Phase I clinical trial of bortezomib in combination with gemcitabine in patients with advanced solid tumors

Enhancing Apoptosis and Overcoming Resistance of Gemcitabine in Pancreatic Cancer with Bortezomib: A Role of Death-Associated Protein Kinase-Related Apoptosis-Inducing Protein Kinase 1

Aims and Background

To investigate the role of the apoptosis gene, DAP (death-associated protein) kinase-related apoptosis-inducing protein kinase 1 (DRAK1), which is involved in enhancing cell sensitivity and overcoming cell resistance to gemcitabine in pancreatic cancer cells by the proteasome inhibitor bortezomib.

Methods

Cultured human pancreatic cancer gemcitabine-sensitive cell lines (bxpc-3) and gemcitabine-resistant (panc-1) cell lines were divided into four groups: control, treatment with bortezomib, treatment with gemcitabine, and the two-drug combination. Expression of DRAK1 genes in each group was detected by using reverse transcription-polymerase chain reaction and western blot. Apoptosis in the pancreatic cancer cell lines was measured by flow cytometry.

Results

We found that the effects of growth inhibition and apoptosis of gemcitabine on both pancreatic cancer cell lines were enhanced by bortezomib. Treatment of panc-1 and bxpc-3 cells with bortezomib (100 nM) and gemcitabine (50 μg/ml and 0.05 μg/ml, respectively) induced an increase in the levels of DRAK1 mRNA compared with the control and single-agent treatment. Furthermore, immunblotting analysis in panc-1 but not bxpc-3 cells showed similar changes in the expression of DRAK1 protein produced by combination therapy.

Conclusions

Our results demonstrated that bortezomib enhanced cell sensitivity and overcame cell resistance to gemcitabine in pancreatic cancer cells, which may be attributed to DRAK1 induced by bortezomib and the combination with gemcitabine.

Carfilzomib demonstrates broad anti-tumor activity in pre-clinical non-small cell and small cell lung cancer models

BACKGROUND

Carfilzomib (CFZ) is a proteasome inhibitor that selectively and irreversibly binds to its target and has been approved in the US for treatment of relapsed and refractory multiple myeloma. Phase 1B studies of CFZ reported signals of clinical activity in solid tumors, including small cell lung cancer (SCLC). The aim of this study was to investigate the activity of CFZ in lung cancer models.

METHODS

A diverse panel of human lung cancer cell lines and a SHP77 small cell lung cancer xenograft model were used to investigate the anti-tumor activity of CFZ.

RESULTS

CFZ treatment inhibited both the constitutive proteasome and the immunoproteasome in lung cancer cell lines. CFZ had marked anti-proliferative activity in A549, H1993, H520, H460, and H1299 non-small cell lung cancer (NSCLC) cell lines, with IC50 values after 96 hour exposure from <1.0 nM to 36 nM. CFZ had more variable effects in the SHP77 and DMS114 SCLC cell lines, with IC50 values at 96 hours from <1 nM to 203 nM. Western blot analysis of CFZ-treated H1993 and SHP77 cells showed cleavage of poly ADP ribose polymerase (PARP) and caspase-3, indicative of apoptosis, and induction of microtubule-associated protein-1 light chain-3B (LC3B), indicative of autophagy. In SHP77 flank xenograft tumors, CFZ monotherapy inhibited tumor growth and prolonged survival, while no additive or synergistic anti-tumor efficacy was observed for CFZ + cisplatin (CDDP).

CONCLUSIONS

CFZ demonstrated anti-proliferative activity in lung cancer cell lines in vitro and resulted in a significant survival advantage in mice with SHP77 SCLC xenografts, supporting further pre-clinical and clinical investigations of CFZ in NSCLC and SCLC.

Ubiquitination and degradation of ribonucleotide reductase M1 by the polycomb group proteins RNF2 and Bmi1 and cellular response to gemcitabine

Ribonucleotide reductase M1 (RRM1) is required for mammalian deoxyribonucleotide (dNTP) metabolism. It is the primary target of the antimetabolite drug gemcitabine, which is among the most efficacious and most widely used cancer therapeutics. Gemcitabine directly binds to RRM1 and irreversibly inactivates ribonucleotide reductase. Intra-tumoral RRM1 levels are predictive of gemcitabine’s therapeutic efficacy. The mechanisms that regulate intracellular RRM1 levels are largely unknown. Here, we identified the E3 ubiquitin-protein ligases RNF2 and Bmi1 to associate with RRM1 with subsequent poly-ubiquitination at either position 48 or 63 of ubiquitin. The lysine residues 224 and 548 of RRM1 were identified as major ubiquitination sites. We show that ubiquitinated RRM1 undergoes proteasome-mediated degradation and that targeted post-transcriptional silencing of RNF2 and Bmi1 results in increased RRM1 levels and resistance to gemcitabine. Immunohistochemical analyses of 187 early-stage lung cancer tumor specimens revealed a statistically significant co-expression of RRM1 and Bmi1. We were unable to identify suitable reagents for in situ quantification of RNF2. Our findings suggest that Bmi1 and possibly RNF2 may be attractive biomarkers of gemcitabine resistance in the context of RRM1 expression. They also provide novel information for the rational design of gemcitabine-proteasome inhibitor combination therapies, which so far have been unsuccessful if given to patients without taking the molecular context into account.

A phase I/II trial of bortezomib combined concurrently with gemcitabine for relapsed or refractory DLBCL and peripheral T-cell lymphomas

There remains an unmet therapeutic need for patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL) and peripheral T-cell lymphoma (PTCL). We conducted a phase I/II trial with bortezomib (dose-escalated to 1·6 mg/m(2) ) given concurrently with gemcitabine (800 mg/m(2) ) days 1 + 8 q21 d. Of 32 patients, 16 each had relapsed/refractory PTCL and DLBCL. Median prior therapies were 3 and 35% had failed transplant. Among the first 18 patients, 67% experienced grade 3/4 neutropenia and/or grade 3/4 thrombocytopenia resulting in repeated treatment delays (relative dose intensity: 46%). Thus, the study was amended to give bortezomib and gemcitabine days 1 + 15 q28 d, which resulted in markedly improved tolerability. Among all patients, the overall response rate (ORR) was 24% with 19% complete remission (CR; intent-to-treat (ITT) ORR 16%, CR 13%), which met criteria for futility. The ORR for DLBCL was 10% (CR 10%) vs. 36% for PTCL (CR 27%). Among 6 PTCL patients treated on the modified schedule, ORR by ITT was 50% (CR 30%). Altogether, concurrent bortezomib/gemcitabine given days 1 + 8 q21 d was not tolerable, while modification to a bi-monthly schedule allowed consistent treatment delivery. Whereas efficacy of this combination was low in heavily pre-treated DLBCL, there was a signal of activity in relapsed/refractory PTCL utilizing the modified schedule.

