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Evaluation of Long-Term Efficacy and Safety of Obefazimod as Maintenance Therapy in Patients with Moderately to Severely Active Ulcerative Colitis

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What is this trial about?

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

This clinical trial is focused on studying the effects of a treatment for ulcerative colitis, a condition that causes inflammation and sores in the digestive tract. The treatment being tested is a medication called ABX464, which contains the active substance obefazimod. The study aims to evaluate how effective and safe this medication is when used as a long-term maintenance therapy for individuals with moderately to severely active ulcerative colitis.

The study is designed to compare the effects of taking ABX464 in two different doses, 25 mg and 50 mg, against a placebo. Participants will take the medication once daily. The study will be conducted over several phases, starting with a 44-week period to assess the medication's impact on improving symptoms and achieving remission, which means the symptoms of the disease are reduced or disappear. Following this, the safety and tolerability of the medication will be monitored for an additional 44 weeks. There is also a long-term extension phase lasting up to four years to further evaluate the safety of the treatment over time.

Throughout the study, participants will undergo regular check-ups to monitor their health and any changes in their condition. The goal is to determine whether ABX464 can provide a sustainable improvement in symptoms and quality of life for those living with ulcerative colitis. The study will also track any side effects or adverse events that may occur during the treatment period.

The research process

The trial runs in 10 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and Baseline Assessment

    After you join the study, you will be assigned at random to receive either ABX464 25 mg, ABX464 50 mg, or a matching placebo. The assignment is unknown to you and the study staff (double‑blind).

    You will undergo baseline examinations that include a colonoscopy to evaluate the condition of your colon, blood tests, and questionnaires about your symptoms of ulcerative colitis.

  2. Step 2

    Start of Study Medication

    On the day after baseline assessments, you will begin taking the study medication orally. The capsule contains the active substance obefazimod.

    If you were assigned to the 25 mg group, you will take one capsule containing 25 mg of obefazimod each day. If you were assigned to the 50 mg group, you will take one capsule containing 50 mg each day. If you received the placebo, the capsule looks identical but contains no active drug.

  3. Step 3

    Daily Medication Intake

    You will swallow the capsule with water once a day, preferably at the same time each day, for the entire duration of the trial phases in which you remain enrolled.

  4. Step 4

    Regular Clinic Visits During Part 1 (Weeks 0‑44)

    You will attend scheduled clinic visits approximately every four weeks. During each visit you will:

    • Report any side effects, referred to as treatment‑emergent adverse events (TEAEs).
    • Provide blood samples for safety laboratory tests.
    • Answer questions about your bowel symptoms.

    At selected visits, the study team may repeat colonoscopic examinations to assess endoscopic improvement.

  5. Step 5

    End of Part 1 Assessment at Week 44

    At week 44 you will undergo a comprehensive evaluation that includes:

    • A colonoscopy to determine whether you have achieved endoscopic improvement and/or endoscopic remission.
    • Clinical assessment to determine if you have reached symptomatic remission and clinical remission.

    The safety data collected up to this point will be analyzed to compare the effect of obefazimod with the placebo.

  6. Step 6

    Continuation into Part 2 (Weeks 45‑88)

    If you continue in the study, you will keep taking the same dose of the study medication (25 mg or 50 mg) once daily for an additional 44 weeks.

    The focus of this phase is the evaluation of safety and tolerability of the medication.

  7. Step 7

    Regular Clinic Visits During Part 2

    You will continue to attend clinic visits roughly every four weeks. At each visit you will:

    • Report any new or ongoing treatment‑emergent adverse events, including serious events that may require medical attention.
    • Provide blood samples for safety monitoring.
    • Undergo vital‑sign measurements and, if required, an electrocardiogram (ECG) to check heart function.

  8. Step 8

    End of Part 2 Assessment at Week 88

    At the end of week 88 you will have a final safety assessment for the double‑blind phase. This includes a colonoscopy, laboratory tests, and a review of any adverse events that occurred during the 88‑week period.

  9. Step 9

    Optional Long‑Term Extension (Up to 4 Years)

    You may choose to remain in the study for a long‑term extension lasting up to four years. During this period you will continue the same daily dose of obefazimod (25 mg or 50 mg).

    Clinic visits will be scheduled approximately every three months. At each visit you will:

    • Report any adverse events.
    • Provide blood samples for safety monitoring.
    • Undergo colonoscopic examinations at yearly intervals to assess ongoing endoscopic improvement and remission.

    The extension aims to collect additional information on the long‑term safety and tolerability of the medication.

  10. Step 10

    Final Study Completion and Safety Evaluation

    At the conclusion of the long‑term extension, you will have a final assessment that includes a colonoscopy, comprehensive laboratory testing, and a summary of all safety data collected during the four‑year period.

