Oxyntomodulin (OXM)
Oxyntomodulin is a 37-amino acid peptide derived from proglucagon processing in intestinal L-cells, consisting of the full glucagon sequence plus an 8-residue C-terminal extension. As a natural dual GLP-1 receptor and glucagon receptor agonist, oxyntomodulin uniquely combines appetite suppression with increased energy expenditure, producing weight loss exceeding GLP-1 agonism alone and inspiring the design of next-generation dual agonist therapeutics.
Oxyntomodulin (OXM) is a 37-amino acid peptide hormone produced by post-translational processing of proglucagon in intestinal L-cells and brainstem neurons. Structurally, OXM consists of the complete 29-amino acid glucagon sequence followed by an 8-residue C-terminal extension known as intervening peptide 1 (IP-1) or the "octapeptide spacer." First identified by Bataille et al. in 1981 for its ability to inhibit pentagastrin-stimulated acid secretion in oxyntic (acid-producing) gastric mucosa — hence the name — OXM has emerged as a key peptide in metabolic research due to its unique pharmacology as a dual agonist at both the GLP-1 receptor (GLP-1R) and the glucagon receptor (GCGR).
Overview
OXM is co-secreted with GLP-1 and peptide YY (PYY) from enteroendocrine L-cells in the distal ileum and colon in response to nutrient ingestion. Postprandial OXM levels rise within 15–30 minutes of eating, peak at approximately 30–60 minutes, and return to baseline within 3–4 hours. The magnitude of OXM release is proportional to caloric load, with mixed meals producing the strongest response Le Quellec et al. (1992).
The C-terminal octapeptide extension (IP-1) profoundly alters OXM's receptor pharmacology compared to glucagon. While glucagon activates GCGR with high potency and has negligible GLP-1R activity, the IP-1 extension reduces OXM's GCGR affinity approximately 10-fold while conferring meaningful GLP-1R agonism (approximately 50-fold lower potency than GLP-1 itself). This creates a balanced dual agonist profile: OXM activates both receptors at moderate potency, producing physiological effects that neither glucagon nor GLP-1 alone can replicate Jorgensen et al. (2007).
Despite its lower receptor potencies compared to the native ligands, OXM produces robust metabolic effects in vivo. This apparent paradox is partly explained by the combinatorial nature of dual receptor activation — the metabolic benefits of simultaneous GLP-1R and GCGR signaling are synergistic rather than merely additive, and OXM's moderate potency at both receptors avoids the adverse effects associated with maximal activation of either receptor alone.
Mechanism of Action
OXM exerts its metabolic effects through simultaneous activation of two class B GPCRs:
- GLP-1 receptor agonism: OXM activates GLP-1R at ~50-fold lower potency than GLP-1(7-36)amide. This moderate GLP-1R activation mediates appetite suppression via hypothalamic and brainstem circuits (arcuate nucleus POMC activation, NTS signaling), slows gastric emptying, and produces the characteristic GI side effects (nausea) at higher doses. GLP-1R activation contributes approximately 50–60% of OXM's anorexigenic effect based on receptor antagonist studies Baggio et al. (2004).
- Glucagon receptor agonism: OXM activates GCGR at ~10-fold lower potency than glucagon. GCGR activation in hepatocytes stimulates glycogenolysis and gluconeogenesis acutely, but chronically promotes fatty acid oxidation, amino acid catabolism, and thermogenesis. The GCGR component is responsible for OXM's energy expenditure increase — a 3–5% increase in resting metabolic rate not seen with pure GLP-1R agonists Kosinski et al. (2012).
- Synergistic weight loss mechanism: The combination of reduced energy intake (primarily GLP-1R) and increased energy expenditure (primarily GCGR) creates a dual metabolic deficit. In GLP-1R knockout mice, OXM retains partial weight loss efficacy through GCGR-mediated energy expenditure, and in GCGR knockout mice, OXM retains partial efficacy through GLP-1R-mediated appetite suppression. Only blockade of both receptors abolishes OXM's weight loss effects Kosinski et al. (2012).
