Complement is a proteolytic cascade that upon activation plays a key effector role in the innate immune system and acts to prime the adaptive immune response. During normal homeostatic events, complement is tightly regulated for its roles in immune complex clearance, lysis of target cells, opsonization, and recruitment of leukocytes and monocytes to target areas. Several endogenous regulators are responsible for the control of complement activation, however when dysregulation occurs, aberrant complement activation has been linked to autoimmune, proinflammatory, and neurodegenerative diseases, including Alzheimer0́9s disease. Inhibition of the classical complement component C1 may ameliorate hallmarks of autoimmune and inflammatory disease. The serine proteases within the C1 complex, C1r and C1s, are promising therapeutic targets for structure-based small-molecule drug development. We investigated the activity of a series of small-molecule compounds identified in a large-scale fragment library screen and those from a cheminformatics computational docking screen in which hit compounds were predicted to bind the C1r or C1s proteases. Using surface plasmon resonance and ELISA-based assays for hit validation, we analyzed the binding affinities and the inhibitory IC50's of several compounds predicted to bind and inhibit the activation of C1r or C1s in a dose-dependent manner. In this study, we have identified four lead compounds (cmp-1611, cmp-1663, cmp-1696, cmp-1827) and their 10 active structural analogues that target and inhibit C1r activation. Given their abilities to bind and inhibit C1r and favorable physicochemical properties, our lead compounds may provide a starting point for optimizing affinity and specificity necessary for developing novel routes of therapeutic upstream complement inhibition.

The complement system is an essential element of host development and immune homeostasis. This immunoregulatory enzyme cascade is driven by serine protease activation and plays critical roles in the recognition of danger signals associated with pathogens and damaged or apoptotic self-molecules. Due to its potent effector functions and ability to drive overwhelming innate and adaptive immune responses against a particular target, tight regulation is vital to prevent damage to host tissues. In the event of complement dysregulation, humans are known to become susceptible to an ever-growing number of autoimmune, inflammatory, and neurodegenerative disorders. A detailed understanding of the molecular mechanisms that drive protein function, and specifically complement activation, is fundamental to the design and development of specific complement-directed therapeutics. The complement system is comprised of three distinct pathways that differ in the molecular targets that drive pathway activation. The initiating proteases of the classical and lectin pathways are set apart from other serine proteases in that they undergo autocatalytic activation in the presence of a molecular trigger without necessitating extrinsic factors for full enzymatic activation. Using structural data derived from the enzyme-product complex of self-associated lectin pathway MASP-2 proteases, we elucidate the conformational changes that occur during autoactivation in the initiating proteases of the classical and lectin pathway. Our structural model provides an empirically derived alternative mechanism for autocatalysis that has not been previously described in the complement proteases. Using structural information derived from X-ray crystallography and autocatalysis as well as known interactions between bacterial inhibitors utilized for host complement evasion, we pursued multiple avenues for rational small-molecule drug design aimed at C1r and C1s, which are initiating proteases of the classical pathway. Molecular dynamics studies and chemical modification of compounds were used to guide the optimization and development of competitive small-molecule inhibitors against the active site of C1r. Structure-activity relationship data was generated through the bioisosteric replacement of chemical moieties of another lead compound to drive noncompetitive C1r inhibition. Moreover, advancements in technology building off protein-ligand interaction fingerprints derived from known structures were utilized in collaborative machine learning and artificial intelligence methods for the rational design of novel C1s inhibitors. Additional optimization of small-molecule compounds may ultimately lead to novel therapeutic options for diseases mediated by aberrant classical pathway activation. To aid in future endeavors in small-molecule drug screening and design, we developed a novel platform and methodology for evaluating targets outside of the complement system that requires the presence of lipid bilayers for activity. Using surface plasmon resonance, we established a bilayer model to mimic biological membranes to aid in protein characterization and screen for inhibitors capable of high affinity binding to the target surface as well as those that block protein association to the membrane, thereby inhibiting protein function. As such, biofunctional assays, such as surface plasmon resonance, can serve as powerful tools for aiding structure-based drug design strategies. Together, the structural insights gleaned from the enzyme-product complex of MASP-2, as well as surface plasmon resonance binding assays, allowed us to identify three small-molecule compound hits against both C1r and C1s using different methodologies and means of inhibition, validating differing strategies of inhibitor design. The identification of these hits, in addition to the development of a novel SPR screening platform, has led to the generation of in-depth structural data and method systems to guide future continued optimization efforts that may one day lead to the design of a small-molecule therapeutic option for diseases marked by autoimmune and inflammatory pathologies.