Molecularly targeted therapies in metastatic pancreatic cancer: a systematic review

Pancreatic cancer is the fourth leading cause of cancer-related death. Most patients present with an advanced stage of disease that has a dismal outcome, with a median survival of approximately 6 months. Evidently, there is a clear need for the development of new agents with novel mechanisms of action in this disease. A number of biological agents modulating different signal transduction pathways are currently in clinical development, inhibiting angiogenesis and targeting epidermal growth factor receptor, cell cycle, matrix metalloproteinases, cyclooxygenase-2, mammalian target of rapamycin, or proteasome. This is the first systematic review of the literature to synthesize all available data coming from trials and evaluate the efficacy and safety of molecular targeted drugs in unresectable and metastatic pancreatic cancer. However, it should be stressed that although multiple agents have been tested, only 9 phase 3 trials have been conducted and one agent (erlotinib) has been approved by the Food and Drug Administration for use in clinical practice. As knowledge accumulates on the molecular mechanisms underlying carcinogenesis in the pancreas, the anticipated development and assessment of molecularly targeted agents may offer a promising perspective for a disease which, to date, remains incurable.

Phase I trial using the proteasome inhibitor bortezomib and concurrent chemoradiotherapy for head-and-neck malignancies

PURPOSE

Advanced head-and-neck cancer (HNC) remains a difficult disease to cure. Proteasome inhibitors such as bortezomib have the potential to improve survival over chemoradiotherapy alone. This Phase I dose-escalation study examined the potential of bortezomib in combination with cisplatin chemotherapy and concurrent radiation in the treatment of locally advanced and recurrent HNC.

METHODS AND MATERIALS

Eligible patients received cisplatin once weekly at 30 mg/m(2) per week and bortezomib along with concurrent radiation. Bortezomib was given on Days 1, 4, 8, and 11 every 3 weeks, with an initial starting dose of 0.7 mg/m(2) and escalation levels of 1.0 and 1.3 mg/m(2). Dose escalation was performed only after assessment to rule out any dose-limiting toxicity.

RESULTS

We enrolled 27 patients with HNC, including 17 patients with recurrent disease who had received prior irradiation. Patients received bortezomib dose levels of 0.7 mg/m(2) (7 patients), 1.0 mg/m(2) (10 patients), and 1.3 mg/m(2) (10 patients). No Grade 5 toxicities, 3 Grade 4 toxicities (all hematologic and considered dose-limiting toxicities), and 39 Grade 3 toxicities (in 20 patients) were observed. With a median follow-up of 7.4 months, the overall median survival was 24.7 months (48.4 months for advanced HNC patients and 15.4 months for recurrent HNC patients).

CONCLUSION

Bortezomib in combination with radiation therapy and cisplatin chemotherapy is safe in the treatment of HNC with a bortezomib maximum tolerated dose of 1.0 mg/m(2) in patients previously treated for HNC and 1.3 mg/m(2) in radiation-naive patients.

Phase 1 trial of gemcitabine with bortezomib in elderly patients with advanced solid tumors

INTRODUCTION

Bortezomib, a proteasome inhibitor, has synergistic antitumor activity with gemcitabine, an antimetabolite, in preclinical and clinical studies. The safety of this combination has not yet been established in elderly patients; therefore, this dose-escalation study was designed to assess the maximum-tolerated dose of bortezomib and gemcitabine in patients aged 70 years or older with advanced-stage solid tumors.

PATIENTS AND METHODS

Gemcitabine was administered intravenously (800 to 1000 mg/m) over 30 minutes on days 1 and 8, followed 60 minutes later by bortezomib administered as an intravenous push over 3 to 5 seconds (1.0 to 1.8 mg/m) on a 21-day cycle. This study used a standard phase 1 dose-escalation design with 3 or 6 patients per dose level.

RESULTS

Seventeen patients with stage IV solid tumors were treated. Median age was 73 years (range: 70 to 87 y). All patients had an Eastern Cooperative Oncology Group (ECOG) performance status less than 2. Median number of earlier chemotherapy regimens was 2 (range: 0 to 6). Dose-limiting toxicities were seen in 2 of 8 patients enrolled at the second dose level of gemcitabine (1000 mg/m) and bortezomib (1.0 mg/m), which consisted of grade ≥3 lower extremity edema, thrombocytopenia, fatigue, and dehydration. The most common grade ≥3 toxicities included thrombocytopenia (n=9), neutropenia (n=6), and anemia (n=5). Partial response (n=3) or disease stabilization (n=3) was seen in 6 of 14 evaluable patients.

CONCLUSIONS

Concurrent weekly gemcitabine (800 mg/m) and bortezomib (1 mg/m) is the recommended schedule for future phase 2 trials in elderly patients with stage IV solid tumors.

Age-stratified phase I trial of a combination of bortezomib, gemcitabine, and liposomal doxorubicin in patients with advanced malignancies

BACKGROUND

Preclinical data suggest synergistic activity of bortezomib, gemcitabine, and liposomal doxorubicin. Because tolerance to therapy may be attenuated in elderly patients, we performed an age-stratified phase I trial of this combination.

PATIENTS AND METHODS

Two parallel age-stratified arms (< 65 and ≥ 65 years old) were accrued (3 + 3 design). Starting doses included bortezomib 0.7 mg/m(2) (days 1 and 8), gemcitabine 500 mg/m(2) (days 1 and 8), and liposomal doxorubicin 20 mg/m(2) (day 1).

RESULTS

In the < 65-year-old group, 65 patients were treated; the maximum-tolerated dose was bortezomib 1.3 mg/m(2), gemcitabine 800 mg/m(2), and liposomal doxorubicin 35 mg/m(2). In the ≥ 65-year-old group, 28 patients were treated; the recommended phase II dose was bortezomib 1.0 mg/m(2), gemcitabine 800 mg/m(2), and liposomal doxorubicin 20 mg/m(2). Dose-limiting toxicities included thrombocytopenia and neutropenia. The most common toxicities were mild cytopenias, fatigue, and neuropathy. Ten patients achieved partial responses (6 of 7 patients with cutaneous T-cell lymphoma; 4 of 16 patients with small cell carcinomas, including lung, prostate, ovarian, and nasopharyngeal).

