Acute myeloid leukemia: current progress and future directions

Progress in the understanding of the biology and therapy of acute myeloid leukemia (AML) is occurring rapidly. Since 2017, nine agents have been approved for various indications in AML. These included several targeted therapies like venetoclax, FLT3 inhibitors, IDH inhibitors, and others. The management of AML is complicated, highlighting the need for expertise in order to deliver optimal therapy and achieve optimal outcomes. The multiple subentities in AML require very different therapies. In this review, we summarize the important pathophysiologies driving AML, review current therapies in standard practice, and address present and future research directions.Subject terms: Prognosis, Health services     

Therapy of lymphoid and undifferentiated chronic myelogenous leukemia in blast crisis with continuous vincristine and adriamycin infusions plus high-dose decadron

Thirty patients with Philadelphia chromosome-positive lymphoid (20 patients) or undifferentiated (ten patients) chronic myelogenous leukemia in blast crisis were treated with 0.4 mg of vincristine by continuous intravenous infusion (CIV) daily for 4 days; (doxorubicin) 12 mg/m2 of Adriamycin (Adria Laboratories, Columbus, OH) by continuous intravenous infusion daily for 4 days; and 40 mg of decadron daily on days 1 through 4, 9 through 12, and 17 through 20 (VAD). Course 2 was given starting on day 24 with the addition of cyclophosphamide 1 g/22. Overall nine patients achieved complete remission (30%) and three attained a partial remission (10%), for an overall response rate of 40%. Four patients expired during induction whereas 14 had resistant disease. Response rate was significantly higher for patients with lymphoid compared to undifferentiated morphology (55% versus 10%; P = 0.05). In lymphoid blast crisis, Calla-positive disease was associated with a higher response rate compared to Calla-negative disease (75% versus 25%; P = 0.08). Eleven patients developed infections, and seven had fever without documented infections. The median overall survival was 29 weeks. Median survival was 43 weeks for patients achieving complete remission and 20 weeks for those with resistant disease. Remission duration was 39 weeks. After primary and salvage therapy, nine patients are alive, six of them in continuous remission for 19+ to 112+ weeks. The authors conclude that VAD chemotherapy is an effective regimen with acceptable toxicity in patients with lymphoid blast crisis especially those with Calla-positive disease. Alternate induction regimens for undifferentiated disease and for maintenance therapy are currently being investigated.     

Strategy for breakpoint cluster region analysis in chronic myelocytic leukemia in a routine clinical laboratory

Despite the increasing reliance on breakpoint cluster region (bcr) determinations in diagnosis of chronic myelocytic leukemia (CML), few reports have dealt with the practical aspects of specimen analysis. In the setting of a routine molecular diagnostics laboratory, samples from 68 patients with active CML were evaluated for bcr rearrangements, with the use of a variety of enzymes and two probes. The data have been used to develop an efficient strategy for bcr screening and breakpoint determination. Screening with the universal bcr (UBCR) probe on Xba I and BgI II digests yielded bcr rearrangements in 100% of the Ph1-positive patients and three of the seven Ph1-negative patients, giving bcr analysis a sensitivity of 100%. A single-enzyme screen using the UBCR probe would have resulted in a false negative rate of 10%. The false negative rate was determined during the breakpoint site analysis from additional digests hybridized to both the 3' and UBCR probes. The false negative rate for the 3' probe was 26.5%, because of deletions or 5' rearrangements. The method of breakpoint site determination was dependent on screening results. In 78% of cases, one additional hybridization with two enzyme digests was required. During breakpoint site analysis, a rare false negative result was also demonstrated with Bam HI and Eco RI. This screening strategy has made bcr analysis competitive with cytogenetic analysis at the authors' institution; although turnaround time may be slightly longer, bcr analysis can yield information (such as detecting bcr-positive/Ph1-negative patients and determining breakpoint site) that cannot be obtained by cytogenetics.     

Activity of oral and intravenous 9-aminocamptothecin in SCID mice engrafted with human leukemia

The intravenous (i.v.) injection of the human acute myelogenous leukemia cell line KBM-3 into severe combined immune deficient (SCID) mice results in disseminated multi-organ human disease involvement in these animals which leads to their death over a defined period of time. We utilized this model of human leukemia to investigate the in vivo therapeutic efficacy of the topoisomerase I inhibitor 9-aminocamptothecin (9-AC) given by two different routes. Mice injected with KBM-3 were divided into five groups. Group 1 received only diluent and served as control. The four remaining groups were treated with 9-AC four days a week for three consecutive weeks as follows: group 2 received 1.33 mg/kg/dose, i.v.; group 3, 1.33 mg/kg/dose, orally (p.o.); group 4, 2.0 mg/kg/dose i.v. and group 5, 2.0 mg/kg/dose p.o.. All animals in the control group died from disseminated human leukemia by day 64 from grafting, with a median survival of 59 days. Eleven out of 20 treated mice survived with no evidence of disease and were sacrificed at the termination of the experiment on day 128. PCR-assisted tissue analysis for the presence of human DNA showed no evidence of human leukemia. In conclusion, 9-AC is an active agent in SCID mice engrafted with human myelogenous leukemia and should be explored in phase I-II trials. Oral and intravenous routes are equally effective.     

