UCLA Advances Kidney Transplantation: Delayed Donor Stem Cell Infusion Shows Promise

A UCLA clinical trial reports that a delayed donor-derived hematopoietic stem cell infusion allowed withdrawal of maintenance immunosuppression in three of six patients in an early phase 1/2 cohort—an initial signal that half of treated participants achieved operational tolerance.

This finding points to a possible pathway to reduce lifelong immunosuppression for select kidney transplant recipients, with potential to lower long-term drug toxicity and improve quality of life.

The intervention administers donor hematopoietic stem cells months to years after the index kidney transplant following a brief outpatient conditioning regimen designed to permit engraftment without repeating major operative risks. The reported phase 1/2 design has treated six patients to date and has expanded eligibility to recipients transplanted up to 20 years earlier. Trial assessments use prespecified clinical endpoints: operational tolerance, successful immunosuppression withdrawal, sustained graft function, and safety monitoring for acute or chronic rejection and other adverse events.

Early outcomes show three of six treated patients are fully off maintenance immunosuppression; the others are either tapering doses or maintaining reduced regimens, with short-term stable graft function reported. Safety data to date do not demonstrate unambiguous graft loss or widespread severe rejection, and adverse events are described as manageable within the study’s monitoring protocols. Together these results support the feasibility of tolerance induction using a delayed-infusion protocol in a selected, well-matched cohort.

A $6.7 million grant will expand enrollment and fund mechanistic studies to identify biomarkers and immune signatures linked to tolerance. That support will enable inclusion of additional patients—including those transplanted up to 20 years earlier—and finance planned analyses to test generalizability and guide next-step designs in larger or randomized cohorts.

Broader testing will require prespecified monitoring schedules, explicit candidate-selection criteria that prioritize stable graft function and donor–recipient matching, and endpoints combining sustained immunosuppression withdrawal with durable graft function plus mechanistic biomarkers. The study team plans staged enrollment and serial mechanistic sampling during the upcoming accrual period, with operational milestones and interim analyses scheduled over the next 12–24 months to determine whether delayed infusion can move from selected cases to wider clinical testing.