Pathogenesis, Therapeutic Targets, and Drug Development for Metabolic Dysfunction-Associated Steatohepatitis (MASH/NASH)

Metabolic dysfunction-associated steatohepatitis is jointly driven by hepatic fat accumulation, lipotoxicity, insulin resistance, inflammation, and fibrosis. Targeting lipid metabolism, nuclear receptors, incretin pathways, and FGF signaling has become a major direction in drug development.

Keywords: MASH; NASH; MASLD; lipotoxicity; insulin resistance; hepatic fibrosis; THR-β; FXR; GLP-1R; FGF21; drug development

1 Disease Spectrum and Pathological Characteristics of MASH/NASH

1.1 Definitions of MASLD and MASH

Fatty liver diseases are now classified under the framework of steatotic liver disease (SLD). Metabolic dysfunction-associated steatotic liver disease (MASLD) refers to hepatic steatosis accompanied by at least one cardiometabolic risk factor. When hepatocellular ballooning and lobular inflammation develop on the basis of steatosis, the condition can be diagnosed as metabolic dysfunction-associated steatohepatitis (MASH). MASH is the updated term for nonalcoholic steatohepatitis (NASH), and the two terms generally refer to the same pathological entity in previous research and drug-development programs.

1.2 Progression From Simple Steatosis to Steatohepatitis

MASLD may present as relatively stable simple hepatic steatosis or progress to MASH accompanied by inflammation and hepatocellular injury. Disease progression is not determined solely by intrahepatic triglyceride content but is jointly influenced by free fatty acid influx, de novo lipogenesis, fatty acid oxidation, lipoprotein export, accumulation of lipotoxic molecules, and the host genetic background.

1.3 Histopathological Characteristics of MASH

The main histological features of MASH include macrovesicular hepatic steatosis, lobular inflammation, and hepatocellular ballooning, with variable degrees of fibrosis. Hepatocellular ballooning reflects cytoskeletal disruption, organelle stress, and metabolic dysfunction, whereas lobular inflammation mainly involves recruitment of Kupffer cells, monocytes, and other immune cells.

1.4 Staging of Hepatic Fibrosis

MASH-associated fibrosis generally begins in the centrilobular and perisinusoidal regions and may gradually progress to portal fibrosis, bridging fibrosis, and cirrhosis. F0 indicates no fibrosis, F1 mild fibrosis, F2 moderate fibrosis, F3 bridging fibrosis, and F4 cirrhosis. The degree of fibrosis is more strongly associated with the risk of adverse liver-related outcomes than inflammation or steatosis alone.

1.5 Disease Heterogeneity

MASH can occur in patients with obesity and type 2 diabetes but can also develop in individuals of normal body weight who have visceral fat accumulation, sarcopenia, or genetic susceptibility. Genetic variants in PNPLA3, TM6SF2, MBOAT7, GCKR, and other genes can affect lipid-droplet remodeling, lipoprotein export, and intrahepatic lipid composition, resulting in substantially different rates of disease progression under similar metabolic conditions.

1.6 Extrahepatic Complications

In addition to risks of cirrhosis, hepatic decompensation, and hepatocellular carcinoma, patients with MASH frequently have cardiovascular disease, type 2 diabetes, chronic kidney disease, and obstructive sleep apnea. Treatment should evaluate hepatic pathology, body weight, blood glucose, blood lipids, and cardiovascular risk rather than focusing only on reducing hepatic fat content.

Table 1 Stages of MASH Progression and Major Pathological Characteristics

Disease Stage	Major Pathological Characteristics	Major Evaluation Indicators	Major Risks
Simple steatosis	Increased lipid droplets in hepatocytes without marked ballooning or inflammation	Hepatic fat content and liver enzymes	May remain stable for a prolonged period or progress
Early MASH	Steatosis, lobular inflammation, and ballooning	NAS and markers of inflammation and cellular injury	Progression toward fibrosis
F1 fibrosis	Mild perisinusoidal or portal fibrosis	Histology and elastography	Still highly reversible
F2 fibrosis	Coexisting perisinusoidal and portal fibrosis	Histology, ELF, and MRE	Increased risk of liver-related outcomes
F3 fibrosis	Bridging fibrosis	Histology, MRE, and serum fibrosis markers	High risk of progression to cirrhosis
F4 fibrosis	Cirrhosis and nodule formation	Portal hypertension, liver function, and imaging	Decompensation, hepatocellular carcinoma, and death

2 Mechanisms of Hepatic Lipid Accumulation and Lipotoxic Injury

2.1 Major Sources of Hepatic Fatty Acids

Hepatic fatty acids are mainly derived from free fatty acids released by adipose tissue, hepatic de novo lipogenesis, and dietary lipids. Insulin resistance weakens the inhibitory effect of insulin on adipose-tissue lipolysis, allowing large quantities of free fatty acids to enter the liver. High glucose and fructose intake can enhance hepatic de novo lipogenesis through ChREBP and SREBP-1c.

