Inter-molecular crosslinking activity is engendered by the dimeric form of transglutaminase 2.

Transglutaminase 2 (TGase 2) catalyzes a crosslink between protein bound-glutamine and -lysine. We proposed the mechanism of TGase 2 activation depends on conformation change from unfolded monomer to unfolded dimer. We found that TGase 2 has temperature-sensitive conformation change system at 30 °C. Small-angle X-ray scattering analysis showed that the enzyme was maintained as an unfolded monomer at temperatures below 30 °C, but changed to an unfolded dimer at over 30 °C. Mass analysis revealed that the C-terminus of TGase 2 was the critical region for dimerization. Furthermore, this conformational switch creates new biochemical reactivity that catalyzed inter-molecular crosslink at above 30 °C as an unfolded dimer of TGase 2 while catalyzed intra-molecular crosslink at below 30 °C as an unfolded monomer of TGase 2. The mechanism of TGase 2 activation depends on temperature-sensitive conformation change from unfolded monomer to unfolded dimer at over 30 °C. Furthermore, inter-molecular crosslinking activity is generated by the dimeric form of TGase 2. TGase 2 switches its conformation from a monomer to a dimer following a change in temperature, which engendered unique catalytic function of enzyme as inter-molecular crosslinking activity with calcium.

Assessment of pharmacokinetics, bioavailability and protein binding of anacetrapib in rats by a simple high-performance liquid chromatography-tandem mass spectrometry method.

Anacetrapib is a potent and selective CETP inhibitor and is undergoing phase III clinical trials for the treatment of dyslipidemia. A simple and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the quantification of anacetrapib in rat plasma was developed and validated using an easily purchasable compound, chlorpropamide, as an internal standard (IS). A minimal volume of rat plasma sample (20 µL) was prepared by a single-step deproteinization procedure with 80 µL of acetonitrile. Chromatographic separation was performed using Kinetex C18 column with a gradient mobile phase consisting of water and acetonitrile containing 0.1% formic acid at a flow rate of 0.3 mL/min. Mass spectrometric detection was performed using selected reaction monitoring modes at the mass/charge transitions m/z 638 → 283 for anacetrapib and m/z 277 → 175 for IS. The assay was validated to demonstrate the selectivity, linearity, precision, accuracy, recovery, matrix effect and stability. The lower limit of quantification was 5 ng/mL. This LC-MS/MS assay was successfully applied in the rat plasma protein binding and pharmacokinetic studies of anacetrapib. The fraction of unbound anacetrapib was determined to be low (ranging from 5.66 to 12.3%), and the absolute oral bioavailability of anacetrapib was 32.7%.

Groebke-Blackburn-Bienaymé Reaction for DNA-Encoded Library Technology.

This study presents a DNA-compatible synthesis of diverse 5-arylimidazo[1,2-a]pyridin-3-amine derivatives using the Suzuki-Miyaura reaction, followed by a Groebke-Blackburn-Bienaymé (GBB) reaction. The GBB reaction demonstrates a wide substrate scope, mild one-pot reaction conditions, and compatibility with subsequent enzymatic ligation, highlighting its potential in DNA-encoded library technology.

Synthesis of cyclopentenols and cyclopentenones via nickel-catalyzed reductive cycloaddition.

Strategies for the reductive cycloaddition of enals or enoates with alkynes have been developed. The enal-alkyne cycloaddition directly affords cyclopentenols, whereas the enoate-alkyne cycloaddition affords the analogous cyclopentenones. The mechanism of these processes likely involves formation and protonation of a metallacyclic intermediate. The general strategy provides a straightforward entry to five-membered ring products from simple, stable π-systems.

DNA-Encoded Library Screening as Core Platform Technology in Drug Discovery: Its Synthetic Method Development and Applications in DEL Synthesis.

DNA-encoded library technology (DELT) was introduced to our medicinal chemistry society more than 20 years ago. The application of DELT in the development of clinical candidates has been actively reported in the literature recently. A few representative examples include RIP1K inhibitors for inflammatory diseases and sEH inhibitors for endothelial dysfunction or abnormal tissue repair, among many others. Here, the authors would like to recall the recent developments in on-DNA synthetic methodologies for DEL construction and to analyze recent examples in the literature of DELT-based drug development efforts pursued in both the academic and industrial sectors. With this perspective, we hope to provide a useful summary of recent DELT-based drug discovery research and to discuss the future scope of DELT in medicinal chemistry.

Recent Development of Aminoacyl-tRNA Synthetase Inhibitors for Human Diseases: A Future Perspective.

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes that ligate amino acids to tRNAs and translate the genetic code during protein synthesis. Their function in pathogen-derived infectious diseases has been well established, which has led to the development of small molecule therapeutics. The applicability of ARS inhibitors for other human diseases, such as fibrosis, has recently been explored in the clinical setting. There are active studies to find small molecule therapeutics for cancers. Studies on central nervous system (CNS) disorders are burgeoning as well. In this regard, we present a concise analysis of the recent development of ARS inhibitors based on small molecules from the discovery research stage to clinical studies as well as a recent patent analysis from the medicinal chemistry point of view.

