Copanlisib is a PI3K (Phosphoinositide 3-kinase) inhibitor primarily used in the treatment of relapsed or refractory follicular lymphoma (FL), a type of B-cell non-Hodgkin lymphoma. It works by inhibiting PI3K enzymes involved in signaling pathways that promote the growth and survival of cancer cells. This targeted approach helps to slow down or stop the progression of the disease. It is administered intravenously in a clinical setting, allowing for controlled dosing and monitoring. Copanlisib is typically considered for patients who have not responded to other treatments, providing an alternative option. Its use is closely monitored by healthcare professionals to manage potential side effects, such as hyperglycemia, hypertension, and infections, and to ensure the best possible outcomes.