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. Author manuscript; available in PMC: 2017 Jun 30.
Published in final edited form as: Curr Opin Gastroenterol. 2017 May;33(3):134–141. doi: 10.1097/MOG.0000000000000356

Current and future pharmacologic treatment of nonalcoholic steatohepatitis

Bubu A Banini 1, Arun J Sanyal 1
PMCID: PMC5491795  NIHMSID: NIHMS863677  PMID: 28346237

Abstract

Purpose of review

Nonalcoholic steatohepatitis (NASH), the aggressive form of nonalcoholic fatty liver disease (NAFLD), can progress to cirrhosis and hepatocellular cancer in 5–15% of patients and is rapidly becoming the leading cause for end-stage liver disease. Dietary caloric restriction and exercise, currently the cornerstone of therapy for NAFLD, can be difficult to achieve and maintain, underscoring the dire need for pharmacotherapy. This review presents the agents currently used in managing NAFLD and their pharmacologic targets. It also provides an overview of NAFLD agents currently under development.

Recent findings

Therapies for NASH can be broadly classified into agents that target the metabolic perturbations driving disease pathogenesis (such as insulin resistance and de novo lipogenesis) and agents that target downstream processes including cell stress, apoptosis, inflammation, and fibrosis. Modulation of peroxisome proliferator-activator receptors, farnesoid-X-receptors, and the glucagon-like peptide 1 pathway have been shown to improve liver histology. The intestinal microbiome and metabolic endotoxemia are novel targets that are currently under review. Antioxidants such as vitamin E, and more recently anti-inflammatory agents such as apoptosis signal-regulating kinase 1 inhibitors show promise as therapy for NASH. Several antifibrotic agents including C-C chemokine receptor type 2 and type 5 antagonists have been shown to inhibit the progression of fibrosis toward cirrhosis.

Summary

There are currently several agents in the drug pipeline for NASH. Within the next few years, the availability of therapeutic options for NAFLD will hopefully curb the rising trend of NAFLD-related end stage liver disease.

Keywords: chronic liver disease, cirrhosis, fibrosis, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis

INTRODUCTION

Lifestyle modification, consisting of diet and exercise, is the cornerstone of therapy for nonalcoholic fatty liver disease (NAFLD) and has been shown by many studies to improve liver histology [1,2]. However, lifestyle modification is difficult to achieve and to sustain [3]. Recent progress in understanding of NAFLD pathogenesis has led to the development of new therapeutics or the repurposing of currently available drugs that have historically been given for other indications (Fig. 1). In this review, we provide an overview of current therapeutics for NASH and highlight recent findings in NASH pharmacotherapy.

FIGURE 1.

FIGURE 1

Current and emerging therapies for NAFLD and their mechanisms of action. ASK-1, apoptosis signal-regulating kinase; CCR2–CCR5, chemokine receptors type 2 and type 5; DPP-4, dipeptidyl peptidase-4; FXR, farnesoid X receptor; GLP-1, glucagon-like peptide-1; HMG-CoA, 3-hydroxy-3-methyl-glutaryl-coenzyme A; LOXL2, lysyl oxidase-like 2; LPS, lipopolysaccharide; NAFLD, nonalcoholic fatty liver disease; NASH, nonalcoholic steatohepatitis; PDE, phosphodiesterase; PPAR, peroxisome proliferator-activated receptor; RA, receptor agonist; SCD1, stearoyl coenzyme A desaturase 1; SGLT-2, sodium–glucose co-transporter 2.

TARGETING THE GUT

The portal system supplies about 70% of the total hepatic blood flow [4]. NAFLD is associated with increased gut permeability, allowing transport of gut metabolites and bacterial products into the portal circulation [5].

Gut microbiome

A Number of mechanistic pathways within the gut–liver axis appear to be activated in NAFLD, including lipopolysaccharide production, endogenous alcohol production, and conversion of dietary phosphatidylcholine to choline and hepatotoxic trimethylamine [6]. Presumably, changing the composition of the gut microbiome, either by changing the distribution of the gut bacterial flora, modulating metabolite production, or inhibiting translocation of bacteria or their metabolites to the liver could be beneficial in NAFLD.

