A Study to Learn More About the Long-Term Safety and Effects of Felzartamab Infusions in Adults With Kidney Transplants Who Have Antibody-Mediated Rejection (AMR) or Microvascular Inflammation (MVI) (TRANSCEND/TRANSPIRE LTE) (TRANSCEND LTE)

An Open-Label Long-Term Extension Study of Felzartamab in Participants With Antibody-Mediated Rejection or Microvascular Inflammation Previously Enrolled in TRANSCEND or TRANSPIRE

In this study, researchers will learn more about a drug called felzartamab in people who have received a kidney transplant and then developed antibody-mediated rejection (AMR) or microvascular inflammation (MVI). AMR happens when the body's immune system creates donor-specific antibodies (DSAs) that attack the transplanted kidney. In late AMR, this typically happens more than 6 months after the kidney transplant. MVI is a condition where the small blood vessels in the transplanted kidney become inflamed. MVI can happen with or without DSAs. Both AMR and MVI can cause the transplanted kidney to stop working properly.

Two earlier studies looked at felzartamab in kidney transplant recipients. Study 299AR301 (TRANSCEND) (NCT06685757) included participants with AMR. Study 299AR201 (TRANSPIRE) (NCT07219043) included participants with MVI.

This study, 299AR302-299AR301 LTE, is a long-term extension of both of these "parent" studies. Participants who join this study will have the opportunity to receive felzartamab for up to 4 more years after completing their parent study.

The goal of this study is to learn more about the long-term safety and effects of felzartamab in people with kidney transplants. This study is part of a group of studies looking at long-term felzartamab use in people with organ transplants. This study is a substudy of the main study 299AR302.

The main question researchers will answer relate to safety. Namely, how many participants have adverse events during the study and how lab test results change over time. Adverse events are health problems that may or may not be caused by the study drug.

Researchers will perform kidney biopsies to track kidney health. Researchers will also study how felzartamab affects kidney inflammation, kidney function, immune activity, and overall health.

The study will be done as follows:

• Participants who complete the final visit of the treatment period in one of the parent studies can enroll in this study. This includes participants who stopped receiving felzartamab early but still attended their final visits.
• Participants who did not stop receiving felzartamab in their parent study will continue to receive felzartamab for up to 4 more years in this study. Participants may also stop felzartamab during this study at any time.
• Participants who stopped receiving felzartamab in their parent study will only attend study visits for health monitoring- they will not receive felzartamab.
• Felzartamab will be given as an intravenous (IV) infusion, which is a slow injection into a vein using a needle.
• Participants receiving felzartamab may have up to 27 study visits over 200 weeks with an additional safety follow-up visit after their final dose.
• Participants who are not receiving felzartamab may have up to 9 study visits over 200 weeks.

Study Overview

• Status: Enrolling by invitation
• Conditions: Antibody-mediated Rejection; Microvascular Inflammation
• Intervention / Treatment: Drug: Felzartamab

Detailed Description

The primary objective of this study is to evaluate the long-term safety of felzartamab. The secondary objectives of this study are to describe the ongoing efficacy of felzartamab on biopsy-proven histologic response (BPHR), microvascular inflammation (MVI) and graft function; and to evaluate pharmacokinetics (PK) and immunogenicity of felzartamab.

• Study Type: Interventional
• Enrollment (Estimated): 201
• Phase: Phase 3

Contacts and Locations

Study Locations

• United States
  • California
    • Los Angeles, California, United States, 90095
      • UCLA College of Medicine
  • New Jersey
    • West Orange, New Jersey, United States, 07039
      • Cooperman Barnabas Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Key Inclusion Criteria:

• Have completed the parent study Week 52 visit or will be completing Week 52 visit procedures (for participants who sign consent before reaching the Week 52 visit).

• Have received at least one dose of felzartamab in the parent studies, and had the following disposition status in the parent study:

  • Ongoing Treatment: Did not discontinue felzartamab treatment in the parent study and received a dose at the Week 44 visit.
  • Treatment Interrupted: Did not discontinue felzartamab treatment in the parent study and did not receive a dose at the Week 44 visit.
  • Off Treatment, On Study: Discontinued felzartamab treatment in the parent study and were not withdrawn from the study.

Participants who discontinued study treatment prior to receiving any doses of felzartamab in the parent study (i.e., those in the placebo group who discontinued before receiving felzartamab) are not eligible for enrollment in this substudy.

• For participants enrolling into this study who have not discontinued felzartamab treatment in the parent study only: The Investigator has determined that the participant could benefit from continued felzartamab treatment.

Key Exclusion Criteria:

• Met a treatment discontinuation criterion in the parent study but treatment was not discontinued (for example, because the criterion was met after the last dose of felzartamab in the parent study).

Note: Other protocol-defined inclusion/exclusion criteria apply.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Long-Term Extension: Felzartamab; Participants will receive felzartamab, intravenously (IV), once every 8 weeks for up to 200 weeks in the LTE period.	Drug: Felzartamab; Administered IV; Other Names: MOR202, MOR03087, TJ202, HIB202, BIIB148

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Number of Participants With Adverse Events (AEs), Serious Adverse Events (SAEs), and Adverse Events of Special Interest (AESI)	From first dose of study drug up to end of study follow-up (Up to Week 204)
Number of Participants who Discontinue Treatment due to an AE	From first dose of study drug up to end of study follow-up (Up to Week 204)
Number of Participants with Clinically Significant Laboratory, Vital Signs and Electrocardiograms (ECGs) Abnormalities	From first dose of study drug up to end of trial visit (up to Week 200)

Secondary Outcome Measures

Outcome Measure	Time Frame
Percentage of Participants Achieving Biopsy-proven Histologic Resolution (BPHR)	Up to Week 200
Microvascular Inflammation (MVI) Score	Up to Week 200
Change from Baseline in Estimated Glomerular Filtration Rate (eGFR)	Baseline, Week 200
Time to All-cause Allograft Loss	Up to Week 200
Time to Death Censored Allograft Loss	Up to Week 204
Felzartamab Serum Concentration	At Week 200
Number of Participants with Anti-drug Antibodies (ADAs) Against Felzartamab	At Week 200
Percentage of Participants Achieving an MVI Score of 0 by Each Biopsy Timepoint	Up to Week 200
Change From Baseline in Proteinuria	Baseline, Week 200

Collaborators and Investigators

• Sponsor: Biogen
• Investigators: Study Director: Medical Director, Biogen

Study record dates

Study Major Dates

• Study Start (Actual): April 16, 2026
• Primary Completion (Estimated): May 28, 2031
• Study Completion (Estimated): May 28, 2031

Study Registration Dates

• First Submitted: February 26, 2026
• First Submitted That Met QC Criteria: February 26, 2026
• First Posted (Actual): March 3, 2026

Study Record Updates

• Last Update Posted (Actual): June 30, 2026
• Last Update Submitted That Met QC Criteria: June 26, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Kidney Transplant Rejection; AMR, Felzartamab, Kidney Transplant
• Additional Relevant MeSH Terms: felzartamab
• Other Study ID Numbers: 299AR302-299AR301-LTE

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: In accordance with Biogen's Clinical Trial Transparency and Data Sharing Policy on https://www.biogentrialtransparency.com/

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No