WCN26-3140 PROSPECTIVE STUDY ON DARATUMUMAB WITH OR WITHOUT AUTOLOGOUS STEM CELL TRANSPLANTATION FOR THE TREATMENT OF MONOCLONAL GAMMOPATHY OF RENAL SIGNIFICANCE (MGRS) DISEASES

response to tolvaptan, which was defined as an improvement in estimated glomerular filtration rate (GFR) slope, was investigated.Results: A total of 24 patients (median age 48 years; 14 men; median estimated GFR 54.5 mL/min/1.73m2; median height-adjusted total kidney volume 835 mL/m) were included.Comparing before and after tolvaptan therapy, the estimated GFR slope changed from -3.4 (-5.7, -2.1) to -2.9 (-4.4,-1.9) mL/min/1.73m2 per year (p = 0.069), and the annual increase rate of total kidney volume changed from 7.6 (5.9, 12.2) to 2.1 (-1.1, 7.3) % (p <0.01).During a median follow-up period of 3.3 years after the initiation of tolvaptan, the estimated GFR slope improved, as compared to before tolvaptan therapy, in 16 responders.Baseline urine cAMP level was 2.6 (2.2, 3.1) nmol/mg of creatinine, plasma AVP level was 1.6 (1.0, 1.8) pg/mL, and urine cAMP/plasma AVP ratio ranged from 0.95 and 5.55 with a median of 1.81.The baseline urine cAMP/plasma AVP ratio was a significant predictor of tolvaptan responder, with an adjusted odds ratio of 59.7 (95% confidence interval 1.2-2940, p = 0.040).The optimal cutoff value for predicting tolvaptan response was identified as 1.66 (sensitivity 0.81, specificity 0.88), yielding an area under the receiver operating characteristic curve of 0.91 (95% confidence interval 0.78-1.0).Although improvement in the growth of total kidney volume after tolvaptan therapy was observed in 19 patients, the urine cAMP/plasma AVP ratio was not a significant predictor of suppression of kidney volume growth, with an adjusted odds ratio of 1.7 (95% confidence interval 0.37-8.1,p = 0.49).Conclusion: Baseline urine cAMP/plasma AVP ratio is an independent predictor of response to tolvaptan, as defined by improvement in estimated GFR slope, in patients with ADPKD.I have no potential conflict of interest to disclose.I did not use generative AI and AI-assisted technologies in the writing process.