In vitro evaluation of bendamustine induced apoptosis in B-chronic lymphocytic leukemia

Potential New Therapies "ROS-Based" in CLL: An Innovative Paradigm in the Induction of Tumor Cell Apoptosis

Chronic lymphocytic leukemia, in spite of recent advancements, is still an incurable disease; the majority of patients eventually acquire resistance to treatment through relapses. In all subtypes of chronic lymphocytic leukemia, the disruption of normal B-cell homeostasis is thought to be mostly caused by the absence of apoptosis. Consequently, apoptosis induction is crucial to the management of this illness. Damaged biological components can accumulate as a result of the oxidation of intracellular lipids, proteins, and DNA by reactive oxygen species. It is possible that cancer cells are more susceptible to apoptosis because of their increased production of reactive oxygen species. An excess of reactive oxygen species can lead to oxidative stress, which can harm biological elements like DNA and trigger apoptotic pathways that cause planned cell death. In order to upset the balance of oxidative stress in cells, recent therapeutic treatments in chronic lymphocytic leukemia have focused on either producing reactive oxygen species or inhibiting it. Examples include targets created in the field of nanomedicine, natural extracts and nutraceuticals, tailored therapy using biomarkers, and metabolic targets. Current developments in the complex connection between apoptosis, particularly ferroptosis and its involvement in epigenomics and alterations, have created a new paradigm.

Bendamustine: A review of pharmacology, clinical use and immunological effects (Review)

Bendamustine is an alkylating agent classified into the group of nitrogen mustard analogues, synthesized almost sixty years ago. It was registered in former East Germany in 1971 and approved by the US Food and Drug Administration in 2008 for treatment of chronic lymphocytic leukemia and indolent B-cell non-Hodgkin lymphoma. Considering its beneficial properties in the therapy of relapsed or refractory hematological malignancies, synergistic effects with other antineoplastic agents and increasing recent reports on its immunomodulatory effects, bendamustine has once again gained its justified attention. The uniqueness of bendamustine-mediated effects should be observed keeping in mind its distinctive structure with structural similarities to both alkylating agents and purine analogs. In the present review, the current knowledge on the use of bendamustine in oncology, its pharmacokinetics, mechanism of action and toxicity was summarized. In addition, its immune-modulating effects that have not been fully elucidated so far are emphasized, hoping to encourage further investigations of this unique drug.

Bendamustine in association with rituximab for first-line treatment of diffuse large B-cell lymphoma in frail patients ineligible for R-CHOP/R-CHOP-like treatments

R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) has been considered the standard of care for diffuse large B cell lymphoma (DLBCL) patients, including in the elderlies, and represent the current standard treatment. Ineligibility for R-CHOP-like treatments seems to be associated with shorter survival. Recent studies have shown that bendamustine and rituximab is linked, in elderly patients affected by DLBCL. Here we report our experience with BR in 40 elderly frail patients affected by DLBCL ineligibles for R-CHOP. The OOR was 77.5%, with 22 complete responses and 9 partial responses statistical analysis showed no significant difference in overall survival (OS) between patients aged 80 years and older and patients younger than 80 years (6·4 vs. 10·2 months, respectively, P = 0·43). Complete responders were more likely patients with good performance status, (ECOG 0-1) 13 patients (60%), 9 patients (40%) were ECOG 2; of the 9 patients who achieved partial response, 7 patients had ECOG 0-1 and 2 patients had ECOG 2. Four patients had stable disease. Progression-free survival (PFS) median PFS was 13.5 months. These preliminary results showed that bendamustine and rituximab has been associated with high response rates, acceptable toxicity in frail DLBCL patients and high rate of OSS. In older patients with advanced IPI scores, no significant difference in OS were observed between patients aged 80 years and older and patients younger than 80 years. We conclude that bendamustine and rituximab seems to be a reasonable alternative for frail DLBCL patients.

Bendamustine alone or with rituximab modifies expression of apoptosis-regulating genes and proteins of CLL cells, depending on IGVH mutational status

We studied whether bendamustine (BENDA) alone or with rituximab (RIT) modifies in vitro expression of apoptosis-involved genes and proteins of chronic lymphocytic leukemia (CLL) cells depending on IGVH mutational status. Circulating lymphocytes from 34 untreated patients (18 IGVH-MUT and 16 IGVH-UNMUT) were incubated with above drugs to evaluate proteins expression. Microarray analysis of 93 genes was performed in 14 patients. BENDA and BENDA + RIT increased expression of BAX and BBC3 in IGVH-MUT and IGVH-UNMUT groups, and significant differences in expression of above genes after BENDA + RIT were observed between both groups. Additionally, BENDA + RIT decreased NFκB and BCL-2 genes in IGVH-UNMUT patients and increased expression of P53, BAX and PUMA proteins in IGVH-MUT and UNMUT subjects. However, no significant differences were found between these groups. In conclusion, BENDA + RIT modified gene expression profile in CLL cells and affected expression of some apoptosis-regulating proteins in vitro. Expression of BAX and BBC3 depends on action of drugs and IGVH mutational status.

BENDAMUSTINE: AN OLD DRUG IN THE NEW ERA FOR PATIENTS WITH NON-HODGKIN LYMPHOMAS AND CHRONIC LYMPHOCYTIC LEUKEMIA

- The aim of this review is to present data on bendamustine, a non-cross resistant alkylating agent, alone or in combination for treatment of non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL). Bendamustine is currently approved for rituximab-resistant indolent NHL and CLL in patients not fit for conventional chemotherapy. Recent studies have shown superiority of bendamustine combination with rituximab (B-R) in first line treatment of indolent NHLs and mantle cell lymphoma, suggesting a shift of the standard of care in this setting. B-R regimen has also shown efficacy in relapsed setting suggesting the possible treatment option for patients failing conventional chemotherapy. In rituximab-resistant NHL, the recent GADOLIN study exploring the addition of obinutuzumab to bendamustine has yielded impressive result changing the standard of care in this hard-to-treat population. Concerning CLL, despite inferiority to the standard of care in young fit patients, as defined in CLL10 study, B-R has yielded a more beneficial toxicity profile and its use in first line treatment should be decided individually. In relapsed setting, the addition of ibrutinib to B-R has shown superior results compared to B-R alone, possibly changing the paradigm of treatment of relapsed CLL. In conclusion, bendamustine as a single agent or in combinations has shown activity with acceptable toxic profile in the treatment of patients with indolent NHLs or CLL without del(17p) mutation.

