PGVL Hub is an integrated molecular design desktop tool that has been developed and globally deployed throughout Pfizer discovery research units to streamline the design and synthesis of combinatorial libraries and singleton compounds. This tool supports various workflows for design of singletons, combinatorial libraries, and Markush exemplification. It also leverages the proprietary PGVL virtual space (which contains 10(14) molecules spanned by experimentally derived synthesis protocols and suitable reactants) for lead idea generation, lead hopping, and library design. There had been an intense focus on ease of use, good performance and robustness, and synergy with existing desktop tools such as ISIS/Draw and SpotFire. In this chapter we describe the three-tier enterprise software architecture, key data structures that enable a wide variety of design scenarios and workflows, major technical challenges encountered and solved, and lessons learned during its development and deployment throughout its production cycles. In addition, PGVL Hub represents an extendable and enabling platform to support future innovations in library and singleton compound design while being a proven channel to deliver those innovations to medicinal chemists on a global scale.