Once again - a chemist like Polkadot would be best

Once again - a chemist like Polkadot would be best person to ask this question to. I know there are a lot of computational design programs for screening new drugs. Big pharma buys them to run possibilities for new molecules and potential reworked old molecules - the programs help chemist see the structure and estimate feasibility without wasting hours of labwork. But that's about all I know. Computer aided drug design and screening. Someone with good chem background could explain more!