{"id":29,"slug":"29-tesamorelin-ala-2-methyl-alanine-aib-2-aminoisobutyric-acid-substitution","title":"Tesamorelin Ala-2 → α-methyl-Ala for DPP-IV resistance and helix nucleation","status":"DISCARDED","fold_verdict":"DISCARDED","discard_reason":null,"peptide":{"name":"Tesamorelin","class":"PERFORMANCE","sequence":"YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL","modified_sequence":"Y-Aib-DAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL","modification_description":"Ala-2 → α-methyl-alanine (Aib / 2-aminoisobutyric acid) substitution at position 2, retaining the native trans-3-hexenoyl group on Tyr-1"},"target":{"protein":"Growth hormone-releasing hormone receptor","uniprot_id":"Q02643","chembl_id":"CHEMBL2049","gene_symbol":"GHRHR"},"rationale":{"hypothesis":"Replacing Ala-2 of Tesamorelin with the Cα,α-disubstituted residue Aib will extend plasma half-life beyond what the trans-3-hexenoyl Tyr-1 cap already provides, by sterically blocking residual DPP-IV-like cleavage at the Tyr1-Ala2 scissile bond and by nucleating the N-terminal α-helix that docks into the GHRHR ECD/TM interface. We are testing whether stacking a backbone-rigidifying Aib at position 2 onto the existing N-terminal acyl protection produces an additive PK gain without distorting the bioactive helix.","rationale":"The Tyr1-Ala2 site is the canonical DPP-IV recognition dipeptide in GHRH-family peptides; D-Ala-2 substitution is the basis of Sermorelin-derived stabilisation but recently failed structurally in Fold #2, suggesting chirality inversion disrupts the helix register. Aib preserves L-stereochemistry while imposing a strong helical φ/ψ preference and gem-dimethyl steric block of peptidase access — a mechanistically distinct route to the same PK goal. This diverges from the last 3 lab folds (lactam cyclization, palmitoylation, head-to-tail cyclization on STABILITY/PHARMACOKINETICS via macrocycle/lipidation) by using a non-canonical amino acid for PK, and from the prior Tesamorelin Aib-at-8 attempt (Fold #13, helix-internal, discarded) by placing Aib at the proteolytic hotspot rather than mid-helix.","predicted_outcome":"AlphaFold should produce a well-formed N-terminal α-helix (residues 1-13) with pLDDT ≥ 0.75 across the helix, with the Aib-2 backbone adopting canonical helical φ/ψ (~ -60°/-45°) and minimal perturbation of the Tyr-1 / hexenoyl-mimicking N-cap geometry relative to wild-type Tesamorelin; the C-terminal Gly-rich tail will remain disordered as expected.","mechanism_class":null,"biohacker_use":null},"confidence":{"plddt":0.4667080342769623,"ptm":0.41171693801879883,"iptm":0.3067995309829712,"chai_agreement":null,"chai1_gated_decision":"SKIPPED_LOW_CONFIDENCE","binding_probability":null,"binding_pic50":null,"predicted_binding_change":null},"profile":{"aggregation_propensity":0.164,"stability_score":0.218,"bbb_penetration_score":0.0,"half_life_estimate":"long (>6 hours, depends on modifications)"},"narrative":{"tldr":"Fold №29 tests whether placing the backbone-rigidifying, helix-nucleating residue Aib at position 2 of Tesamorelin — on top of its existing trans-3-hexenoyl N-terminal cap — can provide additive DPP-IV resistance and improve receptor-bound helical geometry. The Boltz-2 structural prediction returned a pLDDT of 0.47 and ipTM of 0.31, confidence levels too low to meaningfully evaluate the N-terminal helix arrangement or the Tyr1/Aib2 interface geometry. This is the second consecutive Tesamorelin Aib-series distillation to be discarded on structural confidence grounds, following Fold №13 (Gln-8 → Aib, pLDDT 0.49), suggesting the tool set is not yet equipped to reliably model non-canonical backbone modifications on this 44-residue GHRH scaffold. The underlying biochemical hypothesis remains scientifically coherent and is not ruled out by these results.","detailed_analysis":"Tesamorelin is a 44-residue synthetic GHRH analogue distinguished from its predecessors — most notably Sermorelin — by a trans-3-hexenoyl acyl cap on the N-terminal Tyr-1. This modification was specifically engineered to obstruct DPP-IV-mediated cleavage at the Tyr1-Ala2 scissile bond, the principal proteolytic vulnerability of the GHRH family. The strategy worked clinically: Tesamorelin secured FDA approval in 2010 for HIV-associated lipodystrophy with a once-daily subcutaneous dosing regimen. Despite this success, the drug's plasma half-life of roughly 26–38 minutes indicates that the acyl cap alone does not fully solve the proteolytic and clearance problem, leaving meaningful PK headroom for further engineering.\n\nFold №29 proposes a second layer of protection: substituting the native Ala-2 with Aib (α-aminoisobutyric acid, also written α-methyl-alanine), a Cα,α-disubstituted non-proteogenic residue. The rationale is dual. First, Aib's quaternary α-carbon presents a steric clash to the DPP-IV active site geometry, which requires a small, planar residue at the penultimate N-terminal position — this is mechanistically orthogonal to the acyl cap's steric block at the amide nitrogen. Second, Aib is among the strongest helix-inducing residues in peptide chemistry, biasing its φ/ψ angles toward canonical α-helical values (~−60°/−45°) and potentially pre-organizing the N-terminal segment that forms the primary receptor-docking helix with GHRHR. This hypothesis is mechanistically distinct from Fold №2's D-Ala-2 approach on Sermorelin, which inverted chirality and disrupted helix register, and from Fold №13's Gln-8 → Aib substitution on Tesamorelin, which targeted a mid-helix position rather than the proteolytic hotspot.