Phase II trial of oral rubitecan in previously treated pancreatic cancer patients

Camptothecin and its derivatives: Advancements, mechanisms and clinical potential in cancer therapy

Camptothecin (CPT), an alkaloid isolated from the Camptotheca tree, has demonstrated significant anticancer properties in a range of malignancies. However, its therapeutic efficacy is limited by its hydrophobicity, poor bioavailability, and systemic toxicity. Derivatives, analogues, and nanoformulations of CPT have been synthesized to overcome these limitations. The aim of this review is to comprehensively analyze existing studies to evaluate the therapeutic efficacy, mechanistic aspects, and clinical potential of CPT and its modified forms, including derivatives, analogues, and nanoformulations, in cancer treatment. A comprehensive literature review was performed using PubMed/Medline, Scopus, and Web of Science databases; articles were selected based on specific inclusion criteria, and data were extracted on the pharmacological profile, clinical studies, and therapeutic efficacy of CPT and its different forms. Current evidence suggests that derivatives and analogues of CPT have improved water solubility, bioavailability, and reduced systemic toxicity compared to CPT. Nanoformulations further enhance targeted delivery and reduce off-target effects. Clinical trials indicate promising outcomes with enhanced survival rates and lower side effects. CPT and its modified forms hold significant promise as potent anticancer agents. Ongoing research and clinical trials are essential for establishing their long-term efficacy and safety; the evidence overwhelmingly supports further development and clinical testing of these compounds.

Natural product inspired leads in the discovery of anticancer agents: an update

Natural products have emerged as major leads for the discovery and development of new anti-cancer drugs. The plant-derived anti-cancer drugs account for approximately 60% and the quest for new anti-cancer agents is in progress. Anti-cancer leads have been isolated from plants, animals, marine organisms, and microorganisms from time immemorial. The process of semisynthetic modifications of the parent lead has led to the generation of new anti-cancer agents with improved therapeutic efficacy and minimal side effects. The various chemo-informatics tools, bioinformatics, high-throughput screening, and combinatorial synthesis are able to deliver the new natural product lead molecules. Plant-derived anticancer agents in either late preclinical development or early clinical trials include taxol, vincristine, vinblastine, topotecan, irinotecan, etoposide, paclitaxel, and docetaxel. Similarly, anti-cancer agents from microbial sources include dactinomycin, bleomycin, mitomycin C, and doxorubicin. In this review, we highlighted the importance of natural products leads in the discovery and development of novel anti-cancer agents. The semisynthetic modifications of the parent lead to the new anti-cancer agent are also presented. Further, the leads in the preclinical settings with the potential to become effective anticancer agents are also reviewed.Communicated by Ramaswamy H. Sarma.

Topoisomerase 1B poisons: Over a half-century of drug leads, clinical candidates, and serendipitous discoveries

Topoisomerases are DNA processing enzymes that relieve supercoiling (torsional strain) in DNA, are necessary for normal cellular division, and act by nicking (and then religating) DNA strands. Type 1B topoisomerase (Top1) is overexpressed in certain tumors, and the enzyme has been extensively investigated as a target for cancer chemotherapy. Various chemical agents can act as "poisons" of the enzyme's religation step, leading to Top1-DNA lesions, DNA breakage, and eventual cellular death. In this review, agents that poison Top1 (and have thus been investigated for their anticancer properties) are surveyed, including natural products (such as camptothecins and indolocarbazoles), semisynthetic camptothecin and luotonin derivatives, and synthetic compounds (such as benzonaphthyridines, aromathecins, and indenoisoquinolines), as well as targeted therapies and conjugates. Top1 has also been investigated as a therapeutic target in certain viral and parasitic infections, as well as autoimmune, inflammatory, and neurological disorders, and a summary of literature describing alternative indications is also provided. This review should provide both a reference for the medicinal chemist and potentially offer clues to aid in the development of new Top1 poisons.

Use of gemcitabine as a second-line treatment following chemotherapy with folfirinox for metastatic pancreatic adenocarcinoma

There is a lack of prospective data about second-line treatments for metastatic pancreatic ductal adenocarcinoma patients. This is partially due to recent changes in first-line chemotherapy treatments. Despite this dearth of information, 50.0% of the patients who experience failure with first-line folinic acid, 5-fluorouracil, irinotecan and oxaliplatin (folfirinox) treatment are eligible for additional chemotherapy. In this setting, gemcitabine is widely used without any standard recommendations available. The present study evaluated 42 patients who received gemcitabine subsequent to a first-line treatment of folfirinox between January 2008 and December 2012 at the Centre Léon Bérard (Lyon, France). Clinical data, biological data and tumor characteristics were retrospectively analyzed to identify prognostic factors for successful treatment with gemcitabine. In total, 11 patients (26.2%) experienced control of their cancer with gemcitabine treatment. However, there was no predictive marker for their response to the drug. The median overall survival was 3.6 months from gemcitabine initiation [95% confidence interval (CI), 2.1-5.1]. The median length of gemcitabine treatment was 1.5 months (95% CI, 0.3-13.3). Among the 11 patients who were successfully treated with gemcitabine, 6 were resistant to first-line folfirinox treatment. Patients who were non responsive to folfirinox had a higher probability of success with gemcitabine compared with patients that responded to folfirinox (54.5 vs. 21.4%, respectively; P=0.061). The present study did not identify any clinical or biological marker with a predictive value for successful gemcitabine treatment. Furthermore, successful gemcitabine treatment was not correlated with patients' response to first-line folfirinox treatment. This suggests an absence of cross-resistance in the chemotherapy protocols and provides evidence for effective cancer treatment with the second-line gemcitabine therapy.

Second-line chemotherapy for advanced pancreatic cancer: Which is the best option?

Despite recent biological insight and therapeutic advances, the prognosis of advanced pancreatic cancer still remains poor. For more than 15 years, gemcitabine monotherapy has been the cornerstone of first-line treatment. Recently, prospective randomized trials have shown that novel upfront combination regimens tested in prospective randomized trials have resulted in improved patients' outcome increasing the proportion of putative candidate to second-line therapy. There is no definite standard of care after disease progression. A novel formulation in which irinotecan is encapsulated into liposomal-based nanoparticles may increase the efficacy of the drug without incrementing its toxicity. NAPOLI-1 was the first randomized trial to compare nanoliposomal irinotecan and fluorouracil-leucovorin (5-FU/LV) to 5-FU/LV alone after a gemcitabine-based chemotherapy. This review focuses on the current data for the management of second-line treatment for metastatic pancreatic adenocarcinoma, presents the most interesting ongoing clinical trials and illustrates the biologically-driven future options beyond disease progression.

The long story of camptothecin: From traditional medicine to drugs

20-(S)-Camptothecin (CPT) is a natural alkaloid extracted from the bark of Camptotheca acuminata (Chinese happy tree). It acts as a DNA topoisomerase 1 poison with an interesting antitumor activity and its use is limited by low stability and solubility and unpredictable drug-drug interactions. Since the late 20th century, it has been widely used in cancer therapy and, since extraction yields from plant tissues are very low, various synthetic routes have been developed to satisfy the increase in demand for CPT. Moreover, SAR studies have allowed for the development of more potent CPT analogues topotecan and irinotecan. Unfortunately, resistance has already occurred in several tumour lines. Additional studies are needed to better understand the relationship between substituents and resistance, its clinical relevance and the impact of related gene polymorphism. One of the latest research approaches focuses on modifying the delivery mode to improve tumour cell uptake and reduce toxicity.

Safe approaches for camptothecin delivery: Structural analogues and nanomedicines

Twenty-(S)-camptothecin is a strongly cytotoxic molecule with excellent antitumor activity over a wide spectrum of human cancers. However, the direct formulation is limited by its poor water solubility, low plasmatic stability and severe toxicity, which currently limits its clinical use. As a consequence, two strategies have been developed in order to achieve safe and efficient delivery of camptothecin to target cells: structural analogues and nanomedicines. In this review, we summarize recent advances in the design, synthesis and development of camptothecin molecular derivatives and supramolecular vehicles, following a systematic classification according to structure-activity relationships (structural analogues) or chemical nature (nanomedicines). A series of organic, inorganic and hybrid materials are presented as nanoplatforms to overcome camptothecin restrictions in administration, biodistribution, pharmacokinetics and toxicity. Nanocarriers which respond to a variety of stimuli endogenously (e.g., pH, redox potential, enzyme activity) or exogenously (e.g., magnetic field, light, temperature, ultrasound) seem the best positioned therapeutic materials for optimal spatial and temporal control over drug release. The main goal of this review is to be used as a source of relevant literature for others interested in the field of camptothecin-based therapeutics. To this end, final remarks on the most important formulations currently under clinical trial are provided.

Second-line treatment in inoperable pancreatic adenocarcinoma: A systematic review and synthesis of all clinical trials

There remains uncertainty regarding the optimal second-line chemotherapy in advanced pancreatic ductal adenocarcinoma (PDAC). The current recommendation of 5-fluorouracil and oxaliplatin may not be relevant in current practice, as FOLFIRINOX (5-fluorouracil, leucovorin, irinotecan and oxaliplatin) has become a more popular first line therapy in fit patients. The majority of studies in this setting are single-arm Phase II trials with significant heterogeneity of patient populations, treatments and outcomes. In this review, we sought to systematically review and synthesise all prospective data available for the second-line treatment of advanced PDAC.

Recent advances for the treatment of pancreatic and biliary tract cancer after first-line treatment failure

Here, we evaluate clinical trials on chemotherapy for patients with pancreatic or biliary tract cancer after first-line treatment failure. Clinical trials on conventional and innovative medical treatments for progressive pancreatic and biliary cancer were analyzed. Metronomic chemotherapy, which consists of the administration of continuative low-dose of anticancer drugs, was also considered. A significant extension of overall survival was achieved with second-line, regimens in patients with gemcitabine-refractory pancreatic cancer. Moreover, many Phase II studies, including chemotherapy and target molecules and immunotherapy, have reported promising results, in both pancreatic and biliary cancer. However, data in these patients' setting are very heterogeneous, and only few randomized studies are available.

Beyond first-line chemotherapy for advanced pancreatic cancer: an expanding array of therapeutic options?

While an increasing number of therapeutic options are now available for the first-line treatment of locally advanced or metastatic pancreatic cancer, the optimal choice for treatment in the second-line setting and beyond is less well defined. A variety of cytotoxic agents, either alone or in combination, have been evaluated, although primarily in the context of small single-arm or retrospective studies. Most regimens have been associated with median progression-free survival rates in the range of 2-4 mo and overall survival rates between 4-8 mo, highlighting the very poor prognosis of patients who are candidates for such treatment. Targeted therapies studied in this chemotherapy-refractory setting, meanwhile, have produced even worse efficacy results. In the current article, we review the clinical evidence for treatment of refractory disease, primarily in patients who have progressed on front-line gemcitabine-based chemotherapy. In the process, we highlight the limitations of the available data to date as well as some of the challenges in designing appropriate clinical trials in this salvage setting, including how to select an appropriate control arm given the absence of a well-established reference standard, and the importance of incorporating predictive biomarkers and quality of life measures whenever possible into study design.

A multinational phase 2 study of nanoliposomal irinotecan sucrosofate (PEP02, MM-398) for patients with gemcitabine-refractory metastatic pancreatic cancer

BACKGROUND

PEP02, also known as MM-398, is a novel nanoliposomal irinotecan that has improved pharmacokinetics and tumour bio-distribution of the free drug. This phase 2 study evaluated PEP02 monotherapy as second-line treatment for pancreatic cancer.

METHODS

Patients who had metastatic pancreatic adenocarcinoma, Karnofsky performance status ≥70, and had progressed following gemcitabine-based therapy were eligible. Intravenous injection of PEP02 120 mg m(-2) was given every 3 weeks. Simon 2-stage design was used. The primary objective was 3-month survival rate (OS(3-month)).

RESULTS

A total of 40 patients were enrolled. The most common severe adverse events included neutropenia, abdominal pain, asthenia, and diarrhoea. Three patients (7.5%) achieved an objective response, with an additional 17 (42.5%) demonstrating stable disease for a minimum of two cycles. Ten (31.3%) of 32 patients with an elevated baseline CA19-9 had a >50% biomarker decline. The study met its primary end point with an OS(3-month) of 75%, with median progression-free survival and overall survival of 2.4 and 5.2 months, respectively.

CONCLUSION

PEP02 demonstrates moderate antitumour activity with a manageable side effect profile for metastatic, gemcitabine-refractory pancreatic cancer patients. Given the limited treatment options available to this patient population, a phase 3 trial of PEP02 (MM-398), referred to as NAPOLI-1, is currently underway.

Second-line treatment in advanced pancreatic cancer: a comprehensive analysis of published clinical trials

BACKGROUND

There is currently no standard of care for the second-line treatment of advanced pancreatic cancer. The aim of this analysis was to compare the different therapeutic approaches in this setting.

METHODS

We carried out a systematic analysis of second-line studies in advanced pancreatic cancer that have progressed on or following gemcitabine and published or presented from 2000 to 2012.

RESULTS

Forty-four clinical trials (t) were identified; of which 34 met the inclusion criteria treating an aggregate total of 1503 patients (n). Patients who received treatments (t: 33; n: 1269) had a median overall survival (OS) of 6 months compared with 2.8 months for patients who received best supportive care only (t: 2; n: 234) (P = 0.013). The gemcitabine and platinum-based combination (t: 5; n: 154) provided a median progression-free survival and OS of 4 and 6 months compared with 1.6 and 5.3 for the rest of the regimens (t: 29; n: 1349) (P = 0.059 and 0.10, respectively) and 2.9 and 5.7 for the combination of 5-fluorouracil and platinum agents (t: 12; n: 450) (P = 0.60 and 0.22, respectively).

CONCLUSION(S)

Although not conclusive, these data showed that the advantage of second-line chemotherapy in pancreatic cancer is very limited and there is a need for more studies.

Current developments, problems and solutions in the non-surgical treatment of pancreatic cancer

Pancreatic cancer is a common malignant neoplasm of the pancreas with an increasing incidence, a low early diagnostic rate and a fairly poor prognosis. To date, the only curative therapy for pancreatic cancer is surgical resection, but only about 20% patients have this option at the time of diagnosis and the mean 5-year survival rate after resection is only 10%-25%. Therefore, developing new treatments to improve the survival rate has practical significance for patients with this disease. This review deals with a current unmet need in medical oncology: the improvement of the treatment outcome of patients with pancreatic cancer. We summarize and discuss the latest systemic chemotherapy treatments (including adjuvant, neoadjuvant and targeted agents), radiotherapy, interventional therapy and immunotherapy. Besides discussing the current developments, we outline some of the main problems, solutions and prospects in this field.

Biomarker-driven trial in metastatic pancreas cancer: feasibility in a multicenter study of saracatinib, an oral Src inhibitor, in previously treated pancreatic cancer

Src tyrosine kinases are overexpressed in pancreatic cancers, and the oral Src inhibitor saracatinib has shown antitumor activity in preclinical models of pancreas cancer. We performed a CTEP-sponsored Phase II clinical trial of saracatinib in previously treated pancreas cancer patients, with a primary endpoint of 6-month survival. A Simon MinMax two-stage phase II design was used. Saracatinib (175 mg/day) was administered orally continuously in 28-day cycles. In the unselected portion of the study, 18 patients were evaluable. Only two (11%) patients survived for at least 6 months, and three 6-month survivors were required to move to second stage of study as originally designed. The study was amended as a biomarker-driven trial (leucine rich repeat containing protein 19 [LRRC19] > insulin-like growth factor-binding protein 2 [IGFBP2] "top scoring pairs" polymerase chain reaction [PCR] assay, and PIK3CA mutant) based on preclinical data in a human pancreas tumor explant model. In the biomarker study, archival tumor tissue or fresh tumor biopsies were tested. Biomarker-positive patients were eligible for the study. Only one patient was PIK3CA mutant in a 3' untranslated region (UTR) portion of the gene. This patient was enrolled in the study and failed to meet the 6-month survival endpoint. As the frequency of biomarker-positive patients was very low (<3%), the study was closed. Although we were unable to conclude whether enriching for a subset of second/third line pancreatic cancer patients treated with a Src inhibitor based on a biomarker would improve 6-month survival, we demonstrate that testing pancreatic tumor samples for a biomarker-driven, multicenter study in metastatic pancreas cancer is feasible.

Salvage therapy with mitomycin and ifosfamide in patients with gemcitabine-resistant metastatic pancreatic cancer: a phase II trial

BACKGROUND

At the time of upfront treatment failure, over half of the patients with advanced pancreatic cancer are candidates for further treatment.

METHODS

Patients with metastatic gemcitabine-resistant pancreatic cancer were treated with mitomycin 8 mg/m(2) on day 1, ifosfamide 2,500 mg/m(2) and mesna 3,000 mg/m(2) on days 1-3 every 28 days until progressive disease. A positive responder was defined as a patient who was progression free at 6 months from trial enrollment. According to the Fleming design, a sample size of 34 patients was estimated assuming p0 = 0.05 and p1 = 0.20.

RESULTS

Between May 2006 and December 2007, 21 patients (median age 56 years; median Karnofsky performance score 80) were enrolled. One patient died before receiving any treatment. Eighteen patients interrupted chemotherapy due to progressive disease (n = 15), toxicity (n = 2) or refusal (n = 1). Grade >2 toxicity consisted of neutropenia in 80% of patients, thrombocytopenia and fatigue in 20% and anemia in 10%. Only 1 patient was progression free at 6 months (5%). One patient had a partial response (5%) and 2 patients had stable disease (10%). Median survival was 3.7 months.

CONCLUSION

Based on the poor outcome observed and on the high level of grade 3-4 toxicity, the trial was prematurely stopped and the mitomycin and ifosfamide regimen was considered insufficiently active in gemcitabine-pretreated advanced pancreatic cancer.

A prognostic model to identify patients with advanced pancreas adenocarcinoma who could benefit from second-line chemotherapy

AIMS

The role of salvage chemotherapy after first-line therapy in advanced pancreatic cancer has not yet been established. We intended to identify prognostic factors for long-term survival of advanced pancreatic adenocarcinoma patients with second-line chemotherapy and to devise a prognostic model of clinical parameters.

PATIENTS AND METHODS

We analysed 90 patients who had received second-line chemotherapy after the failure of first-line therapy in recurrent or metastatic pancreatic adenocarcinoma between August 2003 and December 2008.

RESULTS

The median age at the time of second-line chemotherapy was 61.9 years (range 39.8-74.9) and the median Eastern Cooperative Oncology Group (ECOG) performance status was 1 (0-2). Median progression-free survival and overall survival for second-line chemotherapy were 2.1 and 4.5 months, respectively, with an overall response rate of 10%. In multivariate analysis, an ECOG performance status of 2 or more, non-responder for first-line chemotherapy and albumin level of <3.5mg/dl were independent prognostic factors for decreased overall survival for all 90 patients. Overall survival was estimated based on the number of adverse prognostic factors: zero or one (good prognostic group), two (intermediate group) or three (poor prognostic group). The median overall survival for good (n=50), intermediate (n=24) and poor (n=16) prognostic groups was 5.5, 3.3 and 2.1 months, respectively (P<0.001).

CONCLUSION

Our result suggests that second-line chemotherapy may be beneficial for overall survival in patients with ECOG performance status 0-1, albumin level ≥3.5mg/dl and response to first-line chemotherapy.

A tolerability and pharmacokinetic study of adjuvant erlotinib and capecitabine with concurrent radiation in resected pancreatic cancer

BACKGROUND

Erlotinib is approved for the treatment of advanced pancreas cancer. We conducted a prospective trial to determine the safety profile and recommended phase 2 dose of erlotinib and capecitabine given concurrently with intensity-modulated radiation therapy (IMRT) in resected pancreatic cancer patients. The pharmacokinetic profile of this combination was also evaluated.

