Understanding Why Metabolic-Dysfunction-Associated Steatohepatitis Lags Behind Hepatitis C in Therapeutic Development and Treatment Advances

Abstract

Therapeutic development for metabolic-dysfunction-associated steatohepatitis (MASH) trails behind the success seen in hepatitis C virus (HCV) management. HCV, characterized by a viral etiology, benefits from direct-acting antivirals (DAAs) targeting viral proteins, achieving cure rates exceeding 90%. In contrast, MASH involves complex metabolic, genetic, and environmental factors, presenting challenges for drug development. Non-invasive diagnostics like ultrasound, FibroScan, and serum biomarkers, while increasingly used, lack the diagnostic accuracy of liver biopsy, the current gold standard. This review evaluates therapies for MASH, including resmetirom (Rezdiffra) and combinations like pioglitazone and vitamin E, which show potential but offer modest improvements due to MASH’s heterogeneity. The limited efficacy of these treatments highlights the need for multi-targeted strategies addressing metabolic and fibrotic components. Drawing parallels to HCV’s success, this review emphasizes advancing diagnostics and therapies for MASH. Developing effective, patient-specific therapies is crucial to closing the gap between MASH and better-managed liver diseases, optimizing care for this growing health challenge.

1. Metabolic-Dysfunction-Associated Fatty Liver Disease (MAFLD)

Metabolic-dysfunction-associated fatty liver disease (MAFLD) has become a major public health issue and is the leading cause of chronic liver disease in the West [1]. Traditionally, it was named nonalcoholic fatty liver disease (NAFLD) due to histological presentation closely mimicking alcohol-related liver disease but in the absence of significant alcohol consumption or other causes of liver disease [2]. In 2020, 32 experts from 22 countries reached a consensus, and the nomenclature was changed to MAFLD, as it better encompassed the disease pathophysiology rather than just relying on histopathological similarities to alcohol-induced liver disease. In addition to the change in nomenclature, which made the role of metabolic dysfunction a central feature of the disease, consensus was reached to include evidence of such multi-system metabolic dysfunction in the diagnostic criteria [3]. The growing understanding of the disease pathophysiology and adapting a nomenclature that includes a wider clinical picture of MAFLD as a hepatic manifestation of a multi-system disease has opened avenues for extensive research in this specific disease process [4,5]. Figure 1 illustrates the historical evolution of the nomenclature and diagnostic criteria for MAFLD, highlighting key milestones from its initial recognition as NASH/NAFLD to the current MAFLD definition. This progression underscores the growing emphasis on metabolic dysfunction as central to the disease’s pathogenesis, reflecting broader clinical and research perspectives.

It has also resulted in more individuals with MAFLD and liver damage being diagnosed that were previously being missed. A meta-analysis involving 17 studies comprising of 9,808,677 individuals showed that in the general population, MAFLD was present in 33% (95% confidence interval 29.7–36.5%) compared to NAFLD in 29.1% (95% CI 27.1–31.1%). A total of 15.1% (95% CL 11.5–19.5%) of the patients with fatty liver disease were exclusively diagnosed by implementing the newly adapted MAFLD definition compared to using the traditional NAFLD diagnostic criteria. Similarly, this MAFLD group had higher alanine aminotransferases and aspartate aminotransferases as well as a markedly increased risk for fibrosis (RR 4.2; 95% CL 1.3–12.9) [6].

Figure 1. Evolution of nomenclature and diagnostic criteria for MAFLD. This timeline illustrates the key milestones in the evolution of the MAFLD nomenclature and diagnostic criteria from the early recognition of nonalcoholic steatohepatitis (NASH) and nonalcoholic fatty liver disease (NAFLD) in the 1980s and 1990s, respectively, to the formal adoption of metabolic (dysfunction)-associated fatty liver disease (MAFLD) in 2020. The figure highlights the major proposals and changes that reflect the shift in focus from histopathological similarities to alcohol-induced liver disease towards a more comprehensive understanding that emphasizes the role of metabolic dysfunction as central to the disease pathogenesis [3,7].

Figure 1. Evolution of nomenclature and diagnostic criteria for MAFLD. This timeline illustrates the key milestones in the evolution of the MAFLD nomenclature and diagnostic criteria from the early recognition of nonalcoholic steatohepatitis (NASH) and nonalcoholic fatty liver disease (NAFLD) in the 1980s and 1990s, respectively, to the formal adoption of metabolic (dysfunction)-associated fatty liver disease (MAFLD) in 2020. The figure highlights the major proposals and changes that reflect the shift in focus from histopathological similarities to alcohol-induced liver disease towards a more comprehensive understanding that emphasizes the role of metabolic dysfunction as central to the disease pathogenesis [3,7].

2. Diagnosis of MAFLD

Unlike NAFLD, diagnosis of MAFLD does not require the exclusion of other causes of hepatic diseases like viral hepatitis or excessive alcohol consumption [8]. Diagnosis of MAFLD is based on hepatic steatosis in adults evident by either histology/biopsy, imaging, or from blood markers and one of the following three criteria, namely, obesity/overweight, presence of type 2 diabetes mellitus, or evidence of metabolic dysregulation. As noted in the Asian Pacific Association for the Study of the Liver (APASL) clinical practice guidelines, these diagnostic criteria have been refined to better encompass the underlying metabolic components driving MAFLD, with a stronger emphasis on metabolic dysregulation over mere exclusion of other causes [8]. The APASL guidelines emphasize the need for screening high-risk populations, such as those with type 2 diabetes or metabolic syndrome, as early intervention is critical in preventing the progression of liver disease. Additionally, these guidelines recommend using non-invasive tools like transient elastography and serum biomarkers to assess liver fibrosis, making diagnosis more accessible in regions where liver biopsy may not be practical or feasible [8]. The presence of at least two of the following risk factors accounts for metabolic dysregulation and increased MAFLD risk [4].

• Waist circumference ≥ 102/88 cm in Caucasian men and women or ≥90/80 cm in Asian men and women.
• Blood pressure ≥ 130/85 mmHg or specific drug treatment for hypertension.
• Plasma triglycerides ≥ 150 mg/dL or on specific drug treatment.
• Plasma HDL-cholesterol < 40 mg/dL for men and <50 mg/dl for women or on specific drug treatment.
• Prediabetes
• Plasma high-sensitivity C-reactive protein level ≥ 2 mg/dL
• Homeostasis model assessment of insulin resistance score ≥ 2.5

Ultrasound is a widely accessible imaging modality used for detecting hepatic steatosis. It is particularly advantageous due to its low cost, safety, and ease of use, making it a preferred screening tool in clinical and population settings. However, ultrasound has limitations, including operator dependency, subjective evaluation, and limited sensitivity for detecting mild steatosis (<20% fat infiltration), especially in obese patients. Its accuracy is reported as having a sensitivity of 84.8% and specificity of 93.6%, comparable to other imaging modalities like CT and MRI. Despite these strengths, the limited quantitative capacity of ultrasound can impact its effectiveness in providing detailed assessments of liver fat content, which is crucial in the context of MAFLD [9].