Inhibition of STAT3 by Anticancer Drug Bendamustine

Bendamustine (BENDA), which bears the bis(2-chloroethyl)amino moiety, is an alkylating agent that stops the growth of cancer cells by binding to DNA and interfering with its replication. However, the mechanism of action underlying its excellent clinical efficacy remains unclear. In this work, we report that BENDA inhibits signal transducer and activator of transcription 3 (STAT3). In an AlphaScreen-based biochemical assay using recombinant human STAT3, binding of STAT3-Src homology 2 (SH2) to the phosphotyrosine (pTyr, pY) peptide was inhibited by BENDA but not by the inactive metabolite dihydroxy bendamustine (HP2). When a single point mutation of C550A or C712A was introduced into recombinant human STAT3, its sensitivity to BENDA was substantially reduced, suggesting that these cysteine residues are important for BENDA to inhibit STAT3. Furthermore, BENDA suppressed the function of cellular STAT3 as a transcriptional activator in a human breast cancer cell line, MDA-MB-468, with constitutively activated STAT3. A competitive pull-down assay using biotinylated BENDA (Bio-BENDA) revealed that BENDA bound tightly to cellular STAT3, presumably through covalent bonds. Therefore, our results suggest that the anticancer effects of BENDA may be associated, at least in part, with its inhibitory effect on the SH2 domain of STAT3.

CD69 expression potentially predicts response to bendamustine and its modulation by ibrutinib or idelalisib enhances cytotoxic effect in chronic lymphocytic leukemia

Clinical responses to bendamustine in chronic lymphocytic leukemia (CLL) are highly heterogeneous and no specific markers to predict sensitivity to this drug have been reported. In order to identify biomarkers of response, we analyzed the in vitro activity of bendamustine and the gene expression profile in primary CLL cells. We observed that mRNA expression of CD69 (CD69) and ITGAM (CD11b) constitute the most powerful predictor of response to bendamustine. When we interrogated the predictive value of the corresponding cell surface proteins, the expression of the activation marker CD69 was the most reliable predictor of sensitivity to bendamustine. Importantly, a multivariate analysis revealed that the predictive value of CD69 expression was independent from other clinico-biological CLL features. We also showed that when CLL cells were co-cultured with distinct subtypes of stromal cells, an upregulation of CD69 was accompanied by a reduced sensitivity to bendamustine. In agreement with this, tumor cells derived from lymphoid tumor niches harbored higher CD69 expression and were less sensitive to bendamustine than their peripheral blood counterparts. Furthermore, pretreatment of CD69 ^high CLL cases with the B-cell receptor (BCR) pathway inhibitors ibrutinib and idelalisib decreased CD69 levels and enhanced bendamustine cytotoxic effect. Collectively, our findings indicate that CD69 could be a predictor of bendamustine response in CLL patients and the combination of clinically-tested BCR signaling inhibitors with bendamustine may represent a promising strategy for bendamustine low responsive CLL cases.

Determination of Bendamustine in Human Plasma and Urine by LC-FL Methods: Application in a Drug Monitoring

Simple and sensitive liquid chromatography (LC) methods with fluorescence (FL) detection for the determination of bendamustine (BM) in human plasma and urine were developed and validated. The procedure of BM extraction from a plasma sample involved solid-phase extraction with a C18 SPE column, while liquid–liquid extraction with dichloromethane was applied for a urine sample. In both methods, cinoxacin was used as the internal standard. Chromatographic separations were performed on a Synergi Max-RP column, while FL detector was set at the excitation wavelength of 328 nm and the emission wavelength of 420 nm. The LC-FL methods were validated for accuracy, precision, selectivity, linearity, recovery, and stability. The detection limits for BM were 0.5 and 2.5 ng mL⁻¹ in plasma and urine, respectively. The intra-day and inter-day precisions were less than 9.86 %, while the accuracies were higher than 92.63 and 94.29 % for BM in plasma and urine, respectively. The proposed LC-FL methods were sensitive, robust, and specific, allowing reliable drug quantification in plasma and urine samples. The methodologies were successfully applied to monitoring of BM in a child with cancer treated with BM.

The combination effects of bendamustine with antimetabolites against childhood acute lymphoblastic leukemia cells

Bendamustine combined with other drugs is clinically efficacious for some adult lymphoid malignancies, but to date there are no reports of the use of such combinatorial approaches in pediatric patients. We investigated the in vitro activity of bendamustine combined with other antimetabolite drugs on B cell precursor acute lymphoblastic leukemia (BCP-ALL) cell lines established from pediatric patients with refractory or relapsed ALL. We also developed a mathematically drown improved isobologram method to assess the data objectively. Three BCP-ALL cell lines; YCUB-2, YCUB-5, and YCUB-6, were simultaneously exposed to various concentrations of bendamustine and cladribine, cytarabine, fludarabine, or clofarabine. Cell growth inhibition was determined using the WST-8 assay. Combinatorial effects were estimated using our improved isobologram method with IC80 (drug concentration corresponding to 80 % of maximum inhibition). Bendamustine alone inhibited ALL cell growth with mean IC80 values of 11.30-18.90 μg/ml. Combinations of bendamustine with other drugs produced the following effects: (1) cladribine; synergistic-to-additive on all cell lines; (2) cytarabine; synergistic-to-additive on YCUB-5 and YCUB-6, and synergistic-to-antagonistic on YCUB-2; (3) fludarabine; additive-to-antagonistic on YCUB-5, and synergistic-to-antagonistic on YCUB-2 and YCUB-6; (4) clofarabine; additive-to-antagonistic on all cell lines. Flow cytometric analysis also showed the combination effects of bendamustine and cladribine. Bendamustine/cladribine or bendamustine/cytarabine may thus represent a promising combination for salvage treatment in childhood ALL.

Sensitivity of chronic lymphocytic leukemia cells to small targeted therapeutic molecules: An in vitro comparative study

New drugs targeting important cellular signaling pathways are currently being developed for chronic lymphocytic leukemia (CLL). It is therefore of interest to analyze their in vitro killing capacity in manufacturer-independent, comparative experiments. We here report on the sensitivity of CLL cells to a panel of emerging targeted therapeutics using high-throughput screening based on an automated fluorescence digital scanning system. Fresh CLL cells from 42 patients with indolent or progressive CLL were cultured for 72 hours on microtiter plates in a unique primary cell culture medium. Antitumor effects of 31 small therapeutic molecules (and, as controls, 29 cytostatic agents) at equimolar concentration were compared in a fluorescence survival assay. In vitro sensitivity to each drug exhibited considerable interpatient variability. The highest mean direct killing was observed for one survivin inhibitor (YM-155), two bcl-2 inhibitors (ABT-199, ABT-737), and one selective CDK inhibitor (dinaciclib). Their killing capacity was, in contrast to most cytostatic agents, similarly high in refractory versus untreated CLL patients and was significantly higher on cells with the 17p deletion/TP53 mutation than on cells with other cytogenetic abnormalities (p = 0.02). Sensitivity of bone marrow and lymph node cells was highly correlated with that of blood cells. Even though direct killing may not be the only therapeutic effector function in vivo, results from this head-to-head comparison may help to identify drugs of particular interest for intensified clinical development.