Vinylaluminum addition to sulfinimines (N-sulfinyl imines). Asymmetric synthesis of anti-alpha-alkyl beta-amino esters.

Addition of vinylaluminum NMO reagents to N-(p-toluenesufinyl)- and N-(2-methypropanesulfinyl)-derived sulfinimines gives N-sulfinyl aza-Morita-Baylis-Hillman products (dr = 7:1 to 12:1) that result from addition of the reagent from the least hindered direction. Hydrogenation of the aza-MBH adducts with a Rh(I) catalyst affords anti-alpha-substituted N-sulfinyl-beta-amino esters in good yield and high dr (10:1 to 21:1).

Total synthesis of (5R,6R,8R,9S)-(-)-5,9Z-indolizidine 221T using sulfinimine-derived N-sulfinyl beta-amino ketones.

The first total asymmetric synthesis of the poison frog alkaloid (-)-221T, a 5,6,8-trisubstituted indolizidine is described. The key core piperidine ring was constructed via an acid catalyzed intramolecular cascade Mannich cyclization reaction of a N-sulfinyl syn-alpha-methyl beta-amino ketone and crotonaldehyde. The beta-amino ketone was prepared via the reaction of prochiral lithium Weinreb amide enolate with an enantiopure N-2,4,6-triisopropylphenylsulfinyl imine.

Recent Development of Small Molecule Glutaminase Inhibitors.

Glutaminase (GLS), which is responsible for the conversion of glutamine to glutamate, plays a vital role in up-regulating cell metabolism for tumor cell growth and is considered to be a valuable therapeutic target for cancer treatment. Based on this important function of glutaminase in cancer, several GLS inhibitors have been developed in both academia and industry. Most importantly, Calithera Biosciences Inc. is actively developing the glutaminase inhibitor CB-839 for the treatment of various cancers, and it is currently being evaluated in phase 1 and 2 clinical trials. In this review, recent efforts to develop small molecule glutaminase inhibitors that target glutamine metabolism in both preclinical and clinical studies are discussed. In particular, more emphasis is placed on CB-839 because it is the only small molecule GLS inhibitor being studied in a clinical setting. The inhibition mechanism is also discussed based on X-ray structure studies of thiadiazole derivatives present in glutaminase inhibitor BPTES. Finally, recent medicinal chemistry efforts to develop a new class of GLS inhibitors are described in the hopes of providing useful information for the next generation of GLS inhibitors.

Large dynamic range photon detector with a temperature-stabilized Si-based multi-pixel photon counter.

We present an efficient fluorescence detector in the visible region of the spectrum with a photon detection dynamic range over 10 (6) photons/s made of a temperature-stabilized Si-based multi-pixel photon counter at temperature down to 5 degrees C. We show that effective cooling of the device by means of a compact thermo-electric cooler brings several advantages, such as high gain, low dark noise rate, and thus high signal-to-noise ratio in the efficient fluorescence detection at 398.9 nm from the (1)S(0) ? (1)P(1) transition of the ytterbium atoms in an effusive atomic beam. We present also a comparison of the fluorescence detection efficiencies between the device and a side-on photo-multiplier tube with known gain positioned at the symmetric location from the ytterbium atomic beam.

Asymmetric synthesis of syn-alpha-substituted beta-amino ketones by using sulfinimines and prochiral Weinreb amide enolates.

Syn-alpha-substituted beta-amino Weinreb amides are new chiral building blocks for asymmetric synthesis of syn-alpha-substituted beta-amino acids, aldehydes, and ketones and are prepared by addition of prochiral lithium enolates of Weinreb amides to sulfinimines (N-sulfinyl imines).

Recent developments in small molecule therapies for renal cell carcinoma.

Renal cell carcinoma (RCC) is the most common type of kidney cancer in adults and is known to be the 10th most common type of cancer in the world. Most of the currently available RCC drugs are tyrosine kinase inhibitors (TKIs). However, combination therapies of TKIs and immune checkpoint inhibitors such as programmed cell death protein 1 (PD-1) and programmed cell death protein 1 ligand 1 (PD-L1) inhibitors are the focus of most of the final stage clinical trials. Meanwhile, other small molecule therapies for RCC that target indoleamine-2,3-dioxygenase (IDO1), glutaminase, C-X-C chemokine receptor 4 (CXCR4), and transglutaminase 2 (TG2) are emerging as the next generation of therapeutics. In this review, these three major streams for the development of small molecule drugs for RCC are described.

Recent Progress in the Development of Transglutaminase 2 (TGase2) Inhibitors.