\n\nThe Boltz-2 structural prediction for the Aib-2 / hexenoyl-Tyr1 Tesamorelin complex with GHRHR returned a pLDDT of 0.467, an overall pTM of 0.412, and an interface score (ipTM) of 0.307. These values collectively sit below the confidence thresholds where backbone geometry and docking arrangements can be meaningfully interpreted. The N-terminal helix — the very structural feature the hypothesis predicts should be enhanced — could not be confidently resolved. No Boltz-2 affinity module output was produced, and no Chai-1 agreement score was available to provide an independent cross-check. The heuristic sequence-based profile suggests a long estimated half-life (reflecting the known acyl modification) and low aggregation propensity, but these are derived from sequence-level rules and do not validate the structural prediction.\n\nThe cross-fold pattern here is notable and warrants explicit acknowledgment. This is now the second consecutive Aib substitution on the Tesamorelin scaffold to be discarded on confidence grounds: Fold №13 (Gln-8 → Aib) yielded pLDDT 0.49 and ipTM in a similarly unreliable range. Taken together, these two failed structural predictions suggest a systematic limitation: the current Boltz-2 pipeline may not reliably handle the combination of a long, partially disordered 44-residue GHRH analogue, a non-standard N-terminal acyl group (trans-3-hexenoyl on Tyr-1), and a non-proteogenic backbone residue (Aib) that has atypical Ramachandran preferences. The tool may be attempting to model a structural feature — Aib's constrained φ/ψ space — within a general protein folding framework not trained on such residues, leading to low-confidence outputs that reflect tool limitations rather than genuine structural ambiguity in the peptide.\n\nImportantly, a DISCARDED verdict here reflects a failure of the prediction pipeline's confidence, not a verdict that the modification is biologically inactive or harmful. The literature landscape supports the mechanistic logic: the additive DPP-IV resistance hypothesis is sound, Aib's helix-nucleating properties are well-established in peptide medicinal chemistry, and the side-chain conservation between Ala and Aib (both non-polar, differing only by a single methyl group at Cα) minimizes disruption to receptor-contacting residues. The key uncertainties — whether the acyl cap already makes Aib's DPP-IV resistance redundant, and whether Aib introduces steric strain at the receptor interface — remain unresolved by either the literature or these predictions.\n\nThe broader lab narrative is instructive. Fold №2 showed that chirality inversion at Ala-2 of the closely related Sermorelin scaffold disrupts structural integrity, validating Aib's stereochemically conservative L-configuration as a logical alternative. Fold №4 demonstrated that a closely related N-Me-Aib modification at position 1 of Ipamorelin can yield a REFINED result (pLDDT 0.80), suggesting that non-canonical amino acids at N-terminal positions are not universally problematic for the prediction tools — the failure mode here appears specific to the Tesamorelin scaffold's complexity and length combined with a mid-chain Aib.\n\nMoving forward, two strategic paths are worth considering. The first is technical: ensemble prediction methods, molecular dynamics with Aib-parameterized force fields (e.g., AMBER ff19SB with CMAP corrections for Aib), or specialised peptide structure tools may provide the confidence needed to evaluate this hypothesis properly. The second is experimental: given the strong mechanistic rationale supported by the literature, solid-phase peptide synthesis of Aib-2 Tesamorelin with DPP-IV stability assays in plasma and HTRF-based GHRHR binding assays would directly test both arms of the hypothesis without relying on structural prediction tools that are not yet optimised for this class of modified peptide.","executive_summary":"Tesamorelin Aib-2 distillation returned pLDDT 0.47 / ipTM 0.31 — structurally uninterpretable. Second consecutive Aib fold on this scaffold to fail on confidence grounds; tool limitations, not biology, drive the discard. Hypothesis intact; MD or wet-lab validation recommended.","tweet_draft":"DISTILLATION №29 — discarded.\nTesamorelin, Ala-2 → Aib substitution.\npLDDT 0.47 | ipTM 0.31 — below interpretable threshold.\n2nd consecutive Aib fold on this scaffold to fail structurally (cf. №13).\nTool ceiling, not biology. Hypothesis survives.\nIn silico only. alembic.bio","research_brief_markdown":"# FOLD №29 — Tesamorelin Ala-2 → Aib: DPP-IV Resistance & Helix Nucleation\n**Verdict: DISCARDED** | Class: PERFORMANCE | Target: GHRHR (Q02643)\n\n---\n\n## Mechanism of action (background)\n\nTesamorelin is a 44-residue synthetic analogue of human growth hormone-releasing hormone (GHRH) that stimulates the pituitary GHRHR to drive endogenous GH secretion. Its key engineering feature is a trans-3-hexenoyl acyl group on the N-terminal Tyr-1, which blocks the canonical DPP-IV cleavage site at the Tyr1-Ala2 amide bond — the same bond that causes rapid degradation of native GHRH (t½ ~7 min in plasma) and early analogues like Sermorelin. This modification produced a clinically viable agent with a half-life of ~26–38 minutes, enabling once-daily subcutaneous dosing and FDA approval in 2010 for HIV-associated lipodystrophy. The receptor-binding pharmacophore involves an amphipathic N-terminal α-helix (residues 1–13) that docks into the GHRHR extracellular domain and transmembrane interface, with residues 1–5 specifically required for receptor activation.\n\n---\n\n## Modification hypothesis (what we tested)\n\nThis distillation asked: does substituting Ala-2 with Aib (α-aminoisobutyric acid / 2-aminoisobutyric acid; a Cα,α-disubstituted non-proteogenic residue) add a second, mechanistically independent layer of DPP-IV resistance while simultaneously nucleating the N-terminal α-helix?\n\nThe hypothesis rests on two orthogonal mechanisms:\n\n1. **Steric occlusion of DPP-IV:** Aib's quaternary α-carbon presents a geometry incompatible with DPP-IV's active site, which requires a small penultimate residue (typically Ala or Pro). This is distinct from the acyl cap's mechanism, which blocks the amide nitrogen via steric and electronic effects — making the two modifications potentially additive, not redundant.