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28 February 2025 Inhalation Our work aims to enhance preparedness for future pandemics caused by betacoronaviruses. e adapt- ability of siRNA-based therapies, due to the ease of modifying base sequences, represents a signifi- cant advantage. e development of polymer-based nanocarriers thereby provides a robust foundation for the pulmonary treatment of infected individuals, potentially mitigating the impact of future viral out- breaks. It also represents a significant step forward in the field of antiviral therapies. As we continue to refine and test our formulation, we aim to provide a robust, scalable solution that can be deployed rapidly in response to future outbreaks. Ultimately, the success of our inhalable siRNA for- mulation could transform the way we approach pan- demic preparedness, providing a powerful means of both treating and preventing viral infections. We hope to contribute our part to a safer, healthier future, where society is better-equipped to handle the challenges of emerging infectious diseases. Acknowledgements e authors thank the Volkswagen Foundation (Volkswagen Stiftung AZ-9A872), German Research Foundation (DFG ME 4874/3-1) and European Research Council (ERC-2022-COG-101088587) for generous financial support. References 1. WHO. Number of COVID-19 deaths reported to WHO (cumulative total). 2024 10.04.2024]; https:// data.who.int/dashboards/covid19/deaths?n=c. 2. Hebbani, A.V., et al., COVID-19: Comprehen- sive review on mutations and current vaccines. Arch Microbiol, 2021. 204(1): p. 8. 3. Mehta, A., et al., siRNA therapeutics against respi- ratory viral infections—What have we learned for potential COVID-19 therapies? Adv Healthc Mater, 2021. 10(7): p. e2001650. 4. Reperant, L.A., et al., AIDS, Avian flu, SARS, MERS, Ebola, Zika...what next? Vaccine, 2017. 35(35 Pt A): p. 4470-4474. 5. Kole, R., et al., RNA therapeutics: beyond RNA interference and antisense oligonucleotides. Nat Rev Drug Discov, 2012. 11(2): p. 125-140. 6. Ambike, S., et al., Targeting genomic SARS- CoV-2 RNA with siRNAs allows efficient inhibition of viral replication and spread. Nucleic Acids Res, 2022. 50(1): p. 333-349. 7. Jin, Y., et al., Spermine-based poly(β-amino ester)s for siRNA delivery against mutated KRAS in lung cancer. Mol Pharm, 2023. 20(9): p. 4505-4516. 8. Adams, F., et al., Pulmonary siRNA delivery with sophisticated amphiphilic poly(spermine acryl- amides) for the treatment of lung fibrosis. Small, 2023: p. e2308775. pulmonary epithelium studies but lacks functional tight junctions [40]. To better replicate lung physiology, the ALI model was developed, where lung epithelial cells are seeded on a porous membrane and exposed to air on the apical side to induce differentiation, mimicking in vivo conditions. is method ensures that apically administered drugs are not influenced by the culture medium and must overcome physiological barriers such as mucus and surfactant. e ALI model's abil- ity to replicate the air-liquid interface of the lung tis- sue is significant for understanding drug delivery and absorption in respiratory diseases [40, 41]. Additionally, human precision cut lung slices (hPCLS) offer a sophisticated ex vivo 3D model that closely mimics in situ lung conditions. ey serve as a bridge between in vitro and in vivo studies, fol- lowing the 3R principles to provide reliable data for correlation. Generated using detailed protocols [42], hPCLS can be cultured for up to 14 days, maintaining alveolar microstructure for various dis- ease studies, including asthma, COPD, idiopathic pulmonary fibrosis, and infections with numerous pathogens, including betacoronaviruses [43, 44]. ese slices allow researchers to explore the effects of drugs in a controlled environment, ensuring that findings can be effectively translated to human treatments. e use of hPCLS emphasizes the importance of replicating proper physiological con- ditions, such as those found in the human lungs, to ensure accurate and relevant research outcomes. As reflected in Figure 3, our group already visual- ized the transfectability of polyspermine polyplexes towards hPCLS, which lays the basis for trans- lation to human administration. is model has been instrumental in studying the localized infec- tion processes and evaluating potential therapeutic interventions, thereby providing a crucial platform for advancing respiratory disease treatments [45]. Conclusion and outlook In recent years, society has faced the harsh realities of a pandemic, resulting in significant loss of life, long- term health impacts and negative effects on men- tal health, with a marked increase in cases of severe depression and anxiety [46]. e lockdowns further compounded these issues by preventing visits to loved ones and disrupting normal educational activities. Here we present a concept of an inhalable siRNA for- mulation that is effective against the broadest possible spectrum of betacoronaviruses. e intended drug carrier is formed by PBAEs containing spermine and oleylamine side chains, ensuring effective encapsula- tion and reducing toxicity, which can additionally be coupled to an ACE-2 receptor antibody or similar targeting strategies for active targeting.