FibroScan (Vibration-Controlled Transient Elastography (VCTE)) is a non-invasive technique that uses liver stiffness measurements (LSM) and a controlled attenuation parameter (CAP) to detect hepatic steatosis and fibrosis [10]. One cross-sectional prospective multicenter study involving 450 patients in seven centers in the United Kingdom who underwent liver biopsy for suspected MAFLD were examined by FibroScan following biopsy, with the primary and secondary outcomes being to assess the diagnostic accuracy of CAP and LSMs compared to liver histology to diagnose hepatic steatosis and fibrosis. Biopsies were scored by two blinded pathologists according to nonalcoholic steatohepatitis clinical research criteria, and these criteria were considered as the reference standard [11]. It was found that CAP and LSM identified steatosis with an area under the receiver operating characteristics (AUROC) value ranging from 0.70 to 0.89, and the size of the probe or steatosis did not affect LSM [12]. This method offers moderate-to-high accuracy for detecting steatosis, making it valuable in clinical settings for initial assessments. The advantages of FibroScan include its rapid and non-invasive nature, with the ability to provide immediate results. However, it shows reduced accuracy in patients with high BMI due to signal attenuation, and it can struggle to detect mild steatosis, which may limit its use in some clinical environments. Access to this technology can also be limited in certain settings due to its cost and the need for specific equipment [12].

The FAST score, which integrates FibroScan (VCTE) results with AST levels, provides an effective way to stratify NASH severity. It demonstrates 85% specificity for identifying NASH with significant activity and fibrosis. Its advantages include simplicity and effectiveness in identifying patients needing intervention without requiring advanced imaging like MRI. However, the need for FibroScan technology can restrict its use in less equipped settings [13].

Magnetic Resonance Imaging–Proton Density Fat Fraction (MRI-PDFF) is a highly accurate imaging technique that quantifies liver fat and assesses fibrosis. It has a high diagnostic accuracy of approximately 90%, making it a gold standard in non-invasive fat quantification. The advantages of MRI-PDFF include its ability to provide detailed, quantitative data on hepatic fat content and fibrosis without exposure to radiation, unlike CT. However, it is costly and less accessible than other modalities, which limits its routine use in clinical practice [14]. The MAST score, which combines MRI-PDFF, MR elastography, and AST levels, is one of the most accurate non-invasive scores for identifying NASH with significant fibrosis, achieving over 90% accuracy. The primary advantages of the MAST score include its integration of advanced imaging and clinical data, making it particularly useful in research and clinical trials. However, its disadvantages include high costs, limited accessibility, and the need for specific imaging equipment, which may not be available in all settings. Therefore, while it excels in specialized centers, its applicability in broader clinical practice remains limited [15].

Computed tomography (CT) and magnetic resonance imaging (MRI) can also be used to diagnose steatosis. Magnetic resonance spectroscopy (MRS) is another advanced modality that quantifies hepatic steatosis with high sensitivity and specificity, providing a detailed analysis of liver fat composition. MRS is considered highly accurate for liver fat quantification, but its high cost and complex setup restrict its use to research settings rather than routine clinical practice. This limitation makes MRS more suitable for academic studies and clinical trials rather than everyday clinical management [16].

Serum biomarkers have also emerged as non-invasive tools in the diagnosis of MAFLD, particularly in assessing the progression to NASH and fibrosis. Biomarkers like cytokeratin-18 (CK-18), which reflects hepatocyte apoptosis, have shown promising diagnostic potential, with the sensitivity and specificity ranging from 63.6% to 83.7%. Combining CK-18 with other markers such as AST and HOMA, as seen in panels like MACK-3, enhances diagnostic accuracy, achieving an AUC of 0.81 for NASH. Other biomarkers, including interleukin-6 (IL-6) and Golgi protein 73 (GP73), further aid in differentiating disease severity, providing a complementary approach to imaging techniques [17].

Table 1. Comparison of non-invasive diagnostic methods for MAFLD.

Diagnostic Method	Use	Accuracy	Advantages	Disadvantages
Ultrasound [9]	Detection of hepatic steatosis	Sensitivity: 84.8%, Specificity: 93.6%, AUC: 0.93	Low-cost, widely accessible, no radiation, high specificity	Operator-dependent, limited in detecting mild steatosis, subjective assessment
FibroScan (VCTE) [12]	Measures liver stiffness and steatosis using LSM and CAP	AUROC: 0.70–0.89	Rapid, non-invasive, immediate results, useful for early assessment	Reduced accuracy in high-BMI settings, limited access in some settings, struggles with mild steatosis
FAST Score [13]	Stratifies NASH severity using FibroScan and AST	Specificity: 85%, AUC: 0.868	Simplicity, effective in clinical stratification without advanced imaging	Requires FibroScan technology, limited use in resource-constrained settings
MRI-PDFF [14]	Quantifies liver fat and assesses fibrosis	Sensitivity: 95%, Specificity: 92%, AUC: 0.96	Highly accurate, quantitative, no radiation, gold standard for fat quantification	High-cost, less accessible, time-consuming compared to other methods
MAST Score [15]	Combines MRI-PDFF, MR elastography, and AST for NASH	Sensitivity: 89.3%, Specificity: 73.1%, AUC: 0.929	Integrates advanced imaging and clinical data, useful in trials	High-cost, requires advanced imaging equipment, less applicable in general practice
MRS [16]	Quantifies hepatic steatosis with detailed analysis	Sensitivity: 95%, Specificity: 92%	Provides precise quantification of liver fat, superior in research settings	High-cost, complex setup, not suitable for routine clinical use
Serum Biomarkers [17]	Non-invasive assessment of NASH and fibrosis progression	Sensitivity: 63.6–83.7% for CK-18; AUC: 0.81 for MACK-3	Accessible, non-invasive, complements imaging, useful in primary care	Variable accuracy, lower specificity compared to imaging, less effective alone in advanced fibrosis

provides a detailed comparison of available non-invasive diagnostic methods for MAFLD, highlighting their specific uses, accuracies, advantages, and disadvantages.