- Gastric acid inhibition: OXM's original pharmacological activity — inhibition of pentagastrin-stimulated gastric acid secretion — appears to be mediated through a mechanism not fully explained by either GLP-1R or GCGR activation alone, suggesting possible additional receptor interactions or paracrine effects Bataille et al. (1981).
- DPP-4 degradation: OXM is rapidly inactivated by DPP-4, which cleaves the His¹-Ser² N-terminal dipeptide, abolishing both GLP-1R and GCGR activity. This degradation, combined with renal clearance, produces the extremely short plasma half-life of approximately 12 minutes, limiting the therapeutic utility of native OXM Zhu et al. (2003).
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Oxyntomodulin (OXM)
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Research
Weight Loss in Humans — IV Infusion Studies
The initial human weight loss data came from intravenous infusion studies at Imperial College London. Cohen et al. demonstrated that preprandial OXM infusion over 4 days reduced ad libitum food intake by 19.3% compared to saline infusion, with cumulative weight loss of 0.5 kg over the 4-day period Cohen et al. (2003). fMRI studies revealed that OXM infusion modulated activity in hypothalamic and reward-processing brain regions, reducing the neural response to palatable food cues — an effect pattern consistent with dual GLP-1R/GCGR activation affecting both homeostatic and hedonic feeding circuits.
Subcutaneous OXM for Obesity — 4-Week Trial
The landmark subcutaneous OXM trial by Wynne et al. randomized overweight and obese volunteers to self-administered preprandial OXM (400 nmol three times daily) or saline for 4 weeks. OXM-treated subjects lost 2.3 kg (2.4% body weight) versus 0.5 kg in the placebo group, with the weight loss driven by both reduced caloric intake (~250 kcal/day) and increased energy expenditure (~143 kcal/day measured by indirect calorimetry) Wynne et al. (2005). This study was pivotal because it demonstrated:
- Dual mechanism in humans: Both appetite reduction and energy expenditure increase contributed to weight loss — a combination not seen with GLP-1R agonists alone.
- No tachyphylaxis: The appetite-suppressive effect was maintained throughout the 4-week treatment period.
- Increased activity energy expenditure: OXM-treated subjects showed increased ambulatory activity, suggesting that OXM enhances both resting and activity-related energy expenditure.
- Tolerability: The most common side effect was mild, transient nausea in approximately 10% of injections.
Energy Expenditure — The GCGR Advantage
The energy expenditure component of OXM's metabolic effects is its key differentiator from pure GLP-1R agonists. Wynne et al. showed that 4 weeks of subcutaneous OXM increased total energy expenditure by approximately 26%, a finding subsequently confirmed in acute infusion studies. This effect is mediated primarily through GCGR activation, which increases hepatic fatty acid oxidation, stimulates brown adipose tissue thermogenesis (in rodents), and may increase skeletal muscle energy expenditure Wynne et al. (2006). The 3-fold greater weight loss observed with OXM versus equimolar GLP-1 infusion in some preclinical studies is largely attributable to this energy expenditure component, since the appetite-suppressive effects are quantitatively similar.
Comparison with GLP-1 Receptor Agonists
Direct comparisons between OXM and GLP-1 administration have illuminated the unique value of dual agonism:
- Appetite suppression: Comparable between OXM and GLP-1 at equianorexigenic doses.
- Energy expenditure: Increased by OXM but not by GLP-1 alone. This is the critical differentiator.
- Body composition: OXM preferentially reduces fat mass with relative preservation of lean mass, likely due to GCGR-mediated fat oxidation. GLP-1R agonists tend to produce proportional fat and lean mass loss.
- Hepatic fat: GCGR activation promotes hepatic lipid oxidation. OXM and designed dual agonists show superior liver fat reduction compared to pure GLP-1R agonists, making them attractive for MASH/MASLD Tan et al. (2017).
