High-Throughput Screening to Identify Small Molecules That Selectively Inhibit APOL1 Protein Level in Podocytes.

High-throughput phenotypic screening is a key driver for the identification of novel chemical matter in drug discovery for challenging targets, especially for those with an unclear mechanism of pathology. For toxic or gain-of-function proteins, small-molecule suppressors are a targeting/therapeutic strategy that has been successfully applied. As with other high-throughput screens, the screening strategy and proper assays are critical for successfully identifying selective suppressors of the target of interest. We executed a small-molecule suppressor screen to identify compounds that specifically reduce apolipoprotein L1 (APOL1) protein levels, a genetically validated target associated with increased risk of chronic kidney disease. To enable this study, we developed homogeneous time-resolved fluorescence (HTRF) assays to measure intracellular APOL1 and apolipoprotein L2 (APOL2) protein levels and miniaturized them to 1536-well format. The APOL1 HTRF assay served as the primary assay, and the APOL2 and a commercially available p53 HTRF assay were applied as counterscreens. Cell viability was also measured with CellTiter-Glo to assess the cytotoxicity of compounds. From a 310,000-compound screening library, we identified 1490 confirmed primary hits with 12 different profiles. One hundred fifty-three hits selectively reduced APOL1 in 786-O, a renal cell adenocarcinoma cell line. Thirty-one of these selective suppressors also reduced APOL1 levels in conditionally immortalized human podocytes. The activity and specificity of seven resynthesized compounds were validated in both 786-O and podocytes.

Live Cell Membranome cDNA Screen: A Novel Homogenous Live Cell Binding Assay to Study Membrane Protein-Ligand Interaction.

Interactions between transmembrane receptors and their ligands play important roles in normal biological processes and pathological conditions. However, the binding partners for many transmembrane-like proteins remain elusive. To identify potential ligands of these orphan receptors, we developed a screening platform using a homogenous nonwash binding assay in live cells. A collection of ~1900 cDNA clones, encoding full-length membrane proteins, was assembled. As a proof of concept, cDNA clones were individually transfected into CHO-K1 cells in a high-throughput format, and soluble PD-L1-Fc fusion protein was used as bait. The interaction between the putative receptor and PD-L1-Fc was then detected by Alexa Fluor 647 conjugated anti-human immunoglobulin G Fc antibody and visualized using the Mirrorball fluorescence plate cytometer. As expected, PDCD1, the gene encoding programmed cell death protein 1 (PD-1), was revealed as the predominant hit. In addition, three genes that encode Fc receptors (FCGR1A, FCGR1B, and FCGR2A) were also identified as screen hits as the result of the Fc-tag fused to PD-L1, which has provided a reliable internal control for the screen. Furthermore, the potential of using a biotinylated ligand was explored and established to expand the versatility of the cDNA platform. This novel screening platform not only provides a powerful tool for the identification of ligands for orphan receptors but also has the potential for small-molecule target deconvolution.

Interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitors: an updated patent review (2016-2018).

INTRODUCTION: Interleukin-1 receptor-associated kinase 4 (IRAK4) is the most upstream kinase in Toll/Interleukin-1 receptor (TIR) signaling. Human and rodent genetics support the role of IRAK4 in immune function and the involvement of IRAK4-dependent signaling in certain cancers is hypothesized. The accumulating evidence has motivated the discovery of IRAK4 inhibitors that could be used therapeutically. AREAS COVERED: This review summarizes patents published in 2016-2018 claiming IRAK4 inhibitors. Representative analogues from each patent are presented with a focus on compounds that have been profiled in cellular and in vivo assays. EXPERT OPINION: The last three years have seen an increased number of IRAK4 inhibitors with which to assess the therapeutic potential of the target. At least 5 companies are believed to have advanced to the clinic. Pfizer is in phase II for rheumatoid arthritis (RA). The outcomes of these studies should inform on the therapeutic potential in autoimmune disease and cancer.

Efforts towards the optimization of a bi-aryl class of potent IRAK4 inhibitors.

IRAK4 has been identified as potential therapeutic target for inflammatory and autoimmune diseases. Herein we report the identification and initial SAR studies of a new class of pyrazole containing IRAK4 inhibitors designed to expand chemical diversity and improve off target activity of a previously identified series. These compounds maintain potent IRAK4 activity and desirable ligand efficiency. Rat clearance and a variety of off target activities were also examined, resulting in encouraging data with tractable SAR.

Discovery and Structure Enabled Synthesis of 2,6-Diaminopyrimidin-4-one IRAK4 Inhibitors.

We report the identification and synthesis of a series of aminopyrimidin-4-one IRAK4 inhibitors. Through high throughput screening, an aminopyrimidine hit was identified and modified via structure enabled design to generate a new, potent, and kinase selective pyrimidin-4-one chemotype. This chemotype is exemplified by compound 16, which has potent IRAK4 inhibition activity (IC50 = 27 nM) and excellent kinase selectivity (>100-fold against 99% of 111 tested kinases), and compound 31, which displays potent IRAK4 activity (IC50 = 93 nM) and good rat bioavailability (F = 42%).

Initial optimization and series evolution of diaminopyrimidine inhibitors of interleukin-1 receptor associated kinase 4.