3. Pathogenesis of MAFLD

The development of metabolic-dysfunction-associated fatty liver disease involves the interplay of several factors, including ethnicity, genetics, disruption of intestinal microbiome, insulin resistance, and environmental factors like alcohol intake and unhealthy dietary habits. Variation in these factors explains the difference in prevalence and disease severity in various ethnicities and population groups. For example, the prevalence of MAFLD is 33% in Mexicans, 18% in Puerto Ricans, and 16% in people of Dominican descent [18]. Similarly, African Americans have a lesser prevalence of MAFLD and MASH compared to Hispanics and Caucasians despite having high rates of metabolic syndrome. The presence of a higher frequency of the patatin-like phospholipase domain containing 3 (PNPLA3) gene in Mexicans and a lower frequency of the PNPLA3 gene in African American explains these variations in disease prevalence. PNPLA3 proteins have lipase activity towards triglycerides in hepatocytes and retinyl esters in hepatic stellate cells. Loss of this function leads to triglyceride accumulation in hepatocytes. A meta-analysis of seven studies involving 2023 patients with liver cirrhosis showed a robust association of PNPLA3 gene rs738409 C>G polymorphism with MAFLD, steatosis extent, histologic severity, and liver cirrhosis [19,20,21]. Similarly, hydroxysteroid 17β-dehydrogenases 13 (HSD17B13) is a liver-specific lipid-droplet-associated protein, which is over-expressed in patients and mice with MAFLD, resulting in increased lipid accumulation in the liver [22]. Interestingly, loss of function of HSD17B13 results in protection against chronic liver disease and reduces the progression from steatosis to steatohepatitis [23]. Point mutation (rs58542926, c.499 C>T, P. Glu167Lys) in transmembrane 6 superfamily 2 (TM6SF2) results in the E167K variant, which is known to be independently associated with MAFLD [24,25]. Lean patients with MAFLD carry more TM6SF2 rs58542926 (T) alleles than overweight/obese patients with MAFLD, indicating its independent role in the development of the disease [26]. Environmental factors like alcohol consumption are known to increase the risk for fibrosis in MAFLD, and, especially, patients with T2DM who consume alcohol have the highest risk of advanced fibrosis in MAFLD [27]. MAFLD and excessive alcohol consumption are independent risk factors for mortality, and mortality is highest in patients who have both [28]. A high-fructose diet results in the upregulation of transcription factors and increased de novo lipogenesis [29,30]. Fructose also increases malonyl CoA synthesis, which inhibits fatty acid oxidation and the resultant accumulation of hepatic triglycerides [31]. Chronic consumption of a fructose-rich diet also alters the gut microbiota, resulting in increased bacterial translocation and high levels of circulating lipopolysaccharides that cause liver inflammation and fibrosis [32]. Insulin resistance remains the main factor in thepathogenesis of MAFLD. Insulin resistance results in increased hepatic influx of fatty acids, which induce hepatic inflammation [33]. These free fatty acids also increase oxidative stress in the liver by increasing the production of reactive oxygen species. Elevated levels of hepatic diacylglycerols (DAGs) lead to insulin resistance by activating protein kinase C epsilon (PKCε), which, in turn, impairs insulin-stimulated tyrosine phosphorylation and reduces the activation of phosphoinositide 3-kinase (PI3K), thus effecting insulin signaling [34,35]. Figure 2 provides a visual summary of the primary pathways involved in the pathogenesis of MAFLD, highlighting key genetic, metabolic, environmental, and immune factors that contribute to the disease. This figure emphasizes the central role of metabolic dysfunction and details the interplay of various influences that drive the progression from simple steatosis to more severe forms of liver disease. Understanding these interconnected mechanisms is crucial for developing targeted therapies and improving diagnostic criteria for MAFLD.

4. Metabolic-Dysfunction-Associated Steatohepatitis (MASH)

While diagnosis of MAFLD requires hepatic steatosis and other diagnostic criteria like obesity/overweight, diabetes mellitus, and evidence of metabolic dysfunction, diagnosis of MASH depends on specific biopsy and histological features.

Histologically, MAFLD can range from simple steatosis with or without nonspecific inflammation to more specific histological features like macrovascular steatosis, ballooning of hepatocytes, and lobular inflammation, as seen in MASH. Fibrosis and Mallory–Denk bodies are also seen in MASH but are not needed for the diagnosis of MASH. Unlike simple hepatic steatosis, MASH has very distinctive histological features and distribution in the liver [36]. While diagnosing MASH is a challenge and requires invasive procedures to obtain a biopsy for histology, grading and staging MASH has also been a challenge. One of the grading and staging systems proposed in 1999 by Brunt et al. included steatosis, hepatocyte ballooning, lobular inflammation, and portal inflammation for staging of steatohepatitis into mild, moderate, or severe grades. Similarly, fibrosis staging was carried out based on the extent of fibrosis and included stage 1 with zone 3 perisinusoidal fibrosis only, stage 2 with periportal fibrosis in addition to zone 3 perisinusoidal fibrosis, stage 3 with bridging fibrosis, and stage 4 with hepatic cirrhosis [37]. In 2002, the NASH clinical research network (NASH CRN) proposed the NAFLD activity score (NAS) for use in clinical trials. The NAS scoring system utilizes scores for histological features like steatosis (0–3), hepatocellular ballooning (0–2), and lobular inflammation (0–3) and ranges from 0–8. A NAS score of 4 or more has optimal sensitivity and specificity for predicting steatohepatitis and is the recommended value for admission in interventional trials for MASH [10,38].

5. Challenges in MAFLD Diagnosis and Clinical Trial Design

The quest to find effective treatments for MAFLD is beleaguered by a confluence of challenges stemming from its pathophysiological complexity and methodological and regulatory hurdles. There are many intricacies in developing MAFLD clinical trials, including patient recruitment, the inherent limitations of diagnostic methods, and selecting endpoints for trials. Therefore, a multifaceted approach, informed by the recent literature and findings, is required to navigate the clinical trial landscape for MAFLD.

Histological assessment through liver biopsy remains the gold standard for MAFLD diagnosis and therapeutic efficacy evaluation. This method allows for detailed analysis of liver tissue, evaluating steatosis, lobular inflammation, hepatocellular ballooning, and fibrosis. However, the procedure’s invasiveness, potential for complications, and variability in sampling underscore the necessity for alternative diagnostic approaches. The histological improvement criteria, including reductions in steatosis, inflammation, and hepatocellular ballooning without worsening fibrosis, are critical, yet challenging, benchmarks for assessing treatment outcomes [39]. The invasive nature of liver biopsies, coupled with their associated risks, prompts a growing demand for reliable, non-invasive diagnostic methods.