Synthesis and Antiproliferative Activities of Benzimidazole-Based Sulfide and Sulfoxide Derivatives

The design, synthesis, and in vitro antiproliferative activity of a novel series of sulfide (4a-i) and sulfoxide (5a-h) derivatives of benzimidazole, in which different aromatic and heteroaromatic acetamides are linked to benzimidazole via sulfide (4a-i) and sulfoxide (5a-h) linker, are reported and the structure-activity relationship is discussed. The new derivatives were prepared by coupling 2-(mercaptomethyl)benzimidazole with 2-bromo-N-(substituted) acetamides in dry acetone in the presence of anhydrous potassium carbonate. With very few exceptions, all of the synthesized compounds showed varying antiprolific activities against HepG2, MCF-7, and A549 cell lines. Compound 5a was very similar in potency to doxorubicin as an anticancer drug, with IC50 values 4.1 ± 0.5, 4.1 ± 0.5, and 5.0 ± 0.6 µg/mL versus 4.2 ± 0.5, 4.9 ± 0.6, and 6.1 ± 0.6 µg/mL against HepG2, MCF-7, and A549 cell lines, respectively. In contrast, none of the compounds showed activity against human prostate PC3 cancer cells. Additionally, the sulfoxide derivatives were more potent than the corresponding sulfides.

Treatment of chronic lymphocytic leukemia with bendamustine in an HIV-infected patient on antiretroviral therapy: a case report and review of the literature

Few reports have described the coincidence of chronic lymphocytic leukemia (CLL) and HIV. We administered bendamustine to an HIV-positive refractory CLL patient and obtained a significant objective response. Our results indicate that bendamustine can be used in HIV-infected CLL patients. We also reviewed 12 cases of CLL with HIV infection.

Pharmacokinetic and pharmacodynamic profile of bendamustine and its metabolites

Purpose

Bendamustine is a unique alkylating agent indicated for the treatment of chronic lymphocytic leukemia and rituximab-refractory, indolent B cell non-Hodgkin’s lymphoma. Despite the extensive experience with bendamustine, its pharmacokinetic profile has only recently been described. This overview summarizes the pharmacokinetics, pharmacokinetic/pharmacodynamic relationships, and drug–drug interactions of bendamustine in adult and pediatric patients with hematologic malignancies.

Methods

A literature search and data on file (including a human mass balance study, pharmacokinetic population analyses in adult and pediatric patients, and modeling analyses) were evaluated for inclusion.

Results

Bendamustine concentrations peak at end of intravenous infusion (~1 h). Subsequent elimination is triphasic, with the intermediate t_1/2 (~40 min) as the effective t_1/2 since the final phase represents <1 % of the area under the curve. Bendamustine is rapidly hydrolyzed to monohydroxy-bendamustine and dihydroxy-bendamustine, which have little or no activity. Cytochrome P450 (CYP) 1A2 oxidation yields the active metabolites γ-hydroxybendamustine and N-desmethyl-bendamustine, at low concentrations, which contribute minimally to cytotoxicity. Minor involvement of CYP1A2 in bendamustine elimination suggests a low likelihood of drug–drug interactions with CYP1A2 inhibitors. Systemic exposure to bendamustine 120 mg/m² is comparable between adult and pediatric patients; age, race, and sex have been shown to have no significant effect on systemic exposure in either population. The effect of hepatic/renal impairment on bendamustine pharmacokinetics remains to be elucidated. Higher bendamustine concentrations may be associated with increased probability of nausea or infection. No clear exposure–efficacy response relationship has been observed.

Conclusions

Altogether, the findings support dosing based on body surface area for most patient populations.

Effects of rhamnocitrin 4-β-D-galactopyranoside, isolated from Astragalus hamosus on toxicity models in vitro

BACKGROUND

Astragalus hamosus L. (Fabaceae) is used in herbal medicine as emollient, demulcent, phrodisiac, diuretic, laxative, and good for inflammation, ulcers, and leukoderma. It is useful in treating irritation of the mucous membranes, nervous affections, and catarrh.

OBJECTIVE

Rhamnocitrin 4-β-D-galactopyranoside (RGP), isolated from A. hamosus, was investigated for its possible protective effect on different models of toxicity in vitro on sub-cellular and cellular level.

MATERIALS AND METHODS

The effects of RGP were evaluated on isolated rat brain synaptosomes, prepared by Percoll reagent and on rat hepatocytes, isolated by two-stepped collagenase perfusion.

RESULTS

In synaptosomes, RGP had statistically significant protective effect, similar to those of silymarin, on 6-hydroxy (OH)-dopamine-induced oxidative stress. These results correlate with literature data about protective effects of kempferol and rhamnocitrin on oxidative damage in rat pheochromocytoma PC12 cells. In rat hepatocytes, we investigate the effect of RGP on two models of liver toxicity: Bendamustine and cyclophosphamide. In these models, the compound had statistically significant cytoprotective and antioxidant activity, similar to those of silymarin.

CONCLUSION

According to these results, we can suggest that such cytoprotective effect of RGP might be due to an influence on bendamustine and cyclophosphamide metabolism in rat hepatocytes. In isolated rat hepatocytes, in combination with bendamustine and cyclophosphamide and in 6-OH-dopamine-induced oxidative stress in isolated rat synaptosomes, RGP, isolated from A. hamosus, was effective protector and antioxidant. The effects were closed to those of flavonoid silymarin-the classical hepatoprotector and antioxidant.

Pharmacokinetic profile and first preliminary clinical evaluation of bendamustine in Taiwanese patients with heavily pretreated indolent B-cell non-Hodgkin lymphoma and mantle cell lymphoma

Prior studies found bendamustine is efficacious in patients with indolent B-cell non-Hodgkin lymphoma (NHL). To date, no studies have reported the efficacy of bendamustine in a Chinese population. This multicentre phase II trial evaluated the pharmacokinetics (PK), safety and efficacy of bendamustine monotherapy in Chinese patients in Taiwan with pretreated indolent B-cell NHL or mantle cell lymphoma (MCL). For PK assessments, patients were randomized (n = 16; 11 with indolent B-cell NHL and five with MCL) to 90 or 120 mg/m(2) of bendamustine for the first cycle. Plasma levels of bendamustine and its two metabolites were analyzed. For efficacy and safety evaluations, bendamustine 120 mg/m(2) was given to all patients every 3 weeks starting at cycle 2 for a minimum of a total of six cycles. The median age of patients was 61.7 years, and the majority were men (75%). The median number of prior treatments was 4 (range, 1-9 regimens), and all patients were previously treated with rituximab. Bendamustine plasma concentration peaked near the end of infusion and was rapidly eliminated with a mean elimination half-life (t(1/2)) of 0.67-0.8 h. Of the evaluable patients (n = 14), the overall response rate was 78.6%, including 7.2% of patients having a complete response. Mean progression-free survival was 27.5 weeks. The most common grade 3-4 adverse events were leucopenia (56.3%), neutropenia (56.3%) and thrombocytopenia (25%). In conclusion, bendamustine was efficacious and well tolerated in Taiwanese patients with indolent NHL and MCL with a similar PK profile to that of other populations.

Evaluation of bendamustine in combination with fludarabine in primary chronic lymphocytic leukemia cells

The fludarabine and cyclophosphamide couplet has become the backbone of the chronic lymphocytic leukemia (CLL) standard of care. Although this is an effective treatment, it results in untoward toxicity. Bendamustine is a newly approved and better-tolerated alkylating agent. We hypothesized that similar to cyclophosphamide, bendamustine-induced DNA damage will be inhibited by fludarabine, resulting in increased cytotoxicity. To test this hypothesis and the role of the stromal microenvironment in this process, we treated CLL lymphocytes in vitro with each drug alone and in combination. Simultaneous or prior addition of fludarabine to bendamustine resulted in maximum cytotoxicity assayed by 3,3'-dihexyloxacarbocyanine iodine negativity, annexin positivity, and poly (adenosine 5'-diphosphate-ribose) polymerase cleavage. Cytotoxicity elicited by combination of both agents was similar in these malignant B cells cultured either in suspension or on marrow stroma cells. Cell death was associated with DNA damage response, which was determined by phosphorylation of H2AX and unscheduled DNA synthesis. H2AX activation was maximum with the drug combination, and unscheduled DNA synthesis induced by bendamustine was blocked by fludarabine. In parallel, ATM, Chk2, and p53 were phosphorylated and PUMA was induced. Cell death was caspase independent; however, caspases did decrease levels of Mcl-1 survival protein. These data provide a rationale for combining fludarabine with bendamustine for patients with CLL.

Purine analog-like properties of bendamustine underlie rapid activation of DNA damage response and synergistic effects with pyrimidine analogues in lymphoid malignancies

Bendamustine has shown considerable clinical activity against indolent lymphoid malignancies as a single agent or in combination with rituximab, but combination with additional anti-cancer drugs may be required for refractory and/or relapsed cases as well as other intractable tumors. In this study, we attempted to determine suitable anti-cancer drugs to be combined with bendamustine for the treatment of mantle cell lymphoma, diffuse large B-cell lymphoma, aggressive lymphomas and multiple myeloma, all of which are relatively resistant to this drug, and investigated the mechanisms underlying synergism. Isobologram analysis revealed that bendamustine had synergistic effects with alkylating agents (4-hydroperoxy-cyclophosphamide, chlorambucil and melphalan) and pyrimidine analogues (cytosine arabinoside, gemcitabine and decitabine) in HBL-2, B104, Namalwa and U266 cell lines, which represent the above entities respectively. In cell cycle analysis, bendamustine induced late S-phase arrest, which was enhanced by 4-hydroperoxy-cyclophosphamide, and potentiated early S-phase arrest by cytosine arabinoside (Ara-C), followed by a robust increase in the size of sub-G1 fractions. Bendamustine was able to elicit DNA damage response and subsequent apoptosis faster and with shorter exposure than other alkylating agents due to rapid intracellular incorporation via equilibrative nucleoside transporters (ENTs). Furthermore, bendamustine increased the expression of ENT1 at both mRNA and protein levels and enhanced the uptake of Ara-C and subsequent increase in Ara-C triphosphate (Ara-CTP) in HBL-2 cells to an extent comparable with the purine analog fludarabine. These purine analog-like properties of bendamustine may underlie favorable combinations with other alkylators and pyrimidine analogues. Our findings may provide a theoretical basis for the development of more effective bendamustine-based combination therapies.

Poly(ADP-ribose) polymerase inhibitor CEP-8983 synergizes with bendamustine in chronic lymphocytic leukemia cells in vitro

DNA repair aberrations and associated chromosomal instability is a feature of chronic lymphocytic leukemia (CLL). To evaluate if DNA repair insufficiencies are related to methylation changes, we examined the methylation of nine promoter regions of DNA repair proteins by bisulfide sequencing in 26 CLL primary samples and performed quantitative PCR on a subset of samples to examine BRCA1 expression. We also investigated if changes in cytogenetic or expression level of DNA repair proteins led to changes in sensitivity to a novel PARP inhibitor, CEP-8983, alone and in combination with bendamustine. No changes in promoter methylation were identified in BRCA1, BRCA2, FANC-C, FANC-F, FANC-L, ATM, MGMT, hMLH1 and H2AX except for two cases of minor BRCA1 hypermethylation. CLL samples appeared to have reduced BRCA1 mRNA expression uniformly in comparison to non-malignant lymphocytes irrespective of promoter hypermethylation. CEP-8983 displayed single agent cytotoxicity and the combination with bendamustine demonstrated synergistic cytotoxicity in the majority of CLL samples. These results were consistent across cytogenetic subgroups, including 17p deleted and previously treated patients. Our results provide rationale for further exploration of the combination of a PARP inhibitor and DNA damaging agents as a novel therapeutic strategy in CLL.

The role of chemotherapy in managing chronic lymphocytic leukemia: optimizing combinations with targeted therapy

For many years, alkylating agents were the standard treatment for chronic lymphocytic leukemia (CLL). The advent of purine analogs improved response rates, but not overall survival, and although the monoclonal antibody rituximab is generally active against B-cell malignancies, it has demonstrated limited benefits as monotherapy for the treatment of CLL. However, specific combinations of chemotherapy, antibodies and targeted therapies have demonstrated additive or synergistic activity in CLL cells and deliver substantial clinical benefits. A greater understanding of the actions of chemotherapies and targeted agents on cellular pathways will advance the development of rationally designed combinations corresponding to individual patients' disease profiles.

Bendamustine for treatment of chronic lymphocytic leukemia

INTRODUCTION

Chronic lymphocytic leukemia (CLL) often has an extended disease course. With a median age at diagnosis of 72 years, newer treatment options with less toxicity than standard nucleoside analogue-based regimens are needed. Historically, few therapy options are available once CLL has become refractory to nucleoside analogues. Bendamustine has emerged as a feasible therapy for older and less fit CLL patients, with clinical efficacy in previously untreated and refractory CLL.

AREAS COVERED

This paper reviews several of the pivotal clinical trials that established the clinical activity of bendamustine in previously untreated and relapsed/refractory CLL. The toxicity profile of bendamustine, primarily myelosuppression and infections, is reviewed and compared across different CLL populations. A review of the clinical data focuses on potential explanations for differences in response rates and duration of remission reported across studies and how this may impact the development of therapies for CLL.

EXPERT OPINION

Bendamustine is a valuable new agent for the management of CLL. Ongoing clinical trials are comparing bendamustine with standard CLL regimens in untreated disease, and investigating bendamustine combinations with novel targeted therapies and monoclonal antibodies. These studies will help to define the optimal role for bendamustine in CLL management.

Dose dependent effects on cell cycle checkpoints and DNA repair by bendamustine

Bendamustine (BDM) is an active chemotherapeutic agent approved in the U. S. for treating chronic lymphocytic leukemia and non-Hodgkin lymphoma. Its chemical structure suggests it may have alkylator and anti-metabolite activities; however the precise mechanism of action is not well understood. Here we report the concentration-dependent effects of BDM on cell cycle, DNA damage, checkpoint response and cell death in HeLa cells. Low concentrations of BDM transiently arrested cells in G2, while a 4-fold higher concentration arrested cells in S phase. DNA damage at 50, but not 200 µM, was efficiently repaired after 48 h treatment, suggesting a difference in DNA repair efficiency at the two concentrations. Indeed, perturbing base-excision repair sensitized cells to lower concentrations of BDM. Timelapse studies of the checkpoint response to BDM showed that inhibiting Chk1 caused both the S- and G2-arrested cells to prematurely enter mitosis. However, whereas the cells arrested in G2 (low dose BDM) entered mitosis, segregated their chromosomes and divided normally, the S-phase arrested cells (high dose BDM) exhibited a highly aberrant mitosis, whereby EM images showed highly fragmented chromosomes. The vast majority of these cells died without ever exiting mitosis. Inhibiting the Chk1-dependent DNA damage checkpoint accelerated the time of killing by BDM. Our studies suggest that BDM may affect different biological processes depending on drug concentration. Sensitizing cells to killing by BDM can be achieved by inhibiting base-excision repair or disrupting the DNA damage checkpoint pathway.

Role of stromal cell-mediated Notch signaling in CLL resistance to chemotherapy

Stromal cells are essential components of the bone marrow (BM) microenvironment that regulate and support the survival of different tumors, including chronic lymphocytic leukemia (CLL). In this study, we investigated the role of Notch signaling in the promotion of survival and chemoresistance of human CLL cells in coculture with human BM-mesenchymal stromal cells (hBM-MSCs) of both autologous and allogeneic origin. The presence of BM-MSCs rescued CLL cells from apoptosis both spontaneously and following induction with various drugs, including Fludarabine, Cyclophosphamide, Bendamustine, Prednisone and Hydrocortisone. The treatment with a combination of anti-Notch-1, Notch-2 and Notch-4 antibodies or γ-secretase inhibitor XII (GSI XII) reverted this protective effect by day 3, even in presence of the above-mentioned drugs. Overall, our findings show that stromal cell-mediated Notch-1, Notch-2 and Notch-4 signaling has a role in CLL survival and resistance to chemotherapy. Therefore, its blocking could be an additional tool to overcome drug resistance and improve the therapeutic strategies for CLL.

Cytosine arabinoside potentiates the apoptotic effect of bendamustine on several B- and T-cell leukemia/lymphoma cells and cell lines

Bendamustine and cytosine arabinoside (ara-c) are commonly used cytotoxic agents with unique mechanisms of action. We have previously reported a striking additive cytotoxic effect of the consecutive combination of bendamustine and ara-c in mantle cell lymphoma (MCL) cell lines. In the present study, cell lines of follicular lymphoma (DOHH-2), chronic lymphocytic leukemia/lymphoma (EHEB), diffuse large B-cell lymphoma (SU-DHL-4), T-cell leukemia/lymphoma (JURKAT and KARPAS-299) and MCL (JEKO-1 and GRANTA-519) were exposed to the two single drugs or the drugs combined, given simultaneously and consecutively. Peripheral blood chronic lymphocytic leukemia (CLL) B-cells from five patients were also analyzed. Apoptosis, cell proliferation/metabolic activity and mitochondrial damage were evaluated. The combination index (CI) was used to assess synergy between the drugs. Bendamustine exhibited a relevant cytotoxic effect that was dose- and time-dependent, except for SU-DHL-4 and T-cell lymphoma cells. The addition of ara-c after bendamustine significantly potentiated the single-drug cytotoxic effect of bendamustine on all cell lines, including 17p - CLL B-cells, JURKAT and SU-DHL-4, the latter presenting the highest synergism (CI < 0.01). Bendamustine and ara-c are highly synergistic on T- and B-cell lymphoma cells and cell lines, similar to MCL, overcoming resistance to the single agents.

Bendamustine HCL for the treatment of relapsed indolent non-Hodgkin's lymphoma

Bendamustine is an alkylating agent which also shows properties of a purine analog. Because of its unique mechanism of action it shows activity in relapsed indolent lymphomas which are resistant to alkylating agents, purine analogs, and rituximab. Bendamustine has a favorable toxicity profile causing no alopecia and only a moderate hematotoxicity and gastrointestinal toxicity. Combinations of bendamustine with mitoxantrone and rituximab and with rituximab alone have been shown to be highly active in relapsed/refractory indolent lymphomas and mantle cell lymphomas achieving long lasting complete remissions. Because of only moderate toxicity these combinations can be applied safely in elderly patients who can be treated in an outpatient setting.

