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Long‑term safety and tolerability of itepekimab in adults with inadequately controlled chronic rhinosinusitis with nasal polyps: an extension study

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What is this trial about?

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

The study focuses on adults who have Chronic rhinosinusitis with nasal polyps, a condition where the lining of the nose and sinuses stays inflamed for a long time and small growths called polyps develop, making breathing difficult and causing a runny nose or loss of smell. Participants will receive either the investigational medicine itepekimab, given as a subcutaneous injection (a shot under the skin), or a matched placebo that looks the same but does not contain the active drug.

The main goal is to assess the long‑term safety and tolerability of the medicine, meaning researchers will watch for any side effects or problems over an extended period. After the initial treatment period, participants will continue to attend regular visits where doctors will ask about health changes, perform a simple nasal examination, and may take a small blood sample to check drug levels. The study also records whether participants need additional treatments such as a short course of a systemic corticosteroid (a pill that reduces inflammation throughout the body) or sinus surgery.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Screening and enrollment

    After joining the study, you undergo screening procedures to confirm eligibility based on your chronic rhinosinusitis with nasal polyps condition.

    The screening includes medical history review, physical examination, and baseline measurements that will be used for later comparisons.

  2. Step 2

    Baseline visit

    At the baseline visit, detailed assessments of nasal polyps, symptom scores, and laboratory tests are performed.

    The results establish your starting point for evaluating safety and tolerability during the extension study.

  3. Step 3

    Randomization and first injection

    You are randomly assigned to receive either itepekimab or a matched placebo. the assignment is double‑blinded, meaning neither you nor the study staff know which product you receive.

    itepekimab is administered by subcutaneous injection (injection under the skin) using a pre‑filled syringe. the labeled dose is 00 mg, as defined by the protocol.

    The matched placebo is administered in the same manner, without active drug.

  4. Step 4

    Regular injection visits

    You return to the study site for additional injections according to the schedule defined in the protocol. each visit includes the same subcutaneous administration of either itepekimab or placebo.

    The exact interval between injections (for example, every 4 weeks) is specified by the study protocol, but is not detailed in the provided information.

  5. Step 5

    Safety monitoring visits

    At each visit, health professionals assess you for any adverse events, including serious or treatment‑emergent events.

    Laboratory tests may be performed to monitor blood chemistry and immune response, including detection of anti‑drug antibodies.

  6. Step 6

    Interim assessments

    Periodically, endoscopic examination of nasal polyps and symptom questionnaires are repeated to track changes from the baseline of the parent studies.

    Functional itepekimab concentration in serum may be measured to evaluate drug exposure.

  7. Step 7

    Final visit and study end

    At the conclusion of the extension period, a final assessment is performed, including safety evaluation, endoscopic examination, and collection of any remaining study data.

    After the final visit, the study drug is discontinued and you are no longer required to attend study visits.

Who can join the trial?

5 criteria

  • You must have chronic rhinosinusitis with nasal polyps (CRSwNP) and have finished a previous 52‑week study of the medicine itepekimab (study IDs EFC18418 or EFC18419).
  • Your last visit in that previous study (the end‑of‑treatment (EOT) visit) must have taken place no more than 5 days before you come to this study.
  • Both men and women are allowed to take part.
  • If you are a woman, you must not be pregnant or breastfeeding.
  • If you are a woman who could become pregnant (woman of childbearing potential), you must agree to follow the study’s birth‑control instructions during the treatment period and for at least 20 weeks after the last dose.

Who cannot join the trial?

4 criteria

  • Having been diagnosed with a malignancy (a type of cancer) during the earlier study, unless it was a skin cancer called squamous cell carcinoma or basal cell carcinoma.
  • Having any opportunistic infection (an infection that occurs when the immune system is weakened) during the earlier study, such as tuberculosis (TB) or other infections that suggest the immune system is not working well.
  • Having had a severe allergic reaction (anaphylactic reaction) or a whole‑body allergic reaction (systemic allergic reaction) that was linked to the study drug (IMP) and needed treatment during the earlier study.
  • Any other situation that caused the study drug (IMP) to be stopped permanently and early in the earlier trials.
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Investigated drugs

Itepekimab is a laboratory‑made protein given as a small injection under the skin. It works by blocking a part of the immune system that can cause swelling and growth of tissue in the nose. In this study, adults whose chronic sinus condition with nasal polyps was not well‑controlled received itepekimab to see if it remains safe and well‑tolerated when used for a long time. The medication is supplied as a clear liquid in a ready‑to‑use pre‑filled syringe.

What is already known about the treatment

  • Matched placebo for test product

    The placebo is provided as a sterile solution for injection in a pre‑filled syringe, administered by subcutaneous injection just like the active drug. It contains no active medicinal ingredient and is used only as a control in the study. As an inert substance, it has no therapeutic indication, mechanism of action, or pharmacological classification. Its purpose is to help compare safety and tolerability outcomes with the test medication.

  • Itepekimab

    Itepekimab is given as a subcutaneous injection using a pre‑filled syringe containing a clear solution for injection. It is an investigational monoclonal antibody that is currently being studied in clinical trials and has not yet received market approval. The drug is being tested for the treatment of chronic rhinosinusitis with nasal polyps, a condition where the nasal passages become inflamed and develop growths. Itepekimab works by attaching to a protein that triggers inflammation, thereby reducing the body’s allergic‑type response, and it is classified as an immunomodulating monoclonal antibody.

Investigated diseases

Chronic rhinosinusitis with nasal polyps - Chronic rhinosinusitis with nasal polyps is a long‑lasting inflammation of the nasal passages and sinuses that includes the growth of soft tissue lumps called polyps. The condition causes swelling, blockage, and excess mucus in the nose and sinus cavities. Over time the polyps can become larger, making it harder to breathe through the nose and leading to a feeling of fullness in the face. The inflammation may flare up repeatedly, causing periods of increased congestion, runny nose, and reduced sense of smell. Symptoms often persist for months or years, and the condition can gradually worsen if the underlying inflammation continues.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-522983-33-00Protocol codeLTS18420Estimated enrolment380 patientsSponsorSanofi-Aventis Recherche & Developpement

sourced from the EU Clinical Trials Register and site verification

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