Clinical effects of administering leukemia-specific donor T cells to patients with AML/MDS after allogeneic transplant

Abstract

Relapse after allogeneic hematopoietic stem cell transplantation (HCT) is the leading cause of death in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Infusion of unselected donor lymphocytes (DLIs) enhances the graft-versus-leukemia (GVL) effect. However, because the infused lymphocytes are not selected for leukemia specificity, the GVL effect is often accompanied by life-threatening graft-versus-host disease (GVHD), related to the concurrent transfer of alloreactive lymphocytes. Thus, to minimize GVHD and maximize GVL, we selectively activated and expanded stem cell donor-derived T cells reactive to multiple antigens expressed by AML/MDS cells (PRAME, WT1, Survivin, and NY-ESO-1). Products that demonstrated leukemia antigen specificity were generated from 29 HCT donors. In contrast to DLIs, leukemia-specific T cells (mLSTs) selectively recognized and killed leukemia antigen-pulsed cells, with no activity against recipient's normal cells in vitro. We administered escalating doses of mLSTs (0.5 to 10 × 107 cells per square meter) to 25 trial enrollees, 17 with high risk of relapse and 8 with relapsed disease. Infusions were well tolerated with no grade >2 acute or extensive chronic GVHD seen. We observed antileukemia effects in vivo that translated into not-yet-reached median leukemia-free and overall survival at 1.9 years of follow-up and objective responses in the active disease cohort (1 complete response and 1 partial response). In summary, mLSTs are safe and promising for the prevention and treatment of AML/MDS after HCT. This trial is registered at www.clinicaltrials.com as #NCT02494167.

© 2021 by The American Society of Hematology.

Figures

Graphical abstract

Figure 1.

In vitro characteristics of mLSTs. Leukemia TAA-directed activity of nonmanipulated donor lymphocytes (A) and ex vivo expanded mLSTs (B). Mean ± SEM. mLSTs did not kill normal recipient cells (C), but killed TAA-pulsed normal cells tested at E/T ratios from 80:1 to 5:1 (D). Mean ± SEM. Polyclonality of mLSTs, as assessed by TCR-vβ deep sequencing (E) and immunophenotyping (F). (C,E-F) Each symbol represents an individual product.

Figure 2.

Clinical outcomes: adjuvant arm. (A) Swimmer plots depicting outcomes after infusion of mLSTs in patients with AML/MDS who were in remission at the time of infusion. *Individuals who relapsed after HCT but were in morphological remission at the time of T-cell infusion. (B) Kaplan-Meier estimates of LFS in the adjuvant group.

Figure 3.

Mechanisms of immune escape at relapse. (A) Summary of mechanisms of immune escape observed in each relapsing patient. (B) Expression of PD-L1 as estimated by IHC in relapsing tumors obtained from patients 3 and 6. Original magnification ×400. (C) MRI imaging in 3 individuals demonstrating extramedullary (immune-privileged anatomic site) relapses. (D) Representative flow cytometry plot from patient 1 depicting loss of HLA-DR expression at relapse. (E) Downregulation of expression of target TAAs (WT1, PRAME, Survivin) on relapsing AML/MDS cells in patient 7. IHC; original magnification, ×400.

Figure 4.

Clinical outcomes: active disease arm. Swimmer plots depicting outcomes after infusion in patients with AML/MDS who had refractory disease at the time of infusion.

Figure 5.

Complete remission from active AML after mLST infusion. MRI images of AML invading bone before (A) and after (B) mLST infusion. (C) Relapsed AML cells (CD33+ blasts; IHC). Hematoxylin and eosin; original magnification ×400. Cells were surrounded by a dense infiltrate of CD3+ T cells. IHC; original magnification ×10. Changes in frequency of circulating mLSTs after infusion, as measured by IFN-γ ELISpot (D) and polyclonality of circulating WT1-specific T cells, as estimated by ICS (E) performed on fresh PBMCs at the 6-month time point. (F) Change in the frequency of mLST-derived TCR clones represented as fold change from baseline in the repertoire frequency.