CONCLUSION

Combination of bortezomib, gemcitabine, and liposomal doxorubicin is well tolerated, but with a lower recommended phase II dose in elderly patients, and demonstrated antitumor activity, especially in T-cell and small cell histology malignancies.

A phase I study of bortezomib and temozolomide in patients with advanced solid tumors

PURPOSE

The primary objective was to determine the maximum tolerated doses (MTDs) of the combination of bortezomib and temozolomide in patients with solid tumors. The secondary objective was to evaluate the pharmacokinetics (PK) of bortezomib with and without concurrent hepatic enzyme-inducing anticonvulsants (HEIAs).

METHODS

Bortezomib was administered on days 2, 5, 9, and 12; temozolomide on days 1-5 of a 28-day cycle. Dose escalation proceeded using a standard 3+3 design. Patients with primary or metastatic brain tumors were eligible and were stratified based on whether they were taking HEIAs or not.

RESULTS

Of the 25 patients enrolled, 22 were not taking HEIAs. MTDs were only given to patients not receiving HEIAs. Dose-limiting toxicities (DLTs) consisted of grade-3 constipation, hyponatremia, fatigue, elevated hepatic enzymes, and grade-4 neutropenia, thrombocytopenia, constipation, and abdominal pain. Stable disease (>8 weeks) was observed in 5 patients. Bortezomib systemic clearance (CL(sys)) on day 9 was 51% of the CL(sys) on day 2 (P < 0.01) Similarly, the normalized area under the concentration-time curve (norm AUC) on day 9 was 1.9 times the norm AUC on day 2 (P < 0.01). The median bortezomib CL(sys) on days 2 and 9 was significantly higher (P < 0.04) in patients taking HEIAs, and the median norm AUC was correspondingly lower (P < 0.04).

CONCLUSIONS

The MTDs for the combination of bortezomib and temozolomide in patients not taking HEIAs are 1.3 and 200 mg/m(2), respectively. The rate of bortezomib elimination in patients taking HEIAs was increased twofold. Additional trials are needed to better define the optimal dosing in such patients.

Marizomib, a proteasome inhibitor for all seasons: preclinical profile and a framework for clinical trials

The proteasome has emerged as an important clinically relevant target for the treatment of hematologic malignancies. Since the Food and Drug Administration approved the first-in-class proteasome inhibitor bortezomib (Velcade) for the treatment of relapsed/refractory multiple myeloma (MM) and mantle cell lymphoma, it has become clear that new inhibitors are needed that have a better therapeutic ratio, can overcome inherent and acquired bortezomib resistance and exhibit broader anti-cancer activities. Marizomib (NPI-0052; salinosporamide A) is a structurally and pharmacologically unique β-lactone-γ-lactam proteasome inhibitor that may fulfill these unmet needs. The potent and sustained inhibition of all three proteolytic activities of the proteasome by marizomib has inspired extensive preclinical evaluation in a variety of hematologic and solid tumor models, where it is efficacious as a single agent and in combination with biologics, chemotherapeutics and targeted therapeutic agents. Specifically, marizomib has been evaluated in models for multiple myeloma, mantle cell lymphoma, Waldenstrom's macroglobulinemia, chronic and acute lymphocytic leukemia, as well as glioma, colorectal and pancreatic cancer models, and has exhibited synergistic activities in tumor models in combination with bortezomib, the immunomodulatory agent lenalidomide (Revlimid), and various histone deacetylase inhibitors. These and other studies provided the framework for ongoing clinical trials in patients with MM, lymphomas, leukemias and solid tumors, including those who have failed bortezomib treatment, as well as in patients with diagnoses where other proteasome inhibitors have not demonstrated significant efficacy. This review captures the remarkable translational studies and contributions from many collaborators that have advanced marizomib from seabed to bench to bedside.

A phase II study of bortezomib and gemcitabine in relapsed mantle cell lymphoma from the National Cancer Institute of Canada Clinical Trials Group (IND 172)

Bortezomib and gemcitabine have each shown activity as single agents in mantle cell lymphoma (MCL), which is incurable. The purpose of this phase II study was to determine the efficacy and safety of the previously unstudied combination of bortezomib and gemcitabine in patients with relapsed or refractory MCL. Patients were eligible if they had relapsed MCL with 1-3 prior therapies. Patients were treated with gemcitabine 1000 mg/m(2) on days 1 and 8 and bortezomib 1.0 mg/m(2) IV on days 1, 4, 8, and 11, on a 21-day schedule. Twenty-six patients were evaluable for toxicity and 25 for response. The overall response rate was 60% and the median progression free survival was 11.4 months. The main adverse effects were hematological, with 40% and 48% of patients experiencing grade 3/4 thrombocytopenia and granulocytopenia, respectively. Bortezomib and gemcitabine is an active combination in relapsed and refractory MCL with clinically meaningful results. It offers a chemotherapy backbone to which other agents, less myelosuppressive, may be added.

Targeted therapies for advanced non-small-cell lung cancer: current status and future implications

Lung cancer remains the leading cause of malignancy-related mortality worldwide, with over one million cases diagnosed yearly. Non-small-cell lung cancer (NSCLC) accounts for >80% of all lung cancers. Because lung cancer is typically diagnosed at an advanced stage, chemotherapy (CT) is the mainstay of management. Conventional treatment of NSCLC has apparently reached a plateau of effectiveness in improving survival of patients, and treatment outcomes must still be considered disappointing. Hence, considerable efforts have been made in order to identify novel targeted agents that interfere with other dysregulated pathways in advanced NSCLC patients. In order to further improve the results of targeted therapy, we should not forget that lung cancer is a heterogeneous disease with multiple mutations, and it is unlikely that any single signaling pathway drives the oncogenic behaviour of all tumours. The relative failure of some targeted therapies may be a result of multilevel cross-stimulation among the targets of the new biological agents along several pathways of signal transduction that lead to neoplastic events. Thus, blocking only one of these pathways allows others to act as salvage or escape mechanisms for cancer cells. We summarize the most promising research approaches to the treatment of NSCLC, with particular attention to drugs with multiple targets or combining targeted therapies.

Inhibition of NF-kappaB signaling by quinacrine is cytotoxic to human colon carcinoma cell lines and is synergistic in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or oxaliplatin

Colorectal cancer is the third most common malignancy in the United States. Modest advances with therapeutic approaches that include oxaliplatin (L-OHP) have brought the median survival rate to 22 months, with drug resistance remaining a significant barrier. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is undergoing clinical evaluation. Although human colon carcinomas express TRAIL receptors, they can also demonstrate TRAIL resistance. Constitutive NF-kappaB activation has been implicated in resistance to TRAIL and to cytotoxic agents. We have demonstrated constitutive NF-kappaB activation in five of six human colon carcinoma cell lines; this activation is inhibited by quinacrine. Quinacrine induced apoptosis in colon carcinomas and potentiated the cytotoxic activity of TRAIL in RKO and HT29 cells and that of L-OHP in HT29 cells. Similarly, overexpression of IkappaBalpha mutant (IkappaBalphaM) or treatment with the IKK inhibitor, BMS-345541, also sensitized these cells to TRAIL and L-OHP. Importantly, 2 h of quinacrine pretreatment resulted in decreased expression of c-FLIP and Mcl-1, which were determined to be transcriptional targets of NF-kappaB. Extended exposure for 24 h to quinacrine did not further sensitize these cells to TRAIL- or L-OHP-induced cell death; however, exposure caused the down-regulation of additional NF-kappaB-dependent survival factors. Short hairpin RNA-mediated knockdown of c-FLIP or Mcl-1 significantly sensitized these cells to TRAIL and L-OHP. Taken together, data demonstrate that NF-kappaB is constitutively active in colon cancer cell lines and NF-kappaB, and its downstream targets may constitute an important target for the development of therapeutic approaches against this disease.

Effect of the CYP3A inhibitor ketoconazole on the pharmacokinetics and pharmacodynamics of bortezomib in patients with advanced solid tumors: a prospective, multicenter, open-label, randomized, two-way crossover drug-drug interaction study

BACKGROUND

The proteasome inhibitor bortezomib undergoes oxidative biotransformation via multiple cytochrome P450 (CYP) enzymes, with CYP3A4 identified as a partial, yet potentially important, contributor based on in vitro drug metabolism studies.

OBJECTIVE

The aim of this study was to assess the effect of concomitant administration of ketoconazole on the pharmacokinetics (PK) and pharmacodynamics (PD) of bortezomib.

METHODS

This was a prospective, multicenter, open-label, randomized, multiple-dose, 2-way crossover study in patients with advanced solid tumors. All patients received bortezomib 1.0 mg/m(2) IV (on days 1, 4, 8, and 11 of two 21-day cycles) and were randomized to receive concomitant ketoconazole 400 mg on days 6, 7, 8, and 9 of cycle 1 or 2. Serial blood samples were collected over the day-8 dosing interval (immediately prior to bortezomib administration, and from 5 minutes to 72 hours after administration) in cycles 1 and 2 for measurement of plasma bortezomib concentrations for noncompartmental PK analysis and blood 20S proteasome inhibition for PD analysis. All adverse events (AEs) were recorded during each cycle including serious AEs and all neurotoxicity events for up to 30 days after the last dose of bortezomib.

RESULTS

Twenty-one patients (median age, 57 years; sex, 67% male; race, 86% white; median body surface area, 2.01 m(2)) were randomized to treatment. Twelve patients completed the protocol-specified dosing and PK sampling in both cycles 1 and 2. Assessment of the effect of ketoconazole on bortezomib PK and PD was based on data in these 12 PK-evaluable patients. The ratio of geometric mean bortezomib AUC(0-tlast)(AUC from time 0 to last quantifiable concentration) for bortezomib plus ketoconazole versus bortezomib alone was 1.352 (90% CI, 1.032-1.772). Consistent with this observed mean increase in bortezomib exposure, concomitant administration of ketoconazole was associated with a corresponding increase (24%-46%) in the blood proteasome inhibitory effect.

CONCLUSION

Concomitant administration of the CYP3A inhibitor ketoconazole with bortezomib resulted in a mean increase of 35% in bortezomib exposure. ClinicalTrials.gov identifier: NCT00129207.

Phase I trial of bortezomib and concurrent external beam radiation in patients with advanced solid malignancies

PURPOSE

To determine the maximal tolerated dose of bortezomib with concurrent external beam radiation therapy in patients with incurable solid malignant tumors requiring palliative therapy.

METHODS AND MATERIALS

An open label, dose escalation, phase I clinical trial evaluated the safety of three dose levels of bortezomib administered intravenously (1.0 mg/m(2), 1.3 mg/m(2), and 1.6 mg/m(2)/ dose) once weekly with concurrent radiation in patients with histologically confirmed solid tumors and a radiographically appreciable lesion suitable for palliative radiation therapy. All patients received 40 Gy in 16 fractions to the target lesion. Dose-limiting toxicity was the primary endpoint, defined as any grade 4 hematologic toxicity, any grade ≥3 nonhematologic toxicity, or any toxicity requiring treatment to be delayed for ≥2 weeks.

RESULTS

A total of 12 patients were enrolled. Primary sites included prostate (3 patients), head and neck (3 patients), uterus (1 patient), abdomen (1 patient), breast (1 patient), kidney (1 patient), lung (1 patient), and colon (1 patient). The maximum tolerated dose was not realized with a maximum dose of 1.6 mg/m(2). One case of dose-limiting toxicity was appreciated (grade 3 urosepsis) and felt to be unrelated to bortezomib. The most common grade 3 toxicity was lymphopenia (10 patients). Common grade 1 to 2 events included nausea (7 patients), infection without neutropenia (6 patients), diarrhea (5 patients), and fatigue (5 patients).

CONCLUSIONS

The combination of palliative external beam radiation with concurrent weekly bortezomib therapy at a dose of 1.6 mg/m(2) is well tolerated in patients with metastatic solid tumors. The maximum tolerated dose of once weekly bortezomib delivered concurrently with radiation therapy is greater than 1.6 mg/m(2).

A randomized phase 2 study of erlotinib alone and in combination with bortezomib in previously treated advanced non-small cell lung cancer

INTRODUCTION

This phase 2 study was conducted to determine the efficacy and safety of erlotinib alone and with bortezomib in patients with non-small cell lung cancer (NSCLC).

METHODS

Patients with histologically or cytologically confirmed relapsed or refractory stage IIIb/IV NSCLC were randomized (1:1; stratified by baseline histology, smoking history, sex) to receive erlotinib 150 mg/d alone (arm A; n = 25) or in combination with bortezomib 1.6 mg/m2, days 1 and 8 (arm B; n = 25) in 21-day cycles. Responses were assessed using Response Evaluation Criteria in Solid Tumors. Tumor samples were evaluated for mutations predicting response. Six additional patients received the combination in a prior dose deescalation stage and were included in safety analyses.

