This study is testing a new medicine called Pritelivir for people who are immunocompromised, meaning their immune system is weaker. They have infections from the Herpes Simplex Virus (HSV) that don't get better with a common medicine called Acyclovir. The study compares Pritelivir with other treatments like Foscarnet or Cidofovir. Participants take Pritelivir once a day after a starting dose. The study aims to see if Pritelivir works better and is safe for patients.

Key Points:

• The study could last up to 28 days, with a possible extension to 42 days.
• Participants must be immunocompromised and have HSV resistant to Acyclovir.
• Participants need to agree to use birth control and have regular checkups.

The study is divided into different parts, each with specific requirements. Participants must be at least 16 years old (18 in some countries) and cannot have certain other health problems. Pregnant or breastfeeding women cannot join. The goal is to see if all herpes sores heal in the study period.