Multiphysics-Informed Pharmacokinetic Modeling of Systemic Exposure of Intramuscularly Injected LNPs.

Lipid nanoparticle (LNP) constructs have been widely developed for gene therapy delivery. Understanding local absorption and presystemic clearance kinetics of LNPs, however, remains limited. This subsequently restrains the prediction and assessment of the systemic exposure of locally injected LNPs. As such, a multiscale computational approach was developed by integrating multiphysics simulation of intramuscular absorption kinetics of LNPs with whole-body pharmacokinetics modeling, bridged by a presystemic lymphatic kinetic model. The overall framework was enabled by utilizing physiological parameters obtained from the literature and drug-related parameters derived from experiments. The multiscale modeling and simulation approach predicted the systemic exposure of LNPs administered intramuscularly, with a high degree of agreement between the predicted and the experimental data. Sensitivity analyses revealed that the local absorption rate, pinocytosis presystemic clearance rate, and lymph flow rate of the presystemic lymphatic compartment had the most significant impacts on Cmax. The study yielded refreshing perspectives on estimating systemic exposures of locally injected LNPs and their safety and effectiveness.

A Perspective on Model-Informed IVIVC for Development of Subcutaneous Injectables.

Subcutaneously administered drugs are growing in popularity for both large and small molecule drugs. However, development of these systems - particularly generics - is slowed due to a lack of formal guidance regarding preclinical testing and in vitro - in vivo correlations (IVIVC). Many of these methods, while appropriate for oral drugs, may not be optimized for the complex injection site physiologies, and release rate and absorption mechanisms of subcutaneous drugs. Current limitations for formulation design and IVIVC can be supported by implementing mechanistic, computational methods. These methods can help to inform drug development by identifying key drug and formulation attributes, and their effects on drug release rates. This perspective, therefore, addresses current guidelines in place for oral IVIVC development, how they may differ for subcutaneously administered compounds, and how modeling and simulation can be implemented to inform design of these products. As such, integration of modeling and simulation with current IVIVC systems can help in driving the development of subcutaneous injectables.

Multiphysics Simulation of Local Transport and Absorption Coupled with Pharmacokinetic Modeling of Systemic Exposure of Subcutaneously Injected Drug Solution.

INTRODUCTION: Subcutaneous (SC) injectables have become more acceptable and feasible for administration of biologics and small molecules. However, efficient development of these products is limited to costly and time-consuming techniques, partially because absorption mechanisms and kinetics at the local site of injection remain poorly understood. OBJECTIVE: To bridge formulation critical quality attributes (CQA) of injectables with local physiological conditions to predict systemic exposure of these products. METHODOLOGY: We have previously developed a multiscale, multiphysics computational model to simulate lymphatic absorption and whole-body pharmacokinetics of monoclonal antibodies. The same simulation framework was applied in this study to compute the capillary absorption of solubilized small molecule drugs that are injected subcutaneously. Sensitivity analyses were conducted to probe the impact by key simulation parameters on the local and systemic exposures. RESULTS: This framework was capable of determining which parameters had the biggest impact on small molecule absorption in the SC. Particularly, membrane permeability of a drug was found to have the biggest impact on drug absorption kinetics, followed by capillary density and drug diffusivity. CONCLUSION: Our modelling framework proved feasible in predicting local transport and systemic absorption from the injection site of small molecules. Understanding the effect of these properties and how to model them may help to greatly expedite the development process.

Kinetic Retraction at the Onset of Concomitant Crystallization and Implication on Polymorphic Formation.

The four-quadrant regimes of attainable polymorph crystallization (FQR-APC) plot was recently developed through numerical simulations of crystallization kinetics of a dipolymorphic system. Retraction in the polymorphic composition of the most stable form in crystallized samples was unveiled a characteristic indication of concomitant polymorphism. Comparisons were made with a recently developed concept, the Ostwald ratio (OR), in light of characterization of polymorphic formation. It was shown that both schemes display a good agreement in describing polymorphic outcomes, despite their distinct theoretical origins.

Understanding Formulation and Temperature Effects on Dermal Transport Kinetics by IVPT and Multiphysics Simulation.

PURPOSE: It is often unclear how complex topical product formulation factors influence the transport kinetics through skin tissue layers, because of multiple confounding attributes. Environmental factors such as temperature effect are also poorly understood. In vitro permeation testing (IVPT) is frequently used to evaluate drug absorption across skin, but the flux results from these studies are from a combination of mechanistic processes. METHOD: Two different commercially available formulations of oxybenzone-containing sunscreen cream and continuous spray were evaluated by IVPT in human skin. Temperature influence between typical skin surface temperature (32°C) and an elevated 37°C was also assessed. Furthermore, a multiphysics-based simulation model was developed and utilized to compute the flux of modeled formulations. RESULTS: Drug transport kinetics differed significantly between the two drug products. Flux was greatly influenced by the environmental temperature. The multiphysical simulation results could reproduce the experimental observations. The computation further indicated that the drug diffusion coefficient plays a dominant role in drug transport kinetics, influenced by the water content which is also affected by temperature. CONCLUSION: The in vitro testing and bottom-up simulation shed insight into the mechanism of dermal absorption kinetics from dissimilar topical products.

Biodistribution and Non-linear Gene Expression of mRNA LNPs Affected by Delivery Route and Particle Size.

PURPOSE: Lipid nanoparticles (LNPs) are widely utilized as means to deliver mRNA molecules. However, metric connections between biodistribution and pharmacokinetics (PK) of the nanoparticle carrier and transgene expression dynamics remain largely unknown. METHODS: LNPs containing mRNAs encoding the firefly luciferase gene were prepared with varying sizes. Biodistributions of injected LNPs in mice were measured by fluorescence bioimaging or liquid chromatography with tandem mass spectrometry. In addition, luciferase expression levels were determined by bioluminescence imaging and enzyme activity assays. RESULTS: Some intramuscularly injected LNPs were found circulating in the system, resulting in accumulation in the liver and spleen, especially when the LNP sizes were relatively small. Bigger LNPs were more likely to remain at the injection site. Transgene expression in the liver was found most prominent compared with other organs and tissues. CONCLUSIONS: Biomolecules such as mRNAs encapsulated in locally injected LNPs can reach other organs and tissues via systemic circulation. Gene expression levels are affected by the LNP biodistribution and pharmacokinetics (PK), which are further influenced by the particle size and injection route. As transfection efficiency varies in different organs, the LNP exposure and mRNA expression are not linearly correlated.

Hydroxypropyl Beta Cyclodextrin as a Potential Surface Modifier for Paclitaxel Nanocrystals.

Paclitaxel (PTX) is a hydrophobic chemotherapeutic agent cytotoxic against many serious cancers. This study aimed at designing novel PTX nanocrystals (PTX-NCs) coated with the biocompatible and biodegradable hydroxypropyl-beta-cyclodextrin (HPßCD) polymer with specific characteristics through the formation of a non-inclusion complex. Briefly, PTX-NCs were prepared by the anti-solvent method followed by homogenization. Then, the surface of the prepared PTX-NCs was modified using the HPßCD coat (HPßCD-PTX-NCs). The prepared nanocrystals, both coated and uncoated, were characterized in terms of size, polydispersity index, charge, morphology, and stability. Moreover, the nanocrystals were investigated using powder X-ray diffraction (PXRD), differential scanning calorimeter (DSC), and Fourier transform infrared spectroscopy (FTIR). As well, the in vitro release of PTX from the nanocrystals was determined under conditions similar to the IV route of administration. Furthermore, the tendency of the nanocrystals to induce hemolysis was investigated. Results indicated that the size was about 241.4 and 310.5 nm, the polydispersity index was 0.14 and 0.21, and the zeta potential was about - 22.6 and - 16.4 mV for PTX-NCs and HPßCD-PTX-NCs, respectively. Additionally, the PXRD, FTIR, and DSC profiles can be explained by the NCs' integrity and coat formation. The SEM images showed that both PTX-NCs and HPßCD-PTX-NCs have rod-like structures. Moreover, HPßCD-PTX-NCs had significantly superior in vitro release than both PTX-NCs and PTX. Interestingly, the hemolytic assay showed that HPßCD-PTX-NCs had a more efficient and safer profile than PTX-NCs. This study emphasized that HPßCD could be an interesting candidate for the surface modification of PTX-NCs providing superior properties such as release and safety profiles.

Nanoparticle-Mediated Cytoplasmic Delivery of Messenger RNA Vaccines: Challenges and Future Perspectives.

The COVID-19 pandemic has left scientists and clinicians no choice but a race to find solutions to save lives while controlling the rapid spreading. Messenger RNA (mRNA)-based vaccines have become the front-runners because of their safety profiles, precise and reproducible immune response with more cost-effective and faster production than other types of vaccines. However, the physicochemical properties of naked mRNA necessitate innovative delivery technologies to ferry these 'messengers' to ribosomes inside cells by crossing various barriers and subsequently induce an immune response. Intracellular delivery followed by endosomal escape represents the key strategies for cytoplasmic delivery of mRNA vaccines to the target. This Perspective provides insights into how state-of-the-art nanotechnology helps break the delivery barriers and advance the development of mRNA vaccines. The challenges remaining and future perspectives are outlined.

Multiphysics Modeling and Simulation of Subcutaneous Injection and Absorption of Biotherapeutics: Sensitivity Analysis.

PURPOSE: A multiphysics simulation model was recently developed to capture major physical and mechanical processes of local drug transport and absorption kinetics of subcutaneously injected monoclonal antibody (mAb) solutions. To further explore the impact of individual drug attributes and tissue characteristics on the tissue biomechanical response and drug mass transport upon injection, sensitivity analysis was conducted and reported. METHOD: Various configurations of injection conditions, drug-associated attributes, and tissue properties were simulated with the developed multiphysics model. Simulation results were examined with regard to tissue deformation, porosity change, and spatiotemporal distributions of pressure, interstitial fluid flow, and drug concentration in the tissue. RESULTS: Injection conditions and tissue properties were found influential on the mechanical response of tissue and interstitial fluid velocity to various extents, leading to distinct drug concentration profiles. Intrinsic tissue porosity, lymphatic vessel density, and drug permeability through the lymphatic membrane were particularly essential in determining the local absorption rate of an mAb injection. CONCLUSION: The sensitivity analysis study may shed light on the product development of an mAb formulation, as well as on the future development of the simulation method.

Multiphysics Modeling and Simulation of Subcutaneous Injection and Absorption of Biotherapeutics: Model Development.

PURPOSE: Many monoclonal antibodies (mAbs) are administered via subcutaneous (SC) injection. Local transport and absorption kinetics and mechanisms, however, remain poorly understood. A multiphysics computational model was developed to simulate the injection and absorption processes of a protein solution in the SC tissue. METHODS: Quantitative relationships among tissue properties and transport behaviors of an injected solution were described by respective physical laws. SC tissue was treated as a 3-dimensional homogenous, poroelastic medium, in which vasculatures and lymphatic vessels were implicitly treated. Tissue deformation was considered, and interstitial fluid flow was modeled by Darcy's law. Transport of the drug mass was described based on diffusion and advection, which was integrated with tissue mechanics and interstitial fluid dynamics. RESULTS: Injection and absorption of albumin and IgG solutions were simulated. Upon injection, a sharp rise in tissue pressure, porosity, and fluid velocity could be observed at the injection tip. Largest tissue deformation appeared at the model surface. Transport of drug mass out of the injection zone was minimal. Absorption by local lymphatics was found to last several weeks. CONCLUSIONS: A bottom-up method was developed to simulate drug transport and absorption of protein solutions in skin tissue base on physical principles. The results appear to match experimental observations.

Preferential Oxycodone Loss of Physically Manipulated Abuse Deterrent Oxycodone HCl Extended Release Tablets Prepared for Nasal Insufflation Studies.

A method to reproducibly mill abuse deterrent oxycodone hydrochloride (HCl) extended release (ER) tablets was developed for a nasal insufflation pharmacokinetic (PK) study. Several comminution methods were explored before determining that a conical mill resulted in controlled milling of tablets to a size range equal to or below 1000 µm. However, milling resulted in significant loss of oxycodone from abuse deterrent oxycodone HCl ER tablets compared to minimal oxycodone loss from oxycodone HCl immediate release (IR) tablets. Characterization of milled tablet powder showed that loss of oxycodone was not attributed to analytical procedures or oxycodone phase change during high intensity milling processes. The content uniformity of oxycodone in the milled tablet powder varied when ER and IR tablets were milled to a particle size distribution equal to or below 500 µm but did not vary when particles were sized above 500 µm to equal to or below 1000 µm. In addition, the initial excipient weight to drug substance weight ratio impacted the amount of oxycodone lost from the respective formulation. However, dissolution demonstrated that when oxycodone HCl ER tablets are milled, differences in excipient weight to drug substance weight ratio and particle size distribution of milled tablets did not result in significantly different release of oxycodone.

Exploring Molecular Speciation and Crystallization Mechanism of Amorphous 2-Phenylamino Nicotinic Acid.

PURPOSE: Molecular understanding of phase stability and transition of the amorphous state helps in formulation and manufacturing of poorly-soluble drugs. Crystallization of a model compound, 2-phenylamino nicotinic acid (2PNA), from the amorphous state was studied using solid-state analytical methods. Our previous report suggests that 2PNA molecules mainly develop intermolecular -COOH∙∙∙pyridine N (acid-pyridine) interactions in the amorphous state. In the current study, the molecular speciation is explored with regard to the phase transition from the amorphous to the crystalline state. METHODS: Using spectroscopic techniques, the molecular interactions and structural evolvement during the recrystallization from the glassy state were investigated. RESULTS: The results unveiled that the structurally heterogeneous amorphous state contains acid-pyridine aggregates - either as hydrogen-bonded neutral molecules or as zwitterions - as well as a population of carboxylic acid dimers. Phase transition from the amorphous state results in crystal structures composed of carboxylic acid dimer (acid-acid) synthon or acid-pyridine chains depending on the crystallization conditions employed. CONCLUSIONS: The study underlines the structural evolvement, as well as its impact on the metastability, of amorphous samples from local, supramolecular assemblies to long-range intermolecular ordering through crystallization.

Solid-State Characterization of Three Polymorphs of an Orally Available Analog of Diethylenetriaminepentaacetic Acid.

The present work investigated the physical and thermal characteristics of three polymorphic forms (namely, PF1, PF2, and PF3) of a diethyl ester analog of diethylenetriaminepentaacetic acid (C2E2) produced under varying conditions. The identity of each form of C2E2 was confirmed by 1H-NMR, 13C-NMR, and mass spectroscopy. The different polymorphic forms exhibited solubilities ranging from 40 to 150 mg/mL. Powder X-ray diffraction (PXRD) and electron microscopy confirmed that all three forms were crystalline, two of which being scaly, and the third being well-formed. Infrared and Raman spectroscopy revealed differences in the C = O bonding region while differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) showed widely different melting points with only one thermal event for each compound. The comparison of the melting points and heats of fusion show that the PF1 is monotropically related to both PF2 and PF3, while PF2 and PF3 are enantropically related. Our finding indicates that PF3 is the thermodynamically stable polymorph and will be used for in vitro and in vivo experiments.

Receptor-independent, direct membrane binding leads to cell-surface lipid sorting and Syk kinase activation in dendritic cells.

Binding of particulate antigens by antigen-presenting cells is a critical step in immune activation. Previously, we demonstrated that uric acid crystals are potent adjuvants, initiating a robust adaptive immune response. However, the mechanisms of activation are unknown. By using atomic force microscopy as a tool for real-time single-cell activation analysis, we report that uric acid crystals could directly engage cellular membranes, particularly the cholesterol components, with a force substantially stronger than protein-based cellular contacts. Binding of particulate substances activated Syk kinase-dependent signaling in dendritic cells. These observations suggest a mechanism whereby immune cell activation can be triggered by solid structures via membrane lipid alteration without the requirement for specific cell-surface receptors, and a testable hypothesis for crystal-associated arthropathies, inflammation, and adjuvanticity.

Impact of Supramolecular Aggregation on the Crystallization Kinetics of Organic Compounds from the Supercooled Liquid State.

Despite numerous challenges in their theoretical description and practical implementation, amorphous drugs are of growing importance to the pharmaceutical industry. One such challenge is to gain molecular level understanding of the propensity of a molecule to form and remain as a glassy solid. In this study, a series of structurally similar diarylamine compounds was examined to elucidate the role of supramolecular aggregation on crystallization kinetics from supercooled liquid state. The structural similarity of the compounds makes it easier to isolate the molecular features that affect crystallization kinetics and glass forming ability of these compounds. To examine the role of hydrogen-bonded aggregation and motifs on crystallization kinetics, a combination of thermal and spectroscopic techniques was employed. Using variable temperature FTIR, Raman, and solid-state NMR spectroscopies, the presence of hydrogen bonding in the melt and glassy state was examined and correlated with observed phase transition behaviors. Spectroscopic results revealed that the formation of hydrogen-bonded aggregates involving carboxylic acid and pyridine nitrogen (acid-pyridine aggregates) between neighboring molecules in the melt state impedes crystallization, while the presence of carboxylic acid dimers (acid-acid dimers) in the melt favors crystallization. This study suggests that glass formation of small molecules is influenced by the type of intermolecular interactions present in the melt state and the kinetics associated with the molecules to assemble into a crystalline lattice. For the compounds that form acid-pyridine aggregates, the formation of energy degenerate chains, produced due to conformational flexibility of the molecules, presents a kinetic barrier to crystallization. The poor crystallization tendency of these aggregates stems from the highly directional hydrogen-bonding interactions needed to form the acid-pyridine chains. Conversely, for the compounds that form acid-acid dimers, the nondirectional van der Waals forces needed to construct a nucleus promote rapid assembly and crystallization.

Pulmonary delivery of nanoparticle chemotherapy for the treatment of lung cancers: challenges and opportunities.

Lung cancer is the second most prevalent and the deadliest among all cancer types. Chemotherapy is recommended for lung cancers to control tumor growth and to prolong patient survival. Systemic chemotherapy typically has very limited efficacy as well as severe systemic adverse effects, which are often attributed to the distribution of anticancer drugs to non-targeted sites. In contrast, inhalation routes permit the delivery of drugs directly to the lungs providing high local concentrations that may enhance the anti-tumor effect while alleviating systemic adverse effects. Preliminary studies in animals and humans have suggested that most inhaled chemotherapies are tolerable with manageable pulmonary adverse effects, including cough and bronchospasm. Promoting the deposition of anticancer drugs in tumorous cells and minimizing access to healthy lung cells can further augment the efficacy and reduce the risk of local toxicities caused by inhaled chemotherapy. Sustained release and tumor localization characteristics make nanoparticle formulations a promising candidate for the inhaled delivery of chemotherapeutic agents against lung cancers. However, the physiology of respiratory tracts and lung clearance mechanisms present key barriers for the effective deposition and retention of inhaled nanoparticle formulations in the lungs. Recent research has focused on the development of novel formulations to maximize lung deposition and to minimize pulmonary clearance of inhaled nanoparticles. This article systematically reviews the challenges and opportunities for the pulmonary delivery of nanoparticle formulations for the treatment of lung cancers.

Solid-State Spectroscopic Investigation of Molecular Interactions between Clofazimine and Hypromellose Phthalate in Amorphous Solid Dispersions.

It has been technically challenging to specify the detailed molecular interactions and binding motif between drugs and polymeric inhibitors in the solid state. To further investigate drug-polymer interactions from a molecular perspective, a solid dispersion of clofazimine (CLF) and hypromellose phthalate (HPMCP), with reported superior amorphous drug loading capacity and physical stability, was selected as a model system. The CLF-HPMCP interactions in solid dispersions were investigated by various solid state spectroscopic methods including ultraviolet-visible (UV-vis), infrared (IR), and solid-state NMR (ssNMR) spectroscopy. Significant spectral changes suggest that protonated CLF is ionically bonded to the carboxylate from the phthalyl substituents of HPMCP. In addition, multivariate analysis of spectra was applied to optimize the concentration of polymeric inhibitor used to formulate the amorphous solid dispersions. Most interestingly, proton transfer between CLF and carboxylic acid was experimentally investigated from 2D 1H-1H homonuclear double quantum NMR spectra by utilizing the ultrafast magic-angle spinning (MAS) technique. The molecular interaction pattern and the critical bonding structure in CLF-HPMCP dispersions were further delineated by successfully correlating ssNMR findings with quantum chemistry calculations. These high-resolution investigations provide critical structural information on active pharmaceutical ingredient-polymer interaction, which can be useful for rational selection of appropriate polymeric carriers, which are effective crystallization inhibitors for amorphous drugs.

Investigating the Interaction Pattern and Structural Elements of a Drug-Polymer Complex at the Molecular Level.

Strong associations between drug and polymeric carriers are expected to contribute to higher drug loading capacities and better physical stability of amorphous solid dispersions. However, molecular details of the interaction patterns and underlying mechanisms are still unclear. In the present study, a series of amorphous solid dispersions of clofazimine (CLF), an antileprosy drug, were prepared with different polymers by applying the solvent evaporation method. When using hypromellose phthalate (HPMCP) as the carrier, the amorphous solid dispersion system exhibits not only superior drug loading capacity (63% w/w) but also color change due to strong drug-polymer association. In order to further explain these experimental observations, the interaction between CLF and HPMCP was investigated in a nonpolar volatile solvent system (chloroform) prior to forming the solid dispersion. We observed significant UV/vis and (1)H NMR spectral changes suggesting the protonation of CLF and formation of ion pairs between CLF and HPMCP in chloroform. Furthermore, nuclear Overhauser effect spectroscopy (NOESY) and diffusion order spectroscopy (DOSY) were employed to evaluate the strength of associations between drug and polymers, as well as the molecular mobility of CLF. Finally, by correlating the experimental values with quantum chemistry calculations, we demonstrate that the protonated CLF is binding to the carboxylate group of HPMCP as an ion pair and propose a possible structural model of the drug-polymer complex. Understanding the drug and carrier interaction patterns from a molecular perspective is critical for the rational design of new amorphous solid dispersions.