Discovery of a Novel Respiratory Syncytial Virus Replication Inhibitor.

A high-throughput screen of a Roche internal chemical library based on inhibition of the respiratory syncytial virus (RSV)-induced cytopathic effect (CPE) on HEp-2 cells was performed to identify RSV inhibitors. Over 2,000 hits were identified and confirmed to be efficacious against RSV infection in vitro Here, we report the discovery of a triazole-oxadiazole derivative, designated triazole-1, as an RSV replication inhibitor, and we characterize its mechanism of action. Triazole-1 inhibited the replication of both RSV A and B subtypes with 50% inhibitory concentration (IC50) values of approximately 1 µM, but it was not effective against other viruses, including influenza virus A, human enterovirus 71 (EV71), and vaccinia virus. Triazole-1 was shown to inhibit RSV replication when added at up to 8 h after viral entry, suggesting that it inhibits RSV after viral entry. In a minigenome reporter assay in which RSV transcription regulatory sequences flanking a luciferase gene were cotransfected with RSV N/P/L/M2-1 genes into HEp-2 cells, triazole-1 demonstrated specific and dose-dependent RSV transcription inhibitory effects. Consistent with these findings, deep sequencing of the genomes of triazole-1-resistant mutants revealed a single point mutation (A to G) at nucleotide 13546 of the RSV genome, leading to a T-to-A change at amino acid position 1684 of the L protein, which is the RSV RNA polymerase for both viral transcription and replication. The effect of triazole-1 on minigenome transcription, which was mediated by the L protein containing the T1684A mutation, was significantly reduced, suggesting that the T1684A mutation alone conferred viral resistance to triazole-1.

Discovery of (aza)indole derivatives as novel respiratory syncytial virus fusion inhibitors.

A new class of indole derivatives (3) have been identified as potent RSV fusion inhibitors. SAR exploration revealed that 5-Cl and the sulfonyl side chain of the indole scaffold are crucial for anti-RSV activity. Further optimization led to the discovery of a cyclic sulfone (8i) with 2 nM anti-RSV activity and a much improved PK profile compared to the non-cyclic sulfone counterpart.

Discovery of Ziresovir as a Potent, Selective, and Orally Bioavailable Respiratory Syncytial Virus Fusion Protein Inhibitor.

Ziresovir (RO-0529, AK0529) is reported here for the first time as a promising respiratory syncytial virus (RSV) fusion (F) protein inhibitor that currently is in phase 2 clinical trials. This article describes the process of RO-0529 as a potent, selective, and orally bioavailable RSV F protein inhibitor and highlights the in vitro and in vivo anti-RSV activities and pharmacokinetics in animal species. RO-0529 demonstrates single-digit nM EC50 potency against laboratory strains, as well as clinical isolates of RSV in cellular assays, and more than one log viral load reduction in BALB/c mouse model of RSV viral infection. RO-0529 was proven to be a specific RSV F protein inhibitor by identification of drug resistant mutations of D486N, D489V, and D489Y in RSV F protein and the inhibition of RSV F protein-induced cell-cell fusion in cellular assays.

Discovery of RG7834: The First-in-Class Selective and Orally Available Small Molecule Hepatitis B Virus Expression Inhibitor with Novel Mechanism of Action.

Chronic hepatitis B virus (HBV) infection is a serious public health burden, and current therapies cannot achieve satisfactory cure rate. There are high unmet medical needs of novel therapeutic agents with differentiated mechanism of action (MOA) from the current standard of care. RG7834, a compound from the dihydroquinolizinone (DHQ) chemical series, is a first-in-class highly selective and orally bioavailable HBV inhibitor which can reduce both viral antigens and viral DNA with a novel mechanism of action. Here we report the discovery of RG7834 from a phenotypic screening and the structure-activity relationship (SAR) of the DHQ chemical series. RG7834 can selectively inhibit HBV but not other DNA or RNA viruses in a virus panel screening. Both in vitro and in vivo profiles of RG7834 are described herein, and the data support further development of this compound as a chronic HBV therapy.

Discovery of Benzoazepinequinoline (BAQ) Derivatives as Novel, Potent, Orally Bioavailable Respiratory Syncytial Virus Fusion Inhibitors.

A novel benzoazepinequnoline (BAQ) series was discovered as RSV fusion inhibitors. BAQ series originated from compound 2, a hit from similarity-based virtual screening. In SAR exploration, benzoazepine allowed modifications in the head moiety. Benzylic sulfonyl on benzoazepine and 6-Me on quinoline were crucial for good anti-RSV activity. Although the basic amine in the head portion was crucial for anti-RSV activity, the attenuated basicity was required to reduce Vss. Introducing oxetane to the head portion led to discovery of compound 1, which demonstrated single-digit nM anti-RSV activity against different RSV strains, reasonable oral exposure in plasma, and 78-fold higher exposure in lung. Compound 1 also displayed 1 log viral reduction in a female BALB/c mice RSV model by b.i.d. oral dosing at 12.5 mg/kg. A single resistant mutant at L138F in fusion protein proved compound 1 to be a RSV fusion inhibitor.