    You will be informed about the overall results of the study and any recommendations for follow‑up care.

Who can join the trial?

9 criteria

  • You must be at least 16 years old (or at least 18 years old if you live in the European Union, European Economic Area, Israel, Serbia, or Ukraine). If your country allows adolescents to join, you also need to weigh more than 40 kg and be at Tanner stage 5 (the final stage of puberty) when screened.
  • You need to have finished the earlier treatment study called ABX464‑105 or ABX464‑106 and have your clinical response information recorded.
  • You must have had a valid endoscopy (a procedure that uses a small camera to look inside your colon) at the end of that earlier study, and the results must be available for review on Day 1 of this trial.
  • You must be able to understand the study, and you must sign and date a written voluntary informed consent form before any study procedures begin. If you are underage, the consent must also follow your country’s rules for minors.
  • If you are a woman who could become pregnant (women of child‑bearing potential) or a man with a partner who could become pregnant, you must agree to follow the study’s contraception requirements (using birth‑control methods as described in the protocol).
  • You need to be willing and able to attend all study visits and follow the study procedures as described.
  • You should have a health‑insurance policy if your country or state requires it for participation.
  • For the Long‑Term Extension part of the trial, you must have completed the maintenance phase of the study.
  • For the Long‑Term Extension, both you and the investigator must agree that you have received, and will continue to receive, a benefit from staying in the study.

Who cannot join the trial?

11 criteria

  • Anyone who stopped taking the study medicine permanently during the first part of the trial (the induction study) cannot join the next phase.
  • If you still meet any of the reasons listed above for not joining the maintenance phase, you cannot take part in the long‑term extension.
  • During the maintenance phase you cannot start any medicines, doses, surgeries, or other procedures that are not allowed for ulcerative colitis, except for short‑term anti‑diarrhea or gut‑movement drugs used for acute diarrhea.
  • People who have developed a major illness such as primary sclerosing cholangitis (a liver disease), Crohn’s disease (another type of inflammatory bowel disease), removal of the colon (colectomy) or creation of an opening from the intestine to the outside of the body (diverting ileostomy), colon cancer, or colon polyps that show abnormal cells (low‑ or high‑grade dysplasia) are not eligible.
  • If you have an unstable health problem—examples include a severely swollen colon called toxic megacolon, very severe inflammation called fulminant colitis, a hole in the intestine (bowel perforation), uncontrolled loss of blood flow to tissues (ischemic disease), or advanced heart failure (NYHA class 3 or 4 symptoms)—you cannot join because the risk would be too high.
  • Anyone planning to be in another experimental (investigational) study at the same time as the maintenance study cannot participate.
  • Women who are pregnant, plan to become pregnant, or men and women who plan to cause a pregnancy during the study are not allowed.
  • Starting any prohibited medicines, doses, surgeries, or other procedures for ulcerative colitis during the induction phase (except brief anti‑diarrhea or gut‑movement drugs for acute diarrhea) will exclude you.
  • If lab test results change during the induction period in a way that the doctor thinks could be unsafe, you cannot continue in the study.
  • Anyone who intends to receive a live vaccine (a vaccine that contains a weakened form of the germ) while in the study cannot take part.
  • People who are confined to an institution (such as a prison or other facility) by a court or government order are not eligible.
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Investigated drugs

ABX464 is an oral capsule that contains the active ingredient obefazimod. In this study it is being tested as a maintenance therapy for people with moderately to severely active ulcerative colitis. Participants take one capsule each day, and the trial evaluates how well the medicine helps heal the lining of the colon and reduces symptoms, as well as how safe and well‑tolerated it is over time.

What is already known about the treatment

Obefazimod - Obefazimod is taken as a hard gelatin capsule by mouth once daily. It is still an investigational drug being studied in phase III clinical trials for ulcerative colitis. The medicine is meant to keep the disease under control in people with moderate to severe ulcerative colitis. It works by increasing a natural small molecule that reduces inflammation, acting as an oral immunomodulator.

Investigated diseases

Ulcerative colitis - Ulcerative colitis is a chronic inflammatory condition that affects the lining of the large intestine, especially the rectum and colon. It causes the intestinal lining to become red, swollen, and ulcerated, leading to ongoing irritation. In moderately to severely active cases, inflammation spreads over larger sections of the colon and the symptoms become more intense and persistent. The disease typically follows a pattern of flare-ups, where inflammation worsens, followed by periods of reduced activity. Over time, repeated inflammation can lead to thickening of the colon wall and changes in its function.
Trial detailsLast updated 31 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2022-500537-84-01Protocol codeABX464-107Estimated enrolment1 241 patientsSponsorAbivax

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