Transferred Donor-Derived Virus Specific CD8+ T Cells That Have Been Transduced to Express a WT1-Specific T Cell Receptor Can Persist and Provide Anti-Leukemic Activity in AML Patients Post-Transplant
Authors: Bar Merav , Chapuis Aude G. , Schmitt Thomas M , Nguyen Hieu , Duerkopp Natalie A , Tom Mark F , Wagener Felecia D , Chaney Colette N , Bui Kieu-Thu , Heimfeld Shelly , Greenberg Philip D. 
Published: October 2019

Abstract
Relapse is the leading cause of death following allogeneic hematopoietic cell transplant (HCT) for high risk acute myeloid leukemia (AML). Antigen-specific T cells that selectively target leukemia associated antigen (LAA) have the potential to promote graft versus leukemia (GVL) activity without inducing graft versus host disease (GVHD). We previously demonstrated that transferred donor derived WT1-reactive CD8+ cytotoxic T-cells (CTL) clones can persist in post-transplant patients and mediate anti-leukemic activity (Chapuis et al. Sci Transl Med 2013; 5, 174ra27).
T cell receptor (TCR) gene transfer offers the potential to reproducibly provide every patient with a high avidity T cell response. In this study, escalating doses of donor-derived virus specific CD8+ T cells transduced to express a high affinity TCR specific for the HLA A*02:01-restricted WT1126-134 (RMFPNAPYL) epitope are being administered to high-risk AML patients after allogeneic HCT, with escalating doses withheld until persistence of the previous dose is at a frequency of ≤3% of peripheral blood CD8+ T cells. Currently, 9 patients have been treated on study and received a total of 22 infusions. Three patients have completed the four T cell infusions, with the last infusion followed by a two week course of Interleukin 2 (Fig.1). CTC Grade ≥ 3Adverse Events have been transient hypotension and a febrile reaction, and transient leukopenia, lymphopenia, and thrombocytopenia. No end-organ toxicities attributed to the infused T cells have been observed. One patient experienced exacerbation of acute GVHD after T cell infusions, and one patient developed chronic GVHD, although there is currently no evidence the GVHD in either patient reflected activity of the infused T cells.
Three patients, who were treated with T cells after a second allogeneic HCT for relapsed AML (two of whom had persistent/relapsed disease after second HCT), are alive with no evidence of disease 14, 8 and 7 months after initiation of T cell infusion (16, 26, and 9 months after second transplant) with no additional anti-leukemic therapy after completion of study treatment. One patient with high risk AML was treated prophylactically after allogeneic HCT for AML in second complete remission (CR2), and is alive with no evidence of disease 13 months after initiation of study treatment (15 months after transplant) (Table 1). Transferred CTL were detectable between 4 and >290 days after infusion (Table 1, Fig.2).
The study continues to accrue new patients, but the preliminary results suggest that transfer of donor-derived virus specific CD8+ T cells transduced to express a WT1-specific TCR can be accomplished without significant toxicity and that such therapy can potentially provide anti-leukemic activity. Additionally, no immunogenicity of transferred cells has been observed, suggesting the possibility of retreatment at later time points in case of subsequent relapse.
Abstract 3939. Table1. Clinical Outcomes Patient Diagnosis Disease status prior to study treatment Disease burden during T cell infusion Number of infusions CTL persistence (days after last infusion) Outcome* Survival* 1 AML Relapse 5 years after allogeneic HCT (medullary and extramedullary disease) Present 3 14+ Progressive disease Alive 2 AML Relapse 10 years after first allogeneic HCT. MRD early after second HCT Present 4(+IL2) 290+ Remission 16 months after transplant Alive 3 AML HCT at CR2. No evidence of disease after HCT Absent 4(+IL2) 20 Remission 15 months after transplant Alive 4 AML Relapse with extramedulary disease one year after second allogeneic HCT Absent 1 210+ Remission 26 months after transplant (8 months after treatment) Alive 5 MDS → AML Persistent disease after HCT Present 1 5+ Progressive disease Dead 6 AML Second HCT for relapse 4 years after first HCT Absent 4(+IL2) 4 Remission 9 months after transplant Alive 7 AML Persistence disease after HCT Present 1 30+ Progressive disease Dead 8 AML HCT in CR2. MRD early after transplant Present 1 50+ Ongoing treatment Alive 9 AML HCT in CR2. Relapse early after transplant Absent 3 14+ Ongoing treatment Alive
* as of 7/10/14
+ persistence T cells detected at most recent analysis
Figure 1. Treatment plan
Figure 1 (A) Arm 1 – No evidence of disease after HCT Figure 1. (A) Arm 1 – No evidence of disease after HCT
Figure 2 (B) Arm 2 – evidence of disease after HCT Figure 2. (B) Arm 2 – evidence of disease after HCT
Figure 2. In vivo persistence of WT1-specific donor derived transduced CTL
Figure 3 (Arrows indicate T cell infusions) Figure 3. (Arrows indicate T cell infusions)

Disclosures
Greenberg: Juno Therapeutics: Consultancy, Equity Ownership, Patents & Royalties, Research Funding.