Animal only
This paper describes the preclinical pharmacological profiling and biomarker-guided selection process used to identify survodutide (BI 456906) as a clinical development candidate from a library of 19 dual glucagon receptor (GCGR)/GLP-1R agonists. Researchers assessed receptor potency using cAMP assays in CHO-K1 cells expressing human GCGR and GLP-1R, as well as in insulinoma (MIN6) cells and rat primary hepatocytes for endogenous receptor activity. In vivo target engagement was evaluated in lean mice using oral glucose tolerance tests (GLP-1R biomarker) and plasma FGF21 and liver NNMT mRNA expression (GCGR biomarkers). Efficacy was further tested in diet-induced obese (DIO) mice for body weight reduction and in diabetic db/db mice for glucose lowering. A strong correlation was found between in vitro and in vivo GCGR and GLP-1R biomarkers, enabling candidate ranking. Survodutide demonstrated balanced dual agonism, producing greater body weight reduction than selective GLP-1R agonists while maintaining comparable antidiabetic effects. Key limitations include that all efficacy data are from rodent models, and human pharmacological profiling is not reported in this paper. Survodutide is now in Phase 3 clinical trials for obesity.
Diabetes, obesity & metabolism · Apr 2024DOI ↗ Animal only
This rat study investigated whether larazotide acetate (LA), a tight junction regulator that blocks zonulin receptors in the intestinal epithelium, could reduce intestinal barrier dysfunction and bacterial translocation in an experimentally induced acute pancreatitis (AP) model. Thirty-two male Sprague-Dawley rats were divided into four groups (control, larazotide-only, AP, and AP + larazotide). AP was induced via intraperitoneal L-Arginine injections, and LA was administered orally for seven days prior to AP induction. Intestinal permeability was assessed using FITC-Dextran, bacterial translocation was evaluated by culturing samples from liver, mesentery, and spleen, and intestinal histopathology including zonulin-1 (ZO-1) immunoreactivity was analyzed. The study found that, compared to the AP-only group, the AP + LA group showed significantly reduced intestinal damage scores, lower serum FITC-Dextran levels, decreased ZO-1 immunoreactivity, and a lower frequency of bacterial translocation. Key limitations include the exclusive use of an animal model, a small sample size, a single AP-induction method (L-Arginine), and a prophylactic rather than therapeutic administration design, which may limit clinical translatability.
Digestive diseases and sciences · Mar 2024DOI ↗ Animal only
This study investigated whether hexarelin — a synthetic peptide ligand targeting the CD36 receptor — could reduce the hyper-inflammatory response associated with severe SARS-CoV-2 infection. Using the K18-hACE2 transgenic mouse model, which expresses the human ACE2 receptor and is widely used to study COVID-19 pathology, the researchers examined how SARS-CoV-2 infection drives alveolar macrophages toward a pro-inflammatory phenotype and whether CD36 modulation could interrupt this process. The study found that CD36 signaling appears to play a regulatory role in macrophage-driven cytokine overproduction — the so-called "cytokine storm" — and that hexarelin treatment showed potential for blunting this response, thereby potentially limiting progression to acute respiratory distress syndrome (ARDS). The study is limited by its reliance on an animal model, meaning results may not translate directly to human patients. The transgenic mouse system, while a useful proxy for human COVID-19, does not fully recapitulate human immunological complexity. No clinical data in humans were presented. The authors acknowledge that ARDS from SARS-CoV-2 remains an unmet therapeutic need and position hexarelin as a candidate for further investigation.
Frontiers in pharmacology · Feb 2024DOI ↗ Animal only
This animal study investigated how the melanocortin receptor agonist Melanotan II (MTII) affects brain activity in prairie voles, with a focus on whether its effects depend on social context and the oxytocin system. Researchers administered MTII to male and female prairie voles either before social interactions or in non-social conditions, then used Fos expression (a marker of neuronal activation) to map brain activity. In non-social contexts, MTII activated only the hypothalamic paraventricular nucleus (PVN), the brain's primary site of oxytocin production. However, when MTII was given before social interactions, it selectively increased oxytocin-dependent activation in the nucleus accumbens — a region critical for social learning and reward. The authors propose this mechanism may explain how MTII accelerates partner preference formation (a model of social bonding) seen in earlier studies. The study frames these findings as supportive of a treatment model where endogenous oxytocin is pharmacologically stimulated during behavioral therapy, rather than via chronic exogenous oxytocin supplementation. Limitations include the use of a single animal species, an animal-only design, and the inherent challenges of translating prairie vole social bonding models to human psychiatric conditions such as autism.
