P300/CBP inhibition sensitizes mantle cell lymphoma to PI3Kδ inhibitor idelalisib.

Mantle cell lymphoma (MCL) is a lymphoproliferative disorder lacking reliable therapies. PI3K pathway contributes to the pathogenesis of MCL, serving as a potential target. However, idelalisib, an FDA-approved drug targeting PI3Kδ, has shown intrinsic resistance in MCL treatment. Here we report that a p300/CBP inhibitor, A-485, could overcome resistance to idelalisib in MCL cells in vitro and in vivo. A-485 was discovered in a combinational drug screening from an epigenetic compound library containing 45 small molecule modulators. We found that A-485, the highly selective catalytic inhibitor of p300 and CBP, was the most potent compound that enhanced the sensitivity of MCL cell line Z-138 to idelalisib. Combination of A-485 and idelalisib remarkably decreased the viability of three MCL cell lines tested. Co-treatment with A-485 and idelalisib in Maver-1 and Z-138 MCL cell xenograft mice for 3 weeks dramatically suppressed the tumor growth by reversing the unsustained inhibition in PI3K downstream signaling. We further demonstrated that p300/CBP inhibition decreased histone acetylation at RTKs gene promoters and reduced transcriptional upregulation of RTKs, thereby inhibiting the downstream persistent activation of MAPK/ERK signaling, which also contributed to the pathogenesis of MCL. Therefore, additional inhibition of p300/CBP blocked MAPK/ERK signaling, which rendered maintaining activation to PI3K-mTOR downstream signals p-S6 and p-4E-BP1, thus leading to suppression of cell growth and tumor progression and eliminating the intrinsic resistance to idelalisib ultimately. Our results provide a promising combination therapy for MCL and highlight the potential use of epigenetic inhibitors targeting p300/CBP to reverse drug resistance in tumor.

Development of Small-Molecule Fluorescent Probes Targeting Enzymes.

As biological catalysts, enzymes are vital in controlling numerous metabolic reactions. The regulation of enzymes in living cells and the amount present are indicators of the metabolic status of cell, whether in normal condition or disease. The small-molecule fluorescent probes are of interest because of their high sensitivity and selectivity, as well as their potential for automated detection. Fluorescent probes have been useful in targeting particular enzymes of interest such as proteases and caspases. However, it is difficult to develop an ideal fluorescent probe for versatile purposes. In the future, the design and synthesis of enzyme-targeting fluorescent probes will focus more on improving the selectivity, sensitivity, penetration ability and to couple the fluorescent probes with other available imaging molecules/technologies.

Discovery of a Potent and Selective Degrader for USP7.

The tumor suppressor p53 is the most frequently mutated gene in human cancer and more than half of cancers contain p53 mutations. The development of novel and effective therapeutic strategies for p53 mutant cancer therapy is a big challenge and highly desirable. Ubiquitin-specific protease 7 (USP7), also known as HAUSP, is a deubiquitinating enzyme and proposed to stabilize the oncogenic E3 ubiquitin ligase MDM2 that promotes the proteosomal degradation of p53. Herein, we report the design and characterization of U7D-1 as the first selective USP7-degrading Proteolysis Targeting Chimera (PROTAC). U7D-1 showed selective and effective USP7 degradation, and maintained potent cell growth inhibition in p53 mutant cancer cells, with USP7 inhibitor showing no activity. These data clearly demonstrated the practicality and importance of PROTAC as a preliminary chemical tool for investigating USP7 protein functions and a promising method for potential p53 mutant cancer therapy.

Design, synthesis and biological evaluation of a novel spiro oxazolidinedione as potent p300/CBP HAT inhibitor for the treatment of ovarian cancer.

Histone acetylation is one of the most essential parts of epigenetic modification, mediating a variety of complex biological functions. In these procedure, p300/CBP could catalyze the acetylation of lysine 27 on histone 3 (H3K27ac), and had been reported to mediate tumorigenesis and development in a variety of tumors by enhancing chromatin transcription activity. Ovarian cancer, as an extremely malignant tumor, has also been observed to undergo abnormal acetylation of histones. However, whether the treatment of ovarian cancer could be achieved by inhibiting the acetylation activity of p300/CBP on H3K27 has not been well investigated. In this article, we modified the structure of p300/CBP HAT domain inhibitor A-485 and obtained a highly active small molecule known as 13f, which has an IC50 value of 0.49 nM for inhibiting the in vitro enzyme activity of p300, as well as the anti-proliferation IC50 value on ovarian cancer cell line OVCAR-3 was 153 nM. In addition, 13f had strong acetylase family selectivity, good metabolic stability and promising in vivo anti-tumor activity in OVCAR-3 xenograft model. The discovery of 13f revealed a more active chemical entity of the HATs domain of p300/CBP and provided a novel idea for the application of epigenetic inhibitors in the treatment of ovarian cancer.