Bovine colostrum is enriched with IgG directed against antigens injected into cows immediately prior to calving. An IgG-rich bovine colostrum extract, IMM-124e, generated from cows immunized against lipopolysaccharide was shown to improve insulin sensitivity, glycemic control, and liver enzymes in a small pilot study [7]. A phase 2 trial is currently evaluating 24 weeks of IMM-124e on biopsy-proven NASH (ClinicalTrials.gov identifier NCT02316717). Solithromycin, a macrolide antibiotic with anti-inflammatory properties, has been found to improve NASH in animal studies [8] and is currently being studied in a phase 2 clinical trial (NCT02510599).

Antiobesity medications

Orlistat is a gut lipase inhibitor which decreases the absorption of dietary fats [9]. It has been approved for treatment of obesity and recently became available over the counter in the United States for weight loss. A small pilot study suggested that Orlistat-mediated weight loss is associated with reduction in hepatic steatosis [10]. However, the impact of Orlistat on steatohepatitis and its ability to slow the progression of NASH to cirrhosis remains unknown. Current data does not support the use of orlistat as treatment for NAFLD. However, it can be prescribed as an adjunct medication to help with weight loss in the NAFLD patient population.

TARGETING METABOLIC PATHWAYS

Progression of NAFLD is dependent on a number of metabolic processes in the liver. Medications in this category aim to reduce the accumulation of hepatic fat and resultant metabolic stress.

Peroxisome proliferator-activator receptors

Peroxisome proliferator-activator receptors (PPARs) are nuclear receptors that bind fatty acids and fatty acid derivatives to regulate a number of metabolic processes. The three PPARs α, β/δ, and γ differ in tissue distribution and ligand selectivity [11]. PPARα, expressed in the liver and a number of other tissues including brown adipose tissue and heart, upregulates the expression of genes involved in gluconeogenesis, β-oxidation, and lipid transport. Selective deletion of PPARα in hepatocytes results in hepatic lipid accumulation [12].

PPARδ, also widely expressed in many tissues including the liver, decreases hepatic gluconeogenesis, fatty acid oxidation, improves insulin sensitivity, and inhibits activation of macrophage and Kupffer cells [13]. Recently, a PPARδ agonist MBX-8025 was shown to abolish lipotoxicity and ameliorate NASH in a diabetic mouse model [14]. Elafibranor (GFT-505) is a dual PPARα/δ agonist which has been shown to improve liver, adipose tissue, and peripheral tissue insulin sensitivity and reduce alanine aminotransferase (ALT) levels in patients with metabolic syndrome [15]. In a phase 2b randomized double blind placebo controlled trial (RDBPCT) to study the effect of elafibranor on NASH (GOLDEN-505), 276 patients with biopsy-proven noncirrhotic NASH were randomized to 80 mg/day or 120 mg/day of elafibranor or placebo for 1 year [16■■]. The primary end point, selected as histological resolution of NASH without worsening of fibrosis, was achieved in 23, 21, and 17% of patients who received 80 mg/day, 120 mg/day, and placebo, respectively. There was no statistically significant difference between the groups. Using a more stringent criteria for resolution of NASH, 19% of study participants on elafibranor 120 mg/day and 12% of study participants on placebo achieved NASH resolution (P = 0.045). The inability to demonstrate benefit was thought to be due to the high placebo response rates in study participants with mild to moderate NASH [NAFLD activity score (NAS) 3–5]. Exclusion of study participants with mild disease at baseline showed that the 120 mg/day dose was statistically superior to placebo for both definitions of NASH resolution. Based on these results, a phase 3 trial is currently recruiting NASH study participants with NAS >4 who will be randomized to elafibranor 120 mg/day versus placebo for 72 weeks. Histological primary end point of NASH resolution without worsening of fibrosis, together with a clinical coprimary composite end point based on mortality, cirrhosis, and liver-related outcomes will be assessed (NCT02704403).

PPARγ is primarily expressed in adipose tissue and regulates glucose metabolism, lipogenesis, and adipose tissue differentiation. Thiazolidinediones, including pioglitazone, are PPARγ agonists used in the treatment of diabetes and demonstrated to be effective in NASH [17]. The glitazars are dual PPARα/γ agonists which aim to combine the beneficial effects of activating both PPAR receptors. Saroglitazar, currently the only glitazar in clinical use because of safety concerns with other members of the category, has been shown to improve diabetic dyslipidemia [18,19] and is currently approved in India for this indication. In a mouse model of NASH, saroglitazar was found to reduce steatosis and ALT, and improve liver histology [20]. A subsequent retrospective study of NAFLD patients with dyslipidemia treated with saroglitazar for 24 weeks showed a significant decrease in ALT compared with baseline [21]. A phase 2 open-label study (PRESS VIII) evaluated the effectiveness of saroglitazar among 32 patients with biopsy-proven NASH [22]. After 12 weeks of treatment, a 52% decrease in ALT was shown. A phase 3 RDBPCT is currently ongoing in India to assess the effect of saroglitazar versus placebo for 52 weeks in biopsy-proven noncirrhotic NASH (Clinical Trials Registry-India CTRI/2015/10/006236).

Farnesoid X receptor

Bile acids can negatively regulate bile acid synthesis, decrease hepatic gluconeogenesis, and lipogenesis through interaction with their intracellular receptor, the farnesoid X receptor (FXR). A synthetic bile acid agonist of FXR, obeticholic acid (OCA; 6-ethyl-chenodeoxycholic acid) was evaluated in a phase 2b clinical trial (FLINT) in which 283 study participants with biopsy-proven noncirrhotic NASH (NAS >4) were randomized to OCA 25 mg/day versus placebo for 72 weeks [23■■]. The primary end point of histological improvement, demonstrated as reduction in NAS by two or more points, with no worsening of fibrosis was reached in 45% of study participants on OCA versus 21% of those on placebo (P = 0.0002). Resolution of NASH was demonstrated in 22% of OCA study participants versus 13% of placebo (P = 0.08); and fibrosis score decreased in 35% of OCA study participants versus 19% of placebo (P = 0.004). Study participants on OCA showed a significant decrease in BMI compared to those on placebo (BMI decrease by 0.7 kg/m3 versus gain of 0.1 kg/m3, respectively). OCA treatment, however, decreased high-density lipoprotein cholesterol, while increasing low-density lipoprotein cholesterol, and total cholesterol. These changes in cholesterol occurred primarily at the initiation of the study and improved with continued treatment; whether these changes translate into increased cardiovascular risk remains to be demonstrated. A phase 3 trial to compare the effectiveness of 72 weeks of OCA versus placebo for noncirrhotic biopsy-proven NASH is in its recruitment stages (NCT02548351). A primary histological end point of decreased NAFLD activity or improvement in fibrosis will be assessed. Current pivotal trials for precirrhotic stages of NASH require long-term extension trials to demonstrate that such short-term histological benefits translate into decreased progression to cirrhosis, considered a generally accepted surrogate for full approval by regulatory agencies [24■■].

Incretins, dipeptidyl peptidase-4 inhibitors and sodium–glucose cotransporter 2 inhibitors

Glucagon-like peptide (GLP-1), secreted by intestinal L-cells in response to meal ingestion, improves insulin sensitivity, and increases hepatic glucose uptake and glycogen production [25]. GLP-1 receptor agonists or incretin mimetics, including exenatide and liraglutide are approved for the management of type 2 diabetes mellitus [26]. Recently, liraglutide was investigated in a phase 2 RDBPCT (LEAN trial) to determine the effectiveness of 48 weeks of liraglutide (1.8 mg/day) versus placebo on biopsy-proven NASH [27■■]. The primary end point was histological resolution of NASH without worsening of fibrosis. At the end of the study period, the primary end point was reached by 39% of study participants on liraglutide versus 9% on placebo (P = 0.02). Study participants on liraglutide had an average weight loss of 5.3 kg, with histological responders losing an average of 2.1 kg more than histological nonresponders.

