STABIL-study: The Course of Therapy, Safety and Pharmacokinetic Parameters of Conversion of Prograf® to Tacrolimus HEXAL®/Crilomus® in Renal Transplant Recipients - an Observational Study in Germany.

Background/objective: Tacrolimus HEXAL®/Crilomus® is an approved generic immunosuppressant for the prevention and treatment of rejection following renal transplantation. For safe and socioeconomically efficient conversion of the innovator into a generic formulation, high- -quality data are necessary, in view of the different and country-specific comorbidities and pharmacokinetics in kidney transplant recipients.

Patients and methods: From 2014 to 2017, we enrolled 32 kidney transplant recipients, receiving newly prescribed Tacrolimus HEXAL®/Crilomus® in 5 German centers. Efficacy and safety data were collected over 6-8 months and retrospectively compared to the period prior to conversion.

Results: The mean tacrolimus trough level was 4.91 ng/mL Standard Deviation (SD) (SD ±1.7) before and 5.06 ng/mL (SD ±1.97) after conversion. Mean tacrolimus trough concentration-dose-ratio (+/- SD) was 187.1 ng/mL/mg/kg/day (SD 99.2) for the reference and 205.1 ng/mL/mg/kg/day (SD 133) for the generic product, resulting in a non-significant difference of 18.0 ng/mL/mg/kg/day (SD 71.8) (p=0.84, Wilcoxon V=180). Overall, dosing had to be changed in 4 (14.8%) patients. Graft function remained stable and no rejections occurred.

Conclusion: In conclusion, conversion to the generic tacrolimus formulation can be considered safe and feasible in long-term kidney transplant recipients in Germany. As suggested by guidelines, vigilant therapeutic drug monitoring is recommended to account for possible tacrolimus concentration variability on the individual patient level.