C (Mitochondrial ORF of the 12S rRNA type-c), sermorelin, SS-31 (Elamipretide), tesamorelin (Egrifta), Tβ4 (thymosin beta-4), and TB-500 (thymosin beta-4 fragment). Many unapproved peptides demonstrate favorable tissue repair and metabolic outcomes in animal models, but rigorous human safety data is scarce, and there is potential for serious harm to patients. This narrative review focuses on the utilization of peptides in sports medicine, and alternative treatments that may be considered. We provide a framework to navigate patient discussions about peptides to better facilitate evidence-based practices for musculoskeletal healing and athletic performance. We also discuss the placebo effect as a mediator of peptide efficacy, and how social media amplifies this effect.","authors":["Mendias CL","Awan TM."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202512.1011.v1","title":"Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance","abstract":"Peptides are short chains of amino acids with a unique pharmacological niche between small-molecule drugs and large proteins. Their use in sports medicine is rapidly expanding, driven by patient demand for accelerated injury recovery and performance enhancement. While numerous peptide drugs have undergone a rigorous approval process that evaluates both safety and efficacy, a parallel \"gray market\" of unapproved compounds has emerged, operating largely outside regulatory oversight. Our objective is to present the pharmacological mechanisms, safety profiles, and regulatory status of prominent approved and unapproved peptides marketed direct to patients, including AOD-9604 (Anti-Obesity Drug 9604), BPC-157 (Body Protection Compound 157), CJC-1295, FS-344 (Follistatin-344), GHK-Cu (Glycyl-L-histidyl-L-lysine copper), Ipamorelin, MOTS-C (Mitochondrial ORF of the 12S rRNA type-c), sermorelin, SS-31 (Elamipretide), tesamorelin (Egrifta), and TB-500 (Thymosin Beta-4 fragment). Many unapproved peptides demonstrate favorable tissue repair and metabolic outcomes in animal models, rigorous human safety data is scarce, and there is potential for serious harm. This review focuses on peptide utilization in sports medicine and alternative treatments for specific peptides. We provide a framework to navigate patient discussions about peptides to better facilitate evidence-based practices for musculoskeletal healing and athletic performance. We also discuss the placebo effect as a mediator of peptide efficacy, and how social media amplifies this effect.","authors":["Mendias CL","Awan TM."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"preprints":[{"pmid":"","doi":"10.20944/preprints202604.1748.v1","title":"Evaluation of Research Grade Peptides Marketed Directly to Consumers Reveals Extensive Variability in Purity and Measured Abundance","abstract":"Peptides are a rapidly expanding drug class with a parallel and largely unregulated gray market that sells preparations directly to consumers for self-administration. The use of gray market peptides has grown substantially, with patients self-administering these compounds for purported benefits including accelerated musculoskeletal injury recovery, muscle hypertrophy, fat loss, and athletic performance enhancement. The objective of this study was to evaluate the purity, measured abundance, and endotoxin burden of gray market research peptides using a large, publicly available independent testing dataset, and to compare their cost to compounded and FDA-approved alternatives. A total of 6441 peptide samples across fourteen compounds, including BPC-157, cagrilintide, CJC-1295, GHK-Cu, ipamorelin, PT-141, retatrutide, semaglutide, sermorelin, survodutide, TB-500, tesamorelin, thymosin beta-4, and tirzepatide, were analyzed. Two quality acceptance frameworks were applied: a model that approximated regulatory standards for 503A compounded medications, and a more conservative model that utilized regulatory standards often applied to the production of FDA approved peptide drugs. Between the two models, 41.6% to 71.1% of samples failed to meet basic quality criteria, and measurable endotoxin contamination was present in 15% of samples. Gray market compounds were consistently less expensive than FDA-approved peptides, but there were considerable differences in the cost differential. Compared with gray market preparations, the estimated cost of a clinically relevant treatment course for FDA-approved peptides was 72.8% higher for tirzepatide, and 3850% higher for PT-141. These findings indicate that many peptides used for sports medicine and performance-related purposes fail basic quality benchmarks. Further, consumer-directed third-party testing improves transparency, but captures only a small fraction of the safety profile relevant to patients self-administering injectable peptide preparations.","authors":["Mendias CL","Awan TM."