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Patients with primary central nervous system lymphoma (PCNSL) are treated with high-dose methotrexate-based chemotherapy, which requires hospitalization and extensive expertise to manage related toxicity. The use of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) could overcome these difficulties, but blood-brain barrier (BBB) penetration of related drugs is poor. Tumor necrosis factor-α coupled with NGR (NGR-hTNF), a peptide targeting CD13 + vessels, induces endothelial permeabilization and improves tumor access of cytostatics. We tested the hypothesis that NGR-hTNF can break the BBB, thereby improving penetration and activity of R-CHOP in patients with relapsed/refractory PCNSL (NCT03536039). Patients received six R-CHOP21 courses, alone at the first course and preceded by NGR-hTNF (0.8 μg/m 2 ) afterward. This trial included 2 phases: an "explorative phase" addressing the effect of NGR-hTNF on drug pharmacokinetic parameters and on vessel permeability, assessed by dynamic contrast-enhanced magnetic resonance imaging and 99m Tc-diethylene-triamine-pentacetic acid-single-photon emission computed tomography, and the expression of CD13 on tumor tissue; and an "expansion phase" with overall response rate as the primary end point, in which the 2-stage Simon Minimax design was used. At the first stage, if ≥4 responses were observed among 12 patients, the study accrual would have continued (sample size, 28). Herein, we report results of the explorative phase and the first-stage analysis (n = 12). CD13 was expressed in tumor vessels of all cases. NGR-hTNF selectively increased vascular permeability in tumoral/peritumoral areas, without interfering with drug plasma/cerebrospinal fluid concentrations. The NGR-hTNF/R-CHOP combination was well tolerated: there were only 2 serious adverse events, and grade 4 toxicity was almost exclusively hematological, which were resolved without dose reductions or interruptions. NGR-hTNF/R-CHOP was active, with 9 confirmed responses (75%; 95% confidence interval, 51-99), 8 of which were complete. In conclusion, NGR-hTNF/R-CHOP was safe in these heavily pretreated patients. NGR-hTNF enhanced vascular permeability specifically in tumoral/peritumoral areas, which resulted in fast and sustained responses., (© 2019 by The American Society of Hematology.)

Memory stem T cells (TSCM) have been proposed as key determinants of immunologic memory. However, their exact contribution to a mounting immune response, as well as the mechanisms and timing of their in vivo generation, are poorly understood. We longitudinally tracked TSCM dynamics in patients undergoing haploidentical hematopoietic stem cell transplantation (HSCT), thereby providing novel hints on the contribution of this subset to posttransplant immune reconstitution in humans. We found that donor-derived TSCM are highly enriched early after HSCT. We showed at the antigen-specific and clonal level that TSCM lymphocytes can differentiate directly from naive precursors infused within the graft and that the extent of TSCM generation might correlate with interleukin 7 serum levels. In vivo fate mapping through T-cell receptor sequencing allowed defining the in vivo differentiation landscapes of human naive T cells, supporting the notion that progenies of single naive cells embrace disparate fates in vivo and highlighting TSCM as relevant novel players in the diversification of immunological memory after allogeneic HSCT., (© 2015 by The American Society of Hematology.)

Genetically targeted T cells promise to solve the feasibility and efficacy hurdles of adoptive T-cell therapy for cancer. Selecting a target expressed in multiple-tumor types and that is required for tumor growth would widen disease indications and prevent immune escape caused by the emergence of antigen-loss variants. The adhesive receptor CD44 is broadly expressed in hematologic and epithelial tumors, where it contributes to the cancer stem/initiating phenotype. In this study, silencing of its isoform variant 6 (CD44v6) prevented engraftment of human acute myeloid leukemia (AML) and multiple myeloma (MM) cells in immunocompromised mice. Accordingly, T cells targeted to CD44v6 by means of a chimeric antigen receptor containing a CD28 signaling domain mediated potent antitumor effects against primary AML and MM while sparing normal hematopoietic stem cells and CD44v6-expressing keratinocytes. Importantly, in vitro activation with CD3/CD28 beads and interleukin (IL)-7/IL-15 was required for antitumor efficacy in vivo. Finally, coexpressing a suicide gene enabled fast and efficient pharmacologic ablation of CD44v6-targeted T cells and complete rescue from hyperacute xenogeneic graft-versus-host disease modeling early and generalized toxicity. These results warrant the clinical investigation of suicidal CD44v6-targeted T cells in AML and MM.

