Investigating molecular interactions of high-loaded glipizide-HPMCAS microparticles by integrated experimental and modeling techniques

Design of Coamorphous Systems for Flavonoid Components Coformed with Meglumine by Integrating Theory-Model-Experiment Techniques

Flavonoids represent an extensive group of phenolic substances in vegetables, fruits, grains, tea, flowers, etc., which show a variety of biological activities in various nutraceutical, cosmetic, and medicinal fields. Despite demonstrating multifunctional bioactive properties relevant to nutraceutical and pharmaceutical applications, their clinical utilization faces challenges due to their generally low water solubility. This study established a systematic methodology combining computational modeling and experimental validation for developing flavonoid-meglumine (MEG) coamorphous formulations. The initial screening identified 13 flavonoid compounds exhibiting favorable miscibility with MEG from 15 candidates through Hansen solubility parameter analysis. Subsequent molecular dynamics simulations revealed potential hydrogen bond formation in six selected flavonoids (BAI, HES, NAR, KAE, QUE, and ISO) with MEG. Then, six flavonoid coamorphous systems were successfully prepared via the melt-quenching method and characterized by PLM, PXRD, and differential scanning calorimetry. FTIR and radial distribution function analysis results collectively confirmed intermolecular hydrogen bond interactions within these binary systems. In vitro dissolution studies revealed significant solubility/dissolution enhancement in both pH 1.2 HCl and pH 6.8 phosphate buffers, maintaining long-term supersaturation for all six coamorphous formulations. Meanwhile, six flavonoid coamorphous systems had superior stability over individual flavonoid amorphous components, which were attributed to the stronger intermolecular interactions by higher binding energy calculation. These results indicated that the obtained flavonoid coamorphous systems performed a promising application potential in functional products. Importantly, this study presents a novel design framework integrating computational prediction, molecular modeling, and experimental validation for systematic screening of flavonoid coamorphous formulations.

A New Screening Strategy for Flavonoid Components to Obtain a Satisfactory Co-Amorphous System with Piperine

Flavonoids are a large class of compounds with a variety of biological activities. Nevertheless, their therapeutic application remains limited due to the generally low water solubility. In the present study, an integrated approach was provided to guide the design of flavonoid co-amorphous systems co-formed with piperine (PIP). Firstly, 7 flavonoid compounds showed good miscibility with PIP from 13 flavonoid candidates. Then, molecular dynamics simulation confirmed hydrogen bond formation between 5 flavonoid compounds (i.e., BAI, HES, ISO, NAR and KAE) and PIP. Herein, 5 flavonoid compounds were successfully co-amorphized with PIP by the melting and quench cooling method, which were proved via PLM, PXRD and DSC measurements. FTIR results showed the potential hydrogen bond interactions between -OH of flavonoid molecules and C = O of PIP molecule in the formed co-amorphous systems, which were consistent with RDF analyses in molecular models. For dissolution tests, 4 co-amorphous systems (i.e., BAI-PIP CM, HES-PIP CM, ISO-PIP CM and NAR-PIP CM) appeared abnormally reduced dissolution compared to their original crystalline counterparts arising from the formation of gels during dissolution, while only KAE-PIP CM displayed significantly enhanced dissolution (5.83-fold of crystalline KAE at 12 h) with long-time supersaturated concentration. Meanwhile, KAE-PIP CM kept physically stable at least 3 months under 25°C and 40°C conditions, and possessed excellent physical stability over individual amorphous components, which was attributed to the stronger intermolecular interaction by higher binding energy analysis. Therefore, this study provides a design strategy to guide the screening of flavonoid co-amorphous systems through combining theory-model-experiment techniques.

Prediction of Successful Amorphous Solid Dispersion Pairs through Liquid State Nuclear Magnetic Resonance

