Timed sequential therapy of acute myelogenous leukemia in adults: a phase II study of retinoids in combination with the sequential administration of cytosine arabinoside, idarubicin and etoposide

Dose intensity for induction in acute myeloid leukemia: what, when, and for whom?

Intensive chemotherapy has been the backbone of the treatment of acute myeloid leukemia (AML) for decades. However, an increase in novel targeted agents, which has been brought about in part by a deeper understanding of the genetic makeup of AML, has led to remission-inducing regimens that do not require traditional cytotoxic agents. Combinations of a hypomethylating agent (HMA) and venetoclax have doubled the chance of remission for patients considered unfit for induction chemotherapy who would have traditionally been offered singleagent HMA. In fact, this regimen may rival the complete remission rate achieved with induction chemotherapy for certain populations such as the very elderly and those with secondary AML, but equivalency has yet to be established. Further advances include the addition of gemtuzumab ozogamicin and FLT3 inhibitors to induction chemotherapy, which improves survival for patients with core-binding factor and FLT3-mutated AML, respectively. Still, much work is needed to improve the outcomes of the highest-risk subgroups: frail patients and those with high-risk cytogenetics and/or TP53 mutations. Promisingly, the landscape of AML therapy is shifting dramatically and no longer is intensity, when feasible, always the best answer for AML.

Timed sequential therapy for acute myelogenous leukemia: Results of a retrospective study of 301 patients and review of the literature

Timed sequential therapy (TST) aims to improve outcomes in acute myelogenous leukemia (AML) by harnessing drug-induced cell cycle kinetics of AML, where a second drug is timed to coincide with peak leukemia proliferation induced by the first drugs. We analyzed outcomes in 301 newly diagnosed AML patients treated from 2004-2013 with cytarabine, anthracycline, and etoposide TST induction. Median age was 52 (range 20-74) and complete remission rate 68%. With median follow-up 5.8 years, 5-year DFS and overall survival (OS) were 37% (95% CI 31-45%) and 32% (95% CI 27-38%), respectively. In multivariate analysis, older age, unfavorable cytogenetics, and WBC≥50×10⁹/L resulted in worse OS. Among patients not undergoing blood and marrow transplant, a propensity score analysis, which reduces imbalance in baseline characteristics, showed consolidation with TST compared with 1 or more cycles high-dose cytarabine trended toward lower DFS and post-remission survival with hazard ratio (HR) 1.9 (95% CI 0.9-4.0), and 1.6 (95% CI 0.7-3.6), respectively. Our results demonstrate the efficacy and feasibility of TST induction for newly diagnosed patients with AML, with results comparable to that seen in clinical trials with other TST therapies and 7+3.

Meta-analysis of gene expression in relapsed childhood B-acute lymphoblastic leukemia

Background

Relapsed pediatric B-acute lymphoblastic leukemia (B-ALL) remains as the leading cause of cancer death among children. Other than stem cell transplantation and intensified chemotherapy, no other improved treatment strategies have been approved clinically. Gene expression profiling represents a powerful approach to identify potential biomarkers and new therapeutic targets for various diseases including leukemias. However, inadequate sample size in many individual experiments has failed to provide adequate study power to yield translatable findings. With the hope of getting new insights into the biological mechanisms underpinning relapsed ALL and identifying more promising biomarkers or therapeutic targets, we conducted a meta-analysis of gene expression studies involving ALL from 3 separate studies.

Method

By using the keywords “acute lymphoblastic leukemia”, and “microarray”, a total of 280 and 275 microarray datasets were found listed in Gene Expression Omnibus database GEO and ArrayExpress database respectively. Further manual inspection found that only three studies (GSE18497, GSE28460, GSE3910) were focused on gene expression profiling of paired diagnosis-relapsed pediatric B-ALL. These three datasets which comprised of a total of 108 matched diagnosis-relapsed pediatric B-ALL samples were then included for this meta-analysis using RankProd approach.

Results

Our analysis identified a total of 1795 upregulated probes which corresponded to 1527 genes (pfp < 0.01; FC > 1), and 1493 downregulated probes which corresponded to 1214 genes (pfp < 0.01; FC < 1) respectively. S100A8 appeared as the top most overexpressed gene (pfp < 0.01, FC = 1.8) and is a potential target for further validation. Based on gene ontology biological process annotation, the upregulated genes were most enriched in cell cycle processes (enrichment score = 15.3), whilst the downregulated genes were clustered in transcription regulation (enrichment score = 12.6). Elevated expression of cell cycle regulators (e.g kinesins, AURKA, CDKs) was the key genetic defect implicated in relapsed ALL, and serve as attractive targets for therapeutic intervention.