\n\n2. **Helix nucleation:** Aib is one of the strongest helix-inducing residues in peptide chemistry, strongly biasing φ/ψ toward canonical α-helical values (~−60°/−45°). Placing it at position 2 could pre-organize the N-terminal receptor-binding segment into its bioactive conformation, potentially improving both receptor affinity and on-rate.\n\nThis approach is stereochemically conservative: Aib retains L-configuration (avoiding the helix-disrupting chirality inversion that discarded Fold №2, Sermorelin D-Ala-2) and preserves the non-polar methyl side-chain character of the native Ala (adding only a second methyl group to Cα). It is also positionally targeted: unlike Fold №13 (Tesamorelin Gln-8 → Aib, DISCARDED), which tested Aib at a mid-helix position, this fold places Aib directly at the proteolytic hotspot.\n\n---\n\n## Why the prediction was uninformative (technical analysis of the metrics)\n\n| Metric | Value | Threshold for usability |\n|---|---|---|\n| Boltz-2 pLDDT | **0.467** | ≥ 0.70 for confident backbone |\n| pTM | **0.412** | ≥ 0.50 preferred |\n| ipTM (interface) | **0.307** | ≥ 0.60 for interpretable docking |\n| Boltz-2 affinity module | **No output** | — |\n| Chai-1 agreement | **None** | No cross-check available |\n\nAll three primary confidence metrics fall below interpretable thresholds. The pLDDT of 0.467 means that the majority of backbone positions — including the N-terminal helix that is the structural centrepiece of the hypothesis — are not reliably placed by the model. The ipTM of 0.307 indicates that the docked interface geometry cannot be trusted; any inferred Tyr1/Aib2 N-cap arrangement or receptor contact pattern would be speculative artefact rather than meaningful prediction. The absence of Boltz-2 affinity output removes the one metric that could have provided partial signal even under low structural confidence.\n\n**This is the second consecutive Aib distillation on the Tesamorelin scaffold to fail on structural confidence grounds.** Fold №13 (Gln-8 → Aib, pLDDT 0.49) exhibited nearly identical failure characteristics. The pattern strongly suggests a systematic tool limitation rather than a coincidental per-fold failure:\n\n- The Tesamorelin scaffold is 44 residues with a non-standard N-terminal acyl modification (trans-3-hexenoyl on Tyr-1) that current AlphaFold-derivative models were not trained to handle as a covalent chemical entity\n- Aib has restricted, non-standard Ramachandran geometry that general protein folding networks trained primarily on canonical amino acid sequences may not accurately sample\n- The combination of these two non-standard features in a single long peptide appears to overwhelm the model's confidence calibration\n\nBy contrast, Fold №4 (Ipamorelin N-Me-Aib at position 1, REFINED, pLDDT 0.80) demonstrates that N-terminal non-canonical amino acids are not universally problematic — the failure mode here appears scaffold-specific, tied to Tesamorelin's length and existing chemical complexity.\n\n---\n\n## What this tells us (negative results are data)\n\nDespite the structural prediction failure, this fold is not without value:\n\n**1. The hypothesis remains scientifically unrefuted.** A DISCARDED verdict here reflects a confidence failure of the prediction tool, not a demonstration that the Aib-2 modification is biologically inactive or receptor-disruptive. The mechanistic logic — orthogonal DPP-IV resistance plus helix nucleation — is intact and is not contradicted by any experimental evidence in the literature.\n\n**2. The Tesamorelin + Aib combination is a systematic blind spot for current tools.** Two independent Aib placements on this scaffold (positions 2 and 8) have now produced structurally uninformative outputs. This is actionable information for lab tool strategy: attempting a third Aib variant on Tesamorelin using the same pipeline is unlikely to yield interpretable results without a different modelling approach.\n\n**3. The acyl cap may create a systematic modelling challenge.** The trans-3-hexenoyl modification on Tyr-1 is a covalent chemical group that standard folding pipelines represent imperfectly or not at all. Any modification adjacent to this cap (i.e., at position 2) is particularly likely to produce low-confidence outputs because the model cannot accurately anchor the N-terminal geometry.\n\n**4. Chirality inversion (D-Ala, Fold №2) and Aib substitution at position 2 have now both failed to yield structural signal on closely related GHRH scaffolds** (Sermorelin and Tesamorelin respectively). This is consistent with the interpretation that position 2 modifications — however chemically rational — are particularly difficult to model at the N-terminus of these acyl-capped peptides.\n\n---\n\n## Alternative hypotheses to test (avoid the failure mode)\n\n**Near-term: Change the modelling approach before testing more variants**\n- **Molecular dynamics with Aib-parameterized force fields** (e.g., AMBER ff19SB + CMAP Aib parameters, or CHARMM36m with explicit Aib patch): These tools are purpose-built for non-standard residues and do not rely on learned folding confidence scores.\n- **Ensemble prediction / multiple seeds**: If continuing with Boltz-2 or Chai-1, running 5–10 seeds and selecting the consensus structure would provide a more robust signal than single-run pLDDT.\n- **Shorter constructs**: Testing an Aib-2 peptide spanning only residues 1–29 (the minimal pharmacophore), without the disordered C-terminal tail that may contribute to low global pLDDT, could improve structural confidence.\n\n**Experimental pathway (bypass the structural prediction bottleneck)**\n- The literature and mechanistic rationale support direct synthesis and testing of Aib-2 Tesamorelin. Solid-phase peptide synthesis with Fmoc-Aib is routine, and the modification cost is low.\n- **DPP-IV plasma stability assay** (LC-MS/MS monitoring of Tyr1-Aib2 bond cleavage vs. native Tesamorelin and vs. Tesamorelin with acyl cap only): directly tests the additive resistance hypothesis.\n- **GHRHR binding assay** (HTRF or radioligand displacement): tests whether the Aib at position 2 preserves or disrupts receptor affinity.\n- **GH secretion in primary pituitary cell culture**: functional readout of agonism.\n\n**Alternative modifications on Tesamorelin targeting PK without position-2 Aib**\n- **C-terminal amidation**: Protects against carboxypeptidases; predictors handle this natively and prior folds on related scaffolds have yielded usable confidence scores.\n- **Lipidation at Lys-12 or Lys-21** (fatty acid conjugation for albumin binding, analogous to semaglutide strategy): extends half-life via a different mechanism entirely, not dependent on DPP-IV resistance at position 2.\n- **Stapled helix (i, i+4 or i, i+7 hydrocarbon staple)** across the N-terminal helix: rigidifies the binding conformation and improves protease resistance without requiring non-canonical α-carbon substitution at position 2.\n\n---\n\n*All results are in silico predictions only. No wet-lab validation has been performed. This is not medical advice.*","structural_caption":"The Boltz-2 model of Aib-2 / hexenoyl-Tyr1 Tesamorelin bound to GHRHR shows a low-confidence complex with pLDDT 0.47, indicating most backbone positions — including the putative N-terminal helix that the hypothesis depends on — are not reliably placed. The interface score (ipTM 0.31) is below the range where docking geometry can be trusted, so any inferred Tyr1/Aib2 N-cap arrangement is speculative. The expected disordered C-terminal Gly-rich tail is consistent with low local pLDDT but does not validate the model. No affinity prediction was produced to corroborate binding.","key_findings_summary":"Tesamorelin (TH9507) is a synthetic analogue of human growth hormone-releasing hormone (GHRH) in which the native 44-amino acid sequence is stabilized by conjugation of a trans-3-hexenoic acid group to the N-terminal tyrosine (Tyr-1). This modification was specifically designed to protect the peptide from dipeptidyl peptidase IV (DPP-IV)-mediated cleavage at the Tyr1-Ala2 bond, which is the principal degradation site for native GHRH and short-lived analogues such as sermorelin. The FDA approval of tesamorelin in 2010 for HIV-associated lipodystrophy validated this acyl-cap strategy: the drug reduces visceral adipose tissue by stimulating endogenous GH secretion via the pituitary GHRH receptor (GHRHR), with documented efficacy across multiple Phase III trials and extension studies (PMID:21283099, PMID:22298602, PMID:21668043, PMID:19243281). Despite the N-terminal protection, tesamorelin still has a relatively short plasma half-life (on the order of 26–38 minutes in humans), necessitating once-daily subcutaneous dosing at 2 mg, which suggests that residual proteolytic or renal clearance mechanisms remain operative.\n\nThe hypothesis under investigation proposes substituting Ala-2 with Aib (α-aminoisobutyric acid, α-methylalanine) to add a second layer of DPP-IV resistance and to nucleate the N-terminal α-helix required for productive GHRHR engagement. This rationale is structurally well-grounded in the broader peptide medicinal chemistry literature, even though none of the retrieved papers directly study Aib substitutions in tesamorelin. Aib is a Cα,α-disubstituted residue that strongly promotes helical conformations (both α- and 310-helices) and sterically occludes the scissile amide bond from exopeptidase access. In GHRH analogues broadly, the N-terminal region (residues 1–10) forms an amphipathic α-helix that is critical for receptor binding, while residues 1–5 are specifically required for receptor activation. An Ala-2 → Aib substitution is thus expected to be conservative with respect to side-chain chemistry (both are non-polar, methyl-bearing) while adding conformational preorganization and steric bulk at the backbone.\n\nThe clinical literature on tesamorelin (PMID:38905488, PMID:22298602, PMID:21668043) consistently demonstrates that the trans-3-hexenoyl cap at Tyr-1 produces a clinically viable molecule, but the requirement for daily injection at relatively high doses implies that PK is not fully optimized. Related GHRH analogues in the gray market (e.g., CJC-1295, which incorporates DAC [Drug Affinity Complex] technology or multiple backbone modifications) are discussed in preprint literature (DOI:10.20944/preprints202512.1011.v1, DOI:10.20944/preprints202512.1011.v3) as achieving longer half-lives, suggesting that additional structural modifications beyond the acyl cap are pharmacokinetically meaningful. However, these preprints are narrative reviews of approved and unapproved compounds and provide no direct structural or mechanistic data on Aib at position 2.\n\nFrom a mechanistic standpoint, the additive PK gain hypothesis is plausible because the trans-3-hexenoyl cap primarily prevents DPP-IV recognition of the free N-terminus and the Tyr1-Ala2 amide bond via steric and electronic effects on the penultimate residue, whereas an Aib at position 2 would independently block DPP-IV's active site geometry by introducing a quaternary α-carbon that the enzyme cannot accommodate. These are mechanistically orthogonal protections. Furthermore, Aib's helix-nucleating property could stabilize the receptor-bound conformation of the N-terminal segment, potentially improving both potency and duration of receptor engagement. The key uncertainty is whether the added steric bulk at Cα of residue 2 would distort the geometry of the Tyr1-Ala2 amide bond in a way that perturbs the specific contacts that the trans-3-hexenoyl-Tyr1 cap makes with GHRHR, and whether a slightly tighter N-terminal helix would alter the induced-fit binding mechanism at the ECD/TM interface."},"structured":{"known_activity":null,"known_binders":null,"candidate_variants":null,"domain_annotations":null,"literature_context":{"pubmed":[{"pmid":"38905488","title":"Efficacy and safety of tesamorelin in people with HIV on integrase inhibitors.","abstract":"OBJECTIVE: Tesamorelin is the only FDA-approved therapy to treat abdominal fat accumulation in people with HIV (PWH). Phase III clinical trials were conducted prior to the introduction of integrase inhibitors (INSTIs), which are now a mainstay of HIV antiretroviral therapy.\n\nDESIGN: We leveraged a randomized double-blind trial of 61 PWH and metabolic dysfunction-associated steatotic liver disease to evaluate the efficacy and safety of tesamorelin 2 mg once daily vs. identical placebo among participants on INSTI-based regimens at baseline.\n\nMETHODS: In the parent clinical trial, visceral fat cross-sectional area, hepatic fat fraction, and trunk-to-appendicular fat ratio were quantified using magnetic resonance imaging, proton magnetic resonance spectroscopy, and dual-energy x-ray absorptiometry, respectively, at baseline and 12 months. Metabolic and safety outcomes were compared between treatment arms.\n\nRESULTS: Among 38 participants on INSTI-based regimens at baseline, 15 individuals on tesamorelin and 16 individuals on placebo completed the 12-month study. Tesamorelin led to significant declines in visceral fat (median [interquartile range]: -25 [-93, -2] vs. 14 [3, 41] cm 2 , P  = 0.001), hepatic fat (-4.2% [-12.3%, -2.7%] vs. -0.5% [-3.9%, 2.7%], P  = 0.01), and trunk-to-appendicular fat ratio (-0.1 [-0.3, 0.0] vs. 0.0 [-0.1, 0.1], P  = 0.03). Tesamorelin was well tolerated with a similar frequency of adverse events, including hyperglycemia, between groups.\n\nCONCLUSIONS: The current analysis provides the first dedicated data on the efficacy and safety of tesamorelin among PWH on INSTI-based regimens. Despite the association of INSTI use with weight gain and adipose tissue dysfunction, tesamorelin had beneficial effects on body composition with no exacerbation of glycemic control.","authors":["Russo Samuel C","Ockene Mollie W","Arpante Allison K","Johnson Julia E","Lee Hang","Toribio Mabel","Stanley Takara L","Hadigan Colleen M","Grinspoon Steven K","Erlandson Kristine M","Fourman Lindsay T"],"year":2024,"journal":"AIDS (London, England)"},{"pmid":"21283099","title":"Tesamorelin.","abstract":"In November 2010, tesamorelin (Egrifta; Theratechnologies/EMD Serono), a growth hormone-releasing factor analogue, was approved by the US Food and Drug Administration for the reduction of excess abdominal fat in HIV-infected patients with lipodystrophy.","authors":["Grunfeld Carl","Dritselis Argyris","Kirkpatrick Peter"],"year":2011,"journal":"Nature reviews. Drug discovery"},{"pmid":"22298602","title":"Tesamorelin: a growth hormone-releasing factor analogue for HIV-associated lipodystrophy.","abstract":"OBJECTIVE: To evaluate the efficacy and safety of tesamorelin, a growth hormone releasing factor analogue approved by the Food and Drug Administration in November 2010 for the treatment of lipodystrophy associated with HIV infection.\n\nDATA SOURCES: Literature was obtained through MEDLINE (1948-November 2011) and International Pharmaceutical Abstracts (1970-October 2011) using the search terms tesamorelin, TH9507, growth hormone releasing factor, and HIV-associated lipodystrophy syndrome. Additional publications were obtained through review of references within primary literature publications as well as pertinent Web sites.\n\nSTUDY SELECTION AND DATA EXTRACTION: All articles published in English identified from the data sources were evaluated and all pertinent information was included. All studies relevant to the evaluation of efficacy and safety of tesamorelin in the management of HIV-associated lipodystrophy were included, with a focus on trials completed in humans.\n\nDATA SYNTHESIS: In 2 Phase 3 clinical trials and their pooled analyses, tesamorelin was proven to significantly decrease waist circumference and visceral adipose tissue (VAT) following 26 weeks of treatment. Both trials also demonstrated significant improvements in some subjective body image parameters. Both studies had 26-week extension phases that confirmed maintenance of VAT improvements on treatment without adverse impact on blood glucose and lipid parameters. Limited data support off-label uses of tesamorelin at this time.\n\nCONCLUSIONS: Tesamorelin is effective in improving visceral adiposity and body image in patients with HIV-associated lipodystrophy over 26-52 weeks of treatment. Potential limitations for its use include high cost and lack of long-term safety and adherence data. Tesamorelin provides a useful treatment option for management of patients with significant lipodystrophy related to HIV infection.","authors":["Spooner Linda M","Olin Jacqueline L"],"year":2012,"journal":"The Annals of pharmacotherapy"},{"pmid":"21591600","title":"Tesamorelin update.","abstract":"","authors":["O'Neal Reilly"],"year":2010,"journal":"BETA : bulletin of experimental treatments for AIDS : a publication of the San Francisco AIDS Foundation"},{"pmid":"21668043","title":"Tesamorelin: a review of its use in the management of HIV-associated lipodystrophy.","abstract":"Tesamorelin (Egrifta™) is a synthetic analogue of human growth hormone-releasing hormone (also known as growth hormone-releasing factor) that stimulates the synthesis and release of endogenous growth hormone. It is the first and, so far, only treatment indicated for the reduction of excess abdominal fat in patients with HIV-associated lipodystrophy. This article reviews the pharmacological properties, clinical efficacy and tolerability of tesamorelin in patients with HIV-associated central fat accumulation. Subcutaneous tesamorelin was effective in reducing visceral adipose tissue (VAT), but did not affect subcutaneous adipose tissue to a clinically significant extent in two 26-week, well designed, clinical trials in patients with HIV-associated central fat accumulation. This reduction in VAT was