Neuropharmacology · Jan 2024DOI ↗ Animal only
This preclinical study investigated SLU-PP-332, a synthetic agonist targeting estrogen-related receptors (ERRα, ERRβ, and ERRγ), as a potential pharmacological "exercise mimetic" for treating obesity and metabolic syndrome. Researchers administered the compound to two mouse models — diet-induced obese mice and genetically obese (ob/ob) mice — and measured a range of metabolic outcomes. The study found that SLU-PP-332 administration was associated with increased whole-body energy expenditure and enhanced fatty acid oxidation, effects the authors liken to those induced by aerobic exercise. These changes were accompanied by reductions in fat mass accumulation. The compound also appeared to improve insulin sensitivity in the metabolic syndrome models. The study's primary limitation is that all experiments were conducted exclusively in mouse models, meaning the findings cannot be directly extrapolated to humans. Differences in ERR biology, pharmacokinetics, and disease physiology between rodents and humans represent significant translational barriers. The authors conclude that pharmacological ERR activation warrants further investigation as a potential strategy for metabolic disease treatment.
The Journal of pharmacology and experimental therapeutics · Jan 2024DOI ↗ Animal only
This study investigated whether activating estrogen-related receptors (ERRα and ERRγ) — key regulators of cardiac metabolism — could treat heart failure (HF). Researchers designed two novel pan-ERR agonist compounds, SLU-PP-332 and SLU-PP-915, using structure-based drug design, and tested them in a mouse model of pressure overload-induced HF. Both compounds significantly improved ejection fraction, reduced cardiac fibrosis, and increased survival in mice without causing additional cardiac hypertrophy. Multi-omics analyses (RNA sequencing and metabolomics) revealed that ERR agonists broadly activated metabolic gene programs — particularly those governing fatty acid oxidation and mitochondrial function — and substantially normalized disrupted metabolic profiles in failing hearts. In vitro and in vivo genetic dependency experiments identified ERRγ as the primary mediator of these cardioprotective effects and confirmed target specificity. The study also found that ERR agonism downregulated cell cycle and developmental pathways, partly via the transcription factor E2F1. Limitations include that all in vivo work was conducted in mice, and no human data were presented. The authors conclude that ERR agonists represent a promising pharmacologic strategy for HF, warranting further development.
Circulation · Nov 2023DOI ↗ Animal only
This mouse study investigated the role of estrogen-related receptors (ERRs) in age-related kidney decline, focusing on mitochondrial dysfunction and inflammation as key mechanisms. The researchers first observed that ERR expression was reduced in both aging human and mouse kidneys, and that lifelong caloric restriction (CR) preserved ERR levels in mice. They then treated 21-month-old mice (equivalent to elderly) for 8 weeks with a pan-ERR agonist (SLU-PP-332) or for 3 weeks with a STING pathway inhibitor (C-176). The ERR agonist treatment reversed age-associated increases in albuminuria (a marker of kidney damage), podocyte loss, mitochondrial dysfunction, and inflammatory cytokines, acting through the cGAS-STING and STAT3 signaling pathways — effects resembling those of caloric restriction. STING inhibition reduced inflammatory cytokines and the senescence marker p21, but also unexpectedly restored mitochondrial pathway components (PGC-1α, ERRα, mitochondrial complexes, MCAD). The study identifies ERRs as potential CR mimetics and highlights the cGAS-STING pathway as a link between mitochondrial dysfunction and renal inflammation in aging. Key limitations include reliance on animal models, short treatment durations, and the absence of human interventional data.
The American journal of pathology · Sep 2023DOI ↗ Animal only
This study investigated whether the growth hormone-releasing peptide Hexarelin could protect against ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) and explored its molecular mechanisms. Using a rat I/R model, animals were pretreated with Hexarelin for seven days before injury induction. Researchers assessed kidney function (serum creatinine), histology (tubular necrosis and dilation), and apoptosis markers. In vitro, a hypoxia/reoxygenation (H/R) model in human kidney tubular (HK-2) cells was used to complement findings. The study reports that Hexarelin pretreatment reduced pathological kidney changes, improved renal function, and suppressed apoptosis, as evidenced by downregulation of pro-apoptotic proteins (Caspase-3, Bax, Bad) and upregulation of anti-apoptotic Bcl-2. Gene Set Enrichment Analysis (GSEA) highlighted the apoptosis pathway's role in I/R-AKI. Molecular docking suggested Hexarelin binds MDM2, a negative regulator of p53, and both MDM2 and p53 expression were suppressed by Hexarelin in vivo and in vitro. Key limitations include exclusive use of animal and cell models with no human data, a relatively narrow mechanistic focus, and reliance on computational docking without direct protein-interaction validation.
European journal of medical research · Sep 2023DOI ↗ Animal only
This study investigated whether a short-term high-fat (HF) diet could impair neurobehavioral outcomes in zebrafish (Danio rerio) and whether treatment with Melanotan-II (MT-II), a melanotropin receptor agonist, could reverse those effects. Zebrafish were fed an HF diet for approximately three weeks — roughly 1% of their lifespan — and then assessed for recognition memory, anxiety levels, and exploratory behavior. The researchers found that zebrafish on the HF diet showed measurable impairments in recognition memory, elevated anxiety, and reduced exploratory behavior compared to control-diet animals. Notably, HF-diet zebrafish that also received MT-II treatment demonstrated memory, anxiety, and exploratory behavior comparable to the control group, suggesting a reversal of HF diet-induced changes. The authors describe this as the first study demonstrating MT-II's ability to reverse short-term HF diet-induced neurobehavioral abnormalities. Key limitations include the use of a non-mammalian animal model (zebrafish), which limits direct translation to human neurology, and the absence of mechanistic data clarifying how MT-II acts on the relevant brain pathways. No human or clinical data are presented.
Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie · Jul 2023DOI ↗ Animal only
This study identified SLU-PP-332, a synthetic pan-agonist targeting all three estrogen receptor-related receptors (ERRα, ERRβ, and ERRγ), with the highest potency for ERRα. Researchers first characterized the compound's pharmacokinetic properties to confirm it could be used as an in vivo tool. In cultured skeletal muscle cells, SLU-PP-332 was shown to increase mitochondrial function and cellular respiration. In mouse experiments, administration of SLU-PP-332 increased type IIa oxidative skeletal muscle fibers and enhanced exercise endurance. The study also demonstrated that the compound induced a genetic program closely resembling an acute aerobic exercise response, and that this effect was ERRα-dependent — mice lacking ERRα did not show the same enhancement in exercise endurance. The authors propose that targeting ERRα may be a viable strategy for developing exercise mimetics useful in treating metabolic disorders and age-related muscle decline. Key limitations include that all in vivo experiments were conducted in mice, no human data were generated, and the long-term safety and efficacy of SLU-PP-332 remain untested.
ACS chemical biology · Mar 2023DOI ↗ Animal only
This animal study investigated how the central nervous system melanocortin (CNS-MC) system influences feed intake, metabolic hormones, and insulin sensitivity in sheep. Ewes were surgically fitted with intracerebroventricular (ICV) cannulas and infused with artificial cerebrospinal fluid (aCSF), the α-MSH analog melanotan-I (MTI), or agouti-related peptide (AGRP) directly into the third ventricle. The study found that ICV MTI infusion significantly reduced voluntary feed intake, while AGRP infusion modestly increased it. MTI also elevated plasma triiodothyronine and thyroxine independently of changes in food intake, suggesting a direct central effect on thyroid hormone regulation. Notably, MTI did not affect plasma glucose, insulin, or cortisol under normal feeding conditions. However, during hyperinsulinemic-euglycemic clamp experiments in energy-restricted ewes, MTI impaired insulin's ability to suppress endogenous glucose production, indicating reduced hepatic insulin sensitivity. MTI also tended to lower plasma leptin in a feeding-level-dependent manner, with no effect on adiponectin. AGRP infusion did not significantly alter any measured plasma metabolic variables. The authors concluded that the CNS-MC system plays a role in regulating metabolic efficiency and peripheral insulin action in ruminants. Limitations include small sample sizes, a single non-human species, and the invasive ICV delivery route.
Journal of animal science · Jan 2023DOI ↗ Animal only
This preclinical study investigated the neurological mechanisms by which obesity medications suppress food intake, focusing on proglucagon (PPG)-expressing neurons in the nucleus of the solitary tract (PPG-NTS). Using single-nucleus RNA sequencing and histochemistry, researchers characterized gene expression profiles of PPG-NTS neurons in rodents, finding that serotonin 2C receptors (5-HT2CR) — the target of lorcaserin — were widely expressed in these neurons, while GLP-1 receptors and melanocortin-4 receptors were not. Lorcaserin was found to significantly activate PPG-NTS neurons. When PPG-NTS neurons were virally ablated, lorcaserin lost its ability to suppress food intake, whereas the MC4R agonist melanotan-II retained its effect, confirming the functional role of 5-HT2CR expression in these neurons. Additionally, combining lorcaserin with GLP-1R agonists liraglutide or exendin-4 produced greater food intake reduction than either drug alone. The study concludes that PPG-NTS neurons are a necessary mechanistic link for lorcaserin's appetite-suppressing effects and suggests that combining 5-HT2CR and GLP-1R agonists may enhance therapeutic outcomes. Key limitations include that all experiments were conducted in animals, and translational relevance to humans remains to be established.