Conclusion

We identified S100A8 as the most overexpressed gene, and the cell cycle pathway as the most promising biomarker and therapeutic target for relapsed childhood B-ALL. The validity of the results warrants further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3103-1) contains supplementary material, which is available to authorized users.

Potential role for all-trans retinoic acid in nonpromyelocytic acute myeloid leukemia

All-trans retinoic acid (ATRA) has been very successful in the subtype of acute myelogenous leukemia known as acute promyelocytic leukemia due to targeted reactivation of retinoic acid signaling. There has been great interest in applying this form of differentiation therapy to other cancers, and numerous clinical trials have been initiated. However, ATRA as monotherapy has thus far shown little benefit in nonacute promyelocytic leukemia acute myelogenous leukemia. Here, we review the literature on the use of ATRA in combination with chemotherapy, epigenetic modifying agents and targeted therapy, highlighting specific patient populations where the addition of ATRA to existing therapies may provide benefit. Furthermore, we discuss the impact of recent whole genome sequencing efforts in leading the design of rational combinatorial approaches.

Timed-sequential chemotherapy as induction and/or consolidation regimen for younger adults with acute myelogenous leukemia

Increasing the intensity of induction chemotherapy has generated considerable recent interest in the treatment of acute myeloid leukemia. Achieving complete remission is a sine qua non condition for prolonged disease-free survival and may affect long-term outcome. In this setting, administering a repeat course of induction shortly after completion of the first course, known as timed-sequential chemotherapy (TSC), has been tested and may lead to an improved long-term outcome. Whether these results are due to the biologic recruitment of cell cycle-specific agents is unknown. However, this strategy to intensify induction may lead to more profound myelosuppression and to potential toxicities. Here we review the results of timed-sequential chemotherapy, used as induction regimen in de novo, relapsed or refractory AML or used as post-remission therapy, and compare them with those from other types of regimens.

High expression of lactotriaosylceramide, a differentiation-associated glycosphingolipid, in the bone marrow of acute myeloid leukemia patients

Glycosphingolipids (GSLs) are information-bearing biomolecules that play critical roles in embryonic development, signal transduction and carcinogenesis. Previous studies indicate that certain GSLs are associated with differentiation in acute myeloid leukemia (AML) cells. In this study, we collected bone marrow samples from healthy donors and AML patients and analyzed the GSL expression profiles comprehensively using electrospray ionization linear ion-trap mass spectrometry. The results showed that AML patients had higher expression of the GSL lactotriaosylceramide (Lc3), GM3 and neolactotetraosylceramide (nLc4) in their bone marrow than did the healthy donors (P < 0.05), especially the M1 subtype of AML. To further explore the molecular mechanisms of Lc3, we examined the expression of the Lc3 synthase β1,3-N-acetylglucosaminyltransferase5 (β3Gn-T5) and found that the bone marrow samples of AML patients had 16-fold higher expression of β3Gn-T5 than those of healthy donors (P < 0.05). Our results suggest that AML-associated GSLs Lc3, GM3 and nLc4 are possibly involved in initiation and differentiation of AML.

Acute myeloid leukaemia: optimal management and recent developments

The current treatment of patients with acute myeloid leukaemia yields poor results, with expected cure rates in the order of 30-40% depending on the biological characteristics of the leukaemic clone. Therefore, new agents and schemas are intensively studied in order to improve patients' outcomes. This review summarizes some of these new paradigms, including new questions such as which anthracycline is most effective and at what dose. High doses of daunorubicin have shown better responses in young patients and are well tolerated in elderly patients. Monoclonal antibodies are promising agents in good risk patients. Drugs blocking signalling pathways could be used in combination with chemotherapy or in maintenance with promising results. Epigenetic therapies, particularly after stem cell transplantation, are also discussed. New drugs such as clofarabine and flavopiridol are reviewed and the results of their use discussed. It is clear that many new approaches are under study and hopefully will be able to improve on the outcomes of the commonly used '7+3' regimen of an anthracycline plus cytarabine with daunorubicin, which is clearly an ineffective therapy in the majority of patients.