METHODS

Patients with resected pancreatic adenocarcinoma received erlotinib and capecitabine concurrently with IMRT delivered at 1.8 Gy daily in 28 fractions (total = 50.4 Gy). The starting dose level (DL 1) was erlotinib 150mgdaily and capecitabine 800 mg/m(2) twice daily without interruption. The next lower dose level (DL -1) was erlotinib 100 mg daily and capecitabine 800 mg/m(2) twice daily (Monday to Friday). Plasma samples were obtained for pharmacokinetic analysis.

RESULTS

Thirteen patients were enrolled in total. At DL 1, six of the seven treated patients were evaluable for toxicities. Four completed planned treatment, but all required treatment interruption or dose reduction. The dose-limiting toxicities were neutropenia, diarrhea, and rash. Six patients were subsequently enrolled to and completed planned treatment in DL-1. Themost common toxicities were fatigue, elevated liver enzymes, and anorexia. The pharmacokinetic parameters of erlotinib and OSI-420 were not significantly different in the presence or absence of capecitabine and were consistent with historical controls.

CONCLUSIONS

When administered concurrently with IMRT, erlotinib 100 mg daily and capecitabine 800 mg/m(2) twice daily (Monday to Friday) can be administered safely in resected pancreas cancer patients, and is the recommended regimen for efficacy studies using this regimen.

Weekly Paclitaxel after failure of gemcitabine in pancreatic cancer patients with malignant ascites: a retrospective study

OBJECTIVES

Peritoneal metastasis is one of the major sites of disease progression of pancreatic cancer. There have been few trials in the second-line setting after gemcitabine failure because patients can hardly be candidates for chemotherapy after failure in the first-line chemotherapy, especially those with malignant ascites. The safety and efficacy of weekly paclitaxel therapy was evaluated for pancreatic cancer patients with malignant ascites in this retrospective study.

METHODS

The subjects of this retrospective study were 23 advanced pancreatic cancer patients with malignant ascites who received weekly paclitaxel therapy after gemcitabine failure. Paclitaxel (80 mg/m(2), div. for 1 h) was administered on Days 1, 8 and 15, every 4 weeks.

RESULTS

While the disease control rate was 35%, decrease of ascites was obtained in 30% of the patients and ascites control rate was 61%. The median survival time was 101 days. Toxicities were mild, although one treatment-related death occurred.

CONCLUSIONS

Weekly paclitaxel therapy may be useful treatment option for pancreatic cancer patients with malignant ascites after gemcitabine failure.

BACPTDP: a water-soluble camptothecin pro-drug with enhanced activity in hypoxic/acidic tumors

Hypoxia is a common feature of solid tumors. Up-regulation of hypoxia-inducing factor-1 (HIF-1) occurs in the majority of primary malignant tumors and in two-thirds of metastases, while most normal tissues are negative. HIF-1 induces the glycolytic phenotype, which creates an acidic extracellular microenvironment and associated pH gradient such that drugs that are weak acids are selectively taken up and retained in acidic tumors. 7-Butyl-10-amino-camptothecin (BACPT) is a prime example of an agent that can exploit the tumor pH gradient for enhanced selectivity.

PURPOSE

This study profiles the antitumor activity of BACPT in vitro and its water-soluble dipeptide ester, BACPTDP, in vivo.

METHODS

Antitumor activity was evaluated by proliferation assays in cancer cell lines and in murine xenograft models for human neuroblastoma (IMR-32), colon (HT29), ovarian (SK-OV-3), pancreatic (Panc-1), glioma (SF-295) and non-small-cell lung (NCI-H460) cancers.

RESULTS

BACPT had superior antiproliferative activity compared to established drugs in monolayer cultures of human neuroblastoma and pancreatic tumor cell lines and in 3-dimensional histocultures of colon and primary ovarian cancer. Antitumor activity of BACPTDP was comparable to irinotecan in IMR-32, HT29, SF-295 and NCI-H460 xenografts, significantly greater in SK-OV-3 and in Panc-1 where complete regressions were observed. Combination of BACPT with gemcitabine produced additive to synergistic interactions in Panc-1 cells that were independent of drug ratio and optimal when gemcitabine was administered 24 h prior to BACPT.

CONCLUSIONS

BACPTDP is a water-soluble camptothecin pro-drug that spontaneously generates the lipid-soluble active agent, BACPT. This topoisomerase inhibitor exploits solid tumor physiology for improved selectivity and activity against multiple tumor types with particular promise for use in treating pediatric neuroblastoma and pancreatic carcinoma.

Second-line chemotherapy with capecitabine (Xeloda) and docetaxel (Taxotere) in previously treated, unresectable adenocarcinoma of pancreas: the final results of a phase II trial

PURPOSE

To investigate the efficacy and toxicity of the docetaxel and capecitabine combination in patients with previously treated, unresectable adenocarcinoma of the pancreas.

PATIENTS AND METHODS

Patients with pancreatic adenocarcinoma, pre-treated with gemcitabine-based chemotherapy, were treated with capecitabine (800 mg/m(2) orally, twice a day for 14 days) and docetaxel (75 mg/m(2) i.v, on day 1), every 3 weeks. The primary end-point was overall response rate (RR).

RESULTS

Thirty-one patients were enrolled in the study; 93.6% of them had a performance status (PS) of 0-1 and 96.8% had stage IV disease. Patients received a median of 4 cycles/patient, and the main reason for treatment discontinuation was disease progression. Partial response was observed in three (9.7%) patients, stable disease in seven (22.6%) (disease control rate: 32.3%, 95% CI: 15.80-48.71%) and disease progression in 21 (67.6%). The median progression-free survival (PFS) was 2.4 months (95% CI: 1.6-3.13) and the median overall survival (OS) was 6.3 months (95% CI: 3.38-9.23); the estimated 1-year survival rate was 14.7%. Grade III/IV neutropenia occurred in 10 (32.2%) patients and febrile neutropenia in one patient. Other severe non-hematologic toxicities were mild and manageable. After 2 chemotherapy cycles, pain control occurred in 20% of patients and stabilization of body weight in 40%.

CONCLUSION

The combination of docetaxel/capecitabine may confer good disease control associated with improvement of quality of life as second-line chemotherapy in patients with metastatic pancreatic cancer.

Phase II study of S-1 in patients with gemcitabine-resistant advanced pancreatic cancer

PURPOSE

The primary objective of this study was to assess the efficacy and safety of S-1 in patients with gemcitabine-resistant advanced pancreatic cancer.

METHODS

Patients with histologically or cytologically proven, advanced pancreatic cancer who had received first-line chemotherapy with gemcitabine were eligible for this study. S-1 was administered orally at a dose of 40 mg/m(2) twice daily for 28 days, followed by 14 days' rest. Treatment was repeated every 6 weeks until disease progression.

RESULTS

Twenty-one patients were enrolled in this study. Grade 3 and 4 toxicities included anorexia in 14% of the patients, abdominal pain in 4.8% and infection without neutropenia in 4.8%. S-1 was discontinued in two patients because of toxicity. Of the 21 eligible patients, 2 (9.5%) achieved a partial response and 9 (43%) had stable disease. A marked decrease (≥50%) in tumor marker (CA19-9) was observed in 5 (28%) of the 18 evaluable patients. The median progression-free survival and the median survival time from the first day of S-1 therapy were 4.1 months (95% CI, 1.3-6.9 months) and 6.3 months (95% CI, 3.6-8.9 months), respectively.

CONCLUSIONS

Second-line chemotherapy with S-1 was tolerated with acceptable toxicity and resulted in a relatively high disease control rate in patients with gemcitabine-resistant advanced pancreatic cancer. As an oral agent, S-1 may be a feasible treatment option for this patient population.

S-1 monotherapy as second-line treatment for advanced pancreatic cancer after gemcitabine failure

OBJECTIVE

No standard salvage chemotherapy regimen has been established for patients with advanced pancreatic cancer after failure of gemcitabine-based treatment. Although a Phase II study of S-1 monotherapy was conducted in patients with gemcitabine-refractory advanced pancreatic cancer, the number of patients enrolled was small.

METHODS

We retrospectively reviewed 84 consecutive patients who received S-1 monotherapy as a second-line treatment after gemcitabine failure at the Shizuoka Cancer Center between May 2004 and April 2008. The selection criteria in this study were age 20-75 years, ECOG performance status <or=2 and preserved organ functions. S-1 was administered orally twice a day at a dose of 40 mg/m(2) for 28 days, followed by 14-day rest.

RESULTS

Fifty-two patients were selected for the analysis. Out of the 47/52 patients with measurable lesions, only 2 patients (4%) showed a partial response and 15 patients (32%) showed stable disease. The median progression-free survival was 2.1 months and the median overall survival was 5.8 months, with a 1-year survival rate of 12%. The common grade 3/4 toxicities were diarrhea (8%), anorexia (6%), fatigue (6%), anemia (6%) and leucopenia (4%).

CONCLUSIONS

S-1 monotherapy is marginally effective and well tolerated in the second-line setting in patients with gemcitabine-refractory advanced pancreatic cancer.

A phase II study of bevacizumab plus erlotinib for gemcitabine-refractory metastatic pancreatic cancer

PURPOSE

No standard of care exists for patients with metastatic pancreatic cancer following progression on first-line chemotherapy. Based on potential for additive or synergistic activity by concurrent inhibition of VEGF and EGFR, we conducted a phase II study evaluating the combination of bevacizumab plus erlotinib in this patient population.

METHODS

Patients with metastatic pancreatic adenocarcinoma, ECOG performance status 0-1, and previous exposure to 1-3 systemic therapies (at least one gemcitabine-based) were eligible. Treatment consisted of bevacizumab 15 mg/kg every 21 days plus erlotinib 150 mg daily.

RESULTS

Thirty-six patients were enrolled, including eight who had previously received VEGF-targeted therapy and nine prior erlotinib. Median number of treatment cycles was 2 (range, 1-7). Common toxicities included rash (72%), diarrhea (25%), venous thromboembolic events (15%), and hypertension (11%). One patient demonstrated partial response and seven others stable disease for >2 cycles. CA19-9 decline ≥25% was observed in 4/26 patients with baseline levels >2x ULN. Estimated median time to progression was 40 days (95% CI, 35-41 days) and median survival 102 days (95% CI, 74-117 days), with a 6-month survival rate of 22%. Baseline concentration of circulating endothelial cells (CD45(-)/CD34(+)/CD31(+)) was inversely associated with overall survival.

CONCLUSIONS

The combination of bevacizumab and erlotinib is safe but relatively ineffective in patients with gemcitabine-refractory metastatic pancreatic cancer. Future studies should focus on refining subsets of patients in this challenging population likely to benefit from treatment beyond first-line.

Second-line therapy for advanced pancreatic cancer: a review of the literature and future directions

Whereas first-line chemotherapy (CT) with single-agent gemcitabine or gemcitabine-based combinations provides a proven benefit in patients with locally advanced or metastatic pancreatic cancer (PC), the role of salvage CT after gemcitabine-failure is not well-established and to date no regimen has emerged as preferred in this setting. Several clinical trials have investigated the efficacy and toxicity-profile of second-line CT and indicated that selected patients may obtain significant benefit from it, also with regard to survival. However, definitive results from large randomized phase III studies are still lacking, and the evidence for clinical benefit of salvage CT is based on small phase II trials that evaluated different treatment schedules in heterogeneous populations. The main goal of this paper is reviewing this topic.

Pilot study of irinotecan/oxalipltin (IROX) combination chemotherapy for patients with gemcitabine- and 5-fluorouracil- refractory pancreatic cancer

BACKGROUND

Gemcitabine- and 5-fluorouracil (5-FU)- based chemotherapy is a commonly used adjuvant or palliative treatment for patients with pancreatic cancer. However, a standard chemotherapy regimen has yet to be developed for patients refractory to gemcitabine and 5-FU treatment. We attempted to evaluate the efficacy and safety of a combination of irinotecan and oxaliplatin (IROX) as a salvage treatment for patients with gemcitabine- and 5-FU- refractory pancreatic cancer.

PATIENTS AND METHODS

Patients with advanced pancreatic cancer who were refractory to prior gemcitabine- and 5-FU- based chemotherapy were enrolled in this study. IROX chemotherapy was administered as follows: Irinotecan, 150 mg/m(2) on day 1; and oxaliplatin, 85 mg/m(2) on day 1 over 90 min every 2 weeks.

RESULT

From Mar. 2006 to Dec. 2008, a total of 14 patients were administered 50 cycles of chemotherapy. The male-to-female ratio of the patient group was 11:3. These patients ranged in age from 48 to 73 years (median 65.5 years old). 3 patients (21.4%) evidenced partial responses. four patients (28.6%) exhibited stable disease. The median time to progression and overall survival time were 1.4 (95% CI: 1.2-1.6) months and 4.1 (95% CI: 2.0-6.2) months, respectively. Major hematologic toxicities included grade 1-2 anemia (88%), neutropenia (36%), thrombocytopenia (30%), and grade 3-4 neutropenia (10%). The most frequently detected non-hematological toxicities were grade 3 diarrheas (14%).