Ruthenium(II)-Catalyzed Regioselective Ortho C-H Allenylation of Electron-Rich Aniline and Phenol Derivatives.

Ortho C-H allenylation of electron-rich benzene derivatives with propargylic alcohol derivatives has been a challenge, due to their great innate tendency toward a para C-H allenylation via an SN2'-type substitution process. Here, we described a Ru(II)-catalyzed regioselective ortho C-H allenylation of electron-rich aniline and phenol derivatives, which allows the previously challenging synthesis of a broad range of ortho allenylated aniline and phenol derivatives. More significantly, highly optically active fully substituted allenes can also be prepared with high enantiomeric excess via a highly efficient chirality transfer. No para C-H allenylation product was observed in the current catalytic system, thus showing a complete reversibility of the regioselectivity.

Complete genome sequence of an isolate of duck enteritis virus from China.

Here, we present the complete genomic sequence of duck enteritis virus (DEV) strain SD, isolated in China in 2012. The virus was virulent in experimentally infected 2-month-old ducks. The DEV SD genome is 160,945 base pairs (bp) in length. The viral genome sequence, when compared to that of strain DEV CSC, which was isolated in 1962, showed three discontinuous deletions of 101 bp, 48 bp and 417 bp within the inverted repeats. A comparison of the amino acid (aa) sequences of all ORFs of the CSC and SD isolates demonstrated an11-aa deletion, two single-aa deletions, and one single-aa deletion in LORF3, UL47, UL4, respectively. Moreover, 38 single aa variations were also detected in 24 different ORFs. These results will further advance our understanding of the genetic variations involved in evolution.

Rh(III)-Catalyzed Redox-Neutral Unsymmetrical C-H Alkylation and Amidation Reactions of N-Phenoxyacetamides.

A Rh(III)-catalyzed unsymmetrical C-H alkylation and amidation of N-phenoxyacetamides with diazo compounds has been developed under mild and redox-neutral conditions, producing dinitrogen as the only byproduct. The reaction represents the first example of one-step, unsymmetrical difunctionalization of two ortho-C-H bonds. Experimental and computational studies support that N-phenoxyacetamides most likely undergo an initial ortho-C-H alkylation with diazo compounds via a Rh(III)-catalyzed C-H activation, and the resulting Rh(III) intermediate subsequently undergoes an intramolecular oxidative addition into the O-N bond to form a Rh(V) nitrenoid species that is protonated and further directed toward electrophilic addition to the second ortho position of the phenyl ring. This work might provide a new direction for unsymmetrical C-H difunctionalization reactions in an efficient manner.

Discovery and biological evaluation of thiobarbituric derivatives as potent p300/CBP inhibitors.

Histone acetyltransferases (HATs) relieve transcriptional repression by preferentially acetylation of ε-amino group of lysine residues on histones. Dysregulation of HATs is strongly correlated with etiology of several diseases especially cancer, thus highlighting the utmost significance of the development of small molecule inhibitors against this potential therapeutic target. In the present study, through virtual screening and iterative optimization, we identified DCH36_06 as a bona fide, potent p300/CBP inhibitor. DCH36_06 mediated p300/CBP inhibition leading to hypoacetylation on H3K18 in leukemic cells. The suppression of p300/CBP activity retarded cell proliferation in several leukemic cell lines. In addition, DCH36_06 arrested cell cycle at G1 phase and induced apoptosis via activation of capase3, caspase9 and PARP that elucidated the molecular mechanism of its anti-proliferation activity. In transcriptome analysis, DCH36_06 altered downstream gene expression and apoptotic pathways-related genes verified by real-time PCR. Importantly, DCH36_06 blocked the leukemic xenograft growth in mice supporting its potential for in vivo use that underlies the therapeutic potential for p300/CBP inhibitors in clinical translation. Taken together, our findings suggest that DCH36_06 may serve as a qualified chemical tool to decode the acetylome code and open up new opportunities for clinical intervention.

Discovery and optimization of selective inhibitors of protein arginine methyltransferase 5 by docking-based virtual screening.

