1) Current status in drug discovery methodology There are four commonly used approaches for the generation of "hits" and "leads" in contemporary drug discovery: (1) Structure-Activity-Relationship (SAR) research on high throughput screening (HTS) data, (2) transformation of endogenous ligands into druglike compounds, (3) in silico drug design and (4) fragment-based design. Due to the absence of a single eminent strategy, drug discovery projects often try implementing tailored aspects of several of these approaches simultaneously. Common to all these approaches is that lead molecules are produced from iterative cycles of design, synthesis and potency evaluation, each time producing further optimized compounds. This is generally a very time- and cost-consuming process that could be significantly shortened by implementing "on-target" strategies. The latter rely on direct assistance of the drug target, which serves as a physical template that selects useful drug fragments and assembles them into finalized ligands. In this way, synthesis and potency determination, along with aspects of molecular design, are merged into a single, time-efficient experimental step. Limited but convincing proof for the "on-target" drug design concept is present in literature and has relied on "click chemistry", reductive amination, hydrazone formation and disulfide exchange.1 In order to increase the practical value of on-target approaches for drug discovery, three factors are in our opinion required: (1) expansion of the range of (bio-orthogonal) chemistry types amenable to on-target approaches and, related to the former, (2) improvement of the "druglikeness" of the compound types that can be produced. (3) In addition, models offering insight into the fundamental kinetic and thermodynamic drivers of "on-target" reactions are, apart from one example, virtually absent from the scientific literature.2
2) Current status in drug discovery for urokinase plasminogen activator (uPA) and caspase 1. uPA and caspase 1 have been selected as the model targets for this work. Longstanding expertise in inhibitor discovery and biochemical screening exists for these targets at UAMC. In addition, both are generally considered as "daunting targets" for which drug discovery has proven challenging. uPA is a trypsin-like serine protease that is overexpressed in metastasizing solid tumors. The enzyme is a valuable oncology target but clinical development of its inhibitors has been problematic. This is most probably related to the doubtful biopharmaceutical quality of developed compounds and their insufficient selectivity with respect to other, phylogenetically related trypsin-like proteases.3 Likewise, selectivity issues have also been a constant concern with caspase 1 inhibitors. Caspase 1, also known as interleukin 1 converting enzyme (ICE) is a cysteine protease and a so-called "inflammatory caspase". Given its involvement in inflammasome formation, pyroptosis and necrosis, ICE is a validated drug target for a range of disorders characterized by inflammation and tissue remodeling. 4
B) Project Objectives
1) Developing reliable on-target versions of reaction types with high value for drug discovery.
2) Developing computational approaches to model and rationalize on-target reactions and their outcome.
3) Validating the technology by producing druglike inhibitors for uPA and caspase 1.