I-Jou Chang1, Fang-Ching Chao2, Jenny K. W. Lam3 & Chien-Ming Hsieh3,4
1School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, 110, Taiwan
2Drug Metabolism and Pharmacokinetics, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, SE-431 83 Gothenburg, Sweden
3Department of Pharmaceutics, School of Pharmacy, University College London, 29-39 Brunswick Square, WC1N 1AX, UK
4Medway School of Pharmacy, Central Avenue, University of Kent, Chatham Maritime, Canterbury, ME4 4TB, UK
Summary
In recent years, numerous studies have supported the potential of pulmonary delivery of small interfering RNA (siRNA) as a therapeutic strategy for lung cancer. The PEG12-KL4 peptide, comprising a synthetic 21-residue cationic peptide combined with 12 polyethylene glycol (PEG) monomers, is a mimic of surfactant protein B (SP-B) and has been developed for the pulmonary delivery of siRNA. While the mechanism of siRNA-induced gene inhibition is well recognized, a quantitative understanding of the factors governing the magnitude and duration of siRNA activity remains limited. Mechanistic pharmacokinetic/pharmacodynamic (PK/PD) modelling enables researchers to elucidate how key factors, for instance, siRNA properties, target mRNA turnover, and intracellular trafficking processes collectively influence gene knockdown dynamics. This study aims to develop a mechanistic intracellular PK/PD model to predict the PEG12KL4/siRNA nanocomplex-mediated gene silencing effects of three different doses of siRNA. PEG12-KL4 was used to transfect siRNA targeted at GAPDH into A549 cells. Real-time PCR was employed to characterize the kinetics of mRNA knockdown effects for model validation. The PK/PD model describing siRNA intracellular trafficking mechanisms is developed in MATLAB SimBiology, with only one of the parameters, the rate of nanocomplex internalization (kint), fitted in MATLAB SimBiology using a nonlinear regression function. The final simulated results showed a similar magnitude of observed mRNA knockdown level. This simplified yet predictive PK/PD model can potentially be extended to pulmonary delivery, as its mechanistic structure is adaptable to capture intercellular trafficking and endosomal escape, two pivotal barriers in lung-targeted delivery that must be addressed to inform formulation development and optimisation.