RESULTS

Response rates were 16% in arm A and 9% in arm B; disease control rates were 52 and 45%, respectively. The study was halted at the planned interim analysis due to insufficient clinical activity in arm B. Median progression-free survival and overall survival were 2.7 and 7.3 months in arm A, and 1.3 and 8.5 months in arm B. Six-month survival rates were 56.0% in both arms; 12-month rates were 40 and 30% in arms A and B, respectively. Response rate to erlotinib+/-bortezomib was significantly higher in patients with epidermal growth factor receptor mutations (50 versus 9% for wild type). The most common treatment-related grade > or =3 adverse event was skin rash (three patients in each treatment group).

CONCLUSION

Insufficient activity was seen with erlotinib plus bortezomib in patients with relapsed/refractory advanced NSCLC to warrant a phase 3 study of the combination.

A randomized phase II study of bortezomib and pemetrexed, in combination or alone, in patients with previously treated advanced non-small-cell lung cancer

BACKGROUND

This is a phase II randomized study to evaluate the efficacy and safety of bortezomib and pemetrexed alone or in combination, in patients with previously treated advanced non-small-cell lung cancer (NSCLC). The primary end point was assessment of response rate.

METHODS

A total of 155 patients were randomized (1:1:1) to pemetrexed (500mg/m(2)) on day 1 plus bortezomib (1.6mg/m(2)) on days 1 and 8 (Arm A) or pemetrexed (500mg/m(2)) on day 1 (Arm B) or bortezomib (1.6mg/m(2)) on days 1 and 8 (Arm C) of a 21 day cycle. Response rate was assessed by investigators using Response Evaluation Criteria In Solid Tumors (RECIST) criteria and toxicity assessed by the National Cancer Institute-Common Terminology Criteria for Adverse Events (NCI-CTCAE) grading system.

RESULTS

Response rate was 7% in Arm A, 4% in Arm B, and 0% in Arm C; disease control rates were 73%, 62%, and 43%, respectively. Median overall survival was 8.6 months in Arm A, 12.7 months in Arm B, and 7.8 months in Arm C; time to progression was 4.0 months, 2.9 months, and 1.4 months, respectively. Most common reported adverse events >/=grade 3 were neutropenia (19%), thrombocytopenia (15%), and dyspnea (13%) in Arm A, neutropenia (10%) in Arm B, and dyspnea (13%) and fatigue (10%) in Arm C.

CONCLUSION

In previously treated NSCLC the addition of bortezomib to pemetrexed was well tolerated but offered no statistically significant response or survival advantage versus pemetrexed alone, while bortezomib alone showed no clinically significant activity.

Effect of the cytochrome P450 2C19 inhibitor omeprazole on the pharmacokinetics and safety profile of bortezomib in patients with advanced solid tumours, non-Hodgkin's lymphoma or multiple myeloma

BACKGROUND AND OBJECTIVE

Bortezomib, an antineoplastic for the treatment of relapsed multiple myeloma and mantle cell lymphoma, undergoes metabolism through oxidative deboronation by cytochrome P450 (CYP) enzymes, primarily CYP3A4 and CYP2C19. Omeprazole, a proton-pump inhibitor, is primarily metabolized by and demonstrates high affinity for CYP2C19. This study investigated whether coadministration of omeprazole affected the pharmacokinetics, pharmacodynamics and safety profile of bortezomib in patients with advanced cancer. The variability of bortezomib pharmacokinetics with CYP enzyme polymorphism was also investigated.

PATIENTS AND METHODS

This open-label, crossover, pharmacokinetic drug-drug interaction study was conducted at seven institutions in the US and Europe between January 2005 and August 2006. Patients who had advanced solid tumours, non-Hodgkin's lymphoma or multiple myeloma, were aged >/=18 years, weighed >/=50 kg and had a life expectancy of >/=3 months were eligible. Patients received bortezomib 1.3 mg/m2 on days 1, 4, 8 and 11 for two 21-day cycles, plus omeprazole 40 mg in the morning of days 6-10 and in the evening of day 8 in either cycle 1 (sequence 1) or cycle 2 (sequence 2). On day 21 of cycle 2, patients benefiting from therapy could continue to receive bortezomib for six additional cycles. Blood samples for pharmacokinetic/pharmacodynamic evaluation were collected prior to and at various timepoints after bortezomib administration on day 8 of cycles 1 and 2. Blood samples for pharmacogenomics were also collected. Pharmacokinetic parameters were calculated by noncompartmental analysis of plasma concentration-time data for bortezomib administration on day 8 of cycles 1 and 2, using WinNonlin version 4.0.1.a software. The pharmacodynamic profile was assessed using a whole-blood 20S proteasome inhibition assay.

RESULTS

Twenty-seven patients (median age 64 years) were enrolled, 12 in sequence 1 and 15 in sequence 2, including eight and nine pharmacokinetic-evaluable patients, respectively. Bortezomib pharmacokinetic parameters were similar when bortezomib was administered alone or with omeprazole (maximum plasma concentration 120 vs 123 ng/mL; area under the plasma concentration-time curve from 0 to 72 hours 129 vs 135 ng . h/mL). The pharmacodynamic parameters were also similar (maximum effect 85.8% vs 93.7%; area under the percent inhibition-time curve over 72 hours 4052 vs 3910 % x h); the differences were not statistically significant. Pharmacogenomic analysis revealed no meaningful relationships between CYP enzyme polymorphisms and pharmacokinetic/pharmacodynamic parameters. Toxicities were generally similar between patients in sequence 1 and sequence 2, and between cycle 1 and cycle 2 in both treatment sequences. Among 26 evaluable patients, 13 (50%) were assessed as benefiting from bortezomib at the end of cycle 2 and continued to receive treatment.

CONCLUSION

No impact on the pharmacokinetics, pharmacodynamics and safety profile of bortezomib was seen with coadministration of omeprazole. Concomitant administration of bortezomib and omeprazole is unlikely to cause clinically significant drug-drug interactions and is unlikely to have an impact on the efficacy or safety of bortezomib.

