sdz-psc-833 and Leukemia--Myeloid--Acute

Topics: ADP-ribosyl Cyclase 1; Antigens, CD34; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biological Transport; Bone Marrow Cells; Cyclosporins; Drug Resistance, Multiple; Gene Expression Profiling; Hematopoietic Stem Cells; Humans; Leukemia, Myeloid, Acute; Mitoxantrone; Reverse Transcriptase Polymerase Chain Reaction; Verapamil

Valspodar (PSC-833) is a derivative of cyclosporin but devoid of the immunosuppressive and nephrotoxic properties seen in cyclosporin A. It exhibited high affinity binding to Mdr1 P-glycoprotein (P-gp) and demonstrated multidrug resistance-reversing activity superior to cyclosporin A and verapamil both in vitro and in vivo. Preclinical and phase I/II clinical data have indicated that plasma levels of PSC-833 with multidrug resistance-reversing activities are achievable. Potent inhibition of intestinal, hepatobiliary and blood-brain barrier P-gp function has been demonstrated. Since valspodar is also a substrate of cytochrome P450 3A (CYP3A), dual interactions of this compound with P-gp and CYP3A are the basis for the pharmacokinetic interactions seen in preclinical and clinical studies. A new formulation of the drug has recently been developed with better oral bioavailability (60%) and less interindividual variability. The toxicity profiles of valspodar are acceptable and dose-limited by transient and reversible cerebellar ataxia. It has shown multidrug resistance-modulating activities towards acute myeloid leukemia, multiple myeloma and ovarian cancer in phase I/II clinical trials. Phase III studies with respect to these three diseases are ongoing.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Biotechnology; Cyclosporins; Drug Resistance, Multiple; Female; Humans; Leukemia, Myeloid, Acute; Multiple Myeloma; Ovarian Neoplasms

Expression of the multidrug resistance (MDR) phenotype is an independent prognostic variable in acute myeloid leukemia. Approximately 43-57% of the patients have P-glycoprotein (P-gp) expression. A major drawback with the interpretation of P-gp data in AML is the lack of coherence with different analytical assays. We have focused our efforts of P-gp detection on flow cytometry using a dual technique of P-gp staining with antibodies for the extracellular epitope (MRK16) and a functional analysis of P-gp using the rhodamine efflux assay and the effect of P-gp inhibitors such as SDZ PSC 833. This technique was combined with the staining of lineage-specific antigens such as CD34, CD56 and c-kit. In this way, various subsets of AML cells can be identified such as MRK 16+/-, CD34+/- blasts. These cells can be sorted for further analysis, such as the molecular expression of P-gp and other pleiotropic drug resistance genes.

Topics: Antigens, CD34; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporins; Flow Cytometry; Fluorescence; Humans; Immunohistochemistry; Leukemia, Myeloid, Acute; RNA

Recombinant interleukin-2 (rIL-2) induces cellular cytotoxicity against leukemia blasts. Patients with acute myeloid leukemia (AML) in first complete remission (CR) may harbor minimal residual disease that is susceptible to rIL-2-activated effector cells.. In the Cancer and Leukemia Group B (CALGB) 19808 study, patients with AML in first CR were randomly assigned after all planned chemotherapy to receive a 90-day course of subcutaneously administered rIL-2 or no further therapy. The primary objective was to compare disease-free survival (DFS) between the 2 treatment arms. A total of 534 patients achieved a CR, 214 of whom were randomized. Six courses of low-dose daily rIL-2 were given for the expansion of cytotoxic effector cells, each followed by 3-day high-dose boluses given to trigger cytotoxicity against minimal residual disease.. On the protocol-specified intention-to-treat analysis, the hazards ratio for DFS was 0.75 (95% confidence interval, 0.52-1.09; P = .13); the 5-year DFS rate was 42% in the observation arm and 53% in the rIL-2 treatment arm. The hazards ratio for overall survival (OS) was 0.88 (95% confidence interval, 0.54-1.23; P = .34); the 5-year OS rate was 58% for the observation arm and 63% for the rIL-2 treatment arm. Twenty-five of the 107 patients randomized to treatment with rIL-2 either refused or were unable to initiate therapy and 30 patients did not complete their assigned therapy. However, significant toxicities were not commonly observed. The trial design did not anticipate the difficulties patients would encounter with protocol compliance.. The efficacy of immunotherapy with rIL-2 administered after intensive postremission treatment was not assessed as planned because of unexpected refusals by patients and/or their physicians to comply with protocol-directed therapy. Neither DFS nor OS was found to be significantly improved.

