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Study to measure bimekizumab concentration in breast milk of breastfeeding mothers with psoriasis, psoriatic arthritis, axial spondyloarthritis, or hidradenitis suppurativa

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What is this trial about?

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

This study will investigate how much bimekizumab passes into breast milk in mothers who are being treated with this medication. The study includes women with several chronic inflammatory conditions including psoriatic arthritis, axial spondyloarthritis, hidradenitis suppurativa, and plaque psoriasis. Bimekizumab is given as an injection under the skin using either pre-filled syringes or pre-filled pens.

The study will collect breast milk samples from mothers who are already receiving bimekizumab treatment as prescribed by their doctor. Samples will be taken over a period of two weeks, with additional samples collected depending on how often the participant receives their medication. The main purpose is to measure the amount of medication that passes into breast milk.

Participants must be at least 18 years old, currently breastfeeding, and have been receiving bimekizumab treatment for at least 12 weeks after giving birth. The study will monitor both mothers and infants for any side effects throughout the study period. The medication dose and schedule will continue as previously prescribed by the participant's doctor.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial participation phase

    You will begin participation after being on bimekizumab treatment for at least 12 weeks following delivery

    The medication is administered through subcutaneous injection (under the skin)

    You must be actively breastfeeding and plan to continue throughout the sampling period

  2. Step 2

    First sampling day

    On Day 1, a breast milk sample will be collected before your scheduled dose of bimekizumab

    The medication is available in different forms: pre-filled pen or pre-filled syringe, with doses of 160 mg or 320 mg

  3. Step 3

    Regular sampling period

    Breast milk samples will be collected on Days 2, 3, 5, 7, 9, 11, 13, and 15

    If you are on a two-week dosing schedule, sampling ends on Day 15

    If you are on a four-week dosing schedule, an additional sample will be collected on Day 29

    If you are on an eight-week dosing schedule, an additional sample will be collected on Day 57

  4. Step 4

    Safety monitoring

    Throughout the study period, any side effects or health changes will be monitored and recorded

    The study will measure the amount of bimekizumab present in breast milk

    The study will calculate how much medication might reach the infant through breast milk

  5. Step 5

    Study completion

    A final safety follow-up will be conducted after the sampling period ends

    Your participation in the study will conclude after the safety follow-up

Who can join the trial?

10 criteria

  • You must be 18 years or older when signing the consent form
  • You must be currently receiving bimekizumab treatment (a medication prescribed by your doctor) according to approved guidelines
  • You must be actively breastfeeding and plan to continue breastfeeding throughout the study period
  • Your decision to use bimekizumab and breastfeed must have been made before agreeing to participate in this study
  • You must have been using bimekizumab for at least 12 weeks after giving birth before the study sampling begins
  • You must not be pregnant and must not plan to become pregnant during the study period
  • You must have one of these conditions that is being treated with bimekizumab:
    • Psoriatic arthritis (joint inflammation related to psoriasis)
    • Axial spondyloarthritis (inflammation affecting the spine)
    • Hidradenitis suppurativa (a chronic skin condition)
    • Moderate to severe plaque psoriasis (a skin condition causing scaly patches)

Who cannot join the trial?

13 criteria

  • Male participants (study is for females only)
  • Age below 18 or above 55 years
  • Not currently breastfeeding
  • Not diagnosed with at least one of these conditions:
    • Psoriatic arthritis (joint inflammation related to psoriasis)
    • Axial spondyloarthritis (inflammation affecting the spine and joints)
    • Hidradenitis suppurativa (chronic skin condition with painful bumps)
    • Moderate to Severe Plaque Psoriasis (skin condition causing thick, scaly patches)
    • History of allergic reactions to similar medications
    • Currently participating in other clinical trials
    • Significant medical conditions that could interfere with the study
    • Unable to follow study procedures or attend scheduled visits
    • Not willing to provide breast milk samples for analysis
    • Currently using medications that could interact with the study drug
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Investigated drugs

Bimekizumab (also known by the brand name Bimzelx) is a biological medication that works by blocking specific proteins in the immune system. It is used to treat various inflammatory conditions. In this study, researchers are looking at how much of this medication passes into breast milk when nursing mothers receive the treatment. This helps understand the safety of the medication for breastfeeding mothers and their infants.

What is already known about the treatment

Bimekizumab (Bimzelx®) - A biologic medication administered through subcutaneous injection that belongs to the class of monoclonal antibodies. It works by specifically targeting and blocking two inflammatory proteins (IL-17A and IL-17F) that play a key role in causing inflammation in various autoimmune conditions. This medication is used in the treatment of several inflammatory conditions including psoriatic arthritis, axial spondyloarthritis, hidradenitis suppurativa, and moderate to severe plaque psoriasis. Clinical studies have shown that bimekizumab effectively reduces inflammation and improves symptoms in patients with these conditions by modulating the immune system's response.

Investigated diseases

  • Psoriatic arthritis

    A chronic inflammatory joint condition that occurs in some people with psoriasis. It causes joint pain, stiffness, and swelling that can affect any part of the body. The condition typically affects the fingers, toes, wrists, and lower back, causing joints to become swollen and tender. The symptoms can vary from mild to severe, and they may develop gradually or suddenly.

  • Axial spondyloarthritis

    A chronic inflammatory arthritis that primarily affects the spine and sacroiliac joints. The condition causes pain and stiffness in the back and hips, particularly in the morning or after periods of inactivity. It can lead to reduced flexibility in the spine and may affect other joints in the body. The symptoms typically begin in early adulthood and develop gradually over time.

  • Hidradenitis suppurativa

    A chronic skin condition that causes small, painful lumps to form under the skin. These lumps typically develop in areas where skin rubs together, such as the armpits, groin, and under the breasts. The condition can cause the formation of tunnels under the skin and scarring. The symptoms tend to be long-lasting and can flare up periodically.

  • Plaque psoriasis

    A chronic skin condition characterized by thick, red patches covered with silvery scales. These patches, known as plaques, most commonly appear on the elbows, knees, scalp, and lower back. The skin cells in affected areas multiply much faster than normal, causing the characteristic buildup of patches. The condition tends to go through cycles of flaring and remission.

Trial detailsLast updated 4 Oct 2026
Age18+ yearsPhasePhase ITrial ID2024-518689-29-00Protocol codeUP0122Estimated enrolment20 patientsSponsorUCB Biopharma

sourced from the EU Clinical Trials Register and site verification

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