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The safety and efficacy of ibrutinib (420 mg) in chronic lymphocytic leukemia (CLL) were evaluated in a phase 2 study; 51 patients had TP53 aberration (TP53 cohort) and 35 were enrolled because of age 65 years or older (elderly cohort). Both cohorts included patients with treatment-naive (TN) and relapsed/refractory (RR) CLL. With the median follow-up of 4.8 years, 49 (57.0%) of 86 patients remain on study. Treatment was discontinued for progressive disease in 20 (23.3%) patients and for adverse events in 5 (5.8%). Atrial fibrillation occurred in 18 (20.9%) patients for a rate of 6.4 per 100 patient-years. No serious bleeding occurred. The overall response rate at 6 months, the primary study endpoint, was 95.8% for the TP53 cohort (95% confidence interval, 85.7%-99.5%) and 93.9% for the elderly cohort (95% confidence interval, 79.8%-99.3%). Depth of response improved with time: at best response, 14 (29.2%) of 48 patients in the TP53 cohort and 9 (27.3%) of 33 in the elderly cohort achieved a complete response. Median minimal residual disease (MRD) in peripheral blood was 3.8 × 10 -2 at 4 years, with MRD-negative (<10 -4 ) remissions in 5 (10.2%) patients. In the TP53 cohort, the estimated 5-year progression-free survival (PFS) was 74.4% in TN-CLL compared with 19.4% in RR-CLL ( P = .0002), and overall survival (OS) was 85.3% vs 53.7%, respectively ( P = .023). In the elderly cohort, the estimated 5-year PFS and OS in RR-CLL were 64.8% and 71.6%, respectively, and no event occurred in TN-CLL. Long-term administration of ibrutinib was well tolerated and provided durable disease control for most patients. This trial was registered at www.clinicaltrials.gov as #NCT01500733., (© 2018 by The American Society of Hematology.)

Ligation of inhibitory receptors renders natural killer (NK) cells inactive against autologous tumors. Recently, the proteasome inhibitor bortezomib was shown to sensitize tumors to autologous NK-cell cytotoxicity in vitro. Here, we show bortezomib augments the antitumor effects of syngeneic NK-cell infusions in tumor-bearing animals; this effect is further enhanced in regulatory T cell (Treg cell)-depleted hosts. In vitro, bortezomib-treated tumors had higher tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and perforin/granzyme-mediated caspase-8 activity, which enhanced their susceptibility to NK-cell lysis. Bioluminescence imaging of mice with established tumors showed treatment with bortezomib and syngeneic NK cells reduced tumor growth and prolonged survival compared with controls receiving bortezomib or NK cells alone. In contrast, tumor progression was not delayed when animals received bortezomib and perforin-deficient NK cells, showing drug-induced augmentation in NK-cell cytotoxicity was mediated through perforin/granzyme. Furthermore, tumor growth was slower in bortezomib-treated recipients when host Treg cells were eradicated with anti-CD25 antibody before infusing NK cells compared with mice without Treg-cell ablation (tumor doubling time, 16.7 vs 4.9 days, respectively; P = .02). These findings suggest that depletion of Treg cells followed by bortezomib-induced tumor sensitization to autologous NK cells could be used as a novel strategy to treat cancer.

Primitive quiescent CD34(+) chronic myeloid leukemia (CML) cells are more biologically resistant to tyrosine kinase inhibitors than their cycling counterparts; however, graft-versus-leukemia (GVL) effects after allogeneic stem cell transplantation (SCT) probably eliminate even these quiescent cells in long-term surviving CML transplant recipients. We studied the progeny of CD34(+) cells from CML patients before SCT, which were cultured 4 days in serum-free media with hematopoietic growth factors. BCR-ABL expression was similar in both cycling and quiescent noncycling CD34(+) populations. Quiescent CD34(+) cells from CML patients were less susceptible than their cycling CD34(+) and CD34(-) counterparts to lysis by natural killer (NK) cells from their HLA-identical sibling donors. Compared with cycling populations, quiescent CD34(+) CML cells had higher surface expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors DR4 and DR5. Bortezomib up-regulated TRAIL receptor expression on quiescent CD34(+) CML cells, and further enhanced their susceptibility to cytotoxicity by in vitro expanded donor NK cells. These results suggest that donor-derived NK cell-mediated GVL effects may be improved by sensitizing residual quiescent CML cells to NK-cell cytotoxicity after SCT. Such treatment, as an adjunct to donor lymphocyte infusions and pharmacologic therapy, may reduce the risk of relapse in CML patients who require treatment by SCT.

Perforin is a cytolytic protein expressed mainly in activated cytotoxic lymphocytes and natural killer cells. Inherited perforin mutations account for 20% to 40% of familial hemophagocytic lymphohistiocytosis, a fatal disease of early childhood characterized by the absence of functional perforin. Aplastic anemia, the paradigm of immune-mediated bone marrow failure syndromes, is characterized by hematopoietic stem cell destruction by activated T cells and Th1 cytokines. We examined whether mutations in the perforin gene occurred in acquired aplastic anemia. Three nonsynonymous PRF1 mutations among 5 unrelated patients were observed. Four of 5 patients with the mutations showed some hemophagocytosis in the bone marrow at diagnosis. Perforin protein levels in these patients were very low or absent, and perforin granules were completely absent. Natural killer (NK) cell cytotoxicity from these patients was significantly decreased. Our data suggest that PRF1 genetic alterations help explain the aberrant proliferation and activation of cytotoxic T cells and may represent genetic risk factors for bone marrow failure.

We investigated if an infusion of alloreactive natural killer (NK) cells would reduce GVHD and mediate antitumor effects in mice undergoing MHC-matched allogeneic stem cell transplantation (SCT). Balb/c mice bearing RENCA tumors underwent an allogeneic SCT from MHC-matched B10.d2 donors and were given a single infusion of either Ly49 ligand-matched, ligand-mismatched, or no donor NK cells. Recipients of Ly49 ligand-mismatched NK cells had a reduced incidence of graft-versus-host disease (GVHD; 39% vs 100%; P < .01), and prolonged survival (median 84 days vs 39 days; P < .01) compared with SCT recipients not receiving NK cells. Recipients of Ly49 ligand-matched NK cells had the same incidence of GVHD and similar survival compared with controls not receiving NK cells. Pulmonary tumor burden was significantly (P < .01) lower in recipients that received Ly49-mismatched or Ly49-matched NK cells compared with recipients not receiving NK cells. These data provide in vivo evidence that a single infusion of alloreactive donor NK cells reduces GVHD and mediates antitumor effects following MHC-matched allogeneic transplantation.

Eighty patients with chronic myeloid leukemia (CML) underwent T cell-depleted stem cell transplantation from an HLA-identical sibling, with add-back of donor T cells on days 30 to 45 and days 60 to 100 in patients in whom grade 2 or greater acute graft-versus-host disease (GVHD) developed. The outcomes for 54 patients with chronic-phase (CP) and 26 with advanced-phase (AP) disease were as follows: overall survival, 85% +/- 5% versus 36% +/- 10%; transplantation-related mortality (TRM), 13% +/- 5% versus 43% +/- 11%; and current leukemia-free survival, 76% +/- 6% versus 34% +/- 9%. The day-30 lymphocyte count (LC30) was strongly associated with outcome. For patients in CP with counts greater than the median of 0.30 x 10(9)/L, survival was 100% versus 70% +/- 9% (P = .003); current LFS 100% versus 56% +/- 9% (P = .002); and TRM 0% versus 26% +/- 8% (P = .006). Higher-than-median LC30 correlated significantly with molecular remission (MR) at 3, 6, and 12 months and with higher CD34 doses. Lymphocyte subset analysis performed in 20 patients available for phenotyping showed that LC30 was highly correlated with absolute CD56+CD3- natural killer cell numbers (NK30), which also predicted for survival and MR. CD34 cell dose, LC30, and NK30, but not day-30 CD3+ cell count, were highly correlated and were significant predictors of transplantation outcome. These results suggest that transplanted CD34 cell doses greater than 5 x 10(6)/kg may improve outcomes by increasing the early recovery of NK cells.

We have selectively depleted host-reactive donor T cells from peripheral blood stem cell (PBSC) transplant allografts ex vivo using an anti-CD25 immunotoxin. We report a clinical trial to decrease graft-versus-host disease (GVHD) in elderly patients receiving selectively depleted PBSC transplants from HLA-identical sibling donors. Sixteen patients (median age, 65 years [range, 51-73 years]), with advanced hematologic malignancies underwent transplantation following reduced-intensity conditioning with fludarabine and either cyclophosphamide (n = 5), melphalan (n = 5), or busulfan (n = 6). Cyclosporine was used as sole GVHD prophylaxis. The allograft contained a median of 4.5 x 10(6) CD34 cells/kg (range, 3.4-7.3 x 10(6) CD34 cells/kg) and 1.0 x 10(8)/kg (range, 0.2-1.5 x 10(8)/kg) selectively depleted T cells. Fifteen patients achieved sustained engraftment. The helper T-lymphocyte precursor (HTLp) frequency assay demonstrated successful (mean, 5-fold) depletion of host-reactive donor T cells, with conservation of third-party response in 9 of 11 cases tested. Actuarial rates of acute GVHD were 46% +/- 13% for grades II to IV and 12% +/- 8% for grades III to IV. These results suggest that allodepletion of donor cells ex vivo is clinically feasible in older patients and may reduce the rate of severe acute GVHD. Further studies with selectively depleted transplants to evaluate graft-versus-leukemia (GVL) and survival are warranted.

Antigens implicated in the graft-versus-leukemia (GVL) effect in chronic myeloid leukemia (CML) include WT1, PR1, and BCR-ABL. To detect very low frequencies of these antigen-specific CD8+ T cells, we used quantitative polymerase chain reaction (qPCR) to measure interferon-gamma (IFN-gamma) mRNA production by peptide-pulsed CD8+ T cells from HLA-A*0201+ healthy volunteers and from patients with CML before and after allogeneic stem cell transplantation (SCT). Parallel assays using cytomegalovirus (CMV) pp65 tetramers demonstrated the IFN-gamma copy number to be linearly related to the frequency of tetramer-binding T cells, sensitive to frequencies of 1 responding CD8+ T cell/100 000 CD8+ T cells. Responses to WT1 and PR1 but not BCR-ABL were detected in 10 of 18 healthy donors. Responses to WT1, PR1, or BCR-ABL were observed in 9 of 14 patients with CML before SCT and 5 of 6 after SCT, often to multiple epitopes. Responses were higher in patients with CML compared with healthy donors and highest after SCT. These antigen-specific CD8+ T cells comprised central memory (CD45RO+CD27+CD57-) and effector memory (CD45RO-CD27-CD57+) T cells. In conclusion, leukemia-reactive CD8+ T cells derive from memory T cells and occur at low frequencies in healthy individuals and at higher frequencies in patients with CML. The increased response in patients after SCT suggests a quantitative explanation for the greater effect of allogeneic SCT.

To assess the safety and efficacy of nonmyeloablative allogeneic transplantation in patients with HIV infection, a clinical protocol was initiated in patients with refractory hematologic malignancies and concomitant HIV infection. The results from the first 2 patients are reported. The indications for transplantation were treatment-related acute myelogenous leukemia and primary refractory Hodgkin disease in patients 1 and 2, respectively. Only patient 1 received genetically modified cells. Both patients tolerated the procedure well with minimal toxicity, and complete remissions were achieved in both patients, but patient 2 died of relapsed Hodgkin disease 12 months after transplantation. Patient 1 continues in complete remission with undetectable HIV levels and rising CD4 counts, and with both the therapeutic and control gene transfer vectors remaining detectable at low levels more than 2 years after transplantation. These results suggest that nonmyeloablative allogeneic transplantation in the context of highly active antiretroviral therapy is feasible in patients with treatment-sensitive HIV infection.

Delayed donor red cell engraftment and pure red cell aplasia (PRCA) are well-recognized complications of major ABO-incompatible hematopoietic stem cell transplantation (SCT) performed by means of myeloablative conditioning. To evaluate these events following reduced-intensity nonmyeloablative SCT (NST), consecutive series of patients with major ABO incompatibility undergoing either NST (fludarabine/cyclophosphamide conditioning) or myeloablative SCT (cyclophosphamide/high-dose total body irradiation) were compared. Donor red blood cell (RBC) chimerism (initial detection of donor RBCs in peripheral blood) was markedly delayed following NST versus myeloablative SCT (median, 114 versus 40 days; P <.0001) and strongly correlated with decreasing host antidonor isohemagglutinin levels. Antidonor isohemagglutinins declined to clinically insignificant levels more slowly following NST than myeloablative SCT (median, 83 versus 44 days; P =.03). Donor RBC chimerism was delayed more than 100 days in 9 of 14 (64%) and PRCA occurred in 4 of 14 (29%) patients following NST, while neither event occurred in 12 patients following myeloablative SCT. Conversion to full donor myeloid chimerism following NST occurred significantly sooner in cases with, compared with cases without, PRCA (30 versus 98 days; P =.008). Cyclosporine withdrawal appeared to induce graft-mediated immune effects against recipient isohemagglutinin-producing cells, resulting in decreased antidonor isohemagglutinin levels and resolution of PRCA following NST. These data indicate that significantly delayed donor erythropoiesis is (1) common following major ABO-incompatible NST and (2) associated with prolonged persistence of host antidonor isohemagglutinins. The clinical manifestations of these events are affected by the degree and duration of residual host hematopoiesis.