#2587 Is the generic treatment as effective as the original drug? A comparative study of the treatment with tolvaptan in autosomal dominant polycystic kidney disease at the Virgen Macarena University Hospital

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease in the population. So far, Tolvaptan is the only drug approved for its treatment. Recently, the generic version of the drug has been marketed, although a post-marketing study of the original drug has not yet been published. The objective of our study is to compare the available outcomes in patients treated with the original drug versus the generic one in our healthcare area. Method A total of 44 patients treated with Tolvaptan for at least one year were selected: − 27 treated with the original drug (Group 1) − 17 treated with the generic drug (Group 2). The dose adjustment was similar in all cases: during the first month, the dose was 45/15, in the second month 60/30, and from the third month onwards, 90/30. This last dose was maintained for at least six months. After six months, the treatment regimen/drug used was modified according to the patients' outcomes. Those who did not achieve urinary osmolarity (Uosm) targets were switched to the original drug Sociodemographic variables (sex, age), total renal volume adjusted to body surface area (TRV), and analytical parameters (eGFR, sodium, Uosm, and uric acid levels (UA)) were collected at the start of treatment, after one month, at six months, and one year after treatment initiation. The groups were compared using Student's t-test or the Mann-Whitney U test, depending on whether the variable showed a normal distribution or not. Results Global data: Mean age: 43.8 ± 8 years. 29 (67%) women. TRV (Total Renal Volume): 1117.65 ± 686.79 cc. Mayo classification: Stage B: 2 (5%), Stage C: 11 (28%), Stage D: 17 (44%), Stage E: 9 (23%). At baseline: eGFR (estimated Glomerular Filtration Rate): 62.7 ± 29.66 ml/min, serum sodium 140.85 ± 2.23 mEq/L, Uosm (urinary osmolarity) 565.8 ± 161.7 mOsm/kg, uric acid (UA) 5.86 ± 1.48 mg/dl. The comparison between the two groups is provided in the attached table. Conclusion The decline in GFR at one year was greater in the group treated with the generic drug, although no significant differences were found. The urinary osmolarity (Uosm) in the group treated with the generic drug remained >300 mOsm/kg until the sixth month, above the recommended values. After the sixth month, the strategy of switching patients who did not achieve the desired Uosm to the original drug was implemented, resulting in appropriate figures by the end of the year. In conclusion, given the limitations of our study due to the sample size, the results show that the generic group did not achieve the desired beneficial effects, with the same side effects observed.