Analysis of amorphous solid dispersions using 2D solid-state NMR and (1)H T(1) relaxation measurements

From formulation to structure: 3D electron diffraction for the structure solution of a new indomethacin polymorph from an amorphous solid dispersion

3D electron diffraction (3DED) is increasingly employed to determine molecular and crystal structures from micro-crystals. Indomethacin is a well known, marketed, small-molecule non-steroidal anti-inflammatory drug with eight known polymorphic forms, of which four structures have been elucidated to date. Using 3DED, we determined the structure of a new ninth polymorph, σ, found within an amorphous solid dispersion, a product formulation sometimes used for active pharmaceutical ingredients with poor aqueous solubility. Subsequently, we found that σ indomethacin can be produced from direct solvent evaporation using dichloromethane. These results demonstrate the relevance of 3DED within drug development to directly probe product formulations.

Exploring the influence of hydrogen bond donor groups on the microstructure and intermolecular interactions of amorphous solid dispersions containing diflunisal structural analogues

Drug-polymer intermolecular interactions, and H-bonds specifically, play an important role in the stabilization process of a compound in an amorphous solid dispersion (ASD). However, it is still difficult to predict whether or not interactions will form and what the strength of those interactions would be, based on the structure of drug and polymer. Therefore, in this study, structural analogues of diflunisal (DIF) were synthesized and incorporated in ASDs with poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA) as a stabilizing polymer. The respective DIF derivatives contained different types and numbers of H-bond donor groups, which allowed to assess the influence of these structural differences on the phase behavior and the actual interactions formed in the ASDs. The highest possible drug loading of these derivatives in PVPVA were evaluated through film casting. Subsequently, a lower drug loading of each compound was spray dried. These spray dried ASDs were subjected to an in-depth solid-state nuclear magnetic resonance (ssNMR) study, including 1D spectroscopy and relaxometry, as well as 2D dipolar HETCOR experiments. The drug loading study revealed the highest possible loading of 50 wt% for the native DIF in PVPVA. The methoxy DIF derivative reached the second highest drug loading of 35 wt%, while methylation of the carboxyl group of DIF led to a sharp decrease in the maximum loading, to around 10 wt% only. Unexpectedly, the maximum loading increased again when both the COOH and OH groups of diflunisal were methylated in the dimethyl DIF derivative, to around 30 wt%. The ssNMR study on the spray dried ASD samples confirmed intermolecular H-bonding with PVPVA for native DIF and methoxy DIF. Studies of the proton relaxation decay times and 2D 1H-13C dipolar HETCOR experiments indicated that the ASDs with native DIF and methoxy DIF were homogenously mixed, while the ASDs containing DIF methyl ester and dimethyl DIF were phase separated at the nm level. It was established that, for these systems, the availability of the carboxyl group was imperative in the formation of intermolecular H-bonds with PVPVA and in the generation of homogenously mixed ASDs.

Predicting the Stability of Formulations Containing Lyophilized Human Serum Albumin and Sucrose/Trehalose Using Solid-State NMR Spectroscopy

Stabilization of proteins by disaccharides in lyophilized formulations depends on the interactions between the protein and the disaccharide (system homogeneity) and the sufficiently low mobility of the system. Human serum albumin (HSA) was lyophilized with disaccharides (sucrose and/or trehalose) in different relative concentrations. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy 1H T1 and 1H T1ρ relaxation times were measured to determine the homogeneity of the lyophilized systems on 20-50 and 1-3 nm domains, respectively, with 1H T1 relaxation times also being used to determine the β-relaxation rate. HSA/sucrose systems had longer 1H T1 relaxation times and were slightly more stable than HSA/trehalose systems in almost all cases shown. HSA/sucrose/trehalose systems have 1H T1 relaxation times between the HSA/sucrose and HSA/trehalose systems and did not result in a more stable system compared with binary systems. Inhomogeneity was evident in a sample containing relative concentrations of 10% HSA and 90% trehalose, suggesting trehalose crystallization during lyophilization. Under these stability conditions and with these ssNMR acquisition parameters, a 1H T1 relaxation time below 1.5 s correlated with an unstable sample, regardless of the disaccharide(s) used.

Probing the Molecular and Macroscopic Structure of Solid Solutions by Dynamic Nuclear Polarization (DNP) Enhanced 13C and 15N Solid-State NMR Spectroscopy

Crystallization is a widely used purification technique in the manufacture of active pharmaceutical ingredients (APIs) and precursor molecules. However, when impurities and desired compounds have similar molecular structures, separation by crystallization may become challenging. In such cases, some impurities may form crystalline solid solutions with the desired product during recrystallization. Understanding the molecular structure of these recrystallized solid solutions is crucial to devise methods for effective purification. Unfortunately, there are limited analytical techniques that provide insights into the molecular structure or spatial distribution of impurities that are incorporated within recrystallized products. In this study, we investigated model solid solutions formed by recrystallizing salicylic acid (SA) in the presence of anthranilic acid (AA). These two molecules are known to form crystalline solid solutions due to their similar molecular structures. To overcome challenges associated with the long 1H longitudinal relaxation times (T1(1H)) of SA and AA, we employed dynamic nuclear polarization (DNP) and 15N isotope enrichment to enable solid-state NMR experiments. Results of solid-state NMR experiments and DFT calculations revealed that SA and AA are homogeneously alloyed as a solid solution. Heteronuclear correlation (HETCOR) experiments and plane-wave DFT structural models provide further evidence of the molecular-level interactions between SA and AA. This research provides valuable insights into the molecular structure of recrystallized solid solutions, contributing to the development of effective purification strategies and an understanding of the physicochemical properties of solid solutions.

Structural Features of the Glassy State and Their Impact on the Solid-State Properties of Organic Molecules in Pharmaceutical Systems

This paper reviews the structure and properties of amorphous active pharmaceutical ingredients (APIs), including small molecules and proteins, in the glassy state (below the glass transition temperature, Tg). Amorphous materials in the neat state and formulated with excipients as miscible amorphous mixtures are included, and the role of absorbed water in affecting glass structure and stability has also been considered. We defined the term "structure" to indicate the way the various molecules in a glass interact with each other and form distinctive molecular arrangements as regions or domains of varying number of molecules, molecular packing, and density. Evidence is presented to suggest that such systems generally exist as heterogeneous structures made up of high-density domains surrounded by a lower density arrangement of molecules, termed the microstructure. It has been shown that the method of preparation and the time frame for handling and storage can give rise to variable glass structures and varying physical properties. Throughout this paper, examples are given of theoretical, computer simulation, and experimental studies which focus on the nature of intermolecular interactions, the size of heterogeneous higher density domains, and the impact of such systems on the relative physical and chemical stability of pharmaceutical systems.

