Discovery of Orally Bioavailable FGFR2/FGFR3 Dual Inhibitors via Structure-Guided Scaffold Repurposing Approach.

Fibroblast growth factor receptors (FGFRs) are transmembrane receptor tyrosine kinases that regulate multiple physiological processes. Aberrant activation of FGFR2 and FGFR3 has been linked to the pathogenesis of many tumor types, including cholangiocarcinoma and bladder cancer. Current therapies targeting the FGFR2/3 pathway exploiting small-molecule kinase inhibitors are associated with adverse events due to undesirable inhibition of FGFR1 and FGFR4. Isoform-specific FGFR2 and FGFR3 inhibitors that spare FGFR1 and FGFR4 could offer a favorable toxicity profile and improved therapeutic window to current treatments. Herein we disclose the discovery of dual FGFR2/FGFR3 inhibitors exploiting scaffold repurposing of a previously reported ALK2 tool compound. Structure-based drug design and structure-activity relationship studies were employed to identify selective and orally bioavailable inhibitors with equipotent activity toward wild-type kinases and a clinically observed gatekeeper mutant.

Discovery of Potent and Selective Inhibitors of Wild-Type and Gatekeeper Mutant Fibroblast Growth Factor Receptor (FGFR) 2/3.

Upregulation of the fibroblast growth factor receptor (FGFR) signaling pathway has been implicated in multiple cancer types, including cholangiocarcinoma and bladder cancer. Consequently, small molecule inhibition of FGFR has emerged as a promising therapy for patients suffering from these diseases. First-generation pan-FGFR inhibitors, while highly effective, suffer from several drawbacks. These include treatment-related hyperphosphatemia and significant loss of potency for the mutant kinases. Herein, we present the discovery and optimization of novel FGFR2/3 inhibitors that largely maintain potency for the common gatekeeper mutants and have excellent selectivity over FGFR1. A combination of meticulous structure-activity relationship (SAR) analysis, structure-based drug design, and medicinal chemistry rationale ultimately led to compound 29, a potent and selective FGFR2/3 inhibitor with excellent in vitro absorption, distribution, metabolism, excretion (ADME), and pharmacokinetics in rat. A pharmacodynamic study of a closely related compound established that maximum inhibition of downstream ERK phosphorylation could be achieved with no significant effect on serum phosphate levels relative to vehicle.

Improved efficacy of a next-generation ERT in murine Pompe disease.

Pompe disease is a rare inherited disorder of lysosomal glycogen metabolism due to acid α-glucosidase (GAA) deficiency. Enzyme replacement therapy (ERT) using alglucosidase alfa, a recombinant human GAA (rhGAA), is the only approved treatment for Pompe disease. Although alglucosidase alfa has provided clinical benefits, its poor targeting to key disease-relevant skeletal muscles results in suboptimal efficacy. We are developing an rhGAA, ATB200 (Amicus proprietary rhGAA), with high levels of mannose-6-phosphate that are required for efficient cellular uptake and lysosomal trafficking. When administered in combination with the pharmacological chaperone AT2221 (miglustat), which stabilizes the enzyme and improves its pharmacokinetic properties, ATB200/AT2221 was substantially more potent than alglucosidase alfa in a mouse model of Pompe disease. The new investigational therapy is more effective at reversing the primary abnormality - intralysosomal glycogen accumulation - in multiple muscles. Furthermore, unlike the current standard of care, ATB200/AT2221 dramatically reduces autophagic buildup, a major secondary defect in the diseased muscles. The reversal of lysosomal and autophagic pathologies leads to improved muscle function. These data demonstrate the superiority of ATB200/AT2221 over the currently approved ERT in the murine model.

Glucosylceramide and Glucosylsphingosine Quantitation by Liquid Chromatography-Tandem Mass Spectrometry to Enable In Vivo Preclinical Studies of Neuronopathic Gaucher Disease.

