Inclusion Criteria:

• Diagnosis of refractory focal epilepsy

• Completed the Open-label Treatment Period of the parent study (RAP-219-FOS-201) with acceptable tolerability, per the Investigator’s assessment

• Stable RNS®system configuration settings (no setting changes, including changes to stimulation or detection) for 2 months prior to Visit 1 and up to 3 months after Visit 2 except with approval of Sponsor Note: RNS devices should be interrogated at a standard of care frequency, as per Investigator judgment

• Able and willing to provide written informed consent to participate in the study in accordance with International Council for Harmonisation-Good Clinical Practice guidelines, and willing and able to comply with all aspects of the protocol

• Good overall health (with the exception of epilepsy), as determined by the Investigator via medical history, physical examination, clinical labs, and other clinical assessment

• Aged 18 to 70 years

• Weight ≥45 kg by chart review at Visit 1 and a body mass index (BMI) between 18 to 45 kg/m2 , inclusive

Exclusion Criteria:

• Known hypersensitivity to RAP-219

• Use of perampanel within 8 weeks prior to Visit 1

• Pregnant or lactating, or intending to become pregnant during the course of the study

• Individuals of reproductive potential who do not agree to simultaneous use of 2 effective birth control methods throughout the study and for 22 weeks (for male participants) or 13 weeks (for female participants) following the last dose of study drug, when engaging in any sexual activity that comes with a risk of pregnancy. Must also agree to not donate sperm for 22 weeks or donate ova for 13 weeks following the last dose of study drug.

• Any clinically significant psychiatric diagnosis or psychological or behavioral problems which, in the opinion of the Investigator, would pose an additional risk to the participant by their participation in the study

• Any suicidal ideation with intent with or without a plan within 24 months prior to Visit 1 (ie, answering “Yes” to questions 4 or 5 on the Suicidal Ideation section of the Columbia-Suicide Severity Rating Scale [C-SSRS]), or any lifetime suicidal behavior (per the Suicidal Behavior section of the C-SSRS)

• Any clinically significant unstable or serious medical condition as assessed by medical history, including hepatic, respiratory, hematologic, unstable cardiovascular, renal, symptomatic peripheral vascular, or active and/or progressive or relapsing-remitting CNS disease that may confound the interpretation of the study results

• Has any of the following electrocardiogram (ECG) abnormalities at Visit 1, unless approved by the Medical Monitor and in communication with the Sponsor:

  • atrial fibrillation or flutter

  • paroxysmal supraventricular tachycardia

  • left bundle branch block

  • second-degree heart block, Mobitz type II

  • third-degree heart block (complete heart block)

  • ventricular tachycardia/fibrillation

• Has history of Class I-IV heart failure

• Corrected QT interval by Fridericia’s formula >470 msec for females and >450 msec for males at Visit 1

• If participants are on felbamate, they must have been on a stable dose for >12 months and have normal liver function tests. If participants are on vigabatrin, they must have been on a stable dose for >24 months and have documentation of normal visual fields within the last 3 months.

• History of multiple drug allergies or severe drug reactions, including dermatological (eg, Drug Reaction with Eosinophilia and Systemic Symptoms, or Stevens-Johnson syndrome), hematological, or organ toxicity reactions

• Any clinically significant laboratory abnormality which, in the opinion of the Investigator, should exclude the participant from the study

• Participation in any other interventional studies (aside from the parent study RAP-219-FOS-201) involving a study drug or device at least 12 weeks or 5 terminal elimination half-lives prior to Visit 1, whichever is longer, for the duration of the study and/or as required by local regulations. Participation in NeuroPace RNS longitudinal observational studies are not exclusionary.

• Unable or unwilling to comply with the study protocol and evaluations for the duration of the study

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 08/18/2025. Questions regarding updates should be directed to the study team contact.