Masatoshi Karashima

CLK-dependent exon recognition and conjoined gene formation revealed with a novel small molecule inhibitor

CDC-like kinase phosphorylation of serine/arginine-rich proteins is central to RNA splicing reactions. Yet, the genomic network of CDC-like kinase-dependent RNA processing events remains poorly defined. Here, we explore the connectivity of genomic CDC-like kinase splicing functions by applying graduated, short-exposure, pharmacological CDC-like kinase inhibition using a novel small molecule (T3) with very high potency, selectivity, and cell-based stability. Using RNA-Seq, we define CDC-like kinase-responsive alternative splicing events, the large majority of which monotonically increase or decrease with increasing CDC-like kinase inhibition. We show that distinct RNA-binding motifs are associated with T3 response in skipped exons. Unexpectedly, we observe dose-dependent conjoined gene transcription, which is associated with motif enrichment in the last and second exons of upstream and downstream partners, respectively. siRNA knockdown of CLK2-associated genes significantly increases conjoined gene formation. Collectively, our results reveal an unexpected role for CDC-like kinase in conjoined gene formation, via regulation of 3′-end processing and associated splicing factors.The phosphorylation of serine/arginine-rich proteins by CDC-like kinase is a central regulatory mechanism for RNA splicing reactions. Here, the authors synthesize a novel small molecule CLK inhibitor and map CLK-responsive alternative splicing events and discover an effect on conjoined gene transcription.

A novel solubilization technique for poorly soluble drugs through the integration of nanocrystal and cocrystal technologies.

The aim of the present study was to develop a novel solubilization technique consisting of a nano-cocrystal suspension by integrating cocrystal and nanocrystal formulation technologies to maximize solubilization over current solubilizing technologies. Monodisperse carbamazepine-saccharin, indomethacin-saccharin, and furosemide-caffeine nano-cocrystal suspensions, as well as a furosemide-cytosine nano-salt suspension, were successfully prepared with particle sizes of less than 300nm by wet milling with the stabilizers hydroxypropyl methylcellulose and sodium dodecyl sulfate. Interestingly, the properties of resultant nano-cocrystal suspensions were dramatically changed depending on the physicochemical and structural properties of the cocrystals. In the formulation optimization, the concentration and ratio of the stabilizers also influenced the zeta potentials and particles sizes of the resultant nano-cocrystal suspensions. Raman spectroscopic analysis revealed that the crystalline structures of the cocrystals were maintained in the nanosuspensions, and were physically stable for at least one month. Furthermore, their dissolution profiles were significantly improved over current solubilization-enabling technologies, nanocrystals, and cocrystals. In the present study, we demonstrated that nano-cocrystal formulations can be a new promising option for solubilization techniques to improve the absorption of poorly soluble drugs, and can expand the development potential of poorly soluble candidates in the pharmaceutical industry.

Characteristics of the Novel Potassium-Competitive Acid Blocker Vonoprazan Fumarate (TAK-438)

Proton pump inhibitors (PPIs) are widely prescribed as first-line therapy for the treatment of acid-related diseases, such as peptic ulcers and gastro-esophageal reflux disease, and for the eradication of Helicobacter pylori. However, the therapeutic efficacy of conventional PPIs is considered limited because: (1) they are unstable under acidic conditions and require an enteric-coated formulation in clinical use; (2) they show high interindividual variability in pharmacokinetics due to genetic polymorphisms of cytochrome P450 (CYP) 2C19 metabolism; (3) they have a relatively slow onset of pharmacological action and may require several doses to achieve optimal acid suppression and symptom relief; and (4) they often do not provide stable suppression of gastric acid secretion over 24xa0h. Vonoprazan fumarate (TAK-438, hereinafter referred to as “vonoprazan”) is a new potassium-competitive acid blocker (P-CAB) developed to resolve the above limitations of conventional PPIs. Various physicochemical data have shown that vonoprazan has a high solubility and stability over a broad pH range in aqueous conditions. In addition, vonoprazan has a more potent and longer-lasting acid suppression effect than the conventional PPI, lansoprazole. Preclinical pharmacokinetic studies have shown that vonoprazan is accumulated and retained in the stomach for more than 24xa0h, even after it is eliminated from the plasma. From these findings, we propose that vonoprazan, which possesses a novel mode of action, can improve on the outcomes seen with conventional PPI-based treatments for acid-related diseases.FundingThis review project, including the publication of this article, was funded by Takeda Pharmaceutical Company Limited.

Enhanced pulmonary absorption of poorly soluble itraconazole by micronized cocrystal dry powder formulations

&NA; Micronized cocrystal powders and amorphous spray‐dried formulations were prepared and evaluated in vivo and in vitro as pulmonary absorption enhancement formulations of poorly soluble itraconazole (ITZ). ITZ cocrystals with succinic acid (SA) or l‐tartaric acid (TA) with a particle size diameter of <2 &mgr;m were successfully micronized using the jet‐milling system. The cocrystal crystalline morphologies observed using scanning electron microscopy (SEM) suggested particle shapes that differed from those of the crystalline or spray‐dried amorphous ITZ. The micronized ITZ cocrystal powders showed better intrinsic dissolution rate (IDR) and pulmonary absorption profile in rats than that of the amorphous spray‐dried formulation and crystalline ITZ with comparable particle sizes. Specifically, in rat pharmacokinetic studies following pulmonary administration, micronized ITZ‐SA and ITZ‐TA cocrystals showed area under the curve from 0 to 8 h (AUC0–8h) values approximately 24‐ and 19‐fold higher than those of the crystalline ITZ and 2.0‐ and 1.6‐fold higher than the spray‐dried ITZ amorphous values, respectively. The amorphous formulation appeared physically instable during the studies due to rapid crystallization of ITZ, which was its disadvantage compared to the crystalline formulations. Therefore, this study demonstrated that micronized cocrystals are promising formulations for enhancing the pulmonary absorption of poorly soluble compounds. Graphical abstract Figure. No caption available.

Prediction of Human Pharmacokinetic Profile After Transdermal Drug Application Using Excised Human Skin

Although several mathematical models have been reported for the estimation of human plasma concentration profiles of drug substances after dermal application, the successful cases that can predict human pharmacokinetic profiles are limited. Therefore, the aim of this study is to investigate the prediction of human plasma concentrations after dermal application using inxa0vitro permeation parameters obtained from excised human skin. The inxa0vitro skin permeability of 7 marketed drug products was evaluated. The plasma concentration-time profiles of the drug substances in humans after their dermal application were simulated using compartment models and the clinical pharmacokinetic parameters. The transdermal process was simulated using the inxa0vitro skin permeation rate and lag time assuming a zero-order absorption. These simulated plasma concentration profiles were compared with the clinical data. The result revealed that the steady-state plasma concentration of diclofenac and the maximum concentrations of nicotine, bisoprolol, rivastigmine, and lidocaine after topical application were within 2-fold of the clinical data. Furthermore, the simulated concentration profiles of bisoprolol, nicotine, and rivastigmine reproduced the decrease in absorption due to drug depletion from the formulation. In conclusion, this simple compartment model using inxa0vitro human skin permeation parameters as zero-order absorption predicted the human plasma concentrations accurately.

Isotope-edited Infrared Spectroscopy for Efficient Discrimination between Pharmaceutical Salts and Cocrystals

Isotope-edited infrared spectroscopy using carboxylic acids selectively labeled with 13C is proposed herein for the efficient discrimination of pharmaceutical salts and cocrystals, whereby proton-transfer probe vibrations are highlighted by isotope shifts. This new technique can accurately discriminate even a confusing salt from a cocrystal for the traditional method, highlighting the diagnostic peaks. In addition, the established technique also provided the OH in-plane bending vibrations corresponding to intermolecular hydrogen bonding at the carbonyl oxygens of the cocrystals. The technique will accelerate the discrimination, which is a critical process in cocrystal development.

Combination of NMR Methods To Reveal the Interfacial Structure of a Pharmaceutical Nanocrystal and Nanococrystal in the Suspended State

The detailed structure of a pharmaceutical nanosuspension was investigated using three nuclear magnetic resonance (NMR) methods: solid-state, solution-state, and high resolution-magic angle spinning (HR-MAS) NMR. Carbamazepine (CBZ) and CBZ-saccharin (SAC) cocrystal nanosuspensions were prepared by wet-milling with hydroxypropyl methylcellulose (HPMC) and sodium dodecyl sulfate (SDS) as stabilizing agents. Solid-state 13C NMR indicated the presence of not only the crystalline drug substance but also solid-state HPMC, even though HPMC was used as an aqueous solution to prepare the nanosuspensions. Solution-state 1H NMR of the nanosuspensions with and without ultracentrifugation pretreatment indicated that a fraction of the CBZ, SAC, and SDS formed a solid or semisolid phase on the surface of the nanoparticles and was in equilibrium between the dissolved and undissolved states. 1H HR-MAS NMR was highly effective in detecting and quantifying the semisolid phase on the surface of the nanoparticles. From these comprehensive NMR studies, it was concluded that the nanosuspension was composed of crystalline drug core particles surrounded by a semisolid phase consisting of the drug and stabilizing agents. The semisolid phase on the nanoparticle surface was in equilibrium with the solution phase and contributed to the stabilization of the nanoparticle by steric hindrance and electrostatic repulsion.

Discrimination and quantification of sulfathiazole polytypes using low-frequency Raman spectroscopy

Sulfathiazole forms II, III and IV are polytypes where common monolayers accumulate in different stacking modes. These polytypes are difficult to identify using conventional analytical techniques when they concomitantly crystallize. However, the use of low-frequency Raman spectroscopy enables discrimination of these polytypes and can determine the ratio of forms III and IV, which are the most challenging pair for quantification. A Hydrogen/deuterium exchange study suggests that characteristic patterns below 100 cm−1 predominantly come from differences of superstructure geometries, especially layer stacking, rather than hydrogen-bond geometries. This study demonstrates that low-frequency Raman spectroscopy has advantages for both polytypic discrimination and quantification.

Utility of Göttingen minipigs for Prediction of Human Pharmacokinetic Profiles After Dermal Drug Application

PurposeAlthough Göttingen minipigs have been widely used for the evaluation of skin absorption, the correlation of minipig skin permeability with human skin absorption remains unclear. This study was designed to investigate the prediction of human plasma concentrations after dermal application of drug products using skin permeability data obtained from minipigs.MethodsFirst, in vitro skin permeabilities of seven marketed transdermal drug products were evaluated in minipigs, and compared with in vitro human skin permeability data. Next, plasma concentration-time profiles in humans after dermal applications were simulated using the in vitro minipig skin permeability data. Finally, the in vitro-in vivo correlation of minipig skin permeability was assessed.ResultsThe in vitro skin permeabilities in minipigs were correlated strongly with in vitro human skin permeability data for the same drug products, indicating the utility of minipig skin as an alternative to human skin for in vitro studies. The steady-state plasma concentration or the maximum concentration of drugs was within 2-fold of the clinical data. Bioavailability was approximately 3-fold lower than in vitro permeated fraction.ConclusionsPredictions using in vitro skin permeability data in Göttingen minipig skin can reproduce the human pharmacokinetic profile, although the prediction of in vivo skin absorption underestimates human absorption.