Protein arginine methyltransferase 5 (PRMT5) is a type II PRMT enzyme critical for diverse cellular processes and different types of cancers. Many efforts have been made to discover novel scaffold PRMT5 inhibitors. Herein, we report the discovery of DC_P33 as a hit compound of PRMT5 inhibitor, identified by molecular docking based virtual screening and 3H-labeled radioactive methylation assays. Structure-activity relationship (SAR) analysis was performed on the analogs of DC_P33 and then structural modifications were done to improve its activity. Among the derivatives, the compound DC_C01 displayed an IC50 value of 2.8 µM, and good selectivity toward PRMT1, EZH2 and DNMT3A. Moreover, DC_C01 exhibited anti-proliferation activities against Z-138, Maver-1, and Jeko-1 cancer cells with EC50 values of 12 µM, 12 µM, and 10.5 µM, respectively. Taken together, these results contribute to the development of specific inhibitors against PRMT5 and cancer therapy.

Identification of novel small-molecule inhibitors targeting menin-MLL interaction, repurposing the antidiarrheal loperamide.

Leukemia with a mixed lineage leukemia (MLL) rearrangement, which harbors a variety of MLL fusion proteins, has a poor prognosis despite the latest improved treatment options. Menin has been reported to be a required cofactor for the leukemogenic activity of MLL fusion proteins. Thus, the disruption of the protein-protein interactions between menin and MLL represents a very promising strategy for curing MLL leukemia. Making use of menin-MLL inhibitors with a shape-based scaffold hopping approach, we have discovered that the antidiarrheal loperamide displays previously unreported mild inhibition for the menin-MLL interaction (IC50 = 69 ± 3 µM). In an effort to repurpose this drug, a series of chemical modification analyses was performed, and three of the loperamide-based analogues, DC_YM21, DC_YM25 and DC_YM26 displayed better activities with IC50 values of 0.83 ± 0.13 µM, 0.69 ± 0.07 µM and 0.66 ± 0.05 µM, respectively. Further treatment with DC_YM21 demonstrated potent and selective blockage of proliferation and induction of both cell cycle arrest and differentiation of leukemia cells harboring MLL translocations, which confirmed the specific mechanism of action. In conclusion, molecules of a novel scaffold targeting menin-MLL interactions were reported and they may serve as new potential therapeutic agents for MLL leukemia.

Iridium(III)-catalyzed C-7 selective C-H alkynylation of indolines at room temperature.

An iridium-catalyzed direct C-7 selective C-H alkynylation of indolines at room temperature, for the first time, has been developed via C-H bond activation. Furthermore, the first example of direct C-H alkynylation of carbazoles at the C1 position is also achieved. More importantly, the resulting product can be readily transformed into C7-alkynylated indoles, further widening the C-7 derivatization of indoles and highlighting the synthetic utility of this methodology.

Access to Six- and Seven-Membered 1,7-Fused Indolines via Rh(III)-Catalyzed Redox-Neutral C7-Selective C-H Functionalization of Indolines with Alkynes and Alkenes.

We report herein a new strategy for the Rh(III)-catalyzed redox-neutral C7-selective C-H activation/annulation of indolines to rapidly access various privileged 1,7-fused indolines by utilizing an oxidizing-directing group. For example, a Rh(III)-catalyzed redox-neutral C7-selective C-H functionalization of indolines with arylalkynes is described to directly access 7-membered 1,7-fused indolines. Moreover, an unprecedented intramolecular addition of an alkenyl-Cp*Rh(III) species to a carbamoyl moiety occurred to give 1H-pyrroloquinolinones when employing alkyl alkynes. Additionally, an efficient Rh(III)-catalyzed redox-neutral C7-selective C-H activation/alkenylation/aza-Michael addition of indolines is also developed to give 6-membered 1,7-fused indolines. The advantages of these processes are as follows: (1) mild and simple reaction conditions; (2) no need for an external oxidant; (3) broad scope of substrates; and (4) valuable six- or seven-membered 1,7-fused indolines as products.

A [4+1] Cyclative Capture Approach to 3H-Indole-N-oxides at Room Temperature by Rhodium(III)-Catalyzed CH Activation.

The rhodium(III)-catalyzed [3+2] CH cyclization of aniline derivatives and internal alkynes represents a useful contribution to straightforward synthesis of indoles. However, there is no report on the more challenging synthesis of pharmaceutically important N-hydroxyindoles and 3H-indole-N-oxides. Reported herein is the first rhodium(III)-catalyzed [4+1] CH oxidative cyclization of nitrones with diazo compounds to access 3H-indole-N-oxides. More significantly, this reaction proceeds at room temperature and has been extended to the synthesis of N-hydroxyindoles and N-hydroxyindolines.

Redox-neutral rhodium-catalyzed C-H functionalization of arylamine N-oxides with diazo compounds: primary C(sp(3))-H/C(sp(2))-H activation and oxygen-atom transfer.