Topics: Age Factors; Antineoplastic Combined Chemotherapy Protocols; Cyclosporins; Cytarabine; Daunorubicin; Disease-Free Survival; Etoposide; Female; Humans; Interleukin-2; Leukemia, Myeloid, Acute; Male; Middle Aged; Recombinant Proteins; Remission Induction; Survival Rate; Treatment Outcome

Valspodar, a non-immunosuppressive analog of cylosporine, is a potent P-glycoprotein (MDR1) inhibitor. As MDR1-mediated efflux of chemotherapeutic agents from leukemic blasts may contribute to drug resistance, a phase 1 study of valspodar combined with mitoxantrone and etoposide in pediatric patients with relapsed or refractory leukemias was performed.. Patients received a valspodar-loading dose (2 mg/kg) followed by a 5-day continuous valspodar infusion (8, 10, 12.5, or 15 mg/kg/day) combined with lower than standard doses of mitoxantrone and etoposide. The valspodar dose was escalated using a standard 3 + 3 phase I design.. Twenty-one patients were evaluable for toxicity and 20 for response. The maximum tolerated dose (MTD) of valspodar was 12.5 mg/kg/day, combined with 50% dose-reduced mitoxantrone and etoposide. The clearance of mitoxantrone and etoposide was decreased by 64% and 60%, respectively, when combined with valspodar. Dose-limiting toxicities included stomatitis, ataxia, and bone marrow aplasia. Three of 11 patients with acute lymphoblastic leukemia (ALL) had complete responses while no patient with acute myeloid leukemia (AML) had an objective response. In vitro studies demonstrated P-glycoprotein expression on the blasts of 5 of 14 patients, although only 1 had inhibition of rhodamine efflux by valspodar.. While this regimen was tolerable, responses in this heavily pretreated population were limited to a subset of patients with ALL.

Topics: Adolescent; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Child; Child, Preschool; Cyclosporins; Drug Resistance, Multiple; Drug-Related Side Effects and Adverse Reactions; Etoposide; Female; Humans; Leukemia, Myeloid, Acute; Male; Maximum Tolerated Dose; Mitoxantrone; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Recurrence; Salvage Therapy; Young Adult

Cancer and Leukemia Group B 19808 (CALGB 19808) is the only randomized trial of a second-generation P-glycoprotein (Pgp) modulator in untreated patients with acute myeloid leukemia (AML) younger than age 60 years. We randomly assigned 302 patients to receive induction chemotherapy regimens consisting of cytosine arabinoside (Ara-C; A), daunorubicin (D), and etoposide (E), without (ADE) or with (ADEP) PSC-833 (P). The incidence of complete remission was 75% with both regimens. Reversible grade 3 and 4 liver and mucosal toxicities were significantly more common with ADEP. Therapy-related mortality was 7% and did not differ by induction arm. Excess cardiotoxicity was not seen with high doses of D in ADE. The median disease-free survival was 1.34 years in the ADE arm and 1.09 years in the ADEP arm (P = .74, log-rank test); the median overall survival was 1.86 years in the ADE arm and 1.69 years in the ADEP arm (P = .82). There was no evidence of a treatment difference within any identifiable patient subgroup. Inhibition of Pgp-mediated drug efflux by PSC-833 did not improve clinical outcomes in younger patients with untreated AML. This trial was registered at www.clinicaltrials.gov as #NCT00006363.

Topics: Adolescent; Adult; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporins; Cytarabine; Daunorubicin; Etoposide; Female; Humans; Leukemia, Myeloid, Acute; Male; Middle Aged; Remission Induction; Survival Rate; Treatment Outcome; Young Adult

The acute myeloid leukaemia (AML)14 trial addressed four therapeutic questions in patients predominantly aged over 60 years with AML and High Risk Myelodysplastic Syndrome: (i) Daunorubicin 50 mg/m(2) vs. 35 mg/m(2); (ii) Cytarabine 200 mg/m(2) vs. 400 mg/m(2) in two courses of DA induction; (iii) for part of the trial, patients allocated Daunorubicin 35 mg/m(2) were also randomized to receive, or not, the multidrug resistance modulator PSC-833 in a 1:1:1 randomization; and (iv) a total of three versus four courses of treatment. A total of 1273 patients were recruited. The response rate was 62% (complete remission 54%, complete remission without platelet/neutrophil recovery 8%); 5-year survival was 12%. No benefits were observed in either dose escalation randomization, or from a fourth course of treatment. There was a trend for inferior response in the PSC-833 arm due to deaths in induction. Multivariable analysis identified cytogenetics, presenting white blood count, age and secondary disease as the main predictors of outcome. Although patients with high Pgp expression and function had worse response and survival, this was not an independent prognostic factor, and was not modified by PSC-833. In conclusion, these four interventions have not improved outcomes in older patients. New agents need to be explored and novel trial designs are required to maximise prospects of achieving timely progress.

