TB-500

BACKGROUND: Peptide therapeutics represent an emerging frontier in gerontological medicine, targeting fundamental hallmarks of aging including metabolic dysfunction, telomere attrition, tissue repair impairment, and hormonal decline. OBJECTIVE: To comprehensively review the mechanisms, clinical applications, evidence base, and safety profiles of therapeutic peptides with demonstrated or potential applications in healthy aging and age-related conditions. METHODS: A comprehensive narrative review was conducted through systematic searches of PubMed, Scopus, and regulatory databases (FDA, WADA) from inception through January 2026. Search terms included "peptide therapeutics," "aging," "gerontology," "healthspan," combined with specific peptide names (tirzepatide, epitalon, GHK-Cu, BPC-157, TB-500, Semax, CJC-1295, ipamorelin, bremelanotide). Peer-reviewed articles, clinical trials, regulatory documents, and preclinical studies were evaluated. A total of 20 primary sources were selected based on relevance, methodological quality, and contribution to understanding peptide mechanisms and clinical outcomes in aging populations. RESULTS: Nine peptides were identified spanning diverse aging interventions: metabolic restoration (tirzepatide), telomere biology (epitalon), dermal regeneration (GHK-Cu), tissue repair (BPC-157, TB-500), neuroprotection (Semax), growth hormone modulation (CJC-1295, ipamorelin), and sexual function (bremelanotide). FDA-approved agents demonstrated robust safety profiles from large-scale trials. Non-approved peptides showed promising preclinical and limited clinical evidence but lack long-term safety data and systematic validation. Significant knowledge gaps include optimal dosing regimens, combination therapy effects, and biomarkers for monitoring efficacy. CONCLUSION: Therapeutic peptides offer mechanistically diverse approaches to multiple aging hallmarks. While FDA-approved agents demonstrate clinical potential, investigational peptides require rigorous validation through well-designed clinical trials to establish safety and efficacy for healthspan extension.

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 of 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 are 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.

BACKGROUND: Therapeutic peptides are short-chain amino acids that regulate cellular functions and facilitate biochemical processes. In recent years, there has been significant growth in the global market for therapeutic peptides and thus its popularity among patients. Given the increase in the development of peptides and increased marketing to patients for orthopaedic injuries, it is critical for orthopaedic surgeons to understand the current evidence behind these therapeutic peptides. PURPOSE: To evaluate the current evidence and applications of injectable peptide therapy, focusing on its potential in regenerative medicine and sports performance, to help orthopaedic providers better understand the current state of different therapeutic peptide approaches. STUDY DESIGN: Narrative review. METHODS: A comprehensive literature search was conducted using PubMed to identify biochemical and clinical studies on the most popular types of injectable peptide therapy. Key peptides evaluated included BPC-157, TB-4, TB-500, CJC-1295 + ipamorelin, tesamorelin, and GHK-Cu. RESULTS: BPC-157 demonstrated potential benefits in tendon and muscle repair, but these findings are largely unvalidated in human trials. A single human case series reported improvements in pain after intra-articular knee injections of BPC-157, although significant methodological flaws and a lack of controls limit its applicability and reliability. TB-4 and its derivative TB-500 promoted angiogenesis and tissue repair in preclinical models, but human orthopaedic data are lacking, and both remain banned substances in sports. CJC-1295 combined with ipamorelin showed significantly improved maximum tetanic tension in murine models with glucocorticoid-induced muscle loss, but these findings are limited to animal studies. Tesamorelin, approved for treating HIV-associated lipodystrophy, has no supporting orthopaedic evidence. GHK-Cu showed promise in wound healing and anti-inflammatory effects, but no clinical data support its use for musculoskeletal conditions. CONCLUSION: While peptide therapy may possess significant therapeutic and regenerative potential, it is critical that orthopaedic and sports medicine providers understand the current lack of evidence to support the clinical use of these peptides. Importantly, information regarding the indications, dosing, frequency, and duration of treatment remains unknown. Despite the popularity of these peptides in mainstream media and among patients, significant research regarding the safety and efficacy of these therapeutic methods is required before definitive recommendations can be made to patients.

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.

BACKGROUND: TB-500 (Ac-LKKTETQ), derived from the active site of thymosin β4 (Tβ4), has various biological functions in its unacetylated form, LKKTETQ. These functions include actin binding, dermal wound healing, angiogenesis, and skin repair. The biological effects of TB-500, however, have not been documented. And the analysis of TB-500 and its metabolites have been neither simultaneously quantified nor structurally identified using synthesized authentic standards. METHODS: This study was aimed to investigating simultaneous analytical methods of TB-500 and its metabolites in in-vitro and urine samples by using UHPLC-Q-Exactive orbitrap MS, and to comparing the biological activity of its metabolites with the parent TB-500. The metabolism of TB-500 was investigated in human serum, various in-vitro enzyme systems, and urine samples from rats treated with TB-500, and their biological activities measured by cytotoxicity and wound healing experiments were also evaluated in fibroblasts. RESULTS: The simultaneous analytical method for TB-500 and its metabolites was developed and validated. The study found that Ac-LK was the primary metabolite with the highest concentration in rats at 0-6 h intervals. Also, the metabolite Ac-LKK was a long-term metabolite of TB-500 detected up to 72 hr. No cytotoxicity of the parent and its metabolites was found. Ac-LKKTE only showed a significant wound healing activity compared to the control. CONCLUSION: The study provides a valuable tool for quantifying TB-500 and its metabolites, contributing to the understanding of metabolism and potential therapeutic applications. Our results also suggest that the previously reported wound-healing activity of TB-500 in literature may be due to its metabolite Ac-LKKTE rather than the parent form.

UNLABELLED: Small peptides with a molecular weight of <2kDa represent a performance-enhancing substances. However, in vivo studies with human volunteers are limited because most of these peptides are not approved for human consumption. Thus, relevant in vitro models are a basic tool to study their metabolism for anti-doping purposes. To choose the best in vitro model the biotransformation of growth hormone releasing peptides (GHRPs), Desmopressin and TB-500 was investigated using various in vitro systems. High metabolic activity was observed during incubation of GHRPs and TB-500 with human kidney microsomes (HKM) and liver S9 fraction. Peptides degraded through cleavage of all bonds regardless protective modifications in primary structure. HKM and liver S9 fraction demonstrated enzymatic deamidation activity removing C-terminal amide group from all GHRPs. Fewer metabolites were produced during incubation with human serum. The metabolite pattern obtained with commercially available proteases was poor and included nonspecific hydrolyzed compounds. Thus, the maximum diversity of metabolites was achieved with HKM and liver S9 fraction which makes them the most efficient in vitro model systems for peptides biotransformation study. BIOLOGICAL SIGNIFICANCE: Currently, >60 peptide medicines are FDA approved and marketed in the United States as biopharmaceutical products. Approximately 140 peptide drugs are in clinical trials and about 500 therapeutic peptides in preclinical development. There is an emerging interest in small peptides with a molecular weight of <2kDa, which can be used as doping in modern sport due a wide spectrum of their physiological activity. Most of peptide doping products are not yet approved for human use and some of them undergo preclinical or clinical trials, which complicates the study of metabolism in vivo. The investigation of the metabolism with in vitro methods is an alternative that does not require a human participation and an approval by the Ethics Committee.