Safety and tolerability of OV329 as add‑on therapy in adults with drug‑resistant focal epilepsy

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What is this study about?

The trial focuses on adults with Focal epilepsy, a condition in which seizures begin in a specific area of the brain and are not adequately controlled by existing medicines (drug‑resistant). Participants will continue their usual seizure medication and will receive either the experimental oral capsule OV329 or a matching inactive pill, known as a placebo. The study drug is taken by mouth in a hard capsule form.

The purpose of the study is to assess how safe and well‑tolerated the new medication is when added to current therapy. The design is double‑blind, meaning that neither the participants nor the study staff know which capsule contains the active drug, and it is used as adjunctive therapy, meaning it is given in addition to the medicines participants are already taking.

After an initial screening visit, eligible individuals are randomly assigned to receive either the study drug or the inactive pill for several weeks, with regular clinic visits to check vital signs, heart rhythm, laboratory tests, and any side effects. At the end of the treatment period, participants have a final visit to review overall health and to discontinue the study medication under medical supervision.

1 screening and enrollment

after joining the study you will give written consent and provide information about your medical history and current epilepsy medication.

you will undergo basic measurements such as blood pressure, heart rate, a 12‑lead ECG (electrocardiogram), and laboratory tests to check blood and urine.

you will be asked to keep a seizure diary that records each seizure you experience before the study starts.

2 randomization (double‑blind assignment)

based on the information collected, the study will assign you to receive either the investigational product OV329 or a placebo.

the assignment is double‑blind, meaning neither you nor the study staff will know which one you receive.

3 start of treatment

you will take one hard capsule by mouth each day as instructed.

the capsule may contain OV329 or be a placebo; the exact amount of active substance is defined by the study protocol (listed as 0 mg in the product description).

treatment will continue for the entire study period, which lasts until the final study visit.

4 regular monitoring visits

you will attend scheduled clinic visits (for example weekly or monthly) to allow the study team to check your safety.

at each visit you will have your vital signs (blood pressure, pulse) measured, a repeat ECG, and laboratory tests performed.

you will continue to record seizures in your diary and answer questions about mood and thoughts of self‑harm using the C‑SSRS (a questionnaire that assesses suicidal ideation).

5 end of treatment assessment

when the treatment period ends you will stop taking the capsule.

a final assessment will be performed, including the same safety checks (vital signs, ECG, labs) and review of your seizure diary.

6 post‑treatment follow‑up

a follow‑up visit may be scheduled after the end of treatment to ensure that no delayed side effects occur.

you will again have vital signs, ECG, and laboratory tests, and you will be asked about any new symptoms.

Who Can Join the Study?

Give written consent after the study is fully explained to you.
Have a normal heart test called a 12‑lead ECG with no important problems and a corrected QT interval (called QTcF) of 450 ms or less for men and 470 ms or less for women.
Show a resting heart rate while lying down (supine) between 45 and 100 beats per minute at the screening visit and before starting treatment.
If you are tested for COVID‑19, a positive result that stays positive for at least 14 days during the 28‑day screening period will keep you from enrolling until you test negative.
Agree not to use illegal drugs or alcohol while you are in the study.
If you are a woman who could become pregnant, you must use a highly effective birth‑control method (such as an intrauterine device, hormonal IUD, tubal ligation, hormonal implant, injectable hormone, or a vasectomized partner) from screening until one month after the last dose. Oral birth‑control pills alone are not enough, and abstinence counts only if you completely avoid heterosexual intercourse for the whole risk period.
If you are a man who has gone through puberty, you must use a condom or agree to abstain from sex from screening until the study ends, unless you have had a permanent vasectomy.
Be between 18 and 65 years old when you sign the consent form.
Have a diagnosis of drug‑resistant focal epilepsy for at least 2 years, meaning at least three appropriate seizure medicines have not controlled your seizures. This diagnosis must be confirmed by your doctor using your medical history, an electroencephalogram (EEG) (a test that records brain activity), and/or a brain scan (CT or MRI) done within the past 10 years.
Have recorded at least 4 countable focal seizures every 28 days during the 8 weeks before screening and during a 4‑week baseline period, and you must not have had 21 straight days without a seizure during that baseline. Only certain seizure types are allowed; seizures without any visible signs (called FPC) are not eligible unless you also have other seizure types.
Be taking a stable regimen of 1‑3 antiseizure medicines (or non‑drug therapies such as a vagus nerve stimulator VNS, responsive neurostimulation RNS, or a ketogenic diet) for at least 1 month before screening, with no expected changes in dose or type during the 12‑week treatment period. Specific rules apply:
- Barbiturates must have a stable dose for at least 1 month.
- If you have a VNS or RNS device, it must have been implanted for at least 1 year, with settings unchanged for at least 3 months and a battery that will last through the study.
- The ketogenic diet must be stable for at least 1 month.
- Long‑term benzodiazepines are allowed if the dose is stable for at least 1 month; occasional rescue doses are permitted.
- Felbamate is allowed only if you have taken it at a stable dose for at least 18 months with normal liver blood tests.
Be able to keep a daily seizure diary that accurately records each seizure.
Be willing and able to follow the study’s procedures, diet, visit schedule, and understand both spoken and written instructions.
Weigh at least 50 kg and have a body‑mass index (BMI) between 18.0 and less than 40.0.
Have a resting blood pressure while lying down that is between 90 and 145 mm Hg systolic (top number) and no higher than 90 mm Hg diastolic (bottom number) at screening and baseline.