- Glycemic effects: OXM has modest insulinotropic activity (via GLP-1R) partially offset by GCGR-mediated hepatic glucose output. Net glycemic effect is neutral to mildly beneficial.
DPP-4 Resistance and Modified Analogs
Native OXM's clinical utility is severely limited by its ~12-minute half-life due to DPP-4 cleavage at the His¹-Ser² bond. Strategies to extend OXM's duration of action include:
- Fatty acid acylation: Conjugation with C16–C18 fatty acid chains promotes albumin binding, reducing renal clearance and DPP-4 access (approach used in cotadutide and survodutide).
- N-terminal modifications: Substitution or protection of the His¹-Ser² DPP-4 cleavage site. Aib² substitution (aminoisobutyric acid at position 2) confers DPP-4 resistance while maintaining dual receptor activity.
- PEGylation: PEG conjugation extends half-life to hours–days in preclinical models.
- D-amino acid substitution: Selected D-amino acid replacements reduce proteolytic degradation.
- Fc fusion: Fusion with immunoglobulin Fc domain extends half-life to days. Used in some preclinical OXM analogs.
These modification strategies have produced analogs with half-lives suitable for once-weekly dosing, enabling the clinical trials of dual agonists described above.
MASH/MASLD — Hepatic Effects
The GCGR component of OXM's dual agonism has particular relevance for metabolic-associated steatohepatitis (MASH) and steatotic liver disease (MASLD). Glucagon receptor activation in hepatocytes:
- Increases hepatic fatty acid beta-oxidation
- Promotes amino acid catabolism and ureagenesis
- Stimulates autophagy and lipophagy
- Reduces hepatic de novo lipogenesis
These effects, combined with GLP-1R-mediated weight loss and anti-inflammatory actions, produce liver fat reduction superior to caloric restriction alone. The survodutide MASH trials showed 86% liver fat reduction and significant improvements in NASH activity scores and fibrosis staging, validating the dual agonist concept for liver disease Sanyal et al. (2024).
OXM in Post-Bariatric Physiology
Postprandial OXM levels are dramatically elevated after Roux-en-Y gastric bypass and sleeve gastrectomy, alongside elevations in GLP-1 and PYY. The exaggerated OXM response may contribute to the enhanced energy expenditure observed after bariatric surgery — an effect not fully explained by GLP-1 or PYY alone Laferrere et al. (2010). OXM elevation may also explain the superior liver fat resolution observed after bariatric surgery compared to equivalent weight loss achieved by lifestyle intervention.
Designed Dual Agonists — From OXM to Drug Candidates
OXM's pharmacology directly inspired the design of optimized dual GLP-1R/GCGR agonists that overcome its short half-life and low receptor potency:
- Cotadutide (MEDI0382): Acylated dual agonist with balanced GLP-1R/GCGR activity. Phase 2b results in type 2 diabetes showed 5.4% body weight loss at 49 weeks, superior liver fat reduction versus liraglutide, and improvements in NASH biomarkers Parker VER et al. (2020).
- Survodutide (BI 456906): Phase 2 trials demonstrated 18.7% body weight reduction at the highest dose at 46 weeks, with 83% of participants achieving at least 5% weight loss. Liver fat reduced by up to 86% in MASH patients, positioning survodutide as a leading candidate for metabolic liver disease Rosenstock et al. (2024).
- Pemvidutide (ALT-801): GLP-1R/GCGR dual agonist with 10.7% body weight loss at 48 weeks in phase 2, with preferential reduction of liver and visceral fat.
- Retatrutide (LY3437943): Triple GLP-1R/GIPR/GCGR agonist that adds GIP receptor agonism. Phase 2 results: 24.2% body weight loss at 48 weeks at the highest dose — the greatest reported for any anti-obesity peptide. The GCGR component (inherited from OXM's concept) contributed to energy expenditure and liver fat reduction Jastreboff et al. (2023).
