Influenza A virus infection is one of the most common respiratory tract diseases in humans. It is the cause of typical seasonal flu and major human pandemics worldwide. According to the World Health Organization (WHO), in October 2023, approximately 3 to 5 million severe influenza cases were reported, resulting in 290,000 to 650,000 deaths worldwide. The Influenza Medications Market size was valued at USD 942.6 million in 2023 and is anticipated to grow at a 2.9% CAGR from 2024 to 2032, driven by the rising prevalence of influenza.

Currently, the primary drug used clinically for influenza virus infection is Tamiflu (oseltamivir), which targets the viral neuraminidase (NA). Monotherapy against RNA viruses is usually inefficient, and thus, combination therapy against the influenza virus is an urgent, unmet need.

TECHNOLOGY
We discovered several highly potent small-molecule inhibitors of the virus. The best of these inhibitors are new chemical entities that exhibit ED50 values ranging from ~10 nM to ~1 μM across divergent H1N1 subtypes in cell-based assays. Our advancements towards utilization and commercialization of this thechnology is three-pronged:

In vitro: Using cryogenic electron microscopy, we found that our molecules target a novel binding pocket in one of the two major surface proteins of the virus – the hemagglutinin (HA) This pocket is fully conserved among H1 and H6 hemagglutinins and highly conserved (1 semi-conservative substitution) across H2 and H5 hemagglutinins, suggesting the potential for broad-spectrum antivirals and far-reaching antiviral therapeutics. HA facilitates endosome-mediated virus entry into the host cell. Being crucial to viral infections, HA is a well-established drug target; for example, it is the target of the broad-spectrum antiviral drug arbidol (umifenovir), which is used clinically in Russia and China. Our measurements, employing genetic mutation approaches, a limited-proteolysis protection assay, and the biophysical method differential scanning fluorimetry (DSF), provided further evidence for the molecular mechanism underlying HA inhibition by our novel compounds, suggesting that they interfere with the crucial conformational change needed for HA-facilitated membrane fusion, thus preventing the virus from infecting its host (Figure 1).

In cellulo: Using our novel chemiluminescence-based neuraminidase probe (CLNA) that is capable of monitoring viral replication and spreading through the detection of the viral neuraminidase activity, we demonstrated that our inhibitors are ~500-1,000-fold more potent at inhibiting the H1N1 virus (Influenza A Puerto Rico 08/34; PR8) replication than amantadine (a former anti-flu drug) in infected cell In vitro pharmacokinetic studies showed that these leads may permeate intestinal tissue and exhibit liver microsomal stability comparable to that of existing drugs.

In vivo: A preliminary drug efficacy trial using mice was conducted with the best leads and showed significantly attenuated weight loss and clinical symptoms of highly lethal influenza disease compared to untreated mice, and was superior to treatment with the previously used drug amantadine. Administration of the CLNA probe intranasally to PR8-infected mice showed that the probe is sensitive and robust in visualization of the infection, quantification of virus, and monitoring the progression of the disease within the mice’s bodies in the presence or absence of small-molecule inhibitors through a broad dynamic range, potentially adding important yet missing capabilities to the physician’s toolbox. In vivo pharmacokinetic studies demonstrated that the two best lead compounds are orally bioavailable in mice and do not exhibit any observable toxicity at a high dose of 50 mg/kg.

Figure 1. (Left) HA trimer in its fusion-inactive form, showing subunits HA1 in light teal, HA2 in grey, and the fusion peptides in green. We propose that the inhibitor locks the protein in a pre-fusion conformation, preventing the “jack-knife” motion required to expose the fusion peptide and initiate viral fusion with the host cell. (Right) A demonstration of the fusion inhibition effect using a simplified depiction.

POTENTIAL APPLICATION
A new influenza treatment that inhibits viral replication by targeting the viral HA protein. Applicable both as a monotherapy and in a cocktail with inhibitors of other viral targets (combination therapy).

STAGE OF DEVELOPMENT
Using both ligand-based and structure-activity relationship studies, we have identified over 20 potent hits so far, including 18 novel chemical entities. Testing against viruses with diverse HA types, optimizing dosing and formulation for oral administration, and conducting further drug efficacy studies in mice to test potential combination therapies with existing drugs are needed to conclude the first pre-clinical phase.
PATENTS
PCT/IL2025/050558