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Evaluating mezagitamab in adults with late antibody-mediated rejection after kidney transplant

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What is this trial about?

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

A study is being conducted in adults who have received a kidney transplant and later develop Late antibody-mediated rejection (AMR), a condition where the body’s immune system starts to attack the transplanted kidney. The investigational medicine being tested is Mezagitamab, which is given as a small injection under the skin (subcutaneous injection). Participants will receive either this medication or a matching placebo that looks the same but does not contain the active drug.

The purpose of the study is to evaluate the safety and tolerability of the medication compared with the placebo. Participants will attend regular clinic visits over several months during which they will receive the assigned injection, have blood and urine samples taken, and undergo a kidney biopsy—a small tissue sample taken to check how the kidney is doing. Simple tests such as the estimated glomerular filtration rate (eGFR), which measures how well the kidneys filter waste, donor-derived cell‑free DNA (dd‑cfDNA), a marker that can show injury to the transplanted kidney, and the urine protein‑creatinine ratio (UPCR), which looks at protein levels in the urine, will be performed to monitor kidney health.

Throughout the study, doctors will closely watch for any side effects or problems that may arise, record any serious or treatment‑related events, and track changes in laboratory results and vital signs. The overall goal is to determine whether the medication can be given safely to people with this type of transplant complication and to gather information that may guide future treatment options.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline Evaluation

    After joining the study, you will undergo a baseline assessment that includes a physical examination, blood and urine tests, and a kidney biopsy to confirm the presence of late antibody‑mediated rejection.

    The results of these tests provide the reference point for all future measurements during the trial.

  2. Step 2

    Randomization and First Injection

    You will be randomly assigned to receive either mezagitamab or a matching placebo injection.

    Mezagitamab is administered as a subcutaneous injection (injection under the skin) using a solution for injection. The exact dose is defined by the study protocol and is given by a healthcare professional.

    If you are assigned to the placebo group, you will receive an injection that looks identical but does not contain the active drug.

  3. Step 3

    Regular Follow‑Up Visits and Additional Injections

    You will return to the clinic at scheduled intervals for safety monitoring and to receive additional injections according to the study schedule.

    During each visit, blood and urine samples will be collected to check kidney function, donor‑derived cell‑free DNA (dd‑cfDNA), and protein levels.

    Your health status and any side effects will be recorded at every visit.

  4. Step 4

    Week 24 Assessment

    At approximately 24 weeks after the first injection, you will have a repeat kidney biopsy.

    The biopsy will be examined for the microvascular inflammation (MVI) score, which combines glomerulitis and peritubular capillaritis findings.

    Laboratory tests for estimated glomerular filtration rate (eGFR), dd‑cfDNA, and urine protein‑creatinine ratio (UPCR) will be performed.

    Any adverse events that occurred up to this point will be reviewed.

  5. Step 5

    Week 48 Assessment

    Around 48 weeks after the first injection, you will undergo another kidney biopsy to determine whether the rejection activity has resolved.

    The same laboratory measurements (eGFR, dd‑cfDNA, UPCR) will be repeated.

    Safety assessments, including monitoring for serious adverse events, will continue.

  6. Step 6

    Week 70 Assessment (Arm B Only)

    If you are part of Arm B, a further biopsy will be performed at approximately 70 weeks.

    This biopsy and the accompanying lab tests evaluate long‑term changes in the MVI score and kidney function.

    Safety monitoring will be continued as before.

  7. Step 7

    End of Treatment

    When the treatment period ends, you will receive a final injection and undergo a final safety evaluation.

    Blood samples will be taken to measure the concentration of mezagitamab (or placebo) and to check for anti‑drug antibodies.

  8. Step 8

    Post‑Treatment Follow‑Up

    After the last dose, you will be monitored for a period defined by the study to observe any delayed side effects.

    Additional laboratory tests may be performed during this follow‑up to ensure continued safety.

Who can join the trial?

9 criteria

  • Age: You must be at least 18 years old and no older than 80 years (or meet the local legal adult age if it is higher than 18).
  • Informed consent: You (or your legal representative, if required) must sign a written consent form and any needed privacy permission before any study procedures begin.
  • Biopsy‑confirmed diagnosis: You need a kidney biopsy that shows an active or chronic active late antibody mediated rejection (AMR) (a type of kidney rejection caused by antibodies) that occurs more than 6 months after your transplant, and you must not have a definite T‑cell mediated rejection (TCMR) (a rejection caused by immune cells) of grade 1a or higher. A borderline TCMR is allowed. Only a small number of participants (up to 10%) with microvascular inflammation (MVI) = 1 can be included.
  • Biopsy timing: If you already had a biopsy, it must be done within 30 days of signing the consent form. If the biopsy is done during screening, it must be completed within 10 weeks of the date you are randomly assigned to a treatment group (randomization).
  • Previous treatment requirement: If you have received treatment for AMR or TCMR, a repeat biopsy and a test for donor‑specific antibodies (DSA) must be performed at least 6 weeks after stopping that treatment.
  • Functioning transplant: Your kidney transplant must be working and have been in place for at least 6 months.
  • Positive DSA test: You must have a positive result for human leukocyte antigen (HLA) class I and/or II donor‑specific antibodies, measured by a local lab using a single‑antigen bead assay, on the most recent test performed within 30 days of signing the consent form. Detailed HLA typing for both you and the donor must be available.
  • Kidney function: Your estimated glomerular filtration rate (eGFR) must be greater than 30 mL/min/1.73 m² at screening, calculated using the CKD‑EPI formula (a standard method to estimate kidney function).
  • Pregnancy testing for women: Women who could become pregnant must have a negative blood test for human chorionic gonadotropin (hCG) (a hormone that indicates pregnancy) at screening and a negative urine pregnancy test before receiving the first dose of the study medication.

