Antiviral therapies for cancer

ATC CODE: J05

DEFINITION: Antiviral agents are used to treat infections caused by viruses. In patients with cancer, they are also used in combination with other medications to treat human papillomavirus (HPV)–positive cervical cancer and head and neck squamous cell cancer. Antiviral agents known as protease inhibitors, nucleoside reverse-transcriptase inhibitors, and nonnucleoside reverse-transcriptase inhibitors are employed for human immunodeficiency virus (HIV) infection. Antiviral therapies are also important in the prevention of cancer by curtailing the spread of known cancer-causing viruses such as human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), Epstein-Barr virus (EBV), human T-lymphotropic virus (HTLV), Kaposi sarcoma–associated herpes virus (human herpes virus 8), Merkel cell polyomavirus, and human immunodeficiency virus (HIV).

In the 2020s, antiviral treatments became an area of increased concern even before the advent of the COVID-19 coronavirus, which set off a global pandemic. As of March 2024, the pandemic had claimed an estimated 7 million lives worldwide.

Cancers treated: Cervical cancer, head and neck cancers, HIV infection, and opportunistic viral infections associated with all types of cancer.

Subclasses of this group: Nucleotide analogs, purine nucleoside analogs, acyclic guanine derivatives, pyrophosphate analogs, purine nucleoside guanine derivatives, protease inhibitors, nucleoside reverse transcriptase inhibitors, nonnucleoside reverse transcriptase inhibitors

Delivery routes: Administered orally in the form of capsules, tablets, and solutions at home or in the hospital; some also administered in the hospital by intravenous (IV) infusion or subcutaneous injection

How these drugs work: The first successful antiviral drug, acyclovir, is a nucleoside analogue that was discovered in the 1960s for the treatment of herpesvirus infection. The increased incidence of HIV infection in the 1980s initiated the development of a variety of antiviral agents that are available today, such as azidothymidine (AZT), a nucleoside analogue reverse-transcriptase inhibitor. Antiviral agents work in a variety of ways depending on the drug type. Some competitively inhibit an enzyme located on the viral deoxyribonucleic acid (DNA) chain, halting the growth of the viral DNA. Some work on viral ribonucleic acid (RNA), preventing the virus from penetrating healthy cells. Others inhibit viral nucleic acid synthesis by interacting directly with the DNA enzymes. Protease inhibitors inhibit the enzyme needed for viral replication. Reverse transcriptase inhibitors also inhibit viral replication after incorporating themselves into the viral DNA.

Side effects: The most common side effects associated with antiviral drugs include gastrointestinal symptoms such as reduced appetite (anorexia), abdominal pain, diarrhea, dyspepsia, flatulence, nausea, and vomiting. Other side effects that may occur with antiviral therapy include headache, dizziness, insomnia, depression, peripheral neuropathy, weakness, rash, sweating, back pain, chest pain, fever, muscle ache, pneumonia, weight loss, anxiety, elevated or decreased blood pressure, pancreatitis, tremor, cough, shortness of breath, chills, low white blood cell count, low platelet count, anemia, hypoglycemia, seizures, inflammation of the liver (hepatitis), and liver toxicity.

Prevention: Cancers caused by oncoviruses such as hepatitis B virus, hepatitis C virus, HPV, and Epstein-Barr virus account for about 10 to 15 percent of the global burden of cancer. Following the introduction of the HPV vaccine in 2006, the prevalence of vaccine-type HPV, a leading cause of cervical cancer, dropped by 56 percent among female adolescents aged fourteen to nineteen years old by 2013. A 2021 study in Denmark demonstrated an 86% decrease in cervical cancer among subjects 16 years old and younger who had been vaccinated. In addition, a 68% decrease was reported among older teens. A similar study in Sweden showed a 62% decrease in cervical cancer among women between the ages of 20 and 30 who had been vaccinated.

Chronic infection with hepatitis causes approximately 80 percent of all primary liver cancers worldwide. Hepatitis vaccines can prevent infection with hepatitis B virus, which leads to chronic inflammation of the liver and an increased risk of liver cancer. Vaccination, screenings, and antiviral treatment for these oncoviruses are critical in the prevention of many cancers.

Bibliography

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