STOP-COVID19: Superiority Trial Of Protease Inhibition in COVID-19

BACKGROUND COVID-19 is a respiratory disease caused by a novel coronavirus severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and causes substantial morbidity and mortality.This clinical trial is designed to evaluate the potential of Brensocatib as a novel host directed therapy for the treatment of adult patients hospitalised with COVID-19. The investigators hypothesise that Brensocatib, by blocking damaging neutrophil proteases, will reduce the incidence of acute lung injury and acute respiratory distress syndrome (ARDS) in patients with COVID-19, thereby resulting in improved clinical outcomes at day 15 and day 29, fewer days dependent on oxygen or mechanical ventilation, and shorter length of hospital stay.

Coronavirus (CoVs) are positive-sense single stranded enveloped Ribonucleic acid (RNA) viruses, many of which are commonly found in humans and cause mild symptoms. Over the past two decades, emerging pathogenic CoVs capable of causing life-threatening disease in humans and animals have been identified, namely severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) and Middle Eastern respiratory syndrome coronavirus (MERS- CoV).

In December 2019, the Wuhan Municipal Health Committee (Wuhan, China) identified an outbreak of viral pneumonia cases of unknown cause.5 Coronavirus RNA was quickly identified in some of these patients. This novel coronavirus has been abbreviated as SARS-COV-2 and has 89% nucleotide identity with bat SARS-like-CoVZXC21 and 82% with that of human SARS-CoV. This novel coronavirus has been designated SARS-CoV-2, and the disease caused by this virus has been designated COVID-19. Initial infections were travel associated with individuals having contact with Wuhan or other affected areas but the disease has now spread to affect hundreds of thousands of patients worldwide with widespread community transmission across the globe.

Outbreak forecasting and mathematical modelling suggest that these numbers will continue to rise.

Global efforts to evaluate novel antivirals and therapeutic strategies to treat COVID-19 have intensified but to date dexamethasone is the only therapy shown to reduce mortality in COVID-19 while repurposed antiviral drugs did not show clinical benefits in the World Health Organisation SOLIDARITY trial.

Mortality from COVID-19 has been estimated at between 0.5% and 3.4% of infected patients and occurs most frequently because of the development of ARDS. In contrast to some, particularly bacterial pneumonias, where patients present with acute respiratory failure and sepsis, the dynamics of COVID-19 infection demonstrate a slow deterioration in oxygenation with the development of bilateral infiltrates in a high proportion of patients, consistent with the development of ARDS. Patients subsequently require mechanical ventilation.

Treatments that could prevent the requirement for mechanical ventilation or shorten the duration of intensive care unit stay by reducing the severity of ARDS are therefore the number 1 target for COVID-19 therapy.

Neutrophils in ARDS Neutrophil influx into the extravascular compartments of the lungs is a defining characteristic of ARDS. During ARDS, circulating neutrophils become primed, resulting in reduce deformability and retention within the pulmonary capillary bed. They then migrate across the endothelium through the interstitium and epithelium into the airways themselves. As neutrophils migrate they are activated and release oxidants, proteases and neutrophil extracellular traps. All of these processes are important in killing bacterial pathogens but in ARDS these processes become prolonged and excessive leading to progressive lung damage. Neutrophil elastase and other neutrophil proteases such as proteinase-3 and cathepsin-G cause tissue injury resulting in increased epithelial and endothelial permeability which leads to the influx of protein-rich alveolar oedema.

Mortality in ARDS correlates directly with the extent of neutrophilia in the lung. Both human clinical data and murine studies demonstrate a key role for neutrophils in ARDS. Neutrophil depletion in multiple models of ARDS including those induced by lipopolysaccharide, acid, ventilator lung injury, transfusion and other stimuli, reduces the severity of acute lung injury including endothelial-epithelial cell damage and capillary-alveolar permeability.

Neutrophil proteases and particularly neutrophil elastase are believed to be central to the neutrophil induced lung damage. Neutrophil elastase is a serine protease contained within primary neutrophil granules which is released in response to neutrophil activation or neutrophil extracellular trap formation. It is involved in the pathogenesis of multiple inflammatory diseases and therapeutic development of neutrophil elastase inhibitors for use in ARDS has been ongoing for many years. Neutrophil elastase is markedly elevated in human ARDS samples and the inhibition of neutrophil elastase has been demonstrated to reduce epithelial injury in multiple animal models of lung injury across multiple stimuli including lipopolysaccharide (LPS), bleomycin, ventilation, sepsis and many others. Neutrophil elastase is critical to the development of neutrophil extracellular traps, which are highly damaging webs of DNA studded with proteases and other neutrophil derived toxins. Neutrophil extracellular traps (NET) formation and the failure to clear NETs have been strongly implicated in the development and poor outcomes from ARDS. Inhibition of neutrophil elastase reduces the formation of NETs.

A challenge therapeutically has been how to inhibit neutrophil elastase since administration of competitive inhibitors either orally or through the inhaled route may not be sufficient to block elastase activity in the lung.

RATIONALE Neutrophil elastase, proteinase-3 and cathepsin-G are activated during neutrophil maturation in the bone marrow through dipeptidyl peptidase 1 (DPP1; also known as cathepsin C), which removes the N-terminal dipeptide sequence of neutrophil serine proteases allowing active enzymes to be packaged into granules prior to release of neutrophils into the circulation. Brensocatib (INS1007, formerly AZD7986) is an orally delivered selective, competitive, and reversible inhibitor of DPP1. Brensocatib has been shown to inhibit neutrophil serine protease activity in blood in both animal models and healthy volunteers.

The investigators recently conducted a large phase 2 study of Brensocatib in patients with bronchiectasis designed to test if treatment with Brensocatib could reduce infective exacerbations and reduce neutrophil elastase activity in the lung in bronchiectasis patients. The study met its primary endpoint of time to first exacerbation and key secondary endpoint of the frequency of exacerbations as well as showing marked reductions in neutrophil elastase concentrations in sputum. Due to the need to replace the circulating pool of neutrophils with new neutrophils which are deficient in elastase, Brensocatib does not have its effect immediately, but rather over several days. Elastase concentrations were reduced at the first time point at day 14 in the phase 2 study, with very large reductions observed at the second time point at day 28.

In a cohort of 191 hospitalised COVID-19 patients with a completed outcome, the median time from illness onset to discharge was 22·0 days (IQR 18·0-25·0) and the median time to death was 18·5 days (15·0-22·0). Thirty-two patients (17%) required invasive mechanical ventilation and the median time from onset to mechanical ventilation was 14.5 days. The investigators hypothesise that the mechanism of action of Brensocatib to reduce protease activity will be more rapid in COVID-19 patients compared to bronchiectasis due to a more rapid turnover of neutrophils in acute illness. The objective is to test whether by reducing neutrophil protease activity in neutrophils the investigatorscan prevent or reverse the development of ARDS and thereby improve outcomes in individuals with COVID-19 infection.