The cytotoxic effects of bendamustine in combination with cytarabine in mantle cell lymphoma cell lines

Bendamustine is clinically useful in mantle-cell lymphoma (MCL). Its favorable toxicity profile in-vivo favors its combination with other cytotoxic drugs. Cytarabine is a key drug in the treatment of younger patients with MCL. The current study investigated the in-vitro cytotoxic effect of bendamustine and cytarabine, alone or combined, on two MCL cell lines representing the classic and blastoid variant of the lymphoma subtype (JEKO-1 and GRANTA-519). Cell lines were exposed to each drug alone, or simultaneously and consecutively to both drugs, for different time schedules. Apoptosis was measured by flow cytometry. Mitochondrial damage, cell proliferation/metabolic activity, and cell cycle analysis were also assessed. The synergistic, additive, or antagonistic effects of the drugs were calculated with the combination index (CI) method. Bendamustine and cytarabine alone exhibited relevant cytotoxic activity on both cell lines. Both drugs induced cell cycle arrest in S phase. Drug combinations were associated with significantly higher cytotoxic effects than each drug alone. Among the combination schedules, the consecutive incubation of bendamustine followed by cytarabine was associated with the lower CI, being 10-100-fold lower than with simultaneous incubations. The cytotoxic effect of the consecutive combination was prominent on both cell lines, indicating a very strong and highly significant synergy in inducing apoptosis. Similar results were obtained measuring mitochondrial damage or the decline of the metabolic activity in all cell lines. The strong synergistic effect of bendamustine and cytarabine on MCL cells provides a rationale for developing schedules combining these agents in the treatment of MCL.

Mechanism of action: the unique pattern of bendamustine-induced cytotoxicity

Bendamustine has demonstrated substantial efficacy in the treatment of hematologic malignancies and continues to distinguish itself from other alkylating agents with regard to its activity in tumor cells. The mechanistic and clinical differences associated with bendamustine may be directly related to its unique structural features. Although the precise mechanisms of action are still poorly understood, bendamustine is associated with extensive and durable DNA damage. The increased potency of bendamustine may be due to secondary mechanisms such as inhibition of mitotic checkpoints, inefficient DNA repair, and initiation of p53-dependent DNA-damage stress response, all of which lead to mitotic catastrophe and apoptosis. It has also been hypothesized that the presence of a benzimidazole ring in addition to the nitrogen mustard group may influence the way bendamustine interacts with DNA and/or confer antimetabolite properties. Further elucidation of the mechanisms of action for bendamustine and the signaling pathways involved in the response to bendamustine-induced DNA damage is essential to maximize its therapeutic potential, identify biomarkers for response, and understand the potential for synergy with other agents involved in DNA damage and inhibition of DNA repair. This review will discuss the current understanding and hypotheses regarding bendamustine mechanisms of action and suggest future investigations that would shed light on the many unanswered questions.

Bendamustine: a review of its use in the management of indolent non-Hodgkin's lymphoma and mantle cell lymphoma

Bendamustine (bendamustine hydrochloride) is an alkylating agent indicated in several countries for the treatment of indolent non-Hodgkin's lymphoma (NHL) and mantle cell lymphoma (MCL). While the precise mechanism of action of bendamustine is as yet unknown, it has limited cross resistance to other alkylating agents and appears to exert its antineoplastic effects via a different mechanism to that of other alkylating agents. Bendamustine monotherapy was effective in treatment-refractory (including rituximab-refractory) indolent NHL or MCL. Moreover, bendamustine-based combination treatment was at least as effective as cyclophosphamide-based treatment, and bendamustine plus rituximab was at least as effective as cyclophosphamide, doxorubicin, vincristine plus prednisone (CHOP) plus rituximab, as first-line therapy in patients with indolent NHL or MCL. Treatment-refractory disease also appeared to respond favourably to bendamustine-containing combination treatment. In general, bendamustine was associated with a high overall response rate and a durable response. The most common adverse events associated with bendamustine were haematological or gastrointestinal in nature, and most were of mild to moderate severity. Regimens that included bendamustine were also associated with a very low rate of alopecia compared with regimens that included other antineoplastic drugs. In conclusion, bendamustine is a unique alkylating agent, which in clinical trials has demonstrated consistent efficacy and acceptable tolerability in patients with indolent NHL or MCL. It may be a particularly useful treatment option in patients with rituximab-refractory disease, but has also demonstrated efficacy as part of a first-line combination treatment. While further research is necessary to firmly establish the best place for bendamustine in the management of indolent NHL and MCL, it is a valuable addition to the pool of available treatments for these diseases.

Bendamustine: a new treatment option for chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a slow-growing hematologic malignancy and the most common type of leukemia in the western world. The lifetime risk for developing CLL is 1 in 216 men and women. Unfortunately, CLL is considered incurable with the chemotherapeutic agents available today. Bendamustine is a new agent that was recently added to the available regimens for the treatment of CLL. It was also recently approved for the treatment of non-Hodgkin's lymphoma. Its mechanism of action is unknown, but it contains an alkylating group similar to that of other bifunctional alkylating agents such as chlorambucil, and it also contains a benzimidazole central ring thought to exhibit antipurine-like properties. The United States Food and Drug Administration approved bendamustine based on results from an international phase III study of CLL in which bendamustine was compared with chlorambucil in treatment-naïve patients. Ongoing clinical trials are assessing the utility of bendamustine in combination with other agents for the treatment of CLL, as well as for other malignancies.

Bendamustine for the treatment of chronic lymphocytic leukemia and rituximab-refractory, indolent B-cell non-Hodgkin lymphoma

BACKGROUND

Bendamustine is a mechlorethamine derivative with a purine-like benzimidazole ring, which may enhance its clinical efficacy. Bendamustine was approved by the US Food and Drug Administration (FDA) for the treatment of chronic lymphocytic leukemia (CLL) in March 2008 and for the treatment of rituximab-refractory, indolent B-cell non-Hodgkin lymphoma (NHL) in October 2008.

OBJECTIVE

This article reviews the pharmacologic and pharmacodynamic properties of bendamustine, together with data on efficacy and toxicity from trials investigating the use of bendamustine for the treatment of various hematologic malignancies, including CLL, NHL, and multiple myeloma (MM).

METHODS

MEDLINE and International Pharmaceutical Abstracts (1970-April 15, 2009) were searched using the terms bendamustine, bendamustin, Treanda, Ribomustin, SDX-105, IMET-3393, and Cytostasan. References from relevant articles were also reviewed for additional sources and material. The databases of the American Society of Hematology (2004-2008) and the American Society of Clinical Oncology (1995-2008) were searched for relevant abstracts.

