Five different nonreceptor tyrosine kinase inhibitors were effective against viral replication of pandemic viruses and seasonal influenza viruses in an ex vivo lung model.
Influenza viruses remain a high cause of morbidity and mortality worldwide as viral mutations outwit vaccine efficacy, Robert Meineke, PhD, of the University of Veterinary Medicine in Hannover, Germany, and colleagues wrote.
“As with previous influenza pandemics and the current SARS-CoV-2 pandemic, effective vaccines are not readily available at early stages of a pandemic,” they noted. To help manage the limitations of timing and effectiveness of current vaccines, the researchers proposed repurposing nonreceptor tyrosine kinase inhibitors (NRTKIs) to block seasonal flu and COVID-19 viral replication.
In a study published in iScience, the researchers identified six NRTKIs currently approved by the U.S. Food and Drug Administration that showed in vitro inhibition of both pandemic viruses (H1N1) and seasonal influenza viruses (H3N2). These included defactinib, acalabrutinib, saracatinib, and bosutinib, all of which reduced hPCLS infectivity by approximately 50%. In addition, ibrutinib and bosutinib had the largest impact on viral titers. The antiviral effects of NRTKIs appeared to be independent of multiplicity of infection.
The researchers then tested the NRIKIs on an ex vivo model of human precision-cut lung slices to validate the effects of NRTKIs as antivirals against influenza A viruses (IAVs).
In this model, the highest peak titers were achieved at 48 hpi following infection with virus strains NL09 and NL11. The hPCLS models also showed consistent tolerability to 1x concentrations. “Our cytotoxicity cut-off was 20% of the positive control treatment; none of the NRTKIs surpassed this cutoff at [1x] max,” the researchers wrote.
Five of the six identified NRTKIs were validated in the ex vivo setting. All five reduced viral titers by at least 10-fold to more than 1,000-fold. Of these, ibrutinib, bosutinib, and bosutinib showed a significant effect at all concentrations, while treatments with acalabrutinib and defactinib were significant at 24 hpi and 48 hpi. The NRTKs also showed a high genetic barrier against emerging resistant virus mutations.
The study demonstrates the ability of NRTKIs to target kinases required for replication of IAV, the researchers wrote, and that NRTKIs “represent promising drugs for the development of the next generation of antivirals.”
More research is needed to determine the therapeutic window given that NRTKIs are targeting host factors versus virus-targeted antivirals, but the advantages of NRTKIs include localized delivery that can limit possible cytotoxic effects, and their safety and bioavailability are well established, they said.
The findings were limited by several factors including the use of lung tissue mainly from older donors with lung cancer, the researchers noted. However, this population could be considered at increased risk for IAVs and therefore the data are more clinically applicable.
In addition, “because many viruses utilize the same (or related) host kinases to facilitate replication and transmission, our studies have broader implications for the potential use of these SMKIs to treat infections by other viruses,” they concluded.
The study received no outside funding. The researchers had no financial conflicts to disclose.