GLP-1 activity can also be augmented by inhibition of dipeptidyl peptidase 4 (DPP-4), an enzyme that degrades GLP-1. Sitagliptin and vildagliptin are DPP-4 inhibitors which have been shown previously to modestly decrease liver fat as measured by magnetic resonance spectroscopy after 24 weeks of treatment [28]. Recently, a RDBPCT in 50 NAFLD patients with prediabetes or early diabetes did not show any improvement in liver fat, liver enzymes, or fibrosis in study participants on sitagliptin (100 mg/day) versus placebo [29]. Based on currently available data, inhibition of DPP-4 does not appear to be beneficial in the treatment of NASH.

The newest class of diabetic medications on the market are sodium–glucose cotransporter 2 (SGLT-2) inhibitors. A recent retrospective study evaluated the effectiveness of SGLT-2 inhibitor, ipragliflozin (50 mg/day), on liver enzymes and fibrosis index (FIB-4) in 50 diabetic NAFLD patients [30]. Over an average follow-up of 451 days, there was a significant decrease in body weight, ALT and FIB-4 compared with baseline values. The average weight loss in patients who achieved normal ALT was 3.94 kg, compared with 1.98 kg in study participants who did not normalize their ALT. Further studies are needed to shed light on the utility of SGLT-2 inhibitors in the treatment of NAFLD.

3-Hydroxy-3-methyl-glutaryl-CoA reductase inhibitors

The 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors, popularly known as statins, are safe in patients with NAFLD and other chronic liver diseases [31]. However, a recent study demonstrated the underutilization of statins in patients with NAFLD [32]. A prospective trial in 20 patients with biopsy-proven NASH and dyslipidemia determined the effect of 12 months of rosuvastatin (10 mg/day) on liver histology. In total, 19 out of the 20 patients enrolled demonstrated complete resolution of NASH despite no change in weight compared with baseline [33]. Such data are hard to reconcile with the findings that the majority of study participants in large multicenter cohorts such as the NASH CRN are on statins and yet have severe liver disease. If there is a beneficial effect, the effect size is likely to be modest.

De-novo lipogenesis

Acetyl-CoA carboxylase (ACC) catalyzes the carboxylation of acetyl-CoA to malonyl-CoA, which serves as a building block for fatty acid synthesis while inhibiting fatty acid β-oxidation. In a murine model of NAFLD, inhibition of ACC decreased lipogenesis and hepatic steatosis and improved insulin sensitivity. Recently, a Phase 1 trial in obese but otherwise healthy male volunteers showed dose-dependent inhibition of de-novo lipogenesis by the liver-directed synthetic ACC inhibitor, NDI-010976 [34], thus providing the basis for further studies on ACC inhibition as a potential therapy for NAFLD. The fatty acid-bile acid conjugate aramchol inhibits steroyl CoA desaturase and has been shown to produce a dose-dependent decrease in hepatic steatosis using noninvasive measures [35]. A phase 2b trial of Aramchol (400 and 600 mg/day) in patients with biopsy-proven NASH is currently underway (NCT02279524).

OXIDATIVE STRESS AND INFLAMMATION

Hepatic steatosis is characterized by increased fatty acid β-oxidation and oxidative stress, leading to generation of reactive oxygen species, mitochondrial defect and dysfunction, alteration of cell cycle regulation, and decreased cell viability [36,37]. Targeting of pathways involved in oxidative stress and inflammatory response have shown utility as therapy for NASH.

Antioxidants

The fat-soluble antioxidant vitamin E has been shown to be superior to placebo in achieving histological response and resolution of NASH in a phase 3 RDBPCT (PIVENS) [38]. After 96 weeks of treatment, histological response was achieved in 43% of study participants on vitamin E (800 IU/day), compared with 19% of placebo study participants (P = 0.001). Approximately half of the study participants on vitamin E demonstrated reduction in hepatocyte ballooning and lobular inflammation. Vitamin E had no effect on fibrosis. Despite the favorable safety profile of vitamin E in the PIVENS trial, other studies suggest an increase in all-cause mortality [39] and prostate cancer [40] in study participants on vitamin E; observations that have not been supported by subsequent analyses [41,42]. In a recent study that pooled together data from the PIVENS trial and the placebo arm of the FLINT trial to determine the efficacy of vitamin E in diabetic versus nondiabetic NASH study participants, there was similar improvement in NASH histology in both groups [43]. There was no increase in the incidence of adverse events in study participants treated with vitamin E. Based on demonstrated efficacy in improving the histological features of NASH, vitamin E is currently recommended as first line off-label pharmacotherapy for NASH [44,45].

Cysteamine, an aminothiol that scavenges reactive oxygen species, was shown to improve levels of ALT and AST after 24 weeks of treatment in a small pilot study of 11 children with elevated ALT [46]. In a recent multicenter RDBPCT (CyNCh), 169 children with biopsy-proven NASH (NAS >4) were randomized to 12 months of cysteamine (300 mg for study participants ≤65 kg; 375 mg for study participants 65–80 kg; 450 mg for study participants >80 kg) versus placebo. Although study participants treated with cysteamine showed statistically significant decrease in ALT and lobular inflammation, there was no difference in overall histologic markers of NAFLD or in NAS [47]. A post hoc analysis of study participants who weighed less than 65 kg showed that 50% of those in the treatment arm reached the primary outcome of histological improvement, compared with 13% of placebo (P = 0.005). Despite the inability to demonstrate histological response overall in the treatment arm, the results highlight several important questions that were raised in an accompanying commentary [48], including the heterogenous nature of pediatric NASH, the lack of robust data on the natural history of NASH in children, and the effect of genetic polymorphisms including patatin-like phospholipase domain-containing protein 3 (PNPLA3) on NASH treatment outcomes.

Immune modulators

Inflammatory cytokines including C-C chemokine ligands type 2 and type 5 (CCL2-CCL5), which are involved in activation and migration of inflammatory cells into the liver and propagation of fibrosis, have been found to be upregulated in NASH. Cenicriviroc, an oral antagonist of the CCL2–CCL5 receptor, showed anti-inflammatory and antifibrotic activity in animal models of fibrosis [49] and decreased serum fibrotic markers when used for treatment of HIV infection in adults without liver disease [50]. An ongoing phase 2a study of cenicriviroc (ORION) is aimed at assessing the effect of 24 weeks of treatment on insulin sensitivity, liver enzymes, and liver imaging in obese patients with insulin resistance and suspected NAFLD (NCT02330549). At the same time, a phase 2b trial (CENTAUR) is investigating the effect of 2 years of cenicriviroc (150 mg daily) or placebo on noncirrhotic NASH and liver fibrosis in patients with T2DM or metabolic syndrome (NCT02217475). Interim analysis at year 1 of the CENTAUR study, in which 289 study participants were randomized, showed twice as many patients with at least one stage improvement in fibrosis and no worsening of steatohepatitis in the treatment group, compared with placebo (P = 0.023) [51]. A similar proportion of patients in the cenicriviroc versus placebo arms achieved improvements in NAS and resolution of steatohepatitis [52]. A phase 3 study (STELLARIS) to evaluate the efficacy and safety of cenicriviroc in patients with NASH fibrosis is expected to start recruitment in 2017 (NCT03028740).

Apoptosis and tumor necrosis factor α

NASH is characterized by enhanced activation of caspases and proinflammatory cytokines (including tumor necrosis factor α) that drive apoptosis and propagate liver injury [53]. Emricasan, an oral pan-caspase inhibitor, improves inflammation, hepatocyte injury, and hepatic fibrosis in mice fed high-fat diet without any effects on hepatic steatosis or features of the metabolic syndrome [54]. In a recent phase 2 RDBPCT of 38 study participants with noncirrhotic NAFLD, 28 days of emricasan (25 mg twice daily) resulted in a substantial decrease in liver enzymes and cytokeratin 18 fragments, a surrogate of liver apoptosis [55]. A phase 2b trial of emricasan versus placebo (ENCORE-NF) is currently ongoing to evaluate the efficacy of 72 weeks of emricasan (10 mg per day or 100 mg per day) in patients with biopsy-proven NASH. The primary outcome is improvement in fibrosis without worsening of NASH (NCT02686762).

