(497a) Spray-Dried Protein Particles for Dry Powder Inhalation

Background and Motivation:

When targeting respiratory diseases, the direct delivery of active pharmaceutical ingredients to the lungs presents various advantages, i.e., lower doses, fewer side effects, etc. Dry Powder Inhalers (DPIs) are easy to use and deliver drug aerosols directly to the lungs. To reach the lungs, it is generally agreed that drug particles must present an aerodynamic diameter (da) between 1–5 µm. Spray-drying (SD) is a well-known technique that allows the production of micron-sized particles appropriate for inhalation. L-leucine (Leu) is often reported as an acceptable excipient to yield flowable particles that can be aerosolized without using carriers¹. This study aims toward the engineering of inhalable particles of a protein drug in the presence of Leu via spray drying. To that end, miniaturized drying (MD) was performed via sessile droplet drying. Based on the MS results, a Design of Experiment (DoE) was carried out on a Büchi-290 spray dryer, where inhalable particles of protein X and Leu were produced at different weight ratios. Furthermore, of this DoE, the 5 best formulations were selected and larger batches were spray-dried for detailed analyses of the formulations.

Materials and Methods:

The protein X used was applied in a concentration of 5%ww for the miniaturized and spray-drying experiments. Before the SD-DoE experiments (5 factors, two levels), miniaturized experiments using single droplet drying were performed to select an appropriate Leu ratio. Concerning the process factors, the inlet temperature (110-150°C), pump setting (2-4 mL/min), aspirator setting (80-100%), and airflow (400-800 L/min) were studied. The responses evaluated were the particle size span, SMD (Sauter Mean Diameter), VMD (Volume Mean Diameter), da (aerodynamic diameter ²), monomer and aggregate content, yield, and moisture content. Of these 11 formulations, the 5 best according to da, were chosen for analysis by Next Generation Impactor (NGI) for in vitro aerosolization and by the Lowry assay for protein quantification.

Results and Discussion:

The details of the selected DoE runs are summarized in Table 1.

In the MD, higher Leu content (0-20% w/w, based on protein mass used) increased protein X aggregation, showing the highest aggregation of 7.41% for Leu used at 20%w/w (figure 1 A). At the same time, the droplet shapes became very flat with the highest Leu content (figure 1 D). Likewise, a maximum Leu content of 10% w/w was selected for the DoE spray-drying experiments.

The DoE showed the best results in terms of in vitro aerosolization performance and protein aggregation for the experiments N8 and N11. As observed in Figures 1B and C, these samples resulted in 98.5% ED (N8) and 45-50% FPF (N11). In contrast, the lowest performance was observed with the samples N6 and N1, resulting in 95% ED and only 25-35% FPF.

Hence, the samples N8 and N11 were selected for the performance of stability studies over 3 months at the following two conditions: cooled condition at 2-8°C and normal conditions at 25°C and 60% RH. After 1 month, both samples were still amorphous and no significant increase in aggregation (5.17% aggregates) could be observed when compared to 4.74 – 4.8% at the beginning of the study. The moisture content did not change tremendously among the 5 different formulations analyzed and always varies between 5 and 7%.

Implications and Outlook:

Inhalable protein particles were generated with 87-93% yield via spray-drying and a relatively similar moisture content. L-leucine showed to be critical to stabilizing the protein and guaranteeing a good process yield. The produced particles show a great potential for inhalation. Especially, samples N8 and N11 showed very good ED and FPF and hence the stability profiles are currently being.

Literature:

(1) Alhajj, N.; O’Reilly, N. J.; Cathcart, H. Leucine as an Excipient in Spray Dried Powder for Inhalation. Drug Discov. Today 2021, 26 (10). https://doi.org/10.1016/j.drudis.2021.04.009.

(2) De Boer, A. H.; Gjaltema, D.; Hagedoorn, P.; Frijlink, H. W. Characterization of Inhalation Aerosols: A Critical Evaluation of Cascade Impactor Analysis and Laser Diffraction Technique. Int. J. Pharm. 2002, 249 (1–2), 219–231. https://doi.org/10.1016/S0378-5173(02)00526-4.