Influence of unrecognized molecular heterogeneity on randomized clinical trials

Identification of candidate predictive and surrogate molecular markers for dasatinib in prostate cancer: rationale for patient selection and efficacy monitoring

BACKGROUND

Dasatinib is a potent, multi-targeted kinase inhibitor that was recently approved for treatment of chronic myelogenous leukemia resistant to imatinib. To aid the clinical development of dasatinib in prostate cancer, we utilized preclinical models to identify potential molecular markers for patient stratification and efficacy monitoring.

RESULTS

Using gene expression profiling, we first identified 174 genes whose expression was highly correlated with in vitro sensitivity of 16 cell lines and, thus, considered as candidate efficacy predictive markers. Among these are important prostatic cell lineage markers, cytokeratin 5, androgen receptor and prostate specific antigen. Our results indicate that 'basal type' cell lines with high expression of cytokeratin 5 and low expression of androgen receptor or prostate specific antigen are sensitive to dasatinib. To identify markers as surrogates for biological activity, we treated cell lines with dasatinib and identified genes whose expression was significantly modulated by the drug. Ten genes, including that encoding urokinase-type plasminogen activator (uPA), were found to not only be potential efficacy markers but also to have reduced expression upon dasatinib treatment. The down-regulation of uPA by dasatinib was drug-specific and correlated with the sensitivity of cell lines to dasatinib. Furthermore, EphA2, a target of dasatinib, was found to be a sensitivity biomarker.

CONCLUSION

Using the gene expression profiling approach and preclinical models, we have identified prostatic biomarkers that are associated with sensitivity to dasatinib. This study has provided a basis for clinical evaluation of a potential dasatinib efficacy signature in prostate cancer.

Phase 0 clinical trials: conceptions and misconceptions

Phase 0 clinical trials, developed in response to the United States Food and Drug Administration (FDA)'s recent exploratory Investigational New Drug (IND) guidance, are intended to expedite the clinical evaluation of new molecular entities. The exploratory IND supports the performance of first-in-human testing of new investigational agents at subtherapeutic doses based on reduced manufacturing and toxicologic requirements, allowing the demonstration of drug-target effects and assessment of pharmacokinetic-pharmacodynamic relationships in humans earlier in clinical development. The objectives of a phase 0 cancer clinical trial are to establish at the very earliest opportunity-before large numbers of patients have been accrued and exposed to potential drug-associated toxicity-whether an agent is modulating its target in a tumor, and consequently whether further clinical development is warranted. We review here the fundamental requirements of clinical studies conducted under an exploratory IND and address some common misconceptions regarding oncologic phase 0 trials.

Systematic Survey of Therapeutic Trials for Metastatic Colorectal Cancer: Room for Improvement in the Critical Pathway

Purpose

The current strategy of drug development has been criticized as being highly inefficient. In 2004, the US Food and Drug Administration (FDA) released recommendations to improve this process, including a push for increased use of enrichment trials. It is unclear to what extent aspects of this “Critical Path Initiative” have been adopted in trial designs in metastatic colorectal cancer.

Methods

A systematic review was conducted of actively enrolling treatment trials in metastatic colorectal cancer. Trials were identified from the National Cancer Institute's clinicaltrials.gov and Investigative Drug Branch databases. Trials were categorized based on the number of prior treatments allowed, phase of the trial, agent mechanism of action, and FDA approval status of agents under investigation.

Results

One hundred two trials are enrolling, with a combined enrollment goal of more than 20,000 patients. Thirteen percent of trials investigated an agent not yet FDA-approved for any oncology indication. The most common study design was a phase II study limited to previously untreated patients; compared with the remaining trials, these phase II trials were more than 10 times more likely to only use agents FDA-approved for colorectal cancer. Three percent of patients were enrolled onto trials enriched for tumor characteristics that were hypothesized to improve clinical benefit.

Conclusion

Current clinical trials for metastatic colorectal cancer are deficient in the investigation of agents directed at a novel therapeutic target, overuse phase II studies of FDA-approved agents, and fail to incorporate enrichment trial designs as encouraged by the FDA initiative.

Opportunities posed by novel patient selection biomarker approaches in oncology drug development: going beyond the cytotoxics

An area of unmet medical need in clinical oncology has been optimizing patient selection for a given therapeutic with the goal of getting the right drug to the right patient. Recent studies have developed preclinical approaches to identifying molecular ‘signatures of resistance’ for cytotoxic therapies and prospective validation of this strategy is ongoing in the clinic. New challenges in this setting include identifying approaches to patient selection for cytostatic compounds such as signaling pathway inhibitors and stem cell targets. Here, we discuss the biomarker methodologies developed using traditional cytotoxic drugs and how these approaches can be adapted to identify biomarkers of patient selection for novel signaling inhibitors and other novel targets. It has become increasingly clear that such biomarker discovery and validation needs to begin early and continue throughout the drug development process.

Is human hepatocellular carcinoma a hormone-responsive tumor?

Before the positive results recently obtained with multitarget tyrosine kinase inhibitor sorafenib, there was no standard systemic treatment for patients with advanced hepatocellular carcinoma (HCC). Sex hormones receptors are expressed in a significant proportion of HCC samples. Following preclinical and epidemiological studies supporting a relationship between sex hormones and HCC tumorigenesis, several randomized controlled trials (RCTs) tested the efficacy of the anti-estrogen tamoxifen as systemic treatment. Largest among these trials showed no survival advantage from the administration of tamoxifen, and the recent Cochrane systematic review produced a completely negative result. This questions the relevance of estrogen receptor-mediated pathways in HCC. However, a possible explanation for these disappointing results is the lack of proper patients selection according to sex hormones receptors expression, but unfortunately the interaction between this expression and efficacy of tamoxifen has not been studied adequately. It has been also proposed that negative results might be explained if tamoxifen acts in HCC via an estrogen receptor-independent pathway, that requires higher doses than those usually administered, but an Asian RCT conducted to assess dose-response effect was completely negative. Interesting, preliminary results have been obtained when hormonal treatment (tamoxifen or megestrol) has been selected according to the presence of wild-type or variant estrogen receptors respectively, but no large RCTs are available to support this strategy. Negative results have been obtained also with anti-androgen therapy. In conclusion, there is no robust evidence to consider HCC a hormone-responsive tumor. Hormonal treatments should not be part of the current management of HCC.

Methodology of clinical trials with new molecular-targeted agents: where do we stand?

In recent years, we have witnessed growing interest in the methodology of clinical trials with molecular-targeted agents. In phase I studies, alternative end points to toxicity have been proposed to define the optimal biological dose: the identification of a 'target effect', the measurement of 'surrogates' for biological activity and the assessment of drug plasma levels. However, these end points are not routinely incorporated into the study design and have rarely formed the primary basis for dose selection. In phase II studies, response rate remains the preferred end point in the early evaluation of new drugs. However, this approach might lead to rejection of potentially useful drugs when significant tumor shrinkage cannot be demonstrated. Therefore, a number of alternative end points have been proposed for agents that are not expected to cause a major tumor regression: time to progression, progression-free survival, overall survival, early progression rate and growth modulation index. In phase III trials, where efficacy in terms of survival remains the most important goal of the research, the major issues are the adequate selection of patients and the optimal clinical setting of evaluation of drugs. In conclusion, many important questions regarding the methodology of clinical research with target-based agents remain open and need to be defined by research in the near future.

Expression and prognostic significance of a panel of tissue hypoxia markers in head-and-neck squamous cell carcinomas

PURPOSE

To investigate the expression pattern of hypoxia-induced proteins identified as being involved in malignant progression of head-and-neck squamous cell carcinoma (HNSCC) and to determine their relationship to tumor pO(2) and prognosis.

METHODS AND MATERIALS

We performed immunohistochemical staining of hypoxia-induced proteins (carbonic anhydrase IX [CA IX], BNIP3L, connective tissue growth factor, osteopontin, ephrin A1, hypoxia inducible gene-2, dihydrofolate reductase, galectin-1, IkappaB kinase beta, and lysyl oxidase) on tumor tissue arrays of 101 HNSCC patients with pretreatment pO(2) measurements. Analysis of variance and Fisher's exact tests were used to evaluate the relationship between marker expression, tumor pO(2), and CA IX staining. Cox proportional hazard model and log-rank tests were used to determine the relationship between markers and prognosis.

RESULTS

Osteopontin expression correlated with tumor pO(2) (Eppendorf measurements) (p = 0.04). However, there was a strong correlation between lysyl oxidase, ephrin A1, and galectin-1 and CA IX staining. These markers also predicted for cancer-specific survival and overall survival on univariate analysis. A hypoxia score of 0-5 was assigned to each patient, on the basis of the presence of strong staining for these markers, whereby a higher score signifies increased marker expression. On multivariate analysis, increasing hypoxia score was an independent prognostic factor for cancer-specific survival (p = 0.015) and was borderline significant for overall survival (p = 0.057) when adjusted for other independent predictors of outcomes (hemoglobin and age).

CONCLUSIONS

We identified a panel of hypoxia-related tissue markers that correlates with treatment outcomes in HNSCC. Validation of these markers will be needed to determine their utility in identifying patients for hypoxia-targeted therapy.

The randomized discontinuation trial: a phase II design to assess growth-inhibitory agents: Figure 1

An increasing number of putative anticancer targets and drugs have been identified with many of these expected to be growth inhibitory. Clinical development of these agents in the phase II setting is challenging because tumor shrinkages, or at least tumor shrinkages that meet the standard definitions of objective response, are not expected. Time to progression end points are however problematic because expected times in the absence of therapy (the null hypothesis) cannot be predicted accurately, thus requiring trials to enroll a concurrent control group. Another problem is that the patient population that will benefit from a new drug remains poorly defined in early-phase development. The randomized discontinuation trial design addresses both of these issues. All patients are initially treated with the drug; patients with an objective response continue therapy; patients who do not progress or experience excess toxicity within a prespecified "run-in" period are then randomized to continuing or discontinuing therapy in a double-blind, placebo controlled manner. Despite certain limitations that need to be recognized, the ability of this design to "select" a cohort most likely to benefit and to rigorously evaluate the disease-stabilizing activity of an investigational agent provides multiple advantages.

Principes et intérêts pour l’étude des maladies neurologiques et technologie des puces ADN

INTRODUCTION

DNA microarray is a powerful technology which can rapidly provide a high throughput and detailed view of the entire genome and transcriptome. In this review we discuss the basic principles behind gene expression microarrays, CGH arrays and DNA microarray genotyping, and their potential applications to neurological diseases.

STATE OF THE ART

Microarray gene expression profiling is a reliable technology that has already been used with great success in the molecular classification of cancer. It is a very promising technology in the field of Neurooncology. One of the interesting characteristics of DNA microarrays is also that they can be used in a non-hypothesis-driven manner to discover new genomic characteristics that will enable to establish new pathophysiological hypotheses. Such a strategy has already yielded interesting new insights in the study of multiple sclerosis, Alzheimer disease or neuromuscular diseases. With DNA microarray genotyping it is now possible to detect mutations in many genes simultaneously.

CONCLUSIONS

In Neurooncology DNA microarrays should help to establish a more accurate classification of brain tumors and recent studies have shown how gene expression profiling of brain tumors allows to uncover previously unrecognized patient subsets that differ in their survival. The applications of microarrays for the study of neurological diseases, like multiple sclerosis, Alzheimer disease or neuromuscular diseases are also promising both for generating new pathophysiological hypotheses and for enabling new molecular classifications. DNA microarray genotyping is a powerful technology that should help to discover genetic factors associated with multifactorial neurological disorders and help to diagnose complex neurogenetic diseases. This technology should also facilitate the realization of pharmacogenomic studies in neurological diseases.

Hormonal treatment of human hepatocellular carcinoma

Animal models of experimental liver carcinogenesis and epidemiological studies in humans suggest a relationship between sex hormones and hepatocellular carcinoma (HCC). In 1997, a systematic review of the existing, small randomized trials evaluating the antiestrogen tamoxifen yielded a positive result, but the large randomized CLIP-1 trial showed no survival advantage from the addition of tamoxifen to best supportive care. A possible explanation for the negative results is the lack of patient selection, but the expression of estrogen (ER) and progesterone (PgR) receptors in HCC does not clearly affect the survival outcome of the patients treated with tamoxifen. In the last years, it has been proposed that negative results might be due to the fact that tamoxifen in HCC could act via an ER-independent pathway, which requires much higher doses than those usually administered, but a double-blind Asian randomized trial conducted to assess possible dose-response effect showed no efficacy for tamoxifen, with an inversely negative impact with increasing dose. According to the results of large trials and of the Cochrane systematic review, neither further trials are warranted with tamoxifen in HCC, nor should any use in clinical practice be considered. Interesting results have been obtained when the type of hormonal treatment (tamoxifen or megestrol) has been chosen according to the presence of wild-type or variant ER, but these results should be confirmed in large randomized trials. Negative results have been obtained with antiandrogen therapy. In conclusion, hormonal treatment should not be a part of the current management of HCC patients.

DNA-encoded antibody libraries: a unified platform for multiplexed cell sorting and detection of genes and proteins

Whether for pathological examination or for fundamental biology studies, different classes of biomaterials and biomolecules are each measured from a different region of a typically heterogeneous tissue sample, thus introducing unavoidable sources of noise that are hard to quantitate. We describe the method of DNA-encoded antibody libraries (DEAL) for spatially multiplexed detection of ssDNAs and proteins as well as for cell sorting, all on the same diagnostic platform. DEAL is based upon the coupling of ssDNA oligomers onto antibodies which are then combined with the biological sample of interest. Spotted DNA arrays, which are found to inhibit biofouling, are utilized to spatially stratify the biomolecules or cells of interest. We demonstrate the DEAL technique for (1) the rapid detection of multiple proteins within a single microfluidic channel, and, with the additional step of electroless amplification of gold-nanoparticle labeled secondary antibodies, we establish a detection limit of 10 fM for the protein IL-2, 150 times more sensitive than the analogue ELISA; (2) the multiplexed, on-chip sorting of both immortalized cell lines and primary immune cells with an efficiency that exceeds surface-confined panning approaches; and (3) the co-detection of ssDNAs, proteins, and cell populations on the same platform.

Molecular genetics of pediatric central nervous system tumors

Recent advances in molecular biology have enhanced our understanding of the pathogenesis of brain tumors, particularly in children. The use of molecular diagnostic tools is quickly becoming a standard component in the diagnosis and classification of brain tumors in children, in addition to providing insight leading to treatment stratification and improved outcome prediction. All new protocols involving treatments for brain tumors in children include studies of biomarkers and biologic correlates as a means to identify new targets for therapeutics and possible intervention strategies.

Drug development in oncology: classical cytotoxics and molecularly targeted agents

There is an apparent need to improve the speed and efficiency of oncological drug development. Furthermore, strategies traditionally applied to the development of standard cytotoxic chemotherapy may not be appropriate for molecularly targeted agents. This is particularly the case for exploratory Phase 1 and 2 trials. Conventional approaches to determine dose based on maximum tolerability and efficacy based on objective tumour response may not be suitable for targeted agents, since many of them have a wide therapeutic index and inhibit tumour growth without demonstrable cytotoxicity. Instead, exploratory trials of targeted agents may have to focus on other end-points such as pharmacological effects and disease stabilization. Thus, there is an increasing interest in making the best possible use of biomarkers and pharmacogenomics in early phases of drug development.

Effects of unmeasured heterogeneity in the linear transformation model for censored data

We investigate the effect of unobserved heterogeneity in the context of the linear transformation model for censored survival data in the clinical trials setting. The unobserved heterogeneity is represented by a frailty term, with unknown distribution, in the linear transformation model. The bias of the estimate under the assumption of no unobserved heterogeneity when it truly is present is obtained. We also derive the asymptotic relative efficiency of the estimate of treatment effect under the incorrect assumption of no unobserved heterogeneity. Additionally we investigate the loss of power for clinical trials that are designed assuming the model without frailty when, in fact, the model with frailty is true. Numerical studies under a proportional odds model show that the loss of efficiency and the loss of power can be substantial when the heterogeneity, as embodied by a frailty, is ignored.

Adaptive signature design: an adaptive clinical trial design for generating and prospectively testing a gene expression signature for sensitive patients

PURPOSE

A new generation of molecularly targeted agents is entering the definitive stage of clinical evaluation. Many of these drugs benefit only a subset of treated patients and may be overlooked by the traditional, broad-eligibility approach to randomized clinical trials. Thus, there is a need for development of novel statistical methodology for rapid evaluation of these agents.

EXPERIMENTAL DESIGN

We propose a new adaptive design for randomized clinical trials of targeted agents in settings where an assay or signature that identifies sensitive patients is not available at the outset of the study. The design combines prospective development of a gene expression-based classifier to select sensitive patients with a properly powered test for overall effect.

RESULTS

Performance of the adaptive design, relative to the more traditional design, is evaluated in a simulation study. It is shown that when the proportion of patients sensitive to the new drug is low, the adaptive design substantially reduces the chance of false rejection of effective new treatments. When the new treatment is broadly effective, the adaptive design has power to detect the overall effect similar to the traditional design. Formulas are provided to determine the situations in which the new design is advantageous.

CONCLUSION

Development of a gene expression-based classifier to identify the subset of sensitive patients can be prospectively incorporated into a randomized phase III design without compromising the ability to detect an overall effect.

Angiogenic inhibitors: a new therapeutic strategy in oncology

Angiogenesis is a multistep, complex and tightly regulated process that is necessary for tumor growth and metastasis. Based on data of preclinical models, several antiangiogenic compounds has been shown to modify activated tumor endothelium, which suggests that these compounds can improve cytotoxic drug delivery. Such agents have entered clinical trials as single agents or in combination with cytotoxic drugs, and have shown promising antitumor activity. The pharmacodynamic and pharmacokinetic characteristics of antiangiogenic drugs are reviewed here. Most of the early clinical testing of these agents was conducted in patients with advanced disease resistant to standard therapies. Phase III trials compared the efficacy of standard chemotherapy alone with standard chemotherapy in combination with an experimental angiogenesis inhibitor. Although some of these studies were negative or controversial, recent studies validated in large clinical trials with an anti-vascular endothelial growth factor antibody demonstrated significant clinical benefit and renewed enthusiasm for this therapeutic strategy. This review describes the clinical studies of antiangiogenic agents and highlights the challenges related to choosing appropriate strategies for the selection of patients, study design and choice of appropriate endpoints for the studies' development.

Erlotinib: small-molecule targeted therapy in the treatment of non-small-cell lung cancer

BACKGROUND

Erlotinib is an oral tyrosine kinase inhibitor, targeting the human epidermal receptor type 1/ epidermal growth factor receptor, recently approved by the US Food and Drug Administration (FDA) for the treatment of patients with locally advanced or metastatic non-small-cell lung cancer (NSCLC) after the failure of more than 1 or 2 previous chemotherapeutic regimens.

OBJECTIVE

The purpose of this article is to summarize the development, pharmacology, pharmacokinetics, efficacy, and adverse effects of erlotinib.

METHODS

A literature search was conducted with the MEDLINE and EMBASE (1999-2005) databases using the search terms non-small-cell lung cancer, erlotinib, and epidermal growth factor receptor inhibitor. Abstracts from the American Society of Clinical Oncology and documents submitted to the FDA also were reviewed.

RESULTS

BR.21, a randomized, placebo-controlled, multinational Phase III trial demonstrated clinically and statistically improved overall survival in patients with advanced or metastatic NSCLC treated with erlotinib versus placebo as second-line therapy. The erlotinib group had a median survival of 6.7 months versus a median survival of 4.7 months in the placebo group (P < 0.001). The toxicity profile of erlotinib was moderately benign, with the most commonly documented adverse events requiring dose reductions including skin rash (12%) and diarrhea (5%). Interstitial lung disease and relative fatalities were reported infrequently (0.8%) in patients receiving erlotinib. Two randomized, placebo-controlled, multicenter Phase III trials conducted in patients with locally advanced and metastatic NSCLC showed no clinical benefit with first-line administration of erlotinib plus concurrent platinum-based chemotherapy.

CONCLUSIONS

For patients with NSCLC in whom more than 1 or 2 previous chemotherapeutic regimens have failed, erlotinib is an effective therapy with significant overall survival benefits. The use of erlotinib as first-line therapy in combination with platinum-based chemotherapeutic regimens, however, has failed to demonstrate efficacy in the treatment of NSCLC.

Program for the Assessment of Clinical Cancer Tests (PACCT): assisting the development of tailored cancer therapy

Fulfillment of the promise of the genomic revolution for personalizing cancer therapy will depend on the ability to identify specific alterations in tumor cells that are critical to their growth, and the development of drugs that can target these alterations and inhibit their growth. In this report, examples of where this has been successful are discussed, and the challenges faced in other cases are described. The identification of the patients most likely to benefit from targeted agents requires significant investment in the development and validation of predictive assays. The Program for the Assessment of Clinical Cancer Tests (PACCT) has proposed an approach that should speed the development of the diagnostic tools required and their acceptance into clinical practice. This approach is dependent on determining the most pressing clinical questions confronting clinicians today and the availability of adequate specimens to validate the assays.

Ten years of marketing approvals of anticancer drugs in Europe: regulatory policy and guidance documents need to find a balance between different pressures

Despite important progress in understanding the molecular factors underlying the development of cancer and the improvement in response rates with new drugs, long-term survival is still disappointing for most common solid tumours. This might be because very little of the modest gain for patients is the result of the new compounds discovered and marketed recently. An assessment of the regulatory agencies' performance may suggest improvements. The present analysis summarizes and evaluates the type of studies and end points used by the EMEA to approve new anticancer drugs, and discusses the application of current regulations. This report is based on the information available on the EMEA web site. We identified current regulatory requirements for anticancer drugs promulgated by the agency and retrieved them in the relevant directory; information about empirical evidence supporting the approval of drugs for solid cancers through the centralised procedure were retrieved from the European Public Assessment Report (EPAR). We surveyed documents for drug applications and later extensions from January 1995, when EMEA was set up, to December 2004. We identified 14 anticancer drugs for 27 different indications (14 new applications and 13 extensions). Overall, 48 clinical studies were used as the basis for approval; randomised comparative (clinical) trial (RCT) and Response Rate were the study design and end points most frequently adopted (respectively, 25 out of 48 and 30 out of 48). In 13 cases, the EPAR explicitly reported differences between arms in terms of survival: the range was 0–3.7 months, and the mean and median differences were 1.5 and 1.2 months. The majority of studies (13 out of 27, 48%) involved the evaluation of complete and/or partial tumour responses, with regard to the end points supporting the 27 indications. Despite the recommendations of the current EMEA guidance documents, new anticancer agents are still often approved on the basis of small single arm trials that do not allow any assessment of an ‘acceptable and extensively documented toxicity profile’ and of end points such as response rate, time to progression or progression-free survival which at best can be considered indicators of anticancer activity and are not ‘justified surrogate markers for clinical benefit’. Anticipating an earlier than ideal point along the drug approval path and the use of not fully validated surrogate end points in nonrandomised trials looks like a dangerous shortcut that might jeopardise consumers' health, leading to unsafe and ineffective drugs being marketed and prescribed. The present Note for Guidance for new anticancer agents needs revising. Drugs must be rapidly released for patients who need them but not be at the expense of adequate knowledge about the real benefit of the drugs.

Gefitinib (ZD1839, Iressa) in non-small-cell lung cancer: a review of clinical trials from a daily practice perspective

Gefitinib (ZD1839) is the most widely studied targeting agent in the area of non-small-cell lung cancer (NSCLC). Gefitinib is an orally active epidermal growth factor receptor (EGFR) tyrosine kinase (TK) inhibitor. In order to assess the role of gefitinib in the management of NSCLC patients, we systematically reviewed published clinical trials from a daily practice perspective. A systematic research was made in the international medical literature. Gefitinib demonstrated a good tolerance and an encouraging efficacy in pretreated NSCLC patients in preclinical studies. These results were then confirmed in two phase II trials (IDEAL 1 and 2) involving more than 400 patients mostly pretreated with a platinum-containing regimen and docetaxel. All these results were reinforced by those of retrospective studies on patients enrolled in a compassionate use programme. Thus, two phase III trials in chemo-naive patients were initiated (INTACT 1 and 2). Unfortunately, the use of gefitinib with standard combination chemotherapy provided no survival benefit nor response rate or progression-free survival improvement over placebo. Furthermore, we also reviewed the results of studies interested in the characterization of predictive clinical or biological markers for response to gefitinib and discussed the results obtained with other EGFR inhibitors. The efficacy of gefitinib in the first-line setting of each stage of NSCLC has to be further studied through clinical trials. Furthermore, translational studies characterizing the molecular features involved in the response to anti-EGFR-targeted therapies are needed.

Evaluation of Randomized Discontinuation Design

Purpose

Single-arm phase II trials may not be appropriate for testing cytostatic agents. We evaluate two kinds of randomized designs for the early development of target-based cytostatic agents.

Methods

We compared power of the randomized discontinuation and upfront randomization designs under two models for the treatment effect of targeted cytostatic agents.

Results

The randomized discontinuation design is not as efficient as upfront randomization if treatment has a fixed effect on tumor growth rate or if treatment benefit is restricted to slower-growing tumors. On the other hand, the randomized discontinuation design can be advantageous under a model where only a subset of patients, those expressing the molecular target, is sensitive to the agent. To achieve efficiency, the design parameters must be carefully structured to provide adequate enrichment of the randomly assigned patients.

Conclusion

With careful planning, the randomized discontinuation designs can be useful in some settings in the early development of targeted agents where a reliable assay to select patients expressing the target is not available.

TRIBUTE: a phase III trial of erlotinib hydrochloride (OSI-774) combined with carboplatin and paclitaxel chemotherapy in advanced non-small-cell lung cancer

PURPOSE

Erlotinib is a potent reversible HER1/epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor with single-agent activity in patients with non-small-cell lung cancer (NSCLC). Erlotinib was combined with chemotherapy to determine if it could improve the outcome of patients with NSCLC.

PATIENTS AND METHODS

TRIBUTE randomly assigned patients with good performance status and previously untreated advanced (stage IIIB/IV) NSCLC to erlotinib 150 mg/d or placebo combined with up to six cycles of carboplatin and paclitaxel, followed by maintenance monotherapy with erlotinib. Random assignment was stratified by stage, weight loss in the previous 6 months, measurable disease, and treatment center. The primary end point was overall survival (OS). Secondary end points included time to progression (TTP), objective response (OR), and duration of response.

RESULTS

There were 1,059 assessable patients (526 erlotinib; 533 placebo). Median survival for patients treated with erlotinib was 10.6 v 10.5 months for placebo (hazard ratio, 0.99; 95% CI, 0.86 to 1.16; P = .95). There was no difference in OR or median TTP. Patients who reported never smoking (72 erlotinib; 44 placebo) experienced improved OS in the erlotinib arm (22.5 v 10.1 months for placebo), though no other prespecified factors showed an advantage in OS with erlotinib. Erlotinib and placebo arms were equivalent in adverse events (except rash and diarrhea).

CONCLUSION

Erlotinib with concurrent carboplatin and paclitaxel did not confer a survival advantage over carboplatin and paclitaxel alone in patients with previously untreated advanced NSCLC. Never smokers treated with erlotinib and chemotherapy seemed to experience an improvement in survival and will undergo further investigation in future randomized trials.

The treatment of malignant gliomas

The optimal management of patients with malignant gliomas begins with the accurate determination of the pathologic diagnosis based on adequate sampling of the tumor. Clear differences in prognosis and therapeutic options have been established for the various tumor grades and cellular classification. Current recommendations, on the basis of the results of a recent phase III randomized trial, are that patients with glioblastoma should have maximal surgical resection followed by concurrent radiation and chemotherapy with temozolomide. It is further recommended that patients then be treated with 6 to 12 months of adjuvant temozolomide. However, despite the shown improvement in survival with this chemoradiation regimen, the impact on outcome is modest. It is increasingly evident that a greater understanding of the molecular mechanisms of gliomagenesis is needed to improve treatments for these patients. Recent and ongoing investigations strongly indicate that specific molecular markers tremendously impact prognosis and often can predict response to treatment. For example, allelic loss of the 1p and 19q chromosome arms predicts a dramatic improvement in response to treatment and survival for tumors histologically classified as anaplastic oligodendroglioma. Future advances for treating primary brain tumors likely will be directly related to our ability to molecularly subcategorize tumors and customize therapy based on the molecular profile within each histologic type and grade of tumor. This is evident in preliminary data indicating that inactivation of the methyl guanine methyltransferase gene by hypermethylation of the promoter region specifically predicts a better tumor response rate to chemotherapies that alkylate DNA as their mechanism of action. Similarly, elucidation of overly active signal transduction pathways within tumor cells may provide an opportunity to select the optimal therapeutic regimen composed of modulators of these pathways, analogous to restricting the use of trastuzumab to breast cancers expressing the Her-2 receptor. Advances in treating primary malignant brain tumors will likely depend on collaborative clinical trials that are designed to select patients on the basis of histologic and molecular characteristics and to determine the optimal biologic dose of the best agent that can treat each specific tumor type.

Clinical experience with monoclonal antibodies to epidermal growth factor receptor

Recent knowledge about the intermediate steps and final consequences of ligand-dependent epidermal growth factor receptor (EGFR) activation has clearly supported the notion that EGFR plays a fundamental role in regulating the proliferation and survival of malignant neoplasms. Among the rationally designed target-based therapeutics that are being assessed, those targeting EGFR appear to be some of the most clinically relevant. The strategy of using monoclonal antibodies (mAbs) to block ligand binding to the extracellular domain of the EGFR has led to the development of therapeutics that robustly arrest malignant cell proliferation and, in some cases, induce profound tumor regression. The chimeric mAb against EGFR, cetuximab, has already been approved by regulatory agencies worldwide to treat patients with advanced colorectal cancer. Other mAbs against EGFR, particularly panitumumab (ABX-EGF), h-R3, and EMD72000, are in advanced stages of clinical development.

Combination of antiangiogenic therapy with other anticancer therapies: results, challenges, and open questions

Angiogenesis is necessary for tumor growth. Drug discovery efforts have identified several potential therapeutic targets on endothelial cells and selective inhibitors capable of slowing tumor growth or producing tumor regression by blocking angiogenesis in in vivo tumor models. Certain antiangiogenic therapeutics increase the activity of cytotoxic anticancer treatments in preclinical models. More than 75 antiangiogenic compounds have entered clinical trials. Most of the early clinical testing was conducted in patients with advanced disease resistant to standard therapies. Several phase III trials have been undertaken to compare the efficacy of standard chemotherapy versus the same in combination with an experimental angiogenesis inhibitor. Preliminary results of the clinical studies suggest that single-agent antiangiogenic therapy is poorly active in advanced tumors. Although some of the results of combination trials are controversial, recent positive outcomes with an antivascular endothelial growth factor antibody combined with chemotherapy as front-line therapy of metastatic colorectal cancer have renewed enthusiasm for this therapeutic strategy. This article presents an overview of experimental and clinical studies of combined therapy with antiangiogenic agents and highlights the challenges related to the appropriate strategies for selection of the patients, study design, and choice of proper end points for preclinical and clinical studies using these agents.

Breast cancer gene expression profiling: clinical trial and practice implications

The advent of high-throughput array-based technology and the sequencing of the human genome has provided the opportunity to begin comprehensive molecular and genetic profiling of cancers. Such efforts have, in a limited time, given us new insights into breast cancer biology and confirmed that the disease is considerably more heterogeneous than can be predicted by traditional histopathological methods. The estrogen receptor has been found to be the most dominant factor influencing the molecular composition of breast cancer and, in addition, novel subgroups of breast cancer with differing clinical outcomes have been observed. These may have substantial management implications for breast cancer patients and facilitate individualized rather than empirical oncological prescription. Furthermore, new methods of prognostic classification have been developed using array technology. The challenges ahead lie in refining the use of the technology, proper validation of discoveries, and the large-scale collaborative efforts necessary for the incorporation of genomic knowledge into the design and conduct of clinical trials. This will lead, ultimately, to the application of user-friendly tools derived from this technology to everyday patient care.

On the efficiency of targeted clinical trials

The development of genomics-based technologies is demonstrating that many common diseases are heterogeneous collections of molecularly distinct entities. Molecularly targeted therapeutics is often effective only for some subsets patients with a conventionally defined disease. We consider the problem of design of phase III randomized clinical trials for the evaluation of a molecularly targeted treatment when there is an assay predictive of which patients will be more responsive to the experimental treatment than to the control regimen. We compare the conventional randomized clinical trial design to a design based on randomizing only patients predicted to preferentially benefit from the new treatment. Trial designs are compared based on the required number of randomized patients and the expected number of patients screened for randomization eligibility. Relative efficiency depends upon the distribution of treatment effect across patient subsets, prevalence of the subset of patients who respond preferentially to the experimental treatment, and assay performance.

Trying to compose the puzzle with all the pieces: Epidermal growth factor receptor tyrosine kinase inhibitors in non-small cell lung cancer

Small molecule epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have shown promising activity in patients with non-small cell lung cancer (NSCLC). Gefitinib has been the first of these drugs to be licensed for third-line treatment of advanced NSCLC patients. More recently, erlotinib has been shown to be more effective than placebo in increasing overall survival (OAS) and has been approved for NSCLC patients after failure of chemotherapy. However, a large body of clinical and experimental evidence suggests that the benefit from these drugs is limited to a subgroup of patients. The availability of clinical or molecular criteria for predicting sensitivity to EGFR-TKIs is the most relevant issue for their correct use and for planning future research. Determination of EGFR expression is not sufficient to predict sensitivity to EGFR-TKIs. However, several clinical features (female gender, adenocarcinoma/bronchioloalveolar histotype, never-smoking status, Oriental Asian origin) are associated with major clinical responses. The identification of somatic mutations in the tyrosine kinase domain of the EGFR gene represents the most important molecular marker of sensitivity to EGFR-TKIs. These "activating" mutations can be found in a high proportion of gefitinib- or erlotinib-responding patients. However, clinical effectiveness might not be limited to patients carrying EGFR mutations, in which the objective response is probably the detectable effect of apoptosis induction in cancer cells. In fact, clinical efficacy with gefitinib or erlotinib is also observed in another subgroup of patients, in which a tumor growth delay, determined by a block in cancer cell proliferation, could induce a prolonged and clinically relevant disease stabilization.

The role of imaging in the clinical development of antiangiogenic agents

Early clinical development of novel antiangiogenesis agents is hampered by the fact that classic response end points are unlikely to be relevant and there is a lack of validated surrogate markers of efficacy. Toxicity-based decisions for dose setting and tumor size measurements by standard imaging probably are not be applicable. Because these agents modify a multitude of biologic processes that may cause early measurable effects, there is great interest in developing imaging tests that are sensitive to changes in tissue function. This article discusses the development of such "functional" clinical imaging and attempts to address the questions that are being asked of imaging departments by oncologists and pharmaceutical companies.

Gene expression profiling of gliomas strongly predicts survival

In current clinical practice, histology-based grading of diffuse infiltrative gliomas is the best predictor of patient survival time. Yet histology provides little insight into the underlying biology of gliomas and is limited in its ability to identify and guide new molecularly targeted therapies. We have performed large-scale gene expression analysis using the Affymetrix HG U133 oligonucleotide arrays on 85 diffuse infiltrating gliomas of all histologic types to assess whether a gene expression-based, histology-independent classifier is predictive of survival and to determine whether gene expression signatures provide insight into the biology of gliomas. We found that gene expression-based grouping of tumors is a more powerful survival predictor than histologic grade or age. The poor prognosis samples could be grouped into three different poor prognosis groups, each with distinct molecular signatures. We further describe a list of 44 genes whose expression patterns reliably classify gliomas into previously unrecognized biological and prognostic groups: these genes are outstanding candidates for use in histology-independent classification of high-grade gliomas. The ability of the large scale and 44 gene set expression signatures to group tumors into strong survival groups was validated with an additional external and independent data set from another institution composed of 50 additional gliomas. This demonstrates that large-scale gene expression analysis and subset analysis of gliomas reveals unrecognized heterogeneity of tumors and is efficient at selecting prognosis-related gene expression differences which are able to be applied across institutions.

Challenges in breast cancer clinical trial design in the postgenomic era

PURPOSE OF REVIEW

Clinical trials in breast cancer (BC) have seldom taken into consideration molecular heterogeneity, because most have been performed in unselected populations. Hence, their results provide an estimated average benefit for the entire BC population, which may not always be translated to subsets of patients with certain characteristics, let alone to individual patients. Further understanding and acknowledgment of heterogeneity is vital for the development of individualized therapy in BC. New approaches are needed for trial design, patient selection, and choice of endpoints (including surrogate markers). The neoadjuvant setting presents a unique opportunity to test new concepts in a previously untreated patient population, because they may yield preliminary answers in a shorter time than that required in adjuvant trials.

RECENT FINDINGS

The importance of patient selection in the development of targeted agents is exemplified by trastuzumab in BC and of gefitinib in lung cancer. Ongoing innovative trials that investigate biologic hypotheses include the BIG-EORTC p53, TOP and FRAGRANCE trials (which study predictive factors for response), and the NNBC-3 and MINDACT trials (which study prognostic factors).

SUMMARY

There is an urgent need to break from traditional clinical development and to incorporate new molecular knowledge and translational research in the design of clinical trials. The success of new approaches in BC research critically depends on well-conducted translational research linked to prospective clinical trials, and international collaboration, bringing together human and technological resources.

Molecular pathogenesis of oligodendroglial tumors

Based on their histopathological appearances, most diffusely infiltrative gliomas can be classified either as astrocytic tumors (As), pure oligodendroglial tumors (Os) or mixed oligoastrocytic tumors (OAs). The latter two may be grouped together as oligodendroglial tumors (OTs). The distinction between As and OTs is important because of the more favorable clinical behavior of OTs. Unfortunately, the histopathological delineation of OAs, Os and As can be difficult because of vague and subjective histopathological criteria. Over the last decade, the knowledge on the molecular genetic background of OTs has drastically increased. This review provides an overview of molecular genetic aberrations in OTs and discusses the pathobiological and clinical significance of these aberrations. In contrast to As, OTs frequently show frequent loss of heterozygosity on chromosome arms 1p and 19q. Since these aberrations are significantly correlated with clinically relevant parameters, such as prognosis and chemosensitivity, and given the difficulties in histopathological typing and grading of glial tumors, genetic testing should be included in routine glioma diagnostics. It is to be expected that the identification of the relevant tumor suppressor genes located on 1p and 19q will lead to more refined genetic tests for OTs. Furthermore, as microarray technology is rapidly increasing, it is likely that clinically relevant markers for OTs will be identified on other chromosomes and need to be included into routine glioma diagnostics as well.

