Chloroquine, used in the treatment of malaria and MDR-strains, is an endosomal pH regulator, which in vitro has shown inhibition of the viral replication of SARS-COV. Addition of chloroquine to infected cultures could be delayed up to 5h post-infection without an important drop in antiviral activity (3). 

References
[1] Laufer, M. et al.: PLoS One., 7, e42284 (2012).

[2] Hangartner, S. et al.: Drug Test. ANal., 5, 777 (2013).

[3] Keyaerts, E., Vijgen, L., Maes, P., Neyts, J. and Van Ranst, M. In vitro inhibition of severe acute respiratory syndrome coronavirus by chloroquine, Biochemical and Biophysical Research Communications, 323(1), 264-268 (2004) [Online]. Available at: https://www.sciencedirect.com/science/article/pii/S0006291X0401839X.