Isocitrate dehydrogenase mutations in myeloid malignancies.

Alterations to genes involved in cellular metabolism and epigenetic regulation are implicated in the pathogenesis of myeloid malignancies. Recurring mutations in isocitrate dehydrogenase (IDH) genes are detected in approximately 20% of adult patients with acute myeloid leukemia (AML) and 5% of adults with myelodysplastic syndromes (MDS). IDH proteins are homodimeric enzymes involved in diverse cellular processes, including adaptation to hypoxia, histone demethylation and DNA modification. The IDH2 protein is localized in the mitochondria and is a critical component of the tricarboxylic acid (also called the 'citric acid' or Krebs) cycle. Both IDH2 and IDH1 (localized in the cytoplasm) proteins catalyze the oxidative decarboxylation of isocitrate to α-ketoglutarate (α-KG). Mutant IDH enzymes have neomorphic activity and catalyze reduction of α-KG to the (R) enantiomer of 2-hydroxyglutarate, which is associated with DNA and histone hypermethylation, altered gene expression and blocked differentiation of hematopoietic progenitor cells. The prognostic significance of mutant IDH (mIDH) is controversial but appears to be influenced by co-mutational status and the specific location of the mutation (IDH1-R132, IDH2-R140, IDH2-R172). Treatments specifically or indirectly targeted to mIDH are currently under clinical investigation; these therapies have been generally well tolerated and, when used as single agents, have shown promise for inducing responses in some mIDH patients when used as first-line treatment or in relapsed or refractory AML or MDS. Use of mIDH inhibitors in combination with drugs with non-overlapping mechanisms of action is especially promising, as such regimens may address the clonal heterogeneity and the multifactorial pathogenic processes involved in mIDH myeloid malignancies. Advances in mutational analysis have made testing more rapid and convenient, and less expensive; such testing should become part of routine diagnostic workup and repeated at relapse to identify patients who may benefit from treatments that target mIDH.

Chronic graft versus host disease burden and late transplant complications are lower following adult double cord blood versus matched unrelated donor peripheral blood transplantation.

Adult umbilical cord blood transplantation (CBT) has emerged as an important option for patients lacking matched related (MRD) and matched unrelated donors (MUD). We compared chronic GVHD (cGVHD) incidence, immunosuppression burden and late infections and hospitalizations in consecutive patients undergoing CBT (n=51) versus peripheral blood MUD transplant (n=57) at our center between June 2009 and April 2014. At 3 years post transplantation, the cumulative incidence (CI) of moderate to severe cGVHD was 44% following MUD versus 8% following CBT (P=0.0006) and CI of any cGVHD was 68% following MUD versus 32% following CBT (P=0.0017). Median time to being off immunosuppression among CB patients was 268 days versus not reached among MUD patients (P<0.0001). Late infections and late hospitalized days were reduced in CB patients (P=0.1 and <0.001, respectively). Three-year CI of transplant-related mortality (TRM) and relapse as well as 3-year overall survival (OS) were similar following CB and MUD transplantation. We demonstrate a significantly lower incidence of cGVHD, immunosuppression burden and late complication rate following UCB versus peripheral blood MUD transplant without decreased OS, increased relapse or early TRM. Combined with the rapid availability of UCB, these findings have led our center to move primarily to UCB over peripheral blood MUD when a MRD is not available.

Omacetaxine mepesuccinate for the treatment of chronic myeloid leukemia.

Omacetaxine mepesuccinate is a protein synthesis inhibitor that causes apoptosis of chronic myeloid leukemia cells without binding to the BCR-ABL tyrosine kinase that is implicated in the pathogenesis of this disease. It has been approved for the treatment of chronic myeloid leukemia in patients with resistance to two or more tyrosine kinase inhibitors and is emerging as an important agent in countering the highly resistant T315I mutation. This review will focus on the preclinical pharmacology, pharmacokinetics and clinical utility of omacetaxine mepesuccinate in the current milieu of tyrosine kinase inhibitor-dominant therapy of chronic myeloid leukemia.

Ponatinib for the treatment of chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia.

Ponatinib is a novel, next-generation, small-molecule tyrosine kinase inhibitor with potent activity against the BCR-ABL fusion oncogene as well as all other ABL kinase domain mutations that confer resistance to earlier generation tyrosine kinase inhibitors. Due to its unique structure, it is the only tyrosine kinase inhibitor with the capability to counter the highly resistant T315I or gate-keeper mutation in leukemic cells that express the Philadelphia chromosome. This review will focus on the preclinical pharmacology, pharmacokinetics and clinical utility of ponatinib in the treatment of chronic myeloid leukemia and Philadelphia chromosome-positive adult acute lymphoblastic leukemia.

Adjusting DLCO for Hb and its effects on the Hematopoietic Cell Transplantation-specific Comorbidity Index.

