Verinurad (RDEA3170)

Verinurad inhibited the transport activity of human URAT1 in a dose-dependent manner, at high potency with an IC50 of 25 nM. Verinurad inhibited the related URAT1 homologs OAT4 and OAT1 with approximately 200-fold lower affinity compared to URAT1 with IC50 values of 5.9 μM and 4.6 μM, respectively. Human URAT1 (IC50=0.025 μM) has a 1,640-fold higher affinity for verinurad compared to rat URAT1(IC50 = 41 μM). Verinurad has a high potency for human URAT1, and residues 35, 365 and 481 all contribute to verinurad affinity. Human URAT1 carrying a chimeric point mutation at position 365, in which human Phe-365 is replaced by rat Tyr-365 (human URAT1-F365Y or h-F365Y) has an IC50 of 4.0 μM, a significant 160-fold lower affinity relative to human URAT1. Meanwhile, rat URAT1 carrying the opposite point mutation (rat URAT1-Y365F or r-Y365F), had an IC50 of 2.9 μM, a significant 14-fold higher affinity compared to rat URAT1^[1].

URAT1 and OAT4 activity assays were performed in assay buffer con- sisting of 25 mM MES pH 5.5 (from a 1 M MES solution adjusted to pH 5.5 with sodium hydroxide), 125 mM sodium gluconate, 4.8 mM potassium gluconate, 1.2 mM monobasic potassium phosphate, 1.2 mM magnesium sulfate, 1.3 mM calcium gluconate and 5.6 mM glucose. URAT1 inhibitors were serially diluted into assay buffer and added to the cells for 5 minutes prior to addition of substrate. URAT1-expressing cells were incubated with 100 μM 14C-uric acid for 10 minutes and OAT4-expressing cells were incubated with 20 μM carboxyfluorescein for 5 minutes. Cells were then washed three times in 25 mM MES pH 5.5/125 mM sodium gluconate, and solubilized in Ultima Gold prior to liquid scintillation counting. Each treatment is measured in triplicate.

In human, absorption of a single dose is rapid, and exposure (Cmax and AUC) increases with dose up to the maximum dose tested. Cmax is at 0.5-0.75 hours post dose in the fasted state, and is slightly delayed to 1.25 hours post dose in the fed state. The t1/2 is approximately 10-15 hours across doses. Verinurad was well tolerated at the doses studied. In the systemic circulation, verinurad appeared to be a high clearance drug (CL/F ranged ~30-50 L/h) with extensive extravascular distribution. Renal excretion of verinurad is limited to only ~2%–3% in the urine, suggesting that the majority of verinurad is likely cleared in the liver via biotransformation to metabolites^[2].