Optimization of Sugar-Derivatives Mixtures for Stabilizing Polyclonal Immunoglobulin G in Spray-Dried Inhalable Powders During Processing and Long-Term Storage

Background/Objectives: The development of dry powder formulations for pulmonary delivery of therapeutic antibodies requires careful stabilization strategies to preserve protein integrity during spray-drying and long-term storage. This study investigates the impact of various sugar-derivatives, a polyol (D-mannitol), a disaccharide (D-sucrose) and a polysaccharide (dextran 10 kDa), used individually or in combination, on the physical stability of bovine polyclonal immunoglobulin G (pAb) in dry powders for inhalation (DPIs). Methods: A design of experiments (DoE) approach was employed to evaluate the effects of these excipients on residual moisture (RM), low-order aggregates (LOA) and high-order aggregates (HOA), immediately after spray-drying (T0) and after 10 months of storage at room temperature in a desiccator (T10). Results: All DPIs exhibited a high amorphous content and a favorable glass transition temperature, with RM decreasing over time. The combination of D-mannitol and dextran 10 kDA (DPI-MD) demonstrated the most effective stabilization, minimizing LOA and HOA formation at T0 and T10. Although the ternary mixture, including D-sucrose (DPI-MSD) exhibited higher process stability, it was less stable over time in comparison to the binary mixture. The aerodynamic performance of these carrier-free DPIs, assessed via laser diffraction (% ˂ 5 µm), were between 51 ± 3 (DPI-MD) and 67 ± 4 (DPI MSD) and a Next Generation Impactor, confirmed that formulation produced aerosol with suitable size distribution and fine particle fractions (FPFn upt to 71 ± 5% for DPI-MSD), for deep pulmonary deposition. Conclusions: These findings highlight the importance of combining excipients with complementary physical properties to achieve robust protein stabilization. The DPI-MD emerged as the most promising candidate for pAb lung delivery, balancing protein integrity, powder stability, and aerodynamic efficiency.

Background:

The development of dry powder formulations for pulmonary delivery of therapeutic antibodies requires careful stabilization strategies to preserve protein integrity during spray-drying and long-term storage. This study investigates the impact of various sugar-derivatives—specifically a polyol (D-mannitol), a disaccharide (D-sucrose), and a polysaccharide (dextran 10 kDa)—used individually or in combination, on the physical stability of bovine polyclonal immunoglobulin G (pAb) in dry powders for inhalation (DPIs).

Methods:

A design of experiments (DoE) approach was employed to evaluate the effects of these excipients on residual moisture (RM), low-order aggregates (LOA), and high-order aggregates (HOA), immediately after spray-drying (T0) and after 10 months of storage at room temperature in a desiccator (T10).

Results:

All DPIs exhibited a high amorphous content and a favorable glass transition temperature, with RM decreasing over time. The combination of D-mannitol and dextran 10 kDa (DPI-MD) demonstrated the most effective stabilization, minimizing LOA and HOA formation at T0 and T10. Although the ternary mixture including D-sucrose (DPI-MSD) exhibited higher process stability, it was less stable over time compared to the binary mixture. The aerodynamic performance of these carrier-free DPIs, assessed via laser diffraction (% < 5 µm), ranged between 51 ± 3 (DPI-MD) and 67 ± 4 (DPI-MSD), and a Next Generation Impactor confirmed that formulations produced aerosols with suitable size distribution and fine particle fractions (FPFn up to 71 ± 5% for DPI-MSD), appropriate for deep pulmonary deposition.

Data Summary:

Residual moisture decreased over time across all formulations. Fine particle fractions (FPFn) reached up to 71 ± 5% for DPI-MSD, while particle size (% < 5 µm) ranged from 51 ± 3% (DPI-MD) to 67 ± 4% (DPI-MSD). Aggregate formation (LOA and HOA) was lowest in DPI-MD at both T0 and T10.

Conclusions:

These findings highlight the importance of combining excipients with complementary physical properties to achieve robust protein stabilization. The DPI-MD emerged as the most promising candidate for pAb lung delivery, balancing protein integrity, powder stability, and aerodynamic efficiency.

Practical Significance:

The optimized DPI-MD formulation offers a viable strategy for developing stable, inhalable dry powder antibody therapies, enabling effective deep lung deposition and long-term storage without compromising protein structure or function.