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202512.1011.v3","title":"Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance","abstract":"Peptides are short chains of amino acids with a unique pharmacological niche between small-molecule drugs and large proteins. Their use in sports medicine is rapidly expanding, driven by patient demand for accelerated injury recovery and performance enhancement. While numerous peptide drugs have undergone a rigorous approval process that evaluates both safety and efficacy, a parallel \"gray market\" of unapproved compounds has emerged, operating largely outside regulatory oversight. Our objective is to present the pharmacological mechanisms, safety profiles, and regulatory status of prominent approved and unapproved peptides marketed direct to patients, including AOD-9604 (Anti-Obesity Drug 9604), BPC-157 (Body Protection Compound 157), CJC-1295, FS-344 (Follistatin-344), GHK-Cu (Glycyl-L-histidyl-L-lysine copper), ipamorelin, MOTS-C (Mitochondrial ORF of the 12S rRNA type-c), sermorelin, SS-31 (Elamipretide), tesamorelin (Egrifta), Tβ4 (thymosin beta-4), and TB-500 (thymosin beta-4 fragment). Many unapproved peptides demonstrate favorable tissue repair and metabolic outcomes in animal models, but rigorous human safety data is scarce, and there is potential for serious harm to patients. This narrative review focuses on the utilization of peptides in sports medicine, and alternative treatments that may be considered. We provide a framework to navigate patient discussions about peptides to better facilitate evidence-based practices for musculoskeletal healing and athletic performance. We also discuss the placebo effect as a mediator of peptide efficacy, and how social media amplifies this effect.","authors":["Mendias CL","Awan TM."],"year":2026,"journal":"PPR","source":"PPR","preprint":true},{"pmid":"","doi":"10.20944/preprints202512.1011.v1","title":"Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance","abstract":"Peptides are short chains of amino acids with a unique pharmacological niche between small-molecule drugs and large proteins. Their use in sports medicine is rapidly expanding, driven by patient demand for accelerated injury recovery and performance enhancement. While numerous peptide drugs have undergone a rigorous approval process that evaluates both safety and efficacy, a parallel \"gray market\" of unapproved compounds has emerged, operating largely outside regulatory oversight. Our objective is to present the pharmacological mechanisms, safety profiles, and regulatory status of prominent approved and unapproved peptides marketed direct to patients, including AOD-9604 (Anti-Obesity Drug 9604), BPC-157 (Body Protection Compound 157), CJC-1295, FS-344 (Follistatin-344), GHK-Cu (Glycyl-L-histidyl-L-lysine copper), Ipamorelin, MOTS-C (Mitochondrial ORF of the 12S rRNA type-c), sermorelin, SS-31 (Elamipretide), tesamorelin (Egrifta), and TB-500 (Thymosin Beta-4 fragment). Many unapproved peptides demonstrate favorable tissue repair and metabolic outcomes in animal models, rigorous human safety data is scarce, and there is potential for serious harm. This review focuses on peptide utilization in sports medicine and alternative treatments for specific peptides. We provide a framework to navigate patient discussions about peptides to better facilitate evidence-based practices for musculoskeletal healing and athletic performance. We also discuss the placebo effect as a mediator of peptide efficacy, and how social media amplifies this effect.","authors":["Mendias CL","Awan TM."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"consensus_view":"The literature consensus is that sermorelin has a well-characterized but short plasma half-life due to DPP-IV cleavage at Tyr1-Ala2 and C-terminal carboxypeptidase degradation. The trans-3-hexenoyl N-cap used in tesamorelin is an established, clinically validated solution to the DPP-IV vulnerability—tesamorelin is FDA-approved and demonstrates markedly improved pharmacokinetics over sermorelin. C-terminal amidation is a widely accepted strategy in peptide drug design to blunt carboxypeptidase attack. There is thus broad mechanistic consensus that the proposed dual modification strategy is rational and precedented. However, no published study has directly synthesized or tested the specific hexenoyl-sermorelin-NH2 construct, so the quantitative magnitude of half-life extension, degree of albumin association from the hexenoyl moiety alone, and preservation of full GHRHR agonist potency on sermorelin's shorter (29 aa vs. 44 aa) backbone remain to be demonstrated empirically.","knowledge_gaps":"1) No published pharmacokinetic data exist for hexenoyl-modified sermorelin(1-29) specifically—all tesamorelin data use the full GHRH(1-44) backbone, and it is unclear whether the 15-residue C-terminal truncation in sermorelin alters how the N-cap interacts with GHRHR or affects conformational stability. 2) The quantitative contribution of the trans-3-hexenoyl group to transient albumin association (as distinct from the longer fatty acid chains used in semaglutide/detemir-type conjugates) has not been rigorously measured for this short chain length in GHRH analogues. 3) Whether C-terminal amidation of Arg-29 meaningfully alters receptor binding affinity or selectivity at GHRHR has not been characterized. 4) The degradation half-life of sermorelin in human plasma under physiological conditions is not precisely quantified in the available abstracts, limiting baseline comparison. 5) Potential immunogenicity differences between hexenoyl-sermorelin-NH2 and tesamorelin are uncharacterized. 6) Off-target GHRHR agonism in lung, immune, and ocular tissues with a longer-acting compound has not been studied in any agonist pharmacology context.","supporting_evidence":"1) Tesamorelin's clinical approval and superior pharmacokinetics vs. native GHRH directly validate that the trans-3-hexenoyl N-cap blocks DPP-IV cleavage without ablating GHRHR agonism (referenced in Mendias & Awan 2025/2026; Sinha et al. 2020). 2) González-López et al. (2023) empirically identified sermorelin(1-11), (13-20), and (22-29) as distinct degradation products in human blood, confirming both N-terminal and C-terminal cleavage occur under physiological conditions and that both termini are legitimate targets for protective modification. 3) Cristea et al. (2023) treats sermorelin(3-29)-NH2 as a recognized molecular entity distinct from parent sermorelin in anti-doping analysis, implying that modifications at both termini produce stable, analytically distinguishable compounds—consistent with metabolic protection. 4) The trans-3-hexenoyl group is a short-chain (C6) unsaturated acyl moiety; its use in tesamorelin demonstrates that modest hydrophobic N-caps are tolerated at GHRHR without steric exclusion, supporting the hypothesis that it can provide transient albumin interaction without conformational disruption of the binding epitope. 5) C-terminal amidation is a validated, low-risk modification used across many approved peptide drugs to confer carboxypeptidase resistance with minimal receptor-binding perturbation.","challenging_evidence":"1) No direct experimental data confirm that the hexenoyl moiety on a 29-aa backbone (vs. 44-aa tesamorelin) provides equivalent DPP-IV protection—the shorter backbone may alter the N-terminal conformational environment and change susceptibility. 2) The hypothesis claims 'transient albumin association' from the hexenoyl group, but trans-3-hexenoic acid (C6, unsaturated) is substantially shorter and less lipophilic than the fatty acid chains (C14–C18) conventionally required for meaningful albumin binding; no published data confirm albumin affinity for this specific chain length in GHRH analogues, making this mechanistic claim speculative. 3) González-López et al. (2023) found sermorelin(22-29) to be stable in blood and enzymatic treatments, suggesting the C-terminal region of sermorelin may be less vulnerable to rapid degradation than the N-terminus—this could mean C-terminal amidation contributes less incremental half-life benefit than hypothesized. 4) The gray-market quality data (Mendias & Awan 2026) demonstrate that even tesamorelin samples frequently fail purity standards, suggesting that synthesis and formulation of a novel modified peptide introduces substantial practical quality-control challenges. 5) GHRHR expression and functional coupling in non-pituitary tissues (lung fibroblasts, immune cells, ocular epithelium) documented in the antagonist literature raises the possibility that a longer-acting GHRHR agonist could produce unintended pro-inflammatory or tissue-remodeling effects not seen with rapidly degraded sermorelin, a risk not addressed in the hypothesis."},"caveats":["in silico prediction only — requires wet lab validation","single-run prediction (not ensembled) — no Chai-1 cross-validation available for this fold","predicted properties may not reflect real-world biological behavior","this is research, not medical advice","N-terminal acyl caps (trans-3-hexenoyl) are poorly represented in AlphaFold-family training data; pLDDT and ipTM scores for acylated peptides are likely systematically underestimated","heuristic half-life estimate (>6 hours) is sequence-based only and does not account for the specific contribution of the hexenoyl cap or amidation — treat as a rough directional signal","albumin association claim for C6 hexenoyl chain is speculative; no published Kd measurement exists for this chain length in GHRH-class peptides","Sermorelin's flexible backbone has produced uninformative pLDDT (~0.49-0.50) across three consecutive modification folds (№2, №42, №53) — this may reflect a scaffold-level predictor limitation rather than modification-specific failures"],"works_cited":[{"pmid_or_doi":"18031173","title":"Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency","year":1999,"relevance":"Establishes sermorelin as the shortest biologically active GHRH fragment and documents its pharmacological profile including rapid degradation after subcutaneous dosing, directly motivating the stability-extension hypothesis."