Multi-institutional phase 2 clinical and pharmacogenomic trial of tipifarnib plus etoposide for elderly adults with newly diagnosed acute myelogenous leukemia

Tipifarnib (T) exhibits modest activity in elderly adults with newly diagnosed acute myelogenous leukemia (AML). Based on preclinical synergy, a phase 1 trial of T plus etoposide (E) yielded 25% complete remission (CR). We selected 2 comparable dose levels for a randomized phase 2 trial in 84 adults (age range, 70-90 years; median, 76 years) who were not candidates for conventional chemotherapy. Arm A (T 600 mg twice a day × 14 days, E 100 mg days 1-3 and 8-10) and arm B (T 400 mg twice a day × 14 days, E 200 mg days 1-3 and 8-10) yielded similar CR, but arm B had greater toxicity. Total CR was 25%, day 30 death rate 7%. A 2-gene signature of high RASGRP1 and low aprataxin (APTX) expression previously predicted for T response. Assays using blasts from a subset of 40 patients treated with T plus E on this study showed that AMLs with a RASGRP1/APTX ratio of more than 5.2 had a 78% CR rate and negative predictive value 87%. This ratio did not correlate with outcome in 41 patients treated with conventional chemotherapies. The next T-based clinical trials will test the ability of the 2-gene signature to enrich for T responders prospectively. This study is registered at www.clinicaltrials.gov as #NCT00602771.

A network meta-analysis of randomized controlled trials of induction treatments in acute myeloid leukemia in the elderly

BACKGROUND

The optimal induction treatment of acute myeloid leukemia (AML) in the clinically and biologically heterogeneous group of elderly patients is not well-defined since direct comparisons between treatments is limited.

OBJECTIVE

The aim of this study was to estimate the relative effectiveness of induction treatments in AML elderly patients.

METHODS

A network of multiple treatments meta-analysis was performed by combining direct and indirect evidence from published randomized controlled trials (RCTs). The complete remission (CR) was considered as the outcome of interest. We systematically searched PubMed, EMBASE, and Cochrane Library until September 30, 2010, to identify all RCTs published in English that compared diverse induction chemotherapies in elderly AML patients. Our search strategy focused on RCTs that included AML patients >60 years, considering, however, that age stratification was varied between countries and over time and studies were not necessarily designed to compare elderly patients. Regimens were grouped a priori into 42 different types of induction treatment. Prognostic parameters (age, performance status, unfavorable cytogenetics, antecedent malignancy), AML outcomes (median disease-free, overall survival, CR, induction deaths), and myelotoxicity parameters (median duration until neutrophil recovery [>1.0 × 10(9)/L], platelet recovery [>100 × 10(9)/L], hospitalization duration) were evaluated for each induction type. In combining direct and indirect evidence, we calculated the odds ratio (OR) for each therapy relative to the most commonly used combination of standard-dose daunorubicin (30-60 mg/m(2) for 3 days) and standard-dose cytarabine (100 mg/m(2) for 7-10 days) that was set as the reference induction treatment.

RESULTS

We identified 65 RCTs (15,110 patients) that described 64 direct comparisons of induction treatments, but only 14 of them showed significant differences in CR after random effects meta-analyses. Median age of included patients was 68, 18.0% had secondary AML, 21.1 % had poor performance status, 26.7% displayed unfavorable cytogenetics, and 49.3% finally achieved CR. No significant differences were observed in the recorded induction toxicity parameters among the treatment arms. Through the network meta-analysis, the addition of all-trans retinoic acids or lomustine to the combination of idarubicin plus cytarabine showed significantly higher CR rate (OR = 1.93 [1.06-3.49] and 1.76 [1.08-2.88], respectively), whereas no treatment, clofarabine, daunorubicin plus topotecan, and the 2 different schedules of gemtuzumab ozogamicin (at 1, 3, and 5 days and at 1 and 8 days) showed a significantly lower CR rate (OR = 0.01 [0.001-0.19], 0.15 [0.04-0.58], 0.03 [0.002-0.64], 0.06 [0.01-0.51], and 0.05 [0.01-0.32], respectively) than that of the reference induction. Median overall survival showed no difference between treatments (P = 0.150) but was significantly increased during the last 30 years (P < 0.001), presumably reflecting advances in AML management.

