TACR1 and central nervous system cancer: The antitumor effect of temozolomide, the antiviral drug ritonavir, and the brain-penetrant NK-1R antagonist aprepitant (an anti-emetic drug) is higher against GAMG glioma cells when co-administered than when separately administered or when the administration of temozolomide + aprepitant, ritonavir, or ritonavir + aprepitant is performed; thus, a significant antitumor synergic effect occurs when antiviral and anti-emetic drugs are co-administered with temozolomide [63].