Real-world experience of maralixibat in Alagille syndrome: Novel findings outside of clinical trials

OBJECTIVE

Maralixibat, an ileal bile acid transporter inhibitor, is the first drug approved by the U.S. Food and Drug Administration for the treatment of cholestatic pruritus in patients aged ≥3 months with Alagille syndrome (ALGS). Approval was based on reductions in pruritus from the pivotal ICONIC trial, information from two additional trials (ITCH and IMAGO), and long-term extension studies. Although participants in these trials met strict inclusion and exclusion criteria, patients have received maralixibat under broader circumstances as part of an expanded access program or commercially. The expanded access and postapproval settings inform a real-world understanding of effectiveness and safety. The objective was to report on the use of maralixibat in the real-world setting in eight patients who otherwise would not have met entrance criteria for the clinical trials, providing unique insights into its effectiveness in the management of ALGS.

METHODS

We reviewed records of patients with ALGS who received maralixibat but would have been excluded from trials due to surgical biliary diversion, reduction of antipruritic/cholestatic concomitant medications, administration of medication through a gastrostomy or nasogastric tube, or use in patients under consideration for transplantation.

RESULTS

Maralixibat appeared to be effective with reductions in pruritus compared to baseline. Consistent with clinical trials, maralixibat was well tolerated without appreciable gastrointestinal complications. Liver enzyme elevations were observed but were interpreted as consistent with normal fluctuations observed in ALGS, with no increases in bilirubin.

CONCLUSION

Maralixibat may be effective and well tolerated in patients with ALGS in broader clinical contexts than previously reported.

Generation of an Alagille syndrome (ALGS) patient-derived induced pluripotent stem cell line (TRNDi032-A) carrying a heterozygous mutation (p.Cys682Leufs*7) in the JAG1 gene

Alagille syndrome (ALGS) is an autosomal dominant, multisystemic disorder due to haploinsufficiency in either the JAG1 gene (ALGS type 1) or the NOTCH2 gene (ALGS type 2). The disease has been difficult to diagnose and treat due to its muti-system clinical presentation, variable expressivity, and prenatal onset for some of the features. The generation of this iPSC line (TRNDi032-A) carrying a heterozygous mutation, p.Cys682Leufs*7 (c.2044dup), in the JAG1 gene provides a means of studying the disease and developing novel therapeutics towards patient treatment.

Regenerative failure of intrahepatic biliary cells in Alagille syndrome rescued by elevated Jagged/Notch/Sox9 signaling

Despite the robust healing capacity of the liver, regenerative failure underlies numerous hepatic diseases, including the JAG1 haploinsufficient disorder, Alagille syndrome (ALGS). Cholestasis due to intrahepatic duct (IHD) paucity resolves in certain ALGS cases but fails in most with no clear mechanisms or therapeutic interventions. We find that modulating jag1b and jag2b allele dosage is sufficient to stratify these distinct outcomes, which can be either exacerbated or rescued with genetic manipulation of Notch signaling, demonstrating that perturbations of Jag/Notch signaling may be causal for the spectrum of ALGS liver severities. Although regenerating IHD cells proliferate, they remain clustered in mutants that fail to recover due to a blunted elevation of Notch signaling in the distal-most IHD cells. Increased Notch signaling is required for regenerating IHD cells to branch and segregate into the peripheral region of the growing liver, where biliary paucity is commonly observed in ALGS. Mosaic loss- and-gain-of-function analysis reveals Sox9b to be a key Notch transcriptional effector required cell autonomously to regulate these cellular dynamics during IHD regeneration. Treatment with a small-molecule putative Notch agonist stimulates Sox9 expression in ALGS patient fibroblasts and enhances hepatic sox9b expression, rescues IHD paucity and cholestasis, and increases survival in zebrafish mutants, thereby providing a proof-of-concept therapeutic avenue for this disorder.

Mouse Models for Diseases in the Cholangiocyte Lineage

Cholangiopathies are an important group of liver diseases affecting the biliary system, and the purpose of this review is to describe how diseases in the biliary system can be studied in mouse models. A particular focus is placed on mouse models for Alagille syndrome, a cholangiopathy with a strong genetic link to dysfunctional Notch signaling. Recently, a number of different genetic mouse models based on various manipulations of the Notch signaling pathway have been generated to study Alagille syndrome, and we discuss the resulting phenotypes, and possible causes for the phenotypic heterogeneity among the various models. In the final section, we provide a more general discussion on how well mouse models can be expected to mimic human liver disease, as well as an outlook toward the need for new technologies that can help us to gain new insights from mouse models for liver disease.

Characterization of a new B-ALL cell line with constitutional defect of the Notch signaling pathway

Notch signaling contribution to B-cell acute lymphoblastic leukemia (B-ALL) development is still under investigation. The serendipitous onset of B-ALL in a patient affected by the germinal Notch mutation-dependent Alagille syndrome allowed us to establish a B-ALL cell line (VR-ALL) bearing a genetic loss of function in components of Notch signaling. VR-ALL is a common-type B-ALL cell line, grows in conventional culture medium supplemented with 10% serum, and gives rise, once injected into immunodeficient NOG mice, to a mouse xenograft model of B-ALL. Exome sequencing revealed deleterious mutations in some components of Notch signaling, including Jagged1, Notch1, and Notch2. In addition, VR-ALL is sensitive both in vitro and in vivo to γ-secretase inhibitors (GSIs) as well as conventional anti-leukemic drugs. For all these reasons, VR-ALL may help to gain more insights into the role of Notch signaling in B-ALL.

Alagille syndrome: clinical perspectives

Alagille syndrome is an autosomal dominant, complex multisystem disorder characterized by the presence of three out of five major clinical criteria: cholestasis with bile duct paucity on liver biopsy, congenital cardiac defects (with particular involvement of the pulmonary arteries), posterior embryotoxon in the eye, characteristic facial features, and butterfly vertebrae. Renal and vascular abnormalities can also occur. Inter- and intrafamilial variabilities in the clinical manifestations are common. We reviewed the clinical features and management as well as the molecular basis of Alagille syndrome.