The advancement of non-invasive biomarkers, such as Magnetic Resonance Imaging–Proton Density Fat Fraction (MRI-PDFF) for quantifying liver fat content, heralds a significant shift towards less invasive disease monitoring and trial endpoints. These methodologies offer a glimpse into the disease’s progression and therapeutic responses without needing invasive liver biopsies. The APASL guidelines recommend prioritizing non-invasive diagnostics such as transient elastography and serum biomarkers, especially in resource-constrained regions where liver biopsy may not be practical or feasible [8]. These recommendations align with the global trend of reducing reliance on invasive diagnostic tools while still providing accurate assessments of disease progression. Despite these advances, non-invasive methods currently serve as complements to, rather than replacements for, histological assessments. Their limitations in fully capturing the nuanced histological changes associated with MAFLD, particularly fibrosis and inflammation, remain a significant challenge [40].

Designing clinical trials for MAFLD involves a delicate balance of scientific rigor and practical considerations. Determining meaningful endpoints, selecting a representative patient population, and defining adequate trial durations and sample sizes are crucial. Trials must accommodate the slow progression of MAFLD and its heterogeneity across patient populations. Furthermore, the evolving regulatory criteria for drug approval demand robust evidence of clinical benefit, complicating the trial design process [39]. The challenge is further compounded by the need to stratify patients by disease severity and manage the variable natural history of MAFLD, necessitating flexible and innovative trial methodologies.

Establishing surrogate endpoints by regulatory agencies represents a significant evolution in the framework for MAFLD therapeutic trials. These endpoints, including the fibrosis regression and resolution of NASH within specified durations, provide clear targets for drug development and approval. However, aligning trial designs with these regulatory standards while also addressing the complex pathophysiology of MAFLD requires a nuanced understanding of the disease and a strategic approach to trial planning [39].

6. Current and Emerging Therapies in MAFLD Clinical Trials

In the evolving landscape of therapeutic interventions for MAFLD, numerous clinical trials have explored diverse pharmacological agents, each targeting different facets of the disease’s complex pathophysiology. By examining the drugs under investigation, their mechanisms of action, and the specific endpoints being utilized to gauge their efficacy, a foundation is laid for a comprehensive analysis.

Table 2. Comparative overview of current and emerging therapies in MAFLD clinical trials.

Therapeutic Agent/Trial Name	Mechanism of Action	Patient Population	Dosing	Primary Endpoint(s) and Key Findings	FDA Approval Status
Resmetirom (Rezdiffra)/ MAESTRO-NASH [41,42]	THR-β agonist; reduces steatosis, inflammation, and fibrosis	Adults with noncirrhotic NASH with moderate-to-advanced liver fibrosis (F2 to F3)	80 mg and 100 mg	Dual primary endpoints met; NASH resolution (80 mg: 25.9%, 100 mg: 29.9%, placebo: 9.7%) and fibrosis improvement without worsening NASH (80 mg: 24.2%, 100 mg: 25.9%, placebo: 14.2%).	Approved in 2024 for adults with noncirrhotic NASH with moderate-to-advanced liver fibrosis
Pioglitazone, Vitamin E/ PIVENS [43]	Pioglitazone: insulin sensitizer Vitamin E: antioxidant	Non-diabetic adults with NASH	Pioglitazone: 30 mg Vitamin E: 800 IU	Improvement in NAS by ≥2 points in two components or NAS ≤ 3, plus ≥1 point improvement in ballooning, with no fibrosis worsening. Vitamin E improved NAS significantly; pioglitazone was similarly effective with insulin sensitization.	Utilized based on trial evidence; not FDA-approved specifically for NASH
Obeticholic Acid/ FLINT [44]	FXR agonist; modulates bile acid, inflammation, and fibrosis levels	Adults with noncirrhotic NASH	25 mg	Histological improvement with a decrease in NAS without fibrosis worsening observed in 45% of the treatment group vs. 21% in the placebo group.	Fast Track designation from FDA for NASH; awaiting full approval
Vitamin E/ TONIC [45]	Antioxidant	Pediatric NAFLD	800 IU	No sustained ALT reduction; vitamin E led to improved NASH resolution and ballooning scores without significant changes in fibrosis, inflammation, or steatosis. Metformin showed no significant improvement.	Vitamin E has shown efficacy in trials, but it is not specifically FDA-approved for NAFLD/NASH in children

provides a detailed comparative overview of current and emerging therapies in MAFLD clinical trials, summarizing key therapeutic agents, mechanisms of action, patient populations, dosing, primary endpoints, key findings, and FDA approval status. Such comparative insights are crucial for advancing our understanding of MAFLD treatment options and refining future therapeutic strategies. This exploration illuminates current interventions’ potential and guides the development of novel treatments, marking a critical step toward optimizing care for patients with MAFLD.

6.1. Resmetirom/Rezdiffra (MAESTRO-NASH Trial and FDA Approval)

The MAESTRO-NASH clinical trial has significantly contributed to the evolving landscape of therapeutic interventions for MAFLD by spotlighting Resmetirom (marketed as Rezdiffra). This thyroid hormone receptor-beta (THR-β) agonist has emerged as a pioneering treatment to ameliorate the characteristic triad of MAFLD pathology: steatosis, inflammation, and fibrosis. Administered in 80 mg and 100 mg dosages, Resmetirom capitalizes on enhancing lipid metabolism and reducing lipotoxicity, which is pivotal for reversing liver damage. The trial’s distinctive dual primary endpoints, aiming for NASH resolution without fibrosis worsening and fibrosis improvement without NASH worsening, emphasize a holistic approach to evaluating Resmetirom’s therapeutic impact on MAFLD [41].

The trial demonstrated that both dosages of Resmetirom substantially outperformed the placebo in achieving NASH resolution without worsening fibrosis and improving fibrosis without exacerbating NASH. Specifically, NASH resolution without fibrosis worsening was observed in 25.9% and 29.9% of patients receiving 80 mg and 100 mg doses, respectively, compared to only 9.7% in the placebo group. Similarly, fibrosis improvement without NASH worsening was noted in 24.2% and 25.9% of patients in the 80 mg and 100 mg groups, respectively, against 14.2% in the placebo cohort. These findings underscore Resmetirom’s efficacy in addressing the critical endpoints recognized for therapeutic intervention in MAFLD [41].

The significance of Resmetirom in the therapeutic landscape was further solidified by its FDA approval on 14 March 2024, under the trade name Rezdiffra. This landmark approval marked the introduction of the first treatment option for adults with noncirrhotic NASH and moderate-to-advanced liver fibrosis, advocating for its use alongside diet and exercise. The approval, predicated on an accelerated pathway hinging on surrogate endpoints, heralds a new era of targeted, metabolic-based therapy for NASH, reflecting a leap toward precision medicine in hepatology.

