Nils Ostermann

Novel Heterocyclic Dpp-4 Inhibitors for the Treatment of Type 2 Diabetes.

Novel deazaxanthine-based DPP-4 inhibitors have been identified that are potent (IC(50) <10nM) and highly selective versus other dipeptidyl peptidases. Their synthesis and SAR are reported, along with initial efforts to improve the PK profile through decoration of the deazaxanthine core. Optimisation of compound 3a resulted in the identification of compound (S)-4i, which displayed an improved in vitro and ADME profile. Further enhancements to the PK profile were possible by changing from the deazahypoxanthine to the deazaxanthine template, culminating in compound 12g, which displayed good ex vivo DPP-4 inhibition and a superior PK profile in rat, suggestive of once daily dosing in man.

Small-molecule factor D inhibitors targeting the alternative complement pathway

Complement is a key component of the innate immune system, recognizing pathogens and promoting their elimination. Complement component 3 (C3) is the central component of the system. Activation of C3 can be initiated by three distinct routes-the classical, the lectin and the alternative pathways-with the alternative pathway also acting as an amplification loop for the other two pathways. The protease factor D (FD) is essential for this amplification process, which, when dysregulated, predisposes individuals to diverse disorders including age-related macular degeneration and paroxysmal nocturnal hemoglobinuria (PNH). Here we describe the identification of potent and selective small-molecule inhibitors of FD. These inhibitors efficiently block alternative pathway (AP) activation and prevent both C3 deposition onto, and lysis of, PNH erythrocytes. Their oral administration inhibited lipopolysaccharide-induced AP activation in FD-humanized mice. These data demonstrate the feasibility of inhibiting the AP with small-molecule antagonists and support the development of FD inhibitors for the treatment of complement-mediated diseases.

A Novel Class of Oral Direct Renin Inhibitors: Highly Potent 3,5-Disubstituted Piperidines Bearing a Tricyclic P3–P1 Pharmacophore

A small library of fragments comprising putative recognition motifs for the catalytic dyad of aspartic proteases was generated by in silico similarity searches within the corporate compound deck based on rh-renin active site docking and scoring filters. Subsequent screening by NMR identified the low-affinity hits 3 and 4 as competitive active site binders, which could be shown by X-ray crystallography to bind to the hydrophobic S3-S1 pocket of rh-renin. As part of a parallel multiple hit-finding approach, the 3,5-disubstituted piperidine (rac)-5 was discovered by HTS using a enzymatic assay. X-ray crystallography demonstrated the eutomer (3S,5R)-5 to be a peptidomimetic inhibitor binding to a nonsubstrate topography of the rh-renin prime site. The design of the potent and selective (3S,5R)-12 bearing a P3(sp)-tethered tricyclic P3-P1 pharmacophore derived from 3 is described. (3S,5R)-12 showed oral bioavailability in rats and demonstrated blood pressure lowering activity in the double-transgenic rat model.

Structure-based design of substituted piperidines as a new class of highly efficacious oral direct Renin inhibitors.

A cis-configured 3,5-disubstituted piperidine direct renin inhibitor, (syn,rac)-1, was discovered as a high-throughput screening hit from a target-family tailored library. Optimization of both the prime and the nonprime site residues flanking the central piperidine transition-state surrogate resulted in analogues with improved potency and pharmacokinetic (PK) properties, culminating in the identification of the 4-hydroxy-3,5-substituted piperidine 31. This compound showed high in vitro potency toward human renin with excellent off-target selectivity, 60% oral bioavailability in rat, and dose-dependent blood pressure lowering effects in the double-transgenic rat model.

Gift from Nature: Cyclomarin A Kills Mycobacteria and Malaria Parasites by Distinct Modes of Action.

Malaria continues to be one of the most devastating human diseases despite many efforts to limit its spread by prevention of infection or by pharmaceutical treatment of patients. We have conducted a screen for antiplasmodial compounds by using a natural product library. Here we report on cyclomarin A as a potent growth inhibitor of Plasmodium falciparum and the identification of its molecular target, diadenosine triphosphate hydrolase (PfAp3Aase), by chemical proteomics. Using a biochemical assay, we could show that cyclomarin A is a specific inhibitor of the plasmodial enzyme but not of the closest human homologue hFHIT. Co‐crystallisation experiments demonstrate a unique binding mode of the inhibitor. One molecule of cyclomarin A binds a dimeric PfAp3Aase and prevents the formation of the enzyme⋅substrate complex. These results validate PfAp3Aase as a new drug target for the treatment of malaria. We have previously elucidated the structurally unrelated regulatory subunit ClpC1 of the ClpP protease as the molecular target of cyclomarin A in Mycobacterium tuberculosis. Thus, cyclomarin A is a rare example of a natural product with two distinct and specific modes of action.

