Pharmacokinetics and Pharmacodynamics of Tolvaptan in Autosomal Dominant Polycystic Kidney Disease: Phase 2 Trials for Dose Selection in the Pivotal Phase 3 Trial

In the pivotal TEMPO 3:4 trial, the arginine vasopressin V2‐receptor antagonist tolvaptan reduced the rate of kidney growth in patients with autosomal dominant polycystic kidney disease. Tolvaptan was initiated as daily morning/afternoon doses of 45/15 mg, and uptitrated weekly to 60/30 mg and 90/30 mg according to patient‐reported tolerability. The current report describes 3 phase 2 trials in adult autosomal dominant polycystic kidney disease subjects that were the basis for the titrated split‐dose regimen: a single ascending‐dose trial (tolvaptan 15 to 120 mg; n = 11), a multiple split‐dose trial (tolvaptan 15/15 mg, 30/0 mg, 30/15 mg, and 30/30 mg; n = 37), and an 8‐week open‐label safety and efficacy trial in 46 of the 48 subjects who participated in the prior 2 trials (tolvaptan 30/15 mg, 45/15 mg, 60/30 mg, and 90/30 mg). Urine osmolality (U(osm)) was chosen as the biomarker of V2 receptor inhibition. Two tolvaptan doses per day were necessary to suppress U(osm) to <300 mOsm/kg for 24 hours. The 45/15‐mg regimen was well tolerated and effective in suppressing U(osm) in >50% of subjects. Therefore, this regimen was selected as the starting regimen for the TEMPO 3:4 trial. The 90/30‐mg regimen suppressed U(osm) in 85% of subjects tested; however, only 28/46 subjects agreed to uptitrate to 90/30 mg due to tolerability. Higher concentrations of tolvaptan were less well tolerated, resulting in adverse events of pollakiuria, thirst, polyuria, nocturia, and a higher number of times out of bed to urinate. Subjects who agreed to uptitrate to 90/30 mg had lower eGFR than those who did not uptitrate.