RARE DISEASE
Obesity due to melanocortin 4 receptor deficiency
Obesity due to melanocortin 4 receptor deficiency
Obesity due to melanocortin 4 receptor deficiency
Synonyms: MC4R deficiency
Synonyms: MC4R deficiency
Synonyms: MC4R deficiency
Drug discovery
0
drugs
With orphan designations
Overview
Overview of Obesity Due to Melanocortin 4 Receptor Deficiency
MC4R deficiency is the most common monogenic cause of obesity, characterized by severe early-onset hyperphagia, accelerated linear growth in childhood, increased lean mass, and hyperinsulinemia [1][4][10]. It arises from heterozygous or homozygous mutations in the MC4R gene, disrupting hypothalamic appetite regulation. Adults exhibit lower hypertension prevalence but retain metabolic risks like type 2 diabetes and insulin resistance [4][7][9]. Penetrance varies by age, with higher obesity rates in childhood (79%) than older adults (40%) [2][14].
Burden
Comorbidities: Elevated risk of type 2 diabetes (independent of BMI in childhood), hyperleptinemia, and insulin resistance [7][9][16].
Growth and metabolic effects: Increased final adult height, accelerated BMI gain in childhood, and lower blood pressure compared to BMI-matched controls [4][10].
Psychosocial/economic impact: Significant healthcare costs due to early complications (e.g., obstructive sleep apnea, lymphedema) and reduced quality of life [15][16].
Therapies
Lifestyle modifications: Often insufficient due to impaired satiety signaling [4][16].
Pharmacotherapy: GLP-1 agonists (semaglutide, tirzepatide) show efficacy [4]; MC4R agonists (e.g., setmelanotide) are under investigation [8].
Surgery: Roux-en-Y bypass may benefit heterozygous patients but is ineffective in homozygotes [4][16].
Emerging therapies: Preclinical success with BDNF gene therapy targeting MC4R downstream pathways [3][13].
Categories: rare endocrine diseases, rare genetic diseases
Research Papers
604 drug discovery papers related to Obesity due to melanocortin 4 receptor deficiency, with 4 first-in-class and 0 next-in-class early-stage therapies forecasted to outperform the average preclinical success rate. Recent publications:
604 drug discovery papers related to Obesity due to melanocortin 4 receptor deficiency, with 4 first-in-class and 0 next-in-class early-stage therapies forecasted to outperform the average preclinical success rate. Recent publications:
2026-07-10 | The application of GLP-1 receptor agonists in obesity due to MC4R deficiency
Although the pathogenesis of genetic obesity is becoming increasingly clear, effective treatments remain lacking, particularly for obesity caused by melanocortin 4 receptor (MC4R) deficiency. The activity of MC4R is strictly regulated by its endogenous ligands: α-melanocyte-stimulating hormone (α-MSH) binds to MC4R and transmits anorexigenic and energy-expenditure signals, whereas agouti-related protein (AgRP) exerts an antagonistic effect by binding to the receptor, competitively inhibiting α-MSH action and promoting appetite. Current options, such as lifestyle modifications and bariatric surgery, have limited efficacy, highlighting the need for accessible pharmacological interventions. This review evaluates glucagon-like peptide-1 (GLP-1) receptor agonists in MC4R-deficient obesity. We conducted a comprehensive literature search across databases, including PubMed and Web of Science, compiling data from clinical trials, case reports, and basic research studies published up to 2025, with a focus on the efficacy, safety, and mechanism of action of drugs such as liraglutide, semaglutide, and tirzepatide in patients with MC4R deficiency. Evidence indicates these agents induce significant weight loss, appetite suppression, and metabolic improvements via mechanisms independent of intact MC4R signaling. Their weight-loss effects are comparable to those seen in common obesity, with additional benefits for comorbidities like insulin resistance and dyslipidemia. These findings support the GLP-1 pathway as an alternative to impaired MC4R, offering a viable treatment. Understanding their efficacy and mechanisms provides new treatment options for this rare condition and offers evidence for genetically specific personalized weight management.
2026-06-24 | Cardiometabolic regulation by adipocyte-derived leptin and the brain melanocortin system.
Tonic activation of central nervous system (CNS) leptin receptors (LepRs) and melanocortin 4 receptors (MC4Rs) is critical for maintaining normal cardiometabolic function. Deficiency of CNS LepR or MC4R signaling causes severe obesity and is accompanied by multiple metabolic abnormalities including insulin resistance, glucose intolerance, and hyperlipidemia that are only partially explained by obesity. Defective LepR and MC4R signaling also causes dysfunction of the sympathetic nervous system (SNS) and blood pressure (BP) regulation. Hyperleptinemia and activation of the CNS melanocortin system in obesity are important compensatory mechanisms that attenuate abnormalities of glucose and lipid metabolism but may also contribute to SNS activation and increased BP. Despite potentially adverse effects of increases in SNS activity and BP, pharmacological activation of brain LepRs and MC4Rs may provide an important therapeutic approach for protecting target organs, such as the heart, kidneys, and brain, from ischemic injury by improving mitochondrial function and ATP production. However, additional preclinical studies are needed to address mechanistic questions before clinical studies are begun to test the effectiveness of leptin and MC4R agonists for treating people with ischemic injury of target organs.
2026-05-27 | SKNY-1, a THCV Analog, Produces Weight Loss, Lipid Normalization and Attenuation of Reward-Associated Behaviors in an mc4r(G894C) Zebrafish Model of Obesity.
Obesity resulting from melanocortin-4 receptor (MC4R) dysfunction is characterized by combined metabolic dysregulation and maladaptive reward-related behaviors that limit the durability of existing therapies. The endocannabinoid system is a central regulator of appetite, lipid metabolism, and reward processing; however, first-generation cannabinoid receptor 1 (CB1) antagonists were limited by adverse neuropsychiatric effects. SKNY-1 is an orally active tetrahydrocannabivarin (THCV) analog designed to engage pathway-biased CB1 signaling, modulate cannabinoid receptor 2 (CB2), and selectively inhibit monoamine oxidase B (MAO-B), with the objective of addressing both metabolic and behavioral components of obesity while minimizing central nervous system liability through biased CB1 signaling, CB2 modulation, and potential complementary MAO-B inhibition. Here, we integrated in vitro pharmacological profiling of SKNY-1 with in vivo evaluation in an adult mc4r(G894C) zebrafish model exhibiting obesity-associated metabolic and reward-related phenotypes. In vitro, SKNY-1 displayed low-potency modulation of CB1 cyclic AMP signaling (EC50 ~30 µM) but more potent antagonism of the CB1 β-arrestin pathway (IC50 ~6 µM), consistent with differential CB1 pathway modulation. SKNY-1 acted as a CB2 partial agonist (EC50 ~0.1 µM), with antagonist activity emerging at higher concentrations, and selectively inhibited MAO-B at low affinity with no activity against MAO-A. In vivo, mc4r(G894C) zebrafish mutants exhibited dyslipidemia, hepatic triglyceride accumulation, altered appetite-regulatory gene expression, increased metabolic rate, and enhanced compulsive high-calorie feeding and nicotine-seeking behaviors. Oral administration of SKNY-1 for six days produced dose-dependent effects. Both doses normalized total cholesterol and low-density lipoprotein levels and reduced hepatic triglycerides toward wild-type values without affecting circulating triglycerides. The higher dose (200 ng per fish per day) induced significant body weight reduction while preserving body density and attenuated reward-associated feeding and nicotine-seeking behaviors. The lower dose (20 ng per fish per day) more effectively normalized the leptin a-to-ghrelin expression ratio. Collectively, these findings demonstrate that SKNY-1 engages integrated endocannabinoid and potential dopaminergic mechanisms to improve metabolic parameters and attenuate maladaptive reward-related behaviors in an MC4R-deficient vertebrate model, supporting its further translational investigation for obesity complicated by compulsive eating and substance-seeking behaviors.
2026-07-10 | The application of GLP-1 receptor agonists in obesity due to MC4R deficiency
Although the pathogenesis of genetic obesity is becoming increasingly clear, effective treatments remain lacking, particularly for obesity caused by melanocortin 4 receptor (MC4R) deficiency. The activity of MC4R is strictly regulated by its endogenous ligands: α-melanocyte-stimulating hormone (α-MSH) binds to MC4R and transmits anorexigenic and energy-expenditure signals, whereas agouti-related protein (AgRP) exerts an antagonistic effect by binding to the receptor, competitively inhibiting α-MSH action and promoting appetite. Current options, such as lifestyle modifications and bariatric surgery, have limited efficacy, highlighting the need for accessible pharmacological interventions. This review evaluates glucagon-like peptide-1 (GLP-1) receptor agonists in MC4R-deficient obesity. We conducted a comprehensive literature search across databases, including PubMed and Web of Science, compiling data from clinical trials, case reports, and basic research studies published up to 2025, with a focus on the efficacy, safety, and mechanism of action of drugs such as liraglutide, semaglutide, and tirzepatide in patients with MC4R deficiency. Evidence indicates these agents induce significant weight loss, appetite suppression, and metabolic improvements via mechanisms independent of intact MC4R signaling. Their weight-loss effects are comparable to those seen in common obesity, with additional benefits for comorbidities like insulin resistance and dyslipidemia. These findings support the GLP-1 pathway as an alternative to impaired MC4R, offering a viable treatment. Understanding their efficacy and mechanisms provides new treatment options for this rare condition and offers evidence for genetically specific personalized weight management.
