This clinical trial is focused on studying a type of cancer called recurrent or metastatic head and neck squamous cell carcinoma. This is a condition where cancer cells form in the tissues of the head and neck and have either returned after treatment or spread to other parts of the body. The study is testing a combination of two treatments: Buparlisib (also known by its code name AN2025) and Paclitaxel, compared to using Paclitaxel alone. Buparlisib is taken orally in the form of capsules or tablets, while Paclitaxel is given as an infusion, which means it is administered directly into the bloodstream through a vein.

The purpose of this study is to see if the combination of Buparlisib and Paclitaxel can help patients live longer compared to Paclitaxel alone. Participants in the study will receive either the combination treatment or Paclitaxel by itself. The study will last for a period of up to 60 days, during which the effects of the treatments will be monitored. Patients will be closely observed to understand how the treatments affect their cancer and overall health.

Throughout the study, researchers will collect information on how well the treatments work and any side effects that may occur. This includes looking at how long patients live, how the cancer responds to the treatment, and how long any positive effects last. The study will also explore the safety of the treatments by monitoring any adverse effects and conducting regular laboratory tests. Additionally, researchers will investigate certain biological markers to gain more insights into the disease and treatment responses.