6-Substituted amiloride derivatives as inhibitors of the urokinase-type plasminogen activator for use in metastatic disease.
Buckley BJ, Majed H, Aboelela A, Minaei E, Jiang L, Fildes K, Cheung CY, Johnson D, Bachovchin D, Cook GM, Huang M, Ranson M, Kelso MJ.
The oral K+-sparing diuretic amiloride shows anti-cancer side-activities in multiple rodent models. These effects appear to arise, at least in part, through moderate inhibition of the urokinase-type plasminogen activator (uPA, K<sub>i</sub> = 2.4 µM), a pro-metastatic trypsin-like serine protease that is upregulated in many aggressive solid malignancies. In applying the selective optimization of side-activity (SOSA) approach, a focused library of twenty two 6-substituted amiloride derivatives were prepared, with multiple examples displaying uPA inhibitory potencies in the nM range. X-ray co-crystal structures revealed that the potency increases relative to amiloride arise from increased occupancy of uPA's S1β subsite by the appended 6-substituents. Leading compounds were shown to have high selectivity over related trypsin-like serine proteases and no diuretic or anti-kaliuretic effects in rats. Compound 15 showed anti-metastatic effects in a xenografted mouse model of late-stage lung metastasis.