(T1430-03-15) FluoriPack Technology: A Non-aqueous Emulsification Process to Develop Polymeric Microspheres for Sustained Delivery of Biologics

Purpose: Over the past decade, there has been an exponential rise in development and commercialization of therapeutics such as proteins, monoclonal antibodies, etc. (biologics). These modalities are formulated as systemic injections that are administered intravenously or subcutaneously, and in comparison to long acting injectables, require more frequent dosing to maintain therapeutic efficacy. This leads to off-target effects and poor patient compliance. To overcome these challenges, sustained release drug delivery platforms may be developed to protect the biologic drug substance, avoid systemic exposure, and provide extended release of therapeutic concentrations, resulting in an improved pharmacokinetic profile. One such technology is Polymeric Microspheres (MS), which encapsulates drug substance within, thereby protecting it from degradation and releasing the encapsulated drug overtime at a specific rate. The rate of drug release is dependent on polymer swelling, polymer degradation rate, and drug diffusion out of the polymeric matrix and thus tuned to match the desired Target Product Profile (TPP). Conventionally, MS have been formulated as water-in-oil-in-water (w/o/w) emulsions which have worked well for small molecules and peptides. However, biologics have faced difficulty in achieving high drug loading via w/o/w microsphere manufacturing process, and are prone to denaturation when exposed to the organic phase. With an aim to develop a suitable platform for biologics, we have developed an in-house non-aqueous emulsification platform to encapsulate solid biologics into MS. The “FluoriPack” (Fluorinated Packing) system is a solid/hydrocarbon/fluorocarbon system that results in biologic encapsulated MS with high loading, minimal drug degradation, and reduced burst release profile.

Methods: To develop MS using FluoriPack system, a protein (97kDa) was encapsulated in polyester (PE) based microspheres. The protein was first spray dried using an optimized process. Spray Dried Protein (SDP) was characterized for particle morphology and size distribution. Following this, 5-25% w/w SDP was dispersed in a solution of 10-40% w/v PE in dichloromethane (DCM) as the Solid in Hydrocarbon phase (S/H). S/H phase was emulsified with Fluorinert-40 (FC-40) and PicoSurf (fluorosurfactant) which is an inert non-aqueous fluorocarbon phase. Bulk emulsification was executed via homogenization of both phases for 60 seconds and followed by evaporation of DCM. Protein loaded MS were evaluated for physical characteristics, in-vitro release, and accelerated stability. In addition, released protein will be tested for integrity and potency to ensure optimum performance post encapsulation process.

Results: Spray drying resulted in toroid shaped protein (Fig. 1A) particles with Dv(50) of 11.25 ± 1.63 µm. Size exclusion chromatography analysis on SDP revealed that the spray drying process resulted in a slight increase in protein aggregation (ΔHMW = +0.92%) and remained within specification. Successful implementation of anhydrous FluoriPack technology (S/H/F) led to production of SDP loaded PE MS with smooth surface characteristics void of porous channels (Fig. 1B). On the contrary, PE MS produced via conventional aqueous emulsification resulted in poor SDP loading efficiency which may be attributed to the porous channels (data not shown). MS size was significantly changed by the concentration of PE in the hydrocarbon phase. Higher concentration of PE (40% w/v) resulted in a Dv(50) of 28.85 ± 2.05 µm (Fig. 1C), while MS manufactured using 10% w/v PE had an average size of ~4 µm. On the other hand, % SDP loading directly influenced the extent of protein on the surface of the particles. Higher SDP (25% w/w) incorporated in the emulsification step resulted in higher amount of SDP on the surface of MS as compared to lower SDP loading (5% w/w). With this technology, we have achieved an encapsulation efficiency of 72% with a 3.6% w/w loading of SDP. To remove unencapsulated SDP, two wash solutions were evaluated: anhydrous wash with FC-40 and an aqueous wash with 1x PBS pH 7.4. The anhydrous wash strategy did not efficiently wash out unencapsulated SDP as indicated by an extreme burst release of SDP within 1 hour of soaking in 1x PBS pH 7.4 (55% of total protein). Particles washed with 1x PBS resulted in a 10% release of total protein within 1 hour, indicating efficient removal of surface adhered SDP (Fig. 1D). Moreover, aqueous washing did not create porous channels on MS surface that may facilitate faster release of SDP, as observed via SEM analysis.

Conclusion: Currently, there is an unmet need in the field of sustained delivery of biologics. This study introduces non-aqueous approaches that can be taken to exploit the benefits offered by microsphere drug delivery platforms. With proven encapsulation capability, FluoriPack can be a promising technology that allows for sustained delivery of biologics in the future. Studies are underway to understand loading efficiency of diverse modalities, release kinetics, formulation and process optimization, stability, and in-vivo safety and efficacy for microspheres.

References: Yiming Zhao and Hunter Chen, Sustained release formulations using non-aqueous emulsions. US1173079

Acknowledgements: Authors acknowledge the contributions of Yiming Zhao in development of FluoriPack technology


Fig. 1: (A): SEM image of toroid shaped spray dried protein. (B) SEM of SDP loaded PE microspheres indicating an average size of 28 µm. (C) Size distribution of SDP loaded PE microspheres. (D) Burst release profiles for anhydrous wash and aqueous wash microspheres​