In the last decade, biological drugs have rapidly proliferated and have now become an important therapeutic modality. This is because of their high potency, high specificity and desirable safety profile. The majority of biological drugs are peptide- and protein-based therapeutics with poor oral bioavailability. They are normally administered by parenteral injection (with a very few exceptions). Pulmonary delivery is an attractive non-invasive alternative route of administration for local and systemic delivery of biologics with immense potential to treat various diseases, including diabetes, cystic fibrosis, respiratory viral infection and asthma, etc. The massive surface area and extensive vascularisation in the lungs enable rapid absorption and fast onset of action. Despite the benefits of pulmonary delivery, development of inhalable biological drug is a challenging task. There are various anatomical, physiological and immunological barriers that affect the therapeutic efficacy of inhaled formulations. This review assesses the characteristics of biological drugs and the barriers to pulmonary drug delivery. The main challenges in the formulation and inhalation devices are discussed, together with the possible strategies that can be applied to address these challenges. Current clinical developments in inhaled biological drugs for both local and systemic applications are also discussed to provide an insight for further research.

Endosomal Escape Pathways for Non-Viral Nucleic Acid Delivery Systems | InTechOpen, Published on: 2012-07-06. Authors: Wanling Liang and Jenny K. W. Lam

Nucleic acids could be used as therapeutic agents for the treatment of many different diseases, but poor delivery limits their clinical application. A series of pH-responsive amphipathic peptides containing histidine or 2,3-diaminopropionic acid (Dap) derivatives, LAH and LADap peptides, were investigated in this study as nucleic acid carriers for the treatment of respiratory infectious disease. LAH and LADap peptides are cationic, amphipathic pH-responsive peptides. The major attractive property of these peptides is their ability to promote endosomal escape, hence enhance transfection efficiency. Both LAH and LADap peptides were able to form complexes with DNA and small interfering RNA (siRNA) through electrostatic interaction and facilitated cellular uptake via endocytosis. In acidic environments (e.g. in endosomes and lysosomes), the peptides were released from the complexes and changed their conformational structures to display membrane-destabilizing activity. Subsequently, nucleic acids were released from the endosomal/lysosomal compartments into the cytoplasm with improved transfection efficiency. These peptides were effective in transferring DNA and siRNA in various cell lines including human lung epithelial cells. In addition, they were less toxic than the commercially available lipid-based transfection reagent LipofectamineTM 2000. LAH4-L1 and LADap(Me)6-L1 were the two most efficient peptides of the LAH and LADap peptide series respectively, and were selected for further formulation development for pulmonary delivery. To determine the optimal carrier for delivering nucleic acids to the lungs, bronchoalveolar lavage fluid (BALF) was used as a model of airway surface liquid in the in vitro transfection experiments. High transfection efficiency was maintained with LADap(Me)6-L1 peptide, making it a promising vector for pulmonary nucleic acid delivery. Two drying methods, spray drying and spray freeze drying, were investigated to prepare dry powder formulation containing pH-responsive peptides and nucleic acids for inhalation. Both methods could produce powders with desirable aerodynamic properties for inhalation. The physical integrity and biological activity of the nucleic acids were also successfully retained. Overall, SD powders performed better than SFD powders, suggesting that spray drying was a more suitable method to produce inhalable nucleic acid formulation. The clinical potential of the spray-dried powder formulation the peptide-based nucleic acid delivery system was further investigated for the treatment of lung diseases. siRNA has considerable therapeutic potential for treating respiratory infectious diseases including influenza. By introducing siRNA targeting the conserved region of viral genes encoding nucleocapsid protein (NP), viral replication can be inhibited in mammalian cells. Powder formulations containing antiviral siRNA against H1N1 influenza virus and pH-responsive peptides were produced by spray drying. The SD powders were characterized and found to be suitable for inhalation with good stability. The formulations mediated highly effective in vitro delivery of antiviral siRNA into mammalian lung epithelial cells, leading to significant inhibition of viral replication when the transfected cells were subsequently challenged with H1N1 influenza virus. SD siRNA powders containing pH-responsive peptides are promising inhalable formulations to deliver antiviral siRNA against influenza and are readily adapted for the treatment of other respiratory diseases.published_or_final_versionPharmacology and PharmacyDoctoralDoctor of Philosoph

Background Small interfering RNA (siRNA) is a potentially effective therapeutic agent for the treatment of a wide range of respiratory diseases such as cancer and infection by silencing the disease-associated gene through RNA interference. There are several important barriers need to overcome before siRNA could be widely used in the clinic, including the safe and effective delivery of siRNA to the target sites. There are limited studies reported the development of siRNA therapeutics as inhaled powder formulation. The aim of this study was to develop an inhalable siRNA formulation with good aerodynamic properties for effective lung deposition, while preserving the integrity and biological activities of the siRNA therapeutics. Methods Spray drying (SD) and spray freeze drying (SFD) technologies were employed to produce dry powder of siRNA of different formulations (different excipients and solute concentrations) under different operation parameters (different temperature and feed rate). Each formulation contained 2% (w/w) of siRNA. The SD or SFD powders were characterised for the siRNA integrity (gel retardation assay and high performance liquid chromatography), morphology (scanning electron microscopy), aerosol performance (cascade impactor) and transfection efficiency. Results For the SD formulation, the incorporation of L-leucine (serve as a dispersion enhancer) led to the production of particles with corrugated surface, which effectively reduce cohesion between particles, thereby improving powder dispersion. According to the aerosol performance study, the fine particle fraction (FPF, the percentage of powders that can be effectively deposited in the lung) of the optimal SD formulation was around 45%, suggesting good lung deposition. On the other hand, SFD produced spherical, porous particles with low density and large geometric diameter, which could also improve powder dispersion. The FPF of the optimal SFD formulation was around 40%, which was comparable to that of the SD formulation. In addition, the integrity and biological activity of siRNA were well-preserved in both SD and SFD formulations. Conclusions Both SD and SFD technologies can be used to produce inhalable carrier-free siRNA formulation. The siRNA remained intact and the biological activities of the siRNA powders were successfully preserved. Both formulations will be further optimized in the subsequent formulation development for clinical applications.