CONCLUSIONS

Compared with the reference induction, significant differences were found for specific induction regimens, although most compared regimens appeared to have similar efficacy profiles. These results, however, should be interpreted with caution because the network was dominated by indirect comparisons. Data from large RCTs that make direct comparisons between treatments are needed to detect the optimal induction regimen for elderly AML patients.

Tipifarnib in the treatment of newly diagnosed acute myelogenous leukemia

Farnesyltransferase inhibitors (FTIs) represent a new class of signal transduction inhibitors that block the processing of cellular polypeptides that have cysteine terminal residues and, by so doing, interdict multiple pathways involved in proliferation and survival of diverse malignant cell types. Tipifarnib is an orally bioavailable, nonpeptidomimetic methylquinolone FTI that has exhibited clinical activity in patients with myeloid malignancies including elderly adults with acute myelogenous leukemia (AML) who are not candidates for traditional cytotoxic chemotherapy, patients with high-risk myelodysplasia, myeloproliferative disorders, and imatinib-resistant chronic myelogenous leukemia. Because of its relatively low toxicity profile, tipifarnib provides an important alternative to traditional cytotoxic approaches for elderly patients who are not likely to tolerate or even benefit from aggressive chemotherapy. In this review, we will focus on the clinical development of tipifarnib for treatment of newly diagnosed AML, both as induction therapy for elderly adults with poor-risk AML and as maintenance therapy following achievement of first complete remission following induction and consolidation therapies for poor-risk AML. As with all other malignancies, the optimal approach is likely to lie in rational combinations of tipifarnib with cytotoxic, biologic and/or immunomodulatory agents with non-cross-resistant mechanisms of action. Gene expression profiling has identified networks of differentially expressed genes and gene combinations capable of predicting response to single agent tipifarnib. The clinical and correlative laboratory trials in progress and under development will provide the critical foundations for defining the optimal roles of tipifarnib and in patients with AMl and other hematologic malignancies.

Acute myeloid leukemia is characterized by Wnt pathway inhibitor promoter hypermethylation

Nuclear localization of non-phosphorylated, active beta-catenin is a measure of Wnt pathway activation and is associated with adverse outcome in patients with acute myeloid leukemia (AML). While genetic alterations of the Wnt pathway are infrequent in AML, inhibitors of this pathway are silenced by promoter methylation in other malignanices. Leukemia cell lines were examined for Wnt pathway inhibitor methylation and total beta-catenin levels, and had frequent methylation of Wnt inhibitors and upregulated beta-catenin by Western blot and immunofluorescence. One hundred sixty-nine AML samples were examined for methylation of Wnt inhibitor genes. Diagnostic samples from 72 patients with normal cytogenetics who received standard high-dose induction chemotherapy were evaluated for associations between methylation and event-free or overall survival. Extensive methylation of Wnt pathway inhibitor genes was observed in cell lines, and 89% of primary AML samples had at least one methylated gene: DKK1 (16%), DKK3 (8%), RUNX3 (27%), sFRP1 (34%), sFRP2 (66%), sFRP4 (9%), sFRP5 (54%), SOX17 (29%), and WIF1 (32%). In contrast to epithelial tumors, methylation of APC (2%) and RASSF1A (0%) was rare. In patients with AML with normal cytogenetics, sFRP2 and sFRP5 methylation at the time of diagnosis was associated with an increased risk of relapse, and sFRP2 methylation was associated with an increased risk for death. In patients with AML: (a) there is a high frequency of Wnt pathway inhibitor methylation; (b) Wnt pathway inhibitor methylation is distinct from that observed in epithelial malignancies; and (c) methylation of sFRP2 and sFRP5 may predict adverse clinical outcome in patients with normal karyotype AML.

