Advances in antiviral therapy in dermatology

Advances in Antiviral Therapy

Infections with five of the herpesviruses (herpes simplex virus 1 [HSV-1], HSV-2, varicella zoster virus, Epstein-Barr virus, and cytomegalovirus) are treated with topical or systemic antiviral therapies. There are more than 100 genotypes of human papillomaviruses (HPVs), which may manifest as warts, skin cancers, cervical cancer, anogenital cancers, and upper digestive tract cancers. Molluscum contagiosum (MC) is a common, benign viral infection of the skin. Immunomodulating agents, such as imiquimod, act on HPV and MC indirectly by inducing host immune responses, such as cytokines and cell-mediated immunity, and thereby reduce recurrences. There are multiple vaccines available for certain viral diseases and others in development for HSV-2 and HPV.

Emerging therapies for herpes viral infections (types 1 – 8)

There are eight members of the herpesviridae family: herpes simplex virus-1 (HSV-1), HSV-2, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, human herpes virus-6, human herpes virus-7 and human herpes virus-8. The diseases caused by viruses of the herpesviridae family are treated with and managed by systemic and topical antiviral therapies and immunomodulating drugs. Because these viruses establish a latent state in hosts, antiherpetic agents, such as nucleoside analogues, only control symptoms of disease or prevent outbreaks, and cannot cure the infections. There is a need for treatments that require less frequent dosing, can be taken even when lesions are more advanced than the first signs or symptoms, and can treat resistant strains of the viruses without the toxicities of existing therapies. Immunomodulating agents, such as resiquimod, can act on the viruses indirectly by inducing host production of cytokines, and can thereby reduce recurrences of herpes. The new helicase primase inhibitors, which are the first non-nucleoside antiviral compounds, are being investigated for treatment of HSV disease, including infections resistant to existing therapy.

Changing paradigms in dermatology: antivirals in dermatology

Almost all of the approved antiviral drugs have become available during the past two decades. Approximately one half of these agents are for the treatment of human immunodeficiency virus (HIV) infections and comprise five classes. The first three classes all act to inhibit reverse transcriptase: nucleoside analogs; nonnucleoside analogs; and nucleotide analogs. The fourth class, protease inhibitors, prevent viral packaging; the fifth class, fusion inhibitors, prevent fusion between HIV and the target cell. Four nucleoside analogs, acyclovir, valacyclovir, famciclovir and penciclovir, are approved for the therapy of herpes simplex and varicella zoster infections. Interferon alpha is approved in the injectable form for condyloma acuminatum and Kaposi's sarcoma, but the more efficient method of delivering this agent is via interferon induction following topical use of imiquimod cream. Antiviral agents are also approved for infections with cytomegalovirus, hepatitis B and C, respiratory syncytial virus, and influenza viruses. Most of these antiviral drugs are virastatic and not viracidal. Vaccines and public health measures are much more effective and cost effective than antiviral drugs and must be promoted accordingly in the defense against viral infections.