Peptides and Obesity: Beyond GLP-1 Agonists

By the NorthPeptide Research Team  |  February 5, 2026

Why Obesity Research Looks Beyond GLP-1

GLP-1 receptor agonists work. The clinical trial data for semaglutide and tirzepatide is among the strongest in obesity pharmacology. But they are not universally tolerated (nausea, vomiting, GI side effects limit adherence for many), they are expensive, and they work primarily through appetite suppression rather than directly targeting fat tissue or energy expenditure. Researchers are exploring complementary and alternative peptide mechanisms that may offer different profiles — targeting adipogenesis, mitochondrial biogenesis, or multiple receptor pathways simultaneously.

AOD-9604: The Fat-Fragment Approach

AOD-9604 is a synthetic analogue of the C-terminal fragment of human growth hormone (hGH176-191). It was originally developed to retain the lipolytic (fat-burning) effects of HGH without the anabolic and diabetogenic properties of the full molecule. Preclinical research showed it stimulated lipolysis in adipose tissue and inhibited lipogenesis. Early human trials were promising, and it reached Phase IIb clinical development for obesity before the programme was halted on commercial rather than safety grounds. It has since been approved as a food ingredient in some jurisdictions.

Mechanistically, AOD-9604 is thought to act through a β3-adrenergic receptor-mediated pathway, independent of the IGF-1/insulin receptor axis. This is part of why it lacks the growth-promoting effects of full HGH.

MOTS-c: Mitochondrial Metabolic Regulation

MOTS-c is a mitochondrial-derived peptide (MDP) encoded within the 12S rRNA region of mitochondrial DNA. It was identified relatively recently (2015) and has attracted significant research interest for its role in metabolic regulation. MOTS-c has been shown in animal models to improve insulin sensitivity, reduce obesity on a high-fat diet, and enhance exercise capacity. Its mechanism involves AMPK activation and improved glucose uptake in skeletal muscle.

Unlike most obesity-targeting peptides, MOTS-c works at the mitochondrial level — improving how cells use energy rather than simply reducing caloric intake. This positions it as a potential complementary research compound to appetite-suppressing agents.

Multi-Receptor Agonism: Retatrutide and Beyond

The next wave of obesity peptide research involves simultaneous agonism at multiple receptors. Tirzepatide (GLP-1/GIP dual agonist) showed that adding receptors could dramatically improve efficacy. Retatrutide (GLP-1/GIP/glucagon triple agonist) is in late-stage trials with weight loss data showing up to 24% body weight reduction — numbers unprecedented in pharmaceutical history.

Researchers are also exploring GLP-1/FGF21 combinations, amylin analogues (cagrilintide), and peptide YY (PYY) as complementary targets. The field is moving rapidly toward multi-pathway approaches that address both appetite and energy expenditure simultaneously.

The Problem with Single-Target Approaches

Obesity is not a single-mechanism disease. It involves hormonal dysregulation (leptin resistance, insulin resistance, ghrelin signalling), central appetite control, peripheral energy expenditure, adipose tissue biology, gut microbiome interactions, and psychological factors. Research increasingly suggests that durable, significant weight loss may require targeting multiple pathways — which is why the multi-receptor agonist approach is attracting so much interest.

Adiponectin and Leptin-Sensitising Approaches

Adiponectin is an adipokine with anti-inflammatory and insulin-sensitising properties that is paradoxically low in obesity. Research into peptides that mimic or upregulate adiponectin signalling is ongoing. Similarly, leptin sensitisers (rather than leptin replacement, which fails due to leptin resistance) represent another research direction. Some investigators have explored whether peptides like MOTS-c or mitochondria-targeted compounds indirectly improve leptin sensitivity by improving cellular metabolic health.

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