Predicting the Stability of Lyophilized Human Serum Albumin Formulations Containing Sucrose and Trehalose Using Solid-State NMR Spectroscopy: Effect of Storage Temperature on 1H T1 Relaxation Times

In a lyophilized protein/disaccharide system, the ability of the disaccharide to form a homogeneous mixture with the protein and to slow the protein mobility dictates the stabilization potential of the formulation. Human serum albumin was lyophilized with sucrose or trehalose in histidine, phosphate, or citrate buffer. 1H T1 relaxation times were measured by solid-state NMR spectroscopy and were used to assess the homogeneity and mobility of the samples after zero, six, and twelve months at different temperatures. The mobility of the samples decreased after 6 and 12 months storage at elevated temperatures, consistent with structural relaxation of the amorphous disaccharide matrix. Formulations with sucrose had lower mobility and greater stability than formulations with trehalose.

Development of Ternary Amorphous Solid Dispersions Manufactured by Hot-Melt Extrusion and Spray-Drying─Comparison of In Vitro and In Vivo Performance

Producing amorphous solid dispersions (ASDs) by hot-melt extrusion (HME) is favorable from an economic and ecological perspective but also limited to thermostable active pharmaceutical ingredients (APIs). A potential technology shift from spray-drying to hot-melt extrusion at later stages of drug product development is a desirable goal, however bearing the risk of insufficient comparability of the in vitro and in vivo performance of the final dosage form. Hot-melt extrusion was performed using API/polymer/surfactant mixtures with hydroxypropyl methylcellulose acetate succinate (HPMCAS) as the polymer and evaluated regarding the extrudability of binary and ternary amorphous solid dispersions (ASDs). Additionally, spray-dried ASDs were produced, and solid-state properties were compared to the melt-extruded ASDs. Tablets were manufactured of a ternary ASD lead candidate comparing their in vitro dissolution and in vivo performance. The extrudability of HPMCAS was improved by adding a surfactant as plasticizer, thereby lowering the high melt-viscosity. d-α-Tocopheryl polyethylene glycol succinate (TPGS) as surfactant showed the most similar solid-state properties between spray-dried and extruded ASDs compared to those of poloxamer 188 and sodium dodecyl sulfate. The addition of TPGS, however, barely affected API/polymer interactions. The in vitro dissolution experiment and in vivo dog study revealed a higher drug release of tablets manufactured from the spray-dried ASD compared to the melt-extruded ASD; this was attributed to the different particle size. We could further demonstrate that the drug release can be controlled by adjusting the particle size of melt-extruded ASDs leading to a similar release profile compared to tablets containing the spray-dried dispersion, which confirmed the feasibility of a technology shift from spray-drying to HME upon drug product development.

Advancing Drug Delivery Paradigms: Polyvinyl Pyrolidone (PVP)-Based Amorphous Solid Dispersion for Enhanced Physicochemical Properties and Therapeutic Efficacy

BACKGROUND

The current challenge in drug development lies in addressing the physicochemical issues that lead to low drug effectiveness. Solubility, a crucial physicochemical parameter, greatly influences various biopharmaceutical aspects of a drug, including dissolution rate, absorption, and bioavailability. Amorphous solid dispersion (ASD) has emerged as a widely explored approach to enhance drug solubility.

OBJECTIVE

The objective of this review is to discuss and summarize the development of polyvinylpyrrolidone (PVP)-based amorphous solid dispersion in improving the physicochemical properties of drugs, with a focus on the use of PVP as a novel approach.

METHODOLOGY

This review was conducted by examining relevant journals obtained from databases such as Scopus, PubMed, and Google Scholar, since 2018. The inclusion and exclusion criteria were applied to select suitable articles.

RESULTS

This study demonstrated the versatility and efficacy of PVP in enhancing the solubility and bioavailability of poorly soluble drugs. Diverse preparation methods, including solvent evaporation, melt quenching, electrospinning, coprecipitation, and ball milling are discussed for the production of ASDs with tailored characteristics.

CONCLUSION

PVP-based ASDs could offer significant advantages in the formulation strategies, stability, and performance of poorly soluble drugs to enhance their overall bioavailability. The diverse methodologies and findings presented in this review will pave the way for further advancements in the development of effective and tailored amorphous solid dispersions.

Polymer-inducing chemical degradation of amorphous solid dispersions driven by drug-polymer interactions for physical stabilization

Intermolecular interactions between active pharmaceutical ingredients (APIs) and carrier polymers are important for the long-term physical stability of amorphous solid dispersions (ASDs). However, the negative impact of intermolecular interactions on chemical stability has rarely been reported. In this study, the relationship between intermolecular interactions and physical and chemical stability was investigated using two ASDs composed of API and hydroxypropyl methylcellulose acetate succinate (HPMCAS) with different stabilities: ASD1 was physically stable but chemically unstable, whereas ASD2 was physically unstable but chemically stable. Ionic-bonding between the pyridine nitrogen in the API and succinyl group in HPMCAS was found in both ASDs. The additional interaction between the succinyl group in HPMCAS and the hydroxyl group in the API was suggested only in ASD1. It was concluded that the additional interaction contributed to the physical stability of ASD1; however, it accelerated the chemical reaction between the succinyl and hydroxyl groups to generate succinyl ester owing to its close proximity. This study shows that the intermolecular interaction between the API and carrier polymer is not always beneficial for chemical stability. Understanding the molecular states of APIs and polymers in ASDs is important for their successful development.

Exploiting solid-state dynamic nuclear polarization NMR spectroscopy to establish the spatial distribution of polymorphic phases in a solid material

Solid-state DNP NMR can enhance the ability to detect minor amounts of solid phases within heterogenous materials. Here we demonstrate that NMR contrast based on the transport of DNP-enhanced polarization can be exploited in the challenging case of early detection of a small amount of a minor polymorphic phase within a major polymorph, and we show that this approach can yield quantitative information on the spatial distribution of the two polymorphs. We focus on the detection of a minor amount (<4%) of polymorph III of m-aminobenzoic acid within a powder sample of polymorph I at natural isotopic abundance. Based on proposed models of the spatial distribution of the two polymorphs, simulations of 1H spin diffusion allow NMR data to be calculated for each model as a function of particle size and the relative amounts of the polymorphs. A comparison between simulated and experimental NMR data allows the model(s) best representing the spatial distribution of the polymorphs in the system to be established.