The Hematopoietic Cell Transplantation-specific Comorbidity Index (HCT-CI) is used to counsel patients regarding the risk of transplantation and selection of conditioning regimens. Pulmonary disease, most frequently demonstrated by a decreased diffusion capacity of carbon monoxide (DLCO), is the most prevalent comorbidity captured by the HCT-CI. The HCT-CI was validated using the Dinakara method for adjusting DLCO for Hb, but our institution and others utilize the Cotes method. The purpose of this study was to determine the impact of using the Cotes method rather than the Dinakara method on the HCT-CI score. We reviewed pre-transplant pulmonary function tests in 73 patients who underwent allogeneic hematopoietic SCT. Patients were stratified into low, intermediate or high-risk groups based on HCT-CI scores of 0, 1-2 or 3, respectively. We found that compared with the Dinakara method, the Cotes method increased the HCT-CI score in 45% of patients and resulted in total HCT-CI scores predictive of higher non-relapse mortality in 33% of patients. These results indicate that if an institution uses the Cotes method to adjust DLCO for Hb, their patients may be counseled to expect a higher risk of mortality than is actually predicted by the HCT-CI, and may be excluded from transplantation. Therefore, unless the HCT-CI is validated using other methods for correcting DLCO for Hb, the Dinakara method should be used.

Safety, efficacy and biological predictors of response to sequential azacitidine and lenalidomide for elderly patients with acute myeloid leukemia.

Acute myeloid leukemia (AML) is a disease of the elderly. Poor outcomes with standard therapies necessitate novel approaches. Outpatient regimens sufficiently potent and well tolerated to induce remissions and enable continuation therapy may be beneficial. In this phase-1 study, we determined the maximum tolerated dose (MTD) and the efficacy for sequential azacitidine and lenalidomide as remission induction and continuation therapy in elderly, previously untreated patients. We investigated the impact on global DNA methylation and bone marrow cytokines, and sought biological predictors of response. Eighteen patients were enrolled. The MTD was not reached. Median follow-up was 8.2 months (10.3 months for survivors). Common adverse events included fatigue, injection site reactions, constipation, nausea, pruritus and febrile neutropenia. Ten patients responded (56%), and the rate of complete remissions (CRs) or CRs with incomplete recovery of blood counts for evaluable patients was 44% (7/16). The median response duration was 6.2 months. DNA demethylation and changes in bone marrow cytokines were observed; responders had a unique cytokine profile and a trend towards lower methylation levels. Sequential azacitidine and lenalidomide was well tolerated with encouraging clinical and biological activity in previously untreated elderly AML patients. This trial is registered at ClinicalTrials.gov (NCT00890929).

Outcomes of patients with AML and MDS who relapse or progress after reduced intensity allogeneic hematopoietic cell transplantation.

We describe treatment, outcomes and prognostic factors for patients who relapse following transplantation with a reduced intensity conditioning regimen. Seventy consecutive patients with high-risk myeloid malignancies underwent transplant and 25 (36%) relapsed, a median of 120 days later. The median percentage of bone marrow blasts at relapse was 24, the median donor chimerism was 73% and new karyotypic abnormalities occurred in 8 out of 20 (40%) evaluable patients. Twenty-one patients (84%) received aggressive treatment for relapse, including chemotherapy (60%), second hematopoietic cell transplantation (HCT; 52%) and/or donor lymphocyte infusion (DLI; 12%). Thirteen achieved a complete response (CR) and four remain in CR. Median overall survival (OS) after relapse was 6 months (95% confidence interval=2.7-9.9 months), and actuarial 1 year OS was 24%. Most deaths were due to disease progression (17/20, 85%). We did not observe an advantage for cellular therapy (DLI or second transplant) compared to chemotherapy. Salvage therapy for relapse after reduced intensity HCT is feasible, associated with low treatment-related mortality, and may result in prolonged survival in select patients. Studies exploring the optimal treatment for relapse following reduced intensity HCT are warranted.

Pre-transplant ganciclovir and post transplant high-dose valacyclovir reduce CMV infections after alemtuzumab-based conditioning.

Alemtuzumab (Campath-1H)-based conditioning regimens are effective in preventing GVHD, but are associated with very high rates of cytomegalovirus (CMV) infection, a major limitation to their use. We evaluated 85 patients receiving conditioning with fludarabine 30 mg/m2/day (day -7 to day -3), alemtuzumab 20 mg/day (day -7 to day -3), and melphalan 140 mg/m2 on day -2. The initial patients received post transplant CMV prophylaxis with high-dose acyclovir. A very high incidence of CMV viremia was observed as has been commonly reported after alemtuzumab-based conditioning. Sixty-seven subsequent patients received pre-transplant ganciclovir and high-dose valacyclovir after engraftment. The cumulative incidence of CMV infection in the valacyclovir cohort was 29%. This compared favorably to the cumulative incidence of 53% in patients receiving only acyclovir (P = 0.004) and to literature data. CMV prophylaxis with pre-transplant ganciclovir and high-dose valacyclovir after engraftment appears effective in preventing the excessive incidence of CMV infection after alemtuzumab-based conditioning regimens.