RESULTS

Bendamustine is a mechlorethamine derivative with structural similarity to chlorambucil and other drugs from the nitrogen mustard class, as well as a benzimidazole ring, which may act as an antagonist to purines and amino acids. It has good oral bioavailability but has been studied almost exclusively in the intravenous formulation. It undergoes extensive first-pass metabolism by cytochrome P450 1A2 to active metabolites gamma-hydroxy bendamustine and N-desmethyl-bendamustine, but clinical activity appears to be associated primarily with the parent compound. The t(1/2) of bendamustine is approximately 40 minutes. While bendamustine has 2 moieties with possible antitumor effect, it is unclear to what extent the benzimidazole ring enhances the efficacy of the drug. Numerous studies including in vitro assays have reported, however, that bendamustine has little cross-resistance with other alkylating agents and remains active even in extensively pretreated patients. FDA approval for use in CLL was based on findings from a randomized, open-label, Phase III study comparing bendamustine with chlorambucil as single-agent therapy in treatmentnaive patients with CLL (Binet stage B or C). Bendamustine was administered intravenously at a dose of 100 mg/m2 on days 1 and 2, while chlorambucil was administered orally at 0.8 mg/kg daily, both over 4-week cycles for up to 6 cycles. At interim analysis (the data used for FDA approval), bendamustine was associated with a greater overall response (68% vs 39%; P < 0.001), median progression-free survival (21.7 vs 9.3 months; P < 0.001) and median duration of remission (18.9 vs 6.1 months; P < 0.001) compared with chlorambucil. FDA approval for rituximabrefractory, indolent B-cell NHL followed a Phase III, open-label, single-arm study evaluating bendamustine monotherapy in patients who did not respond to rituximab or had progressive disease within 6 months of rituximab therapy. Bendamustine 120 mg/m(2) was administered intravenously on days 1 and 2 of a 21-day cycle for up to 8 cycles. At interim analysis, the overall response rate was 84%, including 29% complete response. The median progression-free survival was 9.7 months. The efficacy of bendamustine has also been reported in the treatment of MM in clinical studies, and bendamustine has been approved in Europe for treating MM, NHL, CLL, breast cancer, and Hodgkin lymphoma. Dose-limiting toxicity is primarily hematologic. Treatment-associated infections have been reported in some studies; however, nonhematologic adverse events have rarely been dose limiting. The most common nonhematologic adverse events include fatigue, nausea, xerostomia, and pyrexia.

CONCLUSIONS

Bendamustine is a mechlorethamine derivative with a purine-like benzimidazole ring, which may enhance its clinical efficacy. It has been approved in the United States for the treatment of CLL and rituximab-refractory, indolent B-cell NHL. It has been approved in Europe for use in other malignancies, and clinical studies have reported activity in MM.

Bendamustine pharmacokinetic profile and exposure-response relationships in patients with indolent non-Hodgkin's lymphoma

PURPOSE

The pharmacokinetic profiles of bendamustine and active metabolites were defined in patients with rituximab-refractory, relapsed indolent B-cell non-Hodgkin's lymphoma, and supported understanding of exposure-response relationships for efficacy and safety.

METHODS

Bendamustine was administered as a 60-min 120 mg/m(2) intravenous infusion on days 1 and 2 of six 21-day cycles. Pharmacokinetic models were developed, with covariate assessment. Correlations between bendamustine exposure and responder status or occurrence of neutropenia, thrombocytopenia, fatigue, nausea, and vomiting were examined.

RESULTS

Following a single dose of bendamustine HCl, concentrations declined in a triphasic manner, with rapid distribution, intermediate, and slow terminal phases. The intermediate t (1/2) (40 min) was considered the pharmacologically relevant (beta elimination) t (1/2) since the initial phases accounted for 99% of the AUC. Age, sex, mild/moderate renal, or mild liver impairment did not alter pharmacokinetics. Metabolite concentrations were low relative to parent. No correlation was observed between exposure and safety or efficacy measures because of the limited range of exposures after 120 mg/m(2) administration, except bendamustine C (max) was a significant (P value = 0.013) predictor of the probability of nausea in patients, most of whom were pretreated with antiemetics.

CONCLUSIONS

The BSA-based dosing regimen for bendamustine achieved the targeted exposure and was associated with a high incidence of therapeutic response. Given the short t (1/2) and low concentrations of bendamustine observed by 12 h after dosing, the single-dose profile for bendamustine described by these analyses is expected to be representative of the multiple-dose profile. The occurrence of nausea was significantly related to bendamustine exposure, with the probability of nausea increasing as bendamustine C (max) increases.

The role of bendamustine in the treatment of indolent non-Hodgkin lymphoma

There is no consensus on recommendations for the treatment of relapsed and refractory indolent non-Hodgkin lymphoma (NHL). Bendamustine hydrochloride (bendamustine) has recently been approved for treatment of these patients. Bendamustine is a uniquely structured alkylating agent that lacks cross-resistance with other alkylators. This agent has a high degree of activity against a variety of tumor cell lines. Clinically, bendamustine has demonstrated activity against indolent NHL, chronic lymphocytic lymphoma, multiple myeloma and mantle cell lymphoma. Moreover, studies have validated its activity in patients with indolent NHL who are resistant to purine analogs and rituximab. The cytotoxic activity of bendamustine has been shown to be synergistic with rituximab in hematological malignancies. The incidence of alopecia is significantly less than with other alkylating agents. Myelosuppression is the major toxicity associated with bendamustine.

Bendamustine in the treatment of chronic lymphocytic leukemia

Bendamustine is a cytotoxic agent that combines alkylating and antimetabolite effects. It has shown promising efficacy in a number of hematological cancers and, hence, is being investigated in patients with chronic lymphocytic leukemia (CLL), which is the most common form of adult leukemia in the Western world. Phase I/II trials with bendamustine as single-agent therapy in CLL have shown overall response rates of 56-93% and complete response rates of 7-29%. Preliminary data from a Phase III trial comparing bendamustine and chlorambucil (an agent widely used in the current treatment of CLL) have shown significantly higher response rates with bendamustine. Bendamustine has also shown activity in CLL when combined with mitoxantrone, rituximab or both. The principal toxicities associated with bendamustine are hematological, mainly leukopenia.

Bendamustine in the treatment of non-Hodgkin's lymphomas

PURPOSE

To review available data using bendamustine alone and in combination with other chemotherapeutic agents in treatment of patients with non-Hodgkin's lymphomas.

METHODS

Internet database searches and literature review.