Considerations in the Development of Physically Stable High Drug Load API- Polymer Amorphous Solid Dispersions in the Glassy State

In this Commentary, the authors expand on their earlier studies of the solid-state long-term isothermal crystallization of amorphous API from the glassy state in amorphous solid dispersions, and focus on the effects of polymer concentration, and its implications for producing high load API doses with minimum polymer concentration. After presenting an overview of the various mechanistic factors which influence the ability of polymers to inhibit API crystallization, including the chemical structure of the polymer relative to the API, the nature and strength of API-polymer noncovalent interactions, polymer molecular weight, impact on primary diffusive molecular mobility, as well as on secondary motions in the bulk and surface phases of the glass, we consider in more detail, the effects of polymer concentration. Here, we examine the factors that appear to allow relatively low polymer concentrations, i.e., less than 10%w/w polymer, to greatly reduce crystallization, including a focus on the heterogeneous structure of the glassy state, and the possible spatial distribution and concentration of polymer in certain key regions of the glass. This is followed by a review and analysis of examples in the recent literature focused on determining the minimum polymer concentration in an amorphous solid dispersion, capable of producing optimally stable high drug load amorphous dispersions.

Non-Covalent Reactions Supporting Antiviral Development

Viruses are the current big enemy of the world's healthcare systems. As the small infector causes various deadly diseases, from influenza and HIV to COVID-19, the virus continues to evolve from one type to its mutants. Therefore, the development of antivirals demands tremendous attention and resources for drug researchers around the world. Active pharmaceutical ingredients (API) development includes discovering new drug compounds and developing existing ones. However, to innovate a new antiviral takes a very long time to test its safety and effectiveness, from structure modeling to synthesis, and then requires various stages of clinical trials. Meanwhile, developing the existing API can be more efficient because it reduces many development stages. One approach in this effort is to modify the solid structures to improve their physicochemical properties and enhance their activity. This review discusses antiviral multicomponent systems under the research phase and has been marketed. The discussion includes the types of antivirals, their counterpart compound, screening, manufacturing methods, multicomponent systems yielded, characterization methods, physicochemical properties, and their effects on their pharmacological activities. It is hoped that the opportunities and challenges of solid antiviral drug modifications can be drawn in this review as important information for further antiviral development.

New Development in Understanding Drug-Polymer Interactions in Pharmaceutical Amorphous Solid Dispersions from Solid-State Nuclear Magnetic Resonance

Pharmaceutical amorphous solid dispersions (ASDs) represent a widely used technology to increase the bioavailability of active pharmaceutical ingredients (APIs). ASDs are based on an amorphous API dispersed in a polymer, and their stability is driven by the presence of strong intermolecular interactions between these two species (e.g., hydrogen bond, electrostatic interactions, etc.). The understanding of these interactions at the atomic level is therefore crucial, and solid-state nuclear magnetic resonance (NMR) has demonstrated itself as a very powerful technique for probing API-polymer interactions. Other reviews have also reported exciting approaches to study the structures and dynamic properties of ASDs and largely focused on the study of API-polymer miscibility and on the identification of API-polymer interactions. Considering the increased use of NMR in the field, the aim of this Review is to specifically highlight recent experimental strategies used to identify API-polymer interactions and report promising recent examples using one-dimensional (1D) and two-dimensional (2D) experiments by exploiting the following emerging approaches of very-high magnetic field and ultrafast magic angle spinning (MAS). A range of different ASDs spanning APIs and polymers with varied structural motifs is targeted to illustrate new ways to understand the mechanism of stability of ASDs to enable the design of new dispersions.

19F Solid-state NMR characterization of pharmaceutical solids

Solid-state NMR has been increasingly recognized as a high-resolution and versatile spectroscopic tool to characterize drug substances and products. However, the analysis of pharmaceutical materials is often carried out at natural isotopic abundance and a relatively low drug loading in multi-component systems and therefore suffers from challenges of low sensitivity. The fact that fluorinated therapeutics are well represented in pipeline drugs and commercial products offers an excellent opportunity to utilize fluorine as a molecular probe for pharmaceutical analysis. We aim to review recent advancements of ¹⁹F magic angle spinning NMR methods in modern drug research and development. Applications to polymorph screening at the micromolar level, structural elucidation, and investigation of molecular interactions at the Ångström to submicron resolution in drug delivery, stability, and quality will be discussed.

Active coating of immediate-release evogliptin tartrate to prepare fixed dose combination tablet with sustained-release metformin HCl

This study was aimed to develop a fixed dose combination (FDC) tablet containing a low dose of evogliptin tartrate (6.87 mg) for immediate release combined with a high dose (1000 mg) of sustained-release (SR) metformin HCl appropriate for once daily dosing the treatment of type 2 diabetes. To prepare the FDC tablets, an active coating was used in this study, whereby evogliptin tartrate film was layered on a matrix core tablet containing metformin HCl. To overcome the problem caused by a low-dose drug in combination with a relatively large matrix tablet containing high-dose drug, it was also aimed to confirm the formulation and coating operation for satisfactory content uniformity, and to describe the chemical stability during storage of the amorphous active coating layer formulation in relation to molecular mobility. Furthermore, the in vitro release and in vivo pharmacokinetic profiles of metformin HCl and evogliptin tartrate in the FDC active coating tablet were compared to those of the commercially marketed reference drugs, Diabex XR® (Daewoong, Seoul, Korea) containing metformin HCl and Suganon® (Donga ST, Seoul, Korea) containing evogliptin tartrate. In conclusion, the newly developed FDC active coating tablet in this study was confirmed to be bioequivalent to the reference marketed products in beagle dogs, with satisfactory content uniformity and stability.

Detecting Crystallinity Using Terahertz Spectroscopy in 3D Printed Amorphous Solid Dispersions

This study demonstrates the applicability of terahertz time-domain spectroscopy (THz-TDS) in evaluating the solid-state of the drug in selective laser sintering-based 3D printed dosage forms. Selective laser sintering is a powder bed-based 3D printing platform, which has recently demonstrated applicability in manufacturing amorphous solid dispersions (ASDs) through a layer-by-layer fusion process. When formulating ASDs, it is critical to confirm the final solid state of the drug as residual crystallinity can alter the performance of the formulation. Moreover, SLS 3D printing does not involve the mixing of the components during the process, which can lead to partially amorphous systems causing reproducibility and storage stability problems along with possibilities of unwanted polymorphism. In this study, a previously investigated SLS 3D printed ASD was characterized using THz-TDS and compared with traditionally used solid-state characterization techniques, including differential scanning calorimetry (DSC) and powder X-ray diffractometry (pXRD). THz-TDS provided deeper insights into the solid state of the dosage forms and their properties. Moreover, THz-TDS was able to detect residual crystallinity in granules prepared using twin-screw granulation for the 3D printing process, which was undetectable by the DSC and XRD. THz-TDS can prove to be a useful tool in gaining deeper insights into the solid-state properties and further aid in predicting the stability of amorphous solid dispersions.

