The discovery of water-soluble indazole derivatives as potent microtubule polymerization inhibitors

Taking a previously discovered indazole derivative 1 as a lead, systematic structural modifications were performed with an indazole core at the 1- and 6-positions to improve its aqueous solubility. Among the designed indazole derivatives, 6-methylpyridin-3-yl indazole derivative 8l and 1H-indol-4-yl indazole derivative 8m exhibited high potency in the low nanomolar range against A549, Huh-7, and T24 cancer cells, including Taxol-resistant variant cells (A549/Tax). As a hydrochloride salt, 8l exhibited much improved aqueous solubility, and its log P value fell into a favorable range. In mechanistic studies, 8l impeded tubulin polymerization through interacting with the colchicine site, resulting in cell cycle arrest and cellular apoptosis. In addition, compared to lead compound 1, 8l reduced cell migration and led to more potent inhibition of tumor growth in vivo without apparent toxicity. In summary, indazole derivative 8l could work as a potential anticancer agent and deserves further investigation for cancer therapy.

Prediction of organic compound aqueous solubility using machine learning: a comparison study of descriptor-based and fingerprints-based models

A reliable and practical determination of a chemical species' solubility in water continues to be examined using empirical observations and exhaustive experimental studies alone. Predictions of chemical solubility in water using data-driven algorithms can allow us to create a rationally designed, efficient, and cost-effective tool for next-generation materials and chemical formulations. We present results from two machine learning (ML) modeling studies to adequately predict various species' solubility using data for over 8400 compounds. Molecular-descriptors, the most used method in previous studies, and Morgan fingerprint, a circular-based hash of the molecules' structures, were applied to produce water solubility estimates. We trained all models on 80% of the total datasets using the Random Forest (RFs) technique as the regressor and tested the prediction performance using the remaining 20%, resulting in coefficient of determination (R2) test values of 0.88 and 0.81 and root-mean-square deviation (RMSE) test values 0.64 and 0.80 for the descriptors and circular fingerprint methods, respectively. We interpreted the produced ML models and reported the most effective features for aqueous solubility measures using the Shapley Additive exPlanations (SHAP) and thermodynamic analysis. Low error, ability to investigate the molecular-level interactions, and compatibility with thermodynamic quantities made the fingerprint method a distinct model compared to other available computational tools. However, it is worth emphasizing that physicochemical descriptor model outperformed the fingerprint model in achieving better predictive accuracy for the given test set.

Comparative study of encapsulated cannabidiol ternary solid dispersions prepared by different techniques: The application of a novel technique jet milling

Jet milling is a common technique in ultrafine powder preparation field. It has never been used to design delivery systems. Cannabidiol (CBD) is an important cannabinoid of hemp but poor aqueous solubility limited its applications. In this study, solid dispersion (SD) technique was combined with cyclodextrin complexation technique, and jet milling was used for the first time to prepare SDs for improving CBD solubility. Different characterizations demonstrated that the dispersion effect and complexation structure of CBD SD3 prepared by jet milling were comparable to that of CBD SD2 prepared by spray drying (a common solution-based method), and were better than that of CBD SD1 prepared by cogrinding. The water solubility of CBD was increased to 20.902 μg/mL (909-fold) in CBD SD3. Besides, the antioxidant activity and cytotoxicity to tumor cells of CBD were enhanced by dispersion. This work indicated that jet milling, as a new technique with low cost and excellent applicability, could be further developed for the delivery of food functional factors or bioactive molecules.

A method for improving the properties of famotidine

According to crystal engineering, the pharmaceutical intermediate m-nitrobenzoic acid (MNBA), which contains a carboxylic acid group, was selected as a coformer (CCF) for drug cocrystallization with famotidine (FMT), and a new stable FMT salt cocrystal was synthesized. The salt cocrystals were characterized by scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, infrared spectroscopy, powder X-ray diffraction and X-ray single crystal diffraction. A single crystal structure of FMT-MNBA (1:1) was successfully obtained, and then the solubility and permeability of the newly synthesized salt cocrystal were studied. The results showed that, compared with free FMT, the FMT from the FMT-MNBA cocrystal showed improved permeability. This study provides a synthetic method to improve the permeability of BCS III drugs, which will contribute to the development of low-permeability drugs.

Promising strategies for improving oral bioavailability of poor water-soluble drugs

INTRODUCTION

Oral administration of poorly water-soluble drugs (PWSDs) is generally related to low bioavailability, leading to high drug doses, multiple side effects, and low patient compliance. Thus, different strategies have been developed to increase drug solubility and dissolution in the gastrointestinal tract, opening new venues for these drugs.

AREAS COVERED

This review outlines the current challenges in PWSD formulation development and the strategies to overcome the oral barriers and increase their solubility and bioavailability. Conventional strategies include altering crystalline and molecular structures and modifying oral solid dosage forms. In contrast, novel strategies comprise micro- and nanostructured systems. Recent representative studies involving how these strategies have improved the oral bioavailability of PWSDs were also reviewed and reported.

EXPERT OPINION

New approaches to enhance PWSD bioavailability have sought to improve water solubility and dissolution rates, drug protection by overcoming biological barriers, and increased absorption. Still, only a handful of studies have focused on quantifying the increase in bioavailability. Improving the oral bioavailability of PWSDs remains an exciting unexplored field of research and has become an important issue for successfully developing pharmaceutical products.

Design of mirtazapine solid dispersion with different carriers' systems: optimization, in vitro evaluation, and bioavailability assessment

The solid dispersion technique is the most effective and widely used approach for increasing the solubility and release of drugs that have low water solubility. Mirtazapine (MRT) is an atypical antidepressant used to treat severe depression. MRT has a low oral bioavailability (about 50%) due to its low water solubility (BCS class II). The study's goal was to determine optimum conditions for incorporating MRT into various polymer types utilizing the solid dispersion (SD) technique, with the goal of selecting the most suitable formula with the optimal aqueous solubility, loading efficiency, and dissolution rate. The D-optimal design was used to pick the optimal response. The optimum formula was subjected to physicochemical evaluation by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM). In vivo bioavailability study was conducted on white rabbits' plasma samples. MRT-SDs were prepared by the solvent evaporation method using Eudragit (RL-100, RS-100, E-100, L-100-55), PVP K-30, and PEG 4000 with different drug/polymer percentages (33.33%, 49.99%, and 66.66%). Results showed that the optimum formula obtained using PVP K-30 at a drug percentage of 33.33% gave a loading efficiency of 100.93%, an aqueous solubility of 0.145 mg/ml, and a dissolution rate of 98.12% after 30 min. These findings demonstrated promising enhancement of MRT properties and increasing its oral bioavailability by 1.34-fold more than plain drug.

Design, synthesis and biological evaluations of quinolone amides against African trypanosomiasis with improved solubility

The human African trypanosomiasis is a devastating parasitic infection, which is caused by the protozoan Trypanosoma brucei and transmitted by the bite of the tsetse fly. An untreated infection usually results in death and only few drugs with significant drawbacks are currently available for treatment. Previous investigations revealed the quinolone amide MB007 as a lead compound with an excellent selectivity for T. b. brucei. Here, new quinolone amides were synthesized for deeper insights into the structure-activity relationship. Furthermore, the aqueous solubility of the compounds was analyzed, as the poor solubility of previous quinolone amides impeded in vivo studies for target identification. The biological evaluation led to the new lead structure 9f, which exhibits a promising in vitro activity against T. b. brucei (IC50 = 22 nM) and showed no cytotoxicity against macrophages. Moreover, compounds 10b and 10c were discovered, which possessed an improved solubility combined with a decent selectivity.

