Current Therapies Present Limited Options against Emerging Viruses

There are three types of conventional antiviral drugs that prevent or treat viral infections:
  • Vaccines mimic viral infections, helping the body to produce antibodies that prevent viruses from attaching to host human cells, therefore warding off future infections;
  • Therapeutic antibodies are directly administered proteins that bind to viruses and prevent them from entering cells;
  • Replication inhibitors are small molecules that stop the replication of viruses already inside infected cells.

These drugs work by interrupting steps in the virus life cycle (viral genome replication) once a virus has infected a host. Although they have greatly helped people protect their health against viruses, each of these drugs also suffers unique challenges:
  • Vaccines are only preventative and cannot treat acute virus infections. Broad vaccination of populations is practically difficult, and concerns exist that vaccination may worsen disease symptoms in persons who have been infected by other viruses.
  • Therapeutic antibodies have potential to treat infections with greater success than replication inhibitors, but have trouble reaching important parts of the body, such as the brain. The development of therapeutic antibodies is also very expensive and has significant logistical and regulatory hurdles that pose barriers to mass production.
  • Replication inhibitors, the most common class of antiviral drug on the market, often have poor efficacy against mosquito-borne viral infections because diagnosis often comes too late for inhibiting replication to be meaningful—there are already too many virus particles in the infected host, so stopping new ones is less useful.
In addition, all of these antiviral products suffer from two crucial problems: they do not work against multiple viruses and/or they lose efficacy against emerging drug-resistant virus strains.

Viruses replicate quickly, and natural mutations mean that the viral genome targeted by conventional antiviral drugs can change. As these mutations accumulate, drug-resistant virus strains emerge, and existing vaccines, replication inhibitors, and antibodies become of little use.

The consequences of the “one bug, one drug” approach are dire: Every time a new virus problem emerges, years of additional research & development are needed to craft a new drug from scratch.

HIV, Hepatitis C and other viruses common in wealthy countries benefit from investment, while viruses elsewhere are neglected until they emerge as a global threat. By that time, it is often too late.