A Study to Compare Sitavig (Acyclovir) Buccal Tablet With a Placebo in the Treatment of Herpes Labialis in Participants Whose Immune System Works Normally

Researchers are looking for a better way to treat people who have recurrent herpes labialis, also known as cold sores. This is a type of viral infection that causes redness and blisters on the mouth and lip and that recurs.

Herpes labialis is caused by a virus called the herpes simplex virus (HSV). The infection is spread when a person comes into direct contact with someone else who has the infection. Once a person becomes infected with HSV, the virus multiplies and spreads, which can cause redness and blistering on the mouth and lip. The blisters crust over and heal. Once healed, the virus is said to go into an "inactive" phase. This means the virus does not cause any symptoms, but still remains in the body. HSV can then become "active" again. This means causing cold sore lesions to reappear. HSV can become active in different ways. Some of these include when a person has a fever, comes into contact with strong sunlight or has a condition that lowers one's immune system It can also happen during a woman's menstrual cycle, also called a period.

In this study, the researchers want to learn more about the available treatment called acyclovir 50mg buccal tablet. acyclovir 50mg buccal tablet is used for treating viral infections. It sticks to the inside of the mouth and directly treats the infected area. This helps stop the HSV from multiplying and spreading.

In this study, the researchers want to gather additional data on acyclovir 50 mg tablet, an available treatment for herpes labialis. It is a buccal tablet that sticks to the gum inside the mouth and directly treats the infected area to help stop the HSV from multiplying and spreading.

In this study, the researchers want to compare the efficacy of acyclovir 50 mg buccal tablets versus placebo in the treatment of herpes labialis. A placebo is a treatment that looks like the study medicine but does not have any medicine in it. Study participants will include those who have had at least 4 episodes of herpes labialis within the past 12 months prior to joining the study. To compare the study treatments, the researchers will measure the "duration of episode" (DOE) for each participant. DOE is amount of time it takes for symptoms to disappear and for herpes labialis lesions to heal after taking the study treatment. A doctor will look at the participants' symptom scores and facial images to determine the DOE. Assessments will be done over a period of 14 days.

The participants in this study will take either acyclovir 50mg buccal tablet or the placebo as a tablet by mouth 1 time.

There will be a 2 week treatment phase and a 12 month follow up phase. The participants in this study will not be required to visit the study site. Instead, the participants will have virtual meetings with the study doctors from their homes using the internet. During the treatment phase, there will be 2 meetings. Throughout the follow up phase, the doctors will call the participants 4 times. Each participant will be in the study for about 20 months.

During the treatment phase of the study, the participants will:

• take their blood pressure and pulse
• check their mouth health through a questionnaire
• take pictures of their face and herpes labialis symptoms During the whole study the participants will answer questions about how they are feeling, what medications they are taking, and what adverse events they are having.

The doctors will keep track of any adverse events. An adverse event is any medical problem that a participant has during a study. Doctors keep track of all adverse events that happen in studies, even if they do not think the adverse events might be related to the study treatments.