Multiple machine learning algorithms assisted QSPR models for aqueous solubility: Comprehensive assessment with CRITIC-TOPSIS

As an essential environmental property, the aqueous solubility quantifies the hydrophobicity of a compound. It could be further utilized to evaluate the ecological risk and toxicity of organic pollutants. Concerned about the proliferation of organic contaminants in water and the associated technical burden, researchers have developed QSPR models to predict aqueous solubility. However, there are no standard procedures or best practices on how to comprehensively evaluate models. Hence, the CRITIC-TOPSIS comprehensive assessment method was first-ever proposed according to a variety of statistical parameters in the environmental model research field. 39 models based on 13 ML algorithms (belonged to 4 tribes) and 3 descriptor screening methods, were developed to calculate aqueous solubility values (log K_ws) for organic chemicals reliably and verify the effectiveness of the comprehensive assessment method. The evaluations were carried out for exhibiting better predictive accuracy and external competitiveness of the MLR-1, XGB-1, DNN-1, and kNN-1 models in contrast to other prediction models in each tribe. Further, XGB model based on SRM (XGB-1, C = 0.599) was selected as an optimal pathway for prediction of aqueous solubility. We hope that the proposed comprehensive evaluation approach could act as a promising tool for selecting the optimum environmental property prediction methods.

Multi-channel GCN ensembled machine learning model for molecular aqueous solubility prediction on a clean dataset

This study constructed a new aqueous solubility dataset and a solubility regression model which was ensembled by GCN and machine learning models. Aqueous solubility is a key physiochemical property of small molecules in drug discovery. In the past few decades, there have been many studies about solubility prediction. However, many of these studies have high root mean squared error (RMSE). Meanwhile, their dataset always contains salt compounds and solubility data obtained from different experimental conditions. In this paper, we constructed a clean dataset with 2609 compounds, which was small but contains only solubility records without salts at the same temperatures (25 °C). Here, we applied graph convolutional neural network (GCN) to construct an aqueous solubility prediction model. To enhance the performance of the model, the molecular MACCS key fingerprints and physiochemical descriptors were also combined with the GCN model to build a multi-channel model. Additionally, the authors also built two machine learning models (support vector regression and gradient boost decision tree) and assembled them to the GCN model to improve the root mean squared error (RMSE = 0.665). Finally, comparative experiments have shown that our framework achieved the best performance on ESOL dataset (RMSE_val = 0.56, RMSE_test = 0.44) and surpassed four established software on aqueous solubility prediction of new compounds.

Soluplus® polymeric nanomicelles improve solubility of BCS-class II drugs

The issue of poor aqueous solubility is often a great hitch in the development of liquid dosage forms for those drugs that the Biopharmaceutics Classification System (BCS) includes in classes II and IV. Among the possible technological solutions, inclusion of the drug molecule within polymeric micelles, and particularly nanomicelles, has been proposed in the last years as a valid strategy. Our attention has been recently attracted by Soluplus^®, an amphiphilic polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer able to form small and stable nanomicelles. The aim of this study was to characterize Soluplus^® nanomicelles to enhance the apparent solubility of three model APIs, categorized in BCS class II: ibuprofen (IBU), idebenone (IDE), and miconazole (MIC). Drug-loaded Soluplus^® micelles with a mean size around 60–70 nm were prepared by two methods (direct dissolution or film hydration method). The prepared nanosystems were characterized in terms of mean particle size and Zeta potential, physical stability, drug solubility, and in vitro drug release. The solubility of the tested APIs was shown to increase linearly with the concentration of graft copolymer. Soluplus^® can be easily submitted to membrane filtration (0.2 µm PES or PTFE membranes), showing the potential to be sterilized by this method. Freeze-drying enabled to obtain powder materials that, upon reconstitution with water, maintained the initial micelle size. Finally, viscosity studies indicated that these nanomicelles have potential applications where a bioadhesive material is advantageous, such as in topical ocular administration.

Salts of 2-hydroxybenzylamine with improvements on solubility and stability: Virtual and experimental screening

2-Hydroxybenzylamine (2-HOBA) is a drug used to effectively treat oxidative stress. To improve its aqueous solubility and thermal stability, salt screening and synthesis was carried out. The conductor-like screening model for the real solvents model (COSMO-RS) was applied to virtual screening of coformers among 200 commonly used candidates for salification of 2-HOBA. As a result, 40 hit compounds were subjected to experimental liquid-assisted grinding (LAG) with 2-HOBA, then 21 systems were characterized as new solid phases by PXRD. Nine multicomponent single crystals of 2-HOBA with succinic acid, p-aminobenzoic acid, p-nitrobenzoic acid, o-nitrobenzoic acid, p-toluic acid, 2,3-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, p-nitrophenol, and 5-hydroxyisophthalic acid were obtained and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. All of them were salts and exhibited higher decomposition temperatures compared with pure 2-HOBA. The apparent aqueous solubility of three new salts, i.e., those with succinic acid, p-aminobenzoic acid, and p-nitrophenol were higher than the equilibrium solubility of 2-HOBA. The accelerated stability test indicated that all salts show excellent stability under conditions (40 °C and 75% RH) for 4 weeks. Overall, this work introduced a protocol that combined the virtual screening tool based on the COSMO-RS model and the experimental LAG method to screen new salts for a target compound. The feasibility of this protocol was confirmed in the case of 2-HOBA whose new salts were successfully obtained and represented an improvement for aqueous solubility and thermal stability.

Ability of mathematical models to predict human in vivo percutaneous penetration of steroids

Human skin is a common route for topical steroids to enter the body. To aid with risk management of therapeutic steroid usage, the US Environmental Protection Agency estimates percutaneous penetration using mathematical models. However, it is unclear how accurate are mathematical models in estimating percutaneous penetration/absorption of steroids. In this study, accuracy of predicted flux (penetration/absorption) by the main mathematical model used by the EPA, the Potts and Guy model based on in vitro data is compared to actual human in vivo data from our laboratory of percutaneous absorption of topical steroids. We focused on steroids due to the availability of steroid in vivo human data in our laboratory. For most steroids the flux was underestimated by a factor 10-60. However, within the group itself, there was an association between the Potts and Guy model and experimental human in vivo data (Pearson Correlation = 0.8925, p = 0.000041). Additionally, some physiochemical parameters used in the Potts and Guy equation, namely log Kp (Pearson Correlation = 0.7307, p = 0.0046) and molecular weight (Pearson correlation = -0.6807, p = 0.0105) correlated significantly with in vivo flux. Current mathematical models used in estimating percutaneous penetration/absorption did not accurately predict in vivo flux of steroids. Why? Proposed limitations to mathematical models currently used include: not accounting for volatility, lipid solubility, hydrogen bond effects, drug metabolism, as well as protein binding. Further research is needed in order to increase the predictive nature of such models for in vivo flux.

