Adoptively-Transferred EBV-Specific T Cells to Prevent or Treat EBV-Related Lymphoproliferative Disease in Allogeneic HSCT Recipients - a Single Center Experience Spanning 22 Years

Epstein-Barr virus (EBV) reactivation post allogeneic hematopoietic stem cell transplantation (HSCT) can lead to the outgrowth of EBV-infected B cells and the development of post-transplant lymphoproliferative disease (EBV-PTLD). Since 1993 our group has used adoptive transfer of in vitro expanded EBV-specific T cells as a means to prevent or treat these EBV-driven lymphomas. In a series of Phase I and II clinical trials we have assessed the safety and clinical benefit associated with these transferred cells in allogeneic HSCT recipients. The T cell products infused were generated using 3 different manufacturing methodologies - [(i) EBV-transformed lymphoblastoid cell lines (EBV-LCLs) (~12 weeks manufacturing time), (ii) plasmid-nucloefected dendritic cells (DCs) (17 day manufacturing) and (iii) direct stimulation of PBMCs using overlapping peptide libraries (10 day manufacturing)] and were administered to either prevent (n=162) or treat (n=47) EBV reactivation/disease in a total of 209 allogeneic HSCT recipients ranging in age from 6 months to 63 years.

198/209 patients were infused with donor-derived virus-specific T cells (VSTs) and administered at doses ranging from 5x10⁶ to 1.2x10⁸ cells/m². Infusions were well tolerated, with acute graft versus host disease (aGvHD) grade I-II documented in just 10 patients, of which 2 cases were de novo. Chronic GvHD occurred in 13 patients and was extensive in 2. Other toxicities were seen only in patients with active disease and included localized swelling at the tumor site due to EBV-specific T cell infiltration (n=4), which was severe in 2 causing transient airway obstruction. An additional patient with bulky, Rituximab-resistant EBV-PTLD developed fever and sepsis-like signs post-infusion, coincident with a decrease in viral load, an increase in the frequency of circulating EBV-specific T cells and an elevation in plasma cytokines consistent with a cytokine release syndrome. However, the symptoms resolved within hours of administering steroids and an anti-TNF antibody and did not recur. Of 162 patients infused prophylactically only 1 (0.6%) developed EBV-PTLD, which occurred following the administration of steroids 3 weeks-post VST infusion. However, this patient responded to a second VST infusion after the steroids. 31 of 36 (86%) patients with elevated viral load (n=21) or biopsy-proven/probable LPD (n=15) achieved durable complete remissions and the infused cells persisted long term as demonstrated in 26 patients who received gene-marked VSTs that were detectable for up to 9 years post-infusion.

Based on the safety and efficacy profile of donor-derived EBV-specific VSTs we extended our approach to provide an "off the shelf" product to third party recipients, generating and banking T cell lines from 88 consenting normal donors. To date we have treated 11 patients, all of whom had drug-refractory EBV infections. Two patients were treated for elevated viral loads while 9 had established PTLD. Patients received 1-5 doses (fixed dose - 2x10⁷ cells/m²) with 3^rd party VSTs matching at one to three of six HLA alleles. Despite the HLA disparity the cells have proven safe with a single case of grade I GvHD reported. Of the 11 patients infused, 8 responded to therapy with 5 complete and 3 partial responses for an overall response rate of 73%.

Overall our experience with adoptively-transferred EBV-specific T cells over a 22-year period demonstrates the safety and efficacy of this approach for the prevention and treatment of post-transplant EBV disease.