2.2 Abnormal De Novo Lipogenesis

Acetyl-CoA carboxylase (ACC) converts acetyl-CoA into malonyl-CoA, fatty acid synthase (FASN) further synthesizes long-chain fatty acids, and stearoyl-CoA desaturase 1 (SCD1) generates monounsaturated fatty acids. Sustained activation of these enzymes increases the hepatic fatty acid supply. Malonyl-CoA also inhibits CPT1A-mediated fatty acid entry into mitochondria, creating a metabolic state characterized by increased synthesis and restricted oxidation.

2.3 Dual Effects of Triglyceride Storage

Hepatocytes can esterify fatty acids into triglycerides through DGAT1 and DGAT2 and store them in lipid droplets. Moderate triglyceride synthesis can sequester free fatty acids and reduce immediate toxicity. However, sustained expansion of lipid droplets causes hepatic steatosis and provides a continuing substrate source for lipid peroxidation and formation of lipotoxic molecules.

 

 

Figure 1. Fatty acid synthesis, β-oxidation, and triglyceride storage pathways in hepatocytes

2.4 Lipotoxic Lipid Molecules

Diacylglycerols, ceramides, free cholesterol, lysophospholipids, and oxidized lipids are more cytotoxic than neutral triglycerides. Diacylglycerols can activate PKCε and inhibit hepatic insulin signaling, ceramides can disrupt AKT and mitochondrial function, and free cholesterol can destabilize mitochondrial membranes, the endoplasmic reticulum, and lysosomes.

2.5 Mitochondrial Overload and Oxidative Stress

In the early stages of hepatic fat accumulation, mitochondrial β-oxidation may increase compensatorily. Long-term fatty acid overload, however, causes pressure on the electron transport chain, reactive oxygen species generation, and reduced ATP-synthesis efficiency. Fatty acid oxidation in peroxisomes and microsomes also increases reactive oxygen species, further aggravating lipid peroxidation, protein oxidation, and mitochondrial DNA damage.

2.6 Endoplasmic Reticulum Stress and the Unfolded Protein Response

Saturated fatty acids, cholesterol, and oxidative stress can disrupt the endoplasmic reticulum membrane environment and cause accumulation of misfolded proteins. The unfolded protein response mediated by PERK, IRE1α, and ATF6 is adaptive in the early stage, but persistent activation induces CHOP, JNK, and inflammatory signaling, promoting hepatocyte apoptosis and insulin resistance.

2.7 Lipophagy and Lysosomal Dysfunction

Lipid droplets can be delivered to lysosomes through lipophagy and degraded into fatty acids. In MASH, impaired autophagosome formation, lysosomal acidification, or lipid-droplet recognition reduces lipid-clearance capacity. Lysosomal cholesterol accumulation and increased membrane permeability can also promote inflammasome activation and cell death.

3 Insulin Resistance, Inflammatory Responses, and Progression of Hepatic Fibrosis

3.1 Hepatic and Peripheral Insulin Resistance

Skeletal muscle insulin resistance reduces glucose uptake and causes more glucose to reach the liver. Adipose-tissue insulin resistance enhances lipolysis and causes continuous free fatty acid influx into the liver. Hepatic insulin resistance prevents adequate suppression of gluconeogenesis. At the same time, lipogenic pathways may remain selectively responsive to hyperinsulinemia, resulting in simultaneous enhancement of gluconeogenesis and lipid synthesis.

3.2 Kupffer Cells and Monocyte Recruitment

Lipotoxic hepatocytes release damage-associated molecules such as ATP, mitochondrial DNA, HMGB1, and oxidized lipids, activating Kupffer cells and liver sinusoidal endothelial cells. Chemokines such as CCL2 further recruit CCR2-positive monocytes into the liver, creating an inflammatory environment that continuously produces TNF-α, IL-1β, and TGF-β.

