αβ T-cell graft depletion for allogeneic HSCT in adults with hematological malignancies

Abstract

We conducted a multicenter prospective single-arm phase 1/2 study that assesses the outcome of αβ T-cell depleted allogeneic hematopoietic stem cell transplantation (allo-HSCT) of peripheral blood derived stem cells from matched related, or unrelated donors (10/10 and 9/10) in adults, with the incidence of acute graft-versus-host disease (aGVHD) as the primary end point at day 100. Thirty-five adults (median age, 59; range, 19-69 years) were enrolled. Conditioning consisted of antithymocyte globulin, busulfan, and fludarabine, followed by 28 days of mycophenolic acid after allo-HSCT. The minimal follow-up time was 24 months. The median number of infused CD34+ cells and αβ T cells were 6.1 × 106 and 16.3 × 103 cells per kg, respectively. The cumulative incidence (CI) of aGVHD grades 2-4 and 3-4 at day 100 was 26% and 14%. One secondary graft failure was observed. A prophylactic donor lymphocyte infusion (DLI) (1 × 105 CD3+ T cells per kg) was administered to 54% of the subjects, resulting in a CI of aGVHD grades 2-4 and 3-4 to 37% and 17% at 2 years. Immune monitoring revealed an early reconstitution of natural killer (NK) and γδ T cells. Cytomegalovirus reactivation associated with expansion of memory-like NK cells. The CI of relapse was 29%, and the nonrelapse mortality 32% at 2 years. The 2-year CI of chronic GVHD (cGVHD) was 23%, of which 17% was moderate. We conclude that only 26% of patients developed aGVHD 2-4 after αβ T-cell-depleted allo-HSCT within 100 days and was associated with a low incidence of cGVHD after 2 years. This trial was registered at www.trialregister.nl as #NL4767.

Graphical abstract

Figure 1.

Graft composition after αβ T-cell depletion. Total number of CD34⁺ cells, αβ T cells, γδ T cells, NK cells, and B cells in the infused allograft were measured by flow cytometric analysis. Bullets represent individual numbers; dash represents the median.

Figure 2.

Cumulative incidence aGVHD and cGVHD. The cumulative incidence (CI) of GVHD is defined as time to onset of GVHD, with relapse and death as competing events. (A) CI of aGVHD ≥grade 2-4 (left) and aGVHD ≥3-4 (right). (B) CI of mild cGVHD (left), moderate GVHD (right), or severe cGVHD (bottom left). Dashed lines indicate a 95% confidence interval (95% CI).

Figure 3.

Cumulative incidence of viral reactions. Cumulative incidence of CMV and EBV infections are calculated with relapse and death as competing events. (A) CI of CMV reactivation for patients at risk (defined as seropositive recipients, R+). (B) CI of EBV reactivation. Dashed lines indicate 95% CI.

Figure 4.

Immune reconstitution. Peripheral blood samples were collected at the indicated time intervals after allo-HSCT. Absolute numbers of indicated immune subsets were measured by flow cytometric analysis. Circles indicate individual values; lines indicate the median value; dashed lines represent the normal range in healthy individuals.

Figure 5.

NK cell analysis. NK cell repertoire at 3 and 6 months after allo-SCT. Where indicated, transplant samples were stratified for CMV-reactivated recipients (filled symbols) or CMV-seronegative recipients (open symbols). Bullets depict recipients of the prospective αβ T-cell–depleted cohort; squares depict recipients of the T-cell–replete cohort; triangles depict healthy donors. All cell fractions are presented as fraction of NK cells. Statistics: Mann-Whitney U test (*P < .05; **P < .01). Comparisons without indication of significance where not statistically different.

Figure 6.

Clinical outcome. Clinical outcomes are shown with a 2-year follow-up. OS (A) and EFS (B) were estimated by the Kaplan-Meier product. (C) The CI of relapse is defined as time to relapse, with death as a competing event. (D) NRM is defined as time to death, without relapse or progression. Dashed lines indicate 95% CI.