Phase II study of low-dose decitabine in patients with chronic myelogenous leukemia resistant to imatinib mesylate.

PURPOSE: To determine the activity of decitabine, a DNA methylation inhibitor, in imatinib-refractory or intolerant chronic myelogenous leukemia. MATERIALS AND METHODS: Thirty-five patients were enrolled in this phase II study (12 in chronic phase, 17 in accelerated phase, and six in blastic phase). Decitabine was administered at 15 mg/m2 intravenously over 1 hour daily, 5 days a week for 2 weeks. DNA methylation was measured using a LINE1 bisulfite/pyrosequencing assay. RESULTS: Complete hematologic responses were seen in 12 patients (34%) and partial hematologic responses in seven patients (20%), for an overall hematologic response rate of 54% (83% in chronic phase, 41% in accelerated phase, and 34% in blastic phase). Major cytogenetic responses were observed in six patients (17%), and minor cytogenetic responses were seen in 10 patients (29%) for an overall cytogenetic response rate of 46%. Median response duration was 3.5 months (range, 2 to 13+ months). Myelosuppression was the major adverse effect, with neutropenic fever in 28 (23%) of 124 courses of therapy. LINE1 methylation decreased from 71.3% +/- 1.4% (mean +/- standard error of the mean) to 60.7% +/- 1.4% after 1 week, 50.9% +/- 2.4% after 2 weeks, and returned to 66.5% +/- 2.7% at recovery of counts (median, 46 days). LINE1 methylation at the end of week 1 did not correlate with subsequent responses. However, at day 12, the absolute decrease in methylation was 14.5% +/- 3.0% versus 26.8% +/- 2.7% in responders versus nonresponders (P = .007). CONCLUSION: Decitabine induces hypomethylation and has clinical activity in imatinib refractory chronic myelogenous leukemia. We hypothesize that the inverse correlation between hypomethylation 2 weeks after therapy and response is due to a cell death mechanism of response, whereby resistant cells can withstand more hypomethylation.     

Phase I study of cloretazine (VNP40101M), a novel sulfonylhydrazine alkylating agent, combined with cytarabine in patients with refractory leukemia.

PURPOSE: Cloretazine (VNP40101M) is a novel sulfonylhydrazine alkylating agent with significant antileukemia activity. A phase I study of cloretazine combined with cytarabine (1-beta-d-arabinofuranosylcytosine, ara-C) was conducted in patients with refractory disease. DESIGN: Ara-C was given i.v. at a fixed dose of 1.5 gm/m(2)/d by continuous infusion for 4 days (patients ages <65 years at time of diagnosis) or 3 days (patients ages > or =65 years). Cloretazine was given i.v. over 15 to 60 minutes on day 2 at a starting dose of 200 mg/m(2), with escalation in 100 mg/m(2) increments in cohorts of three to six patients until a maximum tolerated dose was established. The DNA repair enzyme O(6)-alkylguanine DNA alkyltransferase (AGT) was measured at baseline. RESULTS: Forty patients, including 32 with acute myeloid leukemia, received 47 courses of treatment. Complete responses were seen at cloretazine dose levels of > or =400 mg/m(2) in 10 of 37 (27%) evaluable patients, and in this patient subset, AGT activity was significantly lower in patients that responded to treatment than in patients who did not (P < or = 0.027). Dose-limiting toxicities (gastrointestinal and myelosuppression) were seen with 500 and 600 mg/m(2) of cloretazine combined with the 4-day ara-C schedule but not seen with the 3-day schedule. CONCLUSION: The recommended cloretazine dose schedule for future studies is 600 mg/m(2) combined with 1.5 gm/m(2)/d continuous infusion of ara-C for 3 days. The cloretazine and ara-C regimen has significant antileukemic activity. AGT activity may be a predictor of response to cloretazine.     

Prediction of early (4-week) mortality in acute myeloid leukemia with intensive chemotherapy

The progress with intensive chemotherapy and supportive care measures has improved survival in patients with newly diagnosed acute myeloid leukemia (AML). Given the recent development of effective low intensity therapies, an optimal decision on the therapy intensity may improve survival through the avoidance of early mortality. We reviewed the outcome of 3728 patients with newly diagnosed AML who received intensive chemotherapy between August 1980 and May 2020. Intensive chemotherapy was defined as a cumulative cytarabine dose ≥ 700 mg/m² during induction therapy. We divided the whole cohort into a training and validation group at a 3:1 ratio. The population was divided into a training (2790 patients) and a validation cohort (938 patients). The median age was 55 years (range, 15-99). Among them, 442 patients (12%) had core-binding factor AML. Binary logistic regression identified older age, worse performance status, hyperbilirubinemia, elevated creatinine, hyperuricemia, cytogenetic abnormalities other than CBF and -Y, and pneumonia as adverse prognostic factors for an early 4-week mortality. This risk classification for early mortality was verified in the validation cohort of patients. In the validation cohort of more recently treated patients from 2000 to 2017, the 4-week mortality rates with intensive chemotherapy were 2%, 14%, and 50% in the low-, high-, and very high-risk group, respectively. The mortality rates with low intensity therapies were 3%, 9%, and 20%, respectively. The risk classification guides treatment intensity by the assessment of age, frailty, organ dysfunction, cytogenetic abnormality, and infection to avoid early mortality.