Distribution and suitability of pulmonary surfactants as a vehicle for topically applied antibodies in healthy and SARS-CoV-2 infected rodent lungs.

The use of natural pulmonary surfactants (PS) as a drug delivery vehicle for biologics is a more recent therapeutic modality. Herein, we tested different contents of PS regarding their physicochemical properties under stress conditions. The PS content of 12.25 mg/ml (Formulation B) showed desired properties such as an isotonic osmolality ∼300 mOsm/kg and an acceptable viscosity of 8.61 cSt, being lower than in commercially available PS solutions. Formulation B passed the specifications of surface lowering capacities of >80 % total lung capacity and physiologically desired formulation properties were independent of the antibody used in the composition. The identified formulation showed the capability of significantly increasing the oxygen saturation in ex vivo isolated perfused rat lungs, compared to a control and up to 30 min post lavage. In the in vivo setting, we showed that intratracheal administration of a human mAB with and without pulmonary surfactant led to higher amounts of delivered antibody within the alveolar tissue compared to intravenous administration. The antibody with the PS formulation remained longer in the alveolar tissues than the antibody without the PS formulation. Further, SARS-CoV-2 infected Golden Syrian hamsters showed that the intranasally applied antibody reached the site of infection in the alveoli and could be detected in the alveolar region 24 h after the last administration. With this work, we demonstrated that pulmonary surfactants can be used as a pulmonary drug delivery mechanism for antibodies and may subsequently improve the antibody efficacy by increasing the residence time at the desired site of action in the alveolar tissue.