2026-06-24 | Cardiometabolic regulation by adipocyte-derived leptin and the brain melanocortin system.
Tonic activation of central nervous system (CNS) leptin receptors (LepRs) and melanocortin 4 receptors (MC4Rs) is critical for maintaining normal cardiometabolic function. Deficiency of CNS LepR or MC4R signaling causes severe obesity and is accompanied by multiple metabolic abnormalities including insulin resistance, glucose intolerance, and hyperlipidemia that are only partially explained by obesity. Defective LepR and MC4R signaling also causes dysfunction of the sympathetic nervous system (SNS) and blood pressure (BP) regulation. Hyperleptinemia and activation of the CNS melanocortin system in obesity are important compensatory mechanisms that attenuate abnormalities of glucose and lipid metabolism but may also contribute to SNS activation and increased BP. Despite potentially adverse effects of increases in SNS activity and BP, pharmacological activation of brain LepRs and MC4Rs may provide an important therapeutic approach for protecting target organs, such as the heart, kidneys, and brain, from ischemic injury by improving mitochondrial function and ATP production. However, additional preclinical studies are needed to address mechanistic questions before clinical studies are begun to test the effectiveness of leptin and MC4R agonists for treating people with ischemic injury of target organs.
2026-05-27 | SKNY-1, a THCV Analog, Produces Weight Loss, Lipid Normalization and Attenuation of Reward-Associated Behaviors in an mc4r(G894C) Zebrafish Model of Obesity.
Obesity resulting from melanocortin-4 receptor (MC4R) dysfunction is characterized by combined metabolic dysregulation and maladaptive reward-related behaviors that limit the durability of existing therapies. The endocannabinoid system is a central regulator of appetite, lipid metabolism, and reward processing; however, first-generation cannabinoid receptor 1 (CB1) antagonists were limited by adverse neuropsychiatric effects. SKNY-1 is an orally active tetrahydrocannabivarin (THCV) analog designed to engage pathway-biased CB1 signaling, modulate cannabinoid receptor 2 (CB2), and selectively inhibit monoamine oxidase B (MAO-B), with the objective of addressing both metabolic and behavioral components of obesity while minimizing central nervous system liability through biased CB1 signaling, CB2 modulation, and potential complementary MAO-B inhibition. Here, we integrated in vitro pharmacological profiling of SKNY-1 with in vivo evaluation in an adult mc4r(G894C) zebrafish model exhibiting obesity-associated metabolic and reward-related phenotypes. In vitro, SKNY-1 displayed low-potency modulation of CB1 cyclic AMP signaling (EC50 ~30 µM) but more potent antagonism of the CB1 β-arrestin pathway (IC50 ~6 µM), consistent with differential CB1 pathway modulation. SKNY-1 acted as a CB2 partial agonist (EC50 ~0.1 µM), with antagonist activity emerging at higher concentrations, and selectively inhibited MAO-B at low affinity with no activity against MAO-A. In vivo, mc4r(G894C) zebrafish mutants exhibited dyslipidemia, hepatic triglyceride accumulation, altered appetite-regulatory gene expression, increased metabolic rate, and enhanced compulsive high-calorie feeding and nicotine-seeking behaviors. Oral administration of SKNY-1 for six days produced dose-dependent effects. Both doses normalized total cholesterol and low-density lipoprotein levels and reduced hepatic triglycerides toward wild-type values without affecting circulating triglycerides. The higher dose (200 ng per fish per day) induced significant body weight reduction while preserving body density and attenuated reward-associated feeding and nicotine-seeking behaviors. The lower dose (20 ng per fish per day) more effectively normalized the leptin a-to-ghrelin expression ratio. Collectively, these findings demonstrate that SKNY-1 engages integrated endocannabinoid and potential dopaminergic mechanisms to improve metabolic parameters and attenuate maladaptive reward-related behaviors in an MC4R-deficient vertebrate model, supporting its further translational investigation for obesity complicated by compulsive eating and substance-seeking behaviors.
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