Experimental Off-the-Shelf T Cell Therapy Achieves 56.8% Response Rate in Rare, Often Fatal Brain Infection
核心洞察
A Phase 2 study of an investigational virus-specific T cell therapy achieved an overall response rate of 56.8% in 37 patients with progressive multifocal leukoencephalopathy (搜索) (PML), a rare and often deadly neurological condition with no approved treatments.
Complete viral clearance with stabilization or improvement of neurological symptoms was observed in 43.2% of patients, with responses typically occurring within 23 days of infusion.
The one-year overall survival rate for all treated patients was 61.1%, while patients who responded after their first infusion experienced a one-year survival rate of 93.3%.
In the largest study of its kind, an investigational off-the-shelf virus-specific T cell therapy developed at The University of Texas MD Anderson Cancer Center achieved an overall response rate of 56.8% in patients with progressive multifocal leukoencephalopathy (搜索) (PML), a rare and often fatal neurological condition for which no approved treatments currently exist. Findings from the Phase 2 study, published in Clinical Infectious Diseases, demonstrated rapid viral clearance and meaningful clinical responses, offering the first real hope for a potential standard treatment in a disease that has long represented one of the greatest unmet needs in neuroinfectious medicine.
"For decades, physicians have had no approved treatment to offer patients with PML, and this disease has long represented one of the greatest unmet needs in neuroinfectious medicine," said corresponding author Katy Rezvani, M.D., Ph.D., vice president and head of the Institute for Cell Therapy Discovery & Innovation, and professor of Stem Cell Transplantation and Cellular Therapy at MD Anderson. "Seeing rapid viral clearance and meaningful clinical responses in more than half of treated patients is extremely encouraging as we try to identify a potential standard treatment."
The Burden of PML
PML develops when the normally dormant JC virus (搜索) (JCV) reactivates in individuals with severely weakened immune systems. While up to 70% of adults carry the JCV symptom-free, the virus can become active in immune-compromised patients, including those with blood cancers, HIV/AIDS, organ transplants, autoimmune diseases, or treatment-related immunosuppression. When reactivated, the virus attacks the brain's white matter, leading to cognitive decline, speech difficulties, vision problems, weakness, balance disturbances, and progressive neurological deterioration. Mortality rates range from 50% to 80%, and among patients with underlying hematologic malignancies, mortality can exceed 90% within two months of diagnosis.
How the Therapy Works
The investigational therapy uses a bank of cryopreserved T cells from healthy donors that recognize the BK virus, which shares certain features with the JCV. These BK virus-specific T cells can therefore recognize and attack JCV-infected cells, providing patients with the virus-fighting immune cells they often lack due to their suppressed immune systems. Unlike patient-specific cellular therapies that may require weeks or months to manufacture, these cells are immediately available off-the-shelf and are delivered through an infusion similar to other cell therapies.
Key Efficacy Findings
Among the 37 patients treated in the Phase 2 study, the overall response rate reached 56.8%, with 43.2% achieving complete viral clearance accompanied by stabilization or improvement of neurological symptoms. Responses occurred rapidly, typically within 23 days of infusion. The one-year overall survival rate for all treated patients was 61.1%. Notably, patients who responded after their first infusion experienced a strikingly higher one-year survival rate of 93.3%.
The study also found that patients with lower JCV levels before treatment were more likely to respond, suggesting that earlier intervention may improve outcomes. Greater immune compatibility between donor T cells and recipients was also linked to better responses and survival.
Durability and Broad Applicability
Responses appeared to be durable. Patients who responded to therapy did not develop recurrent PML during follow-up, and there was no evidence of disease relapse after achieving a response. Among the 37 study participants, 23 had underlying hematologic malignancies — a particularly high-risk group. Responses were also observed in patients who developed PML after CAR T cell therapy or transplantation, as well as in individuals with HIV/AIDS and autoimmune diseases treated with immunosuppressive therapies.
"Many of the patients enrolled in this trial were among the highest-risk individuals we see," Rezvani said. "The fact that responses were durable and observed across patients with different underlying causes of immune suppression highlights the broad potential of this approach."
Building on Earlier Research
These findings build directly on earlier MD Anderson research published in the New England Journal of Medicine, which first demonstrated the potential of BK virus-specific T cells in a small group of patients with PML and provided the foundation for the current Phase 2 study. Researchers believe the results warrant further studies and support the development of BK-virus-specific T cell therapy as a potential standard treatment for PML. The clinical trial remains open and continues to enroll patients.