Early phase drug discovery is a multi-parameter optimisation process. Finding drugable targets, discovering starting points for lead optimisation and creating novel structures with new biological properties within these constraints is challenging. As an example of a drug optimisation strategy, recent work on 5-HT1B antagonists will be described. This is put in the context of the drugability of the target, the desired physicochemical properties of the desired molecules and approaches to compound design to create high affinity, selective molecules that are optimised to have low Central Nervous System (CNS) penetration.