Based on drug interaction studies conducted with sofosbuvir, no clinically significant drug interactions have been observed with tacrolimus. Coadministration of tacrolimus (5 mg single dose) and sofosbuvir 400 mg single dose) to 16 subjects decreased sofosbuvir Cmax by 3% but increased AUC by 13%; Cmax of GS-331007 decreased by 3% and there was no change in AUC. Tacrolimus Cmax decreased by 27% and AUC increased by 9%.

A single-centre retrospective study of 108 patients with solid organ transplants examined immunosuppression doses before and during DAA treatment in patients, 91% of whom were taking tacrolimus. Secondary outcome measures were new or worsening rejection, graft dysfunction, and SVR12. The most common DAA regimen given was simepravir + sofosbuvir (33.9%), followed by ledipasvir/sofosbuvir (26.6%). There were no statistically significant changes in immunosuppressant doses or exposure after 4 weeks of DAA therapy. Only 1 patient experienced new or worsening rejection. Five patients experienced new or worsening graft dysfunction. Ninety-eight per-cent of patients achieved SVR12. The rejection rate was similar to historic controls in the literature and the cure rate is likewise similar to the general population. The authors conclude there was no drug interaction between the immunosuppressants and the DAAs.