Early lymphocyte recovery after intensive timed sequential chemotherapy for acute myelogenous leukemia: peripheral oligoclonal expansion of regulatory T cells

Few published studies characterize early lymphocyte recovery after intensive chemotherapy for acute myelogenous leukemia (AML). To test the hypothesis that lymphocyte recovery mirrors ontogeny, we characterized early lymphocyte recovery in 20 consecutive patients undergoing induction timed sequential chemotherapy for newly diagnosed AML. Recovering T lymphocytes were predominantly CD4(+) and included a greatly expanded population of CD3(+)CD4(+)CD25(+)Foxp3(+) T cells. Recovering CD3(+)CD4(+)CD25(+)Foxp3(+) T cells were phenotypically activated regulatory T cells and showed suppressive activity on cytokine production in a mixed lymphocyte reaction. Despite an initial burst of thymopoiesis, most recovering regulatory T cells were peripherally derived. Furthermore, regulatory T cells showed marked oligoclonal skewing, suggesting that their peripheral expansion was antigen-driven. Overall, lymphocyte recovery after chemotherapy differs from ontogeny, specifically identifying a peripherally expanded oligoclonal population of activated regulatory T lymphocytes. These differences suggest a stereotyped immunologic recovery shared by patients with newly diagnosed AML after induction timed sequential chemotherapy. Further insight into this oligoclonal regulatory T-cell population will be fundamental toward developing effective immunomodulatory techniques to improve survival for patients with AML.

Epigenetic differences in cytogenetically normal versus abnormal acute myeloid leukemia

BACKGROUND

Methylation of tumor suppression genes (TSGs) is common in myeloid malignancies. However, application of this as a molecular marker for risk stratification in patients with AML is limited.

DESIGN AND METHODS

To elucidate the impact of patterns of TSG methylation on outcome in cytogenetically normal patients, 106 samples from patients with having normal cytogenetic AML were evaluated for methylation of 12 genes by MSP. For sake of comparison, samples from patients with AML and abnormal cytogenetics (n = 63) were also evaluated.

RESULTS

Methylation frequencies in the whole group (n = 169) were similar to previous reports for CDH1 (31%), ER (31%), FHIT (9%), p15 (INK4b) (44%), p73 (25%), and SOCS1 (75%). Methylation of CTNNA1 was observed in 10%, CEBP-α in16%, CEBP-δ in 2%, MLH1 in 24%, MGMT in 11% and DAPK in 2% of AML samples. We find that DNA methylation was more prevalent in patients with normal compared to karyotypically abnormal AML for most genes; CEBPα (20% vs 9%), CTNNA1 (14% vs 4%), and ER (41% vs 19%) (p < 0.05 for all comparisons). In contrast, p73 was more frequently methylated in patients with karyotypic abnormalities (17% vs 38%; p < 0.05), perhaps due to specific silencing of the pro-apoptotic promoter shifting p73 gene expression to the anti-apoptotic transcript. In AML patients with normal cytogenetics, TSG methylation was not associated with event free or overall survival in a multivariate analysis.

CONCLUSIONS

In patients with AML, TSG methylation is more frequent in patients with normal karyotype than those with karyotypic abnormalities but does not confer independent prognostic information for patients with normal cytogenetics.

Phase I clinical and pharmacokinetic study of a novel schedule of flavopiridol in relapsed or refractory acute leukemias

BACKGROUND

A pharmacokinetically derived schedule of flavopiridol administered as a 30 min intravenous bolus followed by 4-hour continuous intravenous infusion (IVB/CIVI) is active in fludarabine-refractory chronic lymphocytic leukemia, but no studies examining the feasibility and maximum tolerated dose of this schedule have been reported in acute leukemia.

DESIGN AND METHODS

We conducted a phase I dose escalation trial of single-agent flavopiridol in adults with relapsed/refractory acute leukemias, utilizing a modification of the intravenous bolus/continuous intravenous infusion approach, intensifying treatment for administration on days 1, 2, and 3 of 21-day cycles.

RESULTS

Twenty-four adults with relapsed/refractory acute myeloid leukemia (n=19) or acute lymphoblastic leukemia (n=5) were enrolled. The median age was 62 years (range, 23-78). The maximum tolerated dose of flavopiridol was 40 mg/m(2) intravenous bolus plus 60 mg/m(2) continuous intravenous infusion (40/60). The dose limiting toxicity was secretory diarrhea. Life-threatening hyperacute tumor lysis syndrome requiring hemodialysis on day 1 was observed in one patient. Pharmacokinetics were dose-dependent with increased clearance observed at the two highest dose levels. Diarrhea occurrence and severity significantly correlated with flavopiridol concentrations at the end of the 4-hour infusion, volume of distribution, and elimination half-life. Modest anti-leukemic activity was observed, with most patients experiencing dramatic but transient reduction/clearance of circulating blasts lasting for 10-14 days. One refractory acute myeloid leukemia patient had short-lived complete remission with incomplete count recovery.

