In the years since identification of autosomal-dominant polycystic kidney disease (ADPKD) genes, the lag time between initial understanding and translation to therapy has decreased rapidly. Albaqumi and colleagues describe a promising approach to slow ADPKD cyst enlargement through inhibition of the basolateral KCa3.1 K(+) channel, using a nontoxic small molecule with a close congener poised for rapid entry into the clinic. Cyst fluid accumulation can be blocked from both sides now.