Who cannot join the trial?

19 criteria

  • Having a transplanted organ that does not match the donor’s ABO blood type (blood‑type incompatibility).
  • Having had more than one organ transplant, such as multiple kidney transplants or combined organ transplants.
  • Having a rapid and severe loss of kidney function that is likely to need dialysis within the next 30 days.
  • Being enrolled in another study that uses an experimental drug or vaccine, or having taken another experimental drug within the past 4 weeks (or for a period equal to five drug half‑lives, whichever is longer).
  • Having received an anti‑CD38 medication in the past year, or having previously failed to control the disease with such a medication.
  • Having taken other strong immune‑suppressing medicines recently: within 6 months, drugs that block the complement system (e.g., eculizumab), proteasome inhibitors (e.g., bortezomib), IL‑6 or IL‑6R antibodies (e.g., tocilizumab), or anti‑CD20 antibodies (e.g., rituximab); within 6 weeks, intravenous or subcutaneous immunoglobulin (IVIG/SCIG) or plasma exchange (plasmapheresis).
  • Having a kidney biopsy that shows any of the following problems: acute T‑cell mediated rejection (Banff grade ≥ 1), severe blood‑vessel clotting disease (thrombotic microangiopathy), polyoma virus kidney disease, or a new or recurrent type of kidney inflammation (glomerulonephritis) – except for a harmless finding of IgA staining.
  • Having received a live or weakened‑virus vaccine within the past 4 weeks, or planning to receive such a vaccine during the study.
  • Having a recent serious infection, including active bacterial, viral, or fungal infection (except a common cold or nail fungus) within 2 weeks (with any antibiotics or antivirals finished at least 2 weeks before the first visit), significant cytomegalovirus (CMV) or BK virus in the blood (especially if treatment is needed or the virus level is high), any opportunistic infection or treatment for one within the past 2 months, active tuberculosis (TB) or a history of active TB, positive tests for latent TB (such as QuantiFERON, IGRA, or tuberculin skin test) without documented treatment for latent TB, or active infection with hepatitis B, hepatitis C, or HIV (including a positive hepatitis B core antibody test).
  • Having low blood counts or abnormal lab results at the screening visit, including very low lymphocyte count (<500 per mm³), very low neutrophil count (<1,000 per mm³), liver enzymes (ALT or AST) more than three times the normal upper limit, low hemoglobin (<9 g/dL), low immunoglobulin G (IgG) (<500 mg/dL), low platelet count (<100,000 per mm³), high bilirubin (>1.5 times the normal limit) (except people with Gilbert syndrome), or low total white blood cell count (<2,000 per mm³).
  • Having a medical or mental health condition that, in the investigator’s view, could interfere with taking the study drug, completing the study, increase risk, or make it hard to understand the results.
  • Having had major surgery within the past 3 months (or longer if the doctor decides).
  • Having had cancer (including myelodysplastic syndrome) in the past 5 years, except for certain skin cancers, superficial bladder cancer, or treated cervical carcinoma‑in‑situ.
  • Having a severe allergy or anaphylactic reaction to the protein part of the study drug (mezagitamab) or any of its ingredients.
  • Having chronic obstructive pulmonary disease (COPD) or asthma and a very low lung function test (forced expiratory volume in 1 second, or FEV1, less than 50 % of what is predicted for a healthy person).
  • Being able to breastfeed but not willing to stop breastfeeding from the first dose until 30 days after the last dose.
  • Being able to become pregnant but not willing to use at least one highly effective birth control method plus a barrier method (like a male condom) for at least 150 days after the last dose.
  • Being a sexually active man who can produce sperm, not sterilized, and not willing to use a barrier method plus at least one highly effective birth control method for any partner who could become pregnant, for at least 150 days after the last dose.
  • Being unwilling or unable to understand and follow all study procedures, including any digital tools or applications required for the trial.
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Investigated drugs

Mezagitamab is an experimental medicine given as a small injection under the skin. In this study it is being tested to see if it can help kidney‑transplant patients who have a problem called late antibody‑mediated rejection, where the body’s immune system attacks the transplanted kidney. Researchers are looking at how safe the medicine is and whether it can improve the health of the transplanted kidney compared with a placebo.

What is already known about the treatment

Mezagitamab - Mezagitamab is given as a subcutaneous injection, using a clear solution that is placed under the skin. It is currently an investigational drug being studied in a Phase 2 clinical trial, so it is not yet approved for routine medical use. The medication is being tested to treat late antibody‑mediated rejection in people who have received a kidney transplant. It works as a monoclonal antibody that binds to specific immune‑cell targets, helping to calm the immune response that can damage the transplanted kidney, and it is classified as an immunosuppressive biologic agent.

Investigated diseases

Late antibody‑mediated rejection (AMR) - It is a condition that can develop months to years after an organ transplant when the recipient’s immune system produces antibodies that target the transplanted organ. These antibodies cause inflammation and damage to the small blood vessels within the graft. Over time the injury can spread, leading to worsening function of the transplanted organ. The disease is identified by characteristic changes seen in biopsy tissue and by specific laboratory markers.
Trial detailsLast updated 22 Oct 2026
Age18+ yearsPhasePhase IITrial ID2026-526239-20-00Protocol codeTAK-079-2002Estimated enrolment44 patientsSponsorTakeda Development Center Americas Inc.

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