Drug Repurposing Approaches for the Treatment of Influenza Viral Infection: Reviving Old Drugs to Fight Against a Long-Lived Enemy

“Drug repurposing, also termed drug repositioning, defines the process of identifying and validating a new therapeutic indication for an existing or developmental drug (38, 42, 43).”

“The molecule is therefore said to present polypharmacologyrelated features, meaning the capacity to act on multiple targets (48, 49).”

“Finding new indications for already-existing drugs has many benefits, mainly by improving cost-effectiveness, reducing risks, and shortening time to market (37, 41).”

“Indeed, human influenza type A and B viruses are responsible for annual flu epidemics marked by up to 1 billion infections, 3-5 million severe cases and 300,000-650,000 deaths worldwide, with an huge economic burden in terms of medical visits, hospitalizations, work/school absenteeism. and productivity loss (1) (2) (3…”

“Besides the inclusion of constantly emerging "omics" (e.g., transcriptomic, proteomic, metabolomic) data to expand our current knowledge of drug/disease-associated mechanisms, in silico data mining and modeling tools have pushed our capacity to analyze data to the next level (58) (59) (60) .”

“In that regard, many well-annotated collections of smallmolecule libraries could be readily made available through different collaborative and/or commercial partnerships in order to accelerate drug repurposing through hypothesis biased or unbiased phenotypic screening [reviewed in (54) (55) (56) (57) ].”

“By binding to the broadly conserved active site of the NA, NA inhibitors interfere with the sialidase enzymatic activity of the viral protein, which is essential for the release of newly formed progeny viruses from the infected cell, hence preventing the spread of infection to the rest of the respiratory tissue (14).”

“Phenotypic screening of bioactive molecule libraries in different experimental cellbased or in vivo disease models without the need of a priori knowledge or consideration of the target and/or mechanism of action the candidate was designed to modulate can provide valuable contribution to overcome this constraint (53).”

“7% of the patients receiving the drug (28, 30).”

“These in silico methods include the screening of chemical, biological, and text databases, analysis of quantitative structure-activity relationships, pharmacophores, homology models, and other molecular modeling approaches as well as network analysis of biological functions, machine learning and almost any other analy…”

“In such segmented nature of the viral genome resides the capacity of influenza viruses to form new reassortant strains following the concomitant infection of a host with more than one strain of human, and/or animal origin, a phenomenon so far observed only among type A influenza viruses [reviewed in (4)].”

“More recently, sildenafil found a third life under the commercial brand of Revatio R © for the treatment of pulmonary hypertension (46).”

“a moderate efficacy of NA inhibitor treatment in reducing symptom duration, pneumonia, hospitalization and mortality, especially when administered within 48 h from symptom onset (18, 19).”

“Interestingly, the proposed mode of action of nitazoxanide toward influenza is clearly distinct to that for which it was designed in its initial indication, acting at the post-translational level by selectively blocking the maturation of the viral glycoprotein HA, with a consecutive impact on its intracellular traffic…”

“During the last decade, an increasing number of studies converged on proposing that many drugs, initially designed for a unique therapeutics target, are in fact expected to hit on average between 6 and 13 different targets (51, 52).”

“Polypharmacological phenomena includes both a single drug acting on multiple targets of a unique disease pathway, or a single drug acting on multiple targets pertaining to multiple disease pathways (50).”

“Another interesting illustration is the previously cited example of favipiravir, which proved its repurposing potential for the treatment of Zika or Ebola viral infections (25, 43, 75).”

“7% of the patients receiving the drug (28, 30).”

“For example, chloroquine, a major antimalarial drug, has been proposed for the treatment of filoviral infections, and more largely for the treatment of other emerging pathogens, as it targets endosomal acidification, a pivotal step in the replication cycle of a large number of viruses (73, 74).”

“Oral oseltamivir (administered as its prodrug oseltamivir phosphate) is the most largely used of the three, whereas inhaled zanamivir is not recommended for very young children nor for individuals with underlying respiratory conditions, and intravenous peramivir is prioritized in hospitalized patients that cannot rece…”

“Baloxavir marboxil is a selective inhibitor of the cap-dependent endonuclease activity of the influenza viral PA polymerase subunit (27), therefore interfering with the cap-snatching activity of the viral polymerase complex.”

“Besides the inclusion of constantly emerging "omics" (e.g., transcriptomic, proteomic, metabolomic) data to expand our current knowledge of drug/disease-associated mechanisms, in silico data mining and modeling tools have pushed our capacity to analyze data to the next level (58) (59) (60) .”