Topics: Adult; Age Factors; Aged; Aged, 80 and over; Antineoplastic Combined Chemotherapy Protocols; Cyclosporins; Cytarabine; Cytogenetic Analysis; Daunorubicin; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Female; Humans; Leukemia, Myeloid, Acute; Leukocyte Count; Male; Middle Aged; Multivariate Analysis; Myelodysplastic Syndromes; Prognosis; Remission Induction; Survival Rate

To determine whether MDR1 reversal by the addition of the P-glycoprotein (P-gp) inhibitor PSC-833 to standard induction chemotherapy would improve event-free survival (EFS), 419 untreated patients with acute myeloid leukemia (AML) aged 60 years and older were randomized to receive 2 induction cycles of daunorubicin and cytarabine with or without PSC-833. Patients in complete remission were then given 1 consolidation cycle without PSC-833. Neither complete response (CR) rate (54% versus 48%; P = .22), 5-year EFS (7% versus 8%; P = .53), disease-free survival (DFS; 13% versus 17%; P = .06) nor overall survival (OS; 10% in both arms; P = .52) were significantly improved in the PSC-833 arm. An integrated P-gp score (IPS) was determined based on P-gp function and P-gp expression in AML cells obtained prior to treatment. A higher IPS was associated with a significantly lower CR rate and worse EFS and OS. There was no significant interaction between IPS and treatment arm with respect to CR rate and survival, indicating also a lack of benefit of PSC-833 in P-gp-positive patients. The role of strategies aimed at inhibitory P-gp and other drug-resistance mechanisms continues to be defined in the treatment of patients with AML.

Topics: Aged; Aged, 80 and over; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporins; Cytarabine; Daunorubicin; Drug Therapy, Combination; Female; Follow-Up Studies; Humans; Leukemia, Myeloid, Acute; Male; Middle Aged; Survival Rate; Treatment Outcome

The Cancer and Leukemia Group B conducted a phase 3 trial of the P-glycoprotein modulator PSC-833 in untreated acute myeloid leukemia patients aged 60 years and older. Patients were randomized to 1 of 2 regimens, with doses determined in a prior phase 1 study, consisting of cytarabine 100 mg/m(2)/d by 7-day infusion, with daunorubicin 60 mg/m(2) and etoposide 100 mg/m(2) daily for 3 days (ADE), or daunorubicin 40 mg/m(2) and etoposide 60 mg/m(2) for 3 days with PSC-833, 2.8 mg/kg over 2 hours, and then 10 mg/kg/d by 3-day infusion (ADEP). The ADEP arm was closed after randomization of 120 patients (61 to ADE and 59 to ADEP) because of excessive early mortality. Rates of complete remission, nonresponse, and death were 46%, 34%, and 20% for ADE, versus 39%, 17%, and 44% for ADEP (P =.008). Nevertheless, disease-free survival (median 7 vs 8 months; P =.38) and overall survival (approximately 33% alive at 1 year) did not differ and were similar to historical results. Although the number of patients was limited, ADE patients whose pretreatment cells exhibited PSC-833-modulated dye efflux in vitro (n = 22) had worse outcomes than those without efflux (n = 11) (complete remission, nonresponse, and death rates of 41%, 41%, and 18%, compared with 91%, 9%, and 0%; P =.03), but with ADEP outcomes were nearly identical. Moreover, for patients with PSC-833-modulated efflux, median disease-free survival was 5 months with ADE and 14 months with ADEP (P =.07). Further modulation trials in older patients must await the design of less-toxic regimens.

