Benzbromarone Analog SAR: Potent hURAT1 (SLC22A12) Inhibitors and Drug Transporter Interaction Studies

There were two main purposes for this study. One, to report two benzbromarone analogs and test their in vitro activity in the URAT1 inhibition assay; and two, to probe the structure-activity relationship (SAR) of various benzbromarone analogs regarding other drug transporters that may play a role in the uric acid uptake/elimination interplay.

In brief, chemical synthesis of two benzbromarone analogs was prepared using methods analogous to those reported. Furthermore, drug transporter protein inhibition was investigated in vitro using oocytes expressing hURAT1, hURATv1 (GLUT9), hOAT1, hOAT3, hOAT10, hNPT4, OATP1B1, OATP1B3 and OATP2B1 prepared and utilized to conduct inhibition studies. In addition, one novel benzbromarone analog was studied via in vivo rat pharmacokinetic experiments to determine apparent oral bioavailability.

Two analogs, 6-fluoro-benzbromarone (5) and 5,6-difluoro-benzbromarone (9), were synthetically prepared and 5 had a hURAT1 IC₅₀ inhibition of 18 ± 4 nM, while analog (9) had an IC₅₀ of 245 ± 64 nM. Analog (5) had good oral bioavailability (F_a) >0.6 in rat. Eadie-Hofstee plot and double-reciprocal plot of the Michaelis-Menten equation are summarized for benzbromarone (2) and its major Phase I metabolite 6-hydroxy-benzbromarone (3).

These results illustrate that the K_m for [¹⁴C]UA uptake was not altered in the presence of 2 or 3, but rather the V_max was reduced in the presence of inhibitors when added to the uptake solutions. As a result, these data support the notion that 2 and 3 inhibit [¹⁴C]UA uptake by non-competitive inhibition and not at the URAT1 binding site.