#2119 Long-term efficacy of tolvaptan therapy in patients with ADPKD

Abstract Background and Aims Currently, the only available therapy to ameliorate disease progression in patients with autosomal dominant polycystic kidney disease (ADPKD) is tolvaptan, a vasopressin V2 receptor antagonist. Real-life data on tolvaptan treatment effect is sparce, with several limitations including restricted follow-up, relatively small patient groups, no control groups, or only data reported on kidney function without total kidney volume. We studied, therefore, the long-term effect of tolvaptan on kidney function as well as kidney growth in a relatively large number of real-life ADPKD patients and controls. Moreover, we investigated the effect of salt and protein intake on long-term treatment efficacy. Method Data from two national ADPKD cohorts were pooled. Kidney function (creatinine-based eGFR) was measured at least yearly and total kidney volume (TKV, measured by MRI or CT) at least 3-yearly. Salt and protein intake were measured by 24 h urine excretion. To investigate the long-term effects of tolvaptan we assessed change in eGFR and TKV before as well as after start of tolvaptan using linear mixed effects models. For this purpose, we excluded the acute treatment effect from start to 6 months after initiation of tolvaptan. As a control group, we included all patients who were not treated with tolvaptan, assessing change in eGFR and TKV before and after the theoretical start of treatment (based on the average time of tolvaptan initiation observed in the tolvaptan-treated group) as well as a matched control group. Subgroup analyses of salt and protein intake were based on the median urinary excretion of sodium or urea. Results 697 patients (47 ± 12 years, 59.1% female) were included, of which 104 patients used tolvaptan. Mean duration of tolvaptan use was 6.0 ± 4.5 years (range: 0.8 to 15.6). Tolvaptan use reduced yearly eGFR decline by 17.4% (−4.43 to −3.66 mL/min/1.73 m2/year, p = 0.03, number of measurements: n = 817), whereas in the non-tolvaptan control group after the theoretical start of treatment, eGFR decline increased by 13.3% (−1.95 to −2.21 mL/min/1.73 m2/year, p = 0.2, n = 2804). Long-term TKV growth did not change after start of tolvaptan treatment (4.90 to 5.53%/year, p = 0.5, n = 316). Similar results were obtained in the matched control group. A more substantial treatment effect of tolvaptan on eGFR slope was noted in patients with high compared to low salt intake (assessed as ≥ versus median urinary sodium excretion of 146 mmol/24 h (difference 1.62 (0.22 to 3.02) mL/min/1.73 m2/year, p = 0.02). Subgroup analysis according to median protein intake did not show a significant difference in tolvaptan treatment effect. Conclusion In this study, with real-life patient data, long-term follow-up, and a control group, we found that tolvaptan attenuated long-term kidney function decline but, notably, did not influence kidney growth. Higher daily salt intake was associated with a more substantial tolvaptan treatment effect, perhaps due to higher vasopressin levels before treatment, and consequently more vasopressin antagonism by tolvaptan.