Torres VE, et al. - In TEMPO 3:4 (Tolvaptan Efficacy and safety in Management of Polycystic kidney disease and its Outcomes) Clinical Trial, tolvaptan (the vasopressin V2 receptor antagonist) slowed total kidney volume (TKV) growth and estimated glomerular filtration rate (eGFR) decline relative to placebo. In TEMPO 4:4, a sustained disease-modifying effect of tolvaptan on eGFR was supported. Moreover, the observed lack of a sustained treatment difference on TKV may be accounted for by limitations of the trial design, including loss of randomization and baseline imbalances ensuing TEMPO 3:4. Safety profile similar to that observed in TEMPO 3:4 was noted.