Ursodeoxycholic acid in the treatment of primary sclerosing cholangitis

Novel preclinical developments of the primary sclerosing cholangitis treatment landscape

INTRODUCTION

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease associated with inflammation, fibrosis, and destruction of intra- and extrahepatic bile ducts. Despite substantial recent advances in our understanding of PSC, the only proven treatment of PSC is liver transplantation. There is an urgent unmet need to find medical therapies for this disorder.

AREAS COVERED

Multiple drugs are currently under evaluation as therapeutic options for this disease. This article summarizes the literature on the various novel therapeutic options that have been investigated and are currently under development for the treatment of PSC.

EXPERT OPINION

In the next decade, more than one drug will likely be approved for the treatment of the disease, and we will be looking at combination therapies for the optimal management of the disease.

Machine-Learning-Guided Engineering of an NADH-Dependent 7β-Hydroxysteroid Dehydrogenase for Economic Synthesis of Ursodeoxycholic Acid

Enzymatic synthesis of ursodeoxycholic acid (UDCA) catalyzed by an NADH-dependent 7β-hydroxysteroid dehydrogenase (7β-HSDH) is more economic compared with an NADPH-dependent 7β-HSDH when considering the much higher cost of NADP+/NADPH than that of NAD+/NADH. However, the poor catalytic performance of NADH-dependent 7β-HSDH significantly limits its practical applications. Herein, machine-learning-guided protein engineering was performed on an NADH-dependent Rt7β-HSDHM0 from Ruminococcus torques. We combined random forest, Gaussian Naïve Bayes classifier, and Gaussian process regression with limited experimental data, resulting in the best variant Rt7β-HSDHM3 (R40I/R41K/F94Y/S196A/Y253F) with improvements in specific activity and half-life (40 °C) by 4.1-fold and 8.3-fold, respectively. The preparative biotransformation using a "two stage in one pot" sequential process coupled with Rt7β-HSDHM3 exhibited a space-time yield (STY) of 192 g L-1 d-1, which is so far the highest productivity for the biosynthesis of UDCA from chenodeoxycholic acid (CDCA) with NAD+ as a cofactor. More importantly, the cost of raw materials for the enzymatic production of UDCA employing Rt7β-HSDHM3 decreased by 22% in contrast to that of Rt7β-HSDHM0, indicating the tremendous potential of the variant Rt7β-HSDHM3 for more efficient and economic production of UDCA.

Emerging therapies in primary sclerosing cholangitis: pathophysiological basis and clinical opportunities

Primary sclerosing cholangitis (PSC) is a progressive liver disease, histologically characterized by inflammation and fibrosis of the bile ducts, and clinically leading to multi-focal biliary strictures and with time cirrhosis and liver failure. Patients bear a significant risk of cholangiocarcinoma and colorectal cancer, and frequently have concomitant inflammatory bowel disease and autoimmune disease manifestations. To date, no medical therapy has proven significant impact on clinical outcomes and most patients ultimately need liver transplantation. Several treatment strategies have failed in the past and whilst prescription of ursodeoxycholic acid (UDCA) prevails, controversy regarding benefits remains. Lack of statistical power, slow and variable disease progression, lack of surrogate biomarkers for disease severity and other challenges in trial design serve as critical obstacles in the development of effective therapy. Advances in our understanding of PSC pathogenesis and biliary physiology over recent years has however led to a surge of clinical trials targeting various mechanistic compartments and currently raising hopes for imminent changes in patient management. Here, in light of pathophysiology, we outline and critically evaluate emerging treatment strategies in PSC, as tested in recent or ongoing phase II and III trials, stratified per a triad of targets of nuclear and membrane receptors regulating bile acid metabolism, immune modulators, and effects on the gut microbiome. Furthermore, we revisit the UDCA trials of the past and critically discuss relevant aspects of clinical trial design, including how the choice of endpoints, alkaline phosphatase in particular, may affect the future path to novel, effective PSC therapeutics.

The use of obeticholic acid for the management of non-viral liver disease: current clinical practice and future perspectives

Farnesoid X nuclear receptor is involved in the regulation of lipid and glucose metabolism, though mainly in the homeostasis of bile acids. Indeed, the agonists of farnesoid X nuclear receptor represent promising drugs. Areas covered: Obeticholic acid, a novel semisynthetic analogue of the naturally occurring bile acid, has led to encouraging preliminary results in both cholestatic and metabolic liver disease. In patients with primary biliary cholangitis, obeticholic acid determines a significant biochemical improvement although the effects on liver fibrosis are lacking. Obeticholic acid has been suggested for the treatment of nonalcoholic liver disease with good laboratory results. In cirrhotic animal models, the drug seems to reduce both portal hypertension and gut bacterial translocation. Expert commentary: The use of obeticholic acid for the treatment of primary biliary cholangitis shows satisfying results. However, some open questions remain unresolved. Herein, we provide an overview of the current knowledge about the use of obeticholic acid in the field of nonviral chronic liver diseases. We tried to give a global point of view using a translational approach.

