Emerging therapies in hematopoietic stem cell transplantation

A pharmacodynamic assay to monitor treatment with the hypomethylating cytosine analogs, decitabine and azacitidine

Hypomethylating therapies using decitabine or azacitidine are actively investigated to treat acute myeloid leukemia, myelodysplastic syndromes, as maintenance therapy after allogenic stem cell transplant and hemoglobinopathies. The therapeutic mechanism is to de-repress genes that have been turned off through oncogenesis or development via methylation. The therapy can be non-cytotoxic at low dosage, sparing healthy stem cells and operating on committed precursors. Because the methods of determining maximum tolerated dose are not well suited to this paradigm, and because the mechanism of action, which is depletion of DNA methylase 1 (DNMT1), is complex and dependent on passing through a cell cycle, a pharmacodynamic assay that measures DNMT1 can inform clinical trials aimed at establishing and improving therapy. Herein, we provide an assay that measures DNMT1 relative levels in circulating T cells of peripheral blood.

Reprint of: Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

Epigenetic therapy in allogeneic hematopoietic stem cell transplantation

DNA methylation and other epigenetic phenomena appear to be relevant in the pathogenesis of several malignant disorders. DNA methyltransferases add methyl groups to cytosine-phosphate-guanine (CpG) islandsleading to gene promoter silencing. The DNA methyltransferases inhibitors azacitidine and decitabine have anti-tumor activity against a broad range of malignancies, but have been investigated mostly in myelodysplastic syndrome. In addition, these agents have immunomodulatory effects that are under investigation in the allogeneic stem cell transplantation scenario. Both drugs have been used in the perioperative period of allogeneic transplantations with varying degrees of success. It has been hypothesized that low dose azacitidine may increase the graft-versus-leukemia effect and have a role in the maintenance of remission after allogeneic transplantation for myeloid leukemias. It is also intriguing that this favorable effect might occur while mitigating graft-versus-host disease. Here we present a review of the rapidly growing field of epigenetic manipulation using hypomethylating agents in allogeneic transplantation.

Primary treatment of leukemia relapses after allogeneic hematopoietic stem cell transplantation with reduced-intensity conditioning second transplantation from the original donor

Acute leukemia relapsing after allogeneic hematopoietic stem cell transplantation (HSCT) has dismal outcome. Consecutive consenting patients (acute myeloid leukemia: N = 71; acute lymphoblastic leukemia: N = 37), at a median age of 37 (16-57) years, who had relapsed 7.9 (1.3-132) months post-HSCT, were treated with three cytarabine-based intensive regimens as reduced-intensity conditioning (RIC), followed by infusion of mobilized HSC from the original donors. There were four treatment-related mortalities (TRMs). Of 104 evaluable cases, 72 patients (67%) achieved complete remission (CR)/CR with incomplete hematologic recovery (CRi). The median overall survival (OS) of the entire cohort was 11.6 months. The OS of patients achieving CR/CRi after the first RIC/HSCT was 18.8 months, as compared with 3.9 months for those not (P < 0.01). For 32 patients with nonremission, 11 received a repeat RIC-HSCT, leading to CR/CRi in three cases. Therefore, 75/108 (69%) of patients achieved CR/CRi after one or two courses of RIC-HSCT. Among CR/CRi patients, 48 cases relapsed again after 6.1 (1.0-64.4) months. Thirty cases received a repeat RIC-HSCT, leading to CR/CRi in 22 patients. Multivariate analyses showed a significant impact of remission duration after initial HSCT (P = 0.026) and the presence of acute graft-versus-host disease after RIC-HSCT (P = 0.011) on CR/CRi. RIC-HSCT as primary treatment for acute leukemic relapses post-HSCT induced a high CR rate with low TRM. Optimal postremission treatment remains to be defined.