First-in-Human Study Shows TRX103 Cell Therapy Accelerates Immune Recovery in Mismatched Stem Cell Transplants
核心洞察
TRX103, an off-the-shelf engineered Tr1 cell therapy, demonstrated exceptional safety with no dose-limiting toxicities in the first clinical study of patients undergoing HLA-mismatched hematopoietic stem cell transplantation.
The therapy significantly accelerated immune reconstitution, with donor-derived CD4 (搜索)-positive and FOXP3-positive regulatory T cells reaching healthy donor levels by day 42 post-transplant.
TRX103 induced the patient's own immune system to generate protective regulatory T cells through an "infectious tolerance" mechanism, potentially offering an alternative to lifelong pharmacologic immunosuppression.
A novel off-the-shelf cell therapy has shown promising early results in addressing one of the most challenging complications in stem cell transplantation. TRX103, an engineered Type 1 regulatory T (Tr1) cell therapy, demonstrated exceptional safety and accelerated immune recovery in the first clinical study of patients undergoing HLA-mismatched hematopoietic stem cell transplantation (HSCT).
The Phase 1 dose-escalation study, presented at the 2026 ASTCT/CIBMTR Tandem Meetings, represents the first clinical demonstration that an engineered, allogeneic cell therapy can induce a patient's own immune system to generate protective regulatory T cells. This breakthrough could potentially shift treatment away from lifelong pharmacologic immunosuppression toward restoring natural immune balance.
Exceptional Safety Profile and Successful Engraftment
Across all evaluated dose levels, TRX103 was well tolerated with no dose-limiting toxicities reported and no serious adverse events related to the product. All patients achieved successful engraftment and full donor chimerism following transplantation, marking a significant milestone for the therapy's clinical development.
"The dose-escalation phase concluded with no dose-limiting toxicities, allowing the team to move into an expansion phase," said Monzr M. Al Malki, MD, Principal Investigator and Professor at City of Hope (搜索), who serves as director of the Unrelated Donor Bone Marrow Transplant and Haploidentical Transplant Programs.
Pharmacokinetic analyses demonstrated dose-dependent persistence of TRX103 cells in circulation and significant increases in exposure between doses, indicating the therapy's biological activity scales appropriately with dosing.
Accelerated Immune Reconstitution Through "Infectious Tolerance"
The therapy's mechanism centers on inducing "infectious tolerance," a process that significantly accelerates recovery of donor-derived immune cells. TRX103 utilizes CD4 (搜索) T cells from healthy donors engineered to express IL-10, granting them the properties of Tr1 regulatory cells, while a dNGFR (搜索) marker enables cell tracking.
The clinical data revealed significant accelerated immune reconstitution of donor-derived CD4 (搜索)-positive T cells, reaching higher levels compared with historical controls. Most notably, FOXP3-positive T regulatory cells achieved levels comparable to healthy donors by day 42 post-transplant.
"We saw significant accelerated immune reconstitution of donor derived CD4 (搜索)-positive T cells. Those will reach higher levels compared with historical control that we already published in City of Hope (搜索) data. This was also the same for FOXP3-positive T regulatory cells," Al Malki explained.
The therapy also increased circulating tolerogenic dendritic cells, called DC 10, which express CD14 (搜索) and CD16 (搜索), alongside natural Tr1 cells. This combination of donor-derived DC 10, FOXP3-positive and natural Tr1 T-regulatory cells creates a tolerizing environment crucial for improved transplant outcomes.
Addressing Critical Unmet Need in Mismatched Transplants
Patients receiving mismatched transplants face prolonged immune deficiency, leaving them vulnerable to severe infections and relapse despite current standards of care such as post-transplant cyclophosphamide. The TRX103 data suggest the therapy can address this vulnerability by promoting rapid immune reconstitution.
"Patients receiving mismatched transplants can remain immunologically vulnerable for weeks to months," Al Malki noted. "In this early dose-escalation experience, TRX103 has shown a favorable safety profile alongside a compelling biologic signature, with dose-dependent persistence and early signals of rapid immune reconstitution."
The therapy showed faster and healthier recovery of lymphocyte subsets compared to patients undergoing transplant using post-transplant cyclophosphamide platforms without cellular therapy, meeting the study's main secondary objective.
Expanding Treatment Possibilities
The therapy's design is not restrictive to mismatched donors and could potentially be extended to matched donor transplants and even cord blood transplants. The study specifically targeted HLA-mismatched HCT recipients as they face the highest risk of graft-versus-host disease (搜索) and immune dysregulation.
"This therapy is not restrictive, and could be extended later to match donor, even cord blood transplants," Al Malki said, suggesting TRX103 could eventually broaden donor options and set new benchmarks for standard care.
Next Phase Focuses on Efficacy Endpoints
With the dose-escalation phase complete, the expansion phase will focus on confirming safety at the most biologically active dose level. Primary endpoints will include graft-versus-host disease (搜索) incidence and severity, transplant-related mortality, and immune recovery reflected in infection rates.
The low incidence of severe infections at optimal doses, combined with the induction of immune tolerance through regulatory T cell expansion, suggests TRX103 is behaving as designed and demonstrates biological activity. In a field where more than half of patients fail to achieve graft-versus-host disease (搜索)-free, relapse-free survival, these early results offer hope for improved outcomes.
The research team plans to evaluate efficacy in a larger, potentially multi-center study, representing a critical next step in validating this novel approach to transplant tolerance induction.