Gaucher disease (GD) is caused by mutations in the GBA1 gene that encodes the lysosomal enzyme acid ß-glucosidase (GCase). Reduced GCase activity primarily leads to the accumulation of two substrates, glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph). Current treatment options have not been shown to ameliorate the neurological pathology observed in the most severe forms of GD, clearly representing an unmet medical need. To better understand the relationship between GlcCer and GlcSph accumulation and ultimately their connection with the progression of neurological pathology, we developed LC-MS/MS methods to quantify GlcCer and GlcSph in mouse brain tissue. A significant challenge in developing these methods was the chromatographic separation of GlcCer and GlcSph from the far more abundant isobaric galactosyl epimers naturally occurring in white matter. After validation of both methods, we evaluated the levels of both substrates in five different GD mouse models, and found significant elevation of brain GlcSph in all five, while GlcCer was elevated in only one of the five models. In addition, we measured GlcCer and GlcSph levels in the brains of wild-type mice after administration of the GCase inhibitor conduritol ß-epoxide (CBE), as well as the nonlysosomal ß-glucosidase (GBA2) inhibitor N-butyldeoxygalactonojirimycin (NB-DGJ). Inhibition of GCase by CBE resulted in elevation of both sphingolipids; however, inhibition of GBA2 by NB-DGJ resulted in elevation of GlcCer only. Taken together, these data support the idea that GlcSph is a more selective and sensitive biomarker than GlcCer for neuronopathic GD in preclinical models.

Coformulation of a Novel Human α-Galactosidase A With the Pharmacological Chaperone AT1001 Leads to Improved Substrate Reduction in Fabry Mice.

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the gene that encodes α-galactosidase A and is characterized by pathological accumulation of globotriaosylceramide and globotriaosylsphingosine. Earlier, the authors demonstrated that oral coadministration of the pharmacological chaperone AT1001 (migalastat HCl; 1-deoxygalactonojirimycin HCl) prior to intravenous administration of enzyme replacement therapy improved the pharmacological properties of the enzyme. In this study, the authors investigated the effects of coformulating AT1001 with a proprietary recombinant human α-galactosidase A (ATB100) into a single intravenous formulation. AT1001 increased the physical stability and reduced aggregation of ATB100 at neutral pH in vitro, and increased the potency for ATB100-mediated globotriaosylceramide reduction in cultured Fabry fibroblasts. In Fabry mice, AT1001 coformulation increased the total exposure of active enzyme, and increased ATB100 levels in cardiomyocytes, cardiac vascular endothelial cells, renal distal tubular epithelial cells, and glomerular cells, cell types that do not show substantial uptake with enzyme replacement therapy alone. Notably, AT1001 coformulation also leads to greater tissue globotriaosylceramide reduction when compared with ATB100 alone, which was positively correlated with reductions in plasma globotriaosylsphingosine. Collectively, these data indicate that intravenous administration of ATB100 coformulated with AT1001 may provide an improved therapy for Fabry disease and thus warrants further investigation.

The pharmacological chaperone AT2220 increases the specific activity and lysosomal delivery of mutant acid alpha-glucosidase, and promotes glycogen reduction in a transgenic mouse model of Pompe disease.

Pompe disease is an inherited lysosomal storage disorder that results from a deficiency in acid α-glucosidase (GAA) activity due to mutations in the GAA gene. Pompe disease is characterized by accumulation of lysosomal glycogen primarily in heart and skeletal muscles, which leads to progressive muscle weakness. We have shown previously that the small molecule pharmacological chaperone AT2220 (1-deoxynojirimycin hydrochloride, duvoglustat hydrochloride) binds and stabilizes wild-type as well as multiple mutant forms of GAA, and can lead to higher cellular levels of GAA. In this study, we examined the effect of AT2220 on mutant GAA, in vitro and in vivo, with a primary focus on the endoplasmic reticulum (ER)-retained P545L mutant form of human GAA (P545L GAA). AT2220 increased the specific activity of P545L GAA toward both natural (glycogen) and artificial substrates in vitro. Incubation with AT2220 also increased the ER export, lysosomal delivery, proteolytic processing, and stability of P545L GAA. In a new transgenic mouse model of Pompe disease that expresses human P545L on a Gaa knockout background (Tg/KO) and is characterized by reduced GAA activity and elevated glycogen levels in disease-relevant tissues, daily oral administration of AT2220 for 4 weeks resulted in significant and dose-dependent increases in mature lysosomal GAA isoforms and GAA activity in heart and skeletal muscles. Importantly, oral administration of AT2220 also resulted in significant glycogen reduction in disease-relevant tissues. Compared to daily administration, less-frequent AT2220 administration, including repeated cycles of 4 or 5 days with AT2220 followed by 3 or 2 days without drug, respectively, resulted in even greater glycogen reductions. Collectively, these data indicate that AT2220 increases the specific activity, trafficking, and lysosomal stability of P545L GAA, leads to increased levels of mature GAA in lysosomes, and promotes glycogen reduction in situ. As such, AT2220 may warrant further evaluation as a treatment for Pompe disease.

The pharmacological chaperone AT2220 increases recombinant human acid α-glucosidase uptake and glycogen reduction in a mouse model of Pompe disease.

Pompe disease is an inherited lysosomal storage disease that results from a deficiency in the enzyme acid α-glucosidase (GAA), and is characterized by progressive accumulation of lysosomal glycogen primarily in heart and skeletal muscles. Recombinant human GAA (rhGAA) is the only approved enzyme replacement therapy (ERT) available for the treatment of Pompe disease. Although rhGAA has been shown to slow disease progression and improve some of the pathophysiogical manifestations, the infused enzyme tends to be unstable at neutral pH and body temperature, shows low uptake into some key target tissues, and may elicit immune responses that adversely affect tolerability and efficacy. We hypothesized that co-administration of the orally-available, small molecule pharmacological chaperone AT2220 (1-deoxynojirimycin hydrochloride, duvoglustat hydrochloride) may improve the pharmacological properties of rhGAA via binding and stabilization. AT2220 co-incubation prevented rhGAA denaturation and loss of activity in vitro at neutral pH and 37°C in both buffer and blood. In addition, oral pre-administration of AT2220 to rats led to a greater than two-fold increase in the circulating half-life of intravenous rhGAA. Importantly, co-administration of AT2220 and rhGAA to GAA knock-out (KO) mice resulted in significantly greater rhGAA levels in plasma, and greater uptake and glycogen reduction in heart and skeletal muscles, compared to administration of rhGAA alone. Collectively, these preclinical data highlight the potentially beneficial effects of AT2220 on rhGAA in vitro and in vivo. As such, a Phase 2 clinical study has been initiated to investigate the effects of co-administered AT2220 on rhGAA in Pompe patients.

Co-administration with the pharmacological chaperone AT1001 increases recombinant human α-galactosidase A tissue uptake and improves substrate reduction in Fabry mice.

Fabry disease is an X-linked lysosomal storage disorder (LSD) caused by mutations in the gene (GLA) that encodes the lysosomal hydrolase α-galactosidase A (α-Gal A), and is characterized by pathological accumulation of the substrate, globotriaosylceramide (GL-3). Regular infusion of recombinant human α-Gal A (rhα-Gal A), termed enzyme replacement therapy (ERT), is the primary treatment for Fabry disease. However, rhα-Gal A has low physical stability, a short circulating half-life, and variable uptake into different disease-relevant tissues. We hypothesized that coadministration of the orally available, small molecule pharmacological chaperone AT1001 (GR181413A, 1-deoxygalactonojirimycin, migalastat hydrochloride) may improve the pharmacological properties of rhα-Gal A via binding and stabilization. AT1001 prevented rhα-Gal A denaturation and activity loss in vitro at neutral pH and 37 °C. Coincubation of Fabry fibroblasts with rhα-Gal A and AT1001 resulted in up to fourfold higher cellular α-Gal A and ~30% greater GL-3 reduction compared to rhα-Gal A alone. Furthermore, coadministration of AT1001 to rats increased the circulating half-life of rhα-Gal A by >2.5-fold, and in GLA knockout mice resulted in up to fivefold higher α-Gal A levels and fourfold greater GL-3 reduction than rhα-Gal A alone. Collectively, these data highlight the potentially beneficial effects of AT1001 on rhα-Gal A, thus warranting clinical investigation.

The pharmacological chaperone 1-deoxygalactonojirimycin reduces tissue globotriaosylceramide levels in a mouse model of Fabry disease.

Fabry disease is an X-linked lysosomal storage disorder caused by a deficiency in alpha-galactosidase A (alpha-Gal A) activity and subsequent accumulation of the substrate globotriaosylceramide (GL-3), which contributes to disease pathology. The pharmacological chaperone (PC) DGJ (1-deoxygalactonojirimycin) binds and stabilizes alpha-Gal A, increasing enzyme levels in cultured cells and in vivo. The ability of DGJ to reduce GL-3 in vivo was investigated using transgenic (Tg) mice that express a mutant form of human alpha-Gal A (R301Q) on a knockout background (Tg/KO), which leads to GL-3 accumulation in disease-relevant tissues. Four-week daily oral administration of DGJ to Tg/KO mice resulted in significant and dose-dependent increases in alpha-Gal A activity, with concomitant GL-3 reduction in skin, heart, kidney, brain, and plasma; 24-week administration resulted in even greater reductions. Compared to daily administration, less frequent DGJ administration, including repeated cycles of 4 days with DGJ followed by 3 days without or every other day with DGJ, resulted in even greater GL-3 reductions that were comparable to those obtained with Fabrazyme. Collectively, these data indicate that oral administration of DGJ increases mutant alpha-Gal A activity and reduces GL-3 in disease-relevant tissues in Tg/KO mice, and thus merits further evaluation as a treatment for Fabry disease.