Small molecule R1498 as a well-tolerated and orally active kinase inhibitor for hepatocellular carcinoma and gastric cancer treatment via targeting angiogenesis and mitosis pathways.

Protein kinases play important roles in tumor development and progression. Lots of kinase inhibitors have entered into market and show promising clinical benefits. Here we report the discovery of a novel small molecule, well-tolerated, orally active kinase inhibitor, R1498, majorly targeting both angiogenic and mitotic pathways for the treatment of hepatocellular carcinoma (HCC) and gastric cancer (GC). A series of biochemical and cell-based assays indicated that the target kinase cluster of R1498 included Aurora kinases and VEGFR2 et al. R1498 showed moderate in vitro growth inhibition on a panel of tumor cells with IC50 of micromole range. The in vivo anti-tumor efficacy of R1498 was evaluated on a panel of GC and HCC xenografts in a parallel comparison with another multikinase inhibitor sorafenib. R1498 demonstrated superior efficacy and toxicity profile over sorafenib in all test models with >80% tumor growth inhibition and tumor regression in some xenogratfts. The therapeutic potential of R1498 was also highlighted by its efficacy on three human GC primary tumor derived xenograft models with 10-30% tumor regression rate. R1498 was shown to actively inhibit the Aurora A activity in vivo, and decrease the vascularization in tumors. Furthermore, R1498 presented good in vivo exposure and therapeutic window in the pharmacokinetic and dose range finding studies. Theses evidences indicate that R1498 is a potent, well-tolerated, orally active multitarget kinase inhibitor with a unique antiangiogenic and antiproliferative profile, and provide strong confidence for further development for HCC and GC therapy.

Pharmacokinetic optimization of class-selective histone deacetylase inhibitors and identification of associated candidate predictive biomarkers of hepatocellular carcinoma tumor response.

Herein, we describe the pharmacokinetic optimization of a series of class-selective histone deacetylase (HDAC) inhibitors and the subsequent identification of candidate predictive biomarkers of hepatocellular carcinoma (HCC) tumor response for our clinical lead using patient-derived HCC tumor xenograft models. Through a combination of conformational constraint and scaffold hopping, we lowered the in vivo clearance (CL) and significantly improved the bioavailability (F) and exposure (AUC) of our HDAC inhibitors while maintaining selectivity toward the class I HDAC family with particular potency against HDAC1, resulting in clinical lead 5 (HDAC1 IC50 = 60 nM, mouse CL = 39 mL/min/kg, mouse F = 100%, mouse AUC after single oral dose at 10 mg/kg = 6316 h·ng/mL). We then evaluated 5 in a biomarker discovery pilot study using patient-derived tumor xenograft models, wherein two out of the three models responded to treatment. By comparing tumor response status to compound tumor exposure, induction of acetylated histone H3, candidate gene expression changes, and promoter DNA methylation status from all three models at various time points, we identified preliminary candidate response prediction biomarkers that warrant further validation in a larger cohort of patient-derived tumor models and through confirmatory functional studies.

Studies in catalytic C-H amination involving nitrene C-H insertion.

Stereoselective catalytic intermolecular C-H amination of complex molecules is reported. Site-selective functionalizations occur with very good yields up to 91% and excellent d.e.s up to 99%. However, the precise nature of the nitrene C-H insertion remains a matter of debate despite several physical organic experiments.

Toward a synthetically useful stereoselective C-H amination of hydrocarbons.

Reaction between a sulfur(VI) compound and an iodine(III) oxidant in the presence of a catalytic quantity (<=3 mol %) of a rhodium(II) catalyst leads to the formation of a chiral metallanitrene of unprecedented reactivity. The latter allows intermolecular C-H amination to proceed in very high yields up to 92% and excellent diastereoselectivities up to 99% with C-H bond containing starting materials as the limiting component. The scope of this C-H functionalization includes benzylic and allylic substrates as well as alkanes. Secondary positions react preferentially, but insertion into activated primary C-H bonds or sterically accessible tertiary sites is also possible. Cooperative effects between the nitrene precursor and the chiral catalyst at the origin of these good results have also been applied to kinetic resolution of racemic sulfonimidamide. This methodology paves the way to the use of Csp3-H bonds as synthetic precursors for the introduction of a nitrogen functionality into selected positions.

Zn(II)/amine-catalyzed coupling reaction of alkylidenemalonates with propargyl alcohol: a one-pot synthesis of methylenetetrahydrofurans.

[reaction: see text] A metal-catalyzed tandem 1,4-addition/cyclization between propargyl alcohol and a Michael acceptor, such as alkylidene malonate, has been developed. In the presence of catalytic amounts of zinc triflate [Zn(OTf)(2)] and triethylamine (Et(3)N), various 2-alkylidene-1,3-dicarbonyl compounds reacted with propargyl alcohol to give 3- or 4-methylene tetrahydrofurans in excellent yields.