Enhanced Solubility of High Melting BCS Class IV Compounds Using Novel Liquid-Assisted Hot Melt Extrusion

Abstract

Insufficient aqueous dissolution properties constitute a fundamental barrier impacting approximately 40% of commercialized and 90% developmental pharmaceuticals, significantly limiting therapeutic absorption and oral bioavailability. Conventional hot-melt extrusion (HME) encounters thermal degradation limitations when processing high-melting point APIs. This study introduces a novel liquid-assisted hot-melt extrusion (LA-HME) approach for alectinib hydrochloride (ALH; mp >300°C), a BCS Class IV compound, utilizing systematic Quality-by-Design principles. A Box-Behnken experimental design (n=15) optimized critical process parameters using twin-screw extruder: processing temperature (150-210°C), DMSO content (0-20% w/w), and screw speed (80-120 rpm). The ternary carrier system comprised Soluplus® and vitamin E TPGS (1:1:0.25 ratio). LA-HME successfully enabled processing 50°C below AH’s melting point, achieving >95% amorphization confirmed by DSC and PXRD analysis. Optimized HME conditions (180°C, 10% DMSO, 100 rpm screw speed) demonstrated remarkable performance enhancement: aqueous solubility increased from 20.0 ± 0.2 μg/mL (crystalline) to 249.1 ± 2.9 μg/mL (12.5-fold improvement; p<0.001), while dissolution performance improved from 28.9 ± 0.4% to 98.0 ± 1.6% at 60 minutes (p<0.001). Statistical validation confirmed robust regression models with R²_adj ≥ 0.954 and R²_pred ≥ 0.918, supported by ANOVA significance (p<0.001). Comprehensive ICH stability studies over six months revealed <4% drift in critical quality attributes, confirming formulation stability. This LA-HME methodology successfully expands HME applicability to thermally sensitive, high- melting APIs while maintaining excellent scalability and regulatory compliance for pharmaceutical manufacturing.

Introduction

Contemporary drug development faces substantial challenges due to inadequate aqueous solubility, affecting roughly 40% of marketed therapeutics and up to 90% of developmental compounds, severely limiting oral bioavailability1,2. Compounds under BCS Class II and IV, with inadequate dissolution characteristics, experience absorption constraints within gastrointestinal systems, making solubility improvement essential for therapeutic success2, 3. Multiple therapeutic formulation methodologies have been developed to overcome dissolution constraints, including salt formation, particle dimension optimization, lipidic delivery platforms, and advanced material engineering technologies4,5. Solid dispersions represent the leading strategy, incorporating active compounds within polymeric carriers to enhance dissolution through increased surface area, improved wetting characteristics, and potential amorphization5,6. Manufacturing techniques include solvent evaporation, spray drying, hot melt extrusion, lyophilization, and co-precipitation methods 6,7.

Amorphous pharmaceutical preparations demonstrate augmented solubility and dissolution characteristics compared to crystalline counterparts due to higher internal energy states and absence of ordered molecular arrangements8. However, thermodynamic instability makes these systems susceptible to recrystallization over time9. Amorphous solid dispersions mitigate this through polymeric matrix stabilization, limiting molecular mobility to prevent crystallization and improve physical stability10, 11. Effective polymer selection requires materials that inhibit molecular motion and prevent drug recrystallization, with polyvinylpyrrolidone, hydroxypropyl methylcellulose, copovidone, and Soluplus® being commonly utilized options compatible with both solvent and melt-based processing12, 13.

Among manufacturing technologies, spray drying and hot melt extrusion represent the primary industrial applications14. HME offers continuous processing advantages while reducing organic solvent usage, providing environmental and economic benefits15, 16. Despite its established role in amorphous solid dispersion production, conventional HME faces substantial limitations when processing high-melting- point APIs, as required temperatures often exceed thermal degradation thresholds, excluding many promising candidates from development17, 18.

Liquid-Assisted Hot Melt Extrusion addresses these limitations through pharmaceutical solvent incorporation19. Maniruzzaman et al. pioneered LA- HME using meloxicam, demonstrating that small amounts of pharmaceutically acceptable solvents could reduce processing temperatures below API melting points, enabling successful amorphous solid dispersion formation20. However, considerable knowledge gaps and technical limitations remained after this initial work21.

ALH a BCS Class IV compound exemplifies these formulation challenges exhibiting marginal solubility and low permeability22. Used clinically as an anaplastic lymphoma kinase inhibitor for ALK- positive non-small-cell lung cancer treatment, ALH contains a benzo[b]carbazole core with substituted morpholinylpiperidine side chains, contributing to hydrophobic properties and solubility constraints23, 24. ALH exhibits extremely limited aqueous solubility (0.0221 mg/mL), moderate lipophilicity (log P = 1.96), and high melting point (>300°C with decomposition), making it unsuitable for conventional HME processing24, 25. Despite substantial particle size reduction, ALH maintains inadequate solubility and achieves only 37% oral bioavailability under fed conditions, necessitating advanced formulation approaches ensuring both solubility enhancement and thermal stability25, 26.

This study presents four key innovations: First, systematic LA-HME application to a BCS Class IV compound with exceptionally high melting point (>300°C), achieving 50°C processing temperature reduction compared to previous meloxicam studies27. Second, DMSO utilization as a transient solubilizing agent provides superior plasticizing properties and improved API solubilization, achieving >95% amorphization versus partial crystallinity retention in DMF-based systems28. Third, comprehensive Quality- by-Design implementation using systematic Box- Behnken experimental design provides statistically validated process understanding with reliable predictive models (R² > 0.95)29. Fourth, exceptional 12.5-fold solubility enhancement substantially exceeds previous LA-HME improvements through optimized ternary carrier system development and systematic process optimization30.

Beyond empirical improvements, this research advances mechanistic understanding by elucidating DMSO’s dual mechanism: transient plasticization during processing and molecular-level API dissolution within polymeric matrices34. Post-processing solvent removal creates stabilized amorphous networks with improved thermodynamic stability compared to conventional HME products32. Comprehensive ICH- compliant analytical validation, stability demonstration, and process robustness evaluation establish regulatory frameworks for LA-HME technology commercialization, confirming LA-HME as a platform technology for pharmaceutical industry’s most challenging formulation problems33, 34.

Download the full article as PDF here Enhanced Solubility of High Melting BCS Class IV Compounds Using Novel Liquid-Assisted Hot Melt Extrusion

Materials

Alectinib hydrochloride (ALH, purity >99.5%) polymorphic Form I was provided as a gift sample by Cadila Healthcare Limited (Ahmedabad, India). Soluplus® (polyvinyl caprolactam-polyvinyl acetate- polyethylene glycol graft copolymer, molecular weight ~118,000) and sodium lauryl sulfate were obtained from BASF Corporation (Ludwigshafen, Germany)35. Vitamin E TPGS (D-α-tocopheryl polyethylene glycol 1000 succinate, pharmaceutical grade) was supplied by PMC Isochem (Vert-le-Petit, France)36. Dimethyl sulfoxide (DMSO, analytical reagent grade, ≥99.9% purity) was purchased from Finar Chemicals Limited (Ahmedabad, India)37. All other  chemicals  and  reagents met analytical specifications and required no additional purification prior to use.

Enhanced Solubility of High Melting BCS Class IV Compounds Using Novel Liquid-Assisted Hot Melt Extrusion, Abhishek Jain, Pragna Shelat, Journal of Molecular Science, Volume 35 Issue 4, Year of Publication 2025, Page 1755-1765, DoI-10.004687/1000-9035.2025.228

Enjoy our new free webinar, registration & information here: