Uptake and intracellular distribution of amrubicin, a novel 9-amino-anthracycline, and its active metabolite amrubicinol in P388 murine leukemia cells

A comprehensive review on time-tested anticancer drug doxorubicin

Doxorubicin or Adriamycin, is one of the most widely used chemotherapeutic drug for treating a myriad of cancers. It induces cell death through multiple intracellular targets: reactive oxygen species generation, DNA-adduct formation, topoisomerase II inhibition, histone eviction, Ca²⁺ and iron hemostasis regulation, and ceramide overproduction. Moreover, doxorubicin-treated dying cells undergo cellular modifications that enable neighboring dendritic cell activation and enhanced presentation of tumor antigen. In addition, doxorubicin also aids in the immune-mediated clearance of tumor cells. However, the development of chemoresistance and cardiotoxicity side effect has undermined its widespread applicability. Several formulations of doxorubicin and co-treatments with inhibitors, miRNAs, natural compounds and other chemotherapeutic drugs have been essential in reducing its dosage-dependent toxicity and combating the development of resistance. Further, more advanced research into the molecular mechanism of chemoresistance development would be vital in improving the overall survivability of clinical patients and in preventing cancer relapse.

Drug metabolite heterogeneity in cultured single cells profiled by pico-trapping direct mass spectrometry

Aim: We investigated the heterogeneity of tafluprost metabolism in primary human hepatocytes at a single-cell level by live single-cell mass spectrometry (MS). Materials & methods: Picoliter volumes of cytoplasm were analyzed by nano-electrospray ionization MS in order to obtain single-cell metabolite profiles. The subcellular components of a single tafluprost-treated human hepatocyte were isolated and the single-cell metabolite profile was compared with those of traditional bulk hepatocyte analysis. Results: In the bulk hepatocyte analysis, liquid chromatography–MS showed the averaged metabolism of tafluprost to tafluprost acid (TA) and β-oxidized metabolites. However, live single-cell MS showed that tafluprost metabolism varied among individual cells. In addition, there was significant variation in the quantities of TA and a major metabolite, dinor-TA, among cells, whereas there was no significant variation in 7-ethoxycoumarin metabolism. Conclusion: Thus, live single-cell MS successfully detected the heterogeneity of drug metabolism in individual living hepatocytes.

Original submitted 12 May 2011; Revised submitted 6 February 2012; Published online 14 May 2012

Amrubicin for the treatment of neuroendocrine carcinoma of the gastrointestinal tract: a retrospective analysis of five cases

PURPOSE

A standard chemotherapy regimen for neuroendocrine carcinoma of the gastrointestinal tract (GI-NEC) has not been established. Treatment usually consists of platinum doublets, consistent with the standard treatment for small-cell lung cancer (SCLC), with which it shares clinicopathological similarities. Here, we retrospectively examined responses of five GI-NEC patients treated with amrubicin chloride (AMR) which has shown activity against SCLC as salvage therapy.

METHODS

Five patients with histologically proven unresectable GI-NEC in whom previous chemotherapy regimens had failed were treated with AMR, a synthetic anthracycline with potent topoisomerase II inhibition.

RESULTS

Primary tumors were located in the esophagus in three patients, anus in one, and colon in one. AMR was administered intravenously at 35-40 mg/m(2) on days 1-3 every 3 weeks for a median of six treatment cycles (range, 2-8). Although all patients had received one to four previous chemotherapy regimens, including cisplatin doublets, three of five achieved objective responses to AMR. All three had esophageal NEC in relapse following combination treatment with irinotecan plus cisplatin. The most common adverse events of ≥ grade 3 were neutropenia (75%), anemia (60%), thrombocytopenia (20%), and febrile neutropenia (20%).

CONCLUSIONS

Single-agent AMR achieved objective responses in three of five patients with GI-NEC. This compound may be a candidate for prospective evaluation in a larger series.

Over-expression of MDR1 in amrubicinol-resistant lung cancer cells

PURPOSE

Amrubicin, a totally synthetic 9-aminoanthracycline anticancer drug, has shown promising activity for lung cancer, but little is known about the mechanism of resistance for this agent. This study was aimed to clarify the role of P-glycoprotein (P-gp) in amrubicinol, an active metabolite of amrubicin, resistance in lung cancer cells.

METHODS

Amrubicinol-resistant cell line PC-6/AMR-OH was developed by continuously exposing the small-cell lung cancer cell line PC-6 to amrubicinol. Gene expression level of MDR1, which encodes P-gp, and intracellular accumulation of amrubicinol were evaluated by PC-6 and PC-6/AMR-OH cells. The involvement of MDR1 in amrubicinol resistance was evaluated by treatment with P-gp inhibitor verapamil and small interfering RNA (siRNA) against MDR1. Also, expression levels and single-nucleotide polymorphisms (SNPs) of MDR1 in 22 lung cancer cell lines were examined, and the relationships between these factors and sensitivity to amrubicinol were evaluated.

RESULTS

The MDR1 gene was increased approximately 4,500-fold in PC-6/AMR-OH cells compared with PC-6 cells, and intracellular accumulation of amrubicinol in PC-6/AMR-OH cells was decreased to about 15 percent of that in PC-6 cells. Treatment with verapamil and siRNA against MDR1 significantly increased the sensitivity to amrubicinol in PC-6/AMR-OH cells with increased cellular accumulation of amrubicinol. Meanwhile, neither MDR1 gene expression levels nor SNPs of the gene were associated with amrubicinol sensitivity.

CONCLUSIONS

Results of this study indicate that increased MDR1 expression and P-gp activity confer acquired resistance to amrubicinol. In contrast, neither expression level nor SNPs of MDR1 are likely to be predictive markers for amrubicin activity.

Recent Pharmacological Advances: Focus on Small-cell Lung Cancer

Small cell lung cancer (SCLC) represents approximately 15% of all lung cancers, and is the most aggressive form of lung cancer. Left untreated, the time from diagnosis to death is 2–3 months. With current treatment, expected survival is 7–20 months, depending on the stage of disease. A new drug, amrubicin, is approved in Japan for lung cancer and has demonstrated efficacy in U.S. and European phase II trials of SCLC patients with either untreated disease or relapsed refractory illness. In a phase II study of amrubicin in previously untreated patients, response rates reached 75% with a median survival time of almost 1 year. Amrubicin is a fully synthetic 9-aminoanthracycline, and an analog of doxorubicin and epirubicin. The major mechanism of action of amrubicin is inhibition of topoisomerase II. Unlike doxorubicin, however, it exhibits little or no cardiotoxicity in clinical studies and preclinical models. In preclinical rodent tumor models, it is selectively distributed to tumour tissue and is not detected in the heart when compared with doxorubicin, which is distributed equivalently to these sites. The primary metabolite of amrubicin, amrubicinol, is up to 100 times more cytotoxic in vitro than the parent compound. This review describes the mechanisms of action of amrubicin as well as clinical studies which demonstrate the potential of this drug in future SCLC treatment. The review also puts forward hypothetical considerations for the use of other drugs such as lenalidomide, an immunomodulatory drug acting on multiple signalling pathways, or histone deacetylase inhibitors, in combination with amrubicin in SCLC.

Retrospective analysis of efficacy and safety of amrubicin in refractory and relapsed small-cell lung cancer

BACKGROUND

Amrubicin, a totally synthetic 9-aminoanthracycline, was evaluated retrospectively for the treatment of refractory and relapsed small-cell lung cancer (SCLC).

METHODS

Retrospective analysis was performed in 32 patients. Amrubicin was infused over 5 min on days 1-3, with courses repeated at 3- or 4-week intervals. Amrubicin was given at a dose of 45 mg/m(2) per day, 40 mg/m(2) per day, 35 mg/m(2) per day, 30 mg/m(2) per day, or 25 mg/m(2) per day depending on medical conditions (patients' age and performance status [PS]), and the dose was modulated according to myelosuppression.

RESULTS

The median number of treatment cycles was 3 (range, 1-6). Seventeen patients (53.1%) had a partial response. Median progression-free survival time for all patients was 96 days, and median survival time was 166 days. Grade 3 or 4 hematologic toxicities comprised neutropenia (78.1%), anemia (65.6%), and thrombocytopenia (50.0%). Febrile neutropenia was observed in 8 patients (25.0%). Nonhematologic toxicities were mild. Treatment-related death was observed in 1 patient.

CONCLUSION

Treatment with amrubicin appeared effective in SCLC patients previously treated with chemotherapy, although it was not necessarily safe, because of myelosuppression. Further research is warranted to investigate amrubicin treatment for patients with SCLC.

Pharmacokinetics of Amrubicin and Its Active Metabolite Amrubicinol in Lung Cancer Patients

Amrubicin, a synthetic 9-aminoanthracycline agent, was recently approved in Japan for treatment of small-cell lung cancer and non-small-cell lung cancer. Amrubicin is converted enzymatically to the C-13 hydroxy metabolite amrubicinol, which is active and possesses a cytotoxicity 10 to 100 times that of the parent drug. The purpose of this study was to characterize the pharmacokinetics of amrubicin and its active metabolite amrubicinol. Amrubicin was administered on days 1-3 in 16 patients with advanced lung cancer. The pharmacokinetics analysis of amrubicin and amrubicinol was performed by high-performance liquid chromatography. When 45 mg/m amrubicin was administered in a bolus injection once every 24 hours for 3 consecutive days, the areas under the curves (0 to 72 hours) for amrubicin and amrubicinol were 13,490 and 2585 ng . h/mL, respectively. The apparent total clearance (CLapp) of amrubicin was 15.4 L/h. The area-under-the-curve ratio of amrubicinol to amrubicin was 15.1 +/- 4.6% (mean +/- SD) at doses ranging from 30 to 45 mg/m. Interindividual variability in the enzymatic conversion of amrubicin to amrubicinol was small. In contrast, a large interindividual variability in the CLapp of amrubicin was observed (CV = 49.8%). The areas under the curves of amrubicin and amrubicinol seemed to be associated with the severity of hematologic toxicities. There is a possibility that monitoring of the plasma concentrations of amrubicin and amrubicinol may provide an efficient tool for establishing the optimal dosage of amrubicin in each patient.

Phase I and pharmacokinetic study of amrubicin, a synthetic 9-aminoanthracycline, in patients with refractory or relapsed lung cancer

Amrubicin is a novel synthetic 9-aminoanthracycline derivative and is converted enzymatically to its C-13 hydroxy metabolite, amrubicinol, whose cytotoxic activity is 10-100 times that of amrubicin. We aimed to determine the maximum tolerated dose (MTD) of amrubicin and to characterize the pharmacokinetics of amrubicin and amrubicinol in previously treated patients with refractory or relapsed lung cancer. The 15 patients were treated with amrubicin intravenously at doses of 30, 35, or 40 mg/m(2) on three consecutive days every 3 weeks for a total of 43 courses. Neutropenia was the major toxicity (grade 4, 67%). The MTD was 40 mg/m(2), with the specific dose-limiting toxicities being grade 4 neutropenia persisting for >4 days, febrile neutropenia, or grade 3 arrhythmia in the three patients treated at this dose. A patient with non-small-cell lung cancer showed a partial response, and ten individuals experienced a stable disease. The area under the plasma concentration versus time curve (AUC) for amrubicin and that for amrubicinol increased with amrubicin dose. The amrubicin AUC was significantly correlated with the amrubicinol AUC. The recommended phase II dose of amrubicin for patients with lung cancer refractory to standard chemotherapy is thus 35 mg/m(2) once a day for three consecutive days every 3 weeks.

Natural products to drugs: natural product derived compounds in clinical trials

Natural product and natural product-derived compounds that are being evaluated in clinical trials or in registration (current 31 December 2004) have been reviewed. Natural product derived drugs launched in the United States of America, Europe and Japan since 1998 and new natural product templates discovered since 1990 are discussed.

Phase I–II study of amrubicin and cisplatin in previously untreated patients with extensive-stage small-cell lung cancer

BACKGROUND

Amrubicin, a totally synthetic 9-amino-anthracycline, demonstrated excellent single-agent activity for extensive-stage small-cell lung cancer (ED-SCLC). The aims of this trial were to determine the maximum-tolerated doses (MTD) of combination therapy with amrubicin and cisplatin, and to assess the efficacy and safety at their recommended doses (RD).

PATIENTS AND METHODS

Eligibility criteria were patients having histologically or cytologically proven measurable ED-SCLC, no previous systemic therapy, an Eastern Cooperative Oncology Group performance status of 0-2 and adequate organ function. Amrubicin was administered on days 1-3 and cisplatin on day 1, every 3 weeks.

RESULTS

Four patients were enrolled at dose level 1 (amrubicin 40 mg/m(2)/day and cisplatin 60 mg/m(2)) and three patients at level 2 (amrubicin 45 mg/m(2)/day and cisplatin 60 mg/m(2)). Consequently, the MTD and RD were determined to be at level 2 and level 1, respectively. The response rate at the RD was 87.8% (36/41). The median survival time (MST) was 13.6 months and the 1-year survival rate was 56.1%. Grade 3/4 neutropenia and leukopenia occurred in 95.1% and 65.9% of patients, respectively.

CONCLUSIONS

The combination of amrubicin and cisplatin has demonstrated an impressive response rate and MST in patients with previously untreated ED-SCLC.