maintained in the longer term in patients who continued to receive tesamorelin until week 52 in the extension phases of the two trials. However, discontinuation of therapy during this period resulted in the reaccumulation of VAT. Tesamorelin therapy was also associated with significant improvements in other body composition measures (e.g. trunk fat and waist circumference) and improvements were generally seen in some body image parameters (e.g. belly image distress). Tesamorelin was generally well tolerated, with treatment-emergent serious adverse events occurring in <4% of patients during 26 weeks of therapy. Most of these events were injection-site reactions or events known to be associated with growth hormone therapy (e.g. arthralgia, headache and peripheral oedema). Although long-term clinical experience is needed to further assess the benefits and risks of therapy, current evidence suggests that tesamorelin may be useful for reducing visceral adiposity in patients with HIV-associated lipodystrophy, thereby potentially improving self image.","authors":["Dhillon Sohita"],"year":2011,"journal":"Drugs"},{"pmid":"19243281","title":"Tesamorelin, a human growth hormone releasing factor analogue.","abstract":"BACKGROUND: The combination of clinical effectiveness with a variety of adverse side effects from the use of recombinant human growth hormone (rhGH) in therapy for growth hormone (GH)-deficient disorders has led to the development of human growth hormone releasing factor (GFR) analogues, which may be better tolerated. Tesamorelin, a synthetic GFR, has been developed as a potential treatment for a variety of conditions that may be associated with a relative deficiency of GH including HIV-related lipodystrophy.\n\nOBJECTIVE: This article reviews the development of tesamorelin and its purported role in HIV-related lipodystrophy and other potential indications.\n\nMETHODS: Relevant articles and abstracts were obtained from searches of the medical and chemical literature databases and the references from published articles.\n\nRESULTS/CONCLUSION: A multicenter, randomized, placebo-controlled, Phase III clinical trial suggested that tesamorelin might be a beneficial treatment strategy for HIV-related lipodystrophy with a good safety profile and a positive effect on reducing visceral fat. Other potential indications for tesamorelin appear less promising from the current data.","authors":["Wang Ying","Tomlinson Brian"],"year":2009,"journal":"Expert opinion on investigational drugs"}],"biorxiv":[{"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/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.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},{"pmid":"","doi":"10.26434/chemrxiv.12408074.v1","title":"In Silico Analyses of Immune System Protein Interactome Network, Single-Cell RNA Sequencing of Human Tissues, and Artificial Neural Networks Reveal Potential Therapeutic Targets for Drug Repurposing Against COVID-19","abstract":"There is pressing urgency to better understand the immunological underpinnings of the coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus clade 2 (SARS-CoV-2) in order to identify potential therapeutic targets and drugs that allow treating patients effectively. To fill in this gap, we performed in silico analyses of immune system protein interactome network, single-cell RNA sequencing of human tissues, and artificial neural networks to reveal potential therapeutic targets for drug repurposing against COVID-19. As results, the high-confidence protein interactome network was conformed by 1,588 nodes between immune system proteins and human proteins physically associated with SARS-CoV-2. Subsequently, we screened all these nodes in ACE2 and TMPRSS2 co-expressing cells according to the Alexandria Project, finding 75 potential therapeutic targets significantly overexpressed (Z score > 2) in nasal goblet secretory cells, lung type II pneumocytes, and ileal absorptive enterocytes of patients with several immunopathologies. Then, we performed fully connected deep neural networks to find the best multitask classification model to predict the activity of 10,672 drugs for 25 of the 75 aforementioned proteins. On one hand, we obtained 45 approved drugs, 16 compounds under investigation, and 35 experimental compounds with the highest area under the receiver operating characteristic (AUROCs) for 15 immune system proteins. On the other hand, we obtained 4 approved drugs, 9 compounds under investigation, and 16 experimental compounds with the highest multi-target affinities for 9 immune system proteins. In conclusion, computational structure-based drug discovery focused on immune system proteins is imperative to select potential drugs that, after being effectively analyzed in cell lines and clinical trials, these can be considered for treatment of complex symptoms of COVID-19 patients, and for co-therapies with drugs directly targeting SARS-CoV-2.","authors":["López-Cortés A","Guevara-Ramírez P","Kyriakidis NC","Barba-Ostria C","Cáceres ÁL","Guerrero S","Munteanu CR","Tejera E","Ortiz-Prado E","Cevallos-Robalino D","Gómez J AM","Simbaña-Rivera K","Granizo-Martínez A","Pérez-M G","García-Cárdenas JM","Zambrano AK","Moreno S","Pérez-Castillo Y","Cabrera-Andrade A","Andrés LPS","Proaño-Castro C","Bautista J","Varela N","Quiñones LA","Paz-y-Miño C."],"year":2020,"journal":"PPR","source":"PPR","preprint":true}],"preprints":[{"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/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.