The T-cell-specific retinoic acid receptor (RAR)-related orphan receptor-γ (RORγt) is a key transcription factor for the production of pro-inflammatory Th17 cytokines, which are implicated in the pathogenesis of autoimmune diseases. Over the years, several structurally diverse RORγt inverse agonists have been reported, but combining high potency and good physicochemical properties has remained a challenging task. We recently reported a new series of inverse agonists based on an imidazopyridine core with good physicochemical properties and excellent selectivity. Herein we report eight new X-ray crystal structures for different classes of natural and synthetic compounds, including examples selected from the patent literature. Analysis of their respective binding modes revealed insight into the molecular mechanisms that lead to agonism, antagonism, or inverse agonism. We report new molecular mechanisms for RORγt agonism and propose a separation of the inverse agonists into two classes: those that act via steric clash and those that act via other mechanisms (for the latter, co-crystallization with a co-activator peptide and helix 12 in the agonist position is still possible). For the non-steric clash inverse agonists, we propose a new mechanism ("water trapping") which can be combined with other mechanisms (e.g., close contacts with H479). In addition, we compare the interactions made for selected compounds in the "back pocket" near S404 and in the "sulfate pocket" near R364 and R367. Taken together, these new mechanistic insights should prove useful for the design and optimization of further RORγt modulators.

The predominant expression of phosphoinositide 3-kinase δ (PI3Kδ) in leukocytes and its critical role in B and T cell functions led to the hypothesis that selective inhibitors of this isoform would have potential as therapeutics for the treatment of allergic and inflammatory disease. Targeting specifically PI3Kδ should avoid potential side effects associated with the ubiquitously expressed PI3Kα and β isoforms. We disclose how morphing the heterocyclic core of previously discovered 4,6-diaryl quinazolines to a significantly less lipophilic 5,6,7,8-tetrahydropyrido[4,3-]pyrimidine, followed by replacement of one of the phenyl groups with a pyrrolidine-3-amine, led to a compound series with an optimal on-target profile and good ADME properties. A final lipophilicity adjustment led to the discovery of CDZ173 (leniolisib), a potent PI3Kδ selective inhibitor with suitable properties and efficacy for clinical development as an anti-inflammatory therapeutic. , CDZ173 inhibits a large spectrum of immune cell functions, as demonstrated in B and T cells, neutrophils, monocytes, basophils, plasmocytoid dendritic cells, and mast cells., CDZ173 inhibits B cell activation in rats and monkeys in a concentration- and time-dependent manner. After prophylactic or therapeutic dosing, CDZ173 potently inhibited antigen-specific antibody production and reduced disease symptoms in a rat collagen-induced arthritis model. Structurally, CDZ173 differs significantly from the first generation of PI3Kδ and PI3Kγδ-selective clinical compounds. Therefore, CDZ173 could differentiate by a more favorable safety profile. CDZ173 is currently in clinical studies in patients suffering from primary Sjögren's syndrome and in APDS/PASLI, a disease caused by gain-of-function mutations of PI3Kδ.

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Inhibition of the lipid kinase PI3Kδ is a promising principle to treat B and T cell driven inflammatory diseases. Using a scaffold deconstruction−reconstruction strategy, we identified 4-aryl quinazolines that were optimized into potent PI3Kδ isoform selective analogues with good pharmacokinetic properties. With compound 11, we illustrate that biochemical PI3Kδ inhibition translates into modulation of isoform-dependent immune cell function (human, rat, and mouse). After oral administration of compound 11 to rats, proximal PD markers are inhibited, and dose-dependent efficacy in a mechanistic plaque forming cell assay could be demonstrated.

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Efficient and versatile protocols for the synthesis of chiral analogues of the novel immunomodulator FTY720 and its phosphate are described. These synthetic procedures allow for broad structural variation and deliver essential tools to further elucidate FTY720's novel mechanism of action. OP), 6.86 (d, J = 8 Hz, 2 H arom ), 7.13 (d, J = 8 Hz, 2 H arom ). MS (ES+): m/z = 398.3 (MH) + , 795.3 (2 M + H) + . MS (ES-): m/z = 396.3 (M -H) -, 397.3 (M -), 793.3 (2M -H) -. (6) 1 H NMR (400 MHz, DMSO-d 6 ): d = 0.90 (t, J = 7 Hz, 3 H, CH 3 ), 1.25-1.53 [m, 10 H, CH 2 , (CH 2 ) 4 ], 1.65-1.85 (m, 6 H, 2 × C q -CH 2 , OCH 2 CH 2 ), 2.53 (m, 2 H, PhCH 2 ), 3.43 (m, 2 H, CH 2 OH), 3.88 (d, J = 7 Hz, 2 H, CH 2 OP), 3.94 (t, J = 7 Hz, 2 H, PhOCH 2 ), 6.86 (d, J = 8 Hz, 2 H arom ), 7.12 (d, J = 8 Hz, 2 H arom ). Phosphoric Acid Mono-{(S)-2-amino-2-[2-(4-heptyloxyphenyl)ethyl]-5-hydroxypentyl} EsterMS (ES+): m/z = 418.3 (MH) + , 873.4 (2 M + K) + . MS (ES-): m/z = 416.4 (M -H) -, 417.3 (M -), 833.5 (2 M -H) -.

The transcription factor RORγt is an attractive drug-target due to its role in the differentiation of IL-17 producing Th17 cells that play a critical role in the etiopathology of several autoimmune diseases. Identification of starting points for RORγt inverse agonists with good properties has been a challenge. We report the identification of a fragment hit and its conversion into a potent inverse agonist through fragment optimization, growing and merging efforts. Further analysis of the binding mode revealed that inverse agonism was achieved by an unusual mechanism. In contrast to other reported inverse agonists, there is no direct interaction or displacement of helix 12 observed in the crystal structure. Nevertheless, compound 9 proved to be efficacious in a delayed-type hypersensitivity (DTH) inflammation model in rats.

Retinoic acid receptor-related orphan receptor gamma-t (RORγt) is considered to be the master transcription factor for the development of Th17 cells that produce proinflammatory cytokines such as IL-17A. Overproportionate Th17 cell abundance is associated with the pathogenesis of many inflammatory conditions including psoriasis. In a high-throughput fluorescence resonance energy transfer (FRET) screen, we identified compound 1 as a hit with promising lipophilic efficiency (LipE). Using structure-based drug design based on a number of X-ray cocrystal structures, we morphed this hit class into potent imidazoles, exemplified by compound 3. To improve the poor absorption, distribution, metabolism, and excretion (ADME) properties of neutral imidazoles, we extended our ligands with carboxylic acid substituents toward a polar, water-rich area of the protein. This highly lipophilicity-efficient modification ultimately led to the discovery of compound 14, a potent and selective inhibitor of RORγt with good ADME properties and excellent in vivo pharmacokinetics. This compound showed good efficacy in an in vivo delayed-type hypersensitivity pharmacology model in rats.