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Identification of agents that target human leukemia stem cells is an important consideration for the development of new therapies. The present study demonstrates that rocaglamide and silvestrol, closely related natural products from the flavagline class of compounds, are able to preferentially kill functionally defined leukemia stem cells, while sparing normal stem and progenitor cells. In addition to efficacy as single agents, flavaglines sensitize leukemia cells to several anticancer compounds, including front-line chemotherapeutic drugs used to treat leukemia patients. Mechanistic studies indicate that flavaglines strongly inhibit protein synthesis, leading to the reduction of short-lived antiapoptotic proteins. Notably though, treatment with flavaglines, alone or in combination with other drugs, yields a much stronger cytotoxic activity toward leukemia cells than the translational inhibitor temsirolimus. These results indicate that the underlying cell death mechanism of flavaglines is more complex than simply inhibiting general protein translation. Global gene expression profiling and cell biological assays identified Myc inhibition and the disruption of mitochondrial integrity to be features of flavaglines, which we propose contribute to their efficacy in targeting leukemia cells. Taken together, these findings indicate that rocaglamide and silvestrol are distinct from clinically available translational inhibitors and represent promising candidates for the treatment of leukemia.

In spite of the chemosensitivity seen with the initial treatment of malignant lymphoid disorders, relapse is common and death most often occurs as a result of disease progression. This is related to a multitude of resistance mechanisms associated with the various lymphoproliferative disorders. As a result, therapies targeting intrinsic drug-resistance mechanisms are evolving and have become an active area of research. In vitro studies of human chronic lymphocytic leukemia cells incubated with theophylline, a phosphodiesterase inhibitor, resulted in downregulation of bcl-2 concomitant with induction of apoptosis. We describe the preclinical basis for a novel combination therapy involving pentostatin (Nipent; SuperGen, San Ramon, CA), chlorambucil, and theophylline in the treatment of patients with relapsed chronic lymphoproliferative disorders. An ongoing study based on such justification, which is currently accruing patients, is also described. Results from this trial appear promising, and a phase II study is now being planned.

We have identified and characterized a previously unrecognized form of acute leukemia that shares features of both myeloid and natural killer (NK) cells. From a consecutive series of 350 cases of adult de novo acute myeloid leukemia (AML), we identified 20 cases (6%) with a unique immunophenotype: CD33+, CD56+, CD11a+, CD13lo, CD15lo, CD34+/-, HLA-DR-, CD16-. Multicolor flow cytometric assays confirmed the coexpression of myeloid (CD33, CD13, CD15) and NK cell-associated (CD56) antigens in each case, whereas reverse transcription polymerase chain reaction (RT-PCR) assays confirmed the identity of CD56 (neural cell adhesion molecule) in leukemic blasts. Although two cases expressed CD4, no case expressed CD2, CD3, or CD8 and no case showed clonal rearrangement of genes encoding the T-cell receptor (TCR beta, gamma, delta). Leukemic blasts in the majority of cases shared unique morphologic features (deeply invaginated nuclear membranes, scant cytoplasm with fine azurophilic granularity, and finely granular Sudan black B and myeloperoxidase cytochemical reactivity) that were remarkably similar to those of acute promyelocytic leukemia (APL); particularly the microgranular variant (FAB AML-M3v). However, all 20 cases lacked the t(15;17) and 17 cases tested lacked the promyelocytic/retinoic acid receptor alpha (RAR alpha) fusion transcript in RT-PCR assays; 12 cases had 46,XX or 46,XY karyotypes, whereas 2 cases had abnormalities of chromosome 17q: 1 with del(17)(q25) and the other with t(11;17)(q23;q21) and the promyelocytic leukemia zinc finger/RAR alpha fusion transcript. All cases tested (6/20), including the case with t(11;17), failed to differentiate in vitro in response to all-trans retinoic acid (ATRA), suggesting that these cases may account for some APLs that have not shown a clinical response to ATRA. Four of 6 cases tested showed functional NK cell-mediated cytotoxicity, suggesting a relationship between these unique CD33+, CD56+, CD16- acute leukemias and normal CD56+, CD16- NK precursor cells. Using a combination of panning and multiparameter flow cytometric sorting, we identified a normal CD56+, CD33+, CD16- counterpart cell at a frequency of 1% to 2% in the peripheral blood of healthy individuals. Our studies suggest that this form of acute leukemia may arise from transformation of a precursor cell common to both the myeloid and NK cell lineages; thus we propose the designation myeloid/NK acute leukemia. Recognition of this new leukemic entity will be important in distinguishing these ATRA-nonresponsive cases from ATRA-responsive true APL.

Despite the major advances that have been made over the past few decades in the management of adult acute leukemia, a substantial number of the patients still die from the underlying disease. Therefore, it is essential that we vigorously pursue efforts to discover and develop novel therapeutic agents for the treatment of leukemia.

This article presents data from the phase I and II clinical investigations of Fludara I.V. (fludarabine phosphate) (NSC 312887), which is the 5'-phosphorylated derivative of the novel antimetabolite, 9-beta-D-arabinofuranosyl-2-fluoroadenine. The comprehensive phase I evaluation of this new antitumor agent was conducted in 51 patients with advanced malignancy and 15 additional patients with aggressive forms of leukemia. Three separate phase I schedules of drug administration were examined. Myelosuppression was the dose-limiting toxicity on each schedule administered to patients with solid tumors. The drug was also examined at higher doses in patients with leukemia, and the dose-limiting toxicity on the high-dose protocol was unacceptable: serious neurologic toxicity. The observation of antitumor responses in patients with advanced non-Hodgkin's lymphoma prompted additional phase II investigation in patients with lymphoproliferative malignancy. The encouraging phase II data demonstrate that Fludara I.V. has promise for patients with low-grade histologic subtypes of non-Hodgkin's lymphoma and chronic lymphocytic leukemia. While interesting additional basic and clinical research projects regarding Fludara I.V. remain, it is important to expeditiously pursue approval for this drug. Adequate data exists to demonstrate that the low-dose administration of Fludara I.V. is both safe and effective. While the development of this drug has stimulated renewed interest in the clinical investigation of the chronic lymphoproliferative malignancies, the time for making it readily available to these patients has arrived.

Urinary nucleosides offer a number of useful laboratory and clinical applications in the study and analysis of leukemia. There are significant differences in the excretion of modified nucleosides between normal individuals and individuals with various forms of leukemia, as well as between leukemia patients at opposite ends of the clinical spectrum, i.e., those with active disease and those in remission. The nucleoside excretion levels correlate to bone marrow tumor burden in certain forms of leukemia, and limited serial data indicate the potential value of the nucleosides for predicting relapse before the disease deterioration can be recognized clinically. In addition, it may be feasible to assess the effectiveness of chemotherapy used in the treatment of leukemia much more rapidly with the urinary nucleoside markers than with conventional invasive methods.

A deficiency of adenosine deaminase, an enzyme important in purine nucleoside catabolism, is associated with a severe combined immunodeficiency disease in children. Inhibition of this enzyme in vitro and in vivo results in an impairment in lymphoblast proliferation. We have investigated the pharmacologic inhibition of this enzyme by 2'-deoxycoformycin in 15 patients with hematologic malignancies. Biochemical consequences of the administration of this agent were closely monitored in erythrocytes, nucleated peripheral blood and bone marrow cells, serum, and urine. A marked rise in erythrocyte dATP was accompanied by a depletion of ATP in those patients exhibiting toxicity. Most patients excreted large amounts of deoxyadenosine but not adenosine in the urine. Serum deoxyadenosine rose in patients demonstrating a marked decrease in cell mass. The biochemical disturbances and clinical toxicity, including hepatic, renal, and conjunctival abnormalities, were usually reversible. Central nervous system toxicity, which potentially was the most serious consequence, was associated with high erythrocyte dATP/ATP ratios and high levels of cerebrospinal fluid deoxyadenosine. In patients with lymphoma and leukemia, objective responses were observed but were short-lived. Patients with chronic lymphocytic leukemia receiving weekly low doses of the drug demonstrated minimal toxicity and some efficacy. The chemotherapeutic potential o 2'-deoxycoformycin, as either a single agent or in combination with Ara-A, merits further exploration.