Complement is a proteolytic cascade that upon activation plays a key effector role in the innate immune system and acts to prime the adaptive immune response. During normal homeostatic events, complement is tightly regulated for its roles in immune complex clearance, lysis of target cells, opsonization, and recruitment of leukocytes and monocytes to target areas. Several endogenous regulators are responsible for the control of complement activation, however when dysregulation occurs, aberrant complement activation has been linked to autoimmune, proinflammatory, and neurodegenerative diseases, including Alzheimer's disease. Inhibition of the classical complement component C1 may ameliorate hallmarks of autoimmune and inflammatory disease. The serine proteases within the C1 complex, C1r and C1s, are promising therapeutic targets for structure-based small-molecule drug development. We investigated the activity of a series of small-molecule compounds identified in a large-scale fragment library screen and those from a cheminformatics computational docking screen in which hit compounds were predicted to bind the C1r or C1s proteases. Using surface plasmon resonance and ELISA-based assays for hit validation, we analyzed the binding affinities and the inhibitory IC50's of several compounds predicted to bind and inhibit the activation of C1r or C1s in a dose-dependent manner. In this study, we have identified four lead compounds (cmp-1611, cmp-1663, cmp-1696, cmp-1827) and their 10 active structural analogues that target and inhibit C1r activation. Given their abilities to bind and inhibit C1r and favorable physicochemical properties, our lead compounds may provide a starting point for optimizing affinity and specificity necessary for developing novel routes of therapeutic upstream complement inhibition.

The complement system is a protein system that combines with antibodies to form a defense against bugs and viruses. This book contains entries on all its components, including C1q and lectins, serine proteases, and terminal pathway proteins.

This book highlights progress and trends in the rapidly evolving field of complement-related drug discovery and spotlights examples of clinical applications. As an integral part of innate immunity and critical mediator in homeostatic and inflammatory processes, the human complement system has been identified as contributor to a large number of disorders including ocular, cardiovascular, metabolic, autoimmune, and inflammatory diseases as well as in ischemia/reperfusion injury, cancer and sepsis. In addition, complement is often involved in adverse immune reactions to biomaterials, cell and organ transplants or drug delivery systems. Although the complement cascade with its close to 50 extracellular protein targets has long been recognized as an attractive system for therapeutic modulation, the past few years have seen a particularly strong boost in interest. Fueled by novel research insight and the marketing of the first complement-targeted drugs, a plethora of highly creative treatment approaches and potent drug candidates have recently emerged and are currently evaluated in disease models and clinical trials. The chapters in this book cover a wide range of topics related to the development of complement therapeutics, ranging from the molecular and functional description of complement targets to the presentation of novel inhibitors, improved treatment strategies as well as examples of disease models and clinical applications. The broad and up-to-date overview on a highly versatile and dynamic field renders this book an indispensable source of information for researchers and clinicians dealing with therapeutic and disease-related aspects of the human complement system.

Encyclopedia of Immunobiology, Five Volume Set provides the largest integrated source of immunological knowledge currently available. It consists of broad ranging, validated summaries on all of the major topics in the field as written by a team of leading experts. The large number of topics covered is relevant to a wide range of scientists working on experimental and clinical immunology, microbiology, biochemistry, genetics, veterinary science, physiology, and hematology. The book is built in thematic sections that allow readers to rapidly navigate around related content. Specific sections focus on basic, applied, and clinical immunology. The structure of each section helps readers from a range of backgrounds gain important understanding of the subject. Contains tables, pictures, and multimedia features that enhance the learning process In-depth coverage allows readers from a range of backgrounds to benefit from the material Provides handy cross-referencing between articles to improve readability, including easy access from portable devices

Written in the same engaging conversational style as the acclaimed first edition, Primer to The Immune Response, 2nd Edition is a fully updated and invaluable resource for college and university students in life sciences, medicine and other health professions who need a concise but comprehensive introduction to immunology. The authors bring clarity and readability to their audience, offering a complete survey of the most fundamental concepts in basic and clinical immunology while conveying the subject’s fascinating appeal. The content of this new edition has been completely updated to include current information on all aspects of basic and clinical immunology. The superbly drawn figures are now in full color, complemented by full color plates throughout the book. The text is further enhanced by the inclusion of numerous tables, special topic boxes and brief notes that provide interesting insights. At the end of each chapter, a self-test quiz allows students to monitor their mastery of major concepts, while a set of conceptual questions prompts them to extrapolate further and extend their critical thinking. Moreover, as part of the Academic Cell line of textbooks, Primer to The Immune Response, 2nd Edition contains research passages that shine a spotlight on current experimental work reported in Cell Press articles. These articles also form the basis of case studies that are found in the associated online study guide and are designed to reinforce clinical connections. Complete yet concise coverage of the basic and clinical principles of immunology Engaging conversational writing style that is to the point and very readable Over 200 clear, elegant color illustrations Comprehensive glossary and list of abbreviations