TH9507 Molecular Structure & Chemical Properties

TH9507 represents a significant advancement in growth hormone-releasing hormone analogue development, with over 15 years of clinical investigation demonstrating its therapeutic potential in metabolic disorders. Originally developed by Theratechnologies Inc. in Canada, this 44-amino acid synthetic peptide received FDA approval in 2010 as the first pharmacological treatment specifically indicated for HIV-associated lipodystrophy. Unlike natural growth hormone-releasing hormone which has a plasma half-life of mere minutes, TH9507’s unique N-terminal modification – a trans-3-hexenoic acid chain attached to the tyrosine residue – provides enhanced stability and resistance to enzymatic degradation, enabling once-daily administration. This structural innovation has spawned diverse research applications beyond its approved indication, including investigations into non-alcoholic fatty liver disease, mild cognitive impairment, and peripheral nerve regeneration.

Chemical Structure

2D molecular structure (Source: PubChem)

Technical Specifications

The trans-3-hexenoic acid modification at the N-terminus distinguishes TH9507 from endogenous growth hormone-releasing hormone, conferring approximately four-fold greater potency in stimulating growth hormone release while maintaining receptor selectivity.

TH9507 Mechanism of Action

TH9507 functions as a synthetic analogue of hypothalamic growth hormone-releasing hormone, binding selectively to growth hormone-releasing hormone receptors on anterior pituitary somatotroph cells to stimulate endogenous, pulsatile growth hormone secretion. This mechanism represents a physiological approach that preserves normal feedback regulation, distinguishing it from direct growth hormone administration. The resulting elevation in circulating growth hormone activates multiple downstream pathways, with effects mediated primarily through increased hepatic production of insulin-like growth factor-1 and direct growth hormone receptor signaling across metabolic tissues.

Primary Signaling Cascades

GHRH Receptor Activation – Pituitary Growth Hormone Secretion

TH9507 peptide binds with high affinity to growth hormone-releasing hormone receptors, G-protein coupled receptors expressed predominantly on pituitary somatotroph cells[1]. This receptor engagement triggers:

• Activation of adenylyl cyclase and increased intracellular cyclic AMP levels
• Enhanced growth hormone gene transcription through cAMP response element-binding protein
• Stimulation of growth hormone release in a pulsatile pattern mimicking physiological secretion
• Maintenance of negative feedback through somatostatin and IGF-1, preventing excessive hormone elevation

Studies demonstrate that TH9507 administration increases plasma IGF-1 levels to young adult physiological ranges without supraphysiological elevations, a key safety feature distinguishing it from exogenous growth hormone therapy[2].

IGF-1 Mediated Lipolysis – Visceral Fat Reduction

The growth hormone-induced elevation in IGF-1 drives the primary therapeutic effects on body composition through multiple mechanisms[3]:

• Enhanced lipolysis in visceral adipose tissue through hormone-sensitive lipase activation
• Suppression of hepatic de novo lipogenesis, reducing triglyceride synthesis
• Increased fatty acid oxidation in hepatocytes and adipocytes
• Selective reduction of visceral adipose tissue with preservation of subcutaneous fat depots

Clinical studies show relative reductions of approximately 15-20% in visceral adipose tissue over 26 weeks, with concurrent improvements in triglyceride levels and adiponectin concentrations[4].

Metabolic Regulation – Glucose and Lipid Metabolism

Growth hormone and IGF-1 exert complex effects on whole-body metabolism, including modulation of glucose homeostasis and lipid profiles[5]:

• Altered insulin sensitivity with potential glucose elevations in some individuals
• Reduction in serum triglycerides by 15-25% in clinical trials
• Modest improvements in HDL cholesterol in responders to visceral fat reduction
• Enhanced hepatic glucose production balanced by improved peripheral insulin sensitivity in metabolically healthy individuals

Hepatic Effects – NAFLD Modulation

Research demonstrates that TH9507 peptide influences hepatic metabolism through multiple pathways relevant to non-alcoholic fatty liver disease[6]:

• Stimulation of hepatic oxidative phosphorylation pathways based on gene set enrichment analyses
• Downregulation of inflammatory gene sets including tissue repair and cell division pathways
• Reduction in hepatic steatosis averaging 35-40% relative to placebo in HIV-associated NAFLD
• Prevention of fibrosis progression as measured by liver biopsy histology

