Treatment of acute leukaemia with m-AMSA in combination with cytosine arabinoside

Inhibition of cardiac HERG currents by the DNA topoisomerase II inhibitor amsacrine: mode of action

1 The topoisomerase II inhibitor amsacrine is used in the treatment of acute myelogenous leukemia. Although most anticancer drugs are believed not to cause acquired long QT syndrome (LQTS), concerns have been raised by reports of QT interval prolongation, ventricular fibrillation and death associated with amsacrine treatment. Since blockade of cardiac human ether-a-go-go-related gene (HERG) potassium currents is an important cause of acquired LQTS, we investigated the acute effects of amsacrine on cloned HERG channels to determine the electrophysiological basis for its proarrhythmic potential. 2 HERG channels were heterologously expressed in human HEK 293 cells and Xenopus laevis oocytes, and the respective potassium currents were recorded using patch-clamp and two-microelectrode voltage-clamp electrophysiology. 3 Amsacrine blocked HERG currents in HEK 293 cells and Xenopus oocytes in a concentration-dependent manner, with IC50 values of 209.4 nm and 2.0 microm, respectively. 4 HERG channels were primarily blocked in the open and inactivated states, and no additional voltage dependence was observed. Amsacrine caused a negative shift in the voltage dependence of both activation (-7.6 mV) and inactivation (-7.6 mV). HERG current block by amsacrine was not frequency dependent. 5 The S6 domain mutations Y652A and F656A attenuated (Y652A) or abolished (F656A, Y652A/F656A) HERG current blockade, indicating that amsacrine binding requires a common drug receptor within the pore-S6 region. 6 In conclusion, these data demonstrate that the anticancer drug amsacrine is an antagonist of cloned HERG potassium channels, providing a molecular mechanism for the previously reported QTc interval prolongation during clinical administration of amsacrine.

An effective age-unrestricted m-AMSA-based second-line regimen for poor prognosis acute myeloid leukaemia

The efficacy and toxicity of a regimen consisting of amsacrine (m-AMSA), cytarabine, and thioguanine for remission-induction therapy in poor prognosis categories of acute myeloid leukaemia (AML) were determined in a single arm study of 46 patients. The study group consisted of 17 patients with disease refractory to daunorubicin plus cytarabine-based induction regimens, 22 patients with disease which had relapsed during daunorubicin plus cytarabine maintenance therapy, or following completion of this maintenance programme after receiving > or = 500 mg daunorubicin/m2, and 7 previously untreated patients where cardiac disease contraindicated anthracycline therapy. Complete remission (CR) was attained in 46%, and probability of survival was comparable to published results for first-line treatment with daunorubicin plus cytarabine regimens. There was no statistically significant difference in CR rate or probability of survival between these three categories of poor prognosis AML, and cardiotoxic complications were uncommon despite extensive anthracycline exposure in the majority. In the 43% of patients who were 60-76 years of age, there was no statistically significant difference in CR rate or probability of survival relative to patients < 60 years. This observation fails to support the view that less myelotoxic regimens with lesser efficacy should be the basic approach to treatment of AML in patients > or = 60 years of age.

Induction of hypomagnesemia during Amsacrine treatment

Serious cardiac arrhythmias and QT interval prolongation have been reported following Amsacrine chemotherapy. The underlying mechanism is unknown. In this study, electrolyte and electrocardiographic parameters were prospectively studied in patients with acute myeloid leukemia (AML) treated with an Amsacrine containing combination chemotherapy regime. Data were collected immediately before and at 20 (+20) and 90 (+90) min after commencement of Amsacrine administration. Sixteen episodes were studied in six consecutive patients over a continuous 9 month period. One patient developed asymptomatic ventricular tachycardia during administration. Results from +20 and +90 min were compared with baseline by Wilcoxon matched pairs test. There was no significant change in potassium, albumin, or ionized calcium concentration at +20 or +90 min. The magnesium concentration at +20 min was significantly reduced (mean -0.04 mmol/liter; P < 0.05) but not so at +90 min. Sodium concentration at +20 min was significantly reduced (mean - 1.9 mmol/liter; P < 0.01). Electrocardiographic analysis showed no significant alteration in PR interval or QRS duration. Heart rate fell significantly from baseline, mean change -10 and -8 min-1 at +20 and +90 min, respectively (P < 0.01 for both). Corrected QT interval (QTc) was significantly prolonged at +20 min (+0.05) and +90 min (+0.05) (P = 0.0001 and P < 0.0001, respectively). This study confirms the high incidence of QTc prolongation with Amsacrine administration and suggests that transient hypomagnesemia may contribute to the risk of cardiac arrhythmia in this setting.

Therapy of acute myelogenous leukemia

Treatment of acute myelogenous leukemia (AML) is divided into remission induction and post-remission therapy. Remission induction is usually with cytarabine and an anthracycline. Daunorubicin is commonly used but recent data suggest idarubicin or mitoxantrone are equally effective, possibly better. High-dose cytarabine has also been used for remission induction but is not proven superior. Post-remission treatment is typically with two or more courses of drugs similar to those used for remission induction. Other studies use non-cross resistant drugs and/or high-dose cytarabine. Although some data favor use of high-dose cytarabine, no approach is clearly superior. There is considerable controversy whether persons in first remission and with an HLA-identical sibling should receive a bone marrow transplant immediately or after relapse. Although transplant results appear superior, especially in persons less than 20 years of age, the most effective strategy may be reserving transplants for persons failing chemotherapy. This strategy also applies to persons receiving autologous transplants or transplants from alternative donors, like HLA-matched related or unrelated persons.