3.3 TLR Signaling and the NLRP3 Inflammasome

Gut-derived lipopolysaccharide, fatty acids, and damage-associated molecules can activate TLR4 and downstream NF-κB signaling. Cholesterol crystals, mitochondrial reactive oxygen species, and extracellular ATP can also promote assembly of the NLRP3 inflammasome, resulting in Caspase-1 activation and maturation of IL-1β and IL-18, thereby amplifying hepatocellular injury and immune-cell recruitment.

3.4 Modes of Hepatocyte Death

Hepatocytes in MASH can undergo apoptosis, necroptosis, pyroptosis, and ferroptosis. Different forms of cell death release distinct cellular contents and lipid mediators, but all can promote macrophage activation and hepatic stellate cell recruitment. When iron loading, glutathione depletion, and peroxidation of polyunsaturated lipids increase, ferroptosis may become an important mechanism of injury.

3.5 Activation of Hepatic Stellate Cells

After exposure to TGF-β, PDGF, reactive oxygen species, apoptotic bodies, and increased matrix stiffness, quiescent hepatic stellate cells can transform into myofibroblast-like cells expressing α-smooth muscle actin. Activated hepatic stellate cells produce type I and type III collagen, fibronectin, TIMP1, and other matrix components and are the principal effector cells responsible for MASH-associated fibrosis.

3.6 TGF-β and PDGF Signaling

TGF-β promotes collagen transcription and suppresses matrix degradation through TGFBR1/2 and SMAD2/3 and is a central fibrotic signal. PDGF mainly promotes hepatic stellate cell proliferation, migration, and survival. These pathways cooperate with integrins, YAP/TAZ, LOXL2, and mechanical stress signaling, causing hepatic tissue to gradually develop a stable fibrotic network that is difficult to degrade.

3.7 Dysregulation of the Gut-Liver Axis

Disruption of the intestinal barrier, changes in microbiota composition, and abnormal bile acid metabolism can increase entry of microbial products into the portal circulation. Changes in lipopolysaccharide, ethanol, short-chain fatty acids, and secondary bile acids can affect hepatic inflammation, FXR signaling, and insulin sensitivity. However, microbiota features vary substantially among patients, and no single microbiota pattern is applicable to all patients with MASH.

4 Therapeutic Targets Related to Lipid Synthesis and Oxidative Metabolism

4.1 ACC Inhibition

Inhibition of ACC1 reduces de novo lipogenesis, whereas inhibition of ACC2 decreases malonyl-CoA-mediated suppression of CPT1A and promotes fatty acid oxidation. ACC inhibition usually reduces hepatic fat rapidly, but decreased hepatic fatty acid synthesis can trigger SREBP1 compensation and increased very-low-density lipoprotein export, resulting in elevated serum triglycerides.

4.2 FASN Inhibition

FASN catalyzes the terminal synthetic step in de novo lipogenesis. FASN inhibition reduces palmitate production and decreases diacylglycerols, ceramides, and other lipotoxic lipids. Compared with ACC inhibition, FASN inhibition has a different effect on malonyl-CoA levels and may reduce some compensatory hypertriglyceridemia. Skin, neurological, and systemic effects associated with lipid synthesis still require monitoring.

4.3 Modulation of SCD1

SCD1 catalyzes the conversion of saturated fatty acids into monounsaturated fatty acids and promotes triglyceride synthesis. SCD1 inhibition can reduce lipogenesis but may also increase saturated fatty acid-induced endoplasmic reticulum stress. Development of this target requires balancing reduced lipid-droplet formation against avoidance of saturated fatty acid toxicity.

4.4 DGAT2 Inhibition

DGAT2 mainly participates in triglyceride synthesis in hepatocytes and is tightly coupled to de novo lipogenesis. DGAT2 inhibition can reduce hepatic fat and lipoprotein output. However, excessive restriction of triglyceride storage may redirect free fatty acids toward ceramide, diacylglycerol, or other lipotoxic pathways, requiring lipidomic evaluation.

4.5 AMPK and Mitochondrial Metabolism

AMPK can inhibit ACC and SREBP-1c while promoting fatty acid oxidation, autophagy, and mitochondrial homeostasis. Activating AMPK or increasing mitochondrial oxidative capacity has the potential to reduce hepatic fat. However, increasing fatty acid oxidation without simultaneously improving electron transport chain function may aggravate oxidative stress.