The apoptosis signal-regulating kinase (ASK1), also known as mitogen-activated protein kinase kinase kinase 5, is activated by tumor necrosis factor α, oxidative or endoplasmic reticulum stress, leading to activation of the p38 MAPK/JNK pathway, and resulting in hepatocyte apoptosis and fibrosis [53]. Inhibition of ASK1 reduces liver steatosis and fibrosis in a murine model of diet-induced NASH [56]. An open-label phase 2 trial in 72 NASH patients with stage 2/3 fibrosis randomized to an oral ASK1 inhibitor, selonsertib (formerly called GS-4997; 6 mg or 18 mg/day) versus lysyl oxidase-like 2 antibody simtuzumab (25 mg SC weekly) versus selonsertib and simtuzumab was recently completed [57]. Preliminary analysis showed that patients who received selonsertib (with or without simtuzumab) were more likely to demonstrate decreased hepatic steatosis, decreased fibrotic stage and at least 15% decrease in liver stiffness on magnetic resonance elastography, compared with simtuzumab alone. Antisteatotic and antifibrotic effects of selonsertib were dose dependent [57].

ANTIFIBROTICS

Antifibrotics in NASH aim to counteract progressive fibrosis and resultant complications through blockage of fibrotic pathways or by promoting reversal of fibrosis [58].

Simtuzumab

The lysyl oxidase-like 2 antibody simtuzumab is currently in a phase 2b trial in NASH patients with advanced fibrosis but without cirrhosis (NCT01672866). Study participants are randomized to biweekly SC injections of simtuzumab (75 or 120 mg) versus placebo for 96 weeks, followed by an additional 240 weeks of open-label phase. Simtuzumab is also being investigated in a phase 2b trial in NASH patients with compensated cirrhosis (NCT01672879). The primary end point being assessed is mean change in hepatic venous pressure gradient as well as event-free survival.

Galectin-3

Galectin-3 is expressed primarily in immune cells and is crucial for the development of liver fibrosis. A galectin-3 inhibitor, GR-MD-02, was previously found to decrease disease activity and fibrosis in a murine model [59,60]. A currently ongoing phase 2 study in patients with NASH and advanced fibrosis is evaluating the effect of 16 weeks of drug on hepatic fibrosis as assessed by MRI (NCT02421094). Another phase 2 study is recruiting patients with NASH cirrhosis and portal HTN to assess the efficacy of 1-year treatment of GR-MD-02 in reducing hepatic venous pressure gradient (NCT02462967).

CONCLUSION

There are currently a number of drugs undergoing pivotal trails as potential therapy for NASH. It is anticipated that the first drugs to be approved for NASH will likely become available by 2020. Approval of these agents should herald future trials of combination therapy to prevent NASH progression to cirrhosis and reduce liver-related outcomes.

KEY POINTS.

  • NASH can progress to cirrhosis and liver cancer and has become a leading cause for chronic liver disease worldwide. It is imperative that effective pharmacotherapies are developed to treat NASH and prevent progression to end-stage liver disease.

  • Vitamin E and pioglitazone currently remain the first-line off label drugs for NASH. Many agents are currently in intermediate or advanced stages of development, including OCA, elafibranor, and cenicriviroc.

  • The intestinal microbiome and metabolic endotoxemia are targets that are actively being explored for the development of novel drugs.

  • It is anticipated that by 2020, some of the agents currently undergoing pivotal trials would be approved for treatment of NASH.

Acknowledgments

None.

Financial support and sponsorship

The work was supported by a training grant T32 DK 7150–40 from NIDDK to A. J. S.

A. J. S. is the President of Sanyal Bio and has stock options in Genfit, NewCo LLC, Akarna, Indalo, and Exhalenz. He has been a paid consultant to Pfizer, Conatus, Novartis, Lilly, Hemoshear, and Salix. He is an unpaid consultant to Intercept, Tobira, Merck, Bristol Myers Squibb, Nitto Denko, Novo Nordisk, Nordic Bio-Science, Syntlogic, Canfite, Jannsen, Gilead, and Galectin. His institution has received grant support from Merck, Astra Zeneca, Bristol Myers, Novartis, Shire, and Conatus.

Footnotes

Conflicts of interest

There are no conflicts of interest.

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