If I were to start a small molecule development program with a great target in coronavirus that was well understood in a research lab, it would take approximately 4 years to discover a chemical that works and get that molecule to the point where it was ready for human testing. Then it would be several more years to get to a large clinical trial. Then manufacturing and regulatory approval might take another year. I think we are talking about 10 years or so, based on averages across many programs I have seen, and the cost to get it done is maybe 1,2 to 1,5 billion dollars. The industry standard success rate from the process from idea to marketed drug is 2-3%, with most failing along the way because science is hard.

Tl/dr; Trump doesn't know what he is talking about.