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Long‑Term Safety and Tolerability of Probenecid (PTI5803) as Adjunctive Therapy in Patients ≥14 Years with Drug‑Resistant Focal Epilepsy due to Focal Cortical Dysplasia

Fast replyInvestigationalNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study looks at people aged 14 and older who have drug‑resistant focal epilepsy related to focal cortical dysplasia, a rare condition where a part of the brain develops abnormally and causes seizures that do not respond to usual medicines. The investigational medicine being tested is PTI5803, which contains the substance probenecid and is taken by mouth as prolonged‑release granules. The purpose is to evaluate the long‑term safety and tolerability of this added therapy.

Participants will continue to receive the study medicine for up to two years while keeping a diary of their seizures. Regular visits will include simple checks such as physical exams, weight measurement, blood tests, and an electrocardiogram (a test that records the heart’s rhythm). Researchers will also ask about overall well‑being, quality of life, and mood, and will monitor for any serious side effects, including any increase in thoughts of self‑harm. The study will track how many people stay on the medicine over time and whether any new safety concerns arise.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline assessments

    After joining the study, a series of baseline checks are performed. these include a physical examination, measurement of vital signs such as blood pressure and heart rate, recording of body weight and height, laboratory blood tests, and a 12‑lead electrocardiogram (ecg).

    Questionnaires that evaluate overall health, seizure impact, and mood are completed, and a seizure diary is started to record any seizures that occur before the study medication is taken.

  2. Step 2

    Start of medication

    The study medication, pt i5803, which contains the active substance probenecid, is provided as oral prolonged‑release granules.

    The prescribed amount is 16 ml taken by mouth each day. the medication is taken once daily for the entire period of the extension study, which may continue for up to 24 months.

  3. Step 3

    Daily medication and seizure diary

    The medication is taken at the same time each day, preferably with water.

    The seizure diary is continued throughout the study. each day you record the number of seizures, their type, and any circumstances that might be relevant. this information helps the study team evaluate changes in seizure frequency.

  4. Step 4

    Regular safety monitoring visits

    Follow‑up visits are scheduled at month 6, month 12, month 18, and month 24 after starting the medication.

    At each visit the study staff check for adverse events (any new or worsening health problems), repeat the physical examination, measure vital signs, record weight and height, and repeat laboratory tests and the ecg.

    Questionnaires that assess seizure control, quality of life, and mood are completed again during these visits.

  5. Step 5

    Evaluation of seizure control and quality of life

    The information from the seizure diary is compared with the baseline period to determine the change in monthly seizure frequency.

    Scores from the quality‑of‑life questionnaires and mood assessments are reviewed to see if there are any improvements or declines.

    The proportion of participants who remain seizure‑free for a 28‑day period is also calculated.

  6. Step 6

    Final assessment

    At the end of the study period (or earlier if the medication is stopped), a final set of assessments is performed. these include the same safety checks, laboratory tests, ecg, and questionnaires as in earlier visits.

    The final data are used to determine the long‑term safety and tolerability of pt i5803 as an additional therapy for drug‑resistant focal epilepsy related to focal cortical dysplasia.

Who can join the trial?

6 criteria

  • Signed a written informed consent form (or have a legal representative sign) showing you understand the study and agree to take part, following the study plan and international safety rules.
  • Finished the treatment part of the earlier study (A_CL_002) and kept at least 80% of the scheduled doses, recorded seizures in a diary, and took the study medication (IMP) as instructed, without stopping the drug.
  • Had no major changes or mistakes in following the study plan that could affect safety or the data, and do not have any current side effects (adverse events) that would make participation unsafe.
  • The doctor believes you are likely to get a benefit from being in the study.
  • If you are a woman who could become pregnant, you must agree to use birth‑control methods as required by the study.
  • You or your caregiver must be willing and able to follow all study procedures, including keeping a daily seizure diary to record any seizures.

Who cannot join the trial?

4 criteria

  • Has already met any of the withdrawal criteria from the earlier part of the study (meaning they were removed or stopped because of safety or other serious reasons).
  • Has another medical problem or personal situation that the doctor thinks makes participation too risky or would make it hard to follow the study rules.
  • Is a woman who is currently pregnant, is breastfeeding, or plans to become pregnant while the study is happening.
  • Plans to join another clinical trial that uses a different investigational drug, or plans to use any experimental device (a device still being tested and not approved for general use) to treat epilepsy or any other condition.
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Investigated drugs

PTI5803 is a medication that contains the active ingredient probenecid, which is taken by mouth in a form that releases the drug slowly over time. In this study, PTI5803 is given in addition to the patients’ usual seizure medicines to see how safe it is and how well patients can tolerate it when they have drug‑resistant seizures caused by focal cortical dysplasia. The goal is to understand any long‑term side effects and how the drug works together with other treatments to help control seizures.

What is already known about the treatment

PTI5803 - PTI5803 is taken by mouth as prolonged‑release granules, which are swallowed and dissolve slowly to give a steady amount of medicine. The product contains probenecid, a drug that is already approved and well described in medical literature for treating gout and for raising blood levels of some antibiotics. In this trial it is being tested as an add‑on treatment for drug‑resistant focal epilepsy linked to focal cortical dysplasia. Probenecid works by blocking kidney transport proteins that normally re‑absorb uric acid and certain drugs, so it increases the amount of these substances that leave the body; this classifies it as a uricosuric agent and a renal tubular secretion inhibitor.

Investigated diseases

Drug‑resistant focal epilepsy associated with focal cortical dysplasia - This condition is a type of epilepsy where seizures originate from a localized area of the brain that has abnormal development of the cortex. The abnormal cortical tissue, called focal cortical dysplasia, creates a region that generates repetitive electrical bursts, leading to seizures that are limited to one part of the body or consciousness. Because the seizures do not respond well to standard anti‑seizure medications, they tend to persist over time and may increase in frequency or intensity. The disorder often begins in childhood or adolescence, but can be identified at any age. Ongoing seizure activity can affect daily functioning and quality of life.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2026-525161-40-00Protocol codeA_CL_003Estimated enrolment15 patientsSponsorPanntherapi

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