Characterization of tea tree oil nanoemulsion and its acute and subchronic toxicity

Tea tree oil (TTO) is a popular topical use to treat skin infections. However, its poor aqueous solubility and stability have substantially limited its widespread application, including oral administration that might be therapeutic for enteric infections. In this study, mechanical ultrasonic methods were used to prepare TTO nanoemulsion (nanoTTO) with a mean droplet diameter of 161.80 nm ± 3.97, polydispersity index of 0.21 ± 0.01, and zeta potential of -12.33 ± 0.72 mV. The potential toxicity of nanoTTO was assessed by studying the oral median lethal dose (LD50) and repeated 28-day oral toxicity to provide a reference for in vivo application. Results showed that nanoTTO had no phase separation under a centrifugation test and displayed good stability during storage at -20, 4 and 25 °C over 60 days. Repeated-dose 28-day oral toxicity evaluation revealed no significant effects on growth and behavior. Assessments of hematology, clinical biochemistry, and histopathology indicated no obvious adverse effects in mice at 50, 100 and 200 mg/mL. These data suggest that nanoTTO can be considered a potential antimicrobial agent by oral administration due to its inhibitory effect on bacteria and relatively lower toxicity.

Predicting aqueous solubility by QSPR modeling

The aqueous solubility is predicted here using quantitative structure property relationship (QSPR) models. In this study, we examine whether descriptors that individually yield favorable models for the prediction of the Gibbs energy of solvation and sublimation can be used in combination with octanol-water partition coefficient to produce QSPR models for the prediction of aqueous solubility. Based on this strategy, applied to seven distinct datasets, all models exhibited an R² greater than 0.7 and Q² greater than 0.6 for the estimation of aqueous solubility. We also determined how uncoupling the descriptors used to create QSPR models in the prediction of Gibbs energy of sublimation yielded an improved model. Model refinement using an artificial neural network applying the same descriptors generated significantly better models with improved R² and standard deviation.

Assessing toxicity of hydrophobic aliphatic and monoaromatic hydrocarbons at the solubility limit using novel dosing methods

Reliable delineation of aquatic toxicity cut-offs for poorly soluble hydrocarbons is lacking. In this study, vapor and passive dosing methods were applied in limit tests with algae and daphnids to evaluate the presence or absence of chronic effects at exposures corresponding to the water solubility for representative hydrocarbons from five structural classes: branched alkanes, mono, di, and polynaphthenic (cyclic) alkanes and monoaromatic naphthenic hydrocarbons (MANHs). Algal growth rate and daphnid immobilization, growth and reproduction served as the chronic endpoints investigated. Results indicated that the dosing methods applied were effective for maintaining mean measured exposure concentrations within a factor of two or higher of the measured water solubility of the substances investigated. Chronic effects were not observed for hydrocarbons with an aqueous solubility below approximately 5 μg/L. This solubility cut-off corresponds to structures consisting of 13-14 carbons for branched and cyclic alkanes and 16-18 carbons for MANHs. These data support reliable hazard and risk evaluation of hydrocarbon classes that comprise petroleum substances and the methods described have broad applicability for establishing empirical solubility cut-offs for other classes of hydrophobic substances. Future work is needed to understand the role of biotransformation on the observed presence or absence of toxicity in chronic tests.

Design, Synthesis and Structure-Activity Relationship Studies of Glycosylated Derivatives of Marine Natural Product Lamellarin D

Lamellarin D, a marine natural product, acts as a potent inhibitor of DNA topoisomerase I (Topo I). To modify its physicochemical property and biological activity, a series of mono- and di-glycosylated derivatives were designed and synthesized through 22-26 multi-steps. Their inhibition of human Topo I was evaluated, and most of the glycosylated derivatives exhibited high potency in inhibiting Topo I activity as well as lamellarin D. All the 15 target compounds were evaluated for their cytotoxic activities against five human cancer cell lines. The typical lamellarin derivative ZL-3 exhibited the best activity with IC₅₀ values of 3 nM, 10 nM, and 15 nM against human lung cancer A549 cells, human colon cancer HCT116 cells and human hepatocellular carcinoma HepG2 cells. Compound ZL-1 exhibited anti-cancer activity with IC₅₀ of 14 nM and 24 nM against human colon cancer HCT116 cells and human hepatocellular carcinoma HepG2 cells, respectively. Cell cycle analysis in MDA-MB-231 suggested ZL-3 inhibited cell growth through arresting cells at the G2/M phase of the cell cycle. Further tests showed a significant improvement in aqueous solubility of ZL-1 and ZL-7. This study suggested that glycosylation could be utilized as a useful strategy to optimize lamellarin D derivatives as Topo I inhibitors and anticancer agents.

Design, synthesis, and biological evaluation of hederagenin derivatives with improved aqueous solubility and tumor resistance reversal activity

Multidrug resistance (MDR) has become a major obstacle to malignancies treatment by chemotherapeutic drugs, therefore, it is important to develop MDR reversal agents with high activity. We have previously found that the hederagenin (HD) derivative HBQ showed good tumor MDR reversal activity in vitro and in vivo but had poor solubility. In this study, to enhance the aqueous solubility and tumor MDR reversal activity of HBQ, three series of HD derivatives were designed and synthesized. Nitrogen-containing heterocyclic-substituted, PEGylated, and ring-A substituted derivatives significantly reversed the MDR phenotype of KBV (multidrug-resistant oral epidermoid carcinoma) cells toward paclitaxel at a concentration of 10 μM in MTT assays. The PEGylated derivatives 10c-10e had increased aqueous solubility compared with HBQ by 18-657 fold, while maintaining tumor MDR reversal activity. The most in vitro active compound 10c possessed good chemical stability to an esterase over 24 h and enhanced the sensitivity of KBV cells to paclitaxel and vincristine with IC₅₀ values of 4.58 and 0.79 nM, respectively. Mechanism studies indicated that compound 10c increased the accumulation of P-glycoprotein (P-gp) substrates rhodamine 123 and Flutax1 in KBV cells and MCF-7T (paclitaxel-resistant breast carcinoma) cells, that is to say, compound 10c exerted the reversal effect of tumor MDR by inhibiting the efflux function of P-gp. Finally, the structure-activity relationships were further investigated by analyzing the relationship between structure and tumor MDR reversal activity of HD derivatives. This study highlights the potential of PEGylated HD derivatives such as compound 10c for the development of tumor MDR reversal agents and provides information for the further improvement of the aqueous solubility and tumor MDR reversal activity of HD derivatives in the future.

Novel Phenylmethylenecyclohexenone Derivatives as Potent TrxR Inhibitors Display High Antiproliferative Activity and Induce ROS, Apoptosis, and DNA Damage

The natural product piperlonguminine (PL) has been shown to exert potential anticancer activity against several types of cancer via elevation of reactive oxidative species (ROS). However, the application of PL has been limited due to its poor water solubility and moderate activity. To improve PL's potency, we designed and synthesized a series of 17 novel phenylmethylenecyclohexenone derivatives and evaluated their pharmacological properties. Most of them exerted antiproliferative activities against four cancer cell lines with IC₅₀ values lower than PL. Among these, compound 10 e not only showed good water solubility and exerted the most potent antiproliferative activity against HGC27 cells (IC₅₀ =0.76 μM), which was 10-fold lower than PL (IC₅₀ =7.53 μM), but also exhibited lower cytotoxicity in human normal gastric epithelial cells GES-1 compared with HGC27 cells. Mechanistically, compound 10 e inhibited thioredoxin reductase (TrxR) activity, increased ROS levels, and diminished mitochondrial transmembrane potential (MTP) in HGC27 cells. Furthermore, 10 e also induced G₂ /M cell-cycle arrest, and triggered cancer cell apoptosis through the regulation of apoptotic proteins. Finally, 10 e promoted DNA damage in HGC27 cells via the activation of the H2AX(S139ph) and p53 signaling. In conclusion, 10 e, with prominent tumor selectivity and water solubility, could be a promising candidate for the treatment of cancer and, as such, warrants further investigation.

A sensitive "Switch-on" phosphorescent probe for ferrous iron quantification in drug and In vitro imaging of living cells

Iron plays an important role in various physiological processes. However, the detailed biological functions of iron have not been sufficiently explored because of a lack of effective methods to monitoring iron, especially the labile ferrous ion (Fe²⁺). In the current study, a novel turn-on phosphorescent probe for Fe²⁺ quantification and visualization has been proposed based on the hybrid nanocomposite of manganese dioxide and gemini iridium complex (MnO₂-GM-Ir). The surfactant-like GM-Ir with positive charges was beneficial to combine with the negatively charged manganese dioxide (MnO₂) nanosheets, and thus endowing the MnO₂-GM-Ir nanocomposite excellent dispersion ability in the water as well as efficiently avoiding the interference to the detection caused by the agglomeration of nanocomposite. Phosphorescence of GM-Ir was effectively quenched by MnO₂ nanosheets through fluorescence resonance energy transfer (FRET) and the inner filter effect (IFE), while the phosphorescence could be significantly recovered in the presence of Fe²⁺via a selective Fe²⁺-mediated reduction of MnO₂ nanosheets, indicating a highly-specific selectivity towards Fe²⁺ with a low detection limit (80 nM). The drug test assay and in vitro imaging studies further proved that the MnO₂-GM-Ir nanocomposite could be employed as a promising probe for the quantitative detection of exogenous Fe²⁺ in drug and in vitro imaging of living cells.

Encapsulation of finasteride with native and modified γ-cyclodextrins. Extensive characterization of the complexes

The aim of this work was to study the complexation process of FIN with native and modified CDs, to develop an aqueous solution for the topical treatment of male androgenic alopecia. The effect of pH and temperature in the complexation process were studied by solubility studies. The complexes FIN-CDs were characterized by ¹HNMR and 2-D NMR (ROESY) spectroscopy. Molecular modeling studies and NMR data were used to build three-dimensional models of the complexes. FTIR, DSC and SEM techniques were also applied to strengthen physicochemical characterization, geometry as well as structural aspects evidencing the effective inclusion of FIN into the CDs' hydrophobic cavity. The most effective CDs in the FIN complexation were γ-CDs, and their modified HP-γ- and methyl-γ-CDs by forming 1:1 complexes. The Kc value obtained for γ-CDs was 9687 ± 51 M^-1, whereas the Kc values obtained for HP-γ- and methyl-γ-CDs were lower, indicating that the presence of HP or methyl groups hinder the entry of FIN in the hydrophobic cavity of γ-CDs. In conclusion, FIN aqueous solubility could be increased by complexation with CDs and the aqueous solutions obtained can be used to improve FIN therapeutic possibilities in a pleasant preparation for the patient that guarantees the adherence to the treatment.

Data on metabolic stability, aqueous solubility and CYP inhibition of novel triazole-based nicotinamide phosphoribosyltransferase (NAMPT) inhibitors

In the related research article, entitled “Identification of novel triazole-based nicotinamide phosphoribosyltransferase (NAMPT) inhibitors endowed with antiproliferative and antiinflammatory activity” [1], we reported the in vitro hepatic metabolism data for compounds 30c, 48b, and 31b (here named as E5, A6, and T1), in comparison with the reference compounds GPP78 and FK866 [1–3]. In this article, we retrieved the available data about the hepatic microsomal stability and metabolites structural characterization of the entire library of triazole-based NAMPT inhibitors, also implementing the given information with data regarding aqueous solubility and CYP inhibition. Compounds are divided in subclasses based on the hydrolytic resistant groups replacing the amide function of GPP78 [1, 2].

Design, synthesis, and evaluations of the antiproliferative activity and aqueous solubility of novel carbazole sulfonamide derivatives as antitumor agents

Optimization of IG-105 (1) on the carbazole ring provided five series of new carbazole sulfonamides derivatives, 7a-e, 8a-g, 9a-g, 10a-e, and 11a-g. All of the compounds were evaluated against HepG2, MCF-7, MIA PaCa-2, and Bel-7402 cells for antiproliferative activity. Each series of compounds was 2-5 times more active against HepG2 cells (IC₅₀: 1.00-10.0 μM) than the other three tumor cell lines. Several representative compounds, selected from each series, showed aqueous solubility (13.4-176.5 µg/mL at pH 7.4 and 2.0) better than 1, with the aqueous solubility of corresponding salts > 30 mg/mL. From the results of evaluating the effects of the compounds 7b, 8c, 9c, 10c and 11c on tubulin in vitro, we speculated that their targets were different from those of 1 and CA-4P. We tested the antitumor activity of the representative compound 7b·HCl (10 mg/kg) in an in vivo study and found that its tumor growth inhibition rate was 41.1%. The tumor growth inhibition rate of 7b·HCl (20 mg/kg) was 54.6%, whereas the tumor growth inhibition rate of CA-4P (50 mg/kg) was 48.3%. And in another batch of in vivo antitumor activity testing, 9c·HCl and 11c·HCl at doses of 10 mg/kg resulted in 61.1% and 50.0% inhibition, respectively. These promising results warrant further development of the derivatives, which may use a novel mechanism and show potential potency as antitumor drug candidates.

A self-attention based message passing neural network for predicting molecular lipophilicity and aqueous solubility

Efficient and accurate prediction of molecular properties, such as lipophilicity and solubility, is highly desirable for rational compound design in chemical and pharmaceutical industries. To this end, we build and apply a graph-neural-network framework called self-attention-based message-passing neural network (SAMPN) to study the relationship between chemical properties and structures in an interpretable way. The main advantages of SAMPN are that it directly uses chemical graphs and breaks the black-box mold of many machine/deep learning methods. Specifically, its attention mechanism indicates the degree to which each atom of the molecule contributes to the property of interest, and these results are easily visualized. Further, SAMPN outperforms random forests and the deep learning framework MPN from Deepchem. In addition, another formulation of SAMPN (Multi-SAMPN) can simultaneously predict multiple chemical properties with higher accuracy and efficiency than other models that predict one specific chemical property. Moreover, SAMPN can generate chemically visible and interpretable results, which can help researchers discover new pharmaceuticals and materials. The source code of the SAMPN prediction pipeline is freely available at Github (https://github.com/tbwxmu/SAMPN).

Development of a potent and orally active activator of adenosine monophosphate-activated protein kinase (AMPK), ASP4132, as a clinical candidate for the treatment of human cancer

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) plays a key role in maintaining cellular metabolism. AMP or adenosine diphosphate (ADP) levels rise during metabolic stress, such as during nutrient starvation, hypoxia and muscle contraction, and bind to AMPK to induce activity. Recently, activation of AMPK has been considered an attractive therapeutic strategy in the field of human oncology. Structural optimization of lead compound 2, a new type of AMPK activator with potent AMPK activation activity and attractive selective growth inhibition against human cancer cells, improved aqueous solubility, metabolic stability and animal pharmacokinetics (PK) and culminated in the identification of (5-{1-[(6-methoxypyridin-3-yl)methyl]piperidin-4-yl}-1H-benzimidazol-2-yl)(4-{[4-(trifluoromethyl)phenyl]methyl}piperazin-1-yl)methanone ditosylate, ASP4132 (28). Studies on ASP4132 had advanced to clinical trials for the treatment of cancer.