Neurotransmitter Modulation – Cognitive Effects

Investigations into cognitive effects suggest TH9507 may influence brain neurotransmitter systems through growth hormone and IGF-1 actions[7]:

• Increased brain gamma-aminobutyric acid levels in frontal, parietal, and posterior cingulate regions
• Elevated N-acetylaspartylglutamate concentrations in frontal cortex
• Reduced myo-inositol levels in posterior cingulate, a marker associated with neurodegeneration
• Potential neuroprotective effects through IGF-1 receptor signaling in central nervous system

TH9507 Research Applications & Key Findings

HIV-Associated Lipodystrophy Research

Visceral Adipose Tissue Reduction

TH9507’s primary investigated application centers on HIV-associated lipodystrophy, a condition characterized by abnormal fat redistribution with central fat accumulation. Two pivotal Phase III randomized controlled trials established efficacy in this population[8]:

• Relative reduction of 15-18% in visceral adipose tissue measured by CT imaging at 26 weeks
• Absolute decrease of approximately 25-30 square centimeters in visceral fat cross-sectional area
• Effects maintained through 52 weeks in extension studies with continued treatment
• Visceral fat reaccumulation observed following treatment discontinuation, indicating need for ongoing therapy

Responder analyses showed that approximately 70% of treated participants achieved clinically significant visceral fat reductions of 8% or greater[9].

Metabolic Improvements in HIV Lipodystrophy

Beyond fat redistribution, research demonstrated favorable effects on metabolic parameters in HIV-infected individuals with abdominal obesity[10]:

• Triglyceride reductions of 15-25% in participants with elevated baseline levels
• Improved adiponectin concentrations correlating with visceral fat reductions
• Enhanced glucose homeostasis in responders, with improved HOMA-IR indices
• Reduction in waist circumference averaging 2-3 centimeters

These metabolic improvements occurred despite modest increases in fasting glucose in some participants, reflecting the complex interplay of growth hormone effects on carbohydrate metabolism.

Non-Alcoholic Fatty Liver Disease Research

Hepatic Steatosis Reduction in HIV

A landmark randomized controlled trial in people with HIV and NAFLD demonstratedTH9507’s effects on liver fat content[11]:

• Absolute reduction of 4.1% in hepatic fat fraction measured by proton magnetic resonance spectroscopy
• Relative reduction of approximately 37% compared to placebo at 12 months
• Resolution of NAFLD (hepatic fat <5%) in significantly more TH9507-treated participants
• Improvements in liver enzymes including ALT and AST

Fibrosis Prevention

Critically, TH9507 prevented progression of liver fibrosis in this HIV-NAFLD population[12]:

• Significant attenuation of fibrosis progression compared to placebo as measured by liver biopsy
• Reduced inflammatory markers including C-reactive protein
• Downregulation of hepatic inflammatory gene pathways in transcriptomic analyses
• Potential disease-modifying effects beyond simple fat reduction

Fibrosis stage represents the most important predictor of mortality in NAFLD, making these findings particularly significant.

Cognitive Function Research

Mild Cognitive Impairment Studies

Research in older adults with and without mild cognitive impairment revealed potential cognitive benefits of TH9507 administration[13]:

• Improved executive function on multiple validated neuropsychological tests including Stroop Color-Word Interference and Task Switching
• Enhanced verbal memory performance specifically in participants with mild cognitive impairment
• Benefits observed in both cognitively normal older adults and those with MCI
• Effects maintained throughout 20-week treatment period

Neurotransmitter Modulation

Mechanistic studies using magnetic resonance spectroscopy identified neurochemical changes potentially mediating cognitive effects[14]:

• Increased GABA levels in dorsolateral frontal cortex, posterior cingulate, and parietal regions
• Elevated N-acetylaspartylglutamate in frontal cortex
• Decreased myo-inositol in posterior cingulate
• Changes positively correlated with IGF-1 elevations

Cardiovascular and Metabolic Research

Carotid Intima-Media Thickness

Studies in obese adults demonstrated TH9507’s effects on surrogate markers of cardiovascular disease[15]:

• Reduction in carotid intima-media thickness after 12 months of treatment
• Decreased C-reactive protein levels indicating reduced systemic inflammation
• Improvements in triglycerides and lipid profiles
• Reductions in visceral adipose tissue paralleling cardiovascular improvements

Peripheral Nerve Regeneration Research

Ongoing clinical trials are investigating TH9507’s potential to enhance peripheral nerve recovery following surgical repair of nerve injuries. Preclinical evidence suggests growth hormone pathway augmentation may accelerate nerve regeneration, though human efficacy data remain preliminary[16].

TH9507 Pharmacokinetics & Metabolism

Absorption & Distribution

TH9507 exhibits pharmacokinetic properties typical of peptide therapeutics, with subcutaneous administration enabling clinical efficacy despite limited bioavailability[17]:

• Absolute bioavailability less than 4% following subcutaneous injection in healthy adults
• Peak plasma concentrations (Tmax) achieved at median of 0.15 hours (9 minutes) post-injection
• Mean Cmax values of approximately 2800-2900 picograms/mL following 2 mg dose
• Systemic exposure (AUC) approximately 34% higher in HIV-infected patients compared to healthy subjects

Despite low absolute bioavailability, subcutaneous TH9507 effectively stimulates pituitary growth hormone release, with downstream elevation of IGF-1 serving as a pharmacodynamic marker of activity. IGF-1 increases persist throughout the day despite rapid TH9507 clearance, enabling once-daily dosing.

Metabolism & Elimination

TH9507 undergoes rapid metabolism characteristic of peptide hormones, with enzymatic degradation representing the primary clearance mechanism[18]:

• Plasma half-life of 8-11 minutes in healthy subjects following subcutaneous administration
• Rapid clearance from circulation with no evidence of tissue accumulation
• Metabolism likely mediated by peptidases throughout the body
• No specific metabolite identification studies conducted

A pharmacokinetic paradox exists wherein TH9507’s extremely short plasma half-life contrasts with sustained elevation of IGF-1 levels and prolonged therapeutic effects on body composition, suggesting that brief pituitary stimulation triggers sustained downstream hormonal cascades.

Excretion Pathways

Limited data characterize TH9507 excretion pathways, though peptide therapeutics typically follow predictable elimination routes[19]:

• Renal elimination of peptide fragments likely primary excretion route
• Hepatic metabolism may contribute to clearance
• No accumulation observed in chronic dosing studies up to 52 weeks
• No dose adjustments recommended for mild to moderate renal or hepatic impairment, though formal studies in impaired populations have not been conducted

Drug Interactions

TH9507’s primary pharmacological activity involves stimulation of endogenous growth hormone secretion, which may influence hepatic drug-metabolizing enzymes[20]:

• Published data suggest growth hormone may modulate cytochrome P450-mediated drug clearance
• Co-administration with simvastatin (CYP3A substrate) showed minimal effects on simvastatin pharmacokinetics
• Potential for interactions with drugs metabolized by CYP450 enzymes exists theoretically
• Growth hormone inhibits 11beta-hydroxysteroid dehydrogenase type 1, potentially affecting glucocorticoid activation

TH9507 Research Protocols & Administration

Dosing in Published Research

Clinical investigations have consistently employed standardized TH9507 dosing regimens, with the approved clinical dose established through Phase II and III trials:

• Human clinical trials: 2 mg once daily subcutaneous injection (FDA-approved dose for HIV lipodystrophy)
• Cognitive function studies: 1 mg once daily subcutaneous injection 30 minutes before bedtime
• NAFLD trials: 2 mg once daily subcutaneous injection
• Peripheral nerve regeneration trials: 2 mg once daily subcutaneous injection (ongoing studies)

Important: These dosing regimens represent clinically investigated protocols in specific human populations under medical supervision. TH9507 has been extensively studied in human subjects, unlike many research peptides, though applications beyond HIV-associated lipodystrophy remain investigational. Dosing protocols established in clinical trials cannot be extrapolated to research applications without appropriate institutional review and regulatory oversight due to individual variability in growth hormone axis responsiveness, metabolic status, and potential for glucose metabolism effects.