“These results prompted the US Food and Drug Administration (FDA) to approve Xofluza R© (baloxavir marboxil) for the treatment of acute uncomplicated influenza in patients 12 years of age and older who have been symptomatic for no more than 48 h (29).”

“Indeed, human influenza type A and B viruses are responsible for annual flu epidemics marked by up to 1 billion infections, 3-5 million severe cases and 300,000-650,000 deaths worldwide, with an huge economic burden in terms of medical visits, hospitalizations, work/school absenteeism. and productivity loss (1) (2) (3…”

“Moreover, another level of complexity can be added by combining, for example, epidemiologic information obtained in-house and/or from publicly available literature databases with in vitro experimental molecule screenings with the aim to identify novel indications, as in the case of digoxin and prostate cancer (67, 68).”

“Although many mouse and observational studies account for the protective role of statins in pneumonia, most in vivo studies reported so far failed to clearly demonstrate such a beneficial effect in the specific context of influenza infection (99) (100) (101) (102) .”

“This interest is inversely correlated with the very low number of classic antiviral molecules that have been market-approved these last 5 years, mostly for the treatment of hepatitis C virus or HIV-related pathologies (72).”

“On the other hand, the Abelson tyrosine-protein kinase 2 (Abl2), target of the anticancer drug imatinib, has been found to be required for efficient fusion and release of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) pseudovirions into the cytoplas…”

“The effectiveness of nitazoxanide in treating patients with non-complicated influenza was successful in a Phase IIb/III trial (107) and is currently being assessed in a Phase III clinical trial (NCT01610245).”

“Interestingly, the proposed mode of action of nitazoxanide toward influenza is clearly distinct to that for which it was designed in its initial indication, acting at the post-translational level by selectively blocking the maturation of the viral glycoprotein HA, with a consecutive impact on its intracellular traffic…”

“Despite the enormous scientific and technological advances that the field of biomedical research has witnessed in the last 20–30 years, this scenario failed to efficiently translate into significant improvement on the success rate of the classic “from the bench to the bedside” target-centered, mechanistically biased d…”

“On the other hand, a few but not all observational studies highlighted an association between statin treatment with up to 41% reduction of 30-day all-cause mortality in patients hospitalized with laboratory-confirmed seasonal influenza (103) (104) (105) .”

“Further research enabled this molecule as well as some derivatives to be repurposed for the treatment of leprosy and multiple myeloma (45).”

“It was initially shown that ASA had interesting antiviral effects against influenza viruses in vitro and in vivo via the inhibition of the NF-kB activating kinase IkkB, which negatively impacts influenza vRNP transport and release of infectious viral particles (108) (109) (110) .”

“The concept of antiviral combination therapy was originally pioneered for antiretroviral treatments, with the primary goal of preventing or at least delaying the emergence of drug resistance via the targeting of multiple steps of the viral cycle (113).”

“In that regard, many well-annotated collections of smallmolecule libraries could be readily made available through different collaborative and/or commercial partnerships in order to accelerate drug repurposing through hypothesis biased or unbiased phenotypic screening [reviewed in (54) (55) (56) (57) ].”

“Moreover, another level of complexity can be added by combining, for example, epidemiologic information obtained in-house and/or from publicly available literature databases with in vitro experimental molecule screenings with the aim to identify novel indications, as in the case of digoxin and prostate cancer (67, 68).”

“The molecule is therefore said to present polypharmacologyrelated features, meaning the capacity to act on multiple targets (48, 49).”

“Moreover, the emergence of NA inhibitor-resistant virus variants is a matter of concern, with particularly higher frequencies among children and the immunocompromised (20).”

“Furthermore, despite the recent progress made in the pursue of the “Holy Grail” of a universal influenza vaccine that can provide broader, long-lasting protection against both matching, and antigenically diverse influenza strains (9, 10), their clinical effectiveness remains to be evaluated, hence highlighting the nee…”

“In that regard, the relatively recent detection of localized clusters of NA inhibitor-resistant H1N1pdm09 viruses harboring the H274Y mutation combined or not with I222R/V NA substitutions (22, 23) strengthens the importance of continuous surveillance.”

“This identified molecule has shown antiviral properties against influenza A virus in vitro and in vivo (94) .”