Facile methodology of nanoemulsion preparation using oily polymer for the delivery of poorly soluble drugs

Aqueous solubility of an active pharmaceutical ingredient (API) is a determining factor that has a direct impact on formulation strategies and overall bioavailability. Fabrication of nanoemulsions of poorly soluble drugs is one of the widely utilized approaches to overcome this problem. However, thermodynamic instability and tedious manufacturing processes of nanoemulsions limit their clinical translation. Therefore, this study was focused on circumventing the abovementioned hurdles by utilizing the polymer as an oil phase, instead of conventional oils. The nanoemulsion was prepared via a facile low-energy nanoprecipitation method using renewable poly(δ-decalactone) (PDL), as an oil phase and Pluronic F-68 as surfactant. The prepared nanoemulsions were characterized in terms of size, drug encapsulation efficiency, stability, and toxicity. Five different hydrophobic drugs were utilized to evaluate the drug delivery capability of the PDL nanoemulsion. The prepared nanoemulsions with sizes less than 200 nm were capable to enhance the aqueous solubility of the drugs by 3 to 10 times compared with the well-established Pluronic F-68 micelles. No phase separation or significant changes in size and drug content was observed with PDL nanoemulsions after high-speed centrifugation and 3 months of storage at two different temperatures (20 °C and 50 °C). PDL nanoemulsions were found to be non-heamolytic up to concentrations of 1 mg/mL, and the cell cytotoxicity studies on MDA-MB-231 and MEF cells suggest a concentration and time-dependent toxicity, where the PDL polymer itself induced no cytotoxicity. The results from this study clearly indicate that the PDL polymer has a tremendous potential to be utilized as an oil phase to prepare stable nanoemulsions via a facile methodology, ultimately favouring clinical translations.

Graphical abstract

A new "off-on" NIR fluorescence probe for determination and bio-imaging of mitochondrial hypochlorite in living cells and zebrafish

Hypochlorite anion (ClO^-) has been recognized as host defense destructing incursive bacteria and pathogens, a signal molecule inducing occurrence of apoptosis and a noxious agent when it is overproduced. It is significant to detect ClO^- in mitochondria for getting meaningful physiological and pathological information. Compared with the fluorescence probes of emission wavelength in ultraviolet or visible region, those with near-infrared (NIR) fluorescence signal are advantageous due to the deeper tissue penetrability and less photo-bleaching effect. In this work, a new "off-on" NIR ClO^--specific fluorescence probe (Mito-NClO) especially located in mitochondria was designed and synthesized by condensation of diaminomaleonitrile with a new fluorophore (Mito-NCHO). A marked "turn-on" NIR fluorescence signal was observed on account of the oxidation of the imine bond by NaClO. Moreover, in the range from 0 to 20 μM, this probe had the capability to quantitatively detect ClO^- with a detection limit as low as 90.2 nM. Additionally, the probe exerted other excellent properties, including larger stokes shift (117 nm), better aqueous solubility, high selectivity toward ClO^-, rapid response and selective mitochondrial location. Furthermore, the bio-imaging experiments clearly demonstrated that Mito-NClO facilitated the visualization of exogenous and endogenous ClO^- in living HeLa cells and zebrafish model. Therefore, we speculate that the probe Mito-NClO can be served as an ideal tool for the monitoring of ClO^- in biosystems.

Aqueous Drug Solubility: What Do We Measure, Calculate and QSPR Predict?

Detailed critical analysis of publications devoted to QSPR of aqueous solubility is presented in the review with discussion of four types of aqueous solubility (three different thermodynamic solubilities with unknown solute structure, intrinsic solubility, solubility in physiological media at pH=7.4 and kinetic solubility), variety of molecular descriptors (from topological to quantum chemical), traditional statistical and machine learning methods as well as original QSPR models.

New findings on the incorporation of essential oil components into liposomes composed of lipoid S100 and cholesterol

The encapsulation of essential oil components into liposomes was demonstrated to improve their solubility and chemical stability. In this study, we investigated the effect of chemical structure, Henry's law constant (H_c), and aqueous solubility of essential oil components on their liposomal encapsulation. Estragole, eucalyptol, isoeugenol, pulegone, terpineol, and thymol were encapsulated in lipoid S100-liposomes using the ethanol injection method. The H_c values were determined. The incorporation in liposomes was more efficient (encapsulation efficiency > 90%) for the essential oil components exhibiting low aqueous solubility (estragole, isoeugenol, and pulegone). Moreover, efficient entrapment into vesicles (loading rate > 18%) was obtained for isoeugenol, terpineol, and thymol. This result suggests that the presence of a hydroxyl group in the structure and a low Hc value enhance the entrapment of essential oil components into liposomes. Furthermore, drug release rate from liposomes was controlled by the loading rate of essential oil components into liposomes, the size of particles, the location of essential oil components within the lipid bilayer, and the cholesterol incorporation rate of liposomes. Finally, considerable concentrations of isoeugenol, pulegone, terpineol, and thymol were retained in liposomes after 10 months with respect to the initial concentration.

Solubility, partitioning, oxidation and photodegradation of dichloroacetamide herbicide safeners, benoxacor and furilazole

Approximately 242 million kg of herbicides are applied in the United States (US) annually. While herbicides prevent the growth of weeds, they can damage crops resulting in so called "herbicide injury." To increase herbicidal tolerance of crops, herbicide safeners are commonly added to formulations. Herbicidal safeners are labeled as inert ingredients in herbicide formulations and typically minimal fate and transport information is available. The objective of this study is to experimentally derive the aqueous solubility, octanol-water partition coefficient, and photo-degradation and permanganate oxidation of two dichloroacetamide safeners, benoxacor and furilazole. These results can be used to understand the environmental chemodynamics of these compounds and their degradation via common drinking water treatment systems containing permanganate. The aqueous solubility of benoxacor and furilazole was 22 and 235 mg L^-1 respectively while the estimated solubility from EPI Suite was 102.7 and 255 mg L^-1 respectively. The log octanol-water partition coefficient of benoxacor and furilazole was 2.23 and 1.96 respectively. The selected safeners were not photodegradable to any great extent. Both benoxacor and furilazole oxidation were found to be second order with respect to initial KMnO₄ concentrations. The results of this study can be used to predict distribution of safeners after application in agricultural fields and aid in the design of treatment systems.

Silymarin-laden PVP-PEG polymeric composite for enhanced aqueous solubility and dissolution rate: Preparation and in vitro characterization

The aim of this work was to develop, optimize and characterize a silymarin-laden polyvinylpyrrolidone (PVP)-polyethylene glycol (PEG) polymeric composite to resolve low aqueous solubility and dissolution rate problem of the drug. A number of silymarin-laden polymeric formulations were fabricated with different quantities of PVP K-30 and PEG 6000 by the solvent-evaporation method. The effect of PVP K-30 and PEG 6000 on the aqueous solubility and dissolution rate was investigated. The optimized formulation and its constituents were characterized using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. Both the PEG 6000 and PVP K-30 positively affected the aqueous solubility and dissolution rate of the drug. In particular, a formulation consisting of silymarin, PVP K-30 and PEG 6000 (0.25/1.5/1.5, w/w/w) furnished the highest solubility (24.39±2.95 mg/mL) and an excellent dissolution profile (~100% in 40 min). The solubility enhancement with this formulation was ~1150-fold as compared to plain silymarin powder. Moreover, all the constituents existed in the amorphous state in this silymarin-laden PVP-PEG polymeric composite. Accordingly, this formulation might be a promising tool to administer silymarin with an enhanced effect via the oral route.

Mixed surfactant (altering chain length and head group) aggregates as an effective carrier for tuberculosis drug

Surface properties and aggregation behavior of cationic-cationic and cationic-non-ionic mixed surfactant systems viz. Dodecylethyldimethylammonium bromide (DDAB) with a series of double chain cationic surfactants (DiDDAB, DMDTAB, and DODAB) and non-ionic surfactants (Brij 96, Tyloxapol and Tween 80) were analysed using surface tension and transmission electron microscopy (TEM). The effect of chain length of cationic surfactant and hydrophilic-lypophilic balance (HLB) prominently observed in critical aggregation (cac) value. The aqueous solubility of anti-tuberculosis drug: rifampicin (RIF) was comparatively studied by UV-vis spectroscopy in presence of formulated micelles and vesicles. RIF was significantly solubilised in aqueous medium using all the formulated aggregates. RIF is very unstable in basic medium (above pH-7) and in oxidizing media. Therefore, stability at pH-13 as well as in strong oxidising environment was monitored using UV-vis spectroscopy. To trace the locus of the drug encapsulation in the micelles/vesicles, fluorescence spectroscopy and TEM studies were carried out. Both the techniques stemmed in complimentary results and confirmed that, RIF is majorly populated at polar medium in cationic-cationic vesicles and favour to reside at hydrophobic medium of the nonionic-cationic micelles.

Preparation and characterization of dialdehyde β-cyclodextrin with broad-spectrum antibacterial activity

Consumers demand more alternatives of riskless antibacterial agents to prevent microbial contamination in food industry. Oxidized carbohydrate may be a potential option as new antibacterial agent. However, the relatively weak antibacterial property of oxidized carbohydrate is not satisfactory. In this paper, dialdehyde β-cyclodextrins with different oxidation degree were prepared by periodate oxidation and their antibacterial properties were systematically studied. The results showed that multi-aldehyde groups were successfully introduced into β-cyclodextrin molecules by periodate oxidation. The aqueous solubility and stability of dialdehyde β-cyclodextrins were improved as expected. It is interesting that dialdehyde β-cyclodextrins possessed outstanding antibacterial activity against both Gram-positive and Gram-negative bacteria. The minimal inhibitory concentrations against E. coli, S. aureus and B. subtilis reached 0.63, 1.25 and 0.63 mg/mL, respectively. Moreover, dialdehyde β-cyclodextrins effectively inhibited bacterial growth on the surface of apples. The results demonstrated that oxidized oligosaccharide with multi-aldehyde groups and good dispersibility in aqueous solution possessed satisfactory antibacterial activity, which can be used as new antibacterial agent in food industry.

Intermolecular interaction as a direct measure of water solubility advantage of meloxicam cocrystalized with carboxylic acids

The solubility advantage (SA) of meloxicam cocrystalized with mono- and dicarboxylic acids was expressed in terms of equilibrium constants involving active pharmaceutical ingredient and coformer in aqueous solutions. It is argued that SA can be quantified by concentration of pairs formed in water. The pH and concentration of dissolved components is included explicitly in the model. The alternative behavior of mono- and dicarboxylic acids was emphasized and addressed to different structural motifs. The structural and energetic properties of meloxicam and its complexes with carboxylic acids were characterized, including tautmerism and dissociation in aqueous media. In particular, performed in silico modeling confirmed experimental observation that meloxicam dissolved in water or modest acidic solutions is expected to be a mixture of anionic form in equilibrium with at least five neutral isomers. Tautomer-related diversity of pairs formation and the possibility of salt formation is also discussed. Graphical abstract Two types of motifs found in meloxicam cocrystals reveal two sources of solubility advantage.

Estimations of the thermodynamic properties of halogenated benzenes as they relate to their environment mobility

In this work, several simple new equations for predicting important environmental mobility properties, at T = 298.15 K, were derived for halogenated benzenes: standard Gibbs energy of hydration, aqueous solubility, octanol-water partition coefficients, and Henry's law constants. A discussion on our previous estimates of other related properties (standard Gibbs energy and vapor pressure of sublimation and of vaporization) and their relation with entropy of fusion is also presented. As we aimed to estimate these properties for any of the ca. 1500 halogenated benzenes that may exist theoretically, an equation for estimating the temperature of fusion was also derived, since some of the proposed predictive equations (solubility of solids and Gibbs energy of sublimation) require its knowledge. For the other estimated properties just the number of each halogen that replaces hydrogen atoms in the halogenated benzene is needed. It was found that the coefficients that multiply the number of halogen atoms in the predictive equations vary linearly with the volume of the halogen atom.

Improvement in aqueous solubility achieved via small molecular changes

Overcoming poor solubility is a significant issue in drug discovery. The most common solution is to replace carbon atoms with polar heteroatoms such as N and O or by attaching a solubilizing appendage. This approach can lead to other issues such as poor activity and PK or the increased risk for toxicity. However, there are more subtle structural changes which can be employed that lead to an increase in solubility. These include, excising hydrophobic groups which do not efficiently contribute to binding, modifying stereo- and regiochemistry, increasing or decreasing the degree of unsaturation or adding small hydrophobic groups such as fluorine or methyl.

Six global and local QSPR models of aqueous solubility at pH = 7.4 based on structural similarity and physicochemical descriptors

Aqueous solubility at pH = 7.4 is a very important property for medicinal chemists because this is the pH value of physiological media. The present work describes the application of three different methods (support vector machine (SVM), random forest (RF) and multiple linear regression (MLR)) and three local quantitative structure-property relationship (QSPR) models (regression corrected by nearest neighbours (RCNN), arithmetic mean property (AMP) and local regression property (LoReP)) to construct stable QSPRs with clear mechanistic interpretation. Our data set contained experimental values of aqueous solubility at pH = 7.4 of 387 chemicals (349 in the training set and 38 in the test set including 16 own measurements). The initial descriptor pool contained 210 physicochemical descriptors, calculated from the HYBOT, DRAGON, SYBYL and VolSurf+ programs. Six QSPRs with good statistics based on fundamentals of aqueous solubility and optimization of descriptor space were obtained. Those models have an RMSE close to experimental error (0.70), and are amenable to physical interpretation. The QSPR models developed in this study may be useful for medicinal chemists. Global MLR, RF and SVM models may be valuable for consideration of common factors that influence solubility. The RCNN, AMP and LoReP local models may be helpful for the optimization of aqueous solubility in small sets of related chemicals.