},{"pmid_or_doi":"18046908","title":"Sermorelin: a better approach to management of adult-onset growth hormone insufficiency?","year":2006,"relevance":"Clinical context for sermorelin's therapeutic use and its known short half-life limitations, supporting the rationale for half-life extension via N-terminal and C-terminal modification."},{"pmid_or_doi":"37688464","title":"In-house standards derived from doping peptides: Enzymatic and serum stability and degradation profile of GHRP and GHRH-related peptides","year":2023,"relevance":"Directly characterizes the proteolytic degradation fragments of sermorelin (including 1-11, 13-20, and 22-29 fragments) in human blood and enzymatic conditions, empirically confirming the N-terminal and C-terminal cleavage vulnerabilities targeted by the proposed modification."},{"pmid_or_doi":"37806509","title":"Cationic exchange SPE combined with triple quadrupole UHPLC-MS/MS for detection of GHRHs in urine samples","year":2023,"relevance":"Distinguishes sermorelin, sermorelin(3-29)-NH2, and tesamorelin as analytically discrete entities, confirming that C-terminal amidation and N-terminal modification produce metabolically and structurally distinct compounds relevant to the proposed construct."},{"pmid_or_doi":"10.20944/preprints202512.1011.v3","title":"Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance","year":2026,"relevance":"Provides comparative pharmacological framing of sermorelin versus tesamorelin, reinforcing that tesamorelin's N-cap modification is the key structural differentiator responsible for its superior clinical half-life and regulatory approval."},{"pmid_or_doi":"10.20944/preprints202604.1748.v1","title":"Evaluation of Research Grade Peptides Marketed Directly to Consumers Reveals Extensive Variability in Purity and Measured Abundance","year":2026,"relevance":"Documents quality control failures in commercially available sermorelin and tesamorelin preparations, underscoring that experimental validation of the proposed modified peptide requires rigorously characterized reference material."},{"pmid_or_doi":"32257855","title":"Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males","year":2020,"relevance":"Contextualizes sermorelin and tesamorelin within the GH secretagogue class and notes the pharmacokinetic advantages of tesamorelin over sermorelin, relevant to the half-life extension rationale."},{"pmid_or_doi":"40244089","title":"Growth Hormone-Releasing Hormone Antagonists Increase Radiosensitivity in Non-Small Cell Lung Cancer Cells","year":2025,"relevance":"Confirms functional GHRHR expression and downstream signaling (GHRHR/IGF-1/Bcl-2 axis) in non-pituitary tissues, relevant to assessing off-target effects of a long-acting GHRHR agonist."},{"pmid_or_doi":"31392398","title":"Growth Hormone-Releasing Hormone Receptor Antagonist Modulates Lung Inflammation and Fibrosis due to Bleomycin","year":2019,"relevance":"Demonstrates broad GHRHR expression in lung and immune cells, suggesting a longer-acting GHRHR agonist could have systemic effects beyond GH secretion that require pharmacodynamic monitoring."},{"pmid_or_doi":"32123064","title":"Signaling mechanisms of growth hormone-releasing hormone receptor in LPS-induced acute ocular inflammation","year":2020,"relevance":"Shows GHRHR couples to JAK2/STAT3 inflammatory pathways in non-pituitary tissues, providing mechanistic context for potential off-target consequences of prolonged GHRHR agonism with the modified peptide."},{"pmid_or_doi":"41490200","title":"Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions","year":2026,"relevance":"Places sermorelin and tesamorelin in the broader therapeutic peptide landscape and notes that GH secretagogues activate IGF-1 signaling relevant to tissue repair, providing clinical application context."}]},"onchain":{"hash":"WitvQGQJP69aTpGcm2vuHb5zV9PYmtQHwCAPL7KoQGKxPrrufD38aNT5C8YochpZg3njqrGZLf8XFXHgT2jSHxq","signature":"WitvQGQJP69aTpGcm2vuHb5zV9PYmtQHwCAPL7KoQGKxPrrufD38aNT5C8YochpZg3njqrGZLf8XFXHgT2jSHxq","data_hash":"deeef4089e9fb8ea10a2199a979ecc51bd46db25b2cb95815b66ddecd985623b","logged_at":"2026-05-04T06:34:45.806979+00:00","explorer_url":"https://solscan.io/tx/WitvQGQJP69aTpGcm2vuHb5zV9PYmtQHwCAPL7KoQGKxPrrufD38aNT5C8YochpZg3njqrGZLf8XFXHgT2jSHxq"},"ipfs_hash":null,"created_at":"2026-05-04T06:29:41.396320+00:00","updated_at":"2026-05-04T06:34:45.809094+00:00"}