Bortezomib induces schedule-dependent modulation of gemcitabine pharmacokinetics and pharmacodynamics in non-small cell lung cancer and blood mononuclear cells

Bortezomib combination with gemcitabine/cisplatin in patients with advanced tumors, predominantly non-small cell lung cancer (NSCLC), showed an unexpected transient drop in the deoxycytidine plasma levels, a marker for gemcitabine activity. This study investigates the pharmacokinetic/pharmacodynamic effect of bortezomib on gemcitabine in NSCLC and peripheral blood mononuclear cells (PBMC). Gemcitabine metabolites, including difluoro-dCTP (dFdCTP), were studied in PBMCs from bortezomib/gemcitabine/cisplatin-treated patients and from volunteers and NSCLC cells (H460 and SW1573) exposed to 4 h simultaneous or sequential treatments of gemcitabine (50 μmol/L, 4 h) and bortezomib (100 nmol/L, 2 h). Gemcitabine total phosphate levels measured by liquid chromatography-tandem mass spectrometry in PBMCs from bortezomib/gemcitabine/cisplatin-treated patients were strongly reduced after 90 min (-82.2%) up to 4 h post-gemcitabine infusion compared with gemcitabine/cisplatin-treated patients. Accordingly, bortezomib/gemcitabine combinations reduced dFdCTP in PBMCs treated ex vivo. Surprisingly, differential effects were observed in NSCLC cells. dFdCTP decreased after 4 h following gemcitabine removal in H460 but continued to increase for 24 h in SW1573. However, dFdCTP significantly increased (2-fold) in both cell lines in the bortezomib → gemcitabine exposure, coinciding with a major reduction in cell growth compared with single drugs, and the highest increase of deoxycytidine kinase expression, possibly mediated via E2F-1. Bortezomib affects differently gemcitabine pharmacokinetics/pharmacodynamics in PBMCs and NSCLC cells, suggesting that PBMCs are not adequate to evaluate the anticancer activity of bortezomib/gemcitabine combinations. The bortezomib → gemcitabine/cisplatin schedule appeared a safe and active combination for the treatment of advanced NSCLC and the bortezomib → gemcitabine was the most cytotoxic combination in NSCLC cells. The increase of deoxycytidine kinase and dFdCTP might contribute to this synergistic interaction and supports its further clinical investigation.

The ubiquitin-proteasome system as a molecular target in solid tumors: an update on bortezomib

The ubiquitin-proteasome system has become a promising molecular target in cancer therapy due to its critical role in cellular protein degradation, interaction with cell cycle and apoptosis regulation, and unique mechanism of action. Bortezomib (PS-341) is a potent and specific reversible proteasome inhibitor, which has shown strong in vitro antitumor activity as single agent and in combination with other cytotoxic drugs in a broad spectrum of hematological and solid malignancies. In preclinical studies, bortezomib induced apoptosis of malignant cells through the inhibition of NF-|B and stabilization of pro-apoptotic proteins. Bortezomib also promotes chemo- and radiosensitization of malignant cells in vitro and inhibits tumor growth in murine xenograft models. The proteasome has been established as a relevant target in hematologic malignancies and bortezomib has been approved for the treatment of multiple myeloma. This review summarizes recent data from clinical trials in solid tumors.

Proteasome inhibition activates epidermal growth factor receptor (EGFR) and EGFR-independent mitogenic kinase signaling pathways in pancreatic cancer cells

PURPOSE

In the current study, we investigate the activation of antiapoptotic signaling pathways in response to proteasome inhibitor treatment in pancreatic cancer and evaluate the use of concomitant inhibition of these pathways to augment proteasome inhibitor treatment responses.

EXPERIMENTAL DESIGN

Pancreatic cancer cell lines and mouse flank xenografts were treated with proteasome inhibitor alone or in combination with chemotherapeutic compounds (gemcitabine, erlotinib, and bevacizumab), induction of apoptosis and effects on tumor growth were assessed. The effect of bortezomib (a first-generation proteasome inhibitor) and NPI-0052 (a second-generation proteasome inhibitor) treatment on key pancreatic mitogenic and antiapoptotic pathways [epidermal growth factor receptor, extracellular signal-regulated kinase, and phosphoinositide-3-kinase (PI3K)/AKT] was determined and the ability of inhibitors of these pathways to enhance the effects of proteasome inhibition was assessed in vitro and in vivo.

RESULTS

Our data showed that proteasome inhibitor treatment activates antiapoptotic and mitogenic signaling pathways (epidermal growth factor receptor, extracellular signal-regulated kinase, c-Jun-NH2-kinase, and PI3K/AKT) in pancreatic cancer. Additionally, we found that activation of these pathways impairs tumor response to proteasome inhibitor treatment and inhibition of the c-Jun-NH2-kinase and PI3K/AKT pathways increases the antitumor effects of proteasome inhibitor treatment.

CONCLUSION

These preclinical studies suggest that targeting proteasome inhibitor-induced antiapoptotic signaling pathways in combination with proteasome inhibition may augment treatment response in highly resistant solid organ malignancies. Further evaluation of these novel treatment combinations in clinical trials is warranted.

Active roles for inhibitory kappaB kinases alpha and beta in nuclear factor-kappaB-mediated chemoresistance to doxorubicin

Chemotherapy agents have been shown to induce the transcription factor nuclear factor-kappaB (NF-kappaB) and subsequent chemoresistance in fibrosarcomas and other cancers. The mechanism of NF-kappaB-mediated chemoresistance remains unclear, with a previous report suggesting that doxorubicin induces this response independent of the inhibitory kappaB kinases (IKK). Other studies have indicated that IKKbeta, but not IKKalpha, is required. Mouse embryo fibroblasts devoid of IKKalpha, IKKbeta, or both subunits (double knockout) were treated with doxorubicin. The absence of either IKKalpha or IKKbeta or both kinases resulted in impaired induction of NF-kappaB DNA-binding activity in response to doxorubicin. To provide a valid clinical correlate, HT1080 human fibrosarcoma cells were transfected with small interference RNA specific for IKKalpha or IKKbeta and then subsequently treated with doxorubicin. Knockdown of IKKalpha severely impaired the ability of doxorubicin to initiate NF-kappaB DNA-binding activity. However, a decrease in either IKKalpha or IKKbeta resulted in decreased phosphorylation of p65 in response to doxorubicin. The inhibition of doxorubicin-induced NF-kappaB activation by the knockdown of either catalytic subunit resulted in increased cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase and increased apoptosis when compared with doxorubicin alone. The results of this study validate current approaches aimed at NF-kappaB inhibition to improve clinical therapies. Moreover, we show that IKKalpha plays a critical role in NF-kappaB-mediated chemoresistance in response to doxorubicin and may serve as a potential target in combinational strategies to improve chemotherapeutic response.

