you will attend an initial visit where a medical professional will record your medical history, perform a physical examination, measure vital signs such as blood pressure and heart rate, and conduct an electrocardiogram (ecg) to check heart activity.

blood and urine samples will be taken for laboratory tests to establish baseline values for blood cells and chemistry.

you will complete several questionnaires that evaluate your behavior and symptoms, including the aberrant behaviour checklist, the repetitive behaviour scale‑revised, and the phelan‑mcdermid syndrome assessment of severity.

all information collected at this visit will be used as a reference point for later comparisons.

you will begin taking vafidemstat in oral capsule form.

the prescribed dose is 1111111 mg per capsule, taken as directed by the study team for the duration of the study.

the medication is taken by mouth; the exact frequency (for example, once daily) will be explained by the study staff.

you will return to the clinic at scheduled intervals (for example, every four weeks) while you are taking the study medication.

during each visit, the staff will ask you about any new or worsening symptoms, known as adverse events, and record their number, frequency, and severity.

vital signs, an ecg, and laboratory tests will be repeated to detect any clinically relevant changes.

if a serious adverse event occurs, additional assessments may be performed, and the study medication may be stopped.

at selected visits, you will again complete the behavioral questionnaires that were administered at baseline.

these include the aberrant behaviour checklist irritability subscale, the clinical global impression of severity for anger and aggression, the repetitive behaviour scale‑revised, and other subscales that measure stereotypic behaviour, hyperactivity, inappropriate speech, and social withdrawal.

the results will be compared with your baseline scores to determine any changes in your condition.

throughout the study, you will be asked to answer questions from the columbia – suicide severity rating scale (c‑ssrs), which evaluates whether you have had thoughts of self‑harm or suicidal behaviour.

any indication of suicidal ideation will be reported immediately and managed according to safety protocols.

at the end of the study period, you will undergo a final visit that repeats the physical examination, vital signs, ecg, laboratory tests, and behavioral questionnaires.

the study medication will be discontinued, and the overall safety and efficacy data will be summarized.

you will be thanked for your participation, and any remaining concerns will be addressed by the study team.