RESULTS

Bendamustine was approved in March 2008 by the United States Food and Drug Administration for the treatment of patients with chronic lymphocytic leukemia. Many trials have been performed over the last decade using bendamustine not only as monotherapy, but also in combination with other agents including rituximab, vincristine, mitoxantrone, fludarabine, and other agents as therapy for patients with relapsed non-Hodgkin's lymphomas, and recently was approved for use in therapy of patients with relapsed indolent lymphomas considered refractory to rituximab therapy. As monotherapy, bendamustine induces good responses with only minor side effects. In combination with other agents, efficacy improves, especially when given in combination with rituximab. The drug has also been studied in combination with rituximab as initial therapy for indolent lymphomas, and has excellent activity with less toxicity than R-CHOP (rituximab - cyclophosphamide, hydroxydaunorubicin [Adriamycin], Oncovin [vincristine], and prednisone/prednisolone).

CONCLUSION

Overall, bendamustine has demonstrated promising results as therapy for non-Hodgkin's lymphomas and should be included in the armamentarium of agents used to treat relapsed indolent non-Hodgkin's lymphomas and may prove valuable as initial therapy for these diseases. Further studies are being conducted to demonstrate the efficacy of this drug in combination with other agents.

Bendamustine is effective in p53-deficient B-cell neoplasms and requires oxidative stress and caspase-independent signaling

PURPOSE

Chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) are two incurable B-cell lymphoid neoplasms characterized by distinct clinical presentation and evolution. Bendamustine hydrochloride is a multifunctional, alkylating agent with a purine-like ring system that exhibits activity in multiple cancer models, including CLL and MCL, but whose mechanism is only partially described. Our aim was to analyze the apoptotic pathways activated by bendamustine in CLL and MCL together with the relevance of p53 mutation in determining the response to this drug.

EXPERIMENTAL DESIGN

Thirteen CLL/MCL cell lines and primary tumor cells from 8 MCL and 25 CLL patients were cultured for up to 24 h with bendamustine followed by cytotoxic assays, flow cytometry, immunofluorescence, and Western blot analysis of p53 response pathway and apoptosis-related factors.

RESULTS

Bendamustine displayed cytotoxic activity on most CLL and MCL primary cells and cell lines irrespective of ZAP-70 expression and p53 status. Bendamustine was found to act synergistically with nucleoside analogues in both CLL and MCL, this combination being effective in p53 mutated cases resistant to standard chemotherapy. Bendamustine cytotoxicity was mediated by the generation of reactive oxygen species and triggering of the intrinsic apoptotic pathway involving up-regulation of PUMA and NOXA, conformational activation of BAX and BAK, and cytosolic release of caspase-related and caspase-unrelated mitochondrial apoptogenic proteins.

CONCLUSIONS

Our findings support the use of bendamustine as a therapeutic agent, alone or in combination, for CLL and MCL with p53 alterations and describe the molecular basis of its activity in these entities.

Bendamustine in Metastatic Breast Cancer: An Old Drug in New Design

The goal of treatment for patients with advanced breast cancer is to prolong survival, control symptoms, and reduce disease-related complications. Despite the introduction of many cytotoxic agents during the past decade, only modest improvement in survival in metastatic breast cancer has been achieved. In order to improve this situation, new cytotoxic drugs as well as molecule-targeted agents are now under investigation. Bendamustine is a bifunctional alkylating agent with cytotoxic activity against several types of solid tumors. In the search for new anthracycline-free combinations, taxanes and alkylating agents might be worth investigating, in order to reduce cardiac toxicity. In this article, we reviewed the latest information regarding antitumor activity, toxicity, pharmacokinetics, and clinical application of bendamustine as a cytotoxic agent in metastatic breast cancer.

Bendamustine, but not fludarabine, exhibits a low stem cell toxicity in vitro

PURPOSE

We investigated the in vitro toxicity of bendamustine and fludarabine to hematopoietic progenitors and stem cells from healthy donors.

METHODS

Clonogenic agar colony assays, non-clonogenic long-term liquid cultures (LTC) and apoptosis assays were used to assess the cytotoxicity of both the agents.

RESULTS

Total colony-forming units (CFU) were more sensitive to fludarabine than to bendamustine in agar colony assays (IC(50) 0.7 microM/L and 8.5 microM/L, respectively). Using the Bliss independence model and combining the two agents yielded additive inhibition of progenitors. Non-clonogenic assays, including LTC and an apoptosis assay detecting activated caspases showed that stem cells are characterized by low sensitivity to bendamustine. In contrast, fludarabine strongly inhibited the viability and growth of stem cells in LTC.

CONCLUSIONS

Our data show that bendamustine is characterized by lower in vitro toxicity to hematopoietic progenitors and stem cells than fludarabine and might thus be preferable in regimens prior to stem cells apheresis.

Bendamustine as a model for the activity of alkylating agents

Attempts to administer personalized standard cytotoxic chemotherapy based on individual patient characteristics have been disappointing. Alkylating agents are one of the oldest classes of anticancer medicine with a wide variety of molecular actions and thus the potential for broad utility. Bendamustine hydrochloride, a new addition to this class, was previously developed in the 1960s and has now been trialled in hematological malignancies and many solid tumor types as monotherapy or in combination with the known standard of care. It appears to occupy a particular role in resistant or refractory hematological disease and it was approved by the US FDA for the treatment of chronic lymphocytic leukemia in March 2008. Further trials will reveal whether it is likely to become incorporated into front-line regimens in non-Hodgkin's lymphoma and other malignancies.

Bendamustine (Treanda) displays a distinct pattern of cytotoxicity and unique mechanistic features compared with other alkylating agents

PURPOSE

Bendamustine has shown clinical activity in patients with disease refractory to conventional alkylator chemotherapy. The purpose of this study was to characterize the mechanisms of action of bendamustine and to compare it with structurally related compounds.

EXPERIMENTAL DESIGN

Bendamustine was profiled in the National Cancer Institute in vitro antitumor screen. Microarray-based gene expression profiling, real-time PCR, immunoblot, cell cycle, and functional DNA damage repair analyses were used to characterize response to bendamustine and compare it with chlorambucil and phosphoramide mustard.

RESULTS

Bendamustine displays a distinct pattern of activity unrelated to other DNA-alkylating agents. Its mechanisms of action include activation of DNA-damage stress response and apoptosis, inhibition of mitotic checkpoints, and induction of mitotic catastrophe. In addition, unlike other alkylators, bendamustine activates a base excision DNA repair pathway rather than an alkyltransferase DNA repair mechanism.

CONCLUSION

These results suggest that bendamustine possesses mechanistic features that differentiate it from other alkylating agents and may contribute to its distinct clinical efficacy profile.