Development of an inhalable dry powder formulation for inhibition of SARS-CoV-2

Coronaviruses, including SARS-CoV-2, can cause significant lung damage and may result in multiple organ failure. The severity of COVID-19 is determined by the virus's entry into lung tissue and subsequent replication. This entry is facilitated by the angiotensin-converting enzyme 2 (ACE2) in combination with the serine protease TMPRSS2, which is a critical step. To reduce viral replication, it is necessary to prevent the uptake of the virus directly at the main route of transmission, which is the deposition of the virus as an aerosol in the respiratory tract. To reduce viral uptake into lung cells, an inhalable dry powder formulation was developed. The formulation contains camostat, a clinically proven serine protease inhibitor that inhibits the cellular uptake mechanisms on the lung surface. Camostat was spray-dried together with the mucolytic agent N-acetylcysteine to produce co-amorphous microparticles with sufficient solubility after deposition. Microparticles with properties suited for deposition in the deep part of the respiratory tract can be produced by using appropriate spray-drying parameters. The use of L-leucine enabled suitable aerodynamic properties and storage stability due to reduced interaction with environmental water. The geometric particle diameter, determined using laser light diffraction, decreased with L-leucine content which was found forming a partially crystalline L-leucine shell. The disintegration behavior of the microparticle formulation simulated under lung-like conditions indicated fast disintegration. A pseudo-viral in vitro assay demonstrated low acute toxicity in combination with a high activity. Cell viability and proliferation were not affected by camostat concentrations up to 11.1 μg/mL. The IC50 values of the two dry powder formulations tested on a HEK293T/ACE2-TMPRSS2 cell line were 0.008 μg/mL and 0.019 μg/mL, respectively, which is at least 100 times lower than the cytotoxic concentration. This dry powder formulation serves as a prototype microparticle matrix for incorporating nanoscale drug carriers in the future.