Safety Profile
OXM has been administered to humans in IV infusion and subcutaneous injection studies with a favorable safety profile:
- Nausea: The most common adverse effect, occurring in approximately 10% of subcutaneous injections. Dose-dependent and typically mild and transient. Mediated by GLP-1R activation. Generally less severe than with equianorexigenic doses of GLP-1R agonists, possibly due to OXM's lower GLP-1R potency.
- Injection site reactions: Mild erythema at subcutaneous injection sites. Transient and self-resolving.
- Glycemic effects: No significant hypoglycemia observed. The GCGR-mediated hepatic glucose output partially counterbalances GLP-1R-mediated insulin secretion, producing a neutral glycemic profile in normoglycemic individuals.
- Cardiovascular: No significant effects on heart rate or blood pressure at doses used in clinical studies.
- Hepatic aminotransferases: Designed dual agonists with stronger GCGR activation have shown mild, transient ALT/AST elevations in some trials. Not observed with native OXM at research doses.
- Short half-life: The ~12-minute half-life limits the duration of any adverse effects but also limits therapeutic utility.
- No chronic human data: Long-term safety of sustained OXM exposure is unknown. Preclinical chronic dosing studies with OXM analogs have not revealed unexpected toxicity.
- Theoretical concerns: Chronic GCGR activation could theoretically promote hepatic glucose output (hyperglycemia risk in diabetes) and alpha-cell hyperplasia. These concerns are mitigated by balanced GLP-1R co-agonism and have not been observed clinically with dual agonists at therapeutic doses.
Pharmacokinetic Profile
Oxyntomodulin (OXM) — Pharmacokinetic Curve
IV infusion, subcutaneous injection (research)Quick Start
- Route
- IV infusion, subcutaneous injection (research)
Molecular Structure
- Formula
- C₁₈₆H₂₉₆N₅₆O₅₉S
Research Indications
Obesity
Human studies show 19% reduction in acute food intake and 2.8 kg weight loss over 4 weeks with thrice-daily subcutaneous injection. Dual GLP-1/glucagon receptor agonism promotes satiety and increases energy expenditure.
Clinical trials demonstrate significant appetite suppression in overweight and obese subjects through central satiety signaling and delayed gastric emptying.
Metabolic
Single-dose studies show improved insulin secretion rate and glucose metabolism comparable to GLP-1 analogs. OXM secretion is impaired in T2D and dramatically increased after gastric bypass.
OXM-based GLP-1/glucagon dual agonists (cotadutide, SAR425899) in Phase 1-2 trials show HbA1c reduction up to 0.75% and weight loss up to 5 kg. Represents a promising next-generation incretin approach.
Research Protocols
subcutaneous Injection
Subcutaneous OXM for Obesity — 4-Week Trial The landmark subcutaneous OXM trial by Wynne et al. showed that 4 weeks of subcutaneous OXM increased total energy expenditure by approximately 26%, a finding subsequently confirmed in acute infusion studies.
intravenous Injection
Research Weight Loss in Humans — IV Infusion Studies The initial human weight loss data came from intravenous infusion studies at Imperial College London.
Interactions
Peptide Interactions
Postprandial OXM levels are dramatically elevated after Roux-en-Y gastric bypass and sleeve gastrectomy, alongside elevations in GLP-1 and PYY.
The survodutide MASH trials showed 86% liver fat reduction and significant improvements in NASH activity scores and fibrosis staging, validating the dual agonist concept for liver disease [Sanyal et al.
Direct comparisons between OXM and GLP-1 administration have illuminated the unique value of dual agonism: - Appetite suppression: Comparable between OXM and GLP-1 at equianorexigenic doses. - Energy expenditure: Increased by OXM but not by GLP-1 alone. This is the critical differentiator. - Body...