4.6 PPAR-Mediated Metabolic Reprogramming

PPARα promotes fatty acid oxidation and lipoprotein metabolism, PPARδ participates in energy expenditure and insulin sensitivity, and PPARγ regulates adipose-tissue differentiation and safe lipid storage. Pan-PPAR or dual-PPAR modulation can simultaneously improve lipid metabolism, inflammation, and fibrosis but may cause weight gain, fluid retention, anemia, or other receptor subtype-related adverse effects.

5 Regulation of Bile Acid, Thyroid Hormone, and Nuclear Receptor Signaling

5.1 Bile Acids and FXR Signaling

Bile acids participate not only in lipid digestion but also serve as endogenous ligands for the farnesoid X receptor (FXR). Hepatic FXR activation suppresses bile acid synthesis and lipogenesis, whereas intestinal FXR induces FGF19 secretion and inhibits CYP7A1 through hepatic FGFR4/β-Klotho signaling. FXR agonists can improve metabolic and fibrotic signaling, but pruritus, increased low-density lipoprotein cholesterol, and disruption of bile acid homeostasis can limit the use of some agents.

5.2 Thyroid Hormone Receptor Beta

Thyroid hormone receptor beta (THR-β) is predominantly expressed in the liver and can promote fatty acid oxidation, mitochondrial biogenesis, and cholesterol metabolism while reducing hepatic fat accumulation. Selective THR-β agonists are designed to preserve hepatic metabolic effects while reducing THR-α-mediated effects on heart rate, bone, and myocardium.

5.3 Liver Selectivity of Resmetirom

Resmetirom is a liver-targeted selective THR-β agonist that enhances hepatic fatty acid oxidation and improves the atherogenic lipid profile. Its therapeutic value extends beyond reduction of hepatic fat because some patients can achieve resolution of steatohepatitis or improvement of fibrosis.

5.4 Cooperation Among PPAR Nuclear Receptors

PPARα, PPARδ, and PPARγ respectively regulate hepatic fatty acid oxidation, muscular energy utilization, adipose-tissue lipid storage, and anti-inflammatory responses. Pan-PPAR agonists can intervene in MASH through the liver, adipose tissue, and immune cells, but both efficacy and adverse effects depend on the relative degree of activation of the different receptor subtypes.

5.5 Selectivity Requirements for Nuclear Receptor Targeting

Nuclear receptors are broadly involved in normal metabolic homeostasis, and strong systemic activation may cause effects unrelated to the target organ. Drug development must simultaneously optimize receptor-subtype selectivity, hepatic exposure, tissue distribution, and the downstream gene-expression profile rather than relying solely on in vitro receptor-activation potency to define the therapeutic window.

6 Metabolic Intervention Mediated by GLP-1R, FGF19, and FGF21

6.1 GLP-1R Agonists

GLP-1R agonists reduce appetite, delay gastric emptying, promote glucose-dependent insulin secretion, and reduce body weight, thereby decreasing adipose-tissue lipolysis and hepatic fatty acid influx. Whether hepatocytes express sufficient functional GLP-1R to mediate direct pharmacological effects remains controversial. Their effects in MASH should therefore mainly be interpreted in terms of weight loss, improved insulin sensitivity, and reduced systemic metabolic burden.

6.2 Dual and Multiple Incretin-Receptor Agonism

GIPR/GLP-1R dual agonists and GLP-1R/GIPR/GCGR multi-receptor agonists can produce stronger weight loss through appetite suppression, adipose-tissue metabolic regulation, and increased energy expenditure. GCGR activation may also increase hepatic fatty acid oxidation and energy expenditure but has the potential to elevate blood glucose and must be balanced by GLP-1R and GIPR signaling.

6.3 FGF19 Signaling

FGF19 is secreted by ileal cells after FXR activation and acts on the liver through FGFR4 and β-Klotho to suppress bile acid synthesis and regulate glucose and lipid metabolism. Engineered FGF19 analogs can reduce hepatic fat and improve inflammation and fibrosis but must minimize the risk of sustained wild-type FGF19-mediated activation of FGFR4-associated proliferative signaling.

6.4 FGF21 Signaling

FGF21 acts primarily through FGFR1c/β-Klotho in adipose tissue and central metabolic networks, improving insulin sensitivity, promoting fatty acid utilization, and improving blood lipids. Long-acting FGF21 analogs can simultaneously reduce hepatic fat, triglycerides, and certain fibrosis indicators and are an important direction in MASH drug development.

6.5 Pegozafermin and Efruxifermin

Pegozafermin and Efruxifermin are both long-acting FGF21 analogs but differ in molecular engineering strategy, receptor activity, and pharmacokinetics. Pegozafermin has shown histological improvement in studies of noncirrhotic patients with F2-F3 fibrosis. Efruxifermin is also being continuously evaluated across different fibrosis stages. Disease stage, treatment duration, and baseline metabolic status can all affect actual efficacy.

6.6 Combined Intervention With Metabolic Factors

GLP-1R agonists mainly reduce energy intake and body weight, FGF21 analogs more strongly affect lipid handling, insulin sensitivity, and adipose-tissue signaling, and THR-β agonists directly enhance hepatic lipid metabolism. These mechanisms are complementary, but combination treatment requires monitoring of gastrointestinal reactions, the magnitude of weight loss, gallbladder disease, and pharmacokinetic changes.

7 Mechanisms and Clinical Translation of Approved and Investigational MASH/NASH Therapies

7.1 Resmetirom

Resmetirom selectively activates hepatic THR-β, promotes fatty acid oxidation, and improves cholesterol and lipoprotein metabolism. It can increase the proportions of patients achieving steatohepatitis resolution and fibrosis improvement and is used in noncirrhotic adults with MASH and moderate-to-advanced fibrosis.

7.2 Semaglutide

Semaglutide acts through GLP-1R signaling to reduce body weight and improve insulin resistance and cardiometabolic risk factors. It can increase the proportion of patients achieving MASH resolution and fibrosis improvement, particularly in those with obesity, type 2 diabetes, or multiple cardiometabolic risk factors.

7.3 Lanifibranor

Lanifibranor is a pan-PPAR agonist that simultaneously regulates fatty acid oxidation, adipose-tissue function, inflammation, and hepatic stellate cell activation. It has the potential to improve disease activity, steatohepatitis, and fibrosis, but adverse effects such as weight gain, edema, and anemia require monitoring.

7.4 FGF21 Analogs

FGF21 analogs can simultaneously improve hepatic fat, insulin sensitivity, triglycerides, and certain fibrosis indicators. Pegozafermin and Efruxifermin represent major development directions in this class. However, different fibrosis stages, treatment durations, and histological endpoints can produce different results, and rapid reductions in hepatic fat cannot be directly equated with improved long-term clinical outcomes.

7.5 FGF19 Analogs and FXR Agonists

Engineered FGF19 analogs and FXR agonists can suppress bile acid synthesis, reduce hepatic fat, and regulate fibrosis. Major development challenges include pruritus, increased low-density lipoprotein cholesterol, gallbladder-related reactions, and long-term FGFR4 proliferative signaling. Drug structure and receptor bias are therefore critical.

7.6 FASN, ACC, and DGAT2 Inhibitors

FASN inhibitors directly reduce de novo fatty acid synthesis, ACC inhibitors both reduce lipogenesis and promote oxidation, and DGAT2 inhibitors limit triglyceride synthesis. These agents generally reduce MRI-PDFF relatively rapidly. Whether they can sustainably improve ballooning and fibrosis depends on lipotoxic lipid shunting, compensatory changes in blood lipids, and long-term safety.

7.7 Anti-Inflammatory and Antifibrotic Drugs

Targets such as CCR2/CCR5, ASK1, TGF-β, LOXL2, and integrins can respectively interfere with inflammatory-cell recruitment, stress kinases, hepatic stellate cell activation, and matrix cross-linking. Some single-target agents failed to reproduce early results in later-stage studies, indicating that MASH fibrosis is maintained by multiple parallel pathways and that blocking a single inflammatory or matrix node may be insufficient to reverse disease.

Table 2 Major MASH Drug Directions and Their Characteristics

Drug or Class	Major Target	Major Effects	Clinical Positioning or Development Status
Resmetirom	THR-β	Enhances hepatic fatty acid oxidation and improves blood lipids	Used for noncirrhotic F2-F3 MASH
Semaglutide	GLP-1R	Promotes weight loss and improves insulin resistance and hepatic histology	Used for MASH with moderate-to-advanced fibrosis
Lanifibranor	PPARα/δ/γ	Regulates lipid metabolism, inflammation, and fibrosis	Late-stage clinical development
Pegozafermin	FGF21 pathway	Improves hepatic fat, blood lipids, and fibrosis	Late-stage clinical development
Efruxifermin	FGF21 pathway	Improves insulin sensitivity and hepatic metabolism	Late-stage clinical development
FGF19 analogs	FGFR4/β-Klotho	Suppress bile acid synthesis and improve metabolism	Clinical development
FXR agonists	FXR	Regulate bile acids, lipids, and fibrosis	Efficacy and tolerability remain under evaluation
FASN inhibitors	FASN	Reduce de novo lipogenesis and lipotoxic lipids	Clinical development
ACC inhibitors	ACC1/ACC2	Reduce lipogenesis and promote fatty acid oxidation	Require control of triglyceride elevation
DGAT2 inhibitors	DGAT2	Reduce hepatic triglyceride synthesis	Clinical development
Anti-inflammatory and antifibrotic drugs	CCR2/5, TGF-β, LOXL2, and others	Suppress immune recruitment and matrix deposition	Most require combination with metabolic intervention

8 Efficacy Evaluation, Biomarkers, and Combination-Treatment Strategies

8.1 Histological Evaluation of the Liver

Liver biopsy remains an important method for evaluating steatosis, ballooning, lobular inflammation, and fibrosis. Drug studies frequently use “MASH resolution without worsening of fibrosis” or “improvement of fibrosis by at least one stage without worsening of MASH” as histological endpoints. However, biopsy represents only a local tissue region and is affected by sampling error and inter-reader variability.

8.2 MRI-PDFF and Quantification of Hepatic Fat

Magnetic resonance imaging-proton density fat fraction (MRI-PDFF) provides noninvasive quantitative evaluation of whole-liver fat content and is suitable for early pharmacodynamic assessment and dose selection. A marked reduction in MRI-PDFF generally indicates improved lipid metabolism but cannot independently demonstrate reversal of hepatocellular ballooning, inflammation, or fibrosis.

8.3 Evaluation of Liver Stiffness

Transient elastography and magnetic resonance elastography can evaluate liver stiffness and support fibrosis-risk stratification. Inflammation, cholestasis, and hepatic congestion can also increase liver stiffness. A reduction in stiffness after treatment should therefore be interpreted together with liver enzymes, inflammatory status, and serum fibrosis markers.

8.4 Serum Biomarkers

ALT, AST, and GGT reflect hepatocellular injury but lack specificity for fibrosis. FIB-4, the NAFLD fibrosis score, ELF, Pro-C3, CK-18, TIMP1, hyaluronic acid, and other markers can evaluate cell death, matrix formation, and fibrosis risk from different perspectives. Combined use is generally more informative than any single marker.

8.5 Metabolic and Cardiovascular Indicators

Body weight, waist circumference, HbA1c, insulin resistance, triglycerides, LDL-C, HDL-C, and blood pressure should be included in efficacy evaluation. Some drugs may improve hepatic pathology while increasing LDL-C or body weight, whereas others may produce substantial weight loss without completely resolving fibrosis. Net clinical benefit therefore requires integrated assessment.

8.6 Pharmacodynamic Stratification and Companion Biomarkers

Patients with high de novo lipogenesis may be more suitable for ACC or FASN inhibition, patients with marked obesity and insulin resistance may derive greater benefit from incretin-based therapies, and patients with elevated LDL-C and hepatic fat may be candidates for THR-β targeting. FGF21, bile acid profiles, lipidomics, and genetic variants may further support stratification but still require standardized validation.

8.7 Combination-Treatment Strategies

Combination treatment can use weight-loss or insulin-sensitizing agents as a metabolic foundation and add hepatic lipid-metabolism or antifibrotic drugs. For example, GLP-1R agonists can reduce fatty acid influx, THR-β or FGF21 agents can increase lipid clearance, and antifibrotic drugs can target residual matrix deposition. Combination design should avoid redundant mechanisms and additive adverse effects.

8.8 Long-Term Clinical Outcomes

Histological improvement is a surrogate endpoint. Long-term evaluation should also assess progression to cirrhosis, portal hypertension, hepatic decompensation, liver transplantation, hepatocellular carcinoma, cardiovascular events, and death. Treatment must demonstrate that histological benefit translates into improved long-term clinical outcomes.

9 Products

9.1 FGF19, FGF21, β-Klotho, and FGFR Signaling Research Products

Catalog #	Product Name	Grade & Purity	Main Application
rp145934	Recombinant Human FGF19 Protein	Animal Free, carrier-free, bioactive, ActiBioPure™, azide-free, His Tag, ≥98% (SDS-PAGE)	Studies of FGF19-FGFR4/β-Klotho signaling, bile acid metabolism, and hepatic lipid regulation
EJ1512801	Mouse Fibroblast Growth Factor 19(FGF19) ELISA Kit	BioReagent	Quantitative detection of FGF15 in mouse MASH models for evaluation of the orthologous FGF15/FGF19 signaling axis
EJ1512795	Mouse Fibroblast Growth Factor 21 (FGF21) ELISA Kit	BioReagent	Evaluation of the FGF21 metabolic response in mouse MASH models
Ab177889	RG7992 (anti-Klotho Beta)	Animal Free, carrier-free, recombinant, ExactAb™, low endotoxin, azide-free, validated, ≥95% (SDS-PAGE & SEC-HPLC), see COA	β-Klotho-targeted binding and FGF19/FGF21 receptor-complex research
rp184968	Recombinant Mouse Klotho beta Protein	Animal Free, carrier-free, bioactive, ActiBioPure™, high-performance, His Tag, ≥95% (SDS-PAGE), expressed in CHO, see COA	FGF19 and FGF21 coreceptor binding and mouse-model research
EJ1513544	Human Klotho Protein β (KLβ) ELISA Kit	BioReagent	Quantitative detection of β-Klotho in human samples
P125865	PD173074	Moligand™, ≥99%	Validation of the role of FGFR1 in FGF21 metabolic signaling
rp145988	Recombinant Human FGFR1 Protein	Animal Free, carrier-free, bioactive, ActiBioPure™, azide-free, high-performance, His Tag, Fc-tagged, ≥95% (SDS-PAGE)	FGF21 receptor binding, ligand screening, and pharmacological research
B174512	BLU-9931	Moligand™, ≥97%	Validation of FGF19-FGFR4 signaling in bile acid and hepatic metabolic regulation
Ab103390	Recombinant FGFR4 Antibody	Recombinant, ExactAb™, validated, see COA	Detection of FGFR4 expression and receptor-signaling changes
rp183620	Recombinant Human FGFR4 Protein	Animal Free, carrier-free, bioactive, ActiBioPure™, high-performance, His Tag, PBS Only, ≥95% (SDS-PAGE)	FGF19 receptor binding and evaluation of FGFR4 inhibitors
EJ1514139	Human Fibroblast Growth Factor Receptor 4 (FGFR4) ELISA Kit	BioReagent	Quantitative detection of FGFR4 in human samples

9.2 GLP-1R and FXR Metabolic Signaling Research Products

Catalog #	Product Name	Grade & Purity	Main Application
Ab209864	Centocor patent anti-GLP-1R (anti-GLP1R)	Animal Free, carrier-free, recombinant, ExactAb™, low endotoxin, azide-free, validated, ≥95% (SDS-PAGE & SEC-HPLC), see COA	GLP-1R binding, receptor-expression, and antibody-function studies
G276156	GLP-1 (7-37)	≥98%	GLP-1R activation and evaluation of cellular signaling and metabolic effects
G1433202	GLP-1R/GIPR agonist-1	—	Research on GLP-1R/GIPR dual activation and metabolic synergy
rp146461	Recombinant Human GLP-1R Protein	Animal Free, carrier-free, bioactive, ActiBioPure™, His Tag, ≥95% (SDS-PAGE)	GLP-1R ligand binding, antibody screening, and receptor-pharmacology research
F288709	Fexaramine	Moligand™, ≥97% (HPLC)	FXR activation and studies of the gut-liver axis, bile acids, and lipid metabolism
G129700	GW4064	Moligand™, ≥98%	FXR activation, CYP7A1 regulation, and hepatic lipid-metabolism research
D288547	DY 268	≥98% (HPLC)	FXR blockade and validation of receptor dependence in bile acid and metabolic effects
EJ1514232	Human Farnesoid X Receptor (FXR) ELISA Kit	BioReagent	Quantitative detection of FXR in human samples

9.3 Lipid Synthesis and Fatty Acid Oxidation Research Products

Catalog #	Product Name	Grade & Purity	Main Application
rp225008	Recombinant Human SREBP1 Protein	Carrier-free, His Tag, ≥90% (SDS-PAGE), expressed in E. coli, see COA	SREBP1 transcriptional regulation and de novo lipogenesis research
F413416	Fasnall	≥99%	FASN inhibition and evaluation of de novo lipogenesis and lipotoxicity
G288292	GSK 2194069	Moligand™, ≥97%	Human FASN inhibition and studies of hepatocellular fatty acid synthesis
EJ1514752	Human Fatty Acid Synthase (FASN) ELISA Kit	BioReagent	Quantitative detection of FASN in human samples
C275139	CAY 10566	≥99%	Inhibition of fatty acid desaturation and evaluation of lipid-droplet formation and lipotoxicity
S275819	SCD1 Inhibitor (DMSO solution)	≥99%	Cell-based SCD1 inhibition and dose-response research
D1439626	DGAT2-IN-3	—	DGAT2 inhibition and studies of triglyceride synthesis and lipid shunting
J287704	JNJ DGAT2-A	≥98%	Evaluation of DGAT2 inhibition on hepatic fat and lipid-droplet formation
P286969	PF 06424439	≥98% (HPLC)	DGAT2 target validation and hepatocellular lipid-metabolism research
rp329551	Recombinant Human CPT1A Protein	≥90% (SDS-PAGE)	CPT1A-mediated mitochondrial fatty acid transport and β-oxidation research

9.4 Products for Research on TGF-β-Mediated Hepatic Stellate Cell Activation and Fibrosis

Catalog #	Product Name	Grade & Purity	Main Application
G125999	GW788388	≥98%	TGF-βRI inhibition and evaluation of hepatic stellate cell activation and collagen expression
I288512	IN 1130	≥98% (HPLC)	TGF-β/SMAD signaling and hepatic fibrosis-mechanism research
L126937	LY2157299	Moligand™, ≥99%	TGF-β receptor kinase and antifibrotic research
R125531	RepSox	≥98%	TGF-βRI blockade and evaluation of SMAD2/3 activation
S125587	SD-208	Moligand™, ≥98%	TGF-βRI inhibition and collagen-deposition research
EJ1514991	Human Transforming Growth Factor Beta 1 (TGF-β1) ELISA Kit	BioReagent	Quantitative detection of TGF-β1 in human samples
EJ1513281	Mouse Transforming Growth Factor β1(TGF-β1) ELISA Kit	BioReagent	Evaluation of TGF-β1 in mouse MASH fibrosis models

9.5 Products for Research on PDGF-Mediated Hepatic Stellate Cell Proliferation and Migration

Catalog #	Product Name	Grade & Purity	Main Application
rp156179	Recombinant Human PDGF AA Protein	Carrier-free, bioactive, ActiBioPure™, high-performance, ≥95% (SDS-PAGE), see COA	PDGFRA signaling and hepatic stellate cell proliferation studies
rp156175	Recombinant Human PDGF-BB Protein	Carrier-free, bioactive, ActiBioPure™, high-performance, His Tag, ≥95% (SDS-PAGE), see COA	Induction of hepatic stellate cell proliferation, migration, and fibrotic phenotypes
rp181276	Recombinant Human PDGF-AB Protein	Carrier-free, bioactive, ActiBioPure™, high-performance, ≥90% (SDS-PAGE), see COA	PDGFRA/PDGFRB combined signaling and cellular-function research
rp181613	Recombinant Human PDGF R alpha Protein	Animal Free, carrier-free, bioactive, ActiBioPure™, His Tag, PBS Only, ≥95% (SDS-PAGE)	PDGFRA ligand binding and inhibitor evaluation
rp183632	Recombinant Human PDGF R beta Protein	Animal Free, carrier-free, His Tag, PBS Only, ≥95% (SDS-PAGE)	PDGFRB binding and hepatic stellate cell-signaling research
Ab120939	Recombinant PDGFR beta Antibody	Recombinant, ExactAb™, validated, 0.3 mg/mL	Detection of PDGFRB in activated hepatic stellate cells
C125124	CP-673451	Moligand™, ≥98%	PDGFR inhibition and evaluation of hepatic stellate cell proliferation and migration
EJ1514839	Human Platelet Derived Growth Factor BB (PDGF-BB) ELISA Kit	BioReagent	Quantitative detection of PDGF-BB in human samples

MASH is jointly driven by dysregulated lipid metabolism, insulin resistance, inflammation, and hepatic fibrosis. THR-β, GLP-1R, FGF21, and lipid-synthesis pathways are major therapeutic directions. Drug development must balance histological improvement in the liver, metabolic benefit, and long-term safety.

For more related articles, please see below:

[1] The Fibroblast Development Factor (FGF) Family

[2] Ligand Systems, Receptor Activation, and Biological Effects of the FGF Pathway