Novel hybrids of natural β-elemene bearing isopropanolamine moieties: Synthesis, enhanced anticancer profile, and improved aqueous solubility

A series of novel β-elemene isopropanolamine derivatives were synthesized and evaluated for their antitumor activity. The results indicated that all of the compounds showed stronger antiproliferative activities than β-elemene as well as improved aqueous solubility. In particular dimer 6q showed the strongest cytotoxicity against four tumor cell lines (SGC-7901, HeLa, U87 and A549) with IC₅₀ values ranging from 4.37 to 10.20μM. Moreover, combination of 6q with cisplatin exhibited a synergistic effect on these cell lines with IC₅₀ values ranging from 1.21 to 2.94μM, and reversed the resistance of A549/DPP cells with an IC₅₀ value of 2.52μM. The mechanism study revealed that 6q caused cell cycle arrest at the G2 phase and induced apoptosis of SGC-7901 cells through a mitochondrial-dependent apoptotic pathway. Further in vivo study in H22 liver cancer xenograft mouse model validated the antitumor activity of 6q with a tumor inhibitory ratio (TIR) of 60.3%, which was higher than that of β-elemene (TIR, 49.1%) at a dose of 60mg/kg. Altogether, the potent antitumor activity of 6qin vitro and in vivo warranted further preclinical investigation for potential anticancer chemotherapy.

Quantification of apigenin trimethyl ether in rat plasma by liquid chromatography-tandem mass spectrometry: Application to a pre-clinical pharmacokinetic study

Apigenin trimethyl ether (5,7,4'-trimethoxyflavone, ATE) is a naturally occurring polymethoxyflavone with a wide range of health-promoting activities. In this study, a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of ATE in rat plasma. Protein precipitation was applied as plasma clean-up procedure; the electrospray ionization was operated in its positive ion mode while ATE and formononetin (internal standard) were measured by multiple reactions monitoring (ATE: m/z 313.1→298.1; formononetin: 269.2→213.3). This LC-MS/MS method displayed good selectivity, sensitivity (lower limit of quantification=2.5ng/ml), accuracy (both intra- and inter-day analytical recovery within 100±10%) and precision (both intra- and inter-day RSD <10%). The matrix effect was found to be insignificant. The pharmacokinetic profiles of ATE were subsequently examined in Sprague-Dawley rats after single oral administration (10mg/kg). When given in an aqueous suspension, ATE was slowly absorbed with quite low plasma exposure (AUC). Fasting further attenuated its oral absorption and led to ∼70% drops in average maximal plasma concentration (C_max) and AUC. When dosed in a solution formulated with 2-hydroxypropyl-β-cyclodextrin, the oral absorption of ATE was substantially improved with ∼500% increases in average C_max and AUC. Clearly, aqueous solubility has been identified as a barrier to the oral absorption of ATE. The information obtained from this study will facilitate further medicinal exploration on ATE.

Systematic Study of Effects of Structural Modifications on the Aqueous Solubility of Drug-like Molecules

Aqueous solubilities and activities have been measured for 17 members of the quinolinyltriazole series of inhibitors of human macrophage migration inhibitory factor (MIF). Systematic variation of a solvent-exposed substituent provided increases in solubility from 2 μg/mL for the parent compound 3a up to 867 μg/mL. The low solubility of 3a results from its near-planar structure and an intermolecular hydrogen bond, as revealed in a small-molecule X-ray structure. Removal of the hydrogen bond yields a 3-fold increase in solubility, but a 7-fold drop in activity. 5b emerges as the most potent MIF inhibitor with a K_i of 14 nM and good solubility, 47 μg/mL, while 4e has both high potency and solubility.

Design and synthesis of water soluble β-aminosulfone analogues of SCH 900229 as γ-secretase inhibitors

In this paper we describe our strategy to improve the aqueous solubility of SCH 900229, a potent PS1-selective γ-secretase inhibitor for the treatment of Alzheimer's disease. Incorporation of ionizable amino groups into the side chain terminal generates water soluble β-aminosulfone analogues of SCH 900229 that maintain robust in vitro potency and in vivo efficacy.

1-Heteroarylpropan-2-ones as inhibitors of fatty acid amide hydrolase: Studies on structure-activity relationships and metabolic stability

The serine hydrolase fatty acid amide hydrolase (FAAH) catalyzes the degradation of the endocannabinoid anandamide, which possesses analgesic and anti-inflammatory effects. A new series of 1-heteroarylpropan-2-ones was synthesized and evaluated for FAAH inhibition. Structure-activity relationship studies revealed that 1H-benzotriazol-1-yl, 1H-7-azabenzotriazol-1-yl, 1H-tetrazol-1-yl and 2H-tetrazol-2-yl substituents have the highest impact on inhibitory potency. Furthermore, attempts were made to increase the limited metabolic stability of the ketone functionality of these compounds towards metabolic reduction by introduction of shielding alkyl substituents in proximity of this serine reactive group.

Structure-activity relationship studies on 1-(2-oxopropyl)indole-5-carboxylic acids acting as inhibitors of cytosolic phospholipase A2α: Effect of substituents at the indole 3-position on activity, solubility, and metabolic stability

Cytosolic phospholipase A₂α (cPLA₂α) is a key enzyme in the biosynthesis of pro-inflammatory lipid mediators and therefore represents an attractive target for the development of new anti-inflammatory drugs. Recently, we have found that 1-[3-(4-octylphenoxy)-2-oxopropyl]indole-5-carboxylic acid (4) is a potent inhibitor of the enzyme. In this work, we evaluate the effect of butanoyl- and hexanoyl-substituents in position 3 of the indole scaffold of this compound bearing terminal groups of varying polarity. As a result, inhibitory potency was not affected considerably in most cases, while metabolic phase I and phase II in vitro stability and aqueous solubility could be influenced and modulated by the structural modifications performed.

Aqueous solubilities of five N-(diethylaminothiocarbonyl)benzimido derivatives at T = 298.15 K

N-(diethylaminothiocarbonyl)benzimido derivatives are polar multifunctional substances. A set of these compounds was synthesised by successive substitution on the enamine side, resulting in similar substances with different polarities, providing a set of model compounds with respect to the study of substituent effects on physico-chemical properties. Experimental aqueous solubility data, at T = 298.15 K, of N-(diethylaminothiocarbonyl)benzamidine, PhCNH2NCSNEt2 (1),N-(diethylaminothiocarbonyl)-N'-phenylbenzamidine, PhCNHPhNCSNEt2 (2), N-(diethylaminothiocarbonyl)-N'-monoethylbenzamidine, PhCNHEtNCSNEt2 (3), N-(diethylaminothiocarbonyl)-N',N'-diethylbenzamidine, PhCNEt2NCSNEt2 (4), and N-(diethylaminothiocarbonyl)benzimido ethylester, PhCOEtNCSNEt2 (5) were measured at T = 298.15 K. The obtained data are supplemented by COSMO-RS aqueous solubility predictions as well as other environmentally important partition coefficients. This information is shown in a two-dimensional chemical space diagram, providing indications about the compartment into which the bulk of the compounds is likely to concentrate. The expected quality of COSMO-RS predictions for this type of screening exercise is illustrated on a set of pesticides with established thermophysical property data.

