Substrate reduction therapy for Krabbe disease and metachromatic leukodystrophy using a novel ceramide galactosyltransferase inhibitor

Abstract

Krabbe disease (KD) and metachromatic leukodystrophy (MLD) are caused by accumulation of the glycolipids galactosylceramide (GalCer) and sulfatide and their toxic metabolites psychosine and lysosulfatide, respectively. We discovered a potent and selective small molecule inhibitor (S202) of ceramide galactosyltransferase (CGT), the key enzyme for GalCer biosynthesis, and characterized its use as substrate reduction therapy (SRT). Treating a KD mouse model with S202 dose-dependently reduced GalCer and psychosine in the central (CNS) and peripheral (PNS) nervous systems and significantly increased lifespan. Similarly, treating an MLD mouse model decreased sulfatides and lysosulfatide levels. Interestingly, lower doses of S202 partially inhibited CGT and selectively reduced synthesis of non-hydroxylated forms of GalCer and sulfatide, which appear to be the primary source of psychosine and lysosulfatide. Higher doses of S202 more completely inhibited CGT and reduced the levels of both non-hydroxylated and hydroxylated forms of GalCer and sulfatide. Despite the significant benefits observed in murine models of KD and MLD, chronic CGT inhibition negatively impacted both the CNS and PNS of wild-type mice. Therefore, further studies are necessary to elucidate the full therapeutic potential of CGT inhibition.

The PGRMC1 Antagonist AG-205 Inhibits Synthesis of Galactosylceramide and Sulfatide

“…The present findings may also be of interest in the area of sphingolipidoses [ 54 ], a group of lysosomal storage diseases [ 55 ]. Specific inhibitors of CGT are of interest as potential therapeutics for Krabbe disease and metachromatic leukodystrophy [ 56 ]. AG-205 may serve as a starting compound to develop new specific CGT inhibitors.…”

Substrate Reduction Therapy for Krabbe Disease: Exploring the Repurposing of the Antibiotic D-Cycloserine

“…In another study, after starting with a small screen of lipid inhibitors against CGT, a brain penetrant compound was ultimately developed that was quite selective, i.e., not readily inhibiting other enzymes that utilize related substrates ( 61 ). This compound (S202) was found to significantly prolong the lifespan of twitcher mice, i.e., from a median of 39.5 up to 63.5 days with treatment starting on postnatal day (PND) 15 ( 61 ). In addition, it lowered brain galactosylceramide and psychosine levels, particularly when treatment was started early, i.e., PND 3 ( 61 ).…”

“…This compound (S202) was found to significantly prolong the lifespan of twitcher mice, i.e., from a median of 39.5 up to 63.5 days with treatment starting on postnatal day (PND) 15 ( 61 ). In addition, it lowered brain galactosylceramide and psychosine levels, particularly when treatment was started early, i.e., PND 3 ( 61 ). These impressive results were dampened by the finding that vacuoles developed in both the white and gray matter of normal mice, even at relatively low doses of the drug ( 61 ).…”

“…In addition, it lowered brain galactosylceramide and psychosine levels, particularly when treatment was started early, i.e., PND 3 ( 61 ). These impressive results were dampened by the finding that vacuoles developed in both the white and gray matter of normal mice, even at relatively low doses of the drug ( 61 ). In addition, extensive histopathological alterations were observed in the testes ( 61 ).…”

“…These impressive results were dampened by the finding that vacuoles developed in both the white and gray matter of normal mice, even at relatively low doses of the drug ( 61 ). In addition, extensive histopathological alterations were observed in the testes ( 61 ). The findings of vacuolation, particularly in gray matter, raised the possibility that CGT is performing a previously unknown role, perhaps within astrocytes and/or within other cell types ( 61 ).…”