An example of what makes this so difficult is the "activity cliffs" often found in drug development: many pairs of apparently similar molecules will have totall

An example of what makes this so difficult is the "activity cliffs" often found in drug development: many pairs of apparently similar molecules will have totally different activity against a target protein. These differences can be understood if examined with costly physics-based simulations, but they have so far shown few of the simpler, compressible patterns that make machine learning effective.