Combined prophylactic and therapeutic use maximizes hydroxychloroquine anti-SARS-CoV-2 effects in vitro

Nicola Clementi; Elena Criscuolo; Roberta Antonia Diotti; Roberto Ferrarese; Matteo Castelli; Roberto Burioni; Massimo Clementi; Nicasio Mancini

In the lack of SARS-CoV-2-specific drugs it is extremely important to evaluate the clinical potential of drug-repurposing in order to face the current pandemic 8 . HCQ has gained the attention of the scientific and medical community based on previous in vitro data on similar viruses (SARS and MERS) and on preliminary reports discussing its possible clinical effectiveness [2] [3] [4] . In this atypical context, in which on-field medicine often anticipates experimental laboratory pre-clinic, there is urgent need of prompt experiments addressing specific clinical questions. For example, it is not clear what is the best administration regimen to maximise possible HCQ anti-viral effectiveness in COVID-19 patients. At this regard, a recent study evaluated the direct anti-SARS-CoV-2 effect in vitro and, importantly, modelled its bioavailability at the lung level where it could maximally exert its antiviral activity. Based on a dosing regimen of 400 mg given twice daily for 1 day, followed by 200 mg twice daily for 4 more days, it also suggested the more useful drug concentrations to be used in clinicallyoriented phenotypic laboratory assays 5,6,9 . On that basis, we evaluated the HCQ antiviral activity when administered before (preadsorption), after (post-adsorption) or before and after (full-time) virus adsorption in order to simulate its possible prophylactic, therapeutic and prophylactic/therapeutic clinical use. Moreover, we focused our attention on a single concentration (10 uM) easily achieved, well tolerated and endowed with a strong antiviral activity 6 . Moreover, in order to speculate on its possible mechanism of action, we also evaluated HCQ activity performing virus adsorption at 37 and 4°C. In fact, at 37°C the virus enters the cell in a more physiological context while, conversely, at 4°C virus it can dock to the cell receptor, but its internalisation is much more limited.