“Besides the inclusion of constantly emerging "omics" (e.g., transcriptomic, proteomic, metabolomic) data to expand our current knowledge of drug/disease-associated mechanisms, in silico data mining and modeling tools have pushed our capacity to analyze data to the next level (58) (59) (60) .”

“In that regard, the relatively recent detection of localized clusters of NA inhibitor-resistant H1N1pdm09 viruses harboring the H274Y mutation combined or not with I222R/V NA substitutions (22, 23) strengthens the importance of continuous surveillance.”

“In a clinical trial enrolling hospitalized patients infected by influenza A(H3N2), combination therapy with naproxen, oseltamivir, and clarithromycin showed improved efficacy in terms of hospital stay duration and patient mortality, when compared to oseltamivir treatment alone (118).”

“In that regard, proper mining of biological, chemical and clinical datasets, has proved effective in unveiling novel relationships (65, 66).”

“However, despite the apparent high threshold for drug resistance (24) and broad-spectrum antiviral potential notably validated in the context of recent Ebola virus outbreaks (25), recent results of Phase II/III randomized trials on its therapeutic efficacy against uncomplicated influenza were not completely conclusive…”

“As most alternative antiviral strategies for the treatment of influenza infections, including those related to drug repurposing and targeting the host instead of viral determinants, an emerging trend consists to propose innovative therapies that combine classic antivirals with host-targeting drugs, which starts to sho…”

“Influenza vaccination constitutes the most effective strategy to prevent seasonal flu and its clinical complications, mainly among high-risk populations such as very young children, the elderly, pregnant women, immunocompromised patients as well as people with obesity, diabetes, or cardiorespiratory comorbidities (6,…”

“have demonstrated, in cell culture-based assays using different human and avian models, that the combination of NA inhibitors and nitazoxanide presents synergistic anti-influenza effects (117).”

“a moderate efficacy of NA inhibitor treatment in reducing symptom duration, pneumonia, hospitalization and mortality, especially when administered within 48 h from symptom onset (18, 19).”

“For example, chloroquine, a major antimalarial drug, has been proposed for the treatment of filoviral infections, and more largely for the treatment of other emerging pathogens, as it targets endosomal acidification, a pivotal step in the replication cycle of a large number of viruses (73, 74).”

“Even if nowadays the prevalence of drug-resistance in circulating strains is quite low (≤1%), evidence form pre-2009 seasonal strains has proved that, given the appropriate conditions, resistance could rapidly disseminate to attain a prevalence of 90–100% (17, 21).”

“However, despite the apparent high threshold for drug resistance (24) and broad-spectrum antiviral potential notably validated in the context of recent Ebola virus outbreaks (25), recent results of Phase II/III randomized trials on its therapeutic efficacy against uncomplicated influenza were not completely conclusive…”

“Although their use is mostly focused on the treatment of severely ill patients and the immunocompromised, some countries, including the USA and Japan, regularly resort to antivirals for the management of uncomplicated influenza in otherwise healthy patients (11, 12).”

“In a proof-of-concept study using an in vitro model of infection, we postulated that host global gene expression profiling can be considered as a “fingerprint” or signature of any specific cell state, including during infection or drug treatment, and hypothesized that the screening of databases for compounds that coun…”

“In the context of the evaluation of the antiviral activity of diltiazem in the reconstituted human airway epithelium model MucilAir, our group demonstrated that the diltiazem-oseltamivir combination treatment conferred a greater reduction of apical viral titers than that was measured with the same-dose monotherapy, wi…”

“These in silico methods include the screening of chemical, biological, and text databases, analysis of quantitative structure-activity relationships, pharmacophores, homology models, and other molecular modeling approaches as well as network analysis of biological functions, machine learning and almost any other analy…”

“This drug presents potent antiviral activity against a large panel of circulating strains (82).”

“On the other hand, a few but not all observational studies highlighted an association between statin treatment with up to 41% reduction of 30-day all-cause mortality in patients hospitalized with laboratory-confirmed seasonal influenza (103) (104) (105) .”

“Although many mouse and observational studies account for the protective role of statins in pneumonia, most in vivo studies reported so far failed to clearly demonstrate such a beneficial effect in the specific context of influenza infection (99) (100) (101) (102) .”

“P h a se II (N C T 0 3 2 1 2 7 1 6 ) ( 9 8 ) Frontiers in Immunology | www.frontiersin.org 7 March 2019 | Volume 10 | Article 531 site of NP structure, has identified naproxen, a known inhibitor of inducible cyclooxygenase type 2 (COX-2) commonly used as non-steroidal anti-inflammatory drug.”

