Press release Synairgen plc(‘Synairgen’ or the ‘Company’) Synairgen announces inclusion of its inhaled interferon beta treatment in US NIH ACTIV-2 trial in COVID-19 outpatients ACTIV partnership is funded by “Operation Warp Speed”, led by the US Government’s Department of Health and Human Services and designed to speed up the development of the most promising treatments and vaccine candidates for COVID-19 Southampton, UK – 25 January 2021: Synairgen plc (LSE: SNG), the respiratory drug discovery and development company, today announces a clinical trial agreement to include its inhaled interferon beta-1a treatment (SNG001) in the ACTIV-2/A5401 Phase II/III trial in patients with COVID-19 not yet requiring hospitalisation. The trial is sponsored by the US National Institute of Allergy and Infectious Diseases (NIAID), part of the US National Institutes of Health (NIH). NIH’s Accelerating COVID-19 Therapeutic Inventions and Vaccines (ACTIV) (https://www.nih.gov/research-training/medical-research-initiatives/activ) is a public-private partnership to develop a coordinated research strategy to speed up the development of the most promising treatments and vaccine candidates for COVID-19. ACTIV-2 is a master protocol designed for evaluating multiple investigational agents compared to placebo in adults with mild-to-moderate COVID-19, not requiring hospitalisation. The Phase II/III ACTIV-2 study, led by the NIAID-funded AIDS Clinical Trials Group (ACTG), is an adaptive, randomised, blinded, placebo-controlled trial. The Phase II evaluation of SNG001 will see the recruitment of up to a maximum of 220 participants across US sites, in a home-based setting, split between SNG001 and placebo, and a positive result enables progression into the Phase III part of the study. NIAID is the regulatory sponsor and holder of the Investigational New Drug application to conduct the ACTIV-2 study, which is funded by Operation Warp Speed, a partnership led by the US Department of Health and Human Services through NIAID, to investigate and coordinate the development, manufacturing, and distribution of COVID-19 diagnostics, therapeutics and vaccines. Richard Marsden, CEO of Synairgen, said: “The inclusion of our inhaled interferon beta-1a treatment in the US Government-funded ACTIV-2 trial reflects the strong interest that our Phase II data has generated and the Company’s strong belief that this drug could play a vital role in the treatment of COVID-19. As an inhaled treatment, SNG001 offers ease of use that makes it possible for patients to administer it conveniently at home, reducing the risk of virus transmission during hospital visits and relieving the major logistical strain on healthcare systems. At-home treatments also have the potential to be taken much earlier in the course of the illness, preventing the progression of the virus in the lower respiratory tract and, in the scenario where hospitals are at capacity, treating patients in the home setting could be the only option. We hope to gain valuable data from this trial, which will aid us in progressing approval of SNG001 as a treatment for COVID-19.” In addition, Synairgen commenced dosing in an international 610 patient Phase III trial on 12 January 2021, assessing the efficacy of inhaled interferon beta in hospitalised patients with COVID-19. Information within this announcement is deemed by the Company to constitute inside information under the Market Abuse Regulation (EU) No. 596/2014. For further enquiries, please contact: Synairgen plcRichard Marsden, Chief Executive OfficerJohn Ward, Finance DirectorTel: + 44 (0) 23 8051 2800 finnCap (Nominated Advisor & Joint Broker)Geoff Nash, James Thompson, Charlie Beeson (Corporate Finance)Alice Lane, Sunila de Silva (ECM)Tel: + 44 (0) 20 7220 0500 Numis Securities Limited (Joint Broker)James Black, Freddie Barnfield, Duncan MonteithTel: +44 (0) 20 7260 1000 Consilium Strategic Communications (Financial Media and Investor Relations)Mary-Jane Elliott, Sue Stuart, Olivia Mansersynairgen@consilium-comms.comTel: +44 (0) 20 3709 5700 Notes for Editors About Synairgen Synairgen is a clinical-stage respiratory drug discovery and development company founded by University of Southampton Professors Sir Stephen Holgate, Donna Davies and Ratko Djukanovic. Synairgen is currently fully focused on progressing its inhaled interferon beta1a broad spectrum antiviral drug as an effective treatment for people suffering with COVID-19 infection. Synairgen's differentiating human biology BioBank platform and world-renowned international academic KOL network has broader applicability for lung viral defence in other respiratory disorders including asthma and COPD. Synairgen is quoted on AIM (LSE: SNG). For more information about Synairgen, please see www.synairgen.com COVID-19 COVID-19, caused by the SARS-CoV-2 virus, is a global threat and there is an urgent need to assess new treatments to prevent and effectively treat the severe lower respiratory tract illness that can occur with this disease. Older people and those with co-morbidities such as heart and lung complications and diabetes are at greatest risk of developing severe or fatal disease. SNG001 (inhaled Interferon beta) applicability to COVID-19 Interferon beta ('IFN-beta') is a naturally occurring protein, which orchestrates the body's antiviral responses. It is used widely systemically for the treatment of multiple sclerosis and is a safe and well tolerated drug. There is growing evidence that deficiency in IFN-beta production by the lung could explain the enhanced susceptibility in 'at-risk' patient groups to developing severe lower respiratory tract (lung) disease during respiratory viral infections. Furthermore, viruses, including coronaviruses especially SARS-CoV-2, have evolved multiple mechanisms for suppressing endogenous IFN-beta production in the lung thereby helping the virus to evade the innate immune system. The addition of exogenous IFN-beta before or during viral infection of lung cells in vitro either prevents or greatly reduces viral replication to reduce the severity of infection and accelerate recovery. Recognising the importance of achieving high concentrations in the lung where SARS-CoV-2 exerts most of its tissue damaging effects, Synairgen's SNG001 is a formulation of IFN-beta-1a for direct delivery to the lungs via nebulisation. It is pH neutral, and is free of mannitol, arginine and human serum albumin, making it suitable for inhaled delivery direct to the site of action. Phase I and II trial data have shown that SNG001 activates lung antiviral defences as measured in sputum cells, and that SNG001 has been well tolerated in approximately 280 asthma/COPD/COVID-19 patients to-date. In July 2020, Synairgen announced the results of its Phase II double-blind, placebo-controlled study of 101 randomised COVID-19 hospitalised patients, which showed that SNG001 given for 14 days, was associated with greater odds of improvement versus placebo on the WHO Ordinal Scale for Clinical Improvement and more rapid recovery to the point where patients were no longer limited in their activity, with a greater proportion of patients recovering during the 28-day study period. The results were published in The Lancet Respiratory Medicine: "Safety and efficacy of inhaled nebulised interferon beta-1a (SNG001) for treatment of SARS-CoV-2 infection: a randomised, double-blind, placebo-controlled, phase 2 trial". Monk, P D et al., 12 November 2020, accessible here: https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30511-7/fulltext. On 20 January 2021, Synairgen announced that it had completed recruitment of 120 COVID-19 patients (over the age of 65, or those over 50 with a comorbidity) in the home setting for its SG016 trial. Results from this study are expected in Q2 2021.