IDH2 mutation-induced histone and DNA hypermethylation is progressively reversed by small-molecule inhibition.

Mutations of IDH1 and IDH2, which produce the oncometabolite 2-hydroxyglutarate (2HG), have been identified in several tumors, including acute myeloid leukemia. Recent studies have shown that expression of the IDH mutant enzymes results in high levels of 2HG and a block in cellular differentiation that can be reversed with IDH mutant-specific small-molecule inhibitors. To further understand the role of IDH mutations in cancer, we conducted mechanistic studies in the TF-1 IDH2 R140Q erythroleukemia model system and found that IDH2 mutant expression caused both histone and genomic DNA methylation changes that can be reversed when IDH2 mutant activity is inhibited. Specifically, histone hypermethylation is rapidly reversed within days, whereas reversal of DNA hypermethylation proceeds in a progressive manner over the course of weeks. We identified several gene signatures implicated in tumorigenesis of leukemia and lymphoma, indicating a selective modulation of relevant cancer genes by IDH mutations. As methylation of DNA and histones is closely linked to mRNA expression and differentiation, these results indicate that IDH2 mutant inhibition may function as a cancer therapy via histone and DNA demethylation at genes involved in differentiation and tumorigenesis.

Isocitrate dehydrogenase 1 (IDH1) mutation in breast adenocarcinoma is associated with elevated levels of serum and urine 2-hydroxyglutarate.

Mutations in the IDH1 and IDH2 (isocitrate dehydrogenase) genes have been discovered across a range of solid-organ and hematologic malignancies, including acute myeloid leukemia, glioma, chondrosarcoma, and cholangiocarcinoma. An intriguing aspect of IDH-mutant tumors is the aberrant production and accumulation of the oncometabolite 2-hydroxyglutarate (2-HG), which may play a pivotal oncogenic role in these malignancies. We describe the first reported case of an IDH1 p.R132L mutation in a patient with hormone receptor-positive (HR+) breast adenocarcinoma. This patient was initially treated for locally advanced disease, but then suffered a relapse and metastasis, at which point an IDH1-R132 mutation was discovered in an affected lymph node. The mutation was subsequently found in the primary tumor tissue and all metastatic sites, but not in an uninvolved lymph node. In addition, the patient's serum and urine displayed marked elevations in the concentration of 2-HG, significantly higher than that measured in six other patients with metastatic HR+ breast carcinoma whose tumors were found to harbor wild-type IDH1. In summary, IDH1 mutations may impact a rare subgroup of patients with breast adenocarcinoma. This may suggest future avenues for disease monitoring through noninvasive measurement of 2-HG, as well as for the development and study of targeted therapies against the aberrant IDH1 enzyme.

Prospective serial evaluation of 2-hydroxyglutarate, during treatment of newly diagnosed acute myeloid leukemia, to assess disease activity and therapeutic response.

Mutations of genes encoding isocitrate dehydrogenase (IDH1 and IDH2) have been recently described in acute myeloid leukemia (AML). Serum and myeloblast samples from patients with IDH-mutant AML contain high levels of the metabolite 2-hydroxyglutarate (2-HG), a product of the altered IDH protein. In this prospective study, we sought to determine whether 2-HG can potentially serve as a noninvasive biomarker of disease burden through serial measurements in patients receiving conventional therapy for newly diagnosed AML. Our data demonstrate that serum, urine, marrow aspirate, and myeloblast 2-HG levels are significantly higher in IDH-mutant patients, with a correlation between baseline serum and urine 2-HG levels. Serum and urine 2-HG, along with IDH1/2-mutant allele burden in marrow, decreased with response to treatment. 2-HG decrease was more rapid with induction chemotherapy compared with DNA-methyltransferase inhibitor therapy. Our data suggest that serum or urine 2-HG may serve as noninvasive biomarkers of disease activity for IDH-mutant AML.

Frequent mutation of isocitrate dehydrogenase (IDH)1 and IDH2 in cholangiocarcinoma identified through broad-based tumor genotyping.

Cancers of origin in the gallbladder and bile ducts are rarely curable with current modalities of cancer treatment. Our clinical application of broad-based mutational profiling for patients diagnosed with a gastrointestinal malignancy has led to the novel discovery of mutations in the gene encoding isocitrate dehydrogenase 1 (IDH1) in tumors from a subset of patients with cholangiocarcinoma. A total of 287 tumors from gastrointestinal cancer patients (biliary tract, colorectal, gastroesophageal, liver, pancreatic, and small intestine carcinoma) were tested during routine clinical evaluation for 130 site-specific mutations within 15 cancer genes. Mutations were identified within a number of genes, including KRAS (35%), TP53 (22%), PIK3CA (10%), BRAF (7%), APC (6%), NRAS (3%), AKT1 (1%), CTNNB1 (1%), and PTEN (1%). Although mutations in the metabolic enzyme IDH1 were rare in the other common gastrointestinal malignancies in this series (2%), they were found in three tumors (25%) of an initial series of 12 biliary tract carcinomas. To better define IDH1 and IDH2 mutational status, an additional 75 gallbladder and bile duct cancers were examined. Combining these cohorts of biliary cancers, mutations in IDH1 and IDH2 were found only in cholangiocarcinomas of intrahepatic origin (nine of 40, 23%) and in none of the 22 extrahepatic cholangiocarcinomas and none of the 25 gallbladder carcinomas. In an analysis of frozen tissue specimens, IDH1 mutation was associated with highly elevated tissue levels of the enzymatic product 2-hydroxyglutarate. Thus, IDH1 mutation is a molecular feature of cholangiocarcinomas of intrahepatic origin. These findings define a specific metabolic abnormality in this largely incurable type of gastrointestinal cancer and present a potentially new target for therapy.

Non-invasive detection of 2-hydroxyglutarate and other metabolites in IDH1 mutant glioma patients using magnetic resonance spectroscopy.

Mutations of the isocitrate dehydrogenase 1 and 2 genes (IDH1 and IDH2) are commonly found in primary brain cancers. We previously reported that a novel enzymatic activity of these mutations results in the production of the putative oncometabolite, R(-)-2-hydroxyglutarate (2-HG). Here we investigated the ability of magnetic resonance spectroscopy (MRS) to detect 2-HG production in order to non-invasively identify patients with IDH1 mutant brain tumors. Patients with intrinsic glial brain tumors (n = 27) underwent structural and spectroscopic magnetic resonance imaging prior to surgery. 2-HG levels from MRS data were quantified using LC-Model software, based upon a simulated spectrum obtained from a GAMMA library added to the existing prior knowledge database. The resected tumors were then analyzed for IDH1 mutational status by genomic DNA sequencing, Ki-67 proliferation index by immunohistochemistry, and concentrations of 2-HG and other metabolites by liquid chromatography-mass spectrometry (LC-MS). MRS detected elevated 2-HG levels in gliomas with IDH1 mutations compared to those with wild-type IDH1 (P = 0.003). The 2-HG levels measured in vivo with MRS were significantly correlated with those measured ex vivo from the corresponding tumor samples using LC-MS (r (2) = 0.56; P = 0.0001). Compared with wild-type tumors, those with IDH1 mutations had elevated choline (P = 0.01) and decreased glutathione (P = 0.03) on MRS. Among the IDH1 mutated gliomas, quantitative 2-HG values were correlated with the Ki-67 proliferation index of the tumors (r ( 2 ) = 0.59; P = 0.026). In conclusion, water-suppressed proton ((1)H) MRS provides a non-invasive measure of 2-HG in gliomas, and may serve as a potential biomarker for patients with IDH1 mutant brain tumors. In addition to 2-HG, alterations in several other metabolites measured by MRS correlate with IDH1 mutation status.

A phase 2 study of bortezomib in relapsed, refractory myeloma.

BACKGROUND: Bortezomib, a boronic acid dipeptide, is a novel proteasome inhibitor that has been shown in preclinical and phase 1 studies to have antimyeloma activity. METHODS: In this multicenter, open-label, nonrandomized, phase 2 trial, we enrolled 202 patients with relapsed myeloma that was refractory to the therapy they had received most recently. Patients received 1.3 mg of bortezomib per square meter of body-surface area twice weekly for 2 weeks, followed by 1 week without treatment, for up to eight cycles (24 weeks). In patients with a suboptimal response, oral dexamethasone (20 mg daily, on the day of and the day after bortezomib administration) was added to the regimen. The response was evaluated according to the criteria of the European Group for Blood and Marrow Transplantation and confirmed by an independent review committee. RESULTS: Of 193 patients who could be evaluated, 92 percent had been treated with three or more of the major classes of agents for myeloma, and in 91 percent, the myeloma was refractory to the therapy received most recently. The rate of response to bortezomib was 35 percent, and those with a response included 7 patients in whom myeloma protein became undetectable and 12 in whom myeloma protein was detectable only by immunofixation. The median overall survival was 16 months, with a median duration of response of 12 months. Grade 3 adverse events included thrombocytopenia (in 28 percent of patients), fatigue (in 12 percent), peripheral neuropathy (in 12 percent), and neutropenia (in 11 percent). Grade 4 events occurred in 14 percent of patients. CONCLUSIONS: Bortezomib, a member of a new class of anticancer drugs, is active in patients with relapsed multiple myeloma that is refractory to conventional chemotherapy.

Bortezomib in combination with dexamethasone for the treatment of patients with relapsed and/or refractory multiple myeloma with less than optimal response to bortezomib alone.

BACKGROUND AND OBJECTIVES: The efficacy and safety of added dexamethasone were assessed in patients with relapsed and/or refractory multiple myeloma who had a suboptimal response to bortezomib alone. DESIGN AND METHODS: In two previously reported, open-label, multicenter phase 2 studies, bortezomib 1.0 or 1.3 mg/m2 was administered intravenously twice weekly for 2 weeks of a 3-week cycle for up to 8 cycles to patients who had failed either > or = 2 lines of therapy (SUMMIT, n=202) or first-line therapy (CREST, n=54). Patients with progressive disease after the first two cycles or stable disease after four cycles of bortezomib were eligible for addition of oral dexamethasone 20 mg on the day of and after each bortezomib dose. Responses were assessed by an Independent Review Committee using European Group for Blood and Marrow Transplantation criteria. RESULTS: Addition of dexamethasone to bortezomib was associated with improved responses in 13 of 74 evaluable patients (18%) in SUMMIT and 9 of 27 (33%) in CREST; eight of these 22 patients had been previously refractory to dexamethasone. There were 2 complete, 8 partial, and 12 minimal responses. Dexamethasone did not appear to alter the type or number of adverse events. Treatment-emergent adverse events reported in > or = 20% of patients receiving combination therapy were fatigue (25%), thrombocytopenia (24%), insomnia (21%), and nausea (20%). INTERPRETATION AND CONCLUSIONS: Addition of dexamethasone to bortezomib in patients with relapsed and/or refractory myeloma who had suboptimal responses to bortezomib alone was associated with improvement in responses without prohibitive toxicity.

Preclinical data with bortezomib in lung cancer.

More effective therapies are needed for non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). Proteasome inhibitors are one class of molecularly targeted antineoplastic agents being investigated for these diseases. These agents block the activity of the 26S proteasome, which is responsible for the degradation of the vast majority of intracellular proteins and thus affect multiple signaling pathways within cells. Bortezomib is the first proteasome inhibitor to be evaluated in human studies and is approved for use in multiple myeloma. Bortezomib is now being investigated as a potential treatment for NSCLC and SCLC. Preclinical studies have shown that single-agent bortezomib causes growth inhibition and apoptosis in numerous NSCLC cell lines in vitro and has antitumor activity in vivo. Bortezomib affects the levels of several proteins known to be of significance in lung cancers. Studies of bortezomib in combination with other antitumor agents in vitro and in vivo demonstrate that these combination regimens can offer additive/synergistic effects compared with the single agents. Bortezomib has been investigated in combination with taxanes, gemcitabine, carboplatin, histone deactylase inhibitors, and other molecularly targeted agents in various NSCLC cell lines. The sequence of administration of the agents in preclinical combination regimens in vitro and in vivo has been shown to be of significance; further elucidation of the mechanism of efficacy of bortezomib in lung cancer is required. Numerous clinical studies have been carried out or are ongoing. Bortezomib has the potential to play a significant role in the future management of NSCLC and SCLC.

Targeted therapies for cancer 2004.

The regulatory agency approvals in the United States and Europe of imatinib mesylate (Gleevec) for patients with bcr/abl-positive chronic myelogenous leukemia, cetuximab (Erbitux) for patients with epidermal growth factor receptor overexpressing metastatic colorectal cancer, the antiangiogenesis agent bevacizumab (Avastin), and the proteasome inhibitor bortezomib (Velcade)--and the considerable public interest in new anticancer drugs that take advantage of specific genetic defects that render the malignant cells more likely to respond to specific treatment--are driving a new era of integrated diagnostics and therapeutics. The recent discovery of a drug response predicting activating mutation in the epidermal growth factor receptor gene for patients with non-small cell lung cancer treated with gefitinib (Iressa) has intensified this interest. In this review, the history of targeted anticancer therapies is highlighted, with focus on the development of molecular diagnostics for hematologic malignancies and the emergence of trastuzumab (Herceptin), an antibody-based targeted therapy for HER-2/neu overexpressing metastatic breast cancer: The potential of pharmacogenomic strategies and the use of high-density genomic microarrays to classify and select therapy for cancer are briefly considered. This review also considers the widely held view that, in the next 5 to 10 years, the clinical application of molecular diagnostics will further revolutionize the drug discovery and development process; customize the selection, dosing, route of administration of existing and new therapeutic agents; and truly personalize medical care for cancer patients.

Use of proteasome inhibition in the treatment of lung cancer.

The proteasome plays a critical role in the degradation of proteins involved in the regulation of cell cycle, apoptosis, and angiogenesis. Bortezomib is the first in a new class of antineoplastic agents known as proteasome inhibitors to become available for clinical use. Bortezomib targets pathways relevant to tumor progression and therapy resistance and can directly modulate expression of cyclins, p27kip1, p53, nuclear factor-kB, Bcl-2, and Bax. In in vitro and in vivo, growth inhibition and apoptosis have been observed in tumor cells following exposure to bortezomib. Currently, bortezomib is approved for the treatment of patients with relapsed and/or refractory multiple myeloma who have received > or =2 therapies and progressed on their most recent therapy. Efforts are now being directed toward exploring the use of bortezomib in the treatment of advanced non-small-cell lung cancer (NSCLC). Clinical trials using bortezomib as monotherapy or in combinations, such as with taxanes, gemcitabine and platinums, and novel agents are under way, and preliminary results have demonstrated activity with bortezomib as a single agent and in combination with chemotherapy in advanced NSCLC. In addition, pharmacogenomics and biomarker analysis are being used in an attempt to identify tumor types likely to respond to treatment with bortezomib.

Circulating oncometabolite 2-hydroxyglutarate is a potential surrogate biomarker in patients with isocitrate dehydrogenase-mutant intrahepatic cholangiocarcinoma.

PURPOSE: Mutations in the IDH1 and IDH2 (IDH1/2) genes occur in approximately 20% of intrahepatic cholangiocarcinoma and lead to accumulation of 2-hydroxyglutarate (2HG) in the tumor tissue. However, it remains unknown whether IDH1/2 mutations can lead to high levels of 2HG circulating in the blood and whether serum 2HG can be used as a biomarker for IDH1/2 mutational status and tumor burden in intrahepatic cholangiocarcinoma. EXPERIMENTAL DESIGN: We initially measured serum 2HG concentration in blood samples collected from 31 patients with intrahepatic cholangiocarcinoma in a screening cohort. Findings were validated across 38 resected patients with intrahepatic cholangiocarcinoma from a second cohort with tumor volume measures. Circulating levels of 2HG were evaluated relative to IDH1/2 mutational status, tumor burden, and a number of clinical variables. RESULTS: Circulating levels of 2HG in the screening cohort were significantly elevated in patients with IDH1/2-mutant (median, 478 ng/mL) versus IDH1/2-wild-type (median, 118 ng/mL) tumors (P < 0.001). This significance was maintained in the validation cohort (343 ng/mL vs. 55 ng/mL, P < 0.0001) and levels of 2HG directly correlated with tumor burden in IDH1/2-mutant cases (P < 0.05). Serum 2HG levels ≥170 ng/mL could predict the presence of an IDH1/2 mutation with a sensitivity of 83% and a specificity of 90%. No differences were noted between the allelic variants IDH1 or IDH2 in regard to the levels of circulating 2HG. CONCLUSIONS: This study indicates that circulating 2HG may be a surrogate biomarker of IDH1 or IDH2 mutation status in intrahepatic cholangiocarcinoma and that circulating 2HG levels may correlate directly with tumor burden. Clin Cancer Res; 20(7); 1884-90. ©2014 AACR.

Reevaluating the accelerated approval process for oncology drugs.

For a new therapy to qualify for the accelerated approval pathway, it must treat a serious disease for which there is "unmet medical need"--defined as providing a therapy where none exists or providing a therapy that may be potentially superior to existing therapy. The increasing number of available therapies, coupled with the lack of accepted endpoints considered "reasonably likely to predict clinical benefit" and the lack of clarity early in development about circumstances in which a new product will qualify for accelerated approval, is pushing developers to pursue accelerated approval in heavily pretreated patients to fulfill an unmet need. To optimize the accelerated approval pathway, we propose here a reevaluation of what constitutes "unmet medical need" and "available therapy" in oncology. We also discuss ways for new endpoints to become qualified for use in supporting accelerated approval, and propose a structured process for pursuing accelerated approval.

Considerations for the successful co-development of targeted cancer therapies and companion diagnostics.

As diagnostic tests become increasingly important for optimizing the use of drugs to treat cancers, the co-development of a targeted therapy and its companion diagnostic test is becoming more prevalent and necessary. In July 2011, the US Food and Drug Administration released a draft guidance that gave the agency's formal definition of companion diagnostics and introduced a drug-diagnostic co-development process for gaining regulatory approval. Here, we identify areas of drug-diagnostic co-development that were either not covered by the guidance or that would benefit from increased granularity, including how to determine when clinical studies should be limited to biomarker-positive patients, defining the diagnostically selected patient population in which to use a companion diagnostic, and defining and clinically validating a biomarker signature for assays that use more than one biomarker. We propose potential approaches that sponsors could use to deal with these challenges and provide strategies to help guide the future co-development of drugs and diagnostics.

Targeted inhibition of mutant IDH2 in leukemia cells induces cellular differentiation.

A number of human cancers harbor somatic point mutations in the genes encoding isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2). These mutations alter residues in the enzyme active sites and confer a gain-of-function in cancer cells, resulting in the accumulation and secretion of the oncometabolite (R)-2-hydroxyglutarate (2HG). We developed a small molecule, AGI-6780, that potently and selectively inhibits the tumor-associated mutant IDH2/R140Q. A crystal structure of AGI-6780 complexed with IDH2/R140Q revealed that the inhibitor binds in an allosteric manner at the dimer interface. The results of steady-state enzymology analysis were consistent with allostery and slow-tight binding by AGI-6780. Treatment with AGI-6780 induced differentiation of TF-1 erythroleukemia and primary human acute myelogenous leukemia cells in vitro. These data provide proof-of-concept that inhibitors targeting mutant IDH2/R140Q could have potential applications as a differentiation therapy for cancer.

Cancer-associated metabolite 2-hydroxyglutarate accumulates in acute myelogenous leukemia with isocitrate dehydrogenase 1 and 2 mutations.

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2), are present in most gliomas and secondary glioblastomas, but are rare in other neoplasms. IDH1/2 mutations are heterozygous, and affect a single arginine residue. Recently, IDH1 mutations were identified in 8% of acute myelogenous leukemia (AML) patients. A glioma study revealed that IDH1 mutations cause a gain-of-function, resulting in the production and accumulation of 2-hydroxyglutarate (2-HG). Genotyping of 145 AML biopsies identified 11 IDH1 R132 mutant samples. Liquid chromatography-mass spectrometry metabolite screening revealed increased 2-HG levels in IDH1 R132 mutant cells and sera, and uncovered two IDH2 R172K mutations. IDH1/2 mutations were associated with normal karyotypes. Recombinant IDH1 R132C and IDH2 R172K proteins catalyze the novel nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reduction of alpha-ketoglutarate (alpha-KG) to 2-HG. The IDH1 R132C mutation commonly found in AML reduces the affinity for isocitrate, and increases the affinity for NADPH and alpha-KG. This prevents the oxidative decarboxylation of isocitrate to alpha-KG, and facilitates the conversion of alpha-KG to 2-HG. IDH1/2 mutations confer an enzymatic gain of function that dramatically increases 2-HG in AML. This provides an explanation for the heterozygous acquisition of these mutations during tumorigenesis. 2-HG is a tractable metabolic biomarker of mutant IDH1/2 enzyme activity.

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 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.

Roles of tyrosine 589 and 591 in STAT5 activation and transformation mediated by FLT3-ITD.

Acquired mutations in the FLT3 receptor tyrosine kinase are common in acute myeloid leukemia and result in constitutive activation. The most frequent mechanism of activation is disruption of the juxtamembrane autoregulatory domain by internal tandem duplications (ITDs). FLT3-ITDs confer factor-independent growth to hematopoietic cells and induce a myeloproliferative syndrome in murine bone marrow transplant models. We and others have observed that FLT3-ITD activates STAT5 and its downstream effectors, whereas ligand-stimulated wild-type FLT3 (FLT3WT) does not. In vitro mapping of tyrosine phosphorylation sites in FLT3-ITD identified 2 candidate STAT5 docking sites within the juxtamembrane domain that are disrupted by the ITD. Tyrosine to phenylalanine substitution of residues 589 and 591 in the context of the FLT3-ITD did not affect tyrosine kinase activity, but abrogated STAT5 activation. Furthermore, FLT3-ITD-Y589/591F was incapable of inducing a myeloproliferative phenotype when transduced into primary murine bone marrow cells, whereas FLT3-ITD induced myeloproliferative disease with a median latency of 50 days. Thus, the conformational change in the FLT3 juxtamembrane domain induced by the ITD activates the kinase through dysregulation of autoinhibition and results in qualitative differences in signal transduction through STAT5 that are essential for the transforming potential of FLT3-ITD in vivo.

Antibody-based therapeutics: focus on prostate cancer.

The recent clinical and commercial success of anti-cancer antibodies such as rituximab, trastuzumab, cetuximab and bevacizumab has continued to foster great interest in antibody-based therapeutics for the treatment of both hematopoietic malignancies and solid tumors. Given the likely lower toxicity for antibodies which, in contrast with traditional cytotoxic small molecule drugs, target tumor cells and have a lower impact on non-malignant by-stander organs, the potential increases in efficacy associated with conjugation to radioisotopes and other cellular toxins and the ability to characterize the target with clinical laboratory diagnostics to improve the drugs clinical performance, it is anticipated that current and future antibody therapeutics will find substantial roles alone and in combination therapy strategies for the treatment of patients with cancer. A significant number of cell surface proteins, glycoproteins, receptors, enzymes and peptides have been discovered that have become targets for the treatment of advanced hormone-refractory prostate cancer. A variety of naked antibodies and antibody conjugates have currently progressed through preclinical development and are in early or more advanced stages of clinical development. Clinicians, scientists and prostate cancer patients are all keenly interested to learn whether these agents when administered alone or in combination with other hormonal-based and cytotoxic therapies will show lasting benefit for sufferers of this common disease.

Safety of prolonged therapy with bortezomib in relapsed or refractory multiple myeloma.

BACKGROUND: Bortezomib, a first-in-class proteasome inhibitor, is active with manageable toxicities in relapsed and/or refractory myeloma. METHODS: Bortezomib 1.0 or 1.3 mg/m2 was administered Days 1, 4, 8, and 11 every 21 days for up to 8 cycles to patients with relapsed and/or refractory myeloma participating in two Phase II trials. Dexamethasone could be added because of progressive disease after 2 cycles or stable disease after 4 cycles. Continuation of or retreatment with bortezomib was offered to patients who, in the investigator's opinion, would benefit from extended treatment. RESULTS: Sixty-three patients with relapsed/refractory myeloma treated in this extension trial received a median of 7 additional cycles of therapy, for a total of 14 cycles (range, 7-32) over a median duration of therapy of 45.1 weeks in the parent and extension studies. Seventy-eight percent of patients completed this study at the same or higher bortezomib dose than they started on during this study, and the treatment schedule of twice-weekly administration remained unchanged in 89%. Overall, 75% of patients received dexamethasone in combination with bortezomib for a median of 5 cycles starting either in the parent or extension study. The safety profile was similar between the extension and parent trials, with no evidence of new cumulative toxicity. The most commonly reported Grade 3/4 toxicities were thrombocytopenia (29%), with a consistent pattern of recovery during the rest period of each cycle, diarrhea (11%), anemia (11%), and neutropenia (10%). Neuropathy was reported less frequently. CONCLUSIONS: Retreatment with or continuation of bortezomib +/- dexamethasone beyond 6 months was safe, and toxicities were manageable, in patients with relapsed and/or refractory myeloma.