“Although their use is mostly focused on the treatment of severely ill patients and the immunocompromised, some countries, including the USA and Japan, regularly resort to antivirals for the management of uncomplicated influenza in otherwise healthy patients (11, 12).”

“P h a se II (N C T 0 3 2 1 2 7 1 6 ) ( 9 8 ) Frontiers in Immunology | www.frontiersin.org 7 March 2019 | Volume 10 | Article 531 site of NP structure, has identified naproxen, a known inhibitor of inducible cyclooxygenase type 2 (COX-2) commonly used as non-steroidal anti-inflammatory drug.”

“Indeed, despite this approach has been questioned due to the fact that the expected altered phenotype readout as a surrogate of an exploitable biological effect induced by the drug candidate might account for an important number of false positive “hits,” it is nonetheless true that the contribution of highthroughput p…”

“Moreover, the length of the current vaccine manufacturing process (at least 6 months to produce sufficiently large vaccine quantities) demands continual strain selection to be done approximately 8 months before the next flu season (6, 8).”

“A clinical trial was conducted during the A(H1N1)pdm09 pandemic in 2009-2010 (COMBINA trial NCT00830323) and failed to demonstrate whether oseltamivir/zanamivir combination therapy improved or reduced the effectiveness of oseltamivir alone in the treatment of influenza infections in community patients (115).”

“In that regard, proper mining of biological, chemical and clinical datasets, has proved effective in unveiling novel relationships (65, 66).”

“Other clinical investigations have shown a greater effectiveness of such combination therapy to reduce influenza transmissibility (116).”

“Although many mouse and observational studies account for the protective role of statins in pneumonia, most in vivo studies reported so far failed to clearly demonstrate such a beneficial effect in the specific context of influenza infection (99) (100) (101) (102) .”

“Another interesting illustration is the previously cited example of favipiravir, which proved its repurposing potential for the treatment of Zika or Ebola viral infections (25, 43, 75).”

“Although many mouse and observational studies account for the protective role of statins in pneumonia, most in vivo studies reported so far failed to clearly demonstrate such a beneficial effect in the specific context of influenza infection (99) (100) (101) (102) .”

“In that regard, many well-annotated collections of smallmolecule libraries could be readily made available through different collaborative and/or commercial partnerships in order to accelerate drug repurposing through hypothesis biased or unbiased phenotypic screening [reviewed in (54) (55) (56) (57) ].”

“On the other hand, a few but not all observational studies highlighted an association between statin treatment with up to 41% reduction of 30-day all-cause mortality in patients hospitalized with laboratory-confirmed seasonal influenza (103) (104) (105) .”

“More recently, a Phase II proof-of-concept study comparing LASAG versus placebo in patients with severe influenza (all patients receiving Tamiflu as standard of care treatment) demonstrated that aerosolized LASAG improved the time to symptom alleviation compared to placebo, despite the absence of a statistically signi…”

“In a mouse infection model, inhalation of LASAG resulted in reduced lung viral titers and protection of mice from lethal infection (85).”

“For example, in a mouse model, the combination of oseltamivir with zanamivir was shown to be not superior to zanamivir monotherapy in the context of influenza A(H3N2) or A(H1N1)pdm09 infection (114).”

“Additionally, inhaled laninamivir, a single-dose long lasting NA inhibitor, is approved in Japan for the prevention and treatment of influenza A and B in both adult and pediatric patients (16).”

“Despite many interesting omics-based approaches (76) or high-throughput screening of specific drug libraries, such as kinase inhibitors (77), no anti-influenza agent issued from drug repurposing has yet reached regulatory market approval.”

“…opportunities, including a substantially higher probability of success to market as compared with developing new virus-specific drugs and vaccines, and a significantly reduced cost and timeline to clinical availability (Ianevski et al., 2019; Pizzorno et al., 2019; Zheng et al., 2018).”

“multiple host factors and pathways that are supportive of virus replication (299, 300).”

“It was demonstrated in vitro and in vivo in a mouse model that Diltiazem modulates host antiviral genes in vitro and in vivo in a mouse model, and cotreatment with Oseltamivir enhanced the antiviral efficacy (362).”

“Repurposing drugs developed for other diseases and conditions may provide a shortcut to antiviral development (Garcı́a-Serradilla et al., 2019; Li and De Clercq, 2020; Pizzorno et al., 2019; Saini et al., 2020).”