CEP-1347 is a potent inhibitor of mixed lineage kinase (MLK), which was investigated for ameliorating HIV-associated neurocognitive disorders. CEP-1347 and atazanavir pharmacokinetics were determined when CEP-1347 50 mg twice daily was administered to HIV-infected patients (n=20) receiving combination antiretroviral therapy including atazanavir and ritonavir (ATV/RTV, 300/100 mg) once daily continuously. Co-administration of CEP-1347 and ATV/RTV resulted with significant changes in pharmacokinetics of ATV but not RTV. Specifically, an increase in ATV accumulation ratio of 15 % (p=0.007) and a prolongation of T1/2 from 12.7 to 15.9 h (p=0.002) were observed. The results suggested that co-administration of CEP-1347 with ATV/RTV in HIV-infected patients might result in limited impact on ATV but not on RTV pharmacokinetics.