Gansevoort, Ron T.

The vasopressin–cAMP–osmolality axis is abnormal in autosomal dominant polycystic kidney disease (ADPKD). In the Tolvaptan Efficacy and Safety in Management of Autosomal Dominant Polycystic Kidney Disease and Its Outcomes 3:4 Trial, a 3-year randomized, placebo-controlled trial in adults, the vasopressin V2 receptor antagonist tolvaptan slowed ADPKD progression in patients with preserved GFR. Here, we investigated the determinants of baseline urine osmolality (Uosm) and its value as a severity marker of ADPKD, the factors influencing the response to tolvaptan, and whether change in Uosm associated with key trial end points. At baseline, lower Uosm independently associated with female sex, presence of hypertension, lower eGFR, higher total kidney volume (TKV), and higher age. Tolvaptan consistently reduced Uosm by 200–300 mOsm/kg over 36 months. The Uosm response to tolvaptan depended on baseline eGFR and Uosm. Subjects with greater change in Uosm experienced a significant reduction in clinical progression events. Among subjects receiving tolvaptan, those with a greater suppression of Uosm had slower renal function decline. Assessment at follow-up, off medication, revealed a significant decrease in Uosm in both placebo and treated groups. Tolvaptan significantly increased plasma osmolality, which returned to baseline at follow-up. In conclusion, baseline Uosm in ADPKD reflects age, renal function, and TKV, and baseline Uosm, eGFR, and TKV influence the effect of tolvaptan on Uosm. The greatest renal benefit occurred in subjects achieving greater suppression of Uosm, that is, those with better eGFR at baseline. These results support the link between vasopressin V2 receptor signaling and ADPKD progression.

Abstract Background: Autosomal-dominant polycystic kidney disease (ADPKD) is characterized by multitudes of expanding renal cysts associated with mononuclear interstitial infiltrates. Monocyte chemotactic protein-1 is produced in the kidneys and excreted in the urine (uMCP1) of these patients in increased amounts. In the TEMPO 3:4 trial, tolvaptan slowed the rate of increase in total kidney volume (TKV) and the rate of decline in estimated glomerular filtration rate (eGFR). In a sub-analysis, we determined whether tolvaptan administration for up to 3 years changed the urinary excretion of MCP-1 referenced to creatinine in 869 treated subjects compared with 438 placebo subjects. Methods: Treatment group differences of uMCP1 at 0.75, 12, 24 and 36 months were evaluated by ANCOVA with factor of treatment and covariate baseline. Results: At baseline, mean uMCP1 was 429 ± 224 pg/mg in the tolvaptan and 434 ± 233 pg/mg in the placebo groups, ∼4-fold greater than normal. Log uMCP1 associated positively with log TKV (r = 0.2645, P < 0.0001) and negatively with eGFR (r = −0.1555 P < 0.0001) and fasting urine osmolality (r = −0.1933, P < 0.0001). Tolvaptan reduced uMCP1 13.8 ± 4.4% (P < 0.0001) below placebo-treated subjects at 24 months and 14.4 ± 3.7% (P < 0.0001) at 36 months, and to the same extent in females and males. The effect of tolvaptan on uMCP1 excretion at 36 months extended across CKD Stage 1 (11.1 ± 6.4%, P = 0.0595), CKD 2 (13.9 ± 5.4%, P = 0.0050) and CKD 3 (21.4 ± 8.0%, P = 0.0020). Conclusion: Tolvaptan, administered for 3 years to patients with ADPKD, caused a sustained reduction in the urinary excretion of MCP-1 relative to placebo.