Structure-Based Library Design and Fragment Screening for the Identification of Reversible Complement Factor D Protease Inhibitors

Chronic dysregulation of alternative complement pathway activation has been associated with diverse clinical disorders including age-related macular degeneration and paroxysmal nocturnal hemoglobinurea. Factor D is a trypsin-like serine protease with a narrow specificity for arginine in the P1 position, which catalyzes the first enzymatic reaction of the amplification loop of the alternative pathway. In this article, we describe two hit finding approaches leading to the discovery of new chemical matter for this pivotal protease of the complement system: in silico active site mapping for hot spot identification to guide rational structure-based design and NMR screening of focused and diverse fragment libraries. The wealth of information gathered by these complementary approaches enabled the identification of ligands binding to different subpockets of the latent Factor D conformation and was instrumental for understanding the binding requirements for the generation of the first known potent noncovalent reversible Factor D inhibitors.

Discovery of C-(1-aryl-cyclohexyl)-methylamines as selective, orally available inhibitors of dipeptidyl peptidase IV.

The successful launches of dipeptidyl peptidase IV (DPP IV) inhibitors as oral anti-diabetics warrant and spur the further quest for additional chemical entities in this promising class of therapeutics. Numerous pharmaceutical companies have pursued their proprietary candidates towards the clinic, resulting in a large body of published chemical structures associated with DPP IV. Herein, we report the discovery of a novel chemotype for DPP IV inhibition based on the C-(1-aryl-cyclohexyl)-methylamine scaffold and its optimization to compounds which selectively inhibit DPP IV at low-nM potency and exhibit an excellent oral pharmacokinetic profile in the rat.

Exploring T Cell Reactivity to Gliadin in Young Children with Newly Diagnosed Celiac Disease

Class II major histocompatibility molecules confer disease risk in Celiac disease (CD) by presenting gliadin peptides to CD4 T cells in the small intestine. Deamidation of gliadin peptides by tissue transglutaminase creates immunogenic peptides presented by HLA-DQ2 and DQ8 molecules to activate proinflammatory CD4 T cells. Detecting gliadin specific T cell responses from the peripheral blood has been challenging due to low circulating frequencies and heterogeneity in response to gliadin epitopes. We investigated the peripheral T cell responses to alpha and gamma gliadin epitopes in young children with newly diagnosed and untreated CD. Using peptide/MHC recombinant protein constructs, we are able to robustly stimulate CD4 T cell clones previously derived from intestinal biopsies of CD patients. These recombinant proteins and a panel of α- and γ-gliadin peptides were used to assess T cell responses from the peripheral blood. Proliferation assays using peripheral blood mononuclear cells revealed more CD4 T cell responses to α-gliadin than γ-gliadin peptides with a single deamidated α-gliadin peptide able to identify 60% of CD children. We conclude that it is possible to detect T cell responses without a gluten challenge or in vitro stimulus other than antigen, when measuring proliferative responses.

Discovery of Highly Potent and Selective Small-Molecule Reversible Factor D Inhibitors Demonstrating Alternative Complement Pathway Inhibition in Vivo

The highly specific S1 serine protease factor D (FD) plays a central role in the amplification of the complement alternative pathway (AP) of the innate immune system. Genetic associations in humans have implicated AP activation in age-related macular degeneration (AMD), and AP dysfunction predisposes individuals to disorders such as paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS). The combination of structure-based hit identification and subsequent optimization of the center (S)-proline-based lead 7 has led to the discovery of noncovalent reversible and selective human factor D (FD) inhibitors with drug-like properties. The orally bioavailable compound 2 exerted excellent potency in 50% human whole blood in vitro and blocked AP activity ex vivo after oral administration to monkeys as demonstrated by inhibition of membrane attack complex (MAC) formation. Inhibitor 2 demonstrated sustained oral and ocular efficacy in a model of lipopolysaccharide (LPS)-induced systemic AP activation in mice expressing human FD.

trans-3,4-Disubstituted pyrrolidines as inhibitors of the human aspartyl protease renin. Part II: prime site exploration using an oxygen linker.

Recently, we reported on the discovery of (3S,4S)-disubstituted pyrrolidines (e.g., 2) as inhibitors of the human aspartyl protease renin. In our effort to further expand the scope of this novel class of direct renin inhibitors, a new sub-series was designed in which the prime site substituents are linked to the pyrrolidine core by a (3S)-amino functional group. In particular, analogs bearing the corresponding sulfonamide spacer (50, 51 and 54a) demonstrated a pronounced increase in in vitro potency compared to compound 2.