Rezdiffra’s indication for adults with noncirrhotic NASH and stages F2 to F3 liver fibrosis, with dosing based on actual body weight, addresses a significant unmet clinical need in NASH care. The drug’s safety and efficacy, thoroughly vetted in a 54-month randomized, double-blind, placebo-controlled trial, coupled with the necessity for a post-approval study to elucidate its clinical benefits fully, illustrates a cautious, yet optimistic, approach towards establishing a new standard in MAFLD treatment. Adverse reactions, predominantly gastrointestinal, underline the importance of patient monitoring for hepatotoxicity and gallbladder-related complications, emphasizing the need for careful drug interaction management to optimize therapeutic outcomes and minimize risks.

This FDA approval, propelled by the Breakthrough Therapy, Fast Track, and Priority Review designations, attests to Rezdiffra’s therapeutic promise and the pressing need to address the escalating burden of NASH. As the clinical community anticipates further data from confirmatory trials, Rezdiffra’s introduction signifies a pivotal advancement in the quest for effective treatments for this challenging liver disease, setting a precedent for future therapeutic innovations in MAFLD management [42].

6.2. Pioglitazone vs. Vitamin E vs. Placebo (PIVENS Trial)

The PIVENS trial, a pivotal study within the landscape of NASH research, investigated the therapeutic potential of pioglitazone and vitamin E against a placebo in non-diabetic adults with NASH. Pioglitazone, a thiazolidinedione, exerts its effects by improving insulin sensitivity, thereby addressing a fundamental aspect of NASH pathogenesis. On the other hand, vitamin E, a potent antioxidant, targets the oxidative stress pathway, a key contributor to liver inflammation and damage in NASH.

Structured to elucidate improvements in hepatic histology, the PIVENS trial employed the NAFLD activity score (NAS) as its primary outcome measure. This score quantifies the severity of steatosis, lobular inflammation, and hepatocellular ballooning, offering a nuanced assessment of treatment efficacy. This strategic choice of endpoints, focusing on histological changes, highlights the trial’s aim to capture the multifaceted nature of the therapeutic impact on NASH. Secondary outcomes encompass biochemical markers of liver function, insulin sensitivity, and fibrosis progression, providing a holistic view of treatment effects.

The trial’s design—a multicenter, randomized, double-masked, placebo-controlled study—enabled a rigorous evaluation of pioglitazone and vitamin E over 96 weeks of treatment. Participants, following randomization, were administered either pioglitazone (30 mg daily), vitamin E (800 IU daily), or a placebo, with liver biopsies performed before and after treatment to assess histological outcomes. The primary outcome measure was improvements in NAS by at least two points across at least two NAS components or a post-treatment NAS of three or fewer, coupled with at least a one-point improvement in hepatocyte ballooning without worsening fibrosis [43].

Key findings from the trial underscore the nuanced efficacy of pioglitazone and vitamin E in managing NASH. While both treatments showed promise in improving specific histological features, the comparative analysis of these interventions against a placebo underscores their potential roles in the broader therapeutic landscape of NASH. The trial’s rigorous design, extensive duration, and comprehensive outcome measures contribute significantly to our understanding of NASH management, laying the groundwork for future therapeutic strategies [43].

6.3. Obeticholic Acid (FLINT Trial)

The Farnesoid X nuclear receptor (FXR) ligand, obeticholic acid, marked a significant advancement in the treatment of noncirrhotic NASH through the FLINT trial. This multicenter, randomized, placebo-controlled trial meticulously assessed the efficacy of obeticholic acid, leveraging its potent FXR agonistic properties to regulate bile acid levels, inflammation, and fibrosis in the liver, central to NASH pathophysiology.

Administered orally at a daily dose of 25 mg over 72 weeks, the trial delineated the primary endpoint as an improvement in liver histology, underscored by a decrease in the NAS score without exacerbating fibrosis. The design underscored the drug’s potential in addressing the intricate mechanisms underpinning NASH, thereby providing critical insights into bile acid regulation’s role in liver health. The secondary endpoints, encompassing biochemical markers, lipid profiles, and other systemic effects, enriched the understanding of obeticholic acid’s comprehensive impact [44].

Significantly, 45% of participants in the obeticholic acid group demonstrated improved liver histology compared to 21% in the placebo group, highlighting the drug’s efficacy in mitigating NASH’s histological features. This was substantiated by a relative risk of 1.9, underpinning obeticholic acid’s potential as a therapeutic agent. However, the trial also revealed challenges, notably the development of pruritus in 23% of patients treated with obeticholic acid compared to 6% in the placebo group, underscoring the necessity for a balanced consideration of therapeutic benefits against potential side effects [44].

6.4. Vitamin E or Metformin (TONIC Trial)

The TONIC trial stands as a seminal investigation into the management of pediatric NAFLD, a condition escalating in parallel with childhood obesity rates. The randomized, double-blind, placebo-controlled clinical trial scrutinized the efficacy of vitamin E and metformin in mitigating NAFLD in children and adolescents devoid of diabetes, spotlighting the distinctive challenges associated with pediatric liver disease treatment. Vitamin E, an antioxidant, targets oxidative stress pathways integral to liver damage, whereas metformin, primarily used for type 2 diabetes management, was evaluated for its potential to enhance insulin sensitivity and diminish hepatic steatosis. The trial’s primary endpoint centered on achieving a sustained reduction in alanine aminotransferase (ALT) levels, a biomarker of liver inflammation, with secondary endpoints exploring histological measures of liver health and broader metabolic parameters, presenting a holistic assessment of treatment efficacy and safety within this vulnerable demographic [45].

Over 96 weeks, the TONIC trial methodically administered daily doses of 800 IU of vitamin E, 1000 mg of metformin, or a placebo to a cohort of 173 participants aged from 8 to 17 years with biopsy-confirmed NAFLD. Despite the interventions, sustained ALT level reduction did not significantly differ across the groups, indicating that neither vitamin E nor metformin outperformed the placebo in this primary measure. However, nuanced findings emerged in histological evaluations and other secondary outcomes. Vitamin E significantly improved hepatocellular ballooning scores and the NAS score, suggesting its potential to attenuate specific pathological features of NASH within pediatric populations. Conversely, metformin’s impact was less pronounced, offering modest improvements but underscoring the complex interplay of metabolic factors in pediatric NAFLD.

