CYP3A4 and graft versus host disease: Both ruxolitinib and tacrolimus are metabolized via CYP3A4, and posaconazole is a strong CYP3A4 inhibitor; however, the ruxolitinib PK study indicated the safety and efficacy of the therapeutic regimen, ultimately leading to successful remission of GVHD while mitigating serious fungal infection and sepsis [14, 15, 16].