Amorphous solid dispersions (ASDs) function in part via a "parachute effect", i.e., polymer-enabled prolonged drug supersaturation, presumably through drug-polymer interactions in the liquid state. We aim to expand the utility of liquid state nuclear magnetic resonance (1HNMR) to streamline polymer selection for ASDs. Our hypothesis is that strong molecular interactions between polymer and drug in 1HNMR anticipate reduced precipitation kinetics in supersaturation studies. For three drug-polymer pairs (i.e., etravirine with each HPMC, HPMCAS-M, and PVP-VA), 1HNMR findings were compared to more common supersaturation studies. Drug-polymer interactions were assessed by saturation transfer difference NMR (STD-NMR) and T1 relaxation time. 2D-1H NOESY experiments were also performed. Supersaturation studies involved precipitation inhibition using the solvent-shift methodology. The results from STD-NMR and T1 relaxation time indicate etravirine bound preferably to HPMCAS-M > HPMC ≫ PVP-VA. STD-NMR and T1 relaxation time yielded insight into which fragments of etravirine structure bind with HPMCAS-M and HPMC. The strong interactions from STD-NMR and T1 relaxation time changes indicated that HPMCAS-M and HPMC, but not PVP-VA, are suitable polymers to maintain etravirine supersaturation and inhibit drug precipitation. 2D-1H NOESY results corroborate the findings of STD-NMR and T1 relaxation time, showing that etravirine interacts preferably to HPMCAS-M than to PVP-VA. Supersaturation studies using solvent-shift technique corroborated our hypothesis as predissolved HPMCAS-M and HPMC, but to a less extent PVP-VA, markedly promoted etravirine supersaturation and inhibited drug precipitation. Supersaturation studies agreed with STD-NMR and T1 relaxation time predictions, as HPMC and HPMCAS-M maintained etravirine in solution for longer time than PVP-VA. The results show promise of 1HNMR to streamline polymer selection in a nondestructive and resource sparing fashion for subsequent ASD development.

Insight into Formation, Synchronized Release and Stability of Co-Amorphous Curcumin-Piperine by Integrating Experimental-Modeling Techniques

Intermolecular interactions between drug and co-former are crucial in the formation, release and physical stability of co-amorphous system. However, the interactions remain difficult to investigate with only experimental tools. In this study, intermolecular interactions of co-amorphous curcumin-piperine (i.e., CUR-PIP CM) during formation, dissolution and storage were explored by integrating experimental and modeling techniques. The formed CUR-PIP CM exhibited the strong hydrogen bond interaction between the phenolic OH group of CUR and the CO group of PIP as confirmed by FTIR, ss 13C NMR and molecular dynamics (MD) simulation. In comparison to crystalline CUR, crystalline PIP and their physical mixture, CUR-PIP CM performed significantly increased dissolution accompanied by the synchronized release of CUR and PIP, which arose from the greater interaction energy of H2O-CUR molecules and H2O-PIP molecules than CUR-PIP molecules, breaking the hydrogen bond between CUR and PIP molecules, and then causing a pair-wise solvation of CUR-PIP CM at the molecular level. Furthermore, the stronger intermolecular interaction between CUR and PIP was revealed by higher binding energy of CUR-PIP molecules, which contributed to the excellent physical stability of CUR-PIP CM over amorphous CUR or PIP. The study provides a unique insight into the formation, release and stability of co-amorphous system from MD perspective. Meanwhile, this integrated technique can be used as a practical methodology for the future design of co-amorphous formulations.

Comparative analysis of drug-salt-polymer interactions by experiment and molecular simulation improves biopharmaceutical performance

The propensity of poorly water-soluble drugs to aggregate at supersaturation impedes their bioavailability. Supersaturated amorphous drug-salt-polymer systems provide an emergent approach to this problem. However, the effects of polymers on drug-drug interactions in aqueous phase are largely unexplored and it is unclear how to choose an optimal salt-polymer combination for a particular drug. Here, we describe a comparative experimental and computational characterization of amorphous solid dispersions containing the drug celecoxib, and a polymer, polyvinylpyrrolidone vinyl acetate (PVP-VA) or hydroxypropyl methylcellulose acetate succinate, with or without Na+/K+ salts. Classical models for drug-polymer interactions fail to identify the best drug-salt-polymer combination. In contrast, more stable drug-polymer interaction energies computed from molecular dynamics simulations correlate with prolonged stability of supersaturated amorphous drug-salt-polymer systems, along with better dissolution and pharmacokinetic profiles. The celecoxib-salt-PVP-VA formulations exhibit excellent biopharmaceutical performance, offering the prospect of a low-dosage regimen for this widely used anti-inflammatory, thereby increasing cost-effectiveness, and reducing side-effects.

Influence of the pK a Value of Cinnamic Acid and P-Hydroxycinnamic Acid on the Solubility of a Lurasidone Hydrochloride-Based Coamorphous System

Coamorphization of a poorly water-soluble active pharmaceutical ingredient (API) has been proven to be effective in improving its solubility. Generally, API can form multiple coamorphous systems with different coformers. However, it remains unclear how the pK _a value of different coformers influences the solubility of the API. In this study, structurally related cinnamic acid (CA, pK _a = 4.37) and p-hydroxycinnamic acid (pHCA, pK _a = 4.65) were chosen as coformers for the coamorphization of lurasidone hydrochloride (LH). To investigate the influence of the pK _a value of the coformers on the solubility of LH, LH-CA/pHCA coamorphous systems were prepared by the vacuum rotary evaporation method and characterized by powder X-ray diffraction and differential scanning calorimetry. Fourier-transform infrared spectroscopy, Raman spectroscopy, and molecular dynamics (MD) simulations were employed to investigate the intermolecular interaction of the coamorphous systems. It was found that the solubility of LH in the coamorphous LH-pHAC with a higher-pK _a coformer was higher than that of the coamorphous LH-CA. In addition, according to the solubility product principle-based formula derivation, we established the functional relationship between the solubility of LH and the pK _a of the coformers at different-pH buffering solution. It was found that the coformer with a larger pK _a value would be more beneficial to improve the solubility profile of LH. Collectively, the current study offers an effective strategy to improve the poor solubility of drugs by increasing the pK _a value of the coformer in coamorphous systems.

An integrated computational methodology with data-driven machine learning, molecular modeling and PBPK modeling to accelerate solid dispersion formulation design

Drugs in solid dispersion (SD) take advantage of fast and extended dissolution, thus attains a higher bioavailability than the crystal form. However, current development of SD relies on a random large-scale formulation screening method with low efficiency. Current research aims to integrate various computational tools, including machine learning (ML), molecular dynamic (MD) simulation and physiologically based pharmacokinetic (PBPK) modeling, to accelerate the development of SD formulations. Firstly, based on a dataset consisting of 674 dissolution profiles of SD, the random forest algorithm was used to construct a classification model to distinguish two types of dissolution profiles: "spring-and-parachute" and "maintain supersaturation", and a regression model to predict the time-dependent dissolution profiles. Both of the two prediction models showed good prediction performance. Moreover, feature importance was performed to help understand the key information that contributes to the model. After that, the vemurafenib (VEM) SD formulation in previous report was used as an example to validate the models. MD simulation was used to investigate the dissolution behavior of two SD formulations with two polymers (HPMCAS and Eudragit) at the molecular level. The results showed that the HPMCAS-based formulation resulted in faster dissolution than the Eudragit formulation, which agreed with the reported experimental results. Finally, a PBPK model was constructed to accurately predict the human pharmacokinetic profile of the VEM-HPMCAS SD formulation. In conclusion, combined computational tools have been developed to in silico predict formulation composition, in vitro release and in vivo absorption behavior of SD formulations. The integrated computational methodology will significantly facilitate pharmaceutical formulation development than the traditional trial-and-error approach in the laboratory.

Interpreting In Vitro Release Performance from Long-Acting Parenteral Nanosuspensions Using USP-4 Dissolution and Spectroscopic Techniques

Injectable sustained release dosage forms have emerged as desirable therapeutic routes for patients that require life-long treatments. The prevalence of drug molecules with low aqueous solubility and bioavailability has added momentum toward the development of suspension-based long-acting parenteral (LAP) formulations; the previously undesirable physicochemical properties of Biopharmaceutics Classification System (BCS) Class II/IV compounds are best suited for extended release applications. Effective in vitro release (IVR) testing of crystalline suspensions affirms product quality during early-stage development and provides connections with in vivo performance. However, before in vitro-in vivo correlations (IVIVCs) can be established, it is necessary to evaluate formulation attributes that directly affect IVR properties. In this work, a series of crystalline LAP nanosuspensions were formulated with different stabilizing polymers and applied to a continuous flow-through (USP-4) dissolution method. This technique confirmed the role of salt effects on the stability of polymer-coated nanoparticles through the detection of disparate active pharmaceutical ingredient (API) release profiles. The polymer stabilizers with extended hydrophilic chains exhibited elevated intrapolymer activity from the loss of hydrogen-bond cushioning in dissolution media with heightened ionic strength, confirmed through one-dimensional (1D) ¹H NMR and two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY) experiments. Thus, steric repulsion within the affected nanosuspensions was limited and release rates decreased. Additionally, the strength of interaction between hydrophobic polymer components and the API crystalline surface contributed to suspension dissolution properties, confirmed through solution- and solid-state spectroscopic analyses. This study provides a unique perspective on the dynamic interface between the crystalline drug and aqueous microenvironment during dissolution.

A novel lurasidone hydrochloride–shikimic acid co-amorphous system formed by hydrogen-bonding interaction with the retained pH-dependent solubility behavior

The current study was aimed at investigating the lurasidone hydrochloride–shikimic acid co-amorphous system using a new type of organic acid.