The TONIC trial’s implications extend beyond the primary outcomes. Among children with NASH, vitamin E facilitated a higher resolution rate compared to the placebo, marking a noteworthy stride in identifying effective treatments for this subgroup. This aligns with the broader recognition of oxidative stress as a pivotal driver in NASH progression and vitamin E’s role in counteracting these detrimental pathways. Furthermore, the trial illuminated the pediatric NAFLD landscape’s intricacies, from the diagnostic challenges to the nuanced effects of therapeutic interventions, emphasizing the urgent need for tailored treatment strategies [45].

7. Advanced Exploration of Alternative Therapies and Diagnostic Innovations for MAFLD

Recent research efforts have brought forth significant advancements in both diagnostic and therapeutic strategies for MAFLD/MASH, signaling a turning point in the management of this complex condition. While much of the focus has traditionally been on managing metabolic dysfunction through lifestyle modification and insulin sensitizers, a growing body of evidence now highlights more sophisticated, multi-targeted therapeutic approaches and the integration of non-invasive diagnostics as a way to streamline MASH care.

7.1. Novel Diagnostic Approaches and Enhancing Non-Invasive Techniques

As the field of MASH treatment progresses, accurate, non-invasive diagnostics have become crucial in monitoring disease progression and therapeutic response. Traditionally, liver biopsy has been the gold standard for diagnosing MASH, yet its invasive nature and associated risks make it less ideal for routine monitoring. Recent advances in non-invasive diagnostics are transforming this landscape.

One of the most promising developments is the use of MRI-PDFF and the MAST score. MRI-PDFF allows for the quantification of liver fat content and, when combined with MR elastography and AST levels in the MAST score, provides a highly accurate tool for diagnosing significant fibrosis and NASH. The MAST score, which has achieved a diagnostic accuracy of over 90%, is now considered one of the most reliable non-invasive methods for identifying patients at risk of advanced disease [14]. These methods are particularly useful in clinical trials and in settings where frequent liver assessments are necessary without the risks associated with biopsy.

Another significant advancement is the FAST score, which uses a combination of FibroScan (Vibration-Controlled Transient Elastography) results and AST levels. This score has demonstrated 85% specificity for identifying NASH with significant activity and fibrosis, making it an effective tool for stratifying patients based on the severity of their disease [13]. The FAST score is especially beneficial in resource-constrained settings where more complex imaging modalities, like MRI-PDFF, may not be available.

In addition to imaging advancements, serum biomarkers have emerged as an invaluable tool for non-invasive diagnosis and monitoring. Biomarkers such as cytokeratin-18 (CK-18), which reflects hepatocyte apoptosis, and Golgi protein 73 (GP73), which correlates with liver fibrosis, have shown potential in diagnosing NASH and monitoring disease progression. When combined in panels like MACK-3 (which includes CK-18, AST, and HOMA-IR), these biomarkers provide a powerful non-invasive approach for assessing MASH and its progression toward fibrosis [17]. While these panels have not yet replaced liver biopsy entirely, they hold great promise for reducing reliance on invasive methods in the future.

7.2. Novel Therapeutic Approaches and Multi-Targeted Strategies for MASH

Historically, treatment options for MASH have focused on managing its metabolic components, such as insulin resistance and lipid metabolism disturbances. However, these approaches have often been insufficient in reversing the disease or preventing its progression to fibrosis and cirrhosis. As a result, recent research has shifted toward multi-targeted therapies that address multiple aspects of the disease simultaneously.

One of the most exciting advancements in this area is the development of thyroid hormone receptor-beta (THR-β) agonists. The drug Resmetirom (marketed as Rezdiffra) has emerged as a leading candidate in this class, showing promising results in phase 3 clinical trials. In these trials, patients receiving Resmetirom experienced significant improvements in both NASH resolution and fibrosis without worsening other histological features [41]. Resmetirom works by enhancing lipid metabolism and reducing lipotoxicity, directly targeting two key pathways involved in the pathogenesis of MASH. The dual primary endpoints of the MAESTRO-NASH trial, NASH resolution without worsening fibrosis and fibrosis improvement without worsening NASH, underscore the multi-targeted potential of Resmetirom in treating the metabolic and inflammatory components of MASH.

Combination therapies are also gaining traction as an effective approach to managing the multifactorial nature of MASH. The PIVENS trial investigated the use of pioglitazone (an insulin sensitizer) and vitamin E (an antioxidant) in non-diabetic patients with NASH. Both drugs showed efficacy in reducing histological markers of steatohepatitis, particularly hepatocellular ballooning and lobular inflammation. Pioglitazone targets insulin resistance, a key driver of MASH pathogenesis, while vitamin E mitigates oxidative stress, which is known to exacerbate liver inflammation and fibrosis [43]. Together, these drugs offer a comprehensive therapeutic approach by targeting both metabolic and oxidative pathways.

7.3. Potential for Personalized Medicine in MASH

With the growing understanding of MASH’s complex genetic and metabolic underpinnings, the potential for personalized medicine is becoming a reality. Genetic variants such as PNPLA3 and TM6SF2 have been shown to significantly influence the severity of MASH and its progression to fibrosis [20]. For instance, individuals carrying the PNPLA3 I148M variant are more likely to develop more severe forms of steatosis and fibrosis, while patients with mutations in TM6SF2 are predisposed to increased liver fat accumulation and reduced lipid export from the liver. These insights into genetic susceptibility are paving the way for personalized treatment strategies.

Emerging therapies are increasingly being tailored to specific genetic profiles. For example, patients with PNPLA3 mutations may benefit from therapies that target lipid metabolism more aggressively, while those with TM6SF2 mutations might respond better to treatments that reduce hepatic lipid accumulation. In this context, FXR agonists, GLP-1 receptor agonists, and PPAR-γ agonists are being investigated as potential treatments that could be customized to an individual’s genetic and metabolic profile [40].

7.4. Future Perspectives and Novel Research Directions

In addition to these advances, there is increasing interest in the role of the gut–liver axis in the development and progression of MASH. The gut microbiome, which is altered in many patients with metabolic diseases, has been shown to influence liver inflammation and fibrosis through mechanisms such as bacterial translocation and dysregulated bile acid signaling [32]. This novel area of research is exploring the use of probiotics, prebiotics, and fecal microbiota transplantation (FMT) as potential therapies for restoring gut homeostasis and, by extension, reducing liver inflammation and fibrosis.

Clinical trials investigating the use of microbiome-modifying therapies are still in their early stages but show promise in offering a new therapeutic avenue for patients who do not respond to traditional treatments. As our understanding of the gut–liver axis deepens, it is likely that future MASH therapies will incorporate these strategies, either as standalone treatments or in combination with metabolic and anti-inflammatory agents.