IRAK4 plays a key role in TLR/IL-1 signaling. Previous efforts identified a series of aminopyrimidine IRAK4 inhibitors that possess good potency, but modest kinase selectivity. Exploration of substituents at the C-2 and C-5 positions generated compounds that maintained IRAK4 potency and improved kinase selectivity. Additionally, it was found that the pyrimidine core could be replaced with a pyridine and still retain potency and kinase selectivity. The optimization efforts led to compound 26 which had an IRAK4 IC50 of 0.7 nM, an IC50 of 55 nM on THP-1 cells stimulated with LPS, a TLR4 agonist, and greater than 100-fold selectivity versus 96% of a panel of 306 kinases.

Potent and Selective Amidopyrazole Inhibitors of IRAK4 That Are Efficacious in a Rodent Model of Inflammation.

IRAK4 is a critical upstream kinase in the IL-1R/TLR signaling pathway. Inhibition of IRAK4 is hypothesized to be beneficial in the treatment of autoimmune related disorders. A screening campaign identified a pyrazole class of IRAK4 inhibitors that were determined by X-ray crystallography to exhibit an unusual binding mode. SAR efforts focused on the identification of a potent and selective inhibitor with good aqueous solubility and rodent pharmacokinetics. Pyrazole C-3 piperidines were well tolerated, with N-sulfonyl analogues generally having good rodent oral exposure but poor solubility. N-Alkyl piperidines exhibited excellent solubility and reduced exposure. Pyrazoles possessing N-1 pyridine and fluorophenyl substituents were among the most active. Piperazine 32 was a potent enzyme inhibitor with good cellular activity. Compound 32 reduced the in vivo production of proinflammatory cytokines and was orally efficacious in a mouse antibody induced arthritis disease model of inflammation.

Discovery and hit-to-lead optimization of 2,6-diaminopyrimidine inhibitors of interleukin-1 receptor-associated kinase 4.

Interleukin receptor-associated kinase 4 (IRAK4) is a critical element of the Toll-like/interleukin-1 receptor inflammation signaling pathway. A screening campaign identified a novel diaminopyrimidine hit that exhibits weak IRAK4 inhibitory activity and a ligand efficiency of 0.25. Hit-to-lead activities were conducted through independent SAR studies of each of the four pyrimidine substituents. Optimal activity was observed upon removal of the pyrimidine C-4 chloro substituent. The intact C-6 carboribose is required for IRAK4 inhibition. Numerous heteroaryls were tolerated at the C-5 position, with azabenzothiazoles conferring the best activities. Aminoheteroaryls were preferred at the C-2 position. These studies led to the discovery of inhibitors 35, 36, and 38 that exhibit nanomolar inhibition of IRAK4, improved ligand efficiencies, and modest kinase selectivities.

Studies toward welwitindolinones: formal syntheses of N-methylwelwitindolinone C isothiocyanate and related natural products.

The formal syntheses of N-methylwelwitindolinone C isothiocyanate (4) and several other welwitindolinones 5-8 were achieved by the independent synthesis of 79. The synthesis featured a Lewis acid-mediated coupling between a heteroaryl carbinol and bis-TMS enol ether, an intramolecular enolate arylation, and an unprecedented intramolecular allylic alkylation of a γ-acyloxyenone.

Formal syntheses of naturally occurring welwitindolinones.

The formal syntheses of N-methylwelwitindolinone C isothiocyanate, N-methylwelwitindolinone C isonitrile, N-methylwelwitindolinone D isonitrile, 3-hydroxy-N-methylwelwitindolinone C isothiocyanate, and 3-hydroxy-N-methylwelwitindolinone C isonitrile are reported. The synthesis features several novel processes, including a Lewis acid mediated coupling between a benzylic-type heteroaromatic alcohol and a highly functionalized silyl ketene acetal, an intramolecular enolate arylation, and a regioselective, Pd(0)-catalyzed π-allylic cyclization of a γ-benzoyloxy enone moiety that is revealed by unmasking a furan ring.

Pyrazoloquinolines as PDE10A inhibitors: discovery of a tool compound.

A series of pyrazoloquinolines, possessing (hetero)arylhydroxymethyl substituents at the quinoline C-4 position were evaluated as PDE10A inhibitors. Among these, methylpyrimidyl analogue 15 was identified as having good rodent and monkey exposure, and a MED of 10 mg/kg in an in vivo model.

Discovery of orally active pyrazoloquinolines as potent PDE10 inhibitors for the management of schizophrenia.

A series of pyrazoloquinoline analogs have been synthesized and shown to bind to PDE10 with high affinity. From the SAR study and our lead optimization efforts, compounds 16 and 27 were found to possess potent oral antipsychotic activity in the MK-801 induced hyperactive rat model.

Application of palladium-catalyzed allylic arylation to the synthesis of a (+/-)-7-deoxypancratistatin analogue.

Palladium-catalyzed coupling of an aryl siloxane and an allylic carbonate proceeded in good yield to give an adduct that was converted to an analogue of (+/-)-7-deoxypancratistatin.

Siloxane-based cross-coupling of bromopyridine derivatives: studies for the synthesis of streptonigrin and lavendamycin.

Highly functionalized 4-bromopyridines were prepared and found to undergo fluoride-promoted, Pd-catalyzed cross-coupling with aryltrialkoxysilanes to give sterically demanding biaryls. The 3-nitro-4-bromopyridine derivative coupled in good yield with TBAT (tetrabutylammonium triphenyldifluorosilicate) to provide a biaryl adduct that serves as a model system for the total synthesis of the antitumor antibiotics streptonigrin and lavendamycin. [reaction: see text]