CONCLUSIONS

Flavopiridol as a single agent given by intravenous bolus/continuous intravenous infusion causes marked, immediate cytoreduction in relapsed/refractory acute leukemias, but objective clinical responses were uncommon. With this schedule, the dose is limited by secretory diarrhea.

Clinical activity of sequential flavopiridol, cytosine arabinoside, and mitoxantrone for adults with newly diagnosed, poor-risk acute myelogenous leukemia

Flavopiridol, a cyclin-dependent kinase inhibitor, is cytotoxic to leukemic blasts. In a Phase II study, flavopiridol 50 mg/m(2) was given by 1-h infusion daily x 3 beginning day 1 followed by 2 g/m(2)/72 h ara-C beginning day 6 and 40 mg/m(2) mitoxantrone on day 9 (FLAM) to 45 adults with newly diagnosed acute myelogenous leukemia (AML) with multiple poor-risk features. Thirty patients (67%) achieved complete remission (CR) and 4 (9%) died. Twelve (40%) received myeloablative allogeneic bone marrow transplant (BMT) in first CR. Median OS and DFS are not reached (67% alive 12.5-31 months, 58% in CR 11.4-30 months), with median follow-up 22 months. Sixteen received FLAM in CR, with median OS and DFS 9 and 13.1 months, and 36% alive at 21-31 months. Short OS and DFS correlated with adverse cytogenetics, regardless of age or treatment in CR. The addition of allogeneic BMT in CR translates into long OS and DFS in the majority of eligible patients.

Active oral regimen for elderly adults with newly diagnosed acute myelogenous leukemia: a preclinical and phase 1 trial of the farnesyltransferase inhibitor tipifarnib (R115777, Zarnestra) combined with etoposide

The farnesyltransferase inhibitor tipifarnib exhibits modest activity against acute myelogenous leukemia. To build on these results, we examined the effect of combining tipifarnib with other agents. Tipifarnib inhibited signaling downstream of the farnesylated small G protein Rheb and synergistically enhanced etoposide-induced antiproliferative effects in lymphohematopoietic cell lines and acute myelogenous leukemia isolates. We subsequently conducted a phase 1 trial of tipifarnib plus etoposide in adults over 70 years of age who were not candidates for conventional therapy. A total of 84 patients (median age, 77 years) received 224 cycles of oral tipifarnib (300-600 mg twice daily for 14 or 21 days) plus oral etoposide (100-200 mg daily on days 1-3 and 8-10). Dose-limiting toxicities occurred with 21-day tipifarnib. Complete remissions were achieved in 16 of 54 (30%) receiving 14-day tipifarnib versus 5 of 30 (17%) receiving 21-day tipifarnib. Complete remissions occurred in 50% of two 14-day tipifarnib cohorts: 3A (tipifarnib 600, etoposide 100) and 8A (tipifarnib 400, etoposide 200). In vivo, tipifarnib plus etoposide decreased ribosomal S6 protein phosphorylation and increased histone H2AX phosphorylation and apoptosis. Tipifarnib plus etoposide is a promising orally bioavailable regimen that warrants further evaluation in elderly adults who are not candidates for conventional induction chemotherapy. These clinical studies are registered at www.clinicaltrials.gov as #NCT00112853.

Phase II trial of tipifarnib as maintenance therapy in first complete remission in adults with acute myelogenous leukemia and poor-risk features

PURPOSE

Acute myelogenous leukemia (AML) does not have a high cure rate, particularly in patients with poor-risk features. Such patients might benefit from additional therapy in complete remission (CR). Tipifarnib is an oral farnesyltransferase inhibitor with activity in AML. We conducted a phase II trial of maintenance tipifarnib monotherapy for 48 adults with poor-risk AML in first CR.

EXPERIMENTAL DESIGN

Tipifarnib 400 mg twice daily for 14 of 21 days was initiated after recovery from consolidation chemotherapy, for a maximum of 16 cycles (48 weeks).

