A drug currently prescribed to treat a rare enzyme deficiency can help cells clear the herpes simplex 1 and herpes simplex 2 viruses, according to a new study published in the journal Science Advances. The new data shows that the antiviral activity of the drug called phenylbutyrate, or PBA -- was even better when used along with acyclovir, a common HSV-1 treatment. When used in combination, less acyclovir is needed to effectively suppress the virus compared to acyclovir alone -- this is important because acyclovir is also known to have toxic side effects in the kidneys. There are two types of herpes simplex virus: herpes simplex 1, which infects the eyes and mouth and is a leading cause of blindness, and herpes simplex 2, a genital infection that may cause painful sores and can seriously impair quality of life. Treatment for both infections often includes acyclovir a systemic medication is taken orally. However, long-term use often results in resistance to the drug as well as kidney damage. Shukla and colleagues investigated the antiviral effects of PBA and found that in cells the drug disrupts the ability of the virus to hijack the cellular machinery used to produce proteins. Normally, viruses infect cells and force them to produce viral proteins so the virus can replicate itself.