Neutropenic enterocolitis following treatment with cytosine arabinoside-containing regimens for hematological malignancies: a potentiating role for amsacrine

A retrospective clinical study was performed to determine the clinical impact of neutropenic enterocolitis (NE) in adult patients with acute leukemia and non-Hodgkin's lymphoma treated with cytosine arabinoside (Ara-C)-containing regimens. The diagnosis of NE was restricted to conditions with clinical signs of peritonitis, ileus, or intestinal hemorrhage. Forty episodes of NE were noted during 461 Ara-C-containing courses (8.6%) in 36 of 211 patients (17%) over a 6-year period. Clinically, 18 cases of ileus, 16 cases of peritonitis, and 6 cases of intestinal hemorrhage were recognized as the most important presentation of NE. NE started about 2 weeks after the initiation of the chemotherapy and lasted for an average of 1 week. All patients had a profound neutropenia. The incidence of septicemia was higher during courses complicated by NE (p less than 0.001). All cases of NE were treated with conservative measures. The mortality was 22.5% and represented one third of all therapy-related deaths during the pancytopenic period. The incidence of NE was significantly higher in courses consisting of high-dose Ara-C for 6 consecutive days when the drug was combined with amsacrine for 3 consecutive days (p less than 0.0001).

Chromatographic analysis of anticancer drugs

The present review on the methods for the analysis of anticancer drugs should be seen as an addition to the excellent work of Eksborg and Ehrsson published half a decade ago in this journal (Vol. 340, p.31). The style and format have been followed closely, with the focus again on chromatographic techniques. We felt it important to add a list of compound (group) structures as a service to the reader. Methods have been reviewed for alkylating agents, platinum compounds, antitumour antibiotics, antimetabolites, alkaloids, suramin, 1-hydroxy-3-amino-propylidene-1,1-bisphosphonate and tamoxifen.

Acute myeloid leukemia in elderly adults

One hundred and fifteen previously untreated adults aged over 60 years were referred to St Bartholomew's Hospital between 1978 and 1986 for management of acute myeloid leukemia (AML). Twenty-seven patients received symptomatic or palliative treatment only because combination chemotherapy was considered inappropriate. Eighty-eight patients received intensive chemotherapy with curative intent. There was a 48 per cent 'early death' rate and a 24 per cent incidence of resistant disease; complete remission (CR) was achieved in 25/88 patients (28 per cent). By multivariate analysis, a blast count less than 50 x 10(9)/l at presentation was the only factor predictive for achievement of CR whilst the latter and a presentation blast count less than 50 x 10(9)/l predicted for superior survival. Treatment was often curtailed on account of unacceptable toxicity; only 2/88 patients received the planned six cycles of treatment. Two patients died in CR. Four patients are alive in first CR at 3-9 years from treatment; one is alive in second CR following meningeal relapse. Overall survival was significantly worse than that of a contemporaneous group of adults aged 15-59 years treated at this hospital, but duration of CR was comparable. There are great difficulties involved in the intensive treatment of AML in elderly adults, but the major survival benefit gained by achieving CR should stimulate the search for better tolerated but still curative regimens.

Chemotherapy for relapsed and resistant acute nonlymphoblastic leukemia. Effect of ATA, an amsacrine-containing regime

Twenty-nine evaluable patients with acute nonlymphoblastic leukemia (ANLL), either in relapse or resistant to initial induction therapy (ara C, daunorubicin + etoposide), received the ATA regime consisting of 100 mg/m2 per day Ara C by i.v. infusion for 4-5 days, 100 mg/m2 per day thioguanine orally for 4-5 days, and 100 mg/m2 per day amsacrine i.v. for 2-5 days. Each patient received 1-6 courses (median, 2) of the regime. There were 7 (24%) complete responders, and their duration of responses were 2, 2, 2, 5, 9+, 19, and 24+ months. The complete remission (CR) rate of patients who had a previous CR beyond 6 months (6/13, 46%) was significantly better (X2 = 4.25, p less than 0.05) than that of those who had previously relapsed within 6 months or were refractory to primary induction chemotherapy (1/16, 6%). The two groups of patients had similar patterns of treatment failure. Myelosuppression was the major toxic side effect, and nonhematological toxicities were mild and acceptable.

Determination of amsacrine in human nucleated hematopoietic cells

A new method has been developed for the determination of amsacrine (AMSA) in human nucleated hematopoietic cells. In order to prevent efflux during the cell separation procedure, white blood cells (WBCs) were separated from red blood cells by dextran sedimentation, leaving the WBCs in their natural environment. After cell counting, pelletting the cell suspension and correcting for the admixture of supernatant, AMSA was extracted from the WBCs and determined by high-performance liquid chromatography. Linearity of extraction was observed up to 40.10(6) cells. The inter-assay variation was 4.7%. Plasma and cellular concentrations were measured in five patients at the end of a 3-h infusion of 100 mg/m2 AMSA. A pharmacokinetic study of plasma and cellular AMSA concentrations up to 19 h after infusion was carried out. AMSA concentrations in WBCs correlated well with the plasma levels (n = 20, r = 0.967) with an accumulation factor compared to the plasma concentration of 2.6-9.8 in the patients studied. The method described is useful for studying cellular pharmacokinetics of AMSA in man.