An Efficacy and Safety Study of Imlifidase in Treatment of Antibody-Mediated Rejection in Kidney Transplant Patients

The purpose of this study was to investigate how efficiently the study medication imlifidase reduces the amount of donor specific antibodies (DSA) in comparison with plasma exchange (PE) therapy, in patients who have had an active or chronic active antibody mediated rejection (AMR) after being kidney transplanted. The purpose was also to investigate and compare safety for these two treatments.

Antibodies to human leukocyte antigens (HLAs) have a strong correlation with allograft injury and loss. Treatment with imlifidase, PE and immunoabsorption (IA) all aim to reduce antibody levels.

This study compared the reduction in DSA levels after treatment with imlifidase and PE in patients diagnosed with active or chronic active AMR (according to Banff 2017 or Banff 2019 criteria) having at least a 25% rise in serum creatinine compared with last measurement prior to the AMR. (Patients with delayed graft function and AMR within 10 days after kidney transplantation could be included regardless of serum creatinine level.) Eligible patients were randomized to either 1 dose of imlifidase (0.25 mg/kg) or 5-10 sessions of PEs (IA could replace PE at the discretion of the investigator).

All patients received pulse methylprednisolone Day 1 to Day 3, followed by a tapering schedule with prednisolone/prednisone. Patients randomised to imlifidase received their first dose of methylprednisolone before imlifidase was administered. The patients did also receive high dose intravenous immunoglobulin (IVIg) 3 days after imlifidase treatment or directly after the last PE. In addition a single dose of rituximab was given 5 days after completed IVIg infusion.

Eligibility Criteria:
Inclusion Criteria:

1. Signed Informed Consent obtained before any study-related procedures
2. Willingness and ability to comply with the protocol
3. Male and/or female donor kidney recipients age ≥18 years at the time of screening
4. Presence of DSA(s)
5. Meet the Banff 2017 criteria for active or chronic active AMR
6. At least 25% rise in serum creatinine compared to last individual value taken prior to the AMR. Patients with delayed graft function and AMR within 10 days after transplant (confirmed by kidney biopsy) can be included regardless of serum creatinine level
7. Women of child-bearing potential willing or able to use at least one highly effective contraceptive method throughout the study. In the context of this study, an effective method is defined as those which result in low failure rate (i.e. less than 1% per year) when used consistently and correctly
8. Men willing to use double-barrier contraception from the first day of treatment until at least 2 months after the dose of imlifidase, if not abstinent

Exclusion Criteria:

1. Previous treatment with imlifidase
2. Previous high dose IVIg treatment (2 g/kg) within 28 days prior to inclusion
3. Lactating or pregnant females
4. Significantly abnormal general serum screening lab results judged inappropriate for inclusion in the study by the investigator
5. Intake of other investigational drugs within 5 half-lives (or similar) of the product prior to inclusion
6. Clinically relevant active infection(s) as judged by the investigator
7. Any condition that in the opinion of the investigator could increase the subject's risk by participating in the study such as severe immune deficiency and severe cardiac insufficiency \[New York Heart Association (NYHA) Class IV\] or severe uncontrolled heart disease
8. Known allergy/sensitivity to imlifidase, IVIg and/or rituximab and the respective excipients
9. Patient unable to tolerate treatment with plasmapheresis or immunoadsorption, as judged by the investigator
10. Unsuitable to participate in the study for any other reason as judged by the investigator
11. Positive polymerase chain reaction (PCR) test for severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) infection
12. Current diagnosis or history of thrombotic thrombocytopenic purpura (TTP), or known familial history of TTP