CONCLUSION

The IROX regimen appears to constitute a feasible and tolerable salvage therapy in patients with advanced pancreatic cancer who have been previously treated with gemcitabine- and 5-FU-based chemotherapy.

Allogeneic granulocyte macrophage colony-stimulating factor-secreting tumor immunotherapy alone or in sequence with cyclophosphamide for metastatic pancreatic cancer: a pilot study of safety, feasibility, and immune activation

PURPOSE

The combination of chemotherapy and immunotherapy has not been examined in patients with advanced pancreatic cancer. We conducted a study of two granulocyte macrophage colony-stimulating factor-secreting pancreatic cancer cell lines (CG8020/CG2505) as immunotherapy administered alone or in sequence with cyclophosphamide in patients with advanced pancreatic cancer.

EXPERIMENTAL DESIGN

This was an open-label study with two cohorts: cohort A, 30 patients administered a maximum of six doses of CG8020/CG2505 at 21-day intervals; and cohort B, 20 patients administered 250 mg/m(2) of cyclophosphamide i.v. 1 day before the same immunotherapy given as in cohort A. The primary objective was to evaluate safety and duration of immunity. Secondary objectives included time to disease progression and median overall survival.

RESULTS

The administration of CG8020/CG2505 alone or in sequence with cyclophosphamide showed minimal treatment-related toxicity. Median survival values in cohort A and cohort B were 2.3 and 4.3 months, respectively. CD8(+) T-cell responses to HLA class I-restricted mesothelin epitopes were identified predominantly in patients treated with cyclophosphamide + CG8020/CG2505 immunotherapy.

CONCLUSION

Granulocyte macrophage colony-stimulating factor-secreting pancreatic cancer cell lines CG8020/CG2505 alone or in sequence with cyclophosphamide showed minimal treatment-related toxicity in patients with advanced pancreatic cancer. Also, mesothelin-specific T-cell responses were detected/enhanced in some patients treated with CG8020/CG2505 immunotherapy. In addition, cyclophosphamide-modulated immunotherapy resulted in median survival in a gemcitabine-resistant population similar to chemotherapy alone. These findings support additional investigation of cyclophosphamide with CG8020/CG2505 immunotherapy in patients with advanced pancreatic cancer.

Gemcitabine in the treatment of metastatic pancreatic cancer

Gemcitabine (2 ,2 -difluorodeoxycytidine) is a deoxycytidine-analog antimetabolite with broad activity against a variety of solid tumors and lymphoid malignancies. It was approved as standard of care in patients with pancreatic cancer one decade ago, based primarily on improvement in clinical benefit response such as pain reduction, improvement in Karnofsky performance status and increase in body weight. This article gives an overview of the pharmacodynamics and pharmacokinetics of gemcitabine, highlights the clinical activity of gemcitabine and summarizes the treatment options in metastatic pancreatic cancer with focus on gemcitabine-based chemotherapy. The emerging role of combinations of gemcitabine with novel targeted agents, including small-molecule inhibitors and other investigational drugs, is also discussed.

PEFG (cisplatin, epirubicin, 5-fluorouracil, gemcitabine) regimen as second-line therapy in patients with progressive or recurrent pancreatic cancer after gemcitabine-containing chemotherapy

OBJECTIVE

The therapeutic arsenal for salvage therapy in pancreatic cancer is limited. PEFG (cisplatin, epirubicin, 5-fluorouracil [FU], gemcitabine) regimen is an effective upfront treatment in advanced pancreatic cancer. The activity and safety of this combination regimen were assessed by means of an observational study in a population of patients with progressive or recurrent pancreatic adenocarcinoma after gemcitabine-containing chemotherapy.

METHODS

Patients with age <76 years, Karnofsky performance status >50 were treated with either classic PEFG (until April 2004: cisplatin and epirubicin 40 mg/m day 1, gemcitabine 600 mg/m day 1 and 8, FU 200 mg/m/d continuous infusion day 1-28) or dose-intense PEFG (since May 2004: cisplatin and epirubicin 30 mg/m, gemcitabine 800 mg/m every 14 days; FU 200 mg/m/d continuous infusion day 1-28) until progressive disease or a maximum of 6 cycles of 28 days.

RESULTS

Forty-six patients (37 metastatic) received 69 cycles of classic PEFG (18 patients) or 104 cycles of dose-intense PEFG (28 patients) as second-line therapy. Prior treatment consisted of single agent gemcitabine (N = 17), gemcitabine-based chemotherapy (N = 4), or PEFG regimen (N = 25). Median previous progression-free survival was 7.6 months. Dose intensity (mg/m/wk) with classic PEFG was cisplatin and epirubicin 8.5; gemcitabine 230; FU 1035 and with dose-intense PEFG was cisplatin and epirubicin 11.5 (+36%); gemcitabine 259 (+13%); FU 1046 (+1%). Main grade >2 toxicity consisted of neutropenia in 26 patients (56%), thrombocytopenia in 10 (22%), anemia in 11 (24%), fatigue and stomatitis in 4 (9%), vomiting, diarrhea and hand-foot syndrome in 2 (4%). Partial response was observed in 11 patients (24%) (5 classic PEFG 28% + 6 dose-intense PEFG 21%). Median and 1-year survival was 8.3 months (8.0 vs. 9.0 months) and 26% (17% vs. 32%). Median and 6-months progression-free survival was 5.0 months (4.5 vs. 5.0 months) and 34% (33% vs. 38%).

CONCLUSIONS

PEFG regimen in gemcitabine refractory pancreatic cancer had an acceptable toxicity profile and interesting activity, and may constitute a treatment option in this setting.

A phase II study of S-1 in gemcitabine-refractory metastatic pancreatic cancer

PURPOSE

Gemcitabine monotherapy or gemcitabine-containing combination chemotherapy is the standard first-line therapy for advanced pancreatic cancer. After disease progression, there is no standard regimen available. In a previous phase II trial, S-1 has been reported to show considerable efficacy, achieving a response rate of 37.5% in chemo-naïve patients with pancreatic cancer. This study evaluated the efficacy and toxicity of S-1 in patients with gemcitabine-refractory metastatic pancreatic cancer.

METHODS

Eligibility criteria were histologically proven pancreatic adenocarcinoma with confirmation of progressive disease while receiving gemcitabine-based first-line chemotherapy, 20-74 years of age, Karnofsky performance status of 80-100 points, with measurable metastatic lesions, adequate hematological, renal and liver functions, and written informed consent. S-1 was administered orally at 40 mg/m(2) twice daily for 28 days with a rest period of 14 days as one course. Administration was repeated until the appearance of disease progression or unacceptable toxicity. The primary endpoint of this study was an objective response, and secondary endpoints included toxicity, progression-free survival (PFS) and overall survival, as well as clinical benefit response in symptomatic patients.

RESULTS

Forty patients from two institutions were enrolled between September 2004 and November 2005. The most common adverse reactions were fatigue and anorexia, although most of those adverse reactions were tolerable and reversible. One patient developed grade 3 pneumonitis without neutropenia and recovered with appropriate antibiotic treatment. Although no complete response was seen, partial response was obtained in six patients (15, 95% confidence interval, 3.9-26%). Stable disease was noted in 17 patients (43%), and progressive disease in 15 patients (38%). Out of 19 evaluable patients, a clinical benefit response was observed in four patients (21%). The median PFS was 2.0 months, and the median survival time was 4.5 months with a 1-year survival rate of 14.1%.

CONCLUSION

S-1 as monotherapy had marginal anti-tumor activity with tolerable toxicity in patients with gemcitabine refractory metastatic pancreatic cancer.

The role of second-line chemotherapy after gemcitabine failure in patients with advanced pancreatic cancer

Systemic chemotherapy with single-agent gemcitabine or a gemcitabine-based regimen still remains a standard of care for the treatment of patients with locally advanced and metastatic pancreatic cancer. To date, no standard treatment approach for patients that show progressive disease during gemcitabine therapy is defined. Several clinical trials have evaluated the safety and efficacy of second-line chemotherapy after gemcitabine failure in this patient population. Based on the currently available data, there is increasing evidence that selected patients may derive clinical benefit from salvage chemotherapy, also with regard to survival. However, results from large randomized Phase III trials are still lacking and therefore no evidence-based treatment recommendation can be given for patients with advanced pancreatic cancer after failure of first-line gemcitabine.

Excess toxicity associated with docetaxel and irinotecan in patients with metastatic, gemcitabine-refractory pancreatic cancer: results of a phase II study

BACKGROUND

No therapeutic standard of care exists for patients with advanced pancreatic cancer who progress following first-line treatment with a gemcitabine-based regimen. There is evidence of synergistic activity between docetaxel and irinotecan, and the combination of these two agents has shown promising efficacy in the first-line setting for advanced pancreatic cancer. We, therefore, evaluated this regimen in patients with gemcitabine-refractory disease.

METHODS

Eligible patients with metastatic pancreatic adenocarcinoma were required to have an elevated serum CA19-9 (> 2x ULN) and exposure to one or two prior chemotherapy regimens, including one gemcitabine-based. Treatment consisted of docetaxel 65 mg/m2 and irinotecan 160 mg/m2, both administered every 21 days. Serum CA19-9 levels were measured at the start of each treatment cycle and CT scans performed after every two cycles.

RESULTS

Fourteen patients were enrolled before the study was closed due to excess toxicity. The most common grade 3/4 toxicities included neutropenia/leukopenia, nausea and vomiting, and diarrhea. Fully half of patients received only 1 treatment cycle, with a median time to treatment failure of 36 days. No objective responses were observed, although 3 patients had stable disease for at least 6 cycles. Overall survival for the entire cohort was 134 days, with a 6-month survival rate of 36%.

CONCLUSIONS

The combination of docetaxel and irinotecan given on a 21-day cycle is associated with excess toxicity in gemcitabine-refractory patients with advanced pancreatic cancer. Although select patients may benefit from treatment, the overall risk:benefit ratio is unfavorable, and other dosing regimens and therapeutic options should be explored in this setting.

Phase II study of rubitecan in recurrent or metastatic head and neck cancer

PURPOSE

Rubitecan is an oral camptothecin analogue that has shown activity against a broad spectrum of human tumor xenografts and has been tested in several diseases.

PATIENTS AND METHODS

In the present study, 19 patients with incurable, recurrent or metastatic head and neck cancer were treated with rubitecan at the initial dose of 1.5 mg/m(2) x 5 days per week. An appropriate dose modification program was set up according to the observed toxicities.

RESULTS

Thirteen out of the 19 treated patients were formally evaluable for tumor response. Ten patients had a disease progression and three patients had a stabilization of disease as their best response. The mean duration of stable disease was 141 days. Median survival was 16 weeks (range 2-22 weeks). Three patients died during the study or less than a month after their last dose of study medication. Hematologic toxicity was serious in this study since four patients discontinued their participation because of severe anemia. The drug was also associated with grade 1-4 neutropenia, and with 1-3 thrombocytopenia.

CONCLUSION

We conclude that rubitecan is not effective as a single-agent in recurrent or metastatic head and neck cancer with the doses and schedule used in this study.

Cytotoxic Therapy for Advanced Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is a highly lethal disease with anecdotal long-term survivorship when the disease is inoperable at presentation. A new era in the treatment of advanced pancreatic cancer commenced a decade ago with the advent of gemcitabine as a standard of care. While many large phase III trials have been conducted in the last 10 years, it has proved a difficult challenge to advance beyond the modest bar set by gemcitabine. For the most part, gemcitabine-combination cytotoxic studies have been negative where the principal end point has been overall survival with only a few noted exceptions; however, for vigorous individuals with bulky or symptomatic disease, a gemcitabine-based fluoropyrimidine or platinum combination is considered a standard of care and these data are reviewed in detail. In this new era of targeted therapy, the addition of erlotinib to gemcitabine has provided an alternate standard option to single-agent gemcitabine or gemcitabine-based cytotoxic combinations, a topic which will be discussed in a separate chapter. Other phase III studies of gemcitabine and bevacizumab and gemcitabine and cetuximab, respectively, which were both preliminarily reported as negative, have provided an indirect endorsement for the relative value of cytotoxic therapy in advanced pancreatic cancer. This underscores the major therapeutic hurdles that we have to surmount in this most challenging of human malignancies.

Rubitecan

The only approved camptothecins for use in patients to date (topotecan and irinotecan) are delivered intravenously. Thus, an oral camptothecin analogue that would provide the convenience of oral delivery with the flexibility for a variety of prolonged treatment schedules would be advantageous. Rubitecan is an orally available camptothecin analogue that also has potential for delivery transdermally or by inhalation. Like all of the camptothecins, its antitumour activity is mediated through the inhibition of DNA topoisomerase I, which is involved in relaxing supercoiled DNA, which is important for the process of DNA replication and RNA transcription. Rubitecan exists in equilibrium as 9-nitro-camptothecin (9-NC) and 9-amino-camptothecin (9-AC), a metabolite that is thought to be active although it failed in clinical trials. Both 9-NC and 9-AC contain a lactone ring that is required for optimal activity with the carboxylic acid (open ring) forms being significantly less active or inactive. A more acidic environment favours the lactone ring structure, whereas neutral or basic conditions favour the conversion to the carboxylic acid form. In addition to issues of lactone ring stability at physiological pH (true for all of the camptothecin analogues), there is pharmacokinetic variability that has had to be dealt with during the development of rubitecan. Preclinically, rubitecan has shown activity against a broad spectrum of tumour types in in vitro and in vivo human tumour xenograft models. Frustratingly, the level of activity of an agent in preclinical models has not always translated into similar activity against human tumours in clinical trials. To date, with the exception of pancreatic and possibly ovarian cancer, rubitecan has had disappointing activity against a number of other solid tumours in relatively small Phase I/II trials; however, it has shown sufficient activity against pancreatic cancer, a malignancy that remains difficult to treat, to continue to be evaluated in clinical trials for this indication. Results of clinical trials in the next few years should determine whether rubitecan can find a role in cancer therapy.

Chemotherapy for advanced pancreatic cancer

Single-agent gemcitabine was established as standard treatment for advanced pancreatic cancer after a superior clinical benefit response was demonstrated in a randomized study comparing it to 5-fluorouracil (FU). Until recently, many subsequent randomized trials of newer, often gemcitabine-based combinations have not been able to show improved survival over gemcitabine. Combination gemcitabine and capecitabine is likely to become the preferred standard treatment, at least in the UK, on the basis of the positive interim results of the UK National Cancer Research Institute (NCRI) randomized study of chemotherapy with this combination. At present, there is no standard second-line treatment for patients who have become refractory to gemcitabine, although a recently reported study has suggested that oxaliplatin with FU and leucovorin is superior to best supportive care in these patients. This article will review and discuss the clinical trials of chemotherapy for this disease, including the more recent trials, which have included the novel targeted agents.

A phase I study of concurrent 9-nitro-20(s)-camptothecin (9NC/Orathecin) and radiation therapy in the treatment of locally advanced adenocarcinoma of the pancreas

BACKGROUND AND PURPOSE

In vitro studies have suggested that 9-nitro-20(s)-Camptothecin (9NC/Orathecin/Rubitecan) can enhance the effects of radiation. We conducted a phase I study to assess the toxicity and determine the maximum tolerated dose of 9NC when combined with radiation in patients with locally advanced adenocarcinoma of the pancreas.

PATIENTS AND METHODS

Eleven patients with locally advanced adenocarcinoma of the pancreas received 9NC, orally during radiation. Radiation therapy consisted of 45 Gy in 25 fractions given over 5 weeks. The starting dose of 9NC was 1 mg/m2/day.

RESULTS

Eight patients received 9NC at a dose of 1 mg/m2/day and three patients received a dose of 1.25 mg/m2/day. Dose-limiting toxicity (DLT) was defined as >or=grade 3 non-hematologic toxicity and >or=grade 4 hematologic toxicity. Dose-limiting toxicity of grade 3 nausea/vomiting developed in one patient at the first dose level. At dose level 2, two of three patients developed DLT. Both developed grade 3 nausea, fatigue, and anorexia. Additionally, one of these patients had grade 3 dehydration and the other had grade 4 leukopenia, grade 3 vomiting, and grade 3 weakness.

CONCLUSIONS

9NC, 1 mg/m2/day, can be given concurrently with radiation with acceptable toxicity.

Human Multidrug Resistance Associated Protein 4 Confers Resistance to Camptothecins

PURPOSE

The multidrug resistance associated protein (MRP) 4 is a member of the adenosine triphosphate (ATP)-binding cassette transporter family. Camptothecins (CPTs) have shown substantial anticancer activity against a broad spectrum of tumors by inhibiting DNA topoisomerase I, but tumor resistance is one of the major reasons for therapeutic failure. P-glycoprotein, breast cancer resistance protein, MRP1, and MRP2 have been implicated in resistance to various CPTs including CPT-11 (irinotecan), SN-38 (the active metabolite of CPT-11), and topotecan. In this study, we explored the resistance profiles and intracellular accumulation of a panel of CPTs including CPT, CPT-11, SN-38, rubitecan, and 10-hydroxy-CPT (10-OH-CPT) in HepG2 cells with stably overexpressed human MRP4. Other anticancer agents such as paclitaxel, cyclophosphamide, and carboplatin were also included.

METHODS

HepG2 cells were transfected with an empty vehicle plasmid (V/HepG2) or human MRP4 (MRP4/HepG2). The resistance profiles of test drugs in exponentially growing V/HepG2 and MRP4/HepG2 cells were examined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazonium bromide (MTT) assay with 4 or 48 h exposure time of the test drug in the absence or presence of various MRP4 inhibitors. The accumulation of CPT-11, SN-38, and paclitaxel by V/HepG2 and MRP4/HepG2 cells was determined by validated high-performance liquid chromatography methods.

RESULTS

Based on the resistance folds from the MTT assay with 48 h exposure time of the test drug, MRP4 conferred resistance to CPTs tested in the order 10-OH-CPT (14.21) > SN-38 carboxylate (9.70) > rubitecan (9.06) > SN-38 lactone (8.91) > CPT lactone (7.33) > CPT-11 lactone (5.64) > CPT carboxylate (4.30) > CPT-11 carboxylate (2.68). Overall, overexpression of MRP4 increased the IC50 values 1.78- to 14.21-fold for various CPTs in lactone or carboxylate form. The resistance of MRP4 to various CPTs tested was significantly reversed in the presence of dl-buthionine-(S,R)-sulfoximine (BSO, a gamma-glutamylcysteine synthetase inhibitor), MK571, celecoxib, or diclofenac (all MRP4 inhibitors). In addition, the accumulation of CPT-11 and SN-38 over 120 min in MRP4/HepG2 cells was significantly reduced compared to V/HepG2 cells, whereas the addition of celecoxib, MK571, or BSO significantly increased their accumulation in MRP4/HepG2 cells. There was no significant difference in the intracellular accumulation of paclitaxel in V/HepG2 and MRP4/HepG2 cells, indicating that P-glycoprotein was not involved in the observed resistance to CPTs in this study. MRP4 also conferred resistance to cyclophosphamide and this was partially reversed by BSO. However, MRP4 did not increase resistance to paclitaxel, carboplatin, etoposide (VP-16), 5-fluorouracil, and cyclosporine.

CONCLUSIONS

Human MRP4 rendered significant resistance to cyclophosphamide, CPT, CPT-11, SN-38, rubitecan, and 10-OH-CPT. CPT-11 and SN-38 are substrates for MRP4. Further studies are needed to explore the role of MRP4 in resistance, toxicity, and pharmacokinetics of CPTs and cyclophosphamide.