Phase I study of G3139, a bcl-2 antisense oligonucleotide, combined with carboplatin and etoposide in patients with small-cell lung cancer

Unlocking the potential of RNA-based therapeutics in the lung: current status and future directions

Awareness of RNA-based therapies has increased after the widespread adoption of mRNA vaccines against SARS-CoV-2 during the COVID-19 pandemic. These mRNA vaccines had a significant impact on reducing lung disease and mortality. They highlighted the potential for rapid development of RNA-based therapies and advances in nanoparticle delivery systems. Along with the rapid advancement in RNA biology, including the description of noncoding RNAs as major products of the genome, this success presents an opportunity to highlight the potential of RNA as a therapeutic modality. Here, we review the expanding compendium of RNA-based therapies, their mechanisms of action and examples of application in the lung. The airways provide a convenient conduit for drug delivery to the lungs with decreased systemic exposure. This review will also describe other delivery methods, including local delivery to the pleura and delivery vehicles that can target the lung after systemic administration, each providing access options that are advantageous for a specific application. We present clinical trials of RNA-based therapy in lung disease and potential areas for future directions. This review aims to provide an overview that will bring together researchers and clinicians to advance this burgeoning field.

Antisense Oligonucleotide-Mediated Splice Switching: Potential Therapeutic Approach for Cancer Mitigation

Splicing is an essential process wherein precursor messenger RNA (pre-mRNA) is reshaped into mature mRNA. In alternative splicing, exons of any pre-mRNA get rearranged to form mRNA variants and subsequently protein isoforms, which are distinct both by structure and function. On the other hand, aberrant splicing is the cause of many disorders, including cancer. In the past few decades, developments in the understanding of the underlying biological basis for cancer progression and therapeutic resistance have identified many oncogenes as well as carcinogenic splice variants of essential genes. These transcripts are involved in various cellular processes, such as apoptosis, cell signaling and proliferation. Strategies to inhibit these carcinogenic isoforms at the mRNA level are promising. Antisense oligonucleotides (AOs) have been developed to inhibit the production of alternatively spliced carcinogenic isoforms through splice modulation or mRNA degradation. AOs can also be used to induce splice switching, where the expression of an oncogenic protein can be inhibited by the induction of a premature stop codon. In general, AOs are modified chemically to increase their stability and binding affinity. One of the major concerns with AOs is efficient delivery. Strategies for the delivery of AOs are constantly being evolved to facilitate the entry of AOs into cells. In this review, the different chemical modifications employed and delivery strategies applied are discussed. In addition to that various AOs in clinical trials and their efficacy are discussed herein with a focus on six distinct studies that use AO-mediated exon skipping as a therapeutic strategy to combat cancer.

RNA-based therapies: A cog in the wheel of lung cancer defense

Lung cancer (LC) is a heterogeneous disease consisting mainly of two subtypes, non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), and remains the leading cause of death worldwide. Despite recent advances in therapies, the overall 5-year survival rate of LC remains less than 20%. The efficacy of current therapeutic approaches is compromised by inherent or acquired drug-resistance and severe off-target effects. Therefore, the identification and development of innovative and effective therapeutic approaches are critically desired for LC. The development of RNA-mediated gene inhibition technologies was a turning point in the field of RNA biology. The critical regulatory role of different RNAs in multiple cancer pathways makes them a rich source of targets and innovative tools for developing anticancer therapies. The identification of antisense sequences, short interfering RNAs (siRNAs), microRNAs (miRNAs or miRs), anti-miRs, and mRNA-based platforms holds great promise in preclinical and early clinical evaluation against LC. In the last decade, RNA-based therapies have substantially expanded and tested in clinical trials for multiple malignancies, including LC. This article describes the current understanding of various aspects of RNA-based therapeutics, including modern platforms, modifications, and combinations with chemo-/immunotherapies that have translational potential for LC therapies.

Genetic Modification of the Lung Directed Toward Treatment of Human Disease

Genetic modification therapy is a promising therapeutic strategy for many diseases of the lung intractable to other treatments. Lung gene therapy has been the subject of numerous preclinical animal experiments and human clinical trials, for targets including genetic diseases such as cystic fibrosis and α1-antitrypsin deficiency, complex disorders such as asthma, allergy, and lung cancer, infections such as respiratory syncytial virus (RSV) and Pseudomonas, as well as pulmonary arterial hypertension, transplant rejection, and lung injury. A variety of viral and non-viral vectors have been employed to overcome the many physical barriers to gene transfer imposed by lung anatomy and natural defenses. Beyond the treatment of lung diseases, the lung has the potential to be used as a metabolic factory for generating proteins for delivery to the circulation for treatment of systemic diseases. Although much has been learned through a myriad of experiments about the development of genetic modification of the lung, more work is still needed to improve the delivery vehicles and to overcome challenges such as entry barriers, persistent expression, specific cell targeting, and circumventing host anti-vector responses.

Amplification and Quantification of an Antisense Oligonucleotide from Target microRNA Using Programmable DNA and a Biological Nanopore

This paper describes a strategy for autonomous diagnoses of cancers using microRNA (miRNA) and therapy for tumor cells by DNA computing techniques and nanopore measurement. Theranostics, which involves the combination of diagnosis and therapy, has emerged as an approach for personalized medicine or point-of-care cancer diagnostics. DNA computing will become a potent tool for theranostics because it functions completely autonomously without the need for external regulations. However, conventional theranostics using DNA computing involves a one-to-one reaction in which a single input molecule generates a single output molecule; the concentration of the antisense drug is insufficient for the therapy in this type of reaction. Herein we developed an amplification system involving an isothermal reaction in which a large amount of the antisense DNA drug was autonomously generated after detecting miRNA from small cell lung cancer. In addition, we successfully quantified the amount of the generated drug molecule by nanopore measurement with high accuracy, which was more accurate than conventional gel electrophoresis. This autonomous amplification strategy is a potent candidate for a broad range of theranostics using DNA computing.

