Third Party Donor Derived EBV Specific T Cells for the Treatment of Refractory EBV-Related Malignancies in Immunodeficient Recipients
Authors: Prockop Susan E. , Doubrovina Ekaterina , Barker Juliet N , Baroudy Karim , Boulad Farid , Khalaf Ramzi , Kernan Nancy A. , Kobos Rachel , Papadopoulos Esperanza B. , Scaradavou Andromachi , Small Trudy N , Wasilewski Gloria , O'Reilly Richard J. 
Published: October 2019

Abstract
Abstract 577
Adoptive immunotherapy is an effective strategy for the treatment of EBV+ lymphoproliferative diseases (EBV-LPD) arising after an allogeneic hematopoietic stem cell (HSCT) or solid organ transplant (SOT). This approach is, however, often limited by an inability to generate donor derived in vitro expanded EBV-specific cytotoxic T-lymphocyte (EBV-CTL) lines in a timely manner and/or the fact that EBV CTL lines derived from HLA non-identical donors may be restricted by non-shared HLA alleles.
To date, we have treated 25 consecutive patients with an EBV LPD (N=20) or EBV Leiomyosarcoma (LMS) (N=5) with in vitro expanded EBV-CTLs derived from a donor other than the patient or their transplant (HSCT or SOT) donor. EBV CTLS were selected from a bank of 345 lines generated under GMP conditions from normal HSCT donors. Each donor was specifically consented for use of their T cells in patients other than their designated transplant recipient. Patients were recipients of unmodified (n=4), T cell depleted (n=5) or unrelated cord blood (n=5) HSCT, a solid organ transplant (n=6), a combined SOT and HSCT (n=1), or were non-transplanted patients with a primary immunodeficiency disease (n=4).
EBV disease in transplanted patients was of host origin in 5 of 10 evaluable HSCT recipients, in 3 of 4 evaluable solid organ recipients, and in the one patient who underwent a combined HSCT/solid organ transplant. Third party EBV-CTLs were selected on the basis of HLA matching at a minimum of 2/8 recipient alleles. Where possible EBV-CTLs were selected that were restricted through HLA alleles present on the EBV+ tumor. HLA restriction was evaluated in vitro in 20 EBV-CTL donor lines. The restriction was at a single HLA allele (n=12), at two alleles (n=6) and at >than two alleles (n=2).
Patients received infusions of 3rd party EBV-CTLs after failing a median of 2 prior therapies including rituximab in all but one case of EBV LPD. Four patients failed prior infusions with EBV-CTLs which were autologous (n=1), derived from their original HSCT (n=2) or from their solid organ donor (n=1). In two patients who progressed after treatment with EBV CTLs generated from their HSCT or organ donor, it was demonstrated that the donor derived EBV CTLs were restricted by a non-shared HLA allele.
Patients received a median of 5 infusions most at 1×106 EBV-CTL/kg/infusion. Four patients received EBV-CTLs from >1 3rd party donor. Nine patients achieved a completed response. Nine patients died of progressive disease, 6 shortly after the first infusion (17–29 days). Two patients with LMS achieved long term stable disease (46 and 8 months); 5 achieved partial remissions which have been sustained in 4 (11- 68 months), and 1 patient progressed after 10 months in a partial remission. Response to EBV CTL therapy did not correlate with the degree of HLA matching between donor and recipient or donor and tumor. Radiographic and clinical responses correlated with detectable increases in the frequency of CTL precursors in the blood. However durable EBV CTL engraftment was not seen.
One patient developed mild skin GvHD after infusion with 3rd party EBV-CTLs, but tolerated subsequent infusion of EBV-CTLs from an alternate 3rd party donor. Although no SOT recipient developed anti-HLA antibodies, one developed and episode of steroid responsive renal transplant rejection more than 6 months after infusion of EBV CTLs without evidence of donor (by STR analysis) in biopsied tissue.
This study demonstrates a high response rate among patients with otherwise refractory EBV malignancy treated with EBV specific 3rd party CTLs restricted by HLA alleles shared by the tumor. Treatment failures correlated with the use of EBV CTLs restricted by HLA alleles not shared by the tumor. In addition two patients with a primary immunodeficiency disease who were unable to mount an endogenous EBV T cell response had transient but not durable responses to 3rd party cells. EBV CTLs can be effective when selected based on restriction to shared alleles despite significant HLA disparity. The bank of EBV specific T cells can provide an immediate source of HLA partially matched appropriately restricted T cells for adoptive immunotherapy to treat EBV associated malignancy. This enables treatment early in the course of disease and the use of EBV-CTL lines previously prepared and characterized in terms of HLA restriction. This is anticipated to maximize the response rate.

Disclosures:
No relevant conflicts of interest to declare.