Development and use of biomarkers in oncology drug development

Successful development and use of biomarkers will improve the productivity of oncology drug development. Recognition of the importance of biomarkers for speeding drug development is reflected in the precise definitions and concepts proposed by an NIH Working Group to standardize terminology and promote a more coherent and systematic approach to the development and use of biomarkers. Potential clinical biomarkers of drug efficacy are often identified through pre-clinical studies or basic research. Identification of potential biomarkers for use in oncology is moving rapidly forward through continuing advances in clinical imaging technologies, especially molecular and functional imaging. Other rapid advances are a product of the growing availability of new scientific reagents for established technologies and of high-throughput genomic and proteomic technologies that can generate hundreds of potential biomarkers for further evaluation. In certain cases, conventional clinical diagnostic techniques or assays can be adapted for use in pre-clinical models to evaluate their ability to serve as biomarkers for predicting clinical responses to new drug candidates. Evaluation (pre-clinical and clinical) of a potential biomarker is often the longest stage of biomarker development, and standards for evaluation or validation depend on the intended use and stage of clinical development. Biomarkers verified for use in preclinical studies can be used to help select appropriate animal models and lead compounds. Biomarkers verified for use in clinical trials can confirm a drug's pharmacological or biological mechanism of action, guide protocol design, aid patient and dose selection, and help to minimize safety risks. Oncology drug development can be optimized by using a tiered set of clinical biomarkers that predict compound efficacy and safety with increasing confidence at each rise in tier thereby aiding corporate decision-making about advancing compounds. In oncology, a special class of extensively evaluated biomarkers of efficacy (surrogate endpoints) that generally correlate with desired clinical outcomes can be used as a basis for corporate decisions as well as for gaining accelerated provisional regulatory approval of a drug.

DNA-microarray analysis of brain cancer: molecular classification for therapy

Primary brain tumours are among the most lethal of all cancers, largely as a result of their lack of responsiveness to current therapy. Numerous new therapies hold great promise for the treatment of patients with brain cancer, but the main challenge is to determine which treatment is most likely to benefit an individual patient. DNA-microarray-based technologies, which allow simultaneous analysis of expression of thousands of genes, have already begun to uncover previously unrecognized patient subsets that differ in their survival. Here, we review the progress made so far in using DNA microarrays to optimize brain cancer therapy.

HER1/EGFR targeting: refining the strategy

Human epidermal growth factor receptor (EGFR), HER, targeting has formed the basis of extensive and growing drug development programs in various companies. However, receptor biology is often poorly explained and confusing. The HER family of four naturally occurring receptors and one tumor-specific mutant can activate signaling via a complex and sophisticated range of mechanisms, which we are only beginning to understand. HER1/EGFR downstream signaling can lead to tumor growth and development via a host of processes, including enhanced cellular proliferation, survival, and metastasis. A range of potential therapeutic targets exists within the HER signaling system, both inside and outside the cell. Monoclonal antibodies and tyrosine kinase inhibitors, acting extracellularly and intracellularly, respectively, comprise two classes of agents most advanced in clinical development or already available for use. Despite promising single-agent activity in chemotherapy-resistant patients with non-small cell lung cancer (NSCLC), disappointing results from two phase III trials of the tyrosine kinase inhibitor gefitinib in NSCLC have been of concern to some. However, many factors may have contributed to this outcome, and it is not necessarily predictive of the future usefulness of these agents. Patient characteristics, lack of patient selection, dosing schedule, and trial design may all have played roles. It is important to remember that intracellular targeting of HER is a relatively novel approach, and our knowledge of how best to optimize such treatment is still unfolding. More clinical experience is needed.

The role of targeted therapy in non-small cell lung cancer

The therapy of non-small cell lung cancer (NSCLC) has reached a plateau in improving patient survival, with overall disappointing results. Thus, clinical research for new treatment strategies is warranted. Advances in the singling out molecular targets for NSCLC treatment has granted the development of several new biological agents. In the present paper we describe the main clinical data currently available on targeted agents in the treatment of NSCLC, focusing on epidermal growth factor receptor family inhibitors, angiogenesis inhibitors, signal transduction inhibitors, eicosanoid pathway inhibitors, vaccines and gene therapy. Several targeted agents have been introduced into clinical trials in NSCLC, mainly in advanced disease, with the first phase III study results being recently made available. To date, few of these new agents can offer hope of a substantial impact on the natural history of NSCLC, and negative results are more commonly reported than positive ones. Nevertheless, clinically-meaningful advances have already been achieved in chemotherapy refractory advanced NSCLC patients, with gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor, representing a further chance of tumor control and symptom palliation. Moreover, important lessons can be learned from this first generation of clinical trials.

Chemotherapy of anaplastic oligodendroglial tumours

Anaplastic oligodendroglial tumours (oligodendrogliomas and oligoastro-cytomas) have a definite better prognosis than diffuse astrocytic gliomas (glioblastomas and anaplastic astrocytomas). Surgery relieves neurological symptoms and provides tissue for classification, grading and molecular characterisation of the tumour. Historically, radiation therapy has been the sole postoperative treatment for patients with anaplastic oligodendroglial tumours, but this policy has been challenged in the last few years by the discovery that these tumours are chemosensitive. Procarbazine, lomustine and vincristine (PCV) and temozolomide are the most active drugs, but it is still unclear which is the best first-line regimen. The most appropriate timing for chemotherapy (neoadjuvant, adjuvant, at recurrence) is unknown and is currently being explored in prospective studies. The goals of neoadjuvant chemotherapy (PCV, temozolomide, high-dose alkylating agents with stem cell rescue) are to defer radiotherapy or to reduce the radiation fields for a conformal treatment in responding patients. Molecular genetic analysis is increasingly employed for both diagnostic and prognostic purposes. Loss of heterozygosity on 1p and 19q is the key alteration for predicting the prognosis and the response to chemotherapy.