By integrating these diagnostic innovations and therapeutic strategies, the field of MASH treatment is moving toward a more personalized, multi-targeted approach. This represents a significant shift from the traditional management of the disease and underscores the potential for future breakthroughs in both the treatment and monitoring of MASH. The advancements in non-invasive diagnostics, multi-pathway therapeutic agents, and personalized medicine are laying the groundwork for more effective and tailored MASH management.

8. Hepatitis C vs. MAFLD Therapeutic Development

The past two decades have witnessed extraordinary progress in hepatitis C (HCV) treatment, marking a significant achievement in the field of infectious diseases. The therapeutic landscape for HCV has evolved from interferon-based regimens, which had modest efficacy and considerable side effects, to the introduction of direct-acting antiviral agents (DAAs). These DAAs function by targeting specific nonstructural proteins of HCV, which has translated to cure rates exceeding 90%. As a result of DAAs, patient prognosis has significantly improved with reduced liver-related morbidity and mortality [46].

Several factors explain the rapid success of therapeutic development for HCV compared to the slower progress in MASH. First, HCV is caused by a viral infection with a well-defined structure and life cycle. This has allowed drug development to focus on creating direct-acting antivirals (DAAs) that target specific viral proteins critical to the replication of the virus. In contrast, MASH is a metabolic disease characterized by a complex interplay of genetic, environmental, and metabolic factors. MASH’s multifactorial pathogenesis makes it difficult to identify clear therapeutic targets, as there is no single pathogen like a virus to target. For example, insulin resistance, lipid metabolism disturbances, oxidative stress, and genetic factors all contribute to MASH development, making it a much more complicated target for drug development than HCV, which is caused by a singular, identifiable viral agent.

In addition to therapeutic development, comparing the pathophysiology of HCV-associated liver disease with MASH reveals distinct mechanisms underlying steatosis in each condition. In HCV-associated steatosis, particularly in genotype 3 infections, viral factors play a central role in inducing lipid accumulation in hepatocytes. The HCV core protein is a major driver of steatosis, interfering with lipid metabolism and promoting hepatic fat deposition. This virus-induced steatosis can be reversed with antiviral treatment, particularly DAAs, which target viral replication and thus reduce the progression of liver damage [47]. In contrast, MASH is driven primarily by metabolic dysfunction, such as insulin resistance, dyslipidemia, and oxidative stress, rather than viral factors. These metabolic disturbances lead to hepatic fat accumulation, inflammation, and progressive fibrosis. Unlike in HCV, where viral clearance results in improvements in steatosis, MASH requires multifaceted therapeutic approaches targeting the metabolic and fibrotic pathways involved in disease progression [47].

Moreover, the availability of a definitive clinical endpoint for HCV, such as the Sustained Virological Response (SVR), has enabled the development of DAAs to focus on achieving viral clearance. The SVR is a widely accepted biomarker that signifies the eradication of the virus from the patient’s bloodstream and is closely correlated with long-term outcomes such as reduced liver-related complications. MASH, on the other hand, lacks an equivalent, universally accepted non-invasive biomarker for assessing treatment success. Currently, the gold standard for diagnosing and monitoring MASH remains liver biopsy, which is invasive, costly, and prone to sampling errors. Non-invasive methods like FibroScan and MRI-PDFF are emerging, but their capacity to fully capture the histological nuances of MASH, such as ballooning hepatocytes and fibrosis progression, is still limited [10]. This absence of reliable, universally accepted biomarkers complicates both the design and evaluation of clinical trials for MASH.

In terms of clinical trial design, the therapeutic development for HCV was facilitated by the virus’s relatively uniform disease course and well-defined patient populations. In contrast, MASH patients present with significant variability in disease severity, ranging from simple steatosis to advanced fibrosis and cirrhosis. This heterogeneity requires larger and longer clinical trials to capture meaningful therapeutic outcomes, as the progression of MASH can be slow and unpredictable. Furthermore, while HCV trials could focus on a clear viral endpoint, MASH trials must consider multiple factors, including reductions in liver fat, inflammation, fibrosis, and metabolic parameters, further complicating trial designs.

Additionally, regulatory frameworks for HCV treatment development were streamlined, allowing DAAs to achieve accelerated approval pathways due to the clear endpoints and well-understood nature of the disease. In contrast, the regulatory approval of drugs for MASH remains more challenging due to the lack of universally agreed-upon surrogate endpoints for clinical trials. Although some regulatory bodies are beginning to accept surrogate markers like fibrosis reduction, significant gaps remain in aligning regulatory standards with the complexity of MASH.

The journey towards HCV therapeutic discovery sheds light on the potential strategies for addressing diseases like MAFLD and MASH. Unlike MAFLD/MASH, which is hindered by a complex interplay of metabolic dysfunctions, the path to DAAs for HCV was paved by a thorough understanding of its viral structure, life cycle, and the establishment of well-defined clinical endpoints such as the SVR. These critical factors contributed to the streamlined development and rapid approval of DAAs, setting a benchmark for antiviral therapy rarely replicated in other diseases [48]. In contrast, the development of treatments for MAFLD and MASH faces significant challenges due to the absence of universally accepted non-invasive diagnostic criteria and endpoints, complicating clinical trial design and regulatory approval processes.

Table 3. Comparative analysis of hepatitis C and MASH.

Characteristic	Hepatitis C	MASH
Etiology	Viral infection	Metabolic dysfunction (insulin resistance, oxidative stress, genetic factors)
Steatosis Mechanism	Viral protein-driven mechanism (HCV core protein)	Metabolic disturbances (insulin resistance, dyslipidemia)
Primary Clinical Endpoint	Sustained Virological Response (SVR)	No single endpoint; liver biopsy is the gold standard for diagnosis
Non-Invasive Diagnostic Tools	HCV RNA testing, FibroScan	FibroScan, MRI-PDFF, serum biomarkers (e.g., CK-18, GP73)
Therapeutic Targets	Viral proteins (NS5A, NS5B, and NS3/4A inhibitors)	Multiple pathways (metabolic, inflammatory, fibrotic components)
Standard Treatment	Direct-acting antivirals (DAAs)	Combination therapy (e.g., pioglitazone with vitamin E, Resmetirom)
Regulatory Pathway	Streamlined, clear clinical endpoint (SVR)	Complex, no universally accepted surrogate endpoints
Clinical Trial Design	Relatively uniform population, clear endpoint	Heterogeneous population, variable disease severity; longer, larger trials required due to slow disease progression
Response to Therapy	High (>90% SVR)	Modest improvements; multi-pathway approach required
Progression to Fibrosis	Slowed or halted with viral clearance	Common in advanced stages, requires targeted anti-fibrotic treatments

provides a detailed comparative analysis of hepatitis C and MASH, illustrating key differences in pathogenesis, diagnostic methods, and treatment strategies. This comparison highlights why therapeutic development for MASH presents greater challenges compared to HCV.

