ESPN 54th Annual Meeting

ESPN 2022


 
Novel cellular model of inhibition of glycolate oxidase dependent oxalate production by BBP-711
THULASHITHA RAJASINGHAM 1 ANDY WHITNEY 2 JUSTIN LAFOUNTAINE 1 UMA SINHA 1

1- CANTERO THERAPEUTICS, A BRIDGEBIO COMPANY
2- APPLIED MOLECULAR TRANSPORT
 
Introduction:

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disorder characterized by overproduction of oxalate. Glycolate oxidase (GO) is a logical target for inhibition as substrate reduction therapy for PH1. BBP-711 is a small molecule inhibitor of GO in development for the treatment of PH1. The purpose of this study was to evaluate the in vitro activity of BBP-711 to inhibit GO-dependent production of oxalate in liver cells.

Material and methods:

Western blot analysis was used to confirm expression of GO in HepaRG cells and immunohistochemistry was used to confirm localization of GO in peroxisomes. Inhibitory potency of BBP-711 was measured in cultured confluent HepaRG cells over a 7-day period while 5 mM of glycolate was used to enhance oxalate production. Given the structural similarity of the substrate binding sites of GO and lactate dehydrogenase A (LDHA), BBP-711 activity was evaluated with purified LDHA to exclude off-target effects.

Results:

GO expression in HepaRG cells was confirmed by western blot analysis. Colocalization of GO and the peroxisome marker catalase was confirmed by immunohistochemistry of the cells. BBP-711 demonstrated dose-dependent inhibition of oxalate production by HepaRG cells over the duration of the experiment (mean IC50 value ± SD of 414 ± 200 nM, 521 ± 47, 481 ± 69 nM at 24 hours, 48 hours and 72 hours, respectively). In vitro assays demonstrated that relative to its inhibitory potency against GO (IC50= 15.4 nM), BBP-711 demonstrated only marginal inhibition (>10%) of LDHA at a much higher concentration (10 µM).

Conclusions:

This novel cellular assay demonstrates the localization of GO in the peroxisome and the ability of BBP-711 to inhibit peroxisomal GO-mediated oxalate production at therapeutic target concentrations.