Targeted drugs in small-cell lung cancer

In contrast to non-small-cell lung cancer (NSCLC), few advances have been made in systemic treatment of small-cell lung cancer (SCLC) in recent years. Most patients are diagnosed with extensive stage disease and are commonly treated with platinum-based chemotherapy which, although attaining high initial objective responses, has a limited impact on survival. Due to the dismal prognosis of SCLC, novel and more effective treatment strategies are urgently needed. A deeper characterization of the genomic landscape of SCLC has led to the development of rational and promising targeted agents. However, despite a large number of clinical trials, results have been disappointing and there are still no approved targeted drugs for SCLC. Recent comprehensive genomic studies suggest SCLC is a heterogeneous disease, characterized by genomic alterations targeting a broad variety of genes, including those involved in transcription regulation and chromatin modification which seem to be a hallmark of this specific lung cancer subtype. Current research efforts are focusing on further understanding of the cellular and molecular abnormalities underlying SCLC development, progression and resistance to chemotherapy. Unraveling the genomic complexity of SCLC could be the key to optimize existing treatments, including chemotherapy and radiotherapy, and for identifying those patients most likely to benefit from selected targeted therapeutic approaches.

Potential of apoptotic pathway-targeted cancer therapeutic research: Where do we stand?

Underneath the intricacy of every cancer lies mysterious events that impel the tumour cell and its posterity into abnormal growth and tissue invasion. Oncogenic mutations disturb the regulatory circuits responsible for the governance of versatile cellular functions, permitting tumour cells to endure deregulated proliferation, resist to proapoptotic insults, invade and erode normal tissues and above all escape apoptosis. This disruption of apoptosis has been highly implicated in various malignancies and has been exploited as an anticancer strategy. Owing to the fact that apoptosis causes minimal inflammation and damage to the tissue, apoptotic cell death-based therapy has been the centre of attraction for the development of anticancer drugs. Increased understanding of the molecular pathways underlying apoptosis has enabled scientists to establish unique approaches targeting apoptosis pathways in cancer therapeutics. In this review, we reconnoitre the two major pathways (intrinsic and extrinsic) targeted cancer therapeutics, steering toward chief modulators of these pathways, such as B-cell lymphoma 2 protein family members (pro- and antiapoptotic), inhibitor of apoptosis proteins, and the foremost thespian of extrinsic pathway regulator, tumour necrosis factor-related apoptosis-inducing agent. Together, we also will have a look from clinical perspective to address the agents (drugs) and therapeutic strategies adopted to target these specific proteins/pathways that have entered clinical trials.

Liposome-coated lipoplex-based carrier for antisense oligonucleotides

The chemical nature of genetic drugs (e.g. antisense oligonucleotides, siRNA, vectors) requires a suitable carrier system to protect them from enzymatic degradation without changing their properties and enable efficient delivery into target cells. Lipid vectors for nucleic acid delivery that have been widely investigated for years can be very effective. As the majority of attempts made in the field of cancer gene therapy have focused on solid tumors, while blood cancer cells have attracted less attention, the latter became the subject of our investigation. The lipid carrier proposed here is based on liposomes constructed by others but the lipid composition is original. A liposome-coated lipoplex (L-cL) consists of a core arising from complexation of positively charged lipid and negatively charged oligodeoxynucleotide (ODN) or plasmid DNA coated by a neutral or anionic lipid bilayer. Moreover, our lipid vector demonstrates size stability and is able to retain a high content of enclosed plasmid DNA or antisense oligodeoxynucleotides (asODNs). Observed transfection efficacies of the tested preparation using a plasmid coding for fluorescent protein were up to 60-85% of examined leukemia cells (Jurkat T and HL-60 lines) in the absence or the presence of serum. When BCL‑2 asODN was encapsulated in the L-cL, specific silencing of this gene product at both the mRNA and protein level and also a markedly decreased cell survival rate were observed in vitro. Moreover, biodistribution analysis in mice indicates prolonged circulation characteristic for PEG-modified liposomal carriers. Experiments on tumor-engrafted animals indicate substantial inhibition of tumor growth.

Targeted therapies for small cell lung cancer: Where do we stand?

Small cell lung cancer (SCLC) accounts for 15% of lung cancer cases and is associated with a dismal prognosis. Standard therapeutic regimens have been improved over the past decades, but without a major impact on patient survival. The development of targeted therapies based on a better understanding of the molecular basis of the disease is urgently needed. At the genetic level, SCLC appears very heterogenous, although somatic mutations targeting classical oncogenes and tumor suppressors have been reported. SCLC also possesses somatic mutations in many other cancer genes, including transcription factors, enzymes involved in chromatin modification, receptor tyrosine kinases and their downstream signaling components. Several avenues have been explored to develop targeted therapies for SCLC. So far, however, there has been limited success with these targeted approaches in clinical trials. Further progress in the optimization of targeted therapies for SCLC will require the development of more personalized approaches for the patients.

Update of research on drug resistance in small cell lung cancer chemotherapy

Small cell lung cancer (SCLC) is characterized by a short cell doubling time, rapid progression and early occurrence of blood-borne and lymph metastasis. The malignancy is the highest of all lung cancer types. Although SCLC has a relatively good initial response to chemotherapy as well as radiotherapy, relapse or disease progression may occur quickly after the initial treatment. Drug resistance, especially multi-drug resistance, is the most important cause of failure of SCLC chemotherapy. This article provides a brief update of research on mechanisms of drug resistance in SCLC and reversal strategies.

Erlotinib resistance in lung cancer: current progress and future perspectives

Lung cancer is the most common cancer in the world. Despite modern advancements in surgeries, chemotherapies, and radiotherapies over the past few years, lung cancer still remains a very difficult disease to treat. This has left the death rate from lung cancer victims largely unchanged throughout the past few decades. A key cause for the high mortality rate is the drug resistance that builds up for patients being currently treated with the chemotherapeutic agents. Although certain chemotherapeutic agents may initially effectively treat lung cancer patients, there is a high probability that there will be a reoccurrence of the cancer after the patient develops resistance to the drug. Erlotinib, the epidermal growth factor receptor (EGFR)-targeting tyrosine kinase inhibitor, has been approved for localized as well as metastatic non-small cell lung cancer where it seems to be more effective in patients with EGFR mutations. Resistance to erlotinib is a common observation in clinics and this review details our current knowledge on the subject. We discuss the causes of such resistance as well as innovative research to overcome it. Evidently, new chemotherapy strategies are desperately needed in order to better treat lung cancer patients. Current research is investigating alternative treatment plans to enhance the chemotherapy that is already offered. Better insight into the molecular mechanisms behind combination therapy pathways and even single molecular pathways may help improve the efficacy of the current treatment options.