Long-living memory stem T cells (T(SCM)) with the ability to self-renew and the plasticity to differentiate into potent effectors could be valuable weapons in adoptive T-cell therapy against cancer. Nonetheless, procedures to specifically target this T-cell population remain elusive. Here, we show that it is possible to differentiate in vitro, expand, and gene modify in clinically compliant conditions CD8(+) T(SCM) lymphocytes starting from naive precursors. Requirements for the generation of this T-cell subset, described as CD62L(+)CCR7(+)CD45RA(+)CD45R0(+)IL-7Rα(+)CD95(+), are CD3/CD28 engagement and culture with IL-7 and IL-15. Accordingly, T(SCM) accumulates early after hematopoietic stem cell transplantation. The gene expression signature and functional phenotype define this population as a distinct memory T-lymphocyte subset, intermediate between naive and central memory cells. When transplanted in immunodeficient mice, gene-modified naive-derived T(SCM) prove superior to other memory lymphocytes for the ability to expand and differentiate into effectors able to mediate a potent xenogeneic GVHD. Furthermore, gene-modified T(SCM) are the only T-cell subset able to expand and mediate GVHD on serial transplantation, suggesting self-renewal capacity in a clinically relevant setting. These findings provide novel insights into the origin and requirements for T(SCM) generation and pave the way for their clinical rapid exploitation in adoptive cell therapy.

The genetic modification of T cells with a suicide gene grants a mechanism of control of adverse reactions, allowing safe infusion after partially incompatible hematopoietic stem cell transplantation (HSCT). In the TK007 clinical trial, 22 adults with hematologic malignancies experienced a rapid and sustained immune recovery after T cell-depleted HSCT and serial infusions of purified donor T cells expressing the HSV thymidine kinase suicide gene (TK+ cells). After a first wave of circulating TK+ cells, the majority of T cells supporting long-term immune reconstitution did not carry the suicide gene and displayed high numbers of naive lymphocytes, suggesting the thymus-dependent development of T cells, occurring only upon TK+ -cell engraftment. Accordingly, after the infusions, we documented an increase in circulating TCR excision circles and CD31+ recent thymic emigrants and a substantial expansion of the active thymic tissue as shown by chest tomography scans. Interestingly, a peak in the serum level of IL-7 was observed after each infusion of TK+ cells, anticipating the appearance of newly generated T cells. The results of the present study show that the infusion of genetically modified donor T cells after HSCT can drive the recovery of thymic activity in adults, leading to immune reconstitution.

In allogeneic hematopoietic cell transplantation (HSCT), donor T lymphocytes mediate the graft-versus-leukemia (GVL) effect, but induce graft-versus-host disease (GVHD). Suicide gene therapy-that is, the genetic induction of a conditional suicide phenotype into donor T cells-allows dissociating the GVL effect from GVHD. Genetic modification with retroviral vectors after CD3 activation reduces T-cell alloreactivity. We recently found that alloreactivity is maintained when CD28 costimulation, IL-7, and IL-15 are added. Herein, we used the minor histocompatibility (mH) antigens HA-1 and H-Y as model alloantigens to directly explore the antileukemia efficacy of human T cells modified with the prototypic suicide gene herpes simplex virus thymidine kinase (tk) after activation with different stimuli. Only in the case of CD28 costimulation, IL-7, and IL-15, the repertoire of tk(+) T cells contained HA-1- and H-Y-specific CD8(+) cytotoxic T cells (CTL) precursors. Thymidine kinase-positive HA-1- and H-Y-specific CTLs were capable of self-renewal and differentiation into potent antileukemia effectors in vitro, and in vivo in a humanized mouse model. Self-renewal and differentiation coincided with IL-7 receptor expression. These results pave the way to the clinical investigation of T cells modified with a suicide gene after CD28 costimulation, IL-7, and IL-15 for a safe and effective GVL effect.

Dendritic cell (DC) targeting in vivo has recently been shown to confer strong and protective cytotoxic T lymphocyte (CTL)-based immunity in tumor murine models. Our group has recently demonstrated in preclinical models that the infusion of genetically modified lymphocytes (GMLs) expressing the self/tumor antigen TRP-2 is able to elicit functional TRP-2-specific effectors with antitumor activity by targeting DCs in vivo. Here we have analyzed vaccine- and tumor-specific immune responses of 10 melanoma patients treated with autologous GMLs expressing the cancer germline gene MAGE-A3. Three of 10 patients treated with MAGE-A3-GML showed an increase of circulating anti-MAGE-A3 T cells, and developed skin delayed-type hypersensitivity to MAGE-A3. Interestingly, in 2 of these patients, with progressive and measurable tumors at study entry, anti-MAGE-A3 T cells were detected not only in the blood but also within tumors resected after vaccination. These results demonstrate that the infusion of MAGE-A3-GML elicits antitumor T cells, which are capable of trafficking to inflamed tissues and of infiltrating tumors. Clinical studies on a larger group of patients are needed to evaluate the clinical efficacy of such a strategy.

Long-term clinical remissions of leukemia, after allogeneic hematopoietic stem cell transplantation, depend on alloreactive memory T cells able to self-renew and differentiate into antileukemia effectors. This is counterbalanced by detrimental graft-versus-host disease (GVHD). Induction of a selective suicide in donor T cells is a current gene therapy approach to abrogate GVHD. Unfortunately, genetic modification reduces alloreactivity of lymphocytes. This associates with an effector memory (T(EM)) phenotype of gene-modified lymphocytes and may limit antileukemia effect. We hypothesized that alloreactivity of gene-modified lymphocytes segregates with the central memory (T(CM)) phenotype. To this, we generated suicide gene-modified T(CM) lymphocytes with a retroviral vector after CD28 costimulation and culture with IL-2, IL-7, or a combination of IL-7 and IL-15. In vitro, suicide gene-modified T(CM) cells self-renewed upon alloantigen stimulation and resisted activation-induced cell death. In a humanized mouse model, only suicide gene-modified T cells cultured with IL-7 and IL-15 persisted, differentiated in T(EM) cells, and were as potent as unmanipulated lymphocytes in causing GVHD. GVHD was halted through the activation of the suicide gene machinery. These results warrant the use of suicide gene-modified T(CM) cells cultured with IL-7 and IL-15 for the safe exploitation of the alloreactive response against cancer.

In this study, we have characterized reconstitution of the natural killer (NK) cell repertoire after haploidentical CD34(+) selected hematopoietic stem cell transplantation (HSCT) for high-risk hematologic malignancies. Analysis focused on alloreactive single-KIR(+) NK cells, which reportedly are potent antileukemic effectors. One month after HSCT, CD56(bright)/CD56(dim) NK-cell subsets showed inverted ratio and phenotypic features. CD25 and CD117 down-regulation on CD56(bright), and NKG2A and CD62L up-regulation on CD56(dim), suggest sequential CD56(bright)-to-CD56(dim) NK-cell maturation in vivo. Consistently, the functional potential of these maturation intermediates against leukemic blasts was impaired. Mature receptor repertoire reconstitution took at least 3 months. Importantly, at this time point, supposedly alloreactive, single-KIR(+) NK cells were not yet fully functional. Frequency of these cells was highly variable, independently from predicted NK alloreactivity, and below 1% of NK cells in 3 of 6 alloreactive patients studied. In line with these observations, no clinical benefit of predicted NK alloreactivity was observed in the total cohort of 56 patients. Our findings unravel the kinetics, and limits, of NK-cell differentiation from purified haploidentical hematopoietic stem cells in vivo, and suggest that NK-cell antileukemic potential could be best exploited by infusion of mature single-KIR(+) NK cells selected from an alloreactive donor.

Mutations in the adenosine deaminase (ADA) gene are responsible for a form of severe combined immunodeficiency (SCID) caused by the lymphotoxic accumulation of ADA substrates, adenosine and 2'-deoxy-adenosine. The molecular mechanisms underlying T-cell dysfunction in humans remain to be elucidated. Here, we show that CD4(+) T cells from ADA-SCID patients have severely compromised TCR/CD28-driven proliferation and cytokine production, both at the transcriptional and protein levels. Such an impairment is associated with an intrinsically reduced ZAP-70 phosphorylation, Ca(2+) flux, and ERK1/2 signaling and to defective transcriptional events linked to CREB and NF-kappaB. Moreover, exposure to 2'-deoxy-adenosine results in a stronger inhibition of T-cell activation, mediated by the aberrant A(2A) adenosine receptor signaling engagement and PKA hyperactivation, or in a direct apoptotic effect at higher doses. Conversely, in T cells isolated from patients after gene therapy with retrovirally transduced hematopoietic stem/progenitor cells, the biochemical events after TCR triggering occur properly, leading to restored effector functions and normal sensitivity to apoptosis. Overall, our findings provide a better understanding of the pathogenesis of the immune defects associated with an altered purine metabolism and confirm that ADA gene transfer is an efficacious treatment for ADA-SCID. The trials in this study are enrolled at www.ClinicalTrials.gov as #NCT00598481 and #NCT0059978.

Gene therapy is a promising therapeutic strategy for genetic and acquired hematologic diseases. With the improvements in gene transfer and expression, factors affecting safety and efficacy of gene therapy can now be evaluated to establish the best clinical benefit-to-risk ratio. The induction of immune responses against gene therapy components is one of the potential limitations. We studied the occurrence of such event in 23 patients treated with donor lymphocyte infusions (DLIs), with lymphocytes transduced to express the HSV-TK suicide gene for relapse of hematologic malignancies occurring after allogeneic hematopoietic stem cell transplantation (HSCT). The suicide gene was used to selectively control graft-versus-host disease (GvHD). Seven patients given infusions late after HSCT developed an immune response against the transgene. Immunization involved appearance of thymidine kinase (TK)-specific CD8(+) effectors and required a level of immunocompetence at the time of TK-DLI that can be achieved only several months after transplantation. This did not prevent graft-versus-leukemia (GvL) effect of the TK-DLI, since 5 of 7 immunized patients maintained the complete remission achieved prior to immunization. We suggest that appropriate study designs taking into account the immune suppression of the patient and time-kinetics of GvL mediated by TK-transduced donor lymphocytes may allow the full exploitation of TK-DLI.

The extensive exploitation of the antitumor effect of donor lymphocytes infused after allogeneic hematopoietic stem-cell transplantation (allo-HSCT) is limited by the risk of graft-versus-host disease (GvHD). To overcome this limitation, we investigated the therapeutic potential of donor lymphocytes engineered with the suicide gene thymidine kinase of herpes simplex virus (TK) in 23 patients experiencing recurrence of hematologic malignancies after allo-HSCT. Long-term follow-up of infused patients included analysis of engraftment of genetically engineered lymphocytes, in vivo assessment of antitumor effect, and control of GvHD by ganciclovir. All 17 patients evaluable for engraftment and graft-versus-leukemia (GvL) had circulating TK(+) cells detectable beginning at a median time of 18 days. Eleven patients (65%) experienced a substantial clinical benefit resulting in 6 (35%) complete remissions and 5 (29%) partial responses. The antitumor effect tightly correlated with the in vivo expansion of TK(+) cells. Seven patients received ganciclovir, resulting in elimination of TK(+) cells and effective and selective treatment of GvHD. Immunization against HSV-TK was observed in 7 patients but did not preclude an effective GvL. These data validate the feasibility, safety, and efficacy of TK(+) cells in the context of allografting and represent the basis for a broader application of this technology.

In an effort to develop an encapsulated cell-based system to deliver arylsulfatase A (ARSA) to the central nervous system of metachromatic leukodystrophy (MLD) patients, we engineered C2C12 mouse myoblasts with a retroviral vector containing a full-length human ARSA cDNA and evaluated the efficacy of the recombinant secreted enzyme to revert the MLD phenotype in oligodendrocytes (OL) of the As2-/- mouse model. After transduction, C2C12 cells showed a fifteen-fold increase in intracellular ARSA activity and five-fold increase in ARSA secretion. The secreted hARSA collected from transduced cells encapsulated in polyether-sulfone polymer, was taken up by enzyme-deficient OL derived from MLD mice and normally sorted to the lysosomal compartment, where transferred enzyme reached 80% of physiological levels, restoring the metabolism of sulfatide. To evaluate whether secreted enzyme could restore metabolic function in the brain, encapsulated cells and secreted ARSA were shown to be stable in CSF in vitro. Further, to test cell viability and enzyme release in vivo, encapsulated cells were implanted subcutaneously on the dorsal flank of DBA/2J mice. One month later, all retrieved implants released hARSA at rates similar to unencapsulated cells and contained well preserved myoblasts, demonstrating that encapsulation maintains differentiation of C2C12 cells, stable transgene expression and long-term cell viability in vivo. Thus, these results show the promising potential of developing an ARSA delivery system to the CNS based on the use of a polymer-encapsulated transduced xenogenic cell line for gene therapy of MLD.

Adenosine deaminase (ADA) deficiency is caused by a purine metabolic dysfunction, leading to severe combined immunodeficiency (SCID) and multiple organ damage. To investigate the efficacy of ex vivo gene therapy with self-inactivating lentiviral vectors (LVs) in correcting this complex phenotype, we used an ADA(-/-) mouse model characterized by early postnatal lethality. LV-mediated ADA gene transfer into bone marrow cells combined with low-dose irradiation rescued mice from lethality and restored their growth, as did transplantation of wild-type bone marrow. Mixed chimerism with multilineage engraftment of transduced cells was detected in the long term in animals that underwent transplantation. ADA activity was normalized in lymphocytes and partially corrected in red blood cells (RBCs), resulting in full metabolic detoxification and prevention of severe pulmonary insufficiency. Moreover, gene therapy restored normal lymphoid differentiation and immune functions, including antigen-specific antibody production. Similar degrees of detoxification and immune reconstitution were obtained in mice treated early after birth or after 1 month of enzyme-replacement therapy, mimicking 2 potential applications for ADA-SCID. Overall, this study demonstrates the efficacy of LV gene transfer in correcting both the immunological and metabolic phenotypes of ADA-SCID and supports the future clinical use of this approach.

In allogeneic hematopoietic cell transplantation (allo-HCT), the immune recognition of host antigens by donor T lymphocytes leads to a beneficial graft-versus-leukemia (GvL) effect as well as to life-threatening graft-versus-host disease (GvHD). Genetic modification of T lymphocytes with a retroviral vector (RV) expressing the herpes simplex virus-thymidine kinase (TK) suicide gene confers selective sensitivity to the prodrug ganciclovir (GCV). In patients, the infusion of TK+ lymphocytes and the subsequent administration of GCV resulted in a time-wise modulation of antihost reactivity for a GvL effect, while controlling GvHD. Because activation required for genetic modification with RV may reduce antihost reactivity, we investigated the requirements for maximizing the potency of human TK+ lymphocytes. Whereas T-cell receptor triggering alone led to effector memory (EM) TK+ lymphocytes, the addition of CD28 costimulation through cell-sized beads resulted in the generation of central memory (CM) TK+ lymphocytes. In a quantitative model for GvHD using nonobese diabetic/severely combined immunodeficient mice, CM TK+ lymphocytes were more potent than EM TK+ lymphocytes. GCV administration efficiently controlled GvHD induced by CM TK+ lymphocytes. These results warrant the clinical investigation of CM suicide gene-modified human T lymphocytes for safe and effective allo-HCT.

The importance of HLA-DPB1 matching for the outcome of allogeneic hematologic stem cell (HSC) transplantation is controversial. We have previously identified HLA-DPB1*0901 as a target of cytotoxic T cells mediating in vivo rejection of an HSC allograft. Here we show that HLA-DPB1*0901 encodes a T-cell epitope shared by a subset of DPB1 alleles that determines nonpermissive mismatches for HSC transplantation. Several T-cell clones obtained from the patient at the time of rejection showed HLA-DP restricted recognition of allogeneic targets expressing HLA-DPB1*0901, *1001, *1701, *0301, *1401, and *4501, but not other alleles. Based on these findings, we developed an algorithm for prediction of nonpermissive HLA-DPB1 mismatches. Retrospective evaluation of 118 transplantations showed that the presence of nonpermissive HLA-DPB1 mismatches was correlated with significantly increased hazards of acute grade II to IV graft-versus-host disease (HR = 1.87, P =.046) and transplantation-related mortality (HR = 2.69, P =.027) but not relapse (HR = 0.98, P =.939), as compared with the permissive group. There was also a marked but statistically not significant increase in the hazards of overall mortality (HR = 1.64, P =.1). These data suggest that biologic characterization of in vivo alloreactivity can be a tool for definition of clinically relevant nonpermissive HLA mismatches for unrelated HSC transplantation.

Gene transfer into T lymphocytes is currently being tested for the treatment of lymphohematologic disorders. We previously showed that suicide gene transfer into donor lymphocytes infused to treat leukemic relapse after allogeneic hematopoietic stem cell transplantation allowed control of graft-versus-host disease. However, the T-cell receptor (TCR) activation and sustained proliferation required for retroviral vector transduction may impair the half-life and immune competence of transduced cells and reduce graft-versus-leukemia activity. Thus, we tested lentiviral vectors (LVs) and stimulation with cytokines involved in antigen-independent T-cell homeostasis, such as interleukin 7 (IL-7), IL-2, and IL-15. Late-generation LVs transduced efficiently nonproliferating T cells that had progressed from G0 to the G1 phase of the cell cycle on cytokine treatment. Importantly, IL-2 and IL-7, but not IL-15, stimulation preserved physiologic CD4/CD8 and naive-memory ratios in transduced cells with only minor induction of some activation markers. Functional analysis of immune response to cytomegalovirus (CMV) showed that, although CMV-specific T cells were preserved by all conditions of transduction, proliferation and specific killing of autologous cells presenting a CMV epitope were higher for IL-2 and IL-7 than for IL-15. Thus, LV transduction of IL-2 or IL-7 prestimulated cells overcomes the limitations of retroviral vectors and may significantly improve the efficacy of T-cell-based gene therapy.