Dinaciclib (SCH727965) is a selective CDKi chosen for clinical development based upon a favorable therapeutic index in cancer xenograft models. We performed a phase I dose escalation study of dinaciclib in relapsed and refractory chronic lymphocytic leukemia (CLL) patients with intact organ function and WBC<200 × 10(9) /l. Five separate dose levels (5 mg/m(2), 7 mg/m(2), 10 mg/m(2), 14 mg/m(2) and 17 mg/m(2)) were explored dosing on a weekly schedule × 3 with 1 week off (4-week cycles) using a standard 3+3 design with expansion cohorts to optimize safety. Fifty-two patients were enrolled with relapsed and refractory CLL. Escalation through cohorts occurred with two dose-limiting toxicity (DLTs) at the 17 mg/m(2) dose (tumor lysis syndrome (TLS) and pneumonia). The phase II expansion occurred at 14 mg/m(2) with 16 patients receiving this dose with one DLT (TLS). Additional stepped up dosing to the maximum tolerated dose was examined in 19 patients at this dose. Adverse events included cytopenias, transient laboratory abnormalities and TLS. Responses occurred in 28 (54%) of patients independent of del(17)(p13.1) with a median progression-free survival of 481 days. Dinaciclib is clinically active in relapsed CLL including those patients with high risk del(17)(p13.1) disease and warrants future study. [ABSTRACT FROM AUTHOR]

Alemtuzumab (anti-CD52; Campath-1H) is effective in fludarabine-refractory chronic lymphocytic leukemia (CLL), but is associated with infection and early onset neutropenia. To reduce toxicity, filgrastim (G-CSF) was administered concurrently with alemtuzumab. In total, 14 CLL patients (median age 59) with a median of 3.5 prior regimens (range 1–12) received i.v. alemtuzumab, stepped up from 3 to 30 mg the first week, then 30 mg thrice weekly for 12 weeks. Filgrastim 5 μg/kg was administered daily 5 days before and throughout alemtuzumab therapy. Six patients developed cytomegalovirus (CMV) reactivation 3–6 weeks into treatment; six patients developed fever, three neutropenia, and one pneumonia. The patient with CMV pneumonia died; ganciclovir cleared CMV in the other patients. Five patients developed early neutropenia (weeks 2–5). Four patients developed delayed neutropenia (weeks 10–13) unassociated with CMV reactivation. Nine patients ceased therapy because of infectious and hematologic toxicity. Five partial responses were noted, all in patients with lymph nodes >5 cm, lasting a median of 6.5 months (range 5–13). Filgrastim and alemtuzumab were given concurrently with manageable infusion toxicity and clinical activity, but the efficacy of this regimen was limited by delayed neutropenia of unclear etiology and CMV reactivation. Filgrastrim should not be administered prophylactically during alemtuzumab therapy outside clinical trials.Leukemia (2005) 19, 1207–1210. doi:10.1038/sj.leu.2403782 Published online 28 April 2005 [ABSTRACT FROM AUTHOR]

Background: BRAF V600E is the genetic lesion underlying hairy-cell leukemia. We assessed the safety and activity of the oral BRAF inhibitor vemurafenib in patients with hairy-cell leukemia that had relapsed after treatment with a purine analogue or who had disease that was refractory to purine analogues.Methods: We conducted two phase 2, single-group, multicenter studies of vemurafenib (at a dose of 960 mg twice daily)--one in Italy and one in the United States. The therapy was administered for a median of 16 weeks in the Italian study and 18 weeks in the U.S. study. Primary end points were the complete response rate (in the Italian trial) and the overall response rate (in the U.S. trial). Enrollment was completed (28 patients) in the Italian trial in April 2013 and is still open (26 of 36 planned patients) in the U.S. trial.Results: The overall response rates were 96% (25 of 26 patients who could be evaluated) after a median of 8 weeks in the Italian study and 100% (24 of 24) after a median of 12 weeks in the U.S. study. The rates of complete response were 35% (9 of 26 patients) and 42% (10 of 24) in the two trials, respectively. In the Italian trial, after a median follow-up of 23 months, the median relapse-free survival was 19 months among patients with a complete response and 6 months among those with a partial response; the median treatment-free survival was 25 months and 18 months, respectively. In the U.S. trial, at 1 year, the progression-free survival rate was 73% and the overall survival rate was 91%. Drug-related adverse events were usually of grade 1 or 2, and the events most frequently leading to dose reductions were rash and arthralgia or arthritis. Secondary cutaneous tumors (treated with simple excision) developed in 7 of 50 patients. The frequent persistence of phosphorylated ERK-positive leukemic cells in bone marrow at the end of treatment suggests bypass reactivation of MEK and ERK as a resistance mechanism.Conclusions: A short oral course of vemurafenib was highly effective in patients with relapsed or refractory hairy-cell leukemia. (Funded by the Associazione Italiana per la Ricerca sul Cancro and others; EudraCT number, 2011-005487-13; ClinicalTrials.gov number NCT01711632.). [ABSTRACT FROM AUTHOR]