Spray-Dried Monoclonal Antibody Suspension for High-Concentration and Low-Viscosity Subcutaneous Injection.

Administration of highly concentrated monoclonal antibodies (mAbs) through injection is often not possible as the viscosity can be readily above 50 mPa·s when the concentration exceeds 150 mg/mL. Besides, highly concentrated mAb solutions always exhibit increased aggregation propensity and lower stability, which raise the difficulty for the successful development of highly concentrated mAb formulations. We hereby explored the possibility of suspension as another formulation form for high-concentration proteins to reduce viscosity and maintain stability. Specifically, we demonstrated that spray drying can serve as a process to prepare particles for suspension. Particles prepared from formulations with different mAb/trehalose mass ratios displayed good physical stability and antibody binding affinity, as indicated by circular dichroism, fluorescence spectroscopy, and surface plasmon resonance (SPR)-based bioassay analyses. During spray drying, a surface tension-dominated enrichment of mAb on the particle surface was observed, but this did not show a significant negative impact on mAb stability. Spray-dried particles were subsequently suspended into benzyl benzoate, and the resulting suspension showed good stability and a lower viscosity when compared to its counterpart solution. Furthermore, mAbs recovered from the suspension maintained their conformational structure. Our study demonstrated that the suspension displayed low viscosity and good physical stability, so it may offer novel opportunities for the preparation of highly concentrated protein formulations.

Water-Resistant Drug-Polymer Interaction Contributes to the Formation of Nano-Species during the Dissolution of Felodipine Amorphous Solid Dispersions.

Drug-polymer interactions are of great importance in amorphous solid dispersion (ASD) formulation for both dissolution performance and physical stability considerations. In this work, three felodipine ASD systems with drug loading ranging from 5 to 20% were prepared using PVP, PVP-VA, or HPMC-AS as the polymer matrix. The amorphization and homogeneity were confirmed by differential scanning calorimetry and powder X-ray diffraction. The intrinsic dissolution behavior of these ASDs was studied in 0.05 M HCl and phosphate-buffered saline (PBS) (pH 6.5). In 0.05 M HCl, PVP-VA ASDs with low drug loading (<15%) showed rapid dissolution accompanied with nano-species generation, while in the PVP system, rapid dissolution and nano-species generation were observed only when drug loading was less than 10%, and HPMC-AS ASDs always released slowly with no nano-species formation. In PBS, PVP-VA ASDs with drug loading less than 10% showed rapid dissolution accompanied with nano-species generation, while for PVP ASDs, rapid dissolution and nano-species generation were observed only when drug loading was 5%. However, 20% drug loading HPMC-AS ASDs exhibited rapid dissolution of felodipine and nano-species generation. When the drug loading was above the transition point of PVP-VA ASDs and PVP ASDs, the release rate was significantly lowered, and no nano-species was generated. To understand this phenomenon, drug-polymer interactions were studied using the melting point depression method and the Flory-Huggins model fitting. The Flory-Huggins interaction parameters (χ) for felodipine/HPMC-AS, felodipine/PVP, and felodipine/PVP-VA were determined to be 0.62 ± 0.07, -0.55 ± 0.20, and -1.02 ± 0.21, respectively, indicating the existence of the strongest attractive molecular interaction between felodipine and PVP-VA, followed by felodipine/PVP, but not in felodipine/HPMC-AS. Furthermore, dynamic vapor sorption further revealed that the molecular interactions between felodipine and PVP or PVP-VA were resistant to water. We concluded that water-resistant drug-polymer interactions in felodipine/polymer systems were responsible for the formation of nano-species, which further facilitated the rapid initial drug dissolution.

Polymer-Mediated Drug Supersaturation Controlled by Drug-Polymer Interactions Persisting in an Aqueous Environment.

We investigated the drug-polymer interactions in nonaqueous and aqueous environments between a poorly water-soluble drug, BAY1161909 (909), and two commonly used polymers in amorphous solid dispersions, i.e., PVP and HPMC-AS. In an nonaqueous state, with a drug-polymer Flory-Huggins interaction parameter, solution NMR and FT-IR results revealed that strong specific interactions existed between 909 and PVP, while not between 909 and HPMC-AS. After prolonged moisture exposure under 95% RH, 909/PVP intermolecular interaction no longer existed, while hydrophobic interaction between 909 and HPMC-AS occurred and persisted. In an aqueous supersaturation study of 909, codissolved PVP significantly outperformed predissolved PVP in maintaining 909 supersaturation. We hypothesized that the codissolved PVP formed a specific interaction with 909, and thus, it was able to prolong 909 supersaturation before disruption of the interaction in aqueous medium, while predissolved PVP formed hydrogen bonds with water, and thus, it was no longer able to form specific interactions with 909 to prolong its supersaturation. In contrast, HPMC-AS effectively mediated 909 supersaturation through hydrophobic interaction, which became pronounced in an aqueous environment and was independent of how HPMC-AS was added. This hypothesis was supported by dynamic light scattering analysis, wherein the formation of nanosized drug/polymer aggregations was found to be correlating with the supersaturation of 909. In summary, we concluded that polymer-mediated drug supersaturation was controlled by drug-polymer interactions persisting in an aqueous environment. Therefore, the physical nature of the drug-polymer interaction as well as the dissolution kinetic of the drug and polymer are all critically important to achieve an optimal ASD formulation design.

Maintaining Supersaturation of Nimodipine by PVP with or without the Presence of Sodium Lauryl Sulfate and Sodium Taurocholate.

Amorphous solid dispersion (ASD) is one of the most versatile supersaturating drug delivery systems to improve the dissolution rate and oral bioavailability of poorly water-soluble drugs. PVP based ASD formulation of nimodipine (NMD) has been marketed and effectively used in clinic for nearly 30 years, yet the mechanism by which PVP maintains the supersaturation and subsequently improves the bioavailability of NMD was rarely investigated. In this research, we first studied the molecular interactions between NMD and PVP by solution NMR, using CDCl3 as the solvent, and the drug-polymer Flory-Huggins interaction parameter. No strong specific interaction between PVP and NMD was detected in the nonaqueous state. However, we observed that aqueous supersaturation of NMD could be significantly maintained by PVP, presumably due to the hydrophobic interactions between the hydrophobic moieties of PVP and NMD in aqueous medium. This hypothesis was supported by dynamic light scattering (DLS) and supersaturation experiments in the presence of different surfactants. DLS revealed the formation of NMD/PVP aggregates when NMD was supersaturated, suggesting the formation of hydrophobic interactions between the drug and polymer. The addition of surfactants, sodium lauryl sulfate (SLS) or sodium taurocholate (NaTC), into PVP maintained that NMD supersaturation demonstrated different effects: SLS could only improve NMD supersaturation with concentration above its critical aggregation concentration (CAC) value while not with lower concentration. Nevertheless, NaTC could prolong NMD supersaturation independent of concentration, with lower concentration outperformed higher concentration. We attribute these observations to PVP-surfactant interactions and the formation of PVP/surfactant complexes. In summary, despite the lack of specific interactions in the nonaqueous state, NMD aqueous supersaturation in the presence of PVP was attained by hydrophobic interactions between the hydrophobic moieties of NMD and PVP. This hydrophobic interaction could be disrupted by surfactants, which interact with PVP competitively, thus hindering the capability of PVP to maintain NMD supersaturation. Therefore, caution is needed when evaluating such ASDs in vitro and in vivo when various surfactants are present either in the formulation or in the surrounding medium.

Inhalable PLGA microspheres: Tunable lung retention and systemic exposure via polyethylene glycol modification.

Polyethylene glycol (PEG) modification is one of the promising approaches to overcome both mucus and alveolar macrophage uptake barriers in the deep lung for sustained therapy of pulmonary diseases such as asthma. To investigate the feasibility of using PEG-modified microspheres to bypass both barriers, we prepared a collection of polyethylene glycol-distearoyl glycero-phosphoethanolamine (PEG-DSPE)-modified poly (lactide-co-glycolide) (PLGA) microspheres bearing specific PEG molecular weights (0.75, 2, 5, and 10 kDa) and PEG-DSPE/PLGA molar ratios (0.25:1 and 1:1). Drug release, mucus penetration, and macrophage uptake were evaluated in vitro, and the corresponding in vivo activities of microspheres in rats were investigated. It was found that the PEG2000-DSPE/PLGA 1:1 group showed enhanced mucus permeability and reduced macrophage uptake in vitro compared to the PEG2000-DSPE/PLGA 0.25:1 group. At high PEG molar ratios, only the PEG 2000-based group showed significantly prolonged lung retention in vivo compared to the control group. The systemic exposure of the PEG2000-DSPE/PLGA 1:1 group was significantly lower than that of the PEG2000-DSPE/PLGA 0.25:1 group (39% of AUC reduction). Additionally, when using the same molar ratio of 1:1, the PEG 2000 group significantly lowered the systemic drug exposure compared to that of the PEG 5000 and 10000 groups (48% and 33% of AUC reduction, respectively), thus making it a promising sustained lung delivery candidate for pulmonary disease treatment.

Engineering large porous microparticles with tailored porosity and sustained drug release behavior for inhalation.

Sustained drug delivery is considered as an effective strategy to improve the treatment of local lung diseases. In this context, inhalation administration of large porous microparticles (LPPs) represents promising prospects. However, one major challenge with said delivery technology is to control the drug release pattern (especially to decrease the burst release) while maintaining a low mass density/high porosity, which is of high significance for the aerodynamic behavior of LPP systems. Here, we show how to engineer drug-loaded, biodegradable LPPs with varying microstructure by means of a premix membrane emulsification-solvent evaporation (PME-SE) method using poly(vinyl pyrrolidone) (PVP) as the pore former. The influence of PVP concentration on the physicochemical properties, in-vitro drug release behavior and in-vitro aerodynamic performance of the drug-loaded microparticles was tested. We demonstrated that the PME-SE technique led to LPPs with favorable pore distribution characteristics (i.e., low external but high internal porosity) as a function of the PVP concentration. In general, more PVP conditioned a larger discrepancy of the internal vs. external porosity. When the external porosity of the LPP formulation (15% of PVP during the manufacturing process) was less than 3%, the burst release of the embedded drug was significantly reduced compared to LPPs prepared by a "conventional" emulsification solvent evaporation method. All the formulations prepared by the PME-SE method had aerodynamic properties suitable for inhalation. This is the first report indicating that the microstructure of LPPs can be tailored using the PME-SE technology with PVP as a suitable pore former. Doing so, we designed LPP formulations having full control over the drug release kinetics and aerodynamic behavior.

In vitro-in vivo correlation of inhalable budesonide-loaded large porous particles for sustained treatment regimen of asthma.

Large porous particles (LPPs) are well-known vehicles for drug delivery to the lungs. However, it remains uncertain whether or to which extent the in vitro drug release behavior of LPPs can be predictive of their in vivo performance (e.g., systemic exposure and therapeutic efficacy). With regard to this, three budesonide-loaded LPP formulations with identical composition but distinct in vitro drug release profiles were studied in vivo for their pharmacokinetic and pharmacodynamic behavior after delivery to rat lung, and finally, an in vitro/in vivo correlation (IVIVC) was established. All formulations reduced approximately 75% of the uptake by RAW264.7 macrophages compared with budesonide/lactose physical mixture and showed a drug release-dependent retention behavior in the lungs of rats. Likewise, the highest budesonide plasma concentration was measured for the formulation revealing the fastest in vitro drug release. After deconvolution of the plasma concentration/time profiles, the calculated in vivo drug release data were successfully utilized for a point-to-point IVIVC with the in vitro release profiles and the predictability of the developed IVIVC was acceptable. Finally, effective therapy was observed in an allergic asthma rat model for the sustained drug release formulations. Overall, the obtained in vitro results correlate well with the systemic drug exposure and the therapeutic performance of the investigated lung-delivered formulations, which can provide an experimental basis for IVIVC development in the pulmonary-controlled delivery system. STATEMENT OF SIGNIFICANCE: Large porous particles (LPPs) are well-known vehicles for drug delivery to the lungs. However, it remains uncertain whether or to which extent the in vitro drug release behavior of LPPs can be predicted by their in vivo performance (e.g., systemic exposure and therapeutic efficacy). With regard to this, three budesonide-loaded PLGA-based LPP formulations with identical composition but distinct in vitro drug release profiles were studied in vivo for their pharmacokinetic and pharmacodynamic behavior, and finally, an in vitro/in vivo correlation (IVIVC) was established. It was demonstrated that the influence of the in vitro drug release profile was obvious during lung retention, systemic exposure, and therapeutic efficacy measurements. An IVIVC (Level A) was successfully established for the budesonide-loaded LPPs delivered to the airspace of rats for the first time. Taken together, the present work will clearly support research and development activities in the field of controlled drug delivery to the lungs.

Phospholipid-modified poly(lactide-co-glycolide) microparticles for tuning the interaction with alveolar macrophages: In vitro and in vivo assessment.

Controlled drug delivery to the lungs is promising with plentiful advantages over current rapid release products. However, alveolar macrophage clearance has severely hindered the application of inhaled controlled release preparations. The objective of our study was to explore the feasibility to decorate poly(lactide-co-glycolide) (PLGA) microparticles with endogenous phospholipids found in the deep lungs, thus, to regulate the interplay with alveolar macrophages. The influence of the phospholipid amount and type on macrophage uptake of PLGA microparticles was investigated systemically under both in vitro (RAW264.7 and NR8383) and in vivo conditions. The uptake rate (k) by macrophages, in vivo elimination rate from the bronchoalveolar lavage fluid (k') and elimination rate from the whole lung (k″) were used as parameters for evaluation. Our data showed that a modification with dipalmitoyl phosphatidylcholine (DPPC) enhanced the macrophage phagocytosis significantly over the unmodified counterparts. Thereafter, using the same modification ratio, remarkable enhancement of macrophage uptake was found in the presence of different types of other phospholipids, especially with distearoyl phosphatidylethanolamine (DSPE). When replaced by a poly(ethylene glycol)-conjugated version of DSPE the uptake of the modified PLGA microparticles was reduced by ~200%. Meanwhile, the drug content in the lung tissue was improved by 3-fold (area under the curve value). Finally, it was possible to establish a correlation between in vitro phagocytosis and in vivo lung elimination rate for the investigated formulations. Overall, our study demonstrated that phospholipids play an important role in modulating the clearance of microparticle-based drug delivery vehicles, which gives a meaningful insight into the development of prolonged drug release system for inhalation.