Molecular metabolism · Dec 2022DOI ↗ Animal only
This study investigated whether MK-0677 (ibutamoren), an orally active, non-peptide growth hormone secretagogue that activates the ghrelin receptor, could be detected in equine hair following oral administration to a single Thoroughbred racehorse. Researchers extracted MK-0677 and its O-dealkylated metabolite from mane and tail hair samples using an established method for prohibited substances, then analyzed them by liquid chromatography tandem mass spectrometry (LC-MS/MS). The study found that MK-0677 was detectable in all collected hair samples, with a detection window of up to 209 days in mane hair and 358 days in tail hair. A follow-up wash procedure confirmed true internal incorporation of the compound rather than mere surface contamination. Wash criteria analyses suggested that hair samples collected at later time points (≥52 days post-administration) reflected internal incorporation via the bloodstream, while the earliest sample (2 days) showed a combination of internal incorporation and external deposition via sweat and sebum. A key limitation is that the study involved only one horse, restricting generalizability. The findings are relevant to anti-doping efforts in equine sports, highlighting the long detection window MK-0677 may afford in hair matrices.
Drug testing and analysis · Dec 2022DOI ↗ Animal onlyPreprint
This study investigated whether a synthetic small-molecule agonist of the orphan nuclear receptor ERRα (estrogen receptor-related receptor alpha), called SLU-PP-332, could mimic the genetic and physiological effects of aerobic exercise in skeletal muscle. Researchers first used cell-based assays to confirm that SLU-PP-332 activates ERRα and found it triggered an acute aerobic exercise-associated gene expression program in skeletal muscle cells in an ERRα-dependent manner. In cell culture experiments, the compound increased mitochondrial function and cellular respiration. When administered to mice, SLU-PP-332 was reported to increase the proportion of type IIa oxidative skeletal muscle fibers and improve exercise endurance capacity. The authors propose that ERRα is a viable pharmacological target for developing "exercise mimetic" compounds, which could potentially help treat metabolic disorders and age-related muscle decline. Key limitations include the preclinical (mouse and cell-based) nature of all findings, the absence of human data, and the preprint status of the paper, meaning it had not yet undergone formal peer review at the time of reporting. No conclusions about human efficacy or safety can be drawn from this work alone.
Unknown journal · Oct 2022DOI ↗ Animal only
This study investigated the role of melanocortin signaling in the nucleus accumbens (NAcc) on food intake and motivation to eat in mice. Male C57BL/6J mice received bilateral microinjections of melanotan-II (MT-II), a melanocortin receptor 3/4 agonist, directly into the NAcc, and researchers measured effects on food consumption and operant responding for food. The study found that MT-II microinjected into the NAcc significantly reduced both the amount of food consumed (measured in home cage settings) and appetitive responding (measured by operant self-administration tasks requiring effort to obtain food). Importantly, these effects appeared to occur without inducing conditioned taste avoidance—suggesting the reductions were not due to nausea or aversion—and without measurable changes in metabolic rate. The authors concluded that melanocortin signaling in the NAcc may selectively regulate appetite and satiety independent of metabolism or aversive side effects. Key limitations include that this was an animal-only study conducted exclusively in male mice of a single inbred strain, limiting generalizability to other sexes, species, or humans. The microinjection approach is also not clinically translatable in its current form.
Neuropeptides · Sep 2022DOI ↗ Animal only
This study investigated the metabolic profile of ibutamoren (MK-0677) — an orally active, non-peptide growth hormone secretagogue — in thoroughbred horses, with the goal of supporting anti-doping detection efforts. Researchers administered ibutamoren orally to horses and collected biological samples, which were analyzed using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) to identify and characterize the parent compound and its metabolites. The study identified 22 metabolites in total: 17 Phase I metabolites (including mono- and di-hydroxylated forms, dissociated side chain products such as a benzyl group and 2-amino-2-methylpropanamide, and hydrogenated metabolites) and 5 Phase II metabolites (glucuronic acid conjugates; no sulfate conjugates were detected). The study reported that major metabolites were detectable up to 96 hours post-administration, while the parent compound ibutamoren itself persisted for up to 72 hours. The authors conclude that these findings provide a useful metabolic reference framework to help detect illicit use of ibutamoren in competitive equine sports. Key limitations include the use of an animal model (horses only), meaning findings may not directly translate to human metabolism or human anti-doping contexts.
Rapid communications in mass spectrometry : RCM · Sep 2022DOI ↗ Animal only
This study investigated the metabolism of MK-0677 (ibutamoren mesylate), an orally active non-peptide growth hormone secretagogue, in horses to support equine doping control efforts. Researchers conducted both in vitro incubations and in vivo oral administration to two Thoroughbred racehorses, then used liquid chromatography high-resolution mass spectrometry (LC-HRMS) and LC-tandem mass spectrometry to identify and profile metabolites in urine and plasma. Fourteen phase I metabolites were identified in vitro; 13 were subsequently detected in post-administration urine and nine in plasma, along with the parent compound in both matrices. The study found that an O-dealkylated metabolite of MK-0677 showed the longest detection window in both urine and plasma, making it the recommended analytical target for doping control laboratories. Both MK-0677 and this key metabolite were found to be excreted predominantly in unconjugated form. Limitations include the very small sample size (n=2 horses) and the fact that findings are restricted to equine species, meaning results cannot be directly extrapolated to human metabolism or doping detection in human sport.
Drug testing and analysis · Mar 2022DOI ↗ Animal onlyPreprint
This study investigated whether pharmacological activation of estrogen-related receptors (ERRα and ERRγ) could serve as a therapeutic strategy for heart failure. Using structure-based drug design, researchers developed two novel synthetic pan-ERR agonists — SLU-PP-332 and SLU-PP-915 — and tested them in a mouse model of pressure overload-induced heart failure. Both compounds significantly improved cardiac ejection fraction and reduced fibrosis without affecting cardiac hypertrophy. Mechanistic analyses revealed that ERR agonists broadly activated metabolic gene programs, particularly those governing fatty acid oxidation and mitochondrial function, with ERRγ identified as the primary mediator. Metabolomics profiling showed that SLU-PP-915 normalized disrupted fatty acid/lipid and TCA cycle/oxidative phosphorylation metabolite profiles in failing mouse hearts. The agonists also induced autophagy in cardiomyocytes and downregulated cell cycle and developmental pathways, partly via suppression of the transcription factor E2F1. The study is limited to preclinical mouse models with no human data, and the long-term safety profile of these compounds remains uncharacterized. The authors conclude that these findings provide direct pharmacological evidence supporting further development of ERR agonists as heart failure therapeutics.
Unknown journal · Feb 2022DOI ↗ Animal only
This animal study investigated whether treatment with a nicotinamide N-methyltransferase inhibitor (NNMTi; 5-amino-1-methylquinolinium) combined with a low-fat diet (LD) switch produced distinct gut microbiome changes in diet-induced obese (DIO) mice, compared to mice maintained on a high-fat Western diet, switched to LD alone, or kept as lean controls. Researchers analyzed cecal microbiome profiles using amplicon sequence variant (ASV) sequencing across these groups. The study found that diet switch (regardless of NNMTi treatment) drove several microbiome differences at the genus and phylum levels relative to controls, while differences between lean and obese controls were minimal, suggesting adiposity alone had limited microbiome impact in this model. Alpha diversity did not significantly differ between groups, but beta diversity analyses indicated within-group similarity. K-means clustering revealed that NNMTi-treated LD-switched mice had a distinct microbiome pattern, characterized by decreased Erysipelatoclostridium and increased Lactobacillus—genera associated with metabolic regulation and body weight. Parasutterella abundance, elevated in both LD-switched groups, significantly correlated with several adipose tissue metabolites. The authors acknowledge this is a foundational, exploratory study in mice, limiting direct translation to human metabolic disease.
Scientific reports · Jan 2022DOI ↗ Animal only
This study investigated whether hexarelin, a synthetic growth hormone-releasing peptide, could reduce the development of abdominal aortic aneurysm (AAA) using an elastase-induced mouse model. Mice received hexarelin injections twice daily, and outcomes were assessed via echocardiography, in situ imaging, histology, and molecular analyses. The study found that hexarelin-treated mice showed reduced infrarenal aortic diameter and improved elastin integrity compared to untreated controls. At the cellular level, hexarelin appeared to preserve smooth muscle cell (SMC) contractile phenotype, evidenced by increased α-SMA expression and decreased MMP2. Additionally, hexarelin was associated with reduced inflammatory cell infiltration, suppression of NLRP3 inflammasome activation, lower IL-18 production, and inhibition of the NF-κB signaling pathway. The authors concluded that hexarelin attenuates AAA development by targeting SMC phenotype switching and NF-κB-mediated inflammation. Key limitations include the exclusive use of an animal model, meaning findings have not been validated in humans, and the mechanistic conclusions are based on a single preclinical model that may not fully replicate human AAA pathophysiology.
Microvascular research · Nov 2021DOI ↗