The ubiquitin-proteasome system in colorectal cancer

The proteasome is a multiprotein complex that regulates the stability of hundreds of cellular proteins and thus, it is implicated in virtually all cellular functions. Most of the time, to be recognized and processed by the proteasome, a protein has to be linked to a chain of ubiquitin molecules. Cell proliferation, apoptosis, angiogenesis and motility, processes with particular importance for carcinogenesis are regulated by the ubiquitin-proteasome system (UPS). In colorectal epithelium, UPS plays a role in the regulation of the Wnt/beta-catenin/APC/TCF4 signaling which regulates proliferation of colorectal epithelial cells in the bottom of the crypts and the inhibition of this proliferation as cells move towards colon villi tips. In most colorectal cancers APC (Adenomatous Polyposis Coli) disabling mutations interfere with the ability of the proteasome to degrade beta-catenin leading to uninhibited cell proliferation. Other key molecules in colorectal carcinogenesis such as p53, Smad4 and components of the k-ras pathways are also regulated by the UPS. In this review I discuss the role of UPS in colorectal carcinogenesis and colorectal cancer prognosis and aspects of its inhibition for therapeutic purposes.

Bortezomib with or without irinotecan in relapsed or refractory colorectal cancer: results from a randomized phase II study

PURPOSE

To evaluate the efficacy and toxicity of bortezomib with or without irinotecan, in patients with relapsed or refractory colorectal cancer (CRC).

PATIENTS AND METHODS

Patients were randomly assigned in a 3:4 ratio to bortezomib 1.5 mg/m(2) (arm A) or bortezomib 1.3 mg/m(2) plus irinotecan 125 mg/m(2) (arm B). A treatment cycle of 21 days consisted of four bortezomib doses on days 1, 4, 8, and 11, plus, in arm B, irinotecan on days 1 and 8. The primary objective of this randomized, multicenter, open-label, phase II study was to determine tumor response to treatment. Secondary objectives were safety and tolerability.

RESULTS

A preplanned interim analysis to assess efficacy revealed inadequate activity, resulting in early termination of this study. A total of 102 patients were treated, 45 in arm A and 57 in arm B. Baseline characteristics were comparable. The investigator-assessed response rate was 0 in arm A and 3.5% in arm B (all partial responses). Adverse events in both treatment arms were as expected, with no significant additive toxicity. The most common grade >or= 3 adverse events reported, per patient, during the study were fatigue (27%), vomiting (13%), nausea (11%), and peripheral sensory neuropathy (11%) in arm A, and diarrhea (33%), fatigue (25%), neutropenia (23%), thrombocytopenia (18%), dyspnea (12%), abdominal pain (12%), dehydration (12%), and anemia (11%) in arm B.

CONCLUSION

Bortezomib alone or in combination with irinotecan was not effective in patients with relapsed or refractory CRC.

Bortezomib and gemcitabine in relapsed or refractory Hodgkin's lymphoma

BACKGROUND

Given the significant activity and tolerability of gemcitabine in patients with relapsed Hodgkin's lymphoma (HL), the critical role that nuclear factor kappa B (NF-kappaB) appears to play in the pathogenesis of this tumor, the ability of bortezomib to inhibit NF-kappaB activity, and laboratory studies suggesting synergistic antitumor effects of gemcitabine and bortezomib, we hypothesized that this combination would be efficacious in patients with relapsed or refractory HL.

PATIENTS AND METHODS

A total of 18 patients participated. Patients received 3-week cycles of bortezomib 1 mg/m(2) on days 1, 4, 8, and 11 plus gemcitabine 800 mg/m(2) on days 1 and 8.

RESULTS

The overall response rate for all patients was 22% (95% confidence interval 3% to 42%). Three patients developed grade III transaminase elevation: one was removed from the study and two had doses of gemcitabine held. Almost all patients exhibited inhibition of proteasome activity with treatment.

CONCLUSIONS

The combination of gemcitabine and bortezomib is a less active and more toxic regimen in relapsed HL than other currently available treatments. It poses a risk of severe liver toxicity and should be pursued with caution in other types of cancer.

Prevalence of bortezomib-resistant constitutive NF-kappaB activity in mantle cell lymphoma

Background

The proteasome inhibitor bortezomib can inhibit activation of the transcription factor NF-κB, a mechanism implicated in its anti-neoplastic effects observed in mantle cell lymphoma (MCL). However, NF-κB can be activated through many distinct mechanisms, including proteasome independent pathways. While MCL cells have been shown to harbor constitutive NF-κB activity, what fraction of this activity in primary MCL samples is sensitive or resistant to inhibition by bortezomib remains unclear.

Results

Proteasome activity in the EBV-negative MCL cell lines Jeko-1 and Rec-1 is inhibited by greater than 80% after exposure to 20 nM bortezomib for 4 hours. This treatment decreased NF-κB activity in Jeko-1 cells, but failed to do so in Rec-1 cells when assessed by electrophoretic mobility shift assay (EMSA). Concurrently, Rec-1 cells were more resistant to the cytotoxic effects of bortezomib than Jeko-1 cells. Consistent with a proteasome inhibitor resistant pathway of activation described in mouse B-lymphoma cells (WEHI231) and a breast carcinoma cell line (MDA-MB-468), the bortezomib-resistant NF-κB activity in Rec-1 cells is inhibited by calcium chelators, calmodulin inhibitors, and perillyl alcohol, a monoterpene capable of blocking L-type calcium channels. Importantly, the combination of perillyl alcohol and bortezomib is synergistic in eliciting Rec-1 cell cytotoxicity. The relevance of these results is illuminated by the additional finding that a considerable fraction of primary MCL samples (8 out of 10) displayed bortezomib-resistant constitutive NF-κB activity.

Conclusion

Our findings show that bortezomib-resistant NF-κB activity is frequently observed in MCL samples and suggest that this activity may be relevant to MCL biology as well as serve as a potential therapeutic target.

The proteasome inhibitor bortezomib in combination with gemcitabine and carboplatin in advanced non-small cell lung cancer: a California Cancer Consortium Phase I study

INTRODUCTION

Bortezomib is a small-molecule proteasome inhibitor with single-agent activity in patients with non-small cell lung carcinoma (NSCLC) and synergy with gemcitabine in preclinical studies. The combination of gemcitabine and carboplatin is an accepted first-line treatment for advanced NSCLC. We conducted a phase I study of gemcitabine and carboplatin in combination with bortezomib.