8.1. FDA-Approved Hepatitis C Medications and Their Clinical Trials

A series of groundbreaking DAAs have received FDA approval, marking a significant shift from side-effect-laden interferon-based therapies to highly efficacious and tolerable treatments. Sofosbuvir, a pivotal drug in this evolution, exemplifies this shift. It forms the backbone of several combination therapies, including Sofosbuvir/Velpatasvir and Sofosbuvir/Velpatasvir/Voxilaprevir, offering high cure rates across various HCV genotypes with minimal side effects [46,49]. DAAs such as Sofosbuvir work by specifically targeting and inhibiting the nonstructural proteins of the hepatitis C virus, which are crucial for its replication. For instance, Sofosbuvir inhibits NS5B polymerase, disrupting viral RNA synthesis, which is essential for the viral replication cycle [50].

Table 4. Detailed comparison of FDA-approved direct-acting antivirals for hepatitis C.

DAA	Target Protein	Genotypic Efficacy	Side Effects	Key Clinical Trial Outcome
Sofosbuvir [50]	NS5B polymerase	High across all genotypes	Fatigue, headache, nausea, insomnia, anemia	Cure rate > 95% in combination therapies
Velpatasvir [50]	NS5A protein	Broad spectrum, high across all genotypes	Headache, fatigue, nausea, asthenia, insomnia	Pan-genotypic efficacy, high cure rates in combination with Sofosbuvir
Voxilaprevir [50]	NS3/4A protease	High in resistance-associated variants	Headache, fatigue, diarrhea, nausea, elevated bilirubin levels	High cure rates in DAA-experienced patients, especially those with resistance-associated variants

below compares different DAAs, highlighting their target nonstructural proteins, genotypic efficacy, and side effects for clearer differentiation.

The ASTRAL studies, pivotal in approving Sofosbuvir/Velpatasvir, demonstrated cure rates exceeding 95% across a broad range of HCV genotypes, setting a new standard in the treatment landscape. Similarly, the POLARIS trials underscored the efficacy of Sofosbuvir/Velpatasvir/Voxilaprevir in patients who had previously failed DAA regimens, offering a potent rescue therapy with cure rates close to 100% for those without prior NS5A inhibitor exposure [51].

The primary endpoint for HCV therapeutic trials has been the achievement of the SVR, defined as undetectable HCV RNA levels in the blood 12 to 24 weeks post treatment completion. This endpoint serves as a proxy for virological cure, closely correlating with a significant reduction in liver-related morbidity and mortality. The precision in measuring the SVR has been enhanced by advances in molecular diagnostic techniques, enabling the accurate assessment of viral eradication and the efficacy of antiviral therapy [52].

Recent studies, such as those evaluating the real-world effectiveness of glecaprevir/pibrentasvir and elbasvir/grazoprevir, have reinforced the centrality of the SVR as a reliable indicator of treatment success, reporting high SVR rates across diverse patient populations, including those with renal impairment and compensated cirrhosis [53,54].

8.2. Implications and Future Directions

The success of DAAs in achieving high SVR rates has not only transformed HCV treatment but has also provided a blueprint for developing therapeutic agents for other chronic conditions, such as MAFLD and MASH. The experience gained from HCV clinical trials emphasizes the importance of selecting appropriate endpoints and patient populations to accurately assess therapeutic efficacy and guide treatment decisions.

Furthermore, the integration of novel diagnostic tools, such as HCV core antigen quantification, offers the potential to streamline the monitoring of treatment response, enabling more efficient and cost-effective management of HCV infection [55,56]. Overall, the transformative journey from interferon-based therapies to the advent of DAAs in HCV treatment illustrates the power of targeted drug development and strategic clinical trial design. Inspired by the rapid therapeutic developments in HCV, researchers and clinicians are encouraged to pursue innovative solutions that could similarly transform patient outcomes in MAFLD and MASH, addressing a growing global health crisis. This comparative analysis not only highlights the successes in HCV treatment but also points towards the necessary collaborative research efforts, innovative trial designs, and regulatory flexibility needed to overcome hurdles in MAFLD/MASH therapeutic development.

9. Conclusions

The rapid advancements in HCV treatment over the past two decades represent a milestone in modern medicine. DAAs, which target the virus’s nonstructural proteins, have led to cure rates exceeding 90%, significantly reducing liver-related morbidity and mortality. The success of HCV therapeutic development is due to several factors, including the virus’s well-defined etiology, the availability of a clear clinical endpoint (SVR), and a relatively uniform disease course, allowing for the creation of highly specific therapies and streamlined clinical trials.

In contrast, MASH presents unique challenges due to its multifactorial metabolic pathogenesis, which lacks a singular therapeutic target like HCV. While HCV-associated steatosis, particularly in genotype 3, is driven by viral factors and can be reversed with antiviral therapy, MASH is driven by metabolic dysfunctions such as insulin resistance, dyslipidemia, and oxidative stress. As a result, MASH requires multi-pathway treatments that address fat accumulation, inflammation, and fibrosis simultaneously.

MASH also lacks a universally accepted, non-invasive clinical endpoint akin to SVR. Liver biopsy remains the gold standard for diagnosis and monitoring, but its invasive nature limits its use in both clinical trials and routine practice. Emerging non-invasive methods, such as FibroScan and MRI-PDFF, show promise, but they still cannot fully capture the histological nuances of MASH. This absence of clear clinical endpoints complicates trial design and regulatory approval.

Furthermore, the variability in disease severity across MASH patients, ranging from simple steatosis to cirrhosis, adds another layer of complexity. This heterogeneity necessitates larger and longer clinical trials, slowing the pace of drug development. Moreover, the regulatory frameworks for MASH therapies are not yet fully aligned with the complexity of the disease, with inconsistent acceptance of surrogate endpoints like fibrosis reduction.

Despite these challenges, recent advances in understanding MASH pathogenesis and the development of multi-targeted therapies, such as Resmetirom and combination treatments like pioglitazone with vitamin E, offer hope for more effective treatments. The increasing role of non-invasive diagnostics and personalized medicine highlights the potential for future breakthroughs. Learning from the success of HCV therapeutic development, future MASH trials must focus on identifying clear surrogate biomarkers and simplifying trial designs to accelerate the approval of effective therapies.