Antiviral drugs

Drugs that combat viral infections are called antiviral drugs. Antiviral drugs work by interfering with viral replication. Because viruses are tiny and replicate inside cells using the cells' own metabolic pathways, there are only a limited number of metabolic functions that antiviral drugs can target. In contrast, bacteria are relatively large organisms, commonly reproduce by themselves outside of cells, and have many metabolic functions against which antibiotics can be directed. Therefore, antiviral drugs are much more difficult to develop.
Because interference with the viral functions often also alters normal cellular metabolism, antiviral drugs can show toxic side effects.
Due to their rapid mode of replication in the cells, viruses have also the ability to develop resistance to many drugs, a major concern in the antiviral chemotherapeutic field.

Viroblock's approach

A virus that replicates within the initially infected cell may spread to adjacent cells extracellularly or intracellularly. Extracellular spread occurs by release of virus into the extracellular fluid and subsequent infection of the adjacent cell. Intracellular spread occurs by fusion of infected cells with adjacent, uninfected cells or by way of cytoplasmic bridges between cells. Most viruses spread extracellularly.
During its extracellular phase, and before it initiates a new replication cycle in the next infected cell, a virus is exposed to environmental conditions. This represents a highly vulnerable stage for a virus because it has to face physico-chemical aggressions and host immune response.
Viroblock’s technology targets this phase of the virus life cycle. Specific modifications of the viral envelope by Viroblock’s products induce loss of infectivity. This envelope destabilization can occur on membranes of complete extracellular viruses or on viruses in the process of budding from infected cell.
Viroblock’s approach will be effective only against extra cellular forms of the virus, when these forms are externally accessible, namely in the naso–, oropharynx, respiratory tract (e.g. influenza), the urogenital tract (e.g. HIV), the skin or eye (e.g. herpes simplex) and deposited on surfaces (fomites).

Applications

Viroblock’s topical strategy of inactivating extracellular viruses through modification of viral envelope, thus interrupting viral transmission, is potentially very powerful for respiratory protection.
Although lined by cells that are susceptible to infection by many viruses, the respiratory tract is ordinarily protected by effective cleansing mechanisms. A mucus layer and ciliated cells line the nasal cavity and most of the lower respiratory tract. Inhaled virus particles deposited on this surface are trapped in mucus, carried by ciliary action from the nasal cavity and airways to the pharynx, and then swallowed or coughed out.
Despite these protective mechanisms, the respiratory tract is, overall, the most important entry site of viruses into the body. Following respiratory infection, many viruses remain localized (e.g. respiratory syncytial virus, parainfluenza viruses and influenza viruses) whereas some others become systemic (e.g. measles virus, varicella virus and variola virus).

Viroblock is implementing a global respiratory protection strategy with two lines of development:

• Pharmaceutical: antiviral respiratory spray
Being a major viral entry site in the body, the respiratory tract is an ideal target for prophylaxis and treatment of viral induced diseases. Enveloped viruses infecting the respiratory tract include influenza viruses, respiratory syncytial virus and SARS virus.

• Non-pharmaceutical: antiviral coating agent
Results obtained in Viroblock’s laboratories demonstrate an excellent antiviral efficacy of the products on solid matrix in air phase. This opens promising opportunity to develop antiviral surface products for filtering devices such as medical health masks.
Medical masks are the first-line non-pharmaceutical protection against viruses. Although they represent the most affordable protection for large populations, most medical masks do not even meet minimum expectations for antiviral respiratory protection. As a consequence, there is an urgent unmet need for technologies improving virus filtration/inactivation of such devices.