Novel antineoplastics targeting genetic changes in colorectal cancer

Cytotoxic chemotherapy remains the mainstay of the medical -management of colorectal cancer (CRC). Research over the last two decades has led to a molecular understanding of the oncogenic mechanisms involved in CRC and has contributed to the rational development of antineoplastics that target these mechanisms. During carcinogenesis, genetic changes often occur in molecules that play key functional roles in cancer such as cell proliferation, angiogenesis, apoptosis, cell death and immune-mediated destruction of cancer cells. Here, we review novel antineoplastics that are approved or in development for CRC that target molecules associated with genetic aberrations in CRC. Some of these targeted antineoplastics have proven effective against other solid tumors and hold promise in treating CRC whereas others are now routinely used in combination with cytotoxic agents. This article reviews antineoplastics that target genetic changes in CRC, their antitumor mechanisms, and their stage of development.

Targeted therapies in small cell lung cancer

Lung cancer is the leading cause of cancer-related mortality. Small cell lung cancer (SCLC) accounted for 12.95% of all lung cancer histological types in 2002. Despite trends toward modest improvement in survival, the outcome remains extremely poor. Chemotherapy is the cornerstone of treatment in SCLC. More than two-thirds of patients who succumb to lung cancer in the United States are over 65 years old. Elderly patients tolerate chemotherapy poorly and need novel therapeutic agents. Targeted drugs have less toxicity than chemotherapy drugs, but no targeted agents have been approved for use in the treatment of SCLC patients to date. Certain new targeted agents, including gefitinib, bevacizumab and Bcl-2 inhibitors, offer a promise of improved outcomes, however negative results are more commonly reported than positive. This review focuses on targeted therapies in SCLC.

Reverse translation of phase I biomarker findings links the activity of angiotensin-(1-7) to repression of hypoxia inducible factor-1α in vascular sarcomas

Background

In a phase I study of angiotensin-(1–7) [Ang-(1–7)], clinical benefit was associated with reduction in plasma placental growth factor (PlGF) concentrations. The current study examines Ang-(1–7) induced changes in biomarkers according to cancer type and investigates mechanisms of action engaged in vitro.

Methods

Plasma biomarkers were measured prior to Ang-(1–7) administration as well as 1, 2, 3, 4, and 6 hours after treatment. Tests for interaction were performed to determine the impact of cancer type on angiogenic hormone levels. If a positive interaction was detected, treatment-induced biomarker changes for individual cancer types were assessed. To investigate mechanisms of action, in vitro growth assays were performed using a murine endothelioma cell line (EOMA). PCR arrays were performed to identify and statistically validate genes that were altered by Ang-(1–7) treatment in these cells.

Results

Tests for interaction controlled for dose cohort and clinical response indicated a significant impact of cancer type on post-treatment VEGF and PlGF levels. Following treatment, PlGF levels decreased over time in patients with sarcoma (P = .007). Treatment of EOMA cells with increasing doses of Ang-(1–7) led to significant growth suppression at doses as low as 100 nM. PCR arrays identified 18 genes that appeared to have altered expression after Ang-(1–7) treatment. Replicate analyses confirmed significant changes in 8 genes including reduction in PlGF (P = .04) and hypoxia inducible factor 1α (HIF-1α) expression (P < .001).

Conclusions

Ang-(1–7) has clinical and pre-clinical activity for vascular sarcomas that is linked to reduced HIF-1α and PlGF expression.

A novel classification of lung cancer into molecular subtypes

The remarkably heterogeneous nature of lung cancer has become more apparent over the last decade. In general, advanced lung cancer is an aggressive malignancy with a poor prognosis. The discovery of multiple molecular mechanisms underlying the development, progression, and prognosis of lung cancer, however, has created new opportunities for targeted therapy and improved outcome. In this paper, we define "molecular subtypes" of lung cancer based on specific actionable genetic aberrations. Each subtype is associated with molecular tests that define the subtype and drugs that may potentially treat it. We hope this paper will be a useful guide to clinicians and researchers alike by assisting in therapy decision making and acting as a platform for further study. In this new era of cancer treatment, the 'one-size-fits-all' paradigm is being forcibly pushed aside-allowing for more effective, personalized oncologic care to emerge.

Gene therapy for lung neoplasms

Both advanced-stage lung cancer and malignant pleural mesothelioma are associated with a poor prognosis. Advances in treatment regimens for both diseases have had only a modest effect on their progressive course. Gene therapy for thoracic malignancies represents a novel therapeutic approach and has been evaluated in several clinical trials. Strategies have included induction of apoptosis, tumor suppressor gene replacement, suicide gene expression, cytokine-based therapy, various vaccination approaches, and adoptive transfer of modified immune cells. This review considers the clinical results, limitations, and future directions of gene therapy trials for thoracic malignancies.

Current management of small cell lung cancer

Confined to one side of the chest, limited stage small cell lung cancer is treated with a combination of chemotherapy and radiotherapy, yet has a long-term survival rate of only 15%. Extensive stage disease has initial response rates to chemotherapy exceeding 70%. However, the disease almost invariably progresses and becomes fatal. Many recent clinical trials have failed to show superiority of newer chemotherapeutics or targeted therapies compared with the standard chemotherapy backbone of platinum plus etoposide. Numerous promising targeted therapies and other agents are still in development.

Update on new drugs in small cell lung cancer

INTRODUCTION

Small cell lung cancer (SCLC) will account for 25,000 to 32,000 new lung cancer cases in the USA in 2010. Current treatmenta pproaches include platinum-based chemotherapy and etoposide with or without radiation therapy depending on stage and performance status. Five-year survival is approximately 25% for patients with limited stage disease and 1 -- 2% for patients with extensive stage disease and has noti mproved in almost two decades.

AREAS COVERED

This article reviews the results of recent clinical trials that have evaluated targeted agents and novel cytotoxic agents alone or in combination with standard chemotherapy in the treatment of patients with SCLC.

EXPERT OPINION

The lack of a targeted approach to the treatment of patients with SCLC has led investigators to evaluate a multitude of agents with overwhelmingly negative results. A more systematic approach to clinical trials in patients is needed to improve outcomes for patients with this disease.

Optimization of circulating biomarkers of obatoclax-induced cell death in patients with small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive disease in which, after initial sensitivity to platinum/etoposide chemotherapy, patients frequently relapse with drug-resistant disease. Deregulation of the Bcl-2 pathway is implicated in the pathogenesis of SCLC, and early phase studies of Bcl-2 inhibitors have been initiated in SCLC. Obatoclax is a small-molecule drug designed to target the antiapoptotic Bcl-2 family members to a proapoptotic effect. Preclinical studies were conducted to clarify the kinetics of obatoclax-induced apoptosis in a panel of SCLC cell lines to assist with the interpretation of biomarker data generated during early phase clinical trials. In vitro, obatoclax was synergistic with cisplatin and etoposide, and "priming" cells with obatoclax before the cytotoxics maximized tumor cell death. Peak levels of apoptosis, reflected by cleaved cytokeratin 18 (CK18) levels (M30 ELISA) and caspase activity (SR-DEVD-FMK), occurred 24 hours after obatoclax treatment. A phase 1b-2 trial of obatoclax administered using two infusion regimens in combination with carboplatin and etoposide has been completed in previously untreated patients with extensive-stage SCLC. Circulating pharmacodynamic biomarkers of cell death, full-length and/or cleaved CK18, and oligonucleosomal DNA were studied in the phase 1b trial. All SCLC patients classified as "responders" after two cycles of treatment showed significantly increased levels of full-length and cleaved CK18 (M65 ELISA) on day 3 of study. However, the preclinical data and the absence of a peak in circulating caspase-cleaved CK18 in trial patients suggest suboptimal timing of blood sampling, which will need refinement in future trials incorporating obatoclax.

Novel compounds in the treatment of lung cancer: current and developing therapeutic agents

Lung cancer is the leading cause of cancer-related death in the United States. Though incremental advances have been made in the treatment of this devastating disease during the past decade, new therapies are urgently needed. Traditional cytotoxic agents have been combined with other modalities with improved survival for early-stage patients. Newer cytotoxic agents targeting the same or different mechanisms have been developed at different stages. Optimization of various chemotherapy regimens in different settings is one of the aims of current clinical trials. Some predictive biomarkers (eg, excision repair cross-complementing 1, ERCC1) and histotypes (eg, adenocarcinoma) are found to be associated with resistance/response to some cytotoxic drugs. Another notable advance is the addition of targeted therapy to lung cancer treatment. Targeted agents such as erlotinib and bevacizumab have demonstrated clinical benefits and gained Food and Drug Administration approval for lung cancer. More agents targeting various signaling pathways critical to lung cancer are at different stages of development. Along with the effort of new targeted drug discovery, biomarkers such as epidermal growth factor receptor and anaplastic lymphoma kinase mutations have proven useful for patient selection, and more predictive biomarkers have been actively evaluated in non-small cell lung cancer. The paradigm of lung cancer treatment has shifted towards biomarker-based personalized medicine.

Phase I/II study of AT-101 with topotecan in relapsed and refractory small cell lung cancer

INTRODUCTION

AT-101 is an oral, pan Bcl-2 family protein inhibitor that has demonstrated activity in small cell lung cancer (SCLC) models. A phase I/II study was conducted combining AT-101 with topotecan in relapsed and refractory SCLC.

METHODS

An open-labeled multicenter phase I/II study was conducted of oral AT-101 with intravenous topotecan in patients with SCLC who had progressed on prior platinum-containing chemotherapy. The phase II portion was a two-stage design, and two cohorts of patients, sensitive relapsed and refractory, were analyzed. Primary endpoint in the two-stage phase II portion was response rate; secondary endpoints were duration of response and time to progression.

RESULTS

Thirty-six patients were enrolled. The most common toxicities were hematologic, as would be expected with topotecan and AT-101. The recommended phase II dose was 40 mg AT-101 days 1 to 5 with topotecan 1.25 mg/m(2) days 1 to 5 on a 21-day cycle. In the sensitive-relapsed cohort (n = 18), there were 0 complete response (CR), three partial response (PR), 10 stable disease (SD), and four progressive disease (PD). In the refractory cohort (n = 12), there were 0 CR/PR, five SD, and five PD. The study did not meet its prespecified endpoints to continue enrollment in the second stage of the phase II study. Median time to progression in the sensitive-relapsed cohort was 17.4 weeks and 11.7 weeks in the refractory cohort.

CONCLUSIONS

AT-101 can be safely combined with topotecan at a reduced dose of 1.25 mg/m(2). The response rates observed did not meet the criteria for additional enrollment; however, many patients had a best response of SD and the median time to progression in both cohorts was favorable. Additional trials of AT-101 in SCLC are ongoing.

A hierarchical Bayesian design for phase I trials of novel combinations of cancer therapeutic agents

We propose a hierarchical model for the probability of dose-limiting toxicity (DLT) for combinations of doses of two therapeutic agents. We apply this model to an adaptive Bayesian trial algorithm whose goal is to identify combinations with DLT rates close to a prespecified target rate. We describe methods for generating prior distributions for the parameters in our model from a basic set of information elicited from clinical investigators. We survey the performance of our algorithm in a series of simulations of a hypothetical trial that examines combinations of four doses of two agents. We also compare the performance of our approach to two existing methods and assess the sensitivity of our approach to the chosen prior distribution.

