Miglustat, a glucosylceramide synthase inhibitor, mitigates liver fibrosis through TGF-β/Smad pathway suppression in hepatic stellate cells

Transforming growth factor (TGF)-β/Smad pathway is implicated in the pathogenesis of liver fibrosis, a condition characterized by excessive deposition of extracellular matrix (ECM) proteins such as collagen in response to chronic inflammation. It has been reported that ceramide regulates collagen production through TGF-β/Smad pathway activation. In this study, we examined whether miglustat, an inhibitor of glucosylceramide synthase, can suppress liver fibrosis by reducing TGF-β/Smad pathway activity. Human hepatic stellate cells (HHSteCs) were cultured with TGF-β and multiple miglustat concentrations to examine dose-dependent effects on the expression levels of ECM-related genes and Smad proteins. To evaluate the efficacy of miglustat for fibrosis mitigation, C57BL/6 mice were treated with carbon tetrachloride (CCl₄) for 4 weeks to induce liver fibrosis, followed by combined CCl₄ plus miglustat for a further 2 weeks. To examine if miglustat can also prevent fibrosis, mice were treated with CCl₄ for 2 weeks, followed by CCl₄ plus miglustat for 2 weeks. Miglustat dose-dependently downregulated expression of α-smooth muscle actin and ECM components in TGF-β-treated HHSteCs. Both phosphorylation and nuclear translocation of Smad2 and Smad3 were also suppressed by miglustat treatment. Sirius-Red staining and hydroxyproline assays of model mouse liver samples revealed that miglustat reduced fibrosis, an effect accompanied by decreased expression of ECM. Our findings suggest that miglustat can both prevent and reverse liver fibrosis by inhibiting TGF-β/Smad pathway.

A novel glucosylceramide synthase inhibitor attenuates alpha synuclein pathology and lysosomal dysfunction in preclinical models of synucleinopathy

Mutations in the lysosomal enzyme glucocerebrosidase (GCase, GBA1 gene) are the most common genetic risk factor for developing Parkinson's disease (PD). GCase metabolizes the glycosphingolipids glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph). Mutations in GBA1 reduce enzyme activity and the resulting accumulation of glycosphingolipids may contribute to the underlying pathology of PD, possibly via altering lysosomal function. While reduction of GCase activity exacerbates α-synuclein (α-syn) aggregation, it has not been determined that this effect is the result of altered glycosphingolipid levels and lysosome function or some other effect of altering GCase. The glycosphingolipid GlcCer is synthesized by a single enzyme, glucosylceramide synthase (GCS), and small molecule inhibitors (GCSi) reduce cellular glycosphingolipid levels. In the present studies, we utilize a preformed fibril (PFF) rodent primary neuron in vitro model of α-syn pathology to investigate the relationship between glycosphingolipid levels, α-syn pathology, and lysosomal function. In primary cultures, pharmacological inhibition of GCase and D409V GBA1 mutation enhanced accumulation of glycosphingolipids and insoluble phosphorylated α-syn. Administration of a novel small molecule GCSi, benzoxazole 1 (BZ1), significantly decreased glycosphingolipid concentrations in rodent primary neurons and reduced α-syn pathology. BZ1 rescued lysosomal deficits associated with the D409V GBA1 mutation and α-syn PFF administration, and attenuated α-syn induced neurodegeneration of dopamine neurons. In vivo studies revealed BZ1 had pharmacological activity and reduced glycosphingolipids in the mouse brain to a similar extent observed in neuronal cultures. These data support the hypothesis that reduction of glycosphingolipids through GCS inhibition may impact progression of synucleinopathy and BZ1 is useful tool to further examine this important biology.

The effect of the glucosylceramide synthase inhibitor lucerastat on cardiac repolarization: results from a thorough QT study in healthy subjects

BACKGROUND

Fabry disease is a rare inherited glycosphingolipid storage disorder caused by deleterious mutations in the GLA gene coding for the lysosomal enzyme α-galactosidase A. The glucosylceramide synthase inhibitor lucerastat is an iminosugar with potential to provide oral substrate reduction therapy in Fabry disease, regardless of the patient´s underlying mutation. Since lucerastat exhibits systemic exposure and many patients with Fabry disease suffer from rhythm and conduction abnormalities its effects on cardiac repolarization were evaluated in a thorough QT study.

METHODS

In Part A of this randomized, double-blind, placebo-controlled phase 1 study, single oral doses of 2000 and 4000 mg lucerastat were investigated to determine the supratherapeutic dose for Part B. The latter was a four-way crossover study to demonstrate that lucerastat at single oral therapeutic and supratherapeutic doses had no effect on the QTc interval > 10 ms using concentration-QTc modeling as primary analysis. The primary ECG endpoint was placebo-corrected change-from-baseline (ΔΔ) in Fridericia-corrected QTc (ΔΔQTcF). Open-label moxifloxacin served as positive control.

RESULTS

The effect of lucerastat on ΔΔQTcF was predicted as 0.39 ms (90% confidence interval [CI] - 0.13 to 0.90) and 1.69 ms (90% CI 0.33-3.05) at lucerastat peak plasma concentration after dosing with 1000 mg (5.2 µg/mL) and 4000 mg (24.3 µg/mL), respectively. A QTcF effect > 10 ms was excluded up to lucerastat plasma concentrations of approximately 34.0 µg/mL. Lucerastat did not exert an effect on other ECG parameters. Across doses, absorption of lucerastat was rapid, its elimination half-life ranged from 8.0 to 10.0 h, and the pharmacokinetics (PK) of lucerastat were dose-proportional. Moxifloxacin PK were in line with published data and assay sensitivity was demonstrated by the moxifloxacin QTc response. Lucerastat was safe and well tolerated.

CONCLUSIONS

Lucerastat up to a dose of 4000 mg has no clinically relevant liability to prolong the QT interval or any clinically relevant effect on other ECG parameters. This will be an important factor in the overall benefit-risk assessment of lucerastat in the potential treatment of Fabry disease. Trial registration The study was registered with the ClinicalTrials.gov identifier NCT03832452 (February 6th, 2019, https://clinicaltrials.gov/ct2/show/NCT03832452 ) and the EudraCT number 2018-004546-42 (December 17th, 2018).

Carcinogenicity testing of eliglustat in mice and rats

Eliglustat is a novel glucosylceramide synthase inhibitor for long-term oral treatment of type 1 Gaucher disease (GD1), an inherited metabolic disorder. The carcinogenic potential of this drug has been evaluated in lifetime carcinogenicity bioassays in mice and rats. Administration of eliglustat to Swiss CD-1 mice at 0, 10, 25 or 75 mg/kg/day for 104 weeks by dietary admixture did not influence survival or bodyweight evolution, or produce any clinical indication of poor condition. At histopathology, no increases in tumor incidence for any tumor type were attributed to treatment with eliglustat. Systemic exposure to eliglustat was confirmed by a reduction in circulating levels of glucosylceramide. Administration of eliglustat to Sprague-Dawley rats by oral gavage for 105 weeks at 0, 10, 25 or 75 mg/kg/day (males) or 103 weeks at 0, 5, 15 or 50 mg/kg/day (females) did not affect survival rates, but resulted in reduced bodyweight evolution in male rats (-18% at high dose), indicating that the MTD had been achieved. At histopathology, no increases in tumor incidence were attributed to treatment with eliglustat. Systemic exposure was confirmed by toxicokinetic analyses. In conclusion, eliglustat was not carcinogenic to mice or rats in standard lifetime bioassays.