XEN1101 is a medication being studied for its safety and tolerability in people with epilepsy. It is designed to help manage seizures in patients who have already participated in previous studies. The trial aims to understand how well patients can tolerate this medication over a long period and to observe any potential side effects.

Focal-onset Seizures – These seizures begin in one specific area of the brain and can affect consciousness or awareness. They may cause unusual sensations, emotions, or movements, depending on the part of the brain involved. As the seizure progresses, it can spread to other areas of the brain, potentially leading to a generalized seizure. Symptoms can vary widely, including muscle twitching, changes in vision, or a sense of déjà vu. The duration of these seizures can range from a few seconds to a couple of minutes. They are often followed by a period of confusion or fatigue.

Primary Generalized Tonic-Clonic Seizures – These seizures involve the entire brain from the onset and are characterized by a combination of muscle stiffness (tonic phase) and rhythmic muscle contractions (clonic phase). They typically begin with a sudden loss of consciousness, followed by a period of muscle rigidity and then convulsions. The person may cry out, fall, and experience muscle jerks, often leading to a brief period of confusion or deep sleep afterward. These seizures usually last a few minutes and can be accompanied by a loss of bladder control or biting of the tongue. They are often followed by a period of drowsiness or confusion known as the postictal state.