An unprecedented rhodium(III)-catalyzed regioselective redox-neutral annulation reaction of 1-naphthylamine N-oxides with diazo compounds was developed to afford various biologically important 1H-benzo[g]indolines. This coupling reaction proceeds under mild reaction conditions and does not require external oxidants. The only by-products are dinitrogen and water. More significantly, this reaction represents the first example of dual functiaonalization of unactivated a primary C(sp(3) )H bond and C(sp(2) )H bond with diazocarbonyl compounds. DFT calculations revealed that an intermediate iminium is most likely involved in the catalytic cycle. Moreover, a rhodium(III)-catalyzed coupling of readily available tertiary aniline N-oxides with α-diazomalonates was also developed under external oxidant-free conditions to access various aminomandelic acid derivatives by an O-atom-transfer reaction.

Rhodium(III)-catalyzed intramolecular redox-neutral annulation of tethered alkynes: formal total synthesis of (±)-goniomitine.

A Rh(III)-catalyzed intramolecular redox-neutral atom-economic annulation of a tethered alkyne has been developed to efficiently construct 2-amidealkyl indoles with completely reversed regioselectivity by a C-H activation pathway. Furthermore, using the Rh(III)-catalyzed C-H activation/annulation as a key step, a one-pot synthesis of pyrido[1,2-a]indoles has also been developed and applied to a highly efficient formal total synthesis of (±)-goniomitine.

Rhodium-catalyzed direct amination of arenes with nitrosobenzenes: a new route to diarylamines.

A Rh(III) -catalyzed addition of aryl CH bonds to nitrosobenzenes, followed by cleavage of the resulting hydroxylamines in situ, has been reported. Different directing groups, such as N-based heterocycles and ketoximes, can be used in this CH amination process, providing valuable diarylamines in excellent yields. Most importantly, this process provides a new method for attaching arylamine groups to aromatic rings.

Rhodium(III)- and iridium(III)-catalyzed C7 alkylation of indolines with diazo compounds.

A Rh(III)-catalyzed procedure for the C7-selective C-H alkylation of various indolines with α-diazo compounds at room temperature is reported. The advantages of this process are: 1) simple, mild, and pH-neutral reaction conditions, 2) broad substrate scope, 3) complete regioselectivity, 4) no need for an external oxidant, and 5) N2 as the sole byproduct. Furthermore, alkylation and bis-alkylation of carbazoles at the C1 and C8 positions have also been developed. More significantly, for the first time, a successful Ir(III)-catalyzed intermolecular insertion of arene C-H bonds into α-diazo compounds is reported.

Rhodium-catalyzed directed sulfenylation of arene C-H bonds.

The rhodium-catalyzed intermolecular direct C-H thiolation of arenes with aryl and alkyl disulfides was developed for the first time to provide a convenient route to aryl thioethers. This strategy is compatible with many different directing groups and exhibits excellent functional group tolerance. More significantly, mono- or dithiolation can be selectively achieved, thus providing a straightforward way for selective preparation of aryl thioethers and dithioethers.

Synthesis of 5α-cholestan-6-one derivatives and their inhibitory activities of NO production in activated microglia: discovery of a novel neuroinflammation inhibitor.

Glial activation-mediated neuroinflammation plays a pivotal role in the process of several neuroinflammatory diseases including stroke, Alzheimer's diseases, Parkinson's diseases, multiple sclerosis and ischemia. Inhibition of microglial activation may ameliorate neuronal degeneration under the inflammatory conditions. In the present study, a number of 5α-cholestan-6-one derivatives were prepared and the anti-inflammatory effects of these compounds were evaluated in LPS-stimulated BV-2 microglia cells. Those derivatives were synthesized from readily available hyodeoxycholic acid (1). Among the tested compounds, several analogs (16-18, 25, 35, 38) exhibited potent inhibitory activities on nitric oxide production with no or weak cell toxicity. Compound 16 also significantly suppressed the expression of TNF-α, interleukin (IL)-1ß, cyclooxygenase (COX-2) as well as inducible nitric oxide synthase (iNOS) in LPS-stimulated BV-2 microglia cells. In addition, compound 16 markedly reduced infarction volume in a focal ischemic mice model.

Switchable Regioselective C-H Activation/Annulation of Acrylamides with Alkynes for the Synthesis of 2-Pyridones.

A catalyst-based switchable regioselective C-H activation/annulation of acrylamides with propargyl carbonates has been developed, delivering C5 or C6 alkenyl substituted 2-pyridones. This robust protocol proceeds with a broad substrate scope and good functional group tolerance under redox-neutral reaction conditions. More significantly, this reaction is highly effective with previously challenging unsymmetrical alkynes, including unbiased alkyl-alkyl substituted alkynes, with perfect and switchable regioselectivity. Additionally, mechanistic studies and DFT calculations were performed to shed light on the switchable regioselectivity.