“There have been only 11 mutations to proteins that are widely distributed. These are potentially functionally distinct variants that deserve attention and experimental and clinical follow up. But my expectation would be most have ‘little effect’ without further data“.
“in terms of immunity, there is a single widely circulating mutation in spike protein (D614G). Spike is present on the surface of the virus and is what the immune system sees“
“If you follow a transmission chain in which one person with flu infects another person and they infect another person and so on, you'll find that the virus mutates about once every 10 days across its genome. Almost all of these mutations will have little to no effect on virus function. Evolution weeds out the mutations that ‘break’ the virus and mutations that make a virus replicate better are extremely rare.”
The effects of the OP drug increasing the mutation rate would need to be modelled to understand risks.
Also, for people who don't know, Trevor is arguably the single most expert person in the world to weigh in on this.
And here's the specific thread where he predicts it will take a few years for the virus to mutate enough to significantly hinder a vaccine: https://twitter.com/trvrb/status/1242628550563250176