The essential role of evasion from cell death in cancer

The link between evasion of apoptosis and the development of cellular hyperplasia and ultimately cancer is implicitly clear if one considers how many cells are produced each day and, hence, how many cells must die to make room for the new ones (reviewed in Raff, 1996). Furthermore, cells are frequently experiencing noxious stimuli that can cause lesions in their DNA and faults in DNA replication can occur during cellular proliferation. Such DNA damage needs to be repaired efficiently or cells with irreparable damage must be killed to prevent subsequent division of aberrant cells that may fuel tumorigenesis (reviewed in Weinberg, 2007). The detection of genetic lesions in human cancers that activate prosurvival genes or disable proapoptotic genes have provided the first evidence that defects in programmed cell death can cause cancer (Tagawa et al., 2005; Tsujimoto et al., 1984; Vaux, Cory, and Adams, 1988) and this concept was proven by studies with genetically modified mice (Egle et al., 2004b; Strasser et al., 1990a). It is therefore now widely accepted that evasion of apoptosis is a requirement for both neoplastic transformation and sustained growth of cancer cells (reviewed in Cory and Adams, 2002; Hanahan and Weinberg, 2000; Weinberg, 2007). Importantly, apoptosis is also a major contributor to anticancer therapy-induced killing of tumor cells (reviewed in Cory and Adams, 2002; Cragg et al., 2009). Consequently, a detailed understanding of apoptotic cell death will help to better comprehend the complexities of tumorigenesis and should assist with the development of improved targeted therapies for cancer based on the direct activation of the apoptotic machinery (reviewed in Lessene, Czabotar, and Colman, 2008).

In vitro modulation of Bcl-2 levels in small cell lung cancer cells: effects on cell viability

Small cell lung cancer (SCLC) is an aggressive disease, representing 15% of all cases of lung cancer, has high metastatic potential and low prognosis that urgently demands the development of novel therapeutic approaches. One of the proposed approaches has been the down-regulation of BCL2, with poorly clarified and controversial therapeutic value regarding SCLC. The use of anti-BCL2 small interfering RNA (siRNA) in SCLC has never been reported. The aim of the present study was to select and test the in vitro efficacy of anti-BCL2 siRNA sequences against the protein and mRNA levels of SCLC cells, and their effects on cytotoxicity and chemosensitization. Two anti-BCL2 siRNAs and the anti-BCL2 G3139 oligodeoxynucleotide (ODN) were evaluated in SCLC cells by the simultaneous determination of Bcl-2 and viability using a flow cytometry method recently developed by us in addition to Western blot, real-time reverse-transcription PCR, and cell growth after single and combined treatment with cisplatin. In contrast to previous reports about the use of ODN, a heterogeneous and up to 80% sequence-specific Bcl-2 protein knockdown was observed in the SW2, H2171 and H69 SCLC cell lines, although without significant sequence-specific reduction of cell viability, cell growth, or sensitization to cisplatin. Our results question previous data generated with antisense ODN and supporting the present concept of the therapeutic interest in BCL2 silencing per se in SCLC, and support the growing notion of the necessity of a multitargeting molecular approach for the treatment of cancer.

[Molecular targeted therapies in small-cell lung cancer]

Small-cell lung cancers (SCLC) are aggressive malignancies, however, characterized by high primary chemosensitivity. Unfortunately, for the vast majority of patients, relapse is the rule with emergence of secondary resistance mechanisms. In the era of molecular targeted therapies, characterization of a number of molecular abnormalities has encouraged implementation of several clinical trials. This literature review summarizes the various pharmacological approaches used in SCLC to improve survival in localized and extensive forms of the disease. Initial trials with molecular targeted therapies have not been able to improve clinical outcome compared to the standard etoposide-cisplatin chemotherapy regimen in extensive forms. However, new targets continue to be identified and many treatments are currently being assessed, including blockade of angiogenesis, signal transduction, cell cycle or induction of apoptosis.

Phase I trial of oblimersen (Genasense®) and gemcitabine in refractory and advanced malignancies

BACKGROUND

Overexpression of Bcl-2 is associated with worse prognosis for a number of cancer types. The present study was designed to determine the maximum tolerated dose (MTD) of oblimersen (antisense Bcl-2) and gemcitabine when administered to patients with refractory malignancies.

MATERIALS AND METHODS

Sixteen patients with advanced solid tumors refractory to standard therapies were treated with escalating doses of oblimersen continuous, 120-h intravenous infusion given every 14 days, with a fixed-dose-rate intravenous infusion of gemcitabine administered on day 5 of each cycle. Serial plasma samples were collected to calculate the pharmacokinetics of oblimersen and gemcitabine, and also to measure the effect of oblimersen on Bcl-2 expression.

RESULTS

7 women and 9 men, median age 55 years (range 35-74 years), received a 5-day infusion of oblimersen at dose levels of 5 mg/kg/day (n = 4) or 7 mg/kg/day (n = 12). On the 5th day of the infusion, gemcitabine was given at 10 mg/m(2)/h for a total dose of 1,000 mg/m(2) (n = 7; cohorts I and II), 1,200 mg/m(2) (n = 3; cohort III), or 1,500 mg/m(2) (n = 6; cohort IV). Edema was the dose-limiting toxicity (DLT), necessitating expansion of cohort IV. No subsequent DLTs were noted. Thus, the maximum planned doses were well tolerated, and a formal MTD was not determined. Most hematologic toxicities were grade 1 or 2. There was low-grade fatigue, nausea/vomiting, and myalgias/arthralgias. Oblimersen C(ss) and AUC increased in relation to the dose escalation, but gemcitabine triphosphate levels did not correlate well with dose. There were no objective responses, though 5 patients had stable disease. A >75% reduction in Bcl-2 expression in peripheral blood mononuclear leucocytes was seen more frequently in patients who achieved stable disease than in progressing patients.

CONCLUSIONS

The maximal planned dose levels of oblimersen and gemcitabine in combination were well tolerated. Only one DLT (edema) occurred. There was a correlation between Bcl-2 reduction and stable disease. The recommended doses of the drugs for future studies are 7 mg/kg/day of oblimersen on days 1-5, and gemcitabine 1,500 mg/m(2) on day 5, every two weeks.