What to Expect
What to Expect
Rapid onset expected; half-life of ~12 minutes (plasma) indicates fast-acting pharmacokinetics
Postprandial OXM levels rise within 15–30 minutes of eating, peak at approximately 30–60 minutes, and return to baseline within 3–4 hours.
No tachyphylaxis: The appetite-suppressive effect was maintained throughout the 4-week treatment period.
Phase 2b results in type 2 diabetes showed 5.4% body weight loss at 49 weeks, superior liver fat reduction versus liraglutide, and improvements in...
Continued use as directed
Quality Indicators
What to look for
- Well-established safety profile
- Extensive peer-reviewed research base
Caution
- Short half-life may require frequent dosing
- No long-term safety data available
- Injection site reactions reported
Frequently Asked Questions
References (17)
- [4]Zhu L, Tamvakopoulos C, Bhatt RS, et al The role of dipeptidyl peptidase IV in the cleavage of glucagon family peptides J Biol Chem (2003)
- [1]Bataille D, Tatemoto K, Gespach C, et al Isolation of glucagon-37 (bioactive enteroglucagon/oxyntomodulin) from porcine jejuno-ileum FEBS Lett (1981)
- [2]Le Quellec A, Kervran A, Blache P, et al Oxyntomodulin-like immunoreactivity: diurnal profile of a new potential enterogastrone J Clin Endocrinol Metab (1992)
- [3]Cohen MA, Ellis SM, Le Roux CW, et al Oxyntomodulin suppresses appetite and reduces food intake in humans J Clin Endocrinol Metab (2003)
- [5]Baggio LL, Huang Q, Brown TJ, Drucker DJ Oxyntomodulin and glucagon-like peptide-1 differentially regulate murine food intake and energy expenditure Gastroenterology (2004)
- [6]Wynne K, Park AJ, Small CJ, et al Subcutaneous oxyntomodulin reduces body weight in overweight and obese subjects: a double-blind, randomized, controlled trial Diabetes (2005)
- [7]Wynne K, Park AJ, Small CJ, et al Oxyntomodulin increases energy expenditure in addition to decreasing energy intake in overweight and obese humans: a randomised controlled trial Int J Obes (2006)
- [8]Jorgensen R, Kubale V, Vrecl M, et al Oxyntomodulin differentially affects glucagon-like peptide-1 receptor beta-arrestin recruitment and signaling through Galpha(s) J Pharmacol Exp Ther (2007)
- [9]Laferrere B, Heshka S, Wang K, et al Incretin levels and effect are markedly enhanced 1 month after Roux-en-Y gastric bypass surgery in obese patients with type 2 diabetes Diabetes Care (2010)
- [10]Kosinski JR, Hubert J, Carrington PE, et al The glucagon receptor is involved in mediating the body weight-lowering effects of oxyntomodulin Obesity (2012)
- [11]Tan TM, Field BCT, McCullough KA, et al Coadministration of glucagon-like peptide-1 during glucagon infusion in humans results in increased energy expenditure and amelioration of hyperglycemia Diabetes (2017)
- [13]Jastreboff AM, Kaplan LM, Frias JP, et al Triple-hormone-receptor agonist retatrutide for obesity — a phase 2 trial N Engl J Med (2023)
- [15]Sanyal AJ, Bedossa P, Engel SS, et al Survodutide for MASH and fibrosis: phase 2 histological trial N Engl J Med (2024)
- [14]
- [12]Parker VER, Robertson D, Wang T, et al Efficacy, safety, and mechanistic insights of cotadutide, a dual receptor GLP-1R/GCGR agonist J Clin Endocrinol Metab (2020)
- [16]Sánchez-Garrido MA et al — Unimolecular polypharmacology for metabolic disease: from glucagon to multi-agonists Nat Rev Endocrinol (2022)
- [17]Tan T et al — Gut hormone combination therapy (GLP-1, OXM, PYY) for obesity: proof of concept Cell Metab (2022)
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