METHODS

Bortezomib was administered on days 1, 4, 8, and 11, after gemcitabine on days 1 and 8, and carboplatin on day 1 of a 21-day cycle. Three escalating dose levels were evaluated: bortezomib 1.0 mg/m2/gemcitabine 800 mg/m2, bortezomib 1.0 mg/m2/gemcitabine 1000 mg/m2, and bortezomib 1.3 mg/m2/gemcitabine 1000 mg/m2, in combination with carboplatin AUC 5.0.

RESULTS

Twenty-six patients with advanced NSCLC were treated; 21 were chemotherapy-naive. The median age was 59 years (range, 34-74), and 23 patients were stage IV. The Karnofsky performance score was <or=80% in 10 and >80% in 16 patients. Dose-limiting toxicities were grade 3 thrombocytopenia with bleeding and febrile neutropenia accompanied by grade 4 thrombocytopenia and grade 3 hyponatremia. The maximum-tolerated dose was defined as bortezomib 1.0 mg/m2, gemcitabine 1000 mg/m2, and carboplatin AUC 5.0. The most common grade 3/4 toxicities were thrombocytopenia (rarely associated with bleeding), and neutropenia. Nine of 26 patients (35%) achieved partial response, and eight patients had stable disease.

CONCLUSIONS

The combination of bortezomib 1.0 mg/m2, gemcitabine 1000 mg/m2, and carboplatin AUC 5.0 demonstrated manageable toxicities and encouraging activity in NSCLC. This regimen was used in a phase II study.

Targeted therapies for pancreatic cancer

INTRODUCTION

Pancreatic cancer is a devastating malignancy and a leading cause of cancer mortality. Furthermore, early diagnosis represents a serious hurdle for clinicians, as symptoms are non-specific and usually manifest in advanced, treatment-resistant stages of the disease.

SOURCES OF DATA

Here, we review the rationale and progress of targeted therapies currently under investigation.

AREAS OF AGREEMENT

At present, chemoradiation regimes are administered palliatively, and produce only marginal survival benefits, underscoring a desperate need for more effective treatment modalities.

AREAS OF CONTROVERSY

Questions have been raised as to whether erlotinib, the only targeted therapy to attain a statistically significant increase in median survival, is cost-effective.

GROWING POINTS

The last decade of research has provided us with a wealth of information regarding the molecular nature of pancreatic cancer, leading to the identification of signalling pathways and their respective components which are critical for the maintenance of the malignant phenotype.

AREAS TIMELY FOR DEVELOPING RESEARCH

These proteins thus represent ideal targets for novel molecular therapies which embody an urgently needed novel treatment strategy.

Knockdown of PgP resensitizes leukemic cells to proteasome inhibitors

Overexpression of MDR-1 represents a critical mechanism of drug resistance in cancer. Proteasome inhibitors recently entered the clinic for treatment of multiple myeloma. We provide evidence that the proteasome-inhibitors Bortezomib and MLN273 are both substrates of MDR-1 by using knockdown of MDR-1 via a transposon-based vector system stably expressing siRNA against MDR-1 in MDR-1-overexpressing K562/Dox cells. Notably, the efficacy of MLN273 (EC(50) from 253 ng/ml in MDR-1(+) to 9.7 ng/ml in MDR-1(-) cells) was much more dependent on MDR-1 expression than Bortezomib (EC(50) from 24.9 ng/ml in MDR-1(+) to 4.5 ng/ml in MDR-1(-) cells). Growth inhibition in MDR-1 negative cells was in part due to increased rate of apoptosis. The enhanced inhibitory effect on the proteasome by loss of MDR-1 was corroborated by a reduced proteasomal activity. Our report provides evidence that MLN273 and, to a lesser degree, Bortezomib are both MDR-1-substrates, which might be relevant for drug-resistance in cancer.

A Parallel Dose-Escalation Study of Weekly and Twice-Weekly Bortezomib in Combination with Gemcitabine and Cisplatin in the First-Line Treatment of Patients with Advanced Solid Tumors

PURPOSE

To establish maximum tolerated dose (MTD) and tolerability of two schedules of bortezomib in combination with cisplatin and gemcitabine as first-line treatment of patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Patients were assigned to increasing doses of bortezomib days 1 and 8 (weekly schedule) or days 1, 4, 8, and 11 (twice-weekly schedule), in addition to gemcitabine 1,000 mg/m(2) days 1 and 8 and cisplatin 70 mg/m(2) day 1, every 21 days. Maximum of six cycles. Plasma pharmacokinetics of cisplatin and gemcitabine were determined at MTD.

RESULTS

Thirty-four patients were enrolled of whom 27 had non-small cell lung cancer (NSCLC). Diarrhea, neutropenia, and thrombocytopenia were dose-limiting toxicities leading to an MTD of bortezomib 1.0 mg/m(2) in the weekly schedule. Febrile neutropenia and thrombocytopenia with bleeding were dose-limiting toxicities in the twice-weekly schedule, leading to an MTD of bortezomib 1.0 mg/m(2) as well. Most common > or =grade 3 treatment-related toxicities were thrombocytopenia and neutropenia. No grade > or =3 treatment-related sensory neuropathy was reported. Of 34 evaluable patients, 13 achieved partial responses, 17 stable disease, and 4 progressive disease. Response and survival of NSCLC patients treated with twice weekly or weekly bortezomib were similar. However, increased dose intensity of bortezomib led to increased gastrointestinal toxicity as well as myelosuppression. Pharmacokinetic profiles of cisplatin and gemcitabine were not significantly different in patients receiving either schedule.

CONCLUSIONS

Weekly bortezomib 1.0 mg/m(2) plus gemcitabine 1,000 mg/m(2) and cisplatin 70 mg/m(2) is the recommended phase 2 schedule, constituting a safe combination, with activity in NSCLC.

The proteasome: a worthwhile target for the treatment of solid tumours?

Proteasomes have a fundamental function since they degrade numerous different proteins, including those involved in the regulation of the cell cycle. Proteasome inhibition is a novel approach to the treatment of solid tumours. PS-341 (bortezomib) is a small, cell-permeable molecule that selectively inhibits the proteasome binding it in a reversible manner. The proteasome has been established as an important target in haematologic malignancies and has been approved for the treatment of multiple myeloma. Bortezomib induces apoptosis of malignant cells through the inhibition of NF-kappaB and stabilisation of proapoptotic proteins. In preclinical studies, bortezomib also promoted chemo and radiosensitisation of malignant cells in vitro and inhibited tumour growth in murine xenografts models. The single-agent and combination studies of bortezomib in solid tumours are detailed.