RESULTS

Twenty (42%) patients completed 16 cycles, 24 (50%) were removed from study for relapse, and 4 (8%) discontinued drug prematurely for intolerance. Nonhematologic toxicities were rare, but tipifarnib dose was reduced in 58% for myelosuppression. Median disease-free survival (DFS) was 13.5 months (range, 3.5-59+ months), with 30% having DFS >2 years. Comparison of CR durations for 25 patients who received two-cycle timed sequential therapy followed by tipifarnib maintenance with 23 historically similar patients who did not receive tipifarnib showed that tipifarnib was associated with DFS prolongation for patients with secondary AML and adverse cytogenetics.

CONCLUSIONS

This study suggests that some patients with poor-risk AML, including patients with secondary AML and adverse cytogenetics, may benefit from tipifarnib maintenance therapy. Future studies are warranted to examine alternative tipifarnib dosing and continuation beyond 16 cycles.

The role of timed sequential chemotherapy in adult acute myelogenous leukemia

Consecutive trials of timed sequential chemotherapy (TSC) have been conducted in adults with acute myelogenous leukemia. The rationale for TSC was based on the observation that leukemic cells can be recruited synchronously into the cell cycle after initial intensive therapy, at which time they may become more susceptible to killing by chemotherapeutic agents. Achieving complete remission is essential for prolonged disease-free survival and may affect long-term outcome. TSC has led to higher rates of complete remission and has improved long-term outcomes. This article reviews the results of important trials in which TSC was used as an induction regimen in de novo, relapsed, or refractory acute myelogenous leukemia or as postremission therapy.

Sequential flavopiridol, cytosine arabinoside, and mitoxantrone: a phase II trial in adults with poor-risk acute myelogenous leukemia

PURPOSE

Flavopiridol is a cyclin-dependent kinase inhibitor that is cytotoxic to leukemic blasts. In a phase I study of flavopiridol followed by 1-beta-d-arabinofuranosylcytosine (ara-C) and mitoxantrone, overall response rate for adults with relapsed and refractory acute myelogenous leukemias (AML) was 31%. We have now completed a phase II study of sequential flavopiridol, ara-C, and mitoxantrone in 62 adults with poor-risk AML.

EXPERIMENTAL DESIGN

Flavopiridol (50 mg/m(2)) was given by 1-h infusion daily x 3 beginning day 1 followed by 2 gm/m(2)/72 h ara-C beginning day 6 and 40 mg/m(2) mitoxantrone on day 9.

RESULTS

Flavopiridol caused a > or =50% decrease in peripheral blood blasts in 44% by median day 2 and > or =80% decrease in 26% by day 3. Self-limited tumor lysis occurred in 53%. Three (5%) died during therapy (2 multiorgan failure and 1 fungal pneumonia). Complete remissions (CR) were achieved in 12 of 15 (75%) newly diagnosed secondary AML, 18 of 24 (75%) first relapse after short CR (median CR, 9 months, including prior allotransplant), and 2 of 13 (15%) primary refractory but 0 of 10 multiply refractory AML. Disease-free survival for all CR patients is 40% at 2 years, with newly diagnosed patients having a 2-year disease-free survival of 50%.

CONCLUSIONS

Flavopiridol has anti-AML activity directly and in combination with ara-C and mitoxantrone. This timed sequential regimen induces durable CRs in a significant proportion of adults with newly diagnosed secondary AML (including complex cytogenetics) and adults with AML in first relapse after short first CR.

Successful therapy must eradicate cancer stem cells

Despite significant improvements in cancer therapy, tumor recurrence is frequent and can be due to a variety of mechanisms, including the evolution of resistance and tumor progression. Cancer stem cells have been postulated to maintain tumor growth similar to normal stem cells maintaining tissue homeostasis. Recently, the existence of these malignant stem cells has been proven for hematological as well as some solid tumors. Tumor stem cells are not targeted by standard therapy and might be responsible for treatment failure and tumor recurrence in many patients. We designed a simple mathematical model to demonstrate the importance of eliminating tumor stem cells. We explored different therapeutic scenarios to illustrate the properties required from novel therapeutic agents for successful tumor treatment. We show that successful therapy must eradicate tumor stem cells.

The histone deacetylase inhibitor valproic acid alters sensitivity towards all trans retinoic acid in acute myeloblastic leukemia cells

Acute myeloblastic leukemia (AML) may be classified in a number of ways. Using the French American British classification, the M3 form of the disease or acute promyelocytic leukemia (APL) has been found to be sensitive in vitro and in vivo to the retinoid all trans retinoic acid (ATRA). The mechanism for this is by restoration of normal gene expression through the release of histone deacetylase complexes (HDACs). In contrast to APL, other forms of AML are either nonresponsive or show blunted responses to ATRA. We evaluated if the inhibitor of HDAC activity, valproic acid (VPA), could mimic or enhance retinoid sensitivity in the AML cell line, OCI/AML-2, and clinical samples derived from patients with AML. An Affymetrix GeneChip experiment demonstrated that VPA modulated the expression of numerous genes in OCI/AML-2 cells that were not affected by ATRA including p21, a retinoid responsive gene in APL. VPA induced p21 expression in OCI/AML-2 cells and the majority of the AML samples tested; this was associated with cell cycle arrest and apoptosis not seen with ATRA alone. The addition of ATRA to VPA accentuated many of these responses, supporting the potential beneficial combination of these drugs in the treatment of AML.

A phase II study of timed sequential therapy of acute myelogenous leukemia (AML) for patients over the age of 60: two cycle timed sequential therapy with topotecan, ara-C and mitoxantrone in adults with poor-risk AML

Acute myeloid leukemia (AML) in the elderly is a serious problem characterized by poor response to therapy and short survival. To improve response to therapy, a timed sequential therapy (TST) approach was designed utilizing topotecan, cytosine arabinoside (ara-C) and mitoxantrone based on multiple studies suggesting that topotecan and mitoxantrone are effective in older patients. Thirty-two adults, >or=60-year-old (median age 69) were included. None had favorable cytogenetics and 44% had and antecedent myelodysplastic syndrome (MDS) or 2 degrees AML. Fifty-nine percent achieved a complete response (CR). Median overall survival (OS) was 6.5 months (95% confidence interval (CI): 3.1-12.0 months; range, 15 days to 25.3 months). Disease-free survival (DFS) for the 19 patients achieving a CR was 7.7 months (95% CI: 6.1-13.7 months; range, 2.9-25.3 months). There were no differences in OS or DFS between cytogenetic or disease etiology groups. Although TST was well tolerated, long-term results in this group of patients are not satisfactory and new approaches are needed.

Targeting Vascular Endothelial Growth Factor for Relapsed and Refractory Adult Acute Myelogenous Leukemias

PURPOSE

Vascular endothelial growth factor (VEGF) promotes acute myelogenous leukemia (AML) cell growth and survival and may contribute to drug resistance. bevacizumab, an anti-VEGF monoclonal antibody, exhibits clinical activity against diverse malignancies when administered with cytotoxic chemotherapy. We conducted a Phase II clinical trial of bevacizumab administered after chemotherapy to adults with refractory or relapsed AML, using a timed sequential therapy (TST) approach.

EXPERIMENTAL DESIGN

bevacizumab 10 mg/kg was administered on day 8 after 1-beta-d-arabinofuranosylcytosine 2 g/m(2)/72 h beginning day 1 and mitoxantrone 40 mg/m(2) beginning day 4. In vivo laboratory correlates included AML cell VEGF receptor-1 (FLT-1) expression, marrow microvessel density, and free serum VEGF before and during TST with bevacizumab.

RESULTS

Forty-eight adults received induction therapy. Myelosuppression occurred in all of the patients similar to other TST regimens. Toxicities were decreased ejection fraction (6%), cerebrovascular bleed (4%), and mortality of 15%. Overall response was 23 of 48 (48%), with complete response (CR) in 16 (33%). Eighteen (14 CR and 4 partial response) underwent one consolidation cycle and 5 (3 CR and 2 partial response) underwent allogeneic transplant. Median overall and disease-free survivals for CR patients were 16.2 months (64%, 1 year) and 7 months (35%, 1 year). Marrow blasts demonstrated FLT-1 staining before bevacizumab and marked decrease in microvessel density after bevacizumab. VEGF was detected in pretreatment serum in 67% of patients tested, increased by day 8 in 52%, and decreased in 93% (67% undetectable) 2 h after bevacizumab.

CONCLUSIONS

In this single arm study, cytotoxic chemotherapy followed by bevacizumab yields a favorable CR rate and duration in adults with AML that is resistant to traditional treatment approaches. The clearance of marrow blasts in some patients after bevacizumab suggests that VEGF neutralization might result directly in leukemic cell death. The potential biological and clinical activity of bevacizumab in AML warrants additional clinical and laboratory study.