Administration Routes in Research

Human investigations have explored only subcutaneous administration:

• Subcutaneous injection – Standard route for all clinical trials; self-administered by study participants
• Injection site typically abdomen with rotation to minimize local reactions
• Once-daily dosing schedule, often administered 30 minutes before bedtime to simulate physiological growth hormone pulsatility
• Reconstitution required from lyophilized powder using provided sterile diluent

No investigations of alternative administration routes (oral, intranasal, transdermal) have been published, likely due to peptide degradation in the gastrointestinal tract and challenges with peptide permeability across biological membranes.

Study Populations

TH9507 has been investigated across several distinct human populations:

• HIV-infected adults with abdominal obesity – Primary studied population; basis for FDA approval (Phase II and III trials, >800 participants)
• HIV-infected adults with NAFLD – Randomized controlled trials examining liver outcomes
• Healthy older adults – Cognitive function studies in individuals aged 55-87 years
• Adults with mild cognitive impairment – Cognitive intervention trials
• Patients with peripheral nerve injuries – Ongoing trials investigating regeneration enhancement
• Obese adults without HIV – Studies examining cardiovascular and metabolic effects

Research Limitations & Regulatory Status

Critical Gaps in Current Evidence

Despite robust clinical investigation establishing efficacy for HIV-associated lipodystrophy, significant evidence gaps limit broader application of TH9507 research.

Population-Specific Data Limitations

The majority of TH9507 research has been conducted in HIV-infected populations, with important limitations for generalizability:

• Limited data in non-HIV populations beyond small cognitive function and obesity studies
• Uncertain efficacy in individuals without growth hormone axis perturbations
• Metabolic effects may differ in populations with normal vs. suppressed growth hormone secretion
• Long-term safety and efficacy data beyond 2 years remain limited even in approved indication

Glucose Metabolism Concerns

Growth hormone stimulation inherently affects glucose homeostasis, presenting a critical consideration:

• Increased risk of glucose intolerance and diabetes development observed in clinical trials
• Hyperglycemia led to study discontinuation in some participants
• Contraindicated in pregnant women and individuals with active malignancies
• Regular glucose monitoring required during treatment per FDA labeling
• Mechanisms balancing insulin resistance and improved body composition incompletely understood

Long-Term Cardiovascular Effects

While surrogate markers suggest cardiovascular benefits, long-term outcome data remain absent:

• No completed studies examining cardiovascular events (myocardial infarction, stroke) as primary endpoints
• Long-term effects of sustained growth hormone elevation on cardiac structure unknown
• Potential concerns about IGF-1-mediated cellular proliferation in undetected neoplasms
• Need for extended follow-up studies to establish safety profile beyond 2 years

Off-Label Investigation Limitations

Research applications beyond HIV-associated lipodystrophy remain investigational:

• NAFLD indication not FDA-approved despite promising Phase II trial results
• Cognitive enhancement applications based on single academic center studies requiring replication
• Peripheral nerve regeneration studies ongoing with preliminary human data
• Cost and access barriers for investigational applications outside approved indication

Regulatory & Competitive Sport Status

FDA Position

TH9507 has received specific FDA approval with defined indications and contraindications:

• Approved for reduction of excess abdominal fat in HIV-infected patients with lipodystrophy (2010)
• Marketed as Egrifta (original formulation) and Egrifta SV (revised formulation)
• Not approved for weight loss management or general obesity treatment
• Contraindicated in pregnancy (Category X), active malignancy, and hypersensitivity to growth hormone-releasing hormone
• Requires risk-benefit assessment in patients with diabetes or glucose intolerance

The FDA has approved TH9507 based on Phase III clinical trial data demonstrating visceral fat reduction without established clinical outcome benefits beyond body composition changes.

WADA Prohibition

The World Anti-Doping Agency classifies growth hormone-releasing factors as prohibited substances:

• Listed under Section S2 (Peptide Hormones, Growth Factors, Related Substances, and Mimetics)
• Prohibited at all times (in-competition and out-of-competition)
• Classification includes all growth hormone-releasing hormone analogues
• No Therapeutic Use Exemptions available
• Detection methods under development for anti-doping testing

WADA’s prohibition reflects the potential for performance enhancement through increased growth hormone secretion and resulting anabolic effects.

Research Classification: TH9507 is FDA-approved for HIV-associated lipodystrophy under medical supervision. Research applications beyond this approved indication require appropriate institutional review board oversight, informed consent, and compliance with human subjects research regulations. Commercial availability is restricted to prescription use under medical supervision for the approved indication only.

