Design and optimization of aniline-substituted tetrahydroquinoline C5a receptor antagonists

Gold(I)-catalyzed synthesis of N-alkenyl 2-pyridonyl sec-amines

N-Alkenyl 2-pyridonyl amines are afforded in high yields via a gold-catalyzed rearrangement of 2-propargyloxypyridine and 2-(but-3-yn-1-yloxy)pyridine under acidic conditions. This approach exhibits significant utility due to its outstanding efficiency of conversion in the synthesis of secondary amines as a one-pot reaction. The initial step of the method involves a cyclization reaction for the production of pyridinium salts, followed by the next stage, where rearrangement is accomplished through the nucleophilic addition phenomenon. This approach provides the conversion of primary amines into secondary amines, resulting in a single product. Furthermore, the methodology presents a high degree of tolerance towards several pyridine and aniline derivatives, resulting in the formation of products with excellent yields.

Receptor residence time trumps drug-likeness and oral bioavailability in determining efficacy of complement C5a antagonists

Drug discovery and translation are normally based on optimizing efficacy by increasing receptor affinity, functional potency, drug-likeness (rule-of-five compliance) and oral bioavailability. Here we demonstrate that residence time of a compound on its receptor has an overriding influence on efficacy, exemplified for antagonists of inflammatory protein complement C5a that activates immune cells and promotes disease. Three equipotent antagonists (3D53, W54011, JJ47) of inflammatory responses to C5a (3 nM) were compared for drug-likeness, receptor affinity and antagonist potency in human macrophages, and anti-inflammatory efficacy in rats. Only the least drug-like antagonist (3D53) maintained potency in cells against higher C5a concentrations and had a much longer duration of action (t1/2 ~ 20 h) than W54011 or JJ47 (t1/2 ~ 1 -3 h) in inhibiting macrophage responses. The unusually long residence time of 3D53 on its receptor was mechanistically probed by molecular dynamics simulations, which revealed long-lasting interactions that trap the antagonist within the receptor. Despite negligible oral bioavailability, 3D53 was much more orally efficacious than W54011 or JJ47 in preventing repeated agonist insults to induce rat paw oedema over 24 h. Thus, residence time on a receptor can trump drug-likeness in determining efficacy, even oral efficacy, of pharmacological agents.

International Union of Basic and Clinical Pharmacology. [corrected]. LXXXVII. Complement peptide C5a, C4a, and C3a receptors

The activation of the complement cascade, a cornerstone of the innate immune response, produces a number of small (74-77 amino acid) fragments, originally termed anaphylatoxins, that are potent chemoattractants and secretagogues that act on a wide variety of cell types. These fragments, C5a, C4a, and C3a, participate at all levels of the immune response and are also involved in other processes such as neural development and organ regeneration. Their primary function, however, is in inflammation, so they are important targets for the development of antiinflammatory therapies. Only three receptors for complement peptides have been found, but there are no satisfactory antagonists as yet, despite intensive investigation. In humans, there is a single receptor for C3a (C3a receptor), no known receptor for C4a, and two receptors for C5a (C5a₁ receptor and C5a₂ receptor). The most recently characterized receptor, the C5a₂ receptor (previously known as C5L2 or GPR77), has been regarded as a passive binding protein, but signaling activities are now ascribed to it, so we propose that it be formally identified as a receptor and be given a name to reflect this. Here, we describe the complex biology of the complement peptides, introduce a new suggested nomenclature, and review our current knowledge of receptor pharmacology.

Inhibiting the C5-C5a receptor axis

Activation of the complement system is a major pathogenic event that drives various inflammatory responses in numerous diseases. All pathways of complement activation lead to cleavage of the C5 molecule generating the anaphylatoxin C5a and, C5b that subsequently forms the terminal complement complex (C5b-9). C5a exerts a predominant pro-inflammatory activity through interactions with the classical G-protein coupled receptor C5aR (CD88) as well as with the non-G protein coupled receptor C5L2 (GPR77), expressed on various immune and non-immune cells. C5b-9 causes cytolysis through the formation of the membrane attack complex (MAC), and sub-lytic MAC and soluble C5b-9 also possess a multitude of non-cytolytic immune functions. These two complement effectors, C5a and C5b-9, generated from C5 cleavage, are key components of the complement system responsible for propagating and/or initiating pathology in different diseases, including paroxysmal nocturnal hemoglobinuria, rheumatoid arthritis, ischemia-reperfusion injuries and neurodegenerative diseases. Thus, the C5-C5a receptor axis represents an attractive target for drug development. This review provides a comprehensive analysis of different methods of inhibiting the generation of C5a and C5b-9 as well as the signalling cascade of C5a via its receptors. These include the inhibition of C5 cleavage through targeting of C5 convertases or via the C5 molecule itself, as well as blocking the activity of C5a by neutralizing antibodies and pharmacological inhibitors, or by targeting C5a receptors per se. Examples of drugs and naturally occurring compounds used are discussed in relation to disease models and clinical trials. To date, only one such compound has thus far made it to clinical medicine: the anti-C5 antibody eculizumab, for treating paroxysmal nocturnal hemoglobinuria. However, a number of drug candidates are rapidly emerging that are currently in early-phase clinical trials. The C5-C5a axis as a target for drug development is highly promising for the treatment of currently intractable major human diseases.

Identification of a new class of small molecule C5a receptor antagonists

C5a is a terminal product of the complement cascade that activates and attracts inflammatory cells including granulocytes, mast cells and macrophages via a specific GPCR, the C5a receptor (C5aR). Inhibition of C5a/C5aR interaction has been shown to be efficacious in several animal models of autoimmune diseases, including RA, SLE and asthma. This account reports the discovery of a new class of C5aR antagonists through high-throughput screening. The lead compounds in this series are selective and block C5a binding, C5a-promoted calcium flux in human neutrophils with nanomolar potency.

1-(4-Bromophenyl)-2-{5-[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-4-phenyl-4H-1,2,4-triazol-3-ylsulfanyl}ethanone

The title compound, C₂₂H₂₀BrN₅OS, is a potent new fungicide. The planes of the phenyl and pyrozole rings are almost perpendicular, making a dihedral angle of 86.5 (4)°. There are two non-classical inter­molecular C—H⋯O and C—H⋯N hydrogen bonds in the crystal structure.

Methyl 4-(4-methylbenzamido)-2-sulfamoylbenzoate

The title compound, C₁₆H₁₆N₂O₅S, is a potent new fungicide. There are two mol­ecules in the asymmetric unit which are linked by C—H⋯π inter­actions, forming a dimer. The two phenyl rings in each mol­ecules are almost coplanar, with C—N—C—C torsion angles of 177.6 (2) and −172.5 (2)°. There are inter­molecular and intra­molecular N—H⋯O hydrogen bonds in the crystal structure.