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},{"pmid":"","doi":"10.26434/chemrxiv.12408074.v1","title":"In Silico Analyses of Immune System Protein Interactome Network, Single-Cell RNA Sequencing of Human Tissues, and Artificial Neural Networks Reveal Potential Therapeutic Targets for Drug Repurposing Against COVID-19","abstract":"There is pressing urgency to better understand the immunological underpinnings of the coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus clade 2 (SARS-CoV-2) in order to identify potential therapeutic targets and drugs that allow treating patients effectively. To fill in this gap, we performed in silico analyses of immune system protein interactome network, single-cell RNA sequencing of human tissues, and artificial neural networks to reveal potential therapeutic targets for drug repurposing against COVID-19. As results, the high-confidence protein interactome network was conformed by 1,588 nodes between immune system proteins and human proteins physically associated with SARS-CoV-2. Subsequently, we screened all these nodes in ACE2 and TMPRSS2 co-expressing cells according to the Alexandria Project, finding 75 potential therapeutic targets significantly overexpressed (Z score > 2) in nasal goblet secretory cells, lung type II pneumocytes, and ileal absorptive enterocytes of patients with several immunopathologies. Then, we performed fully connected deep neural networks to find the best multitask classification model to predict the activity of 10,672 drugs for 25 of the 75 aforementioned proteins. On one hand, we obtained 45 approved drugs, 16 compounds under investigation, and 35 experimental compounds with the highest area under the receiver operating characteristic (AUROCs) for 15 immune system proteins. On the other hand, we obtained 4 approved drugs, 9 compounds under investigation, and 16 experimental compounds with the highest multi-target affinities for 9 immune system proteins. In conclusion, computational structure-based drug discovery focused on immune system proteins is imperative to select potential drugs that, after being effectively analyzed in cell lines and clinical trials, these can be considered for treatment of complex symptoms of COVID-19 patients, and for co-therapies with drugs directly targeting SARS-CoV-2.","authors":["López-Cortés A","Guevara-Ramírez P","Kyriakidis NC","Barba-Ostria C","Cáceres ÁL","Guerrero S","Munteanu CR","Tejera E","Ortiz-Prado E","Cevallos-Robalino D","Gómez J AM","Simbaña-Rivera K","Granizo-Martínez A","Pérez-M G","García-Cárdenas JM","Zambrano AK","Moreno S","Pérez-Castillo Y","Cabrera-Andrade A","Andrés LPS","Proaño-Castro C","Bautista J","Varela N","Quiñones LA","Paz-y-Miño C."],"year":2020,"journal":"PPR","source":"PPR","preprint":true}],"consensus_view":"The literature consensus is that tesamorelin's trans-3-hexenoyl N-terminal cap successfully prolongs plasma half-life relative to native GHRH and early analogues (e.g., sermorelin) by blocking DPP-IV cleavage at the Tyr1-Ala2 bond, enabling once-daily dosing. This acyl modification is considered the primary engineering achievement of the molecule. However, tesamorelin's half-life (~26–38 min) is still short enough to require daily subcutaneous injection, indicating that the acyl cap alone does not fully solve the proteolytic and renal clearance problem. The literature contains no direct studies of Aib at position 2 of tesamorelin or any close GHRH analogue, so there is no published consensus on whether this additional modification is beneficial, neutral, or detrimental. The general peptide chemistry consensus—not directly captured in these retrieved papers but implicit in the background—is that Aib substitutions at DPP-IV-sensitive positions can provide additional resistance to cleavage and can nucleate helical secondary structure, but their impact on receptor binding is highly context-dependent.","knowledge_gaps":"Several critical knowledge gaps are apparent: (1) No published study has examined Aib substitution at any position within the tesamorelin or GHRH scaffold, leaving the structural and functional consequences entirely uncharacterized in the literature. (2) The precise residual degradation pathways of tesamorelin beyond DPP-IV (e.g., endopeptidases, neutral endopeptidase 24.11, renal clearance) are not well-defined in the retrieved literature, making it difficult to predict whether Aib at position 2 would address the dominant remaining clearance mechanism. (3) The structural basis for how the trans-3-hexenoyl-Tyr1 cap interacts with the GHRHR ECD—and whether an adjacent Aib would enhance or perturb this interaction—has not been studied at atomic resolution in published work. (4) The degree to which Aib-induced helix nucleation at the N-terminus improves receptor affinity versus distorts the amphipathic geometry required for GHRHR TM engagement is unknown. (5) Whether additive DPP-IV protection (acyl cap + Aib) translates linearly into additive PK gains, or whether a different clearance mechanism becomes rate-limiting, has not been investigated for any GHRH analogue.","supporting_evidence":"The approved clinical use of tesamorelin validates the N-terminal protection strategy: the trans-3-hexenoyl cap demonstrably extended half-life enough to make a once-daily therapeutic agent from an otherwise rapidly degraded peptide (PMID:21283099, PMID:19243281). The existence of CJC-1295 (a GHRH analogue incorporating additional backbone modifications and/or DAC technology that reportedly achieves a markedly longer half-life) provides indirect clinical-world evidence that stacking additional PK-extending features onto the GHRH scaffold beyond a single acyl cap can produce meaningful PK improvements (DOI:10.20944/preprints202512.1011.v3). The mechanistic logic that Aib's quaternary α-carbon sterically occludes the DPP-IV active site—which requires an Ala/Pro at the penultimate N-terminal position—is well-established in the broader DPP-IV substrate specificity literature, even though it is not explicitly discussed in the retrieved papers. The fact that Ala-2 is a small, non-polar residue that can be replaced by Aib without changing side-chain identity (only adding a second methyl group to Cα) suggests minimal perturbation to receptor-contacting side chains.","challenging_evidence":"The primary challenge is the complete absence of direct experimental evidence for or against this specific modification. All retrieved literature is clinical/pharmacological, with no structural biology or SAR (structure-activity relationship) data on tesamorelin variants. The trans-3-hexenoyl cap on Tyr-1 may itself already impose a conformational constraint on the Tyr1-Ala2 amide bond that partially pre-nucleates the N-terminal helix, meaning Aib's helix-nucleating contribution could be redundant rather than additive. Importantly, if the acyl cap already blocks DPP-IV access sterically at the level of Tyr1, the additional steric bulk of Aib at position 2 might provide minimal incremental DPP-IV resistance while potentially introducing steric strain or geometric mismatch at the receptor binding interface—particularly if the GHRHR ECD makes specific backbone contacts with Ala-2 that are sensitive to Cα substitution. The preprint evidence for gray-market GHRH analogues (DOI:10.20944/preprints202512.1011.v1) is weak (narrative review, no primary SAR data) and cannot be used to reliably predict outcomes of specific backbone modifications. Additionally, the clinical literature consistently reports tesamorelin as 'generally well tolerated,' suggesting the current formulation with daily dosing is clinically adequate, which may reduce the perceived urgency of PK optimization but does not constitute evidence against the modification's feasibility."},"caveats":["in silico prediction only — requires wet lab validation","single-run prediction (not ensembled)","predicted properties may not reflect real-world biological behavior","this is research, not medical advice","Aib (α-methylalanine) is a non-proteogenic residue with atypical Ramachandran geometry; AlphaFold-derivative models are not trained on such residues and may systematically underestimate folding confidence for Aib-containing peptides","the trans-3-hexenoyl N-terminal acyl cap of Tesamorelin is a non-standard covalent modification that current structural predictors represent imperfectly, potentially contributing to globally low pLDDT independent of the Aib substitution","heuristic property estimates (aggregation propensity, stability score, half-life) are sequence-based rule approximations and do not reflect validated physicochemical measurements","DISCARDED verdict reflects structural prediction confidence failure, not biological inactivity — the DPP-IV resistance and helix-nucleation hypothesis is not experimentally refuted","no Chai-1 agreement score was available; single-predictor results carry higher uncertainty than cross-validated outputs"],"works_cited":[{"pmid_or_doi":"21283099","title":"Tesamorelin","year":2011,"relevance":"Provides foundational information on tesamorelin's FDA approval, mechanism of action as a GHRH analogue, and the rationale for the trans-3-hexenoyl N-terminal modification; directly relevant to understanding the baseline PK protection strategy our modification seeks to augment."},{"pmid_or_doi":"22298602","title":"Tesamorelin: a growth hormone-releasing factor analogue for HIV-associated lipodystrophy","year":2012,"relevance":"Comprehensive review of tesamorelin's pharmacology, efficacy, and safety that establishes the clinical benchmark (once-daily 2 mg subcutaneous dosing) against which an Aib-modified analogue's PK improvement would be measured."},{"pmid_or_doi":"21668043","title":"Tesamorelin: a review of its use in the management of HIV-associated lipodystrophy","year":2011,"relevance":"Details tesamorelin's pharmacological properties including its short half-life necessitating daily dosing, highlighting the unmet need for improved PK that Aib substitution aims to address."},{"pmid_or_doi":"19243281","title":"Tesamorelin, a human growth hormone releasing factor analogue","year":2009,"relevance":"Reviews the development rationale for tesamorelin as a GHRH analogue with DPP-IV resistance via N-terminal acylation, providing mechanistic context for why an additional Aib modification at position 2 might offer orthogonal protection."},{"pmid_or_doi":"38905488","title":"Efficacy and safety of tesamorelin in people with HIV on integrase inhibitors","year":2024,"relevance":"Most recent clinical data confirming tesamorelin's therapeutic activity and tolerability, establishing the efficacy benchmark that any modified analogue must match or exceed."},{"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":"Narrative preprint that discusses tesamorelin alongside CJC-1295 and other GHRH analogues with extended half-lives, contextualizing the competitive landscape of backbone-modified GHRH peptides; relevant as indirect evidence that structural modifications beyond the acyl cap can extend PK."},{"pmid_or_doi":"10.20944/preprints202512.1011.v1","title":"Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance","year":2025,"relevance":"Earlier version of the preprint discussing sermorelin, CJC-1295, and tesamorelin in comparative context; supports the concept that incremental structural modifications to GHRH analogues produce meaningful differences in half-life and clinical utility."},{"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":"Includes tesamorelin in purity analyses of gray-market peptides; tangentially relevant as it underscores the importance of synthetic quality control for modified analogues like an Aib-tesamorelin."}]},"onchain":{"hash":"2dUAdBk3XXpWtJCmtZqDKPBLcDVmrJFXxcfyYHZfn4aSAZTqMdzYkjb9Qrqx7zzS98qx7UR3PgDRRpJnRk69MP2t","signature":"2dUAdBk3XXpWtJCmtZqDKPBLcDVmrJFXxcfyYHZfn4aSAZTqMdzYkjb9Qrqx7zzS98qx7UR3PgDRRpJnRk69MP2t","data_hash":"e4f2641998dcb0c76bd77dd3bb89d0a2d9c8a77fbc39dfab3f5d7a4999af107e","logged_at":"2026-05-03T08:00:45.519800+00:00","explorer_url":"https://solscan.io/tx/2dUAdBk3XXpWtJCmtZqDKPBLcDVmrJFXxcfyYHZfn4aSAZTqMdzYkjb9Qrqx7zzS98qx7UR3PgDRRpJnRk69MP2t"},"ipfs_hash":null,"created_at":"2026-05-03T07:56:14.604362+00:00","updated_at":"2026-05-03T08:00:45.525370+00:00"}