Transglutaminase 2 (TGase2, TG2) activity has been implicated in the pathogenesis of a number of unrelated disorders, including celiac, neurological, and renal diseases, and various forms of cancer. It has been suggested that TGase2 activity, such as cross-linking, deamidation, and GTP-related activity, is associated with each disease. Continuing efforts to develop small molecule TG2 inhibitors are ongoing. To develop a new class of TG2 inhibitors, the factors impeding the development of TG2 inhibitors have been identified. Additionally, the conformational effect of TG2 enzyme in regard to its pathological roles, in vitro screening methods, recently discovered TG2 inhibitors, and preclinical evaluations are discussed with a brief summary of current TG2 inhibitor pipelines under the clinical setting.

Progress in Discovery of KIF5B-RET Kinase Inhibitors for the Treatment of Non-Small-Cell Lung Cancer.

A new chimeric fusion transcript of KIF5B (the kinesin family 5B gene) and the RET (Rearranged during Transcription) oncogene, KIF5B-RET, was found in 1-2% of lung adenocarcinomas (LADCs) in late 2011. Several related clinical trials for non-small-cell lung cancer (NSCLC) with KIF5B-RET rearrangements using existing RET inhibitors, such as lenvatinib, vandetanib, sunitinib, ponatinib, cabozantinib, and AUY922, have been swiftly initiated by the discovery of the KIF5B-RET fusion gene. Anti-RET activity and the status of clinical development of these known RET tyrosine kinase inhibitors (TKIs) for KIF5B-RET fusion-positive NSCLC are discussed. A kinase inhibitor that can target a driver mutation specifically may lead to a superior clinical benefit compared with broad-spectrum kinase inhibitors. In this regard, an analysis of the structure of RET kinase and its complex with known RET inhibitors are also briefly discussed.

Cabozantinib for the treatment of non-small cell lung cancer with KIF5B-RET fusion. An example of swift repositioning.

A new chimeric fusion transcript of KIF5B (the kinesin family 5B gene) and the RET (Rearranged during Transcription) oncogene, KIF5B-RET, was found in 1-2% of lung adenocarcinomas (LADCs) in 2012. Several related clinical trials for non-small cell lung cancer (NSCLC) with KIF5B-RET rearrangements using existing RET inhibitors, such as cabozantinib, lenvatinib, vandetanib, sunitinib, ponatinib, and AUY922, have been swiftly initiated by the discovery of the KIF5B-RET fusion gene. Anti-RET activity and the status of clinical development of cabozantinib for KIF5B-RET fusion-positive NSCLC are discussed.

Injectable hydrogels derived from phosphorylated alginic acid calcium complexes.

Phosphorylation of sodium alginate salt (NaAlg) was carried out using H3PO4/P2O5/Et3PO4 followed by acid-base reaction with Ca(OAc)2 to give phosphorylated alginic acid calcium complexes (CaPAlg), as a water dispersible alginic acid derivative. The modified alginate derivatives including phosphorylated alginic acid (PAlg) and CaPAlg were characterized by nuclear magnetic resonance spectroscopy for (1)H, and (31)P nuclei, high resolution inductively coupled plasma optical emission spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. CaPAlg hydrogels were prepared simply by mixing CaPAlg solution (2w/v%) with NaAlg solution (2w/v%) in various ratios (2:8, 4:6, 6:4, 8:2) of volume. No additional calcium salts such as CaSO4 or CaCl2 were added externally. The gelation was completed within about 3-40min indicating a high potential of hydrogel delivery by injection in vivo. Their mechanical properties were tested to be ≤6.7kPa for compressive strength at break and about 8.4kPa/mm for elastic modulus. SEM analysis of the CaPAlg hydrogels showed highly porous morphology with interconnected pores of width in the range of 100-800µm. Cell culture results showed that the injectable hydrogels exhibited comparable properties to the pure alginate hydrogel in terms of cytotoxicity and 3D encapsulation of cells for a short time period. The developed injectable hydrogels showed suitable physicochemical and mechanical properties for injection in vivo, and could therefore be beneficial for the field of soft tissue engineering.

Preparation of homoallylic alcohols by nickel-catalyzed cyclizations of allenyl aldehydes.

The direct cyclization of allenyl aldehydes with organozincs in the presence of Ni(COD)(2) provides synthetically versatile homoallylic alcohols. Both monosubstituted and 1,3-disubstituted allenes participate in the process, with the latter allowing preparation of stereochemically defined trisubstituted alkenes. [reaction: see text]

Cascaded two-photon spectroscopy of Yb atoms with a transportable effusive atomic beam apparatus.

We present a transportable effusive atomic beam apparatus for cascaded two-photon spectroscopy of the dipole-forbidden transition (6s(2)(1)S0↔ 6s7s (1)S0) of Yb atoms. An ohmic-heating effusive oven is designed to have a reservoir volume of 1.6 cm(3) and a high degree of atomic beam collimation angle of 30 mrad. The new atomic beam apparatus allows us to detect the spontaneously cascaded two-photons from the 6s7s(1)S0 state via the intercombination 6s6p(3)P1 state with a high signal-to-noise ratio even at the temperature of 340 °C. This is made possible in our apparatus because of the enhanced atomic beam flux and superior detection solid angle.