The Physical Stability of Felodipine and Its Recrystallization from an Amorphous Solid Dispersion Studied by NMR Relaxometry

The ¹H nuclear magnetic resonance (NMR) relaxometry method was applied to investigate the physical stability of an active pharmaceutical ingredient (API) and, for the first time, its recrystallization process in an amorphous solid dispersion system (ASD). The ASD of felodipine and polyvinylpyrrolidone (PVP) was prepared using the solvent evaporation method in a mass ratio of 50:50. In the first stage of the study (250 days), the sample was stored at 0% relative humidity (RH). The recovery of magnetization was described by one-exponential function. In the second stage (300 days in 75% relative humidity), the recrystallization process of felodipine was studied, showing in the sample three components of equilibrium magnetization related to (i) crystalline felodipine, (ii) water, and (iii) felodipine and PVP remaining in the ASD. The study shows that the ¹H NMR relaxometry method is a very useful tool for analysing the composition of a three-phase system mixed at the molecular level and for the investigation of recrystallization process of API in amorphous solid dispersion system.

Industry White Paper: Contemporary Opportunities and Challenges in Characterizing Crystallinity in Amorphous Solid Dispersions

Members of the IQ Consortium ″Working Group on Characterization on Amorphous Solid Dispersions″ shares here a perspective on the analytical challenges, and limitations of detecting low levels of crystalline drug substance in amorphous solid dispersions (ASDs) and associated drug products. These companies aim to employ highly sensitive commercially available analytical technologies to guide development, support control strategies, and enable registration of quality products. We hope to promote consistency in development and registration approaches and guide the industry in development of "characterization best practices" in the interest of providing high quality products for patients. The first half of this perspective highlights the unique challenges of analytical methodologies to monitor crystalline drug substance in ASDs and their associated drug products. Challenges around use of limit tests, analyte spiking experiments, and method robustness are also underscored. The latter half describes the merits and limitations of the diverse analytical "toolbox" (such as XRPD, NIR and DSC), which can be readily applied during development and, in some cases, considered for potential application and validation in the commercial QC setting when necessary.

Drug crystal growth in ternary amorphous solid dispersions: Effect of surfactants and polymeric matrix-carriers

The present study evaluates the crystal growth rate of amorphous drugs when dispersed in different ternary polymeric amorphous solid dispersions (ASDs) in the presence of surfactants. Specifically, ternary ASDs of aprepitant (APT, selected as a model drug) were prepared via melt-quench cooling by evaluating three commonly used ASDs matrix/carriers, namely hydroxypropyl cellulose (HPC), poly(vinylpyrrolidone) (PVP) and the copolymer Soluplus® (SOL), and two suitable surfactants, namely d-alpha tocopheryl polyethylene glycol 1000 succinate (TPGS) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P407). Results showed that all components were completely miscible (verified via hot stage polarized microscopy) and both surfactants were acting as plasticizers to the API. APT's crystal growth rate was increased in the presence of both P407 and TPGS, while PVP was identified as the matrix/carrier with the greatest impact API's crystal growth rate inhibition. Interestingly, TPGS presented a noticeable synergistic effect when combined with PVP resulting in a further reduction of APT's crystal growth rate. Furthermore, evaluation of APT's nucleation induction time in dissolution medium (PBS pH 6.8) revealed PVP as the most effective crystallization inhibitor, whereas the addition of TPGS showed to improve PVP's ability to inhibit APT's recrystallization. Finally, the formation of intermolecular interactions in the ternary APT-PVP-TPGS provided an explanation for the observed PVP-TPGS synergistic effects, with molecular dynamics simulations being able to unravel the type and extent of these interactions on a theoretical basis.

Variable-Temperature NMR Analysis of the Thermodynamics of Polymer Partitioning between Aqueous and Drug-Rich Phases and Its Significance for Amorphous Formulations

We previously reported that the polymers used in amorphous solid dispersion (ASD) formulations, such as polyvinylpyrrolidone (PVP), polyvinylpyrrolidone/vinyl acetate (PVP-VA), and hypromellose (HPMC), distribute into the drug-rich phase of ibuprofen (IBP) formed by liquid-liquid phase separation, resulting in a reduction in the maximum drug supersaturation in the aqueous phase. Herein, the mechanism underlying the partitioning of the polymer into the drug-rich phase was investigated from a thermodynamic perspective. The dissolved IBP concentration in the aqueous phase and the amount of polymer distributed into the IBP-rich phase were quantitatively analyzed in IBP-supersaturated solutions containing different polymers using variable-temperature solution-state nuclear magnetic resonance (NMR) spectroscopy. The polymer weight ratio in the IBP-rich phase increased at higher temperatures, leading to a more notable reduction of IBP amorphous solubility. Among the polymers, the amorphous solubility reduction was the greatest for the PVP-VA solution at lower temperatures, while HPMC reduced the amorphous solubility to the greatest extent at higher temperatures. The change in the order of polymer impact on the amorphous solubility resulted from the differences in the temperature dependency of polymer partitioning. The van't Hoff plot of the polymer partition coefficient revealed that both enthalpy and entropy changes for polymer transfer into the IBP-rich phase from the aqueous phase (ΔH_{aqueous→IBP-rich} and ΔS_{aqueous→IBP-rich}) gave positive values for most of the measured temperature range, indicating that polymer partitioning into the IBP-rich phase was an endothermic but entropically favorable process. The polymer transfer into the IBP-rich phase was more endothermic for HPMC than for PVP and PVP-VA. The solid-state NMR analysis of the IBP/polymer ASD implied that the newly formed IBP/polymer interactions in the IBP-rich phase upon polymer incorporation were weaker for HPMC, providing a rationale for the larger positive transfer enthalpy for HPMC. The change in Gibbs free energy for polymer transfer (ΔG_{aqueous→IBP-rich}) showed negative values across the experimental temperature range, decreasing with an increase in temperature, indicating that the distribution of the polymer into the IBP-rich phase is favored at higher temperatures. Moreover, ΔG_{aqueous→IBP-rich} for HPMC showed the greatest decrease with the temperature, likely reflecting the temperature-induced dehydration of HPMC in the aqueous phase. This study contributes fundamental insights into the phenomenon of polymer partitioning into drug-rich phases, furthering the understanding of achievable supersaturation levels and ultimately providing information on polymer selection for ASD formulations.

