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Study of ARGX-121 to Reduce Proteinuria in Adults with Primary IgA Nephropathy (IgAN)

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What is this trial about?

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

Immunoglobulin A nephropathy (IgAN) is a rare kidney condition in which an immune protein called IgA builds up in the tiny filters of the kidneys. This can cause blood and protein to appear in the urine and may lead to a gradual loss of kidney function. The study tests an investigational medicine called ARGX-121, which is given as a small injection under the skin (subcutaneous injection). A matching placebo, which looks the same but does not contain the active drug, is also used for comparison.

The purpose of the study is to determine whether ARGX-121 can lower the amount of protein that leaks into the urine in adults with IgAN. Participants will receive a series of injections over several months and will attend regular visits where urine samples are collected to measure protein levels, blood samples are taken to check kidney function (estimated glomerular filtration rate, a test that shows how well the kidneys filter waste), and basic health checks such as blood pressure and heart rhythm are performed. Throughout the study, safety is closely monitored by recording any side effects or unusual laboratory results.

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

    Randomization and baseline assessment

    After you join the study, you will be assigned randomly to receive either ARGX-121 or a matching placebo. the assignment is done by the study team and you will not know which one you receive.

    At the same visit, a series of baseline measurements will be taken, including a 24‑hour urine collection to measure the urine protein‑to‑creatinine ratio (UPCR), blood samples to evaluate kidney function and antibody levels, an electrocardiogram (ECG), and vital‑sign checks such as blood pressure and heart rate.

  2. Step 2

    First dose administration

    You will receive the first dose of the study medication by subcutaneous injection. the injection is given into the tissue just under the skin.

    The product information does not specify a numerical dose, frequency, or duration, so the exact amount and schedule will follow the protocol defined by the investigators.

  3. Step 3

    Regular follow‑up visits and ongoing dosing

    You will return to the clinic at regular intervals for additional injections of the study medication. each visit will include safety checks such as reporting any side effects, measuring vital signs, and performing laboratory tests.

    The study team will also collect urine samples periodically to monitor changes in proteinuria and will draw blood to assess kidney function and immune markers.

  4. Step 4

    Mid‑study assessment at week 24

    At week 24, a key evaluation will be performed. a 24‑hour urine collection will be repeated to calculate the change in UPCR from the baseline value.

    Additional blood tests will be done to measure kidney filtration rate (eGFR) and other laboratory parameters.

  5. Step 5

    Continued treatment and safety checks

    After the week‑24 visit, you will continue receiving the study medication according to the same injection schedule.

    The study team will keep monitoring for adverse events, repeat laboratory tests, and perform periodic ECGs to ensure safety.

  6. Step 6

    Final assessment at week 52 and study completion

    At week 52, the final study visit will occur. you will undergo the same set of measurements as at baseline, including a 24‑hour urine collection, blood tests for kidney function and antibody levels, vital‑sign checks, and an ECG.

    The data collected will be used to evaluate the overall effect of ARGX-121 on proteinuria, kidney function, and safety over the one‑year period.

Who can join the trial?

3 criteria

  • You must be a man or a woman who is not currently pregnant.
  • You must be at least 18 years old.
  • You must have a doctor’s diagnosis of Immunoglobulin A nephropathy (IgAN) that has been confirmed by a small tissue sample taken from your kidney (a biopsy).

Who cannot join the trial?

5 criteria

  • You cannot join the study if you have another autoimmune disease (a condition where your immune system mistakenly attacks your own body) or another health problem that would make it difficult to see how your IgAN is responding.
  • You cannot join the study if you have a secondary form of IgAN, which means the IgA deposits in your kidneys are caused by another disease rather than being primary IgAN.
  • You cannot join the study if you have a history of malignancy (any type of cancer) at any time.
  • You cannot join the study if you currently have an active infection that doctors consider serious or concerning.
  • You cannot join the study if you have had major surgery or an organ transplant (such as a kidney, liver, or heart transplant) recently.
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Investigated drugs

ARGX-121 is an experimental medicine being tested in this study. It is given as a subcutaneous injection, meaning it is placed just under the skin. The drug is designed to target a specific part of the immune system that is thought to cause damage in the kidneys of people with primary IgA nephropathy. By interfering with this process, researchers hope that ARGX-121 will lower the amount of protein that leaks into the urine (proteinuria), which is a key sign of kidney injury. Participants receive the medication during the trial so doctors can see how well it works and whether it is safe and well‑tolerated.

What is already known about the treatment

ARGX-121 - This medication is given as a subcutaneous injection in a clear solution meant for infusion or injection. It is an investigational monoclonal antibody that is currently in Phase 2 clinical trials and has not yet been approved for general medical use. The drug is being studied for adults with primary IgA nephropathy, a kidney disease that causes blood and protein to leak into the urine. It works by binding to a specific protein in the immune system that triggers inflammation, thereby lowering the harmful immune response in the kidneys, and is classified as an immunomodulatory monoclonal antibody.

Investigated diseases

Immunoglobulin A nephropathy (IgAN) - Immunoglobulin A nephropathy is a kidney disorder characterized by the buildup of IgA antibodies in the tiny filtering units of the kidneys (glomeruli). This deposition causes inflammation that can lead to blood and protein appearing in the urine. Over time, the inflammation may cause scarring of the glomeruli, gradually reducing the kidneys’ ability to filter waste. The disease often progresses slowly, with some people experiencing stable kidney function for many years while others show a steady decline. Changes in kidney function are typically monitored through measurements of urine protein and estimated glomerular filtration rate.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2026-525638-43-00Protocol codeARGX-121-26-IgAN2001Estimated enrolment111 patientsSponsorArgenx

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