Quantitative Regression Models for the Prediction of Chemical Properties by an Efficient Workflow

Rapid safety assessment is more and more needed for the increasing chemicals both in chemical industries and regulators around the world. The traditional experimental methods couldn't meet the current demand any more. With the development of the information technology and the growth of experimental data, in silico modeling has become a practical and rapid alternative for the assessment of chemical properties, especially for the toxicity prediction of organic chemicals. In this study, a quantitative regression workflow was built by KNIME to predict chemical properties. With this regression workflow, quantitative values of chemical properties can be obtained, which is different from the binary-classification model or multi-classification models that can only give qualitative results. To illustrate the usage of the workflow, two predictive models were constructed based on datasets of Tetrahymena pyriformis toxicity and Aqueous solubility. The qcv (2) and qtest (2) of 5-fold cross validation and external validation for both types of models were greater than 0.7, which implies that our models are robust and reliable, and the workflow is very convenient and efficient in prediction of various chemical properties.

Novel free fatty acid receptor 1 (GPR40) agonists based on 1,3,4-thiadiazole-2-carboxamide scaffold

Free fatty acid receptor 1 (FFA1), previously known as GPR40 is a G protein-coupled receptor and a new target for treatment of type 2 diabetes. Two series of FFA1 agonists utilizing a 1,3,4-thiadiazole-2-caboxamide scaffold were synthetized. Both series offered significant improvement of the potency compared to the previously described 1,3,4-thiadiazole-based FFA1 agonists and high selectivity for FFA1. Molecular docking predicts new aromatic interactions with the receptor that improve agonist potency. The most potent compounds from both series were profiled for in vitro ADME properties (plasma and metabolic stability, LogD, plasma protein binding, hERG binding and CYP inhibition). One series suffered very rapid degradation in plasma and in presence of mouse liver microsomes. However, the other series delivered a lead compound that displayed a reasonable ADME profile together with the improved FFA1 potency.

Novel diarylpyrimidines and diaryltriazines as potent HIV-1 NNRTIs with dramatically improved solubility: a patent evaluation of US20140378443A1

Diarylpyrimidine and diaryltriazine derivatives, two representative structurally related classes of HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) with robust potencies against wild-type and several mutant strains of HIV-1, have attracted more and more attention in the last decade. However, they have been suffering from poor aqueous solubility. A series of novel diarylpyrimidines and diaryltriazines with solubilizing substituents attached to the central rings were reported as potent NNRTIs in the patent US20140378443A1. Some compounds exhibited potencies against wild-type HIV-1 which were comparable or even superior to those of dapivirine, etravirine and rilpivirine. In addition, dramatically enhanced solubilities were observed for these new compounds. Moreover, some structure optimization strategies for improving aqueous solubility are detailed in this review, providing new insights into development of next-generation NNRTIs endowed with favorable solubility. We anticipate that application of these strategies will ultimately lead to discovery of new anti-HIV drug candidates.

Externally predictive single-descriptor based QSPRs for physico-chemical properties of polychlorinated-naphthalenes: Exploring relationships of logS(W), logK(OA), and logK(OW) with electron-correlation

Quantitative structure-property relationships (QSPRs), based only on a single-parameter, are proposed for the prediction of physico-chemical properties, namely, aqueous solubility (logSW), octanol-water partition coefficient (logKOW) and octanol-air partition coefficient (logKOA) of polychloronaphthalenes (PCNs) including all the 75 chloronaphthalene congeners. The QSPR models are developed using molecular descriptors computed through quantum mechanical methods including ab-initio as well as advanced semi-empirical methods. The predictivity of the developed models is tested through state-of-the-art external validation procedures employing an external prediction set of compounds. To analyse the role of instantaneous interactions between electrons (the electron-correlation), the models are also compared with those developed using only the electron-correlation contribution of the quantum chemical descriptor. The electron-correlation contribution towards the chemical hardness and the LUMO energy are observed to be the best predictors for octanol-water partition coefficient, whereas for the octanol-air partition coefficient, the total electronic energy and electron-correlation energy are found to be reliable descriptors, in fact, even better than the polarisability. For aqueous solubility of PCNs, the absolute electronegativity is observed to be the best predictor. This work suggests that the electron-correlation contribution of a quantum-chemical descriptor can be used as a reliable indicator for physico-chemical properties, particularly the partition coefficients.

In silico Prediction of Aqueous Solubility: a Comparative Study of Local and Global Predictive Models

32 Quantitative Structure-Property Relationship (QSPR) models were constructed for prediction of aqueous intrinsic solubility of liquid and crystalline chemicals. Data sets contained 1022 liquid and 2615 crystalline compounds. Multiple Linear Regression (MLR), Support Vector Machine (SVM) and Random Forest (RF) methods were used to construct global models, and k-nearest neighbour (kNN), Arithmetic Mean Property (AMP) and Local Regression Property (LoReP) were used to construct local models. A set of the best QSPR models was obtained: for liquid chemicals with RMSE (root mean square error) of prediction in the range 0.50-0.60 log unit; for crystalline chemicals 0.80-0.90 log unit. In the case of global models the large number of descriptors makes mechanistic interpretation difficult. The local models use only one or two descriptors, so that a medicinal chemist working with sets of structurally-related chemicals can readily estimate their solubility. However, construction of stable local models requires the presence of closely related neighbours for each chemical considered. It is probable that a consensus of global and local QSPR models will be the optimal approach for construction of stable predictive QSPR models with mechanistic interpretation.

Interpreting physicochemical experimental data sets

With the wealth of experimental physicochemical data available to chemoinformaticians from the literature, commercial, and company databases an increasing challenge is the interpretation of such datasets. Subtle differences in experimental methodology used to generate these datasets can give rise to variations in physicochemical property values. Such methodology nuances will be apparent to an expert experimentalist but not necessarily to the data analyst and modeller. This paper describes the differences between common methodologies for measuring the four most important physicochemical properties namely aqueous solubility, octan-1-ol/water distribution coefficient, pK(a) and plasma protein binding highlighting key factors that can lead to systematic differences. Insight is given into how to identify datasets suitable for combining.

Parenterally administrable nano-micelles of 3,4-difluorobenzylidene curcumin for treating pancreatic cancer

Pancreatic cancer remains one of the most devastating diseases in terms of patient mortality rates for which current treatment options are very limited. 3,4-Difluorobenzylidene curcumin (CDF) is a nontoxic analog of curcumin (CMN) developed in our laboratory, which exhibits extended circulation half-life, while maintaining high anticancer activity and improved pancreas specific accumulation in vivo, compared with CMN. CDF however has poor aqueous solubility and its dose escalation for systemic administration remains challenging. We have engineered self-assembling nano-micelles of amphiphilic styrene-maleic acid copolymer (SMA) with CDF by non-covalent hydrophobic interactions. The SMA-CDF nano-micelles were characterized for size, charge, drug loading, release, serum stability, and in vitro anticancer activity. The SMA-CDF nano-micelles exhibited tunable CDF loading from 5 to 15% with excellent aqueous solubility, stability, favorable hemocompatibility and sustained drug release characteristics. The outcome of cytotoxicity testing of SMA-CDF nano-micelles on MiaPaCa-2 and AsPC-1 pancreatic cancer cell lines revealed pronounced antitumor response due to efficient intracellular trafficking of the drug loaded nano-micelles. Additionally, the nano-micelles are administrable via the systemic route for future in vivo studies and clinical translation. The currently developed SMA based nano-micelles thus portend to be a versatile carrier for dose escalation and targeted delivery of CDF, with enhanced therapeutic margin and safety.