CP19, a histamine receptor antagonist, is an entry inhibitor against both Ebolavirus ( EBOV ) and Marburgvirus ( MARV ) with IC 50 s of 3.4 μM and 29.5 μM, respectively. CP19 has SI values of 29.4 and 3.4 for EBOV and MARV , respectively. CP19 has antiviral activity.