We have previously shown that the infusion of donor lymphocytes expressing the herpes simplex virus thymidine kinase (HSV-tk) gene is an efficient tool for controlling graft-versus-host disease (GVHD) while preserving the graft-versus-leukemia (GVL) effect. In addition to the GVL effect, the administration of donor HSV-tk(+) cells could have a clinical impact in promoting immune reconstitution after T-cell-depleted stem cell transplantation (SCT). To explore this hypothesis, we have investigated whether in vitro polyclonal activation, retroviral transduction, immunoselection, and expansion affect the immune competence of donor T cells. We have observed that, after appropriate in vitro manipulation, T cells specific for antigens relevant in the context of SCT are preserved in terms of frequency, expression of T-cell receptor, proliferation, cytokine secretion, and lytic activity. A reduction in the frequency of allospecific T-cell precursors is observed after prolonged T-cell culture, suggesting that cell manipulation protocols involving a short culture time and high transduction efficiency are needed. Finally, the long-term persistence of HSV-tk(+) cells was observed in a patient treated in the GVL clinical trial, and a reversion of the phenotype of HSV-tk(+) cells from CD45RO(+) to CD45RA(+) was documented more than 2 years after the infusion. Based on all this evidence, we propose a clinical study of preemptive infusions of donor HSV-tk(+) T cells after SCT from haploidentical donors to provide early immune reconstitution against infection and potential immune protection against disease recurrence.

The feasibility and toxicity of allogeneic stem cell transplantation after nonmyeloablative conditioning including thiotepa, fludarabine, and cyclophosphamide have been investigated in 6 patients with breast cancer and 7 patients with renal cell cancer. The program included the use of escalating doses of donor lymphocyte infusions (DLI) and/or interferon alpha (IFNalpha) for patients showing no tumor response and no graft-versus-host disease (GVHD). Patients were at high risk of transplant-related mortality (TRM) because of age, advanced stage, and previous treatments. We observed a partial remission in 4 renal cancer and in 2 breast cancer patients (one at the molecular level in the bone marrow), occurring after cyclosporine withdrawal or after DLI and/or IFNalpha. All the responses were accompanied by the occurrence of acute GVHD. We conclude that reduced-intensity allogeneic stem cell transplantation is a feasible procedure in renal and breast cancer, and that the exploitation of graft-versus-tumor effect after DLI is a promising finding.

A reduced-intensity conditioning regimen was investigated in 45 patients with hematologic malignancies who were considered poor candidates for conventional myeloablative regimens. Median patient age was 49 years. Twenty-six patients previously failed autologous transplantation, and 18 patients had a refractory disease at the time of transplantation. In order to decrease nonrelapse mortality, and enhance the graft-versus-tumor effect, a program was designed in which a reduced conditioning with thiotepa, fludarabine, and cyclophosphamide was associated with programmed reinfusions of donor lymphocytes for patients without graft-versus-host disease (GVHD), not achieving clinical and molecular remission after transplantation. GVHD prophylaxis consisted of cyclosporine A and methotrexate. Seventeen patients received marrow cells and 28 received mobilized hematopoietic cells. All patients engrafted. The probability of grades II-IV and III-IV acute GVHD were 47% and 13%, respectively. The probability of nonrelapse mortality, progression-free survival, and overall survival were 13%, 57%, and 53%, respectively. Thirteen patients in complete remission had a polymerase chain reaction marker for minimal disease monitoring; 10 achieved molecular remission after transplantation. Nine patients received donor lymphocytes: one patient with mantle cell lymphoma had a minimal response, one patient with refractory anemia with excess of blasts in transformation achieved complete remission, and 7 patients did not respond. At a median follow-up of 385 days (range, 24 to 820 days), 25 patients (55%) were alive in complete remission. Although longer follow-up is needed to evaluate the long-term outcome, the study shows that this regimen is associated with a durable engraftment, has a low nonrelapse mortality rate, and can induce clinical and molecular remissions.