Syk Inhibition in MItigating Lung Allograft Rejection (SIMILAR): A Trial to Evaluate the Safety and Tolerability of Fostamatinib in Lung Transplant Patients With Donor-Specific Antibodies

Background: People who have lung transplants often survive 6 or 7 years. But some people develop donor-specific antibodies (DSA) after their transplants; antibodies are proteins that attack foreign invaders in the body. Antibodies typically kill viruses and other agents that can cause disease. But when the antibodies attack a transplanted organ, they can cause the body to reject the new tissues. People who develop DSA after a transplant have a higher risk of death within 1 year. Objective: To test a drug called fostamatinib in people who develop DSA after a lung transplant. Eligibility: Adults aged 18 and older who developed DSA after a lung transplant. Design: Participants will continue with their standard care after a transplant. Fostamatinib is a pill taken by mouth. Some participants will take the study drug along with their standard care; others will take a placebo. A placebo is a pill that looks just like the real drug but contains no medicine. All participants will take 1 pill per day for 2 weeks. Then they will take 2 pills per day for the next 6 weeks. Participants will have clinic visits every 2 weeks while taking their pills. They will have a physical exam, with blood and urine tests, during each visit. If participants have fluid samples collected from their airways during their standard treatment, some extra fluid may be collected for this study. Participants will have a follow-up visit 4 weeks after they stop taking their pills.

NCT Number	NCT06948097
Lead Sponsor	National Heart, Lung, and Blood Institute (NHLBI)
Conditions	Lung Transplantation
Enrollment	30 participants
Start Date	2026-08-19
Primary Completion	2028-07-14 (estimated)
Study Completion	2028-07-14 (estimated)
Updated on ClinicalTrials.gov	2026-08-14