after joining the study, you will sign an informed consent form that explains the purpose of the trial and the procedures you will undergo.

your eligibility for the trial will be confirmed by the study team.

a series of evaluations will be performed before any medication is given, including a physical and neurological examination, vital‑sign measurements, electrocardiogram (ecg), laboratory blood tests, and collection of cerebrospinal fluid (csf) for safety baseline values.

you will be asked to keep a diary of seizure events to establish the frequency of dravet syndrome seizures before treatment.

you will receive an intrathecal injection of ion337 (the study medication) into the spinal fluid.

the exact amount of the dose will be determined by the study protocol and will increase in a stepwise manner for different participants.

after the injection, you will remain under observation for a predefined period while the study staff monitor for any immediate adverse reactions.

you will attend scheduled follow‑up visits during which safety laboratory values, vital signs, ecg, and neurological status will be re‑evaluated.

blood and csf samples will be collected to measure ion337 levels (pharmacokinetics) and to assess drug effect (pharmacodynamics).

the frequency of seizures recorded in your diary will be compared with the baseline to evaluate any change.

if safety criteria are met after the single dose, you will be offered participation in the multiple‑dose phase.

this phase involves receiving several intrathecal injections of ion337 at increasing doses.

you will receive a series of intrathecal injections of ion337 according to the schedule defined by the study protocol.

each injection will be followed by an observation period during which vital signs, laboratory tests, and neurological status are checked.

the dose for each injection will be higher than the previous one, following an ascending‑dose design.

throughout the multiple‑dose phase, you will continue to have regular visits for safety assessments, including laboratory values, vital signs, ecg, and physical/neurological examinations.

blood and csf samples will be taken after each dose to assess drug concentration and activity.

your seizure diary will be reviewed to determine any change in seizure frequency compared with the baseline period.

at the end of the trial, a comprehensive evaluation will be performed to summarize the overall safety and tolerability of ion337.

final laboratory tests, ecg, neurological examination, and collection of blood and csf samples will be completed.

the data collected will be used to determine whether the medication was well tolerated and to assess its effect on seizure frequency.