Cholestatic liver disease

The care of the patient with cholestasis hinges on identifying the etiology, treating reversible causes, and managing chronic cholestatic processes. PBC and PSC are important causes of chronic cholestasis, and are the most common causes of cholestatic liver disease. Effective therapy is available for patients with PBC, whereas none exists for patients with PSC. Awareness of the complications that may be associated with cholestasis and implementing the appropriate management are essential.

Care of the cholestatic patient

Cholestasis is defined as impairment of bile formation or bile flow. Care of the patient with cholestatic features is dependent on identifying the cause of the cholestasis, initiating appropriate treatment of reversible conditions, and the recognition and management of cholestasis-specific complications. Cholestasis may include extrahepatic ducts and intrahepatic bile ducts, or may be limited to one or the other. Jaundice and pruritus are the hallmarks of cholestasis clinically but biochemical evidence may, and often does, precede the clinical manifestations.

Current and future anti-fibrotic therapies for chronic liver disease

Chronic injury results in a wound healing response that eventually leads to fibrosis. The response is generalized, with features common among multiple organ systems. In the liver, various different types of injury lead to fibrogenesis, implying a common pathogenesis. Although several specific therapies for patients who have different liver diseases have been successfully developed, including antiviral therapies for those who have hepatitis B and hepatitis C virus infection, specific and effective antifibrotic therapy remains elusive. Over the past 2 decades, great advances in the understanding of fibrosis have been made and multiple mechanisms underlying hepatic fibrogenesis uncovered. Elucidation of these mechanisms has been of fundamental importance in highlighting novel potential therapies. Preclinical studies have indicated several putative therapies that might abrogate fibrogenesis. This article emphasizes mechanisms underlying fibrogenesis and reviews available and future therapeutics.

New therapies in hepatitis C virus and chronic liver disease: antifibrotics

Fibrotic liver disease occurs after any of the various forms of injury to the liver. Fibrosis is a critical factor leading to hepatic dysfunction and portal hypertension and its complications. The fibrogenic cascade is complex but leads to accumulation of extracellular matrix proteins, followed by nodular fibrosis, tissue contraction, and alteration in blood flow. A critical concept emerging is that activation of effector cells, which produce extracellular matrix, underlies the fibrogenic process. The aggregate data has not only helped lead to an understanding of the pathophysiologic basis of hepatic fibrogenesis, but it has also provided an important context with which to base novel antifibrotic therapy.

Antifibrotic therapy in chronic liver disease

The response to injury is one of wound healing and, subsequently, fibrosis. This response is generalized, occurring in diverse organ systems. Injury and wounding in the liver ultimately lead to cirrhosis in many patients (although not all patients), and are the result of many different diseases. The fact that various diseases result in cirrhosis suggests a common pathogenesis. Study over the past 2 decades has shed considerable light on the pathogenesis of fibrosis and cirrhosis. A growing body of literature indicates that the hepatic stellate cell is a central component in the fibrogenic process. Stellate cells undergo a transformation during injury that has been termed activation. Activation is complex and multifaceted, but one of its most prominent features is the synthesis of large amounts of extracellular matrix, resulting in deposition of scar or fibrous tissue. The fibrogenic process is dynamic; it is noteworthy that even advanced fibrosis (or cirrhosis) is reversible. The best antifibrotic therapy is treatment of the underlying disease. For example, eradication of hepatitis B or C virus can lead to the reversal of fibrosis. In situations in which treating the underlying process is not possible, specific antifibrotic therapy is desirable. A number of specific antifibrotic therapies have been tried, but have been met with poor or mediocre success. However, elucidation of the mechanisms responsible for fibrogenesis, with particular emphasis on stellate cell biology, has highlighted many putative novel therapies. This article emphasizes mechanisms underlying fibrogenesis, and reviews current antifibrotic therapies as well as potential future approaches.

Cellular distribution of thrombomodulin as an early marker for warm ischemic liver injury in porcine liver transplantation: protective effect of prostaglandin I2 analogue and tauroursodeoxycholic acid

BACKGROUND

Warm ischemia of the graft from non-heart-beating donors is considered a risk factor for posttransplant graft dysfunction. The early administration of cytoprotective agents may help improve graft dysfunction.

METHODS

Four groups of 10 pigs each underwent orthotopic liver transplantation. Prostaglandin I2 analogue, OP-41483, was administered intraportally 30 min before warm ischemic insult in donors and after reperfusion in recipients in one group. In the other study group, additional intravenous tauroursodeoxycholic acid (TUDC) was given before the warm ischemic insult in donors and after reperfusion, then maintained continuously until postoperative day (POD) 7.

RESULTS

Exposure of liver grafts to warm ischemia resulted in severe congestion with the disappearance of thrombomodulin (Tm) from the sinusoidal endothelial cells (SECs) and smooth muscle cells (SMCs) around biliary epithelial cells (BEpCs) 2 hr after reperfusion, followed by positive immunoreactivity of Tm in BEpCs with hyperbilirubinemia, which was related to high mortality. Combined administration of OP-41483 and TUDC had a protective effect, demonstrated by sustained immunoreactivity of Tm from SECs and SMCs until POD 7, without that reactivity in BEpCs. This was associated with reduced congestion and hyperbilirubinemia, similar to the control group not subjected to warm ischemia.

CONCLUSIONS

These findings suggest that negative immunoreactivity of Tm in SECs and SMCs surrounding BEpCs and positive in BEpCs may be an early marker for ischemic liver injury, and that OP-41483 and TUDC may protect against the microcirculatory and biliary derangement.

Efficacy of ursodeoxycholic acid in the treatment of primary sclerosing cholangitis in children

BACKGROUND

Ursodeoxycholic acid (UDCA) has been shown to be beneficial in reducing disease activity in adult patients with primary sclerosing cholangitis (PSC). However, there has been little published regarding PSC in children and no studies investigating the efficacy of UDCA as a treatment for PSC.

METHODS

This retrospective study included 10 children who were found to have the diagnosis of PSC during the past 15 years at the Texas Children's Hospital and Herman Hospital, both in Houston, Texas. The male:female ratio was 8:2, the median age of onset was 12 years (range, 1-17 years), and eight patients had coexistent inflammatory bowel disease (IBD; six ulcerative colitis, one Crohn's disease, one unspecified). At the time of diagnosis, five patients were asymptomatic, all of whom had IBD with elevated liver enzymes and three of whom had hepatomegaly. Nine patients were treated with UDCA. The one patient who did not receive UDCA was lost to follow-up soon after diagnosis. The mean dose of UDCA was 17 mg/kg with the doses ranging from 9 to 37 mg/kg.

RESULTS

There were no side effects from the medication recorded for any of the patients. These patients showed a significant reduction in alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transferase at 1, 3, 6, 15, and 20 months after treatment.

CONCLUSIONS

This study demonstrates that children with PSC treated with UDCA have significant improvements in liver biochemical indices. However, the long-term effect of UDCA on clinical outcome is unknown.

The cell and molecular biology of hepatic fibrogenesis. Clinical and therapeutic implications

Much has been learned in the past 2 decades about the cellular and molecular mechanisms underlying hepatic fibrogenesis and about potential therapeutic approaches in patients with liver disease. The central event in fibrogenesis seems to be the activation of hepatic stellate cells. Stellate cell activation is characterized by several important features, including enhanced matrix synthesis and a prominent contractile phenotype, processes that probably contribute to the physical distortion and dysfunction of the liver in advanced disease. It is important to emphasize that the factors controlling activation are multifactorial and complex. The extracellular matrix is a dynamic, active constituent of the fibrogenic response and undergoes active remodeling, including synthesis and degradation. Effective therapy for hepatic fibrogenesis will probably also be multifactorial, based on the basic mechanisms underlying the fibrogenic process. The most effective therapies will probably be directed at the stellate cell. Approaches that address matrix remodeling (i.e., by enhancing matrix degradation or by inhibiting factors that prevent matrix breakdown) may be effective.

Bile acid abnormalities in cholestatic liver diseases

There is ample reason to believe that UDCA is the drug of choice in cholestatic liver diseases. It is possible that UDCA has to be administered for prolonged periods to see appreciable reversal in liver damage. Nevertheless, the amelioration of symptoms and improvement in nutrition of patients are equally important. Disabling symptoms such as pruritus are often brought under control, and quality of life improves. Clearly the goal for UDCA therapy is to slow the rate of disease progression, lessen the mortality risk, and improve the quality of life in patients. It is possible that a combination therapy would be more beneficial than UDCA alone. Initial results of administering UDCA with colchicine have shown no improvement in liver histology; however, administration of UDCA together with a strong anti-inflammatory drugs may be helpful to halt immune destruction of liver cells.