Who Cannot Join the Study?

Have taken OV329 before the study.
Have stomach problems such as gastritis (inflamed stomach lining), have had stomach or intestinal surgery (including gastric bypass), have a liver disease (hepatic disorder), or have any condition that might change how the study drug is absorbed, spread, broken down, or removed from the body. Also, if you had diarrhea, loose stools, or constipation in the two weeks before the first dose.
Have used illegal drugs or misused prescription drugs within the past two years.
Have a known allergy or unusual reaction (hypersensitivity or idiosyncratic reaction) to the study drug or medicines that are similar.
Take dietary supplements or herbal products and have not used them regularly for at least six months before screening, or cannot keep the dose steady during the 12‑week study period.
Have a history of not taking medicines as prescribed (chronic non‑compliance).
Plan to have any surgery during the screening, treatment, tapering off, or follow‑up phases.
Are considered at risk for suicide, have attempted suicide in the past two years, or have had serious thoughts of suicide in the past year, as judged by the study doctor using a questionnaire called the C‑SSRS (Columbia‑Suicide Severity Rating Scale).
Are pregnant or are breastfeeding a baby.
Have taken another experimental (investigational) drug or used an experimental medical device within 30 days before screening, or plan to use any experimental drug or device at any time during the study.
Started epilepsy treatment less than two years ago.
Have other types of epilepsy such as generalized epilepsy, Lennox‑Gastaut syndrome, juvenile myoclonic epilepsy, absence epilepsy, or have non‑epileptic seizures in the past year.
Have fewer than four countable focal seizures in a 28‑day period, or have been seizure‑free for 21 consecutive days during the baseline monitoring period.
Are currently using the medication vigabatrin, or have used it in the past unless you have had stable eye‑vision (visual field) test results twice in the past year after stopping the drug.
Have abnormal laboratory test results that suggest a serious disease, especially liver enzymes (ALT, AST, gamma‑glutamyl transferase, alkaline phosphatase) more than 2.5 times the normal upper limit, total bilirubin more than twice normal, or a blood‑clotting test (INR) over 1.5, unless another non‑liver cause is clearly identified.
Have uncontrolled diabetes (HbA1c greater than 7%), a history of alcohol abuse in the past two years, or untreated vitamin B12 or copper deficiency.
Have a history of heart or blood‑vessel disease, stroke, a serious uncontrolled illness, a heart attack within six months, heart failure, a condition called long QT syndrome (which affects the heart’s electrical rhythm) or a prolonged QT interval on an ECG (over 450 ms for men or 470 ms for women), or other significant laboratory abnormalities.

Where you can join this trial?

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Other Sites

Site Name	City	Country	Status
Uniidsykim Hhizeant Mrwtujrknw	Maastricht	The Netherlands

Trial status

Country	Status	Recruitment Start
The Netherlands	Not yet recruiting	31.10.2026

Trial locations

OV329
OV329 is an experimental medicine being studied as an additional treatment for adults whose focal epilepsy does not respond well to existing drugs. It is taken by mouth in a hard capsule. In the trial, participants continue their usual antiseizure medicines and add OV329 to see if it can help reduce seizure frequency while being safe and well‑tolerated. The study compares people who receive OV329 with those who receive a placebo, but only the description of OV329 is provided here.

Investigated Diseases:

Partial seizures

Focal epilepsy – Focal epilepsy is a type of seizure disorder that starts in one specific area of the brain. The abnormal electrical activity originates in that region and can spread to other parts. Seizures may involve simple motor movements, sensory changes, or altered awareness, depending on the brain area involved. Over time, seizures can become more frequent or change in appearance. Some people experience only occasional episodes, while others have recurrent events that affect daily life.

Trial ID:

2026-525896-23-00

Protocol code:

OV329-26-001

Trial Phase:

Therapeutic exploratory (Phase II)

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Safety and tolerability of OV329 as add‑on therapy in adults with drug‑resistant focal epilepsy

What is this study about?

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