A phase I trial of oblimersen sodium in combination with cisplatin and 5-fluorouracil in patients with advanced esophageal, gastroesophageal junction, and gastric carcinoma

PURPOSE

To determine the maximum tolerated dose of oblimersen, an antisense oligonucleotide directed to the Bcl-2 mRNA, in combination with cisplatin and 5-flourouracil in patients with advanced gastric and esophageal carcinoma.

METHODS

Patients were treated with escalating doses of oblimersen administered by continuous intravenous infusion (CIVI) days 1 to 7, CIVI 5-fluorouracil (5-FU) days 4 to 7, and cisplatin on day 4 every 3 weeks.

RESULTS

Fifteen patients received a total of 49 courses of oblimersen at doses of 3, 5, or 7 mg/kg/d given as a 7 day CIVI in combination with 4 or 5 day CIVI of 5-FU (1000 or 750 mg/m2/d) plus intravenous cisplatin (100 or 75 mg/m2 over 2 hours). The recommended phase II dose of oblimersen was 5 mg/kg/d in combination with 5-FU (750 mg/m2/d for 4 days) and cisplatin (75 mg/m). The most common grade 3 to 4 adverse events that occurred in at least 10% of patients at all dose levels included neutropenia (33%), hypokalemia (27%), infection (20%), and mucositis, fatigue, dizziness, thrombosis, and dehydration (in 13% for each category).

CONCLUSION

The combination of oblimersen with 5-FU and cisplatin chemotherapy is feasible in patients with advanced upper gastrointestinal cancer, with antitumor activity observed in gastric carcinoma.

Emerging drugs for small-cell lung cancer

Small-cell lung cancer (SCLC) is a rapidly progressing tumor in which chemotherapy has a limited impact on survival. Unfortunately, little progress has been made in the medical management of SCLC during the last 30 years, which is best exemplified by the fact that standard first-line chemotherapy has remained platinum-based over time. On the other hand, improvements in survival have been obtained only with the introduction of innovative radiation strategies such as accelerated hyperfractionation to the thorax for limited-stage disease and prophylactic cranial irradiation for both limited- and extensive-stage disease. However, recent advances in the understanding of SCLC biology have renewed the interest in the clinical development of active drugs for SCLC. In this review, we address the most promising agents under clinical evaluation, discussing both novel chemotherapeutic agents and targeted agents. Particularly, amrubicin, a fully synthetic anthracycline, is a very active agent for SCLC, and ongoing Phase III trials are evaluating this agent either in the first-line setting of extensive-stage or relapsed disease. Among targeted agents, anti-angiogenic strategies and Bcl-2 inhibitors represent the most promising approaches, and they are being specifically tested in combination with and/or as maintenance therapy after first-line platinum-based chemotherapy.

Gene therapy for mesothelioma and lung cancer

Both malignant pleural mesothelioma and advanced stage lung cancer are associated with a poor prognosis. Unfortunately, current treatment regimens have had only a modest effect on their progressive course. Gene therapy for thoracic malignancies represents a novel therapeutic approach and has been evaluated in a number of clinical trials over the last two decades. Using viral vectors or anti-sense RNA, strategies have included induction of apoptosis, tumor suppressor gene replacement, suicide gene expression, cytokine-based therapy, various vaccination approaches, and adoptive transfer of modified immune cells. This review will consider the clinical results, limitations, and future directions of gene therapy trials for thoracic malignancies.

Targeting the Bcl-2

PURPOSE OF REVIEW

Members of the Bcl-2 family of proteins are critical components in regulating the intrinsic apoptotic pathway. Bcl-2 protein overexpression is associated with drug resistance and poor clinical outcome in cancer patients. Preclinical and clinical evaluations demonstrate that downregulation of Bcl-2 restores the intrinsic apoptotic pathways with antitumor effects. Thus, Bcl-2 is aggressively pursued as a therapeutic target in cancer with several new drugs undergoing clinical investigations. In this manuscript, we will review clinical information on some of the novel compounds specifically designed to target the Bcl-2 gene product(s).

RECENT FINDINGS

Extensive clinical evaluations using a Bcl-2-specific antisense have resulted in an overall disappointing experience. But new small molecule inhibitors of the Bcl-2 hold promise with high target affinity, ease of administration and improved toxicity profile. Early stage clinical trials of these agents are revealing promising results alone as well as in combination with existing anticancer therapeutics. Encouraging results from some of these clinical investigations are summarized in this review.

SUMMARY

Downregulation of Bcl-2 and restoration of a critical apoptotic pathway in cancer cells remains an important strategy. Novel Bcl-2 inhibitors have started to deliver the therapeutic promise of this target-specific quest.

G3139 (Genasense) in patients with advanced merkel cell carcinoma

OBJECTIVES

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine malignancy of the skin. Preclinical studies have identified up-regulation of the critical antiapoptosis gene bcl-2 in MCC. We conducted a multicenter phase II trial of the novel bcl-2 antisense agent (G3139, Genasense) in patients with advanced MCC.

METHODS

Twelve patients (9 men, 3 women) with histologically confirmed metastatic or regionally recurrent MCC were enrolled. Ten patients (83%) had received prior chemotherapy. Eight patients (67%) had Karnofsky performance status of 90 to 100. Patients received continuous IV infusion of G3139 (7 mg/kg/d) via central venous access in an outpatient setting for 14 days, followed by a 7-day rest period. Response was assessed at 6-week intervals. Patients were allowed to continue therapy until unacceptable toxicity or disease progression.

RESULTS

No objective responses were observed. The best response was stable disease in 3 patients and progressive disease in 9 patients. A median of 4 doses per patient (total 46 doses) was administered. Dose delays and/or reductions were required in 6 patients. One patient developed grade 4 lymphopenia. One patient developed grade 3 renal failure characterized by grade 3-elevated creatinine and grade 4 hyperkalemia. Other grade 3 events included cytopenia (n = 5), aspartate aminotransferase/alanine aminotranferease elevation (n = 3), hypophosphatemia (n = 2), and pain (n = 1). The most frequent grade 1 to 2 toxicities were elevated creatinine, ALT elevation, hypokalemia, lymphopenia, and fatigue.

