A Phase 2a, multi centric, open label clinical study to explore the safety and tolerability, the pharmacokinetics and pharmacodynamics profile and first signs of efficacy of PTI5803 administered as adjunctive therapy with a 3-dose escalation regimen in patients >= 14 years of age with drug-resistant seizures associated to focal cortical dysplasia, followed by an optional open-label extension study.

Prior treatment

• Concomitant long-term treatment(s) already in place or planned during the study duration, except ASMs, which could be modified by the probenecid intake (any product containing probenecid, aspirin and salicylates, Methotrexate, Sulfenamides, Sulfonylureas, Pyrazinamide).
• Excessive drug or alcohol abuse within the past year, or current use of drugs or medications deemed abusive or dependent according to the investigator judgment.
• Participation to another interventional clinical trial in the last month or within 5 half-lives of the other IMP (whichever is longer) prior to inclusion and up to the end of the study.
• Any surgery planned during the study duration.
• Epilepsy surgery performed during the last 3 months before enrolment.

Other illness

• Hypersensitivity to Probenecid or any component of the IMP.
• HIV-infected patients.
• Psychogenic Non-Epileptic Seizures affecting epileptic seizures frequency quantification.
• Presence of a developmental and epileptic encephalopathy, including Lennox-Gastaut syndrome.
• Patient with a history of gastrointestinal ulceration and patients prone to gastrointestinal discomfort.
• Patient with pre-existing haematopoietic disorders.
• Schizophrenia and other psychotic disorders.
• History of suicide attempt in the last 1 years and/ or any suicidal ideation using C-SSRS questionnaire (indicated by a positive response (“Yes”) to either Question 4 or Question 5).
• Any significant medical or surgical condition (excepting epilepsy surgery) or uncontrolled medical illness (excluding epilepsy).

Lab values

• Severe renal insufficiency (creatinine < 50 ml/min).
• Hyperuricemia (>360mmol/L in woman; >420 mmol/L in man).
• Any clinically significant laboratory abnormalities or clinically significant abnormalities (physical examination, ECG) according to the judgement of the investigator.

Other

• Subject who, in the judgment of the Investigator, is likely to be non-compliant or uncooperative during the study, or unable to cooperate because of a language problem, poor mental development.
• Hyperuricosuria and uric lithiasis (Uraturia ≥ 700 mg/24 h under normal diet).
• Pregnant or breastfeeding women; individuals under guardianship, curatorship or legal protection measures; as well as any other individual belonging to a protected population within the meaning of Articles L.1121-5 to L.1121-8 of the French Public Health Code (or applicable regulatory framework), unless specifically justified and subject to reinforced safeguards provided for by law.
• Patient with gout.
• Lack of efficient contraception for heterosexually active females; breastfeeding.

• Male or female aged from 14 to 55 years of age.
• Signed and dated informed consent form must be obtained from the participant and/or their legal representative(s) prior to any study-specific procedures. Where applicable, assent must also be signed and dated by minors.
• The participant and/or their legal representative(s) must be willing and able to comply with all protocol-required visits and procedures, and especially able to keep accurate seizure Diaries (seizure and study treatment when appropriate).
• Subject is covered by Health Insurance System and / or in compliance with the recommendations of National Law in force relating to biomedical research.
• Body weight ≥ 50kg and BMI ≤40 kg/m2.
• Drug resistant seizures associated to FCD types I, II or III, with or without previous surgical management, with lesion diagnosis performed by MRI and / or histological assessment. Diagnosis of epilepsy should have been validated according to the International League Against Epilepsy 2017 classification criteria and patients should have experimented seizures for at least 2 years. Drug resistance is defined by adequate trials of at least 2 ASMs, which were given (and tolerated) at adequate therapeutic doses, without achieving sustained seizure freedom.
• Subject without major ongoing medical history, according to the investigator judgment.
• Subjects presenting at least 4 countable focal seizures (focal aware seizures with motor signs, focal seizures with impaired awareness with or without motor signs, focal seizures that lead to bilateral tonic-clonic seizures) per 28 days on average during the last three months despite current therapy/ies.
• Subjects receiving 1 to 3 antiseizure medications with stable doses during the last month before enrolment, not-including VNS and benzodiazepines. The VNS with an implanted device is allowed in addition to other ASMs if the surgery was performed at least 6 months before enrolment in the study, with stable stimulation parameters for at least 3 months before enrolment and all along the study. Battery should exceed 25% power prior to inclusion.
• Females of childbearing potential: commitment to use a highly effective method of birth control (which result in a low failure rate, i.e. less than 1% per year) when used consistently and correctly, such as combined hormonal contraception associated with inhibition of ovulation (oral, intravaginal, transdermal), progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable, implantable), intra uterine devices (IUDs), intrauterine hormone-releasing system (IUS), bilateral tubal occlusion) from at least one month before the time of informed consent signature and for 95 days (5 expected half-lives of the maximal dose plus 90 days) after the last study drug administration. Females with no heterosexual sexual activity shall be included with no commitment to use a method of birth control.
• Females of non-childbearing potential: defined as women who are either surgically sterilized for at least 6 months prior to inclusion or postmenopausal (amenorrhoea) for at least 12 months prior to inclusion.
• Normal dietary habits, including absence of ketogenic diet at least 3 months prior to inclusion.