Tobramycin nanoformulation for chronic pulmonary infections: From drug product definition to scale-up for preclinical evaluation.

Cystic fibrosis (CF) is characterized by abnormal mucus hydration due to a defective CF Transmembrane Regulator (CFTR) protein, leading to the production of difficult-to-clear mucus. This causes airflow obstruction, recurrent infections, and respiratory complications. Chronic lung infections are the leading cause of death for CF patients and inhaled tobramycin is the first-in-line antibiotic treatment against these infections, mainly caused by Pseudomonas aeruginosa in adult patients. KuDa-tob, a nanoformulation of tobramycin (tob) as the active ingredient and dextran single chain nanoparticles, a drug carrier platform (KuDa) as an excipient, has been developed. The neutralization of the positive charges of the drug by KuDa nanoparticles facilitates its diffusion through the mucus and biofilm, reaching the bacteria. The polar interactions existing between tobramycin and KuDa have been thoroughly characterized by electrophoresis (ζ-potential) and diffusion experiments (diffusion ordered spectroscopy and Taylor dispersion analysis) demonstrating that up to 40 wt% tobramycin could be loaded into the KuDa-tob nanoformulation. The drug product was developed following Quality by Design (QbD) principles. Critical quality attributes (CQAs), critical process parameters (CPPs) and critical material attributes (CMAs) have been defined to obtain a robust production process that was then scaled-up to 40 g, allowing the production of KuDa-tob for further preclinical evaluation. Finally, the final pharmaceutical form of KuDa-tob was defined based on stability studies, and nebulization assays showed that the aerosols generated by reconstituted KuDa-tob were in the ideal range size for lung deposition (Median Mass Aerodynamic Diameter - MMAD - 2.2 μm).