CONCLUSIONS

Bcl-2 antisense therapy (G3139) was well tolerated among patients with advanced MCC. Although probable antitumor activity was documented in 1 patient, no objective responses per Response Evaluation Criteria in Solid Tumors criteria were observed.

Small mitochondria-targeting molecules as anti-cancer agents

Alterations in mitochondrial structure and functions have long been observed in cancer cells. Targeting mitochondria as a cancer therapeutic strategy has gained momentum in the recent years. The signaling pathways that govern mitochondrial function, apoptosis and molecules that affect mitochondrial integrity and cell viability have been important topics of the recent review in the literature. In this article, we first briefly summarize the rationale and biological basis for developing mitochondrial-targeted compounds as potential anti-cancer agents, and then provide key examples of small molecules that either directly impact mitochondria or functionally affect the metabolic alterations in cancer cells with mitochondrial dysfunction. The main focus is on the small molecular weight compounds with potential applications in cancer treatment. We also summarize information on the drug developmental stages of the key mitochondria-targeted compounds and their clinical trial status. The advantages and potential shortcomings of targeting the mitochondria for cancer treatment are also discussed.

A phase I/II study of GTI-2040 plus docetaxel as second-line treatment in advanced non-small cell lung cancer: a study of the PMH phase II consortium

INTRODUCTION

GTI-2040, an antisense oligonucleotide, targets the ribonucleotide reductase R2 subunit, critical for DNA synthesis. This study determined the recommended phase II dose (RP2D) of docetaxel plus GTI-2040, toxicity, and response rate in advanced non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Advanced solid tumor patients, preferably with platinum-treated NSCLC, performance status 0 to 2, no symptomatic central nervous system metastases, adequate organ and bone marrow function, and >or=1 prior chemotherapy regimen were treated with escalating doses of GTI-2040 given by 14-day continuous intravenous infusion (CVI) plus docetaxel every 21 days.

RESULTS

Twenty-nine patients were treated, (24 NSCLC, 3 hormone-refractory prostate cancer, 1 head and neck, and 1 small cell lung cancer). GTI-2040 5 mg/kg as CVI for 14 days plus docetaxel 75 mg/m(2) intravenously every 21days was determined as the RP2D. Dose-limiting toxicity was not seen. Two patients at RP2D developed grade 4/5 febrile neutropenia. One prostate specific antigen response was seen in phase I, but no objective tumor responses in the NSCLC patients. Median time to progression was 3.4 months, 3.2 months in the NSCLC patients treated at RP2D.

CONCLUSIONS

Activity of the combination at RP2D, GTI-2040 5 mg/kg/d x 14 days by CVI plus docetaxel 75 mg/m(2) does not seem superior to docetaxel alone in previously treated NSCLC.

New advances in the second-line treatment of small cell lung cancer

Lung cancer is the leading cause of cancer-related death in the U.K., with small cell histology accounting for 15%-20% of cases. Small cell lung cancer (SCLC) is initially a chemosensitive disease, but relapse is common, and in this group of patients it remains a rapidly lethal disease with a particularly poor prognosis. The choice of second-line chemotherapy for patients with relapsed SCLC has been an area of difficulty for oncologists, and until recently there was no randomized evidence for its use over best supportive care (BSC). Topotecan is currently the only drug licensed in Europe and the U.S. for this indication, having been shown in a phase III trial to lead to longer overall survival and better quality of life than with BSC. In this article, we review the current evidence for the use of second-line cytotoxic therapy and also the emerging role of novel agents and targeted therapies in this setting. In particular, we explore the role of the Bcl-2 protein family, which are key regulators of mitochondrial apoptosis and are implicated in resistance to anticancer therapies. SCLC overexpresses antiapoptotic members of the Bcl-2 family in approximately 80% of cases. Several Bcl-2 inhibitors, including obatoclax, are currently entering clinical trials in SCLC and are an exciting area of drug development in the relapsed setting.

Phase I/II study of G3139 (Bcl-2 antisense oligonucleotide) in combination with doxorubicin and docetaxel in breast cancer

PURPOSE

Preclinical data showed enhancement of breast cancer cell death when G3139 was combined with anthracyclines and taxanes. We evaluated the efficacy and safety of a Bcl-2 antisense oligonucleotide, G3139, in combination with doxorubicin (A) and docetaxel (T) in patients with locally advanced breast cancer (LABC).

EXPERIMENTAL DESIGN

Following a brief phase I to determine the phase II dose, patients with locally advanced breast cancer received G3139 administered by continuous i.v. infusion for 5 to 7 days with bolus A (50 mg/m2) and T (75 mg/m2) administered on either day 3 or 6 of therapy with G3139. Cycles were repeated every 21 days x 6 in the neoadjuvant setting. Serial plasma samples were obtained for pharmacokinetic analysis. Tissue samples were obtained before and after therapy for pharmacodynamic analysis of Bcl-2 expression.

RESULTS

Thirty patients (median age, 49 years; range, 24-71 years) received 160 cycles. During the phase I portion of the trial, the dose of G3139 was escalated from 3 to 7 mg/kg/d (i.v. for 5 days) in combination with AT. During the phase II portion of the trial, several doses and schedules of G3139 were evaluated. There were no pathologic complete responses. Pharmacodynamic studies showed limited Bcl-2 down-regulation in the primary tumors.

CONCLUSIONS

G3139 in combination with doxorubicin and docetaxel is well tolerated. No pathologic complete response was seen and pharmacodynamic studies showed very little down-regulation of Bcl-2 in primary tumors, perhaps related to issues with insufficient drug delivery to the intact tumor.

A phase I pharmacokinetic and pharmacodynamic correlative study of the antisense Bcl-2 oligonucleotide g3139, in combination with carboplatin and paclitaxel, in patients with advanced solid tumors

PURPOSE

This phase I trial assessed the safety and tolerability of G3139 when given in combination with carboplatin and paclitaxel chemotherapy. The effect of G3139 treatment on Bcl-2 expression in peripheral blood mononuclear cells (PBMC) and paired tumor biopsies was also determined.

EXPERIMENTAL DESIGN

Patients with advanced solid malignancies received various doses of G3139 (continuous i.v. infusion days 1-7), carboplatin (day 4), and paclitaxel (day 4), repeated in 3-week cycles, in a standard cohort-of-three dose-escalation schema. Changes in Bcl-2/Bax transcription/expression were assessed at baseline and day 4 (prechemotherapy) in both PBMCs and paired tumor biopsies. The pharmacokinetic interactions between G3139 and carboplatin/paclitaxel were measured.

RESULTS

Forty-two patients were evaluable for safety analysis. Primary toxicities were hematologic (myelosuppression and thrombocytopenia). Dose escalation was stopped with G3139 at 7 mg/kg/d, carboplatin at area under the curve of 6, and paclitaxel at 175 mg/m(2) due to significant neutropenia seen in cycle 1 and safety concerns in further escalating chemotherapy in this phase I population. With G3139 at 7 mg/kg/d, 13 patients underwent planned tumor biopsies, of which 12 matched pairs were obtained. Quantitative increases in intratumoral G3139 with decreases in intratumoral Bcl-2 gene expression were seen. This paralleled a decrease in Bcl-2 protein expression observed in PBMCs.

CONCLUSIONS

Although the maximal tolerated dose was not reached, the observed toxicities were consistent with what one would expect from carboplatin and paclitaxel alone. In addition, we show that achievable intratumoral G3139 concentrations can result in Bcl-2 down-regulation in solid tumors and PBMCs.

Genetic changes in small cell lung carcinoma

Small cell lung carcinoma (SCLC) accounts for approximately 15% of all lung cancer cases. Despite a frequently good response to first-line treatment with chemotherapy and/or radiotherapy, early relapse occurs in the majority of patients and 5-year survival is only about 5%. Therefore, there is a need to develop novel treatments to improve the outcome of patients with SCLC. To fulfil this need, it is critical to gain further understanding on the molecular basis of SCLC and specifically to identify novel therapeutic targets. Clinical trials with molecularly targeted agents have been performed with little success in the past, but recently many promising oncogenic pathways have been discovered and novel targeted therapies are under evaluation. In this review, we summarise the most relevant genetic and signalling pathway alterations reported to date in SCLC and discuss the potential therapeutic implications of such events.

Activity of the Bcl-2 family inhibitor ABT-263 in a panel of small cell lung cancer xenograft models

PURPOSE

The purpose of this study was to characterize the activity of the Bcl-2 protein family inhibitor ABT-263 in a panel of small cell lung cancer (SCLC) xenograft models.

EXPERIMENTAL DESIGN

A panel of 11 SCLC xenograft models was established to evaluate the efficacy of ABT-263. Single agent activity was examined on a continuous dosing schedule in each of these models. The H146 model was used to further evaluate dose and schedule, comparison to standard cytotoxic agents, and induction of apoptosis.

RESULTS

ABT-263 exhibited a range of antitumor activity, leading to complete tumor regression in several models. Significant regressions of tumors as large as 1 cc were also observed. The efficacy of ABT-263 was also quite durable; in several cases, minimal tumor regrowth was noted several weeks after the cessation of treatment. Antitumor effects were equal or superior to that of several clinically approved cytotoxic agents. Regression of large established tumors was observed through several cycles of therapy and efficacy was retained in a Pgp-1 overexpressing line. Significant efficacy was observed on several dose and therapeutic schedules and was associated with significant induction of apoptosis.

CONCLUSIONS

ABT-263 is a potent, orally bioavailable inhibitor of Bcl-2 family proteins that has recently entered clinical trials. The efficacy data reported here suggest that SCLC is a promising area of clinical investigation with this agent.

Therapeutic efficacy of ABT-737, a selective inhibitor of BCL-2, in small cell lung cancer

Bcl-2 is a central regulator of cell survival that is overexpressed in the majority of small cell lung cancers (SCLC) and contributes to both malignant transformation and therapeutic resistance. We compared primary SCLC xenografts prepared from de novo human tumors with standard cell line-based xenografts in the evaluation of a novel and highly potent small molecule inhibitor of Bcl-2, ABT-737. ABT-737 induced dramatic regressions in tumors derived from some SCLC cell lines. In contrast, only one of three primary xenograft SCLC tumors showed significant growth inhibition with ABT-737. Explanations for this apparent dichotomy may include relatively low expression of Bcl-2 in the primary xenografts or inherent differences in the model systems. The addition of etoposide to ABT-737 in the primary xenografts resulted in significant decreases in tumor growth, underscoring the clinical potential of ABT-737 in combination therapy. To identify factors that may contribute to resistance to ABT-737 and related inhibitors, we isolated resistant derivatives of an initially sensitive cell line-based xenograft. Acquired resistance in this model was associated with decreases in the expression of the primary target Bcl-2, of proapoptotic partners of Bcl-2 (Bax and Bim), and of Bcl-2:Bim heterodimers. Expression profiling reveals 85 candidate genes demonstrating consistent changes in gene expression with acquired resistance. Taken together, these data have specific implications for the clinical development of Bcl-2 inhibitors for SCLC and broader implications for the testing of novel anticancer strategies in relevant preclinical models.

Targeting the Bcl-2-regulated apoptosis pathway by BH3 mimetics: a breakthrough in anticancer therapy?

Induction of apoptosis in tumor cells by direct activation of the Bcl-2-regulated apoptosis pathway by small molecule drugs carries high hopes to overcome the shortcomings of current anticancer therapies. This novel therapy concept builds on emerging insights into how Bcl-2-like molecules maintain mitochondrial integrity and how pro-apoptotic BH3-only proteins lead to its disruption. Means to unleash the pro-apoptotic potential of BH3-only proteins in tