Atossa Therapeutics Announces Successful In Vitro Testing Of Nasal Spray Formulation: AT-301 Inhibits SARS-CoV-2 Infectivity Of VERO Cells In Laboratory Culture

Results Support Development of Proprietary AT-301 Nasal Spray for COVID-19 Patients
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SEATTLE, July 15, 2020 (GLOBE NEWSWIRE) -- Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to discover and develop innovative medicines in areas of significant unmet medical need with a current focus on breast cancer and COVID-19, today announced successful results from  in vitro testing of AT-301, Atossa's proprietary COVID-19 nasal spray drug candidate. The preliminary study results show that AT-301 inhibits SARS-CoV-2 infectivity of VERO cells in a laboratory culture, which is the standard disease model used for initial screening of COVID-19 drug candidates. 

AT-301 is being developed with a nasal spray delivery mechanism because many COVID-19 patients are infected via the nasal passage. Collectively, the components of AT-301 are believed to help maintain a protective mucosal like layer within the nasal cavity with both anti-viral properties and protective mucosal like barrier that may lead to lower infectivity and reduced symptoms in COVID-19 patients due to their interference with the spike protein of the virus in the nasal cavity and upper respiratory tract.  Atossa's nasal spray formulation AT-301 is being designed to contain ingredients that can potentially block SARS-CoV-2 viral entry gene proteins in nasal epithelial cells by interfering with spike protein activation by host proteases, by masking receptor binding domains (RBD) via electrostatic mechanisms, and by providing a generalized mucoadhesive epithelial barrier. "The AT-301 formulation was designed to work like a mucosal vaccine, blocking entry of the virus into the cells to begin with and thus, hopefully, preventing a COVID-19 infection," said Dr. Steven Quay, Atossa's President and Chief Executive Officer. "With the finding that a particular cell found in the nasal cavity -- the goblet cell -- has among the highest expressions of viral entry genes 1, the concept of targeting the nasal cavity to block early SARS-CoV-2 infection made a lot of sense. And having invented two FDA-approved nasal spray products before founding Atossa, I am gratified to be able to bring this prior clinical and regulatory experience to bear on this devastating pandemic. We look forward to commencing a Phase 1 clinical study this quarter and reporting progress on this clinical development program." The purpose of these experiments was to mimic the virus's entry process in vitro by examining the infectivity of VERO monkey kidney cells by authentic SARS-CoV-2 virus particles. Although VERO cells are non-mucosal epithelial cells and therefore are more sensitive to cytotoxicity than would be expected of mucosal cells, they provide an established COVID-19 disease model system to judge in vitro efficacy. Serial dilutions of the AT-301 formulation were performed from 1 to 4 to 1 to 4096. SARS-CoV-2 was incubated in these serial dilutions for 1 hour at 37° C and then the mixture was added to the cells for one hour at 37° C. The mixture was then removed and fresh media added at 37° C and incubated overnight. The cells were then fixed with 10% formalin overnight and then the cells were permeabolized with 0.5% Triton X-100. H anti-SARS-2 N protein, 1 µg/mL, was added at room temperature for 1 hour. Anti-human-IgG-488 (green) tagged antibody was added at a 1:1000 dilution at room temperature for 1 hour. This allowed visualization of the production of the N protein inside cells as a green signal, the evidence that an infection had occurred. The experiments show that serial dilutions of the AT-301 nasal formulation, beginning with a 1 to 4 dilution and going to a 1 to 16 dilution were able to prevent N protein expression. Beginning at a 1 to 32 dilution the virus was able to infect the cells. There was minimal toxicity noted. The in vitro laboratory testing was conducted under contract at a leading academic research center that specializes in infectious disease research. Successful  in vitro tests do not guarantee similar results from  in vivo studies, including in human clinical trials. Additional safety and efficacy studies must be successfully completed and regulatory approvals must be obtained before AT-301 may be commercialized. Atossa has filed provisional patent applications with the U.S. Patent and Trademark Office directed to the formulation, manufacturing, and methods of use of AT-301. ABOUT ATOSSA THERAPEUTICS

Atossa Therapeutics, Inc. is a clinical-stage biopharmaceutical company seeking to discover and develop innovative medicines in areas of significant unmet medical need with a current focus on breast cancer and COVID-19. For more information, please visit www.atossatherapeutics.com. FORWARD-LOOKING STATEMENTS Forward-looking statements in this press release, which Atossa undertakes no obligation to update, are subject to risks and uncertainties that may cause actual results to differ materially from the anticipated or estimated future results, including the risks and uncertainties associated with any variation between interim and final clinical results, whether  in vitro test results will also be achieved in  in vivo studies, including human clinical studies, actions by and interactions with the FDA, the outcome or timing of regulatory approvals needed by Atossa including those needed to commence human clinical studies of AT-301, lower than anticipated rate of patient enrollment, estimated market size of drugs under development, the safety and efficacy of Atossa's products, performance of clinical research organizations and investigators, obstacles resulting from proprietary rights held by others such as patent rights, and other risks detailed from time to time in Atossa's filings with the Securities and Exchange Commission, including without limitation its periodic reports on Form 10-K and 10-Q, each as amended and supplemented from time to time. Company Contact: Atossa Therapeutics, Inc. Kyle Guse, CFO and General Counsel Office: 866 893-4927 kyle.guse@atossainc.com Investor Relations Contact: Core IR Office: (516) 222-2560 ir@atossainc.com Source: Atossa Therapeutics, Inc.

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1 SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes