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The effects of pH changes and saccharin (SAC) addition on the nanostructure and mobility of the cationic aminoalkyl methacrylate copolymer Eudragit E PO (EUD-E) and its drug solubilization ability were investigated. Small-angle X-ray scattering performed using synchrotron radiation and atomic force microscopy showed that the EUD-E nanostructure, which has a size of approximately several nanometers, changed from a random coil structure at low pH (pH 4.0-5.0) to a partially folded structure at high pH (pH 5.5-6.5). The EUD-E also formed a partially folded structure in a wide pH range of 4.5-6.5 when SAC was present, and the coil-to-globule transition was moderate with pH increase, compared with that when SAC was absent. The equilibrium solubility of the neutral drug naringenin (NAR) was enhanced in the EUD-E solution and further increased as the pH increased. The enlargement of the hydrophobic region of EUD-E in association with the coil-to-globule transition led to efficient solubilization of NAR. The interaction with SAC enhanced the mobility of the EUD-E chains in the hydrophobic region of EUD-E, resulting in changes in the drug-solubilizing ability. 1H high-resolution magic-angle spinning NMR measurements revealed that the solubilized NAR in the partially folded structure of EUD-E showed higher molecular mobility in the presence of SAC than in the absence of SAC. This study highlighted that solution pH and the presence of SAC significantly changed the drug solubilization ability of EUD-E, followed by changes in the EUD-E nanostructure, including its hydrophobic region.

Recently, choline and geranic acid (CAGE), an ionic liquid (IL), has been recognized to be a superior biocompatible material for oral and transdermal drug delivery systems (DDS). When CAGE is administered, CAGE would be exposed to various types of physiological fluids, such as intestinal and intradermal fluids. However, the effect of physiological fluids on the structure of CAGE remains unclear. In the present study, molecular structures of CAGE with different ratios of water were investigated using small-angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR). The SAXS pattern of CAGE showed an IL-specific broad peak derived from nanoscale aggregation until 17 vol % water. Meanwhile, narrow peaks were observed in samples with 25-50 vol % water, showing a transition to the lamellar phase. With more than 67 vol % water, CAGE was found to exist as micelles in water. The 1H NMR spectra indicated that protons of H2O, OH in choline (CH), and COOH in geranic acid (GA) were observed as only one peak up to 17 vol % water. This peak shifted to a high magnetic field, and the integral values increased with the water content, speculating that water is localized close to the COOH and OH groups to allow proton exchange. The 13C NMR spectra showed that peaks related to the carboxyl group shifted with adding water. Moreover, only GA peaks were observed in the lamellar phase through 13C cross-polarization magic-angle spinning NMR, suggesting that the main rigid component of the lamellar phase was GA. Taken together, this study suggested that CAGE still maintained its IL structure up to 17 vol % water, then transitioned to the lamellar phase with 25-50 vol % water, and finally changed to the micellar phase with more than 67 vol % water. This information would be useful in the formulation and development of DDS using CAGE.

The present study evaluated the specific intermolecular interactions between carbamazepine (CBZ) and substituents of hypromellose acetate succinate (HPMC-AS), as well as the mechanism of inhibition of recrystallization of solid dispersions (SDs) using Fourier-transform infrared (FTIR) and solid-state nuclear magnetic resonance (NMR) spectroscopy. CBZ and HPMC derivatives, including HPMC, hypromellose acetate (HPMC-A), and hypromellose succinate (HPMC-S), were spray-dried to prepare CBZ/polymer spray-dried samples (SPDs). CBZ/HPMC SPD and CBZ/HPMC-A SPD recrystallized within 10 days at 60 °C and 0% relative humidity, whereas CBZ/HPMC-S SPD maintained its amorphous state for a longer period. FTIR and solid-state NMR measurements using 13C cross polarization (CP), 1H single-pulse, and 1H-15N CP-based heteronuclear single quantum correlation filter experiment with very fast magic angle spinning (MAS) at 70 kHz identified molecular interactions in CBZ/polymer SPDs. Although the HPMC backbone and substituents did not interact notably with CBZ and disrupt CBZ-CBZ intermolecular interactions (formed in the amorphous CBZ), acetate and succinate substituents on HPMC-A and HPMC-S disrupted CBZ-CBZ intermolecular interactions through formation of CBZ/polymer interactions. The acetate substituent formed a hydrogen bond with the NH2 group of CBZ, whereas the succinate substituent formed molecular interactions with both the C═O and NH2 groups of CBZ. Formation of relatively strong molecular interactions between CBZ and the succinate substituent followed by disruption of CBZ-CBZ intermolecular interactions effectively stabilized the amorphous state of CBZ in CBZ/HPMC-S SPD. The correlation between CBZ-polymer interactions and ability of polymers to effectively inhibit CBZ recrystallization is reflected in various commercial HPMC-AS. For example, HPMC-AS LF grade, containing higher amounts of the succinate group, was found to effectively inhibit the recrystallization of CBZ through strong molecular interactions as compared with the HPMC-AS HF grade. The present study demonstrated that a detailed investigation of molecular interactions between the drug and the polymer using FTIR and solid-state NMR spectroscopy could contribute to a suitable selection of the SD carrier.

Starting from our previous eIF4A3-selective inhibitor 1a, a novel series of (piperazine-1-carbonyl)pyridin-2(1H)-one derivatives was designed, synthesized, and evaluated for identification of orally bioavailable probe molecules. Compounds 1o and 1q showed improved physicochemical and ADMET profiles, while maintaining potent and subtype-selective eIF4A3 inhibitory potency. In accord with their promising PK profiles and results from initial in vivo PD studies, compounds 1o and 1q showed antitumor efficacy with T/C values of 54% and 29%, respectively, without severe body weight loss. Thus, our novel series of compounds represents promising probe molecules for the in vivo pharmacological study of selective eIF4A3 inhibition.

Eukaryotic initiation factor 4A3 (eIF4A3) is a member of the ATP-dependent RNA helicase protein family and controls RNA metabolism, including nonsense-mediated mRNA decay (NMD) and RNA localization, as a core component of the exon junction complex (EJC). Cancer cells often harbor a wide variety of mutations introducing PTCs, and cancer cells are thought to be highly dependent on the NMD pathway to avoid the accumulation of aberrant proteins. Therefore, targeting eIF4A3 inhibition could potentially represent a promising approach for anticancer therapy, however, the detailed physiological functions of eIF4A3 are not clear. To enable the further biological and pharmacological evaluation of eIF4A3, we recently discovered several classes of both ATP-competitive and allosteric eIF4A3 inhibitors which showed potent and selective eIF4A3 inhibition. Among these, the allosteric eIF4A3 inhibitors exhibited significant NMD inhibition in a cellular reporter assay along with eIF4A3 inhibitory potency and were examined for understanding the function of eIF4A3 in RNA homeostasis. Although the allosteric inhibitors showed potent enzymatic activity as well as cellular potency, the physicochemical properties such as solubility, metabolic stability, and pharmacokinetics were insufficient for conducting further biological and pharmacological studies. To identify improved probe molecules for the study of eIF4A3 function, we continued our chemistry efforts on allosteric inhibitors using the novel 3-(4-chlorophenyl)-1,4-diacylpiperazine derivative as a lead compound. Although many of them showed improved solubility and metabolic stability while maintaining eIF4A3 inhibitory potency, further testing indicated it to be a P-gp substrate. To address this issue, a pyridin-2(1H)-one derivative was prepared based on the calculated tPSA value for reducing polarity, which led us to the discovery of the novel class of orally bioavailable eIF4A3-selective inhibitors. Herein, we demonstrated their biological and pharmacological evaluations and showed anti-tumor efficacy without severe body weight loss in xenograft mice. Thus, our novel series of compounds represent promising tool compounds for the in vivo pharmacological study of selective eIF4A3 inhibition. Citation Format: Ryo Mizojiri, Daisuke Nakata, Yoshihiko Satoh, Daisuke Morishita, Sachio Shibata, Misa Iwatani-Yoshihara, Yohei Kosugi, Mai Kosaka, Junpei Takeda, Shigekazu Sasaki, Kazuaki Takami, Koichiro Fukuda, Masahiro Kamaura, Shinobu Sasaki, Ryosuke Arai, Douglas R. Cary, Yasuhiro Imaeda. Design, synthesis and evaluations of novel class of orally bioavailable eIF4A3-selective inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2793.