It is logically impossible to check the effect of a compound on a virus without using said virus. However, if you know the target (enzyme) that the drug is directed against, you could measure inhibition of that enzyme, using a transgenic enzyme. Such data could at least justify the expensive use of a BS3 or BS4 laboratory for the real test.

In your case you need to know what is a target for the drug: viral RNA or viral proteins Das the drug binds to these viral components selectively? Can you check it first?

..in silico, of course.

Thanks both for your prompt response.