Crystallinity: A Complex Critical Quality Attribute of Amorphous Solid Dispersions.

Does the performance of an amorphous solid dispersion rely on having 100% amorphous content? What specifications are appropriate for crystalline content within an amorphous solid dispersion (ASD) drug product? In this Perspective, the origin and significance of crystallinity within amorphous solid dispersions will be considered. Crystallinity can be found within an ASD from one of two pathways: (1) incomplete amorphization, or (2) crystal creation (nucleation and crystal growth). While nucleation and crystal growth is the more commonly considered pathway, where crystals originate as a physical stability failure upon accelerated or prolonged storage, manufacturing-based origins of crystallinity are possible as well. Detecting trace levels of crystallinity is a significant analytical challenge, and orthogonal methods should be employed to develop a holistic assessment of sample properties. Probing the impact of crystallinity on release performance which may translate to meaningful clinical significance is inherently challenging, requiring optimization of dissolution test variables to address the complexity of ASD formulations, in terms of drug physicochemical properties (e.g., crystallization tendency), level of crystallinity, crystal reference material selection, and formulation characteristics. The complexity of risk presented by crystallinity to product performance will be illuminated through several case studies, highlighting that a one-size-fits-all approach cannot be used to set specification limits, as the risk of crystallinity can vary widely based on a multitude of factors. Risk assessment considerations surrounding drug physicochemical properties, formulation fundamentals, physical stability, dissolution, and crystal micromeritic properties will be discussed.

Impact of Aluminum Oxide Nanocoating on Drug Release from Amorphous Solid Dispersion Particles.

Atomic layer coating (ALC) is emerging as a particle engineering strategy to inhibit surface crystallization of amorphous solid dispersions (ASDs). In this study, we turn our attention to evaluating drug release behavior from ALC-coated ASDs, and begin to develop a mechanistic framework. Posaconazole/hydroxypropyl methylcellulose acetate succinate was used as a model system at both 25% and 50% drug loadings. ALC-coatings of aluminum oxide up to 40 nm were evaluated for water sorption kinetics and dissolution performance under a range of pH conditions. Scanning electron microscopy with energy dispersive X-ray analysis was used to investigate the microstructure of partially released ASD particles. Coating thickness and defect density (inferred from deposition rates) were found to impact water sorption kinetics. Despite reduced water sorption kinetics, the presence of a coating was not found to impact dissolution rates under conditions where rapid drug release was observed. Under slower releasing conditions, underlying matrix crystallization was reduced by the coating, enabling greater levels of drug release. These results demonstrate that water was able to penetrate through the ALC coating, hydrating the amorphous solid, which can initiate dissolution of drug and/or polymer (depending on pH conditions). Swelling of the ASD substrate subsequently occurs, disrupting and cracking the coating, which serves to facilitate rapid drug release. Water sorption kinetics are highlighted as a potential predictive tool to investigate the coating quality and its potential impact on dissolution performance. This study has implications for formulation design and evaluation of ALC-coated ASD particles.

Impact of Polymer Type on Thermal Degradation of Amorphous Solid Dispersions Containing Ritonavir.

High-temperature exposure during hot melt extrusion processing of amorphous solid dispersions may result in thermal degradation of the drug. Polymer type may influence the extent of degradation, although the underlying mechanisms are poorly understood. In this study, the model compound, ritonavir (Tm = 126 °C), undergoes thermal degradation upon high-temperature exposure. The extent of degradation of ritonavir in amorphous solid dispersions (ASDs) formulated with poly(vinylpyrrolidone) (PVP), poly(vinylpyrrolidone) vinyl acetate copolymer (PVP/VA), hydroxypropyl methylcellulose acetate succinate (HPMCAS), and hydroxypropyl methylcellulose (HPMC) following isothermal heating and hot melt extrusion was evaluated, and mechanisms related to molecular mobility and intermolecular interactions were assessed. Liquid chromatography-mass spectrometry (LC-MS/MS) studies were used to determine the degradation products and pathways and ultimately the drug-polymer compatibility. The dominant degradation product of ritonavir was the result of a dehydration reaction, which then catalyzed a series of hydrolysis reactions to generate additional degradation products, some newly reported. This reaction series led to accelerated degradation rates with protic polymers, HPMCAS and HPMC, while ASDs with aprotic polymers, PVP and PVP/VA, had reduced degradation rates. This work has implications for understanding mechanisms of thermal degradation and drug-polymer compatibility with respect to the thermal stability of amorphous solid dispersions.

Effect of Polymer Species on Maximum Aqueous Phase Supersaturation Revealed by Quantitative Nuclear Magnetic Resonance Spectroscopy.

The polymer used in an amorphous solid dispersion (ASD) formulation impacts the maximum achievable drug supersaturation. Herein, the effect of dissolved polymer on drug concentration in the aqueous phase when a drug-rich phase was generated by liquid-liquid phase separation (LLPS) was investigated for different polymers at various concentrations of drug and polymer. Solution nuclear magnetic resonance (NMR) spectroscopy revealed that polyvinylpyrrolidone (PVP), polyvinylpyrrolidone/vinyl acetate (PVP-VA), and hypromellose (HPMC) distributed into the ibuprofen (IBP)-rich phase formed by LLPS when the amorphous solubility of IBP was exceeded. The amount of polymer in the drug-rich phase increased for higher-molecular-weight grades of PVP and HPMC. Moreover, PVP-VA showed a greater extent of distribution into the IBP-rich phase compared to PVP, and this is attributed to its reduced hydrophilicity resulting from the incorporation of vinyl acetate monomers. Direct quantification by NMR measurements indicated that the IBP concentration in the aqueous phase decreased as the amount of polymer in the IBP-rich phase increased. This can be attributed to a reduction of the chemical potential of IBP in the IBP-rich phase. The reduction in dissolved IBP concentration was greater for the IBP/PVP-VA system compared to the IBP/HPMC system, as a result of more extensive drug-polymer interactions in the former system. The present study highlights the impact of polymer selection on the attainable supersaturation of the drug and the factors that need to be considered in the formulation of ASDs to obtain optimized in vivo performance.

Interaction of Polymers with Enzalutamide Nanodroplets-Impact on Droplet Properties and Induction Times.

Amorphous solid dispersions (ASDs), which consist of a drug dispersed in a polymeric matrix, are increasingly being applied to improve the in vivo performance of poorly water-soluble drugs delivered orally. The polymer is a critical component, playing several roles including facilitating drug release from the ASD, as well as delaying crystallization from the supersaturated solution generated upon dissolution. Certain ASD formulations dissolve to produce amorphous drug-rich nanodroplets. The interaction of the polymer with these nanodroplets is poorly understood but is thought to be important for inhibiting crystallization in these systems. In this study, the impact of ionic polymers on the crystallization kinetics of enzalutamide from supersaturated solutions containing different amounts of amorphous nanodroplets was evaluated by determination of nucleation induction times. The amount of the polymer associated with the drug nanodroplets was also determined. When comparing two polymers, hydroxypropylmethyl cellulose acetate succinate (HPMCAS) and Eudragit E PO, it was found that the crystallization tendency and physical properties of the drug nanodroplets varied in the presence of these two polymers. Both polymers distributed between the aqueous phase and the drug-rich nanodroplets. A greater amount of Eudragit E PO was associated with the drug-rich nanodroplets. Despite this, Eudragit E PO was a less-effective crystallization inhibitor than HPMCAS in systems containing nanodroplets. In conclusion, in supersaturated solutions containing amorphous nanodroplets, the extent of association of a polymer with the drug nanodroplet does not solely predict crystallization inhibition.

Interplay of Supersaturation and Solubilization: Lack of Correlation between Concentration-Based Supersaturation Measurements and Membrane Transport Rates in Simulated and Aspirated Human Fluids.

Supersaturating formulations are increasingly being used to improve the absorption of orally administered poorly water-soluble drugs. To better predict outcomes in vivo, we must be able to accurately determine the degree of supersaturation in complex media designed to provide a surrogate for the gastrointestinal environment. Herein, we demonstrate that relying on measurements based on consideration of the total dissolved concentration leads to underestimation of supersaturation and consequently membrane transport rates. Crystalline and amorphous solubilities of two compounds, atazanavir and posaconazole, were evaluated in six different media. Concurrently, diffusive flux measurements were performed in a side-by-side diffusion cell to determine the activity-based supersaturation by evaluating membrane transport rates at the crystalline and amorphous solubilities. Solubility values were found to vary in each medium because of different solubilization capacities. Concentration-based supersaturation ratios were also found to vary for the different media. Activity-based measurements, however, were largely independent of the medium, leading to relatively constant values for the estimated supersaturation. These findings have important consequences for modeling and prediction of supersaturation impact on the absorption rate as well as for better defining the thermodynamic driving force for crystallization in complex media.

Trends in amorphous solid dispersion drug products approved by the U.S. Food and Drug Administration between 2012 and 2023.

Forty-eight (48) drug products (DPs) containing amorphous solid dispersions (ASDs) have been approved by the U.S. Food and Drug Administration in the 12-year period between 2012 and 2023. These DPs comprise 36 unique amorphous drugs. Ten (10) therapeutic categories are represented, with most DPs containing antiviral and antineoplastic agents. The most common ASD polymers are copovidone (49%) and hypromellose acetate succinate (30%), while spray drying (54%) and hot melt extrusion (35%) are the most utilized manufacturing processes to prepare the ASD drug product intermediate (DPI). Tablet dosage forms are the most common, with several capsule products available. Line extensions of several DPs based on flexible oral solids and powders for oral suspension have been approved which provide patient-centric dosing to pediatric and other patient populations. The trends in the use of common excipients and film coating types are discussed. Eighteen (18) DPs are fixed-dose combinations, and some contain a mixture of amorphous and crystalline drugs. The DPs have dose/unit of amorphous drug ranging from <5 mg up to 300 mg, with the majority being ≤100 mg/unit. This review details several aspects of DPI and DP formulation and manufacturing of ASDs, as well as trends related to therapeutic category, dose, and patient-centricity.

Formulation and Processing Strategies which Underpin Susceptibility to Matrix Crystallization in Amorphous Solid Dispersions.

Through matrix crystallization, an amorphous solid may transform directly into its more stable crystalline state, reducing the driving force for dissolution. Herein, the mechanism of matrix crystallization in an amorphous solid dispersion (ASD) was probed. ASDs of bicalutamide/copovidone were prepared by solvent evaporation and hot melt extrusion, and sized by mortar and pestle or cryomilling techniques, modulating the level of mechanical activation experienced by the sample. Drug loading (DL) of the binary ASD was varied from 5-50%, and ternary systems were formulated at 30% DL with two surfactants (sodium dodecyl sulfate, Vitamin E TPGS). Imaging of partially dissolved or crystallized compacts by scanning electron microscopy with energy-dispersive X-ray analysis and confocal fluorescence microscopy was performed to investigate pathways of hydration, phase separation, and crystallization. Monitoring drug and polymer release of ASD powder under non-sink conditions provided insight into supersaturation and desupersaturation profiles. Systems at the greatest risk of matrix crystallization had high DLs, underwent mechanical activation, and/or contained surfactant. Systems having greatest resistance to matrix crystallization had rapid and congruent drug and polymer release. This study has implications for formulation and process design of ASDs and risk assessment of matrix crystallization.

Control of drug release kinetics from hot-melt extruded drug-loaded polycaprolactone matrices.

Sustained local delivery of meloxicam by polymeric structures is desirable for preventing subacute inflammation and biofilm formation following tissue incision or injury. Our previous study demonstrated that meloxicam release from hot-melt extruded (HME) poly(ε-caprolactone) (PCL) matrices could be controlled by adjusting the drug content. Increasing drug content accelerated the drug release as the initial drug release generated a pore network to facilitate subsequent drug dissolution and diffusion. In this study, high-resolution micro-computed tomography (HR µCT) and artificial intelligence (AI) image analysis were used to visualize the microstructure of matrices and simulate the drug release process. The image analysis indicated that meloxicam release from the PCL matrix was primarily driven by diffusion but limited by the amount of infiltrating fluid when drug content was low (i.e., the connectivity of the drug/pore network was poor). Since the drug content is not easy to change when a product has a fixed dose and dimension/geometry, we sought an alternative approach to control the meloxicam release from the PCL matrices. Here, magnesium hydroxide (Mg(OH)2) was employed as a solid porogen in the drug-PCL matrix so that Mg(OH)2 dissolved with time in the aqueous environment creating additional pore networks to facilitate local dissolution and diffusion of meloxicam. PCL matrices were produced with a fixed 30 wt% meloxicam loading and variable Mg(OH)2 loadings from 20 wt% to 50 wt%. The meloxicam release increased in proportion to the Mg(OH)2 content, resulting in almost complete drug release in 14 d from the matrix with 50 wt% Mg(OH)2. The porogen addition is a simple strategy to tune drug release kinetics, applicable to other drug-eluting matrices with similar constraints.

Drug Dissolution in Oral Drug Absorption: Workshop Report.

The in-person workshop "Drug Dissolution in Oral Drug Absorption" was held on May 23-24, 2023, in Baltimore, MD, USA. The workshop was organized into lectures and breakout sessions. Three common topics that were re-visited by various lecturers were amorphous solid dispersions (ASDs), dissolution/permeation interplay, and in vitro methods to predict in vivo biopharmaceutics performance and risk. Topics that repeatedly surfaced across breakout sessions were the following: (1) meaning and assessment of "dissolved drug," particularly of poorly water soluble drug in colloidal environments (e.g., fed conditions, ASDs); (2) potential limitations of a test that employs sink conditions for a poorly water soluble drug; (3) non-compendial methods (e.g., two-stage or multi-stage method, dissolution/permeation methods); (4) non-compendial conditions (e.g., apex vessels, non-sink conditions); and (5) potential benefit of having both a quality control method for batch release and a biopredictive/biorelevant method for biowaiver or bridging scenarios. An identified obstacle to non-compendial methods is the uncertainty of global regulatory acceptance of such methods.

Atomic Layer Coating to Inhibit Surface Crystallization of Amorphous Pharmaceutical Powders.

Preventing crystallization is a primary concern when developing amorphous drug formulations. Recently, atomic layer coatings (ALCs) of aluminum oxide demonstrated crystallization inhibition of high drug loading amorphous solid dispersions (ASDs) for over 2 years. The goal of the current study was to probe the breadth and mechanisms of this exciting finding through multiple drug/polymer model systems, as well as particle and coating attributes. The model ASD systems selected provide for a range of hygroscopicity and chemical functional groups, which may contribute to the crystallization inhibition effect of the ALC coatings. Atomic layer coating was performed to apply a 5-25 nm layer of aluminum oxide or zinc oxide onto ASD particles, which imparted enhanced micromeritic properties, namely, reduced agglomeration and improved powder flowability. ASD particles were stored at 40 °C and a selected relative humidity level between 31 and 75%. Crystallization was monitored by X-ray powder diffraction and scanning electron microscopy (SEM) up to 48 weeks. Crystallization was observable by SEM within 1-2 weeks for all uncoated samples. After ALC, crystallization was effectively delayed or completely inhibited in some systems up to 48 weeks. The delay achieved was demonstrated regardless of polymer hygroscopicity, presence or absence of hydroxyl functional groups in drugs and/or polymers, particle size, or coating properties. The crystallization inhibition effect is attributed primarily to decreased surface molecular mobility. ALC has the potential to be a scalable strategy to enhance the physical stability of ASD systems to enable high drug loading and enhanced robustness to temperature or relative humidity excursions.

Development of hot-melt extruded drug/polymer matrices for sustained delivery of meloxicam.

For effective resolution of regional subacute inflammation and prevention of biofouling formation, we have developed a polymeric implant that can release meloxicam, a selective cyclooxygenase (COX)-2 inhibitor, in a sustained manner. Meloxicam-loaded polymer matrices were produced by hot-melt extrusion, with commercially available biocompatible polymers, poly(ε-caprolactone) (PCL), poly(lactide-co-glycolide) (PLGA), and poly(ethylene vinyl acetate) (EVA). PLGA and EVA had a limited control over the drug release rate partly due to the acidic microenvironment and hydrophobicity, respectively. PCL allowed for sustained release of meloxicam over two weeks and was used as a carrier of meloxicam. Solid-state and image analyses indicated that the PCL matrices encapsulated meloxicam in crystalline clusters, which dissolved in aqueous medium and generated pores for subsequent drug release. The subcutaneously implanted meloxicam-loaded PCL matrices in rats showed pharmacokinetic profiles consistent with their in vitro release kinetics, where higher drug loading led to faster drug release. This study finds that the choice of polymer platform is crucial to continuous release of meloxicam and the drug release rate can be controlled by the amount of drug loaded in the polymer matrices.

Exploring the Role of Surfactants in Enhancing Drug Release from Amorphous Solid Dispersions at Higher Drug Loadings.

To reduce the dosage size of amorphous solid dispersion (ASD)-based formulations, it is of interest to devise formulation strategies that allow increased drug loading (DL) without compromising dissolution performance. The aim of this study was to explore how surfactant addition impacts drug release as a function of drug loading from a ternary ASD, using felodipine as a model poorly soluble compound. The addition of 5% TPGS (d-α-tocopheryl polyethylene glycol 1000 succinate, a surfactant) to felodipine-polyvinylpyrrolidone/vinyl acetate ASDs was found to facilitate rapid and congruent (i.e., simultaneous) release of drug and polymer at higher DLs relative to binary ASDs (drug and polymer only). For binary ASDs, good release was observed for DLs up to <20% DL; this increased to 35% DL with surfactant. Microstructure evolution in ASD films following exposure to 100% relative humidity was studied using atomic force microscopy coupled with nanoscale infrared imaging. The formation of discrete, spherical drug-rich domains in the presence of surfactant appeared to be linked to systems showing congruent and rapid release of drug and polymer. In contrast, a contiguous drug-rich phase was formed for systems without surfactant at higher DLs. This study supports the addition of surfactant to ASD formulations as a strategy to increase DL without compromising release. Furthermore, insights into the potential role of surfactant in altering ASD release mechanisms are provided.

Amorphous Solid Dispersions Containing Residual Crystallinity: Competition Between Dissolution and Matrix Crystallization.

Crystallinity in an amorphous solid dispersion (ASD) may negatively impact dissolution performance by causing lost solubility advantage and/or seeding crystal growth leading to desupersaturation. The goal of the study was to evaluate underlying dissolution and crystallization mechanisms resulting from residual crystallinity contained within bicalutamide (BCL)/polyvinylpyrrolidone vinyl acetate copolymer (PVPVA) ASDs produced by hot melt extrusion (HME). In-line Raman spectroscopy, polarized light microscopy, and scanning electron microscopy were used to characterize crystallization kinetics and mechanisms. The fully amorphous ASD (0% crystallinity) did not dissolve completely, and underwent crystallization to the metastable polymorph (form 2), initiating in the amorphous matrix at the interface of the amorphous solid with water. Under non-sink conditions, higher extents of supersaturation were achieved because dissolution initially proceeded unhindered prior to nucleation. ASDs containing residual crystallinity had markedly reduced supersaturation. Solid-mediated crystallization (matrix crystallization) consumed the amorphous solid, growing the stable polymorph (form 1). Under sink conditions, both the fully amorphous ASD and crystalline physical mixture achieve faster release than the ASDs containing residual crystallinity. In the latter systems, matrix crystallization leads to highly agglomerated crystals with high relative surface area. Solution-mediated crystallization was not a significant driver of concentration loss, due to slow crystal growth from solution in the presence of PVPVA. The high risk stemming from residual crystallinity in BCL/PVPVA ASDs stems from (1) fast matrix crystallization propagating from crystal seeds, and (2) growth of the stable crystal form. This study has implications for dissolution performance outcomes of ASDs containing residual crystallinity.

Patterns of drug release as a function of drug loading from amorphous solid dispersions: A comparison of five different polymers.

To reduce the pill burden associated with amorphous solid dispersions (ASDs), which arises from the large quantity of polymer used in the formulation, it is of interest to understand the relationship between drug loading and release properties. The aim of this study was to comprehensively evaluate drug release mechanisms from ASDs with polymers of varying hydrophobicity as a function of drug loading. Surface normalized dissolution rates of drug and polymer were studied for felodipine ASDs with polyvinylpyrrolidone (PVP), polyvinylpyrrolidone/vinyl acetate (PVPVA), EudragitⓇ S 100 (EUDS), hydroxypropylmethylcellulose (HPMC), and hydroxypropylmethylcellulose acetate succinate (HPMCAS), as a function of drug loading. The water sorption profiles and water contact angle measurements suggested the following rank order for hydrophobicity of the different polymers: HPMCAS  ≃  EUDS > HPMC > PVPVA > PVP. For ASDs with relatively hydrophilic polymers (PVP, PVPVA and HPMC), drug release rates were polymer-controlled at low drug loadings (≤15%), whereas at higher drug loadings, release rates were more similar to that of the amorphous drug. The sudden decline in the release performance of ASDs with hydrophilic polymers when a certain drug loading was reached, was attributed to water-induced phase separation. For ASDs with more hydrophobic polymers (HPMCAS and EUDS), the dissolution rate of both drug and polymer was polymer-controlled for drug loadings as high as 50%, with a more gradual decline in drug release rate at higher drug loadings. Notably, at low drug loadings and across the different polymers, when the polymer dictated the drug release rate, ASDs prepared with the most hydrophilic polymers showed the fastest drug release. This suggested a 'trade-off' in choosing between higher release rates with more hydrophilic polymers at low drug loadings and higher drug loadings achievable with more hydrophobic polymers at the expense of lowered release rates. The findings described herein have significant implications for rational selection of polymers for formulation of ASDs with high drug loading and enhanced dissolution performance.

Amorphous solid dispersions containing residual crystallinity: Influence of seed properties and polymer adsorption on dissolution performance.

The solubility advantage of amorphous solid dispersions (ASDs) is contingent upon supersaturation being generated and maintained. If crystals are present within an ASD, these crystals directly result in lost solubility advantage, and may also seed crystal growth leading to desupersaturation. The goal of this study was to evaluate the impact of residual crystals on ASD supersaturation profiles. Indomethacin-copovidone (PVPVA) ASDs with different levels of residual crystallinity were manufactured by hot melt extrusion (HME). PVPVA at 5 and 50 µg/mL was found to be a highly effective nucleation and crystal growth inhibitor of indomethacin at high supersaturation. Evidence of polymer adsorption onto indomethacin crystals was observed by atomic force microscopy and scanning electron microscopy. HME ASDs containing 0-25% residual crystallinity demonstrated lost solubility advantage, along with minimal desupersaturation during non-sink dissolution testing. While bulk seeds did not properly represent the impact of residual crystals, extensive polymer adsorption onto residual seed crystals resulted in poisoned crystal growth, limiting the potential dissolution performance consequences. Several risk factors related to the presence of residual crystallinity were identified: polymeric crystal growth inhibition effectiveness, seed properties, and supersaturation conditions.

Application and limitations of thermogravimetric analysis to delineate the hot melt extrusion chemical stability processing window.

Thermogravimetric analysis (TGA) is frequently used to define the threshold of acceptable processing temperatures for hot melt extrusion. Herein, evaluation of chemical stability of amorphous drug and polymer systems was assessed by a critical evaluation of TGA nonisothermal and isothermal methods. Nonisothermal analysis of three crystalline APIs of high glass-forming ability (posaconazole, indomethacin, and bicalutamide), as well as six common polymers, identified a degradation onset temperature that ranged from 52 to 170 °C, depending on heating rate and degradation detection method employed. In particular, the tangent method significantly overestimated the onset of acceptable levels of degradation, while weight loss threshold criteria were more suitable. Isothermal analysis provided a more direct indication of chemical stability, however neat amorphous materials are likely to recrystallize. By forming an amorphous solid dispersion, the polymer can stabilize the amorphous drug against recrystallization, enabling isothermal analysis of chemical degradation. However, TGA mass loss of volatiles should be considered only as an approximate indicator of degradation, as actual potency loss is likely to be significantly higher; this was confirmed by high performance liquid chromatographic analysis of samples. TGA methods should be selected to generate highly sensitive outcomes, and caution should be applied when extrapolating suitability of processing conditions.

The application of temperature-composition phase diagrams for hot melt extrusion processing of amorphous solid dispersions to prevent residual crystallinity.

Hot melt extrusion (HME) can be used to produce amorphous solid dispersions (ASDs) at temperatures below the drug's melting point if the drug and polymer exhibit melting point depression. However, the risk of residual crystallinity becomes significant. The purpose of this study was to apply the temperature-composition phase diagram to the HME process, correlating process conditions to ASD residual crystallinity, and identifying the formulation critical temperature, which defines the theoretical minimum processing temperature. The phase diagram of indomethacin (IDM) and polyvinylpyrrolidone/vinyl acetate copolymer (PVPVA) was generated using melting point depression measurements coupled with Flory-Huggins theory. Extrudates were manufactured above, at, and below the formulation critical temperature (Tc) as identified from the phase diagram, with a range of residence times, and characterized for crystallinity. Below the Tc, a fully amorphous sample could not be prepared. Above Tc, sufficient residence time led to amorphous samples. A processing operating design space diagram with three regimes was generated to correlate temperature and residence time factors with process outcome. In conclusion, phase diagrams provide a rational basis for designing hot melt extrusion processes of amorphous solid dispersions to minimize residual crystalline content, delineating the minimum processing temperature based on thermodynamic considerations.