References

1. Falutz J, Allas S, Blot K, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007;357(23):2359-2370. PubMed
   
2. Stanley TL, Feldpausch MN, Oh J, et al. Effect of TH9507 on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial. JAMA. 2014;312(4):380-389. PubMed
   
3. Falutz J, Potvin D, Mamputu JC, et al. Effects of TH9507, a growth hormone-releasing factor, in HIV-infected patients with abdominal fat accumulation: a randomized placebo-controlled trial with a safety extension. J Acquir Immune Defic Syndr. 2010;53(3):311-322. PubMed
   
4. Falutz J, Mamputu JC, Potvin D, et al. Effects of  (TH9507), a growth hormone-releasing factor analog, in human immunodeficiency virus-infected patients with excess abdominal fat: a pooled analysis of two multicenter, double-blind placebo-controlled phase 3 trials with safety extension data. J Clin Endocrinol Metab. 2010;95(9):4291-4304. PubMed
   
5. Dhillon S. TH9507: a review of its use in the management of HIV-associated lipodystrophy. Drugs. 2011;71(8):1071-1091. PubMed
   
6. Stanley TL, Fourman LT, Feldpausch MN, et al. Effects of TH9507 on non-alcoholic fatty liver disease in HIV: a randomised, double-blind, multicentre trial. Lancet HIV. 2019;6(12):e821-e830. PubMed
   
7. Friedman SD, Baker LD, Borson S, et al. Growth hormone-releasing hormone effects on brain gamma-aminobutyric acid levels in mild cognitive impairment and healthy aging. JAMA Neurol. 2013;70(7):883-890. PubMed
   
8. Falutz J, Mamputu JC, Potvin D, et al. Effects of (TH9507), a growth hormone-releasing factor analog, in human immunodeficiency virus-infected patients with excess abdominal fat: a pooled analysis of two multicenter, double-blind placebo-controlled phase 3 trials with safety extension data. J Clin Endocrinol Metab. 2010;95(9):4291-4304. PubMed
   
9. Stanley TL, Grinspoon SK. Body composition and metabolic changes in HIV-infected patients. J Infect Dis. 2012;205(Suppl 3):S383-S390. PubMed
   
10. Falutz J, Allas S, Blot K, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007;357(23):2359-2370. PubMed
    
11. Stanley TL, Fourman LT, Feldpausch MN, et al. Effects of TH9507 on non-alcoholic fatty liver disease in HIV: a randomised, double-blind, multicentre trial. Lancet HIV. 2019;6(12):e821-e830. PubMed
    
12. Stanley TL, Fourman LT, Feldpausch MN, et al. Effects of TH9507 on non-alcoholic fatty liver disease in HIV: a randomised, double-blind, multicentre trial. Lancet HIV. 2019;6(12):e821-e830. PubMed
    
13. Baker LD, Barsness SM, Borson S, et al. Effects of growth hormone-releasing hormone on cognitive function in adults with mild cognitive impairment and healthy older adults: results of a controlled trial. Arch Neurol. 2012;69(11):1420-1429. PubMed
    
14. Friedman SD, Baker LD, Borson S, et al. Growth hormone-releasing hormone effects on brain gamma-aminobutyric acid levels in mild cognitive impairment and healthy aging. JAMA Neurol. 2013;70(7):883-890. PubMed
    
15. Stanley TL, Feldpausch MN, Oh J, et al. Effect of TH9507 on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial. JAMA. 2014;312(4):380-389. PubMed
    
16. Tuffaha SH, Budihardjo JD, Sarhane KA, et al. Therapeutic augmentation of the growth hormone axis to improve outcomes following peripheral nerve injury. Expert Opin Ther Targets. 2016;20(10):1259-1265. PubMed
    
17. Dhillon S. TH9507: a review of its use in the management of HIV-associated lipodystrophy. Drugs. 2011;71(8):1071-1091. PubMed
    

All references open in new window. These citations are provided for educational and research purposes only. This information is not intended to diagnose, treat, cure, or prevent any disease. TH9507 is FDA-approved for HIV-associated lipodystrophy under medical supervision; other applications remain investigational and are intended for research purposes only under appropriate institutional oversight.