Topics: Aged; Aged, 80 and over; Antineoplastic Combined Chemotherapy Protocols; Cyclosporins; Cytarabine; Daunorubicin; Disease-Free Survival; Drug Resistance, Multiple; Etoposide; Female; Humans; Leukemia, Myeloid, Acute; Logistic Models; Male; Middle Aged; Remission Induction

PSC 833 (Valspodar) can reverse multidrug resistance (MDR) in patients with hematologic malignancies, but alters the pharmacokinetics of concomitant anticancer agents. A phase I, dose-finding study was initiated to define a safe and effective regimen of mitoxantrone, etoposide, and cytarabine (MEC) when administered with PSC 833 to patients with early relapsed or refractory acute myeloid leukemia (AML). Poor-prognosis AML patients refractory to first-line induction therapy or relapsing within 9 months of attaining complete remission (CR) were treated with cytarabine (1.0 g/m2/day), etoposide (30 mg/m2/day), and mitoxantrone at a dose of either 3.0 mg/m2/day (cohort 1) or 4.5 mg/m2/day (cohorts 2 and 3) for 6 days plus continuous-infusion PSC 833 (10 mg/kg/24 h with a 2.0 mg/kg loading dose) for 6 or 7 days each 21-day cycle. Patients achieving CR were given a 4-day MEC plus PSC 833 consolidation cycle. Twenty-three patients were enrolled (eight with primary refractory AML and 15 in relapse). Dose-limiting toxicity occurred in one of six patients in cohort 2 (grade 4 mucositis) and one of seven patients in cohort 3 (grade 4 hyperbilirubinemia). The maximum tolerated dose of mitoxantrone was defined as 4.5 mg/m2/day. Clinically significant grade 4 hyperbilirubinemia, possibly related to PSC 833, occurred in four patients. Hematologic toxicities were as expected in this patient population, but were not dose limiting. Mild to moderate cerebellar ataxia and paresthesia occurred in six (26%) and five (22%) patients, respectively, but were not dose limiting. Overall, six of 23 (26%) patients achieved CR, including five patients with demonstrated P-glycoprotein expression and/or function. The median overall survival was 4 months. All six patients with a CR were alive and four (17%) patients were disease free at 12 months. Blood levels of PSC 833 were well above the target level of 1000 ng/ml, a concentration that is known to reverse MDR in vitro. PSC 833 reduced the clearance of etoposide by approximately two-fold. No correlation was observed between the mitoxantrone or etoposide area under the curve and response. In conclusion, the MEC plus PSC 833 tested regimen was well tolerated and the 26% CR rate warrants further testing of this regimen in a randomized, phase III trial.

Topics: Adolescent; Adult; Aged; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporins; Cytarabine; Drug Resistance, Multiple; Etoposide; Female; Humans; Leukemia, Myeloid, Acute; Male; Middle Aged; Mitoxantrone

The aim of the present study was to evaluate the effect of the cyclosporine derivative valspodar (PSC 833; Amdray, Novartis Pharma, Basel, Switzerland) on the concentration of daunorubicin (dnr) in leukemic blast cells in vivo during treatment.. Ten patients with acute myeloid leukemia (AML) were included. Leukemic cells from seven of the patients were P-glycoprotein (Pgp)-positive. dnr 100 mg/m(2) was given as a continuous infusion over 72 hours. After 24 hours, a loading dose of valspodar was given, followed by a 36-hour infusion of 10 mg/kg per 24 hours. Blood samples were drawn at regular intervals, and concentrations of dnr and its main metabolite, daunorubicinol, in plasma and isolated leukemic cells were determined by high-pressure liquid chromatography.. The mean dnr concentrations in leukemic cells 24 hours after the start of infusion (before valspodar) were 18.8 micromol/L in Pgp-negative samples and 13.5 micromol/L in Pgp-positive samples. After 8 hours of valspodar infusion, these values were 25.8 and 24.0 micromol/L, respectively. The effect of valspodar was evaluated from the ratio of the area under the curve (AUC) for dnr concentration versus time in leukemic cells to the AUC for dnr concentration against time in the plasma. For the seven patients with Pgp-positive leukemia, the mean ratio increased by 52%, from 545 on day 1 to 830 on day 2 (P<.05) when valspodar was given. In the three patients with Pgp-negative leukemia, no significant difference was observed.. These results strongly suggest that valspodar, by interacting with Pgp, can increase the cellular uptake of dnr in leukemic blasts in vivo.

Topics: Aged; Aged, 80 and over; Antibiotics, Antineoplastic; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporins; Daunorubicin; Dose-Response Relationship, Drug; Drug Interactions; Female; Humans; Leukemia, Myeloid, Acute; Male; Middle Aged

Valspodar (PSC-833) is a derivative of cyclosporin but devoid of the immunosuppressive and nephrotoxic properties seen in cyclosporin A. It exhibited high affinity binding to Mdr1 P-glycoprotein (P-gp) and demonstrated multidrug resistance-reversing activity superior to cyclosporin A and verapamil both in vitro and in vivo. Preclinical and phase I/II clinical data have indicated that plasma levels of PSC-833 with multidrug resistance-reversing activities are achievable. Potent inhibition of intestinal, hepatobiliary and blood-brain barrier P-gp function has been demonstrated. Since valspodar is also a substrate of cytochrome P450 3A (CYP3A), dual interactions of this compound with P-gp and CYP3A are the basis for the pharmacokinetic interactions seen in preclinical and clinical studies. A new formulation of the drug has recently been developed with better oral bioavailability (60%) and less interindividual variability. The toxicity profiles of valspodar are acceptable and dose-limited by transient and reversible cerebellar ataxia. It has shown multidrug resistance-modulating activities towards acute myeloid leukemia, multiple myeloma and ovarian cancer in phase I/II clinical trials. Phase III studies with respect to these three diseases are ongoing.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Biotechnology; Cyclosporins; Drug Resistance, Multiple; Female; Humans; Leukemia, Myeloid, Acute; Multiple Myeloma; Ovarian Neoplasms

The failure of convenional chemotherapy in relapsed or refractory and other poor risk AML patients has been linked to expression of the multidrug resistance gene (mdr 1) product P-glycoprotein (P-gp). PSC 833 is a non-competitive inhibitor of P-gp and has been shown in vitro and in vivo to restore sensitivity of resistant tumor cells to anticancer drugs (ACDs). Induction chemotherapy consisting of cytarabine (C) in combination with PSC 833 and escalating doses of mitoxantrone (M) and etoposide (E) over 5 or 6 days were tested in two phase I/II studies in poor prognosis AML. Overall, 59 patients were evaluated: their age ranged between 18 and 70 years. Fourteen patients had primary refractory disease, 25 had relapsed within 9 months from first complete remission (CR), 5 were in second relapse, 10 had secondary AML, and 4 had relapsed post-bone marrow transplantation. PSC 833 was given as a constant i.v. infusion at a rate of 10 mg/kg/24 h for 5 or 6 days, depending on the duration of chemotherapy. In both studies a loading dose of 2 mg/kg of PSC 833 was given on day 1. In the 5-day regimen, the final study doses of the cytotoxic agents were C 1 g/m2/d, M 4.0 mg/m2/d, and E 40 mg/m2/d. In the 6-day regimen, the final study doses of the cytotoxic agents were C 1 g/m2/d, M 4.5 mg/m2/d and E 30 mg/m2/d. The combined efficacy results of both studies indicate that PSC-MEC is active in all treatment indications, complete remission being achieved in 2/5 (40%) second relapses, 8/25 (32%) early relapses, 3/10 (30%) secondary AML, 3/15 (20%) refractory patients and 1/4 (25%) post-BMT relapses. Based on historical controls, this observed overall CR rate (29%) is higher than expected in this high risk patient population. Our data indicate that, in refractory/relapsed AML patients, PSC-MEC regimens had encouraging antileukemic effects, is well tolerated, and has led to Phase III trials in this setting.

Topics: Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporins; Cytarabine; Etoposide; Genes, MDR; Humans; Leukemia, Myeloid, Acute; Mitoxantrone; Prognosis; Remission Induction; Salvage Therapy

Expression of the multidrug resistance gene (MDR1) p170 protein is frequent in leukemic blasts from patients with relapsed acute myelogenous leukemia (AML). A phase I study using the nonimmunosuppressive MDR1 blocker SDZ PSC-833 (PSC) in combination with mitoxantrone (MITO) and etoposide (VP) was performed.. Starting doses (LVL0) of MITO (3.25 mg/m2/d on days 1 and 3 to 6) and VP (210 mg/m2/d on days 1 and 3 to 5) were 40% of the maximal-tolerated dose (MTD) from a prior study. A 1.5-mg/kg loading dose of PSC was followed by a 120-hour continuous infusion of 10 mg/kg/d on days 2 to 6. Blood samples for PSC, MITO, and VP pharmacokinetics (PK) were taken on days 1 and 3, and samples for MDR1 expression were taken on day 0.. Severe mucositis developed in all patients at LVL0; therefore, MITO and VP doses were reduced to 2.5 and 170 mg/m2 (LVL-1) for the next seven patients, and this dose proved to be MTD. All LVL0 and three LVL-1 patients had transient elevations in the serum bilirubin level to > or = 4 mg/dL. Serum creatinine level increased to greater than 2 mg/dL in one case. There were no other grade 3 or 4 nonhematologic toxicities observed. The peripheral blood was cleared of leukemia in three LVL0 and four LVL-1 patients. The marrow was cleared of leukemic cells in one LVL0 and five LVL-1 patients, and a significant reduction in marrow leukemic infiltrate was observed in eight of 10. No patient achieved complete remission (CR), and all died of progressive disease (n = 8) or infection (n = 2). MDR1 expression was detected by fluorescent-activated cell sorter (FACS) analysis in five of seven cases. An elevated MDR1 mRNA level was detected by quantitative polymerase chain reaction (Q-PCR) in six of eight cases studied. Clearing of leukemia cells from the marrow occurred in four of six MDR1-positive and one of three MDR1-negative patients. Despite the fact that LVL0 doses had to be reduced due to toxicity, coadministration of PSC did not produce a consistent effect on MITO PK; however, it did repeatedly lead to increased levels of VP in the serum.. We conclude that PSC-MITO-VP is a tolerable regimen with antileukemic activity. Addition of PSC necessitated a 66% reduction in MITO and VP doses from a prior study without PSC.

Topics: Antineoplastic Combined Chemotherapy Protocols; Cyclosporins; Drug Resistance, Neoplasm; Etoposide; Genes, MDR; Humans; Leukemia, Myeloid, Acute; Mitoxantrone; Recurrence

Background Crenolanib (crenolanib besylate, 4-piperidinamine, 1-[2-[5-[(3-methyl-3-oxetanyl)methoxy]-1H-benzimidazol-1-yl]-8-quinolinyl]-, monobenzenesulfonate) is a potent and specific type I inhibitor of fms-like tyrosine kinase 3 (FLT3) that targets the active kinase conformation and is effective against FLT3 with internal tandem duplication (ITD) with point mutations induced by, and conferring resistance to, type II FLT3 inhibitors in acute myeloid leukemia (AML) cells. Crenolanib is also an inhibitor of platelet-derived growth factor receptor alpha and beta and is in clinical trials in both gastrointestinal stromal tumors and gliomas. Methods We tested crenolanib interactions with the multidrug resistance-associated ATP-binding cassette proteins ABCB1 (P-glycoprotein), ABCG2 (breast cancer resistance protein) and ABCC1 (multidrug resistance-associated protein 1), which are expressed on AML cells and other cancer cells and are important components of the blood-brain barrier. Results We found that crenolanib is a substrate of ABCB1, as evidenced by approximate five-fold resistance of ABCB1-overexpressing cells to crenolanib, reversal of this resistance by the ABCB1-specific inhibitor PSC-833 and stimulation of ABCB1 ATPase activity by crenolanib. In contrast, crenolanib was not a substrate of ABCG2 or ABCC1. Additionally, it did not inhibit substrate transport by ABCB1, ABCG2 or ABCC1, at pharmacologically relevant concentrations. Finally, incubation of the FLT3-ITD AML cell lines MV4-11 and MOLM-14 with crenolanib at a pharmacologically relevant concentration of 500 nM did not induce upregulation of ABCB1 cell surface expression. Conclusions Thus ABCB1 expression confers resistance to crenolanib and likely limits crenolanib penetration of the central nervous system, but crenolanib at therapeutic concentrations should not alter cellular exposure to ABC protein substrate chemotherapy drugs.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; Benzimidazoles; Biological Transport; Blood-Brain Barrier; Cyclosporins; Drug Resistance, Neoplasm; fms-Like Tyrosine Kinase 3; Leukemia, Myeloid, Acute; Multidrug Resistance-Associated Proteins; Neoplasm Proteins; Piperidines; Platelet-Derived Growth Factor; Tumor Cells, Cultured

Topics: Aged; Aged, 80 and over; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; Cyclosporins; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Enzyme Inhibitors; Female; Humans; Leukemia, Myeloid, Acute; Male; Middle Aged; Naphthalimides; Neoplasm Proteins; Topoisomerase II Inhibitors

Acute myelogenous leukemia (AML) is a disease originating from normal hematopoietic CD34+ CD38- progenitor cells. Modulation of the multidrug ATP-binding cassette transporter ABCB1 has not resulted in improved outcome in AML, raising the question whether leukemic CD34+ CD38- cells are targeted by this strategy.. ABCB1-mediated transport in leukemic CD34+ CD38- cells compared with their normal counterparts was assessed by quantitating the effect of specific ABCB1 modulators (verapamil and PSC-833) on mitoxantrone retention [defined as efflux index (EI), intracellular mitoxantrone fluorescence intensity in the presence/absence of inhibitor].. ABCB1 was the major drug transporter in CD34+ CD38- cells in normal bone marrow (n = 16), as shown by the abrogation of mitoxantrone extrusion by ABCB1 modulators (EI, 1.99 +/- 0.08). Surprisingly, ABCB1-mediated drug extrusion was invariably reduced in CD34+ CD38- cells in AML (n = 15; EI, 1.21 +/- 0.05; P < 0.001), which resulted in increased intracellular mitoxantrone retention in these cells (mitoxantrone fluorescence intensity, 4.54 +/- 0.46 versus 3.08 +/- 0.23; P = 0.004). Active drug extrusion from these cells occurred in the presence of ABCB1 modulators in the majority of samples, pointing in the direction of redundant drug extrusion mechanisms. Residual normal CD34+ CD38- cells could be identified by their conserved ABCB1-mediated extrusion capacity.. ABCB1-mediated drug extrusion is reduced in leukemic CD34+ CD38- progenitor cells compared with their residual normal counterparts. Redundant drug transport mechanisms confer mitoxantrone transport from leukemic progenitors. These data argue that ABCB1 modulation is not an effective strategy to circumvent drug extrusion from primitive leukemic progenitor cells and may preferentially target residual normal progenitors in AML.

Topics: Adolescent; ADP-ribosyl Cyclase 1; Adult; Aged; Antigens, CD34; Antigens, Differentiation; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biological Transport; Bone Marrow Cells; Cyclosporins; Drug Resistance, Multiple; Female; Flow Cytometry; Hematopoietic Stem Cells; Humans; Leukemia, Myeloid, Acute; Male; Middle Aged; Mitoxantrone; Oncogene Proteins, Fusion; Reverse Transcriptase Polymerase Chain Reaction; Verapamil

Topics: Animals; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Carcinoma, Non-Small-Cell Lung; Clinical Trials, Phase III as Topic; Cyclosporins; Dibenzocycloheptenes; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Drugs, Investigational; Gene Expression Regulation, Neoplastic; Humans; Leukemia, Myeloid, Acute; Lung Neoplasms; Membrane Transport Proteins; Multidrug Resistance-Associated Protein 2; Multidrug Resistance-Associated Proteins; National Institutes of Health (U.S.); Neoplasms; Piperidines; Pyridines; Quinolines; United States

P-glycoprotein (pgp), which is the product of the MDR1 (multidrug resistance-1) gene, has an established role as a mediator of cytotoxic drug resistance in acute myeloid leukemia (AML). To study the role of pgp in mediating apoptosis resistance in AML cells deprived of serum and growth factors, apoptosis was quantified by flow cytometry using uptake of the dye 7-amino-actinomycin D (7-AAD) alongside low forward scatter. In pgp+ve primary AML samples, there was a significant increase in apoptosis in the presence of the pgp-specific antibody UIC2 (mean increase: 58%; range: 11%-95%; P <. 05). Likewise, apoptosis in growth factor-deprived TF1 cells cultured for 30 hours increased 2.5-fold in the presence of 25 microg/mL UIC2. The pgp reversal agent PSC-833 (1 micromol/L) augmented in vitro apoptosis by a median of 52% in pgp+ve patient samples and to a comparable degree in 6 pgp-ve samples. To determine whether the sphingomyelin-ceramide (SM-ceramide) pathway of apoptosis occurs in AML blasts in response to cytotoxic drugs, cells were incubated with daunorubicin at the patient-specific IC(30) (the concentration of daunorubicin that caused apoptotic cell death in 30% of cells) in the presence of the ceramide synthase inhibitor fumonisin B1, which inhibited apoptosis by 18%-81% (median: 40%). Exogenous SM failed to augment apoptosis induced by growth factor withdrawal in pgp+ve TF1 cells and was significantly more effective at augmenting apoptosis in pgp-ve patient blasts (median increase in cell death: 33%; range: 19%-88%) than in pgp+ve samples (median: 7%; range: 0%-27%; P =.028). Cellular accumulation of exogenous SM was associated with apoptosis and also occurred in nonapoptotic patient cells treated with PSC-833. However, this effect was not seen following treatment with the UIC2 antibody. These results indicate that pgp is able to exert a protective effect on AML cell viability and that this is associated with a reduced effect of exogenous SM on apoptosis. The pgp reversal agent PSC-833 acts, at least in part, by a pgp independent mechanism to alter SM distribution and to augment apoptosis induced in AML cells by serum and growth factor withdrawal. (Blood. 2000;95:2897-2904)

Topics: Apoptosis; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biological Transport; Blast Crisis; Cell Survival; Ceramides; Cyclosporins; Dactinomycin; Flow Cytometry; Fluorescent Dyes; Genes, MDR; Growth Substances; Humans; Kinetics; Leukemia, Myeloid, Acute; Signal Transduction; Sphingomyelins; Tumor Cells, Cultured; U937 Cells

In order to bring MDR analysis into a clinical setting, reproducible assays with clear cut off points to define MDR positivity must be used. Sensitivity can also be increased by combining the results of more than one assay. We have used a combination of flow cytometric assays to define MDR positive and negative blasts in 47 AML patients entered into MRC trials. Our primary test is a standardised and reproducible assay for anthracycline accumulation in which we use carboxylate microspheres to bind the fluorescent drug daunorubicin (dnr). Cells and beads are incubated concurrently with dnr. Cellular dnr accumulation is quantified as a cell:bead fluorescence ratio. Confirmatory assays for MDR comprise the cyclosporin modulation assay for rhodamine 123 uptake and also measurement of lung resistance protein and multidrug resistance associated protein (with LRP-56 and MRPr1 respectively). 27/47 (57%) samples had both low and accumulation and at least one positive confirmatory test (a modulated functional assay and/or protein overexpression) and were categorised as "confirmed MDR". 15/47 patients (32%) were MDR negative in all 4 assays. 5/47 (11%) patients had unconfirmed low dnr accumulation. None of the patients in this cohort had high dnr accumulation alongside overexpressed LRP or MRP or functional P-glycoprotein. We believe that this approach to MDR analysis enhances the value of the highly reproducible functional assays. The use of a primary and confirmatory tests is also likely to improve specificity.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP-Binding Cassette Transporters; Blast Crisis; Bone Marrow Cells; Cyclosporine; Cyclosporins; Daunorubicin; Drug Resistance, Multiple; Flow Cytometry; Genes, MDR; Humans; Leukemia, Myeloid, Acute; Multidrug Resistance-Associated Proteins; Reproducibility of Results

The newly designed pyridine derivative B9309-068 and a series of structurally different compounds were tested for their ability to modulate rhodamine 123 (RHO) efflux from CD56+ hematopoietic cells in the presence of either 10% fetal calf serum or undiluted human AB serum. Furthermore, efflux modulation was investigated on CD34+ blast populations obtained from four patients with relapsed state AML. Target cells were specified throughout by labeling with peridinine chlorophyll protein (PerCP)-conjugated monoclonal antibodies, allowing clear differentiation from RHO emission spectrum by flow cytometry. In the presence of low serum each compound efficiently modulated RHO efflux without significant differences in the range of final concentrations (1.0-3.0 microM). At 0.1 microM, however, RHO efflux was differentially modulated following the series GF120918 approximately B9309-068 > PSC 833 > DNIG approximately DVER. With CD56+ cells in the presence of undiluted human AB serum at a final modulator concentration of 0.1 microM, all chemosensitizers tested were found to be inefficient. At final concentrations of 0.3 microM or higher, distinct RHO efflux modulation was found with the following efficacies: B9309-068 approximately GF120918 > PSC 833 >> DVER approximately DNIG. The efficacies seen in undiluted human AB serum at 3.0 microM were comparable to those seen on CD56+ cells at final modulator concentrations of 0.1 microM in low serum. Our results identify the pyridine derivative B9309-068 as a promising compound for modulating P-glycoprotein-mediated drug resistance under conditions resembling the clinical setting. Nonetheless, modulation potencies of a series of structurally very different chemosensitizers was revealed to be substantially diminished at high serum concentrations in vitro.

Topics: Acridines; Antigens, CD34; ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP-Binding Cassette Transporters; Blood Proteins; Calcium Channel Blockers; CD56 Antigen; Cyclosporins; Dihydropyridines; Dose-Response Relationship, Drug; Flow Cytometry; Fluorescent Dyes; Gene Expression; Humans; Isoquinolines; Leukemia, Myeloid, Acute; Leukocytes, Mononuclear; Morpholines; Multidrug Resistance-Associated Proteins; Pyrimidines; Rhodamine 123; Rhodamines; Tetrahydroisoquinolines; Verapamil

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporins; Drug Resistance, Multiple; Glycerol; Humans; In Vitro Techniques; Leukemia, Myeloid, Acute; Lymphocytes; Pharmaceutical Vehicles