MO040: Development of BBP-711, a small molecule inhibitor of glycolate oxidase for primary hyperoxaluria type 1 and recurrent kidney stone formers

Abstract

Abstract BACKGROUND AND AIMS BBP-711 is an investigational small molecule inhibitor of glycolate oxidase (GO), currently in development for the treatment of primary hyperoxaluria type 1 (PH1) and recurrent nephrolithiasis. Selection of BBP-711 as a drug candidate followed structural activity optimization and a pharmacological testing strategy that included functional activity in enzyme assays, target engagement in cellular assays and efficacy studies in a rodent model (Agxt−/− mice) of primary hyperoxaluria type 1. METHOD BBP-711 was developed by iterative synthesis and study of the structure–activity relationship of more than 50 GO inhibitors. Lead molecules including BBP-711 were assessed for functional activity by determining inhibition of the conversion of glycolate to oxalate with purified human, mouse and rat HAOX1 enzymes. The ability of BBP-711 to bind directly to immobilized purified hGO (HAOX1 gene product) was evaluated by surface plasmon resonance. Selectivity of BBP-711 was assessed by determining its inhibition of several physiologically related gene products including that from HAOX2. In vitro efficacy of BBP-711 was tested via inhibition of oxalate production in primary hepatocytes cultured from hyperoxaluric Agxt−/− mice. In vivo efficacy of BBP-711 on urinary oxalate excretion was assessed at various doses given by oral gavage in Agxt −/− mice. Pharmacokinetics of BBP-711 was investigated to assess plasma and liver concentrations associated with efficacy. RESULTS BBP-711 is a potent inhibitor of human, rat and mouse GO (IC50 = 15.4 nM, 22.4 nM and 149 nM, respectively). BBP-711 demonstrated stronger direct binding to hGO1 (KD = 6.31 nM) than to rGO2 (KD = 12.8 nM), indicating its preference for GO1 as a target. BBP-711 specificity was demonstrated with <10% activity against off-target enzymes D-amino acid oxidase, dihydroorotate dehydrogenase and lactate dehydrogenase-A at 10 µM. BBP-711 demonstrated concentration-dependent inhibition of oxalate production by Agxt−/− hepatocytes (IC50 = 24.2 nM at 24 hours, IC50 = 42.9 nM at 48 hours). When orally dosed at 7 mg/kg for 5 days in Agxt−/− mice, BBP-711 produced a maximum reduction of urinary oxalate (60%) as well as maximum inhibition of GO activity (>88%). Higher doses did not result in greater reduction in urinary oxalate. Liver exposures (AUC0-24hr) were higher than plasma exposures at all doses tested. GO engagement by BBP-711 was also assessed in an ex vivo assay. Liver extracts from Agxt−/− and wild-type mice dosed with BBP-711 show a dose-dependent reduction in ex vivo GO activity at 1 and 4-hour post-dose. CONCLUSION Iterative and rational optimization of small molecule GO inhibitors resulted in BBP-711, a potent and specific inhibitor of GO with drug-like properties.