Drug-Polymer Interactions in Acetaminophen/Hydroxypropylmethylcellulose Acetyl Succinate Amorphous Solid Dispersions Revealed by Multidimensional Multinuclear Solid-State NMR Spectroscopy

The bioavailability of insoluble crystalline active pharmaceutical ingredients (APIs) can be enhanced by formulation as amorphous solid dispersions (ASDs). One of the key factors of ASD stabilization is the formation of drug-polymer interactions at the molecular level. Here, we used a range of multidimensional and multinuclear nuclear magnetic resonance (NMR) experiments to identify these interactions in amorphous acetaminophen (paracetamol)/hydroxypropylmethylcellulose acetyl succinate (HPMC-AS) ASDs at various drug loadings. At low drug loading (<20 wt %), we showed that 1H-13C through-space heteronuclear correlation experiments identify proximity between aromatic protons in acetaminophen with cellulose backbone protons in HPMC-AS. We also show that 14N-1H heteronuclear multiple quantum coherence (HMQC) experiments are a powerful approach in probing spatial interactions in amorphous materials and establish the presence of hydrogen bonds (H-bond) between the amide nitrogen of acetaminophen with the cellulose ring methyl protons in these ASDs. In contrast, at higher drug loading (40 wt %), no acetaminophen/HPMC-AS spatial proximity was identified and domains of recrystallization of amorphous acetaminophen into its crystalline form I, the most thermodynamically stable polymorph, and form II are identified. These results provide atomic scale understanding of the interactions in the acetaminophen/HPMC-AS ASD occurring via H-bond interactions.

What Are the Important Factors That Influence API Crystallization in Miscible Amorphous API-Excipient Mixtures during Long-Term Storage in the Glassy State?

In this Perspective, the authors examine the various factors that should be considered when attempting to use miscible amorphous API-excipient mixtures (amorphous solid dispersions and coamorphous systems) to prevent the solid-state crystallization of API molecules when isothermally stored for long periods of time (a year or more) in the glassy state. After presenting an overview of a variety of studies designed to obtain a better understanding of possible mechanisms by which amorphous API undergo physical instability and by which excipients generally appear to inhibit API crystallization from the amorphous state, we examined 78 studies that reported acceptable physical stability of such systems, stored below T_g under "dry" conditions for one year or more. These results were examined more closely in terms of two major contributing factors: the degree to which a reduction in diffusional molecular mobility and API-excipient molecular interactions operates to inhibit crystallization. These two parameters were chosen because the data are readily available in early development to help compare amorphous systems. Since T_g - T = 50 K is often used as a rule of thumb for the establishing the minimum value below T_g required to reduce diffusional mobility to a period of years, it was interesting to observe that 30 of the 78 studies still produced significant physical stability at values of T_g - T < 50 K (3-47 °C), suggesting that factors besides diffusive molecular mobility likely contribute. A closer look at the T_g - T < 50 systems shows that hydrogen bonding, proton transfer, disruption of API-API self-associations (such as dimers), and possible π-π stacking were reported for most of the systems. In contrast, five crystallized systems that were monitored for a year or more were also examined. These systems exhibited T_g - T values of 9-79, with three of them exhibiting T_g - T < 50. For these three samples, none displayed molecular interactions by infrared spectroscopy. A discussion on the impact of relative humidity on long-term crystallization in the glass was included, with attention paid to the relative water vapor sorption by various excipients and effects on diffusive mobility and molecular interactions between API and excipient.

Solid-State NMR Spectroscopy: A Key Tool to Unravel the Supramolecular Structure of Drug Delivery Systems

In the past decades, nanosized drug delivery systems (DDS) have been extensively developed and studied as a promising way to improve the performance of a drug and reduce its undesirable side effects. DDSs are usually very complex supramolecular assemblies made of a core that contains the active substance(s) and ensures a controlled release, which is surrounded by a corona that stabilizes the particles and ensures the delivery to the targeted cells. To optimize the design of engineered DDSs, it is essential to gain a comprehensive understanding of these core-shell assemblies at the atomic level. In this review, we illustrate how solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become an essential tool in DDS design.

Analytical and Computational Methods for the Determination of Drug-Polymer Solubility and Miscibility

In the pharmaceutical industry, poorly water-soluble drugs require enabling technologies to increase apparent solubility in the biological environment. Amorphous solid dispersion (ASD) has emerged as an attractive strategy that has been used to market more than 20 oral pharmaceutical products. The amorphous form is inherently unstable and exhibits phase separation and crystallization during shelf life storage. Polymers stabilize the amorphous drug by antiplasticization, reducing molecular mobility, reducing chemical potential of drug, and increasing glass transition temperature in ASD. Here, drug-polymer miscibility is an important contributor to the physical stability of ASDs. The current Review discusses the basics of drug-polymer interactions with the major focus on the methods for the evaluation of solubility and miscibility of the drug in the polymer. Methods for the evaluation of drug-polymer solubility and miscibility have been classified as thermal, spectroscopic, microscopic, solid-liquid equilibrium-based, rheological, and computational methods. Thermal methods have been commonly used to determine the solubility of the drug in the polymer, while other methods provide qualitative information about drug-polymer miscibility. Despite advancements, the majority of these methods are still inadequate to provide the value of drug-polymer miscibility at room temperature. There is still a need for methods that can accurately determine drug-polymer miscibility at pharmaceutically relevant temperatures.

Stabilization mechanism of amorphous carbamazepine by transglycosylated rutin, a non-polymeric amorphous additive with a high glass transition temperature

α-Glycosyl rutin (Rutin-G), composed of a flavonol skeleton and sugar groups, is a promising non-polymeric additive for stabilizing amorphous drug formulations. In this study, the mechanism of the stabilization of the amorphous state of carbamazepine (CBZ) by Rutin-G was investigated. In comparison with hypromellose (HPMC), which is commonly used as a crystallization inhibitor for amorphous drugs, Rutin-G significantly stabilized amorphous CBZ. Moreover, the dissolution rate and the resultant supersaturation level of CBZ were significantly improved in the CBZ/Rutin-G spray-dried samples (SPDs) owing to the rapid dissolution property of Rutin-G. Differential scanning calorimetry measurement demonstrated a high glass transition temperature (T_g) of 186.4°C corresponding to Rutin-G. The CBZ/Rutin-G SPDs with CBZ weight ratios up to 80% showed single glass transitions, indicating the homogeneity of CBZ and Rutin-G. A solid-state NMR experiment using ¹³C- and ¹⁵N-labeled CBZ demonstrated the interaction between the flavonol skeleton of Rutin-G and the amide group of CBZ. A ¹H-¹³C two-dimensional heteronuclear correlation NMR experiment and quantum mechanical calculations confirmed the presence of a possible hydrogen bond between the amino proton in CBZ and the carbonyl oxygen in the flavonol skeleton of Rutin-G. This specific hydrogen bond could contribute to the strong interaction between CBZ and Rutin-G, resulting in the high stability of amorphous CBZ in the CBZ/Rutin-G SPD. Hence, Rutin-G, a non-polymeric amorphous additive with high T_g, high miscibility with drugs, and rapid and pH-independent dissolution properties could be useful in the preparation of amorphous formulations.

Amorphous Solid Dispersions of Felodipine and Nifedipine with Soluplus®: Drug-Polymer Miscibility and Intermolecular Interactions

The objective of this study was to investigate thermodynamic and kinetic miscibility for two structurally similar model compounds nifedipine (NIF) and felodipine (FEL) when formulated as amorphous solid dispersions (ASDs) with an amphiphilic polymer Soluplus®. Thermodynamic miscibility was studied via melting point depression approach for the two systems. The Flory Huggins theory was used to calculate the interaction parameter and generate the phase diagrams. It was shown that NIF was more miscible in Soluplus® than FEL. The nature of drug polymer interactions was studied by fourier transform infra-red spectroscopy (FTIR) and solid-state nuclear magnetic resonance spectroscopy (ssNMR). The data from spectroscopic analyses showed that both the drugs interacted with Soluplus® through hydrogen bonding interactions. Furthermore, ¹³C ssNMR data was used to get quantitative estimate of the extent of hydrogen bonding for ASDs samples. Proton relaxation measurements were carried out on ASDs in order to evaluate phase heterogeneity on two different length scales of mixing. The data suggested that better phase homogeneity in NIF:SOL systems especially for lower Soluplus® content ASDs on smaller domains. This could be explained by understanding the extent of hydrogen bonding interactions for these two systems. This study highlights the need to consider thermodynamic and kinetic mixing, when formulating ASDs with the goal of understanding phase mixing between drug and polymer.

Selective Laser Sintering 3-Dimensional Printing as a Single Step Process to Prepare Amorphous Solid Dispersion Dosage Forms for Improved Solubility and Dissolution Rate

This study reports the development of ritonavir-copovidone amorphous solid dispersions (ASDs) and dosage forms thereof using selective laser sintering (SLS) 3-dimensional (3-D) printing in a single step, circumventing the post-processing steps required in common techniques employed to make ASDs. For this study, different drug loads of ritonavir with copovidone were processed at varying processing conditions to understand the impact, range, and correlation of these parameters for successful ASD formation. Further, ASDs characterized using conventional and advanced solid-state techniques including wide-angle X-ray scattering (WAXS), solid-state nuclear magnetic resonance (ssNMR), revealed the full conversion of the crystalline drug to its amorphous form as a function of laser-assisted selective fusion in a layer-by-layer manner. It was observed that an optimum combination of the powder flow properties, surface temperature, chamber temperature, laser speed, and hatch spacing was crucial for successful ASD formation, any deviations resulted in print failures or only partial amorphous conversion. Moreover, a 21-fold increase in solubility was demonstrated by the SLS 3-D printed tablets. The results confirmed that SLS 3-D printing can be used as a single-step platform for creating ASD-based pharmaceutical dosage forms with a solubility advantage.

A novel amorphous solid dispersion based on drug-polymer complexation

Rafoxanide (RAF) is a poorly water-soluble drug that forms a complex with povidone K25 (PVP) in a cosolvent system containing acetone and an alkaline aqueous medium. This study aims to investigate the impact of RAF-PVP complexation on in vitro and in vivo release of RAF. We prepared two RAF amorphous solid dispersions (ASDs) spray-dried from these two cosolvents. The first is a complexation-based spray-drying using a 70% 0.1 N NaOH solution with 30% acetone. The second is a traditional spray-dried formulation containing 80% acetone and 20% ethanol. Evidence from multiple solid-state characterization techniques indicated that ASDs spray-dried using both methods were amorphous. However, RAF ASDs based on drug-polymer complexation in the feed solution demonstrated not only faster drug release during dissolution testing but also higher in vivo absorption in an animal model. The improved RAF release in the complexation-based ASD is due to (1) high energy state of RAF owing to the amorphous form, (2) high pH in the microenvironment due to the ionized state of RAF and residual sodium hydroxide, (3) increased apparent solubility of RAF results from RAF-PVP complexation in dissolution media and biological media, and (4) improved wettability.

In situ solid-state NMR characterization of pharmaceutical materials: An example of drug-polymer thermal mixing

Pharmaceutical amorphous solid dispersions, a multicomponent system prepared by dispersing drug substances into polymeric matrix via thermal and mechanical processes, represent a major platform to deliver the poorly water-soluble drug. Microscopic properties of drug-polymer contacts play mechanistic roles in manipulating long-term physical stability as well as dissolution profiles. Although solid-state nuclear magnetic resonance has been utilized as an indispensable tool to probe structural details, previous studies are limited to ex situ characterizations. Our work provides likely the first documented example to investigate comelting of ketoconazole and polyacrylic acid, as a model system, in an in situ manner. Their physical mixture is melted and mixed in the solid-state nuclear magnetic resonance rotor under magic angle spinning at up to approximately 400 K. Critical structural events of molecular miscibility and interaction have been successfully identified. These results design and evaluate the instrumental and experimental protocols for real-time characterizations of the comelting of pharmaceutical materials.

Physical stability of amorphous pharmaceutical solids: Nucleation, crystal growth, phase separation and effects of the polymers

Compared to their crystalline forms, amorphous pharmaceutical solids present marvelous potential and advantages for effectively improving the oral bioavailability of poorly water-soluble drugs. A central issue in developing amorphous pharmaceutical solids is the stability against crystallization, which is particularly important for maintaining their advantages in solubility and dissolution rate. This review provides a comprehensive overview of recent studies focusing on the physical stability of amorphous pharmaceutical solids affected by nucleation, crystal growth, phase separation and the addition of polymers. Moreover, we highlight the novel technologies and theories in the field of amorphous pharmaceutical solids. Meanwhile, the challenges and strategies in maintaining the physical stability of amorphous pharmaceutical solids are also discussed. With a better understanding of physical stability, the more robust amorphous pharmaceutical formulations with desired pharmaceutical performance would be easier to achieve.

Component Quantification in Solids with the Mixture Analysis Using References Method

Quantifying components in solid mixtures composed of the same chemical species exhibiting different physical forms represents a difficult challenge in many areas of chemistry. The development of small-molecule active pharmaceutical ingredients (APIs) is a classic example. APIs predominantly exhibit polymorphism and the propensity to form solvates and hydrates. The various API phases typically display different physical properties affecting chemical stability, processability, and bioperformance. Accordingly, API development critically relies on characterizing and quantifying the relevant API forms in complex mixtures in the presence of each other and in the presence of excipients. Presented here is a new solid-state-NMR-based quantification method for components in solid mixtures: mixture analysis using references (MAR). The method utilizes weighted pure component reference spectra in a linear combination fitting procedure to reproduce the corresponding mixture spectrum. The results yield the respective component contributions to the mixture composition. Using several model systems of varying complexity, the applicability and performance of the MAR analysis utilizing ¹³C and ¹⁹F cross-polarization magic-angle-spinning data are evaluated. Finally, the MAR method is compared to one of the most commonly applied traditional quantification methods. The results demonstrate that MAR performs with the same high accuracy as conventional methods. However, MAR exhibits clear efficiency advantages over conventional methods by requiring significantly less overall time (experimental and computational) and displaying remarkable robustness and general applicability. The MAR quantification protocol as presented here can easily be applied to nonpharmaceutical molecular systems in other branches of chemistry.

Solid State NMR Study of the Mixing Degree Between Ginkgo Biloba Extract and a Soy-Lecithin-Phosphatidylserine in a Composite Prepared by the Phytosome® Method

Leaves extract of Ginkgo biloba, known in China since the most ancient times, has been widely used in the area of senile dementia thanks to its improving effects on cognitive function. A promising formulation of this botanical ingredient consists in a Ginkgo biloba-soy-lecithin-phosphatidylserine association obtained by the Phytosome® process. The precise assessment of the mixing degree between Ginkgo biloba and soy-lecithin-phosphatidylserine in this formulation is an important piece of information for understanding the reasons of its final performances. To this aim in the present study we carried out for the first time a Solid State Nuclear Magnetic Resonance investigation on Ginkgo biloba-soy-lecithin-phosphatidylserine association, on its constituents and on a mechanical mixture. The analysis of different observables highlighted a very intimate mixing (domains of single components not larger than 60 nm) of Ginkgo biloba and soy-lecithin-phosphatidylserine in their association obtained by Phytosome® process, together with a slight modification of their molecular dynamics, not observed in the case of the mechanical mixture.

Quantifying Pharmaceutical Formulations from Proton Detected Solid-State NMR under Ultrafast Magic Angle Spinning

Probing form conversions of active pharmaceutical ingredients in solid dosages is critical for understanding the physicochemical stability of drug substances in formulations. The multicomponent and low drug loading nature of drug products often results in challenges to quantify the phase stability, at a low detection limit and with the chemical resolution that differentiate drug molecules and excipients, for routine laboratory techniques. Recent advancement of ultrafast magic angle spinning (UF-MAS) enables proton-detected solid-state nuclear magnetic resonance (ssNMR) techniques to characterize pharmaceutical materials with enhanced resolution and sensitivity. This study demonstrates one of the first documented cases implementing 60 kHz UF-MAS techniques to quantify the minor content of pioglitazone free base (PIO-FB) in a binary system with its hydrochloride salt (PIO-HCl) and a multicomponent formulation with typical excipients. One-dimensional ¹H methods can unambiguously differentiate the two forms and exhibit a limit of detection at 1.77% (w/w). Moreover, we extended it to a two-dimensional ¹H-¹H correlation for minimizing peak overlap and successfully quantifying approximately 2.0% (w/w) PIO-FB in a multicomponent formulation. These results have demonstrated that ¹H ssNMR as a novel method to quantify solid dosages at a higher resolution and faster acquisition than conventional ¹³C techniques.

Local Structural Effects Due to Micronization and Amorphization on an HIV Treatment Active Pharmaceutical Ingredient

Processing procedures for inducing domain size reduction and/or amorphous phase generation can be crucial for enhancing the bioavailability of active pharmaceutical ingredients (APIs). It is important to quantify these reduced coherence phases and to detect and characterize associated structural changes, to ensure that no deleterious effects on safety, function, or stability occur. Here, X-ray powder diffraction (XRPD), total scattering pair distribution function (TSPDF) analysis, and solid-state nuclear magnetic resonance spectroscopy (SSNMR) have been performed on samples of GSK2838232B, an investigational drug for the treatment of human immunodeficiency virus (HIV). Preparations were obtained through different mechanical treatments resulting in varying extents of domain size reduction and amorphous phase generation. Completely amorphous formulations could be prepared by milling and microfluidic injection processes. Microfluidic injection was shown to result in a different local structure due to dispersion with dichloromethane (DCM). Implications of combined TSPDF and SSNMR studies to characterize molecular compounds are also discussed, in particular, the possibility to obtain a thorough structural understanding of disordered samples from different processes.

Investigation into Intermolecular Interactions and Phase Behavior of Binary and Ternary Amorphous Solid Dispersions of Ketoconazole

Conventionally, amorphous solid dispersions (ASDs) have been formulated as a binary matrix, but in recent years a new class of ASDs has emerged, where generally a second polymer is also added to the formulation. Having the presence of a second polymer necessitates a comprehensive solid-state characterization to study the intermolecular interactions and phase behavior on a molecular level. With this goal in mind, ketoconazole (KET) was selected as a model drug, and hydroxypropyl methyl cellulose (HPMC) and poly(acrylic acid) (PAA) were chosen as polymeric carriers. The binary and ternary ASDs were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, solid-state nuclear magnetic resonance (SSNMR) spectroscopy, and powder X-ray diffraction (PXRD). The binary KET:HPMC dispersions lacked any specific interactions, whereas binary KET:PAA dispersions and ternary KET:PAA:HPMC dispersions showed evidence for ionic and hydrogen bonding interactions. The ¹³C SSNMR deconvolution study established a comparison for molecular interactions between the binary KET:PAA and ternary KET:PAA:HPMC dispersions, with the binary KET:PAA system showing higher prevalence of ionic and hydrogen bonds than the ternary KET:PAA:HPMC system. Moreover, individual binary and ternary ASDs were found to be homogeneous on a nanometric level, implying the presence of a second polymer did not impact the phase homogeneity. In addition, a stronger interaction in binary KET:PAA and ternary KET:HPMC:PAA systems translated to better physical stability at different storage conditions. Through this case study it is recommended that a comprehensive investigation is needed to study the impact of using two polymers in ASD formulations in terms underlying intermolecular interactions and physical stability.

Commentary: Considerations in the Measurement of Glass Transition Temperatures of Pharmaceutical Amorphous Solids

An increased interest in using amorphous solid forms in pharmaceutical applications to increase solubility, dissolution, and bioavailability has generated a need for better characterization of key properties, such as the glass transition (Tg) temperature. Although many laboratories measure and report this value, the details around these measurements are often vague or misunderstood. In this article, we attempt to highlight and compare various aspects of the two most common methods used to measure pharmaceutical Tg values, conventional and modulated differential scanning calorimetry (DSC). Issues that directly impact the Tg, such as instrumental parameters, sample preparation methods, data analysis, and "wet" vs. "dry" measurements, are discussed.

Loading-Dependent Structural Model of Polymeric Micelles Encapsulating Curcumin by Solid-State NMR Spectroscopy

Detailed insight into the internal structure of drug‐loaded polymeric micelles is scarce, but important for developing optimized delivery systems. We observed that an increase in the curcumin loading of triblock copolymers based on poly(2‐oxazolines) and poly(2‐oxazines) results in poorer dissolution properties. Using solid‐state NMR spectroscopy and complementary tools we propose a loading‐dependent structural model on the molecular level that provides an explanation for these pronounced differences. Changes in the chemical shifts and cross‐peaks in 2D NMR experiments give evidence for the involvement of the hydrophobic polymer block in the curcumin coordination at low loadings, while at higher loadings an increase in the interaction with the hydrophilic polymer blocks is observed. The involvement of the hydrophilic compartment may be critical for ultrahigh‐loaded polymer micelles and can help to rationalize specific polymer modifications to improve the performance of similar drug delivery systems.

Inhomogeneous Distribution of Components in Solid Protein Pharmaceuticals: Origins, Consequences, Analysis, and Resolutions

Successful development of stable solid protein formulations usually requires the addition of one or several excipients to achieve optimal stability. In these products, there is a potential risk of an inhomogeneous distribution of the various ingredients, specifically the ratio of protein and stabilizer may vary. Such inhomogeneity can be detrimental for stability but is mostly neglected in literature. In the past, it was challenging to analyze inhomogeneous component distribution, but recent advances in analytical techniques have revealed new options to investigate this phenomenon. This paper aims to review fundamental aspects of the inhomogeneous distribution of components of freeze-dried and spray-dried protein formulations. Four key topics will be presented and discussed, including the sources of component inhomogeneity, its consequences on protein stability, the analytical methods to reveal component inhomogeneity, and possible solutions to prevent or mitigate inhomogeneity.

Study the influence of formulation process parameters on solubility and dissolution enhancement of efavirenz solid solutions prepared by hot-melt extrusion: a QbD methodology

The current study investigates the dissolution rate performance of amorphous solid solutions of a poorly water-soluble drug, efavirenz (EFV), in amorphous Soluplus® (SOL) and Kollidon® VA 64 (KVA64) polymeric systems. For the purpose of the study, various formulations with varying drug loadings of 30, 50, and 70% w/w were developed via hot-melt extrusion processing and adopting a Box-Behnken design of experiment (DoE) approach. The polymers were selected based on the Hansen solubility parameter calculation and the prediction of the possible drug-polymer miscibility. In DoE experiments, a Box-Behnken factorial design was conducted to evaluate the effect of independent variables such as Soluplus® ratio (A₁), HME screw speed (A₂), and processing temperature (A₃), and Kollidon®VA64 ratio (B₁), screw speed (B₂), and processing temperature (B₃) on responses such as solubility (X₁ and Y₁) and dissolution rate (X₂ and Y₂) for both ASS [EFV:SOL] and BSS [EFV:KVA64] systems. DSC and XRD data confirmed that bulk crystalline EFV transformed to amorphous form during the HME processing. Advanced chemical analyses conducted via 2D COSY NMR, FTIR chemical imaging, AFM analysis, and FTIR showed that EFV was homogenously dispersed in the respective polymer matrices. The maximum solubility and dissolution rate was observed in formulations containing 30% EFV with both SOL and KVA64 alone. This could be attributed to the maximum drug-polymer miscibility in the optimized formulations. The actual and predicted values of both responses were found precise and close to each other.

Enhanced Aerosolization of High Potency Nanoaggregates of Voriconazole by Dry Powder Inhalation

Invasive pulmonary aspergillosis is a deadly fungal infection with a high mortality rate, particularly in patients having undergone transplant surgery. Voriconazole, a triazole antifungal pharmaceutical product, is considered as a first-line therapy for invasive pulmonary aspergillosis, and exhibits efficacy even for patients who have failed other antifungal drug therapies. The objective of this study is to develop high potency nanoaggregates of crystalline voriconazole composition for dry powder inhalation using the particle engineering process, thin film freezing. In this study, mannitol at low concentrations acted as a surface texture-modifying agent, and we evaluated the physicochemical and aerodynamic properties of the voriconazole formulations containing different amounts of mannitol. In vitro aerosol performance data demonstrated that powder formulations consisting of 90 to 97% (w/w) voriconazole were the optimum for inhalation with a fine particle fraction (% of delivered dose) as high as 73.6 ± 3.2% and mass median aerodynamic diameter of 3.03 ± 0.17 μm when delivered by a commercially available device. The thin film freezing process enabled phase-separated submicron crystalline mannitol to be oriented such as to modify the surface texture of the crystalline voriconazole nanoaggregates, thus enhancing their aerosolization. Addition of as low as 3% (w/w) mannitol significantly increased the fine particle fraction (% of metered dose) of voriconazole nanoaggregates when compared to compositions without mannitol (40.8% vs 24.6%, respectively). The aerosol performance of the voriconazole nanoaggregates with 5% (w/w) mannitol was maintained for 13 months at 25 °C/60% RH. Therefore, voriconazole nanoaggregates having low amounts of surface texture-modifying mannitol made by thin film freezing are a feasible local treatment option for invasive pulmonary aspergillosis with high aerosolization efficiency and drug loading for dry powder inhalation.