Our PADS™ (Peptide Antagonist Discovery System) platform is a library-based screening system that employs a protein fragment complementation-based approach. Key to this approach is that the system is performed in an intracellular environment. This means that the protein target as well as the peptide library members are expressed in live cells, ensuring that our peptide hits are more likely to be resistant to degradation by proteases, soluble, nontoxic, and target-specific in the presence of other cytoplasmic proteins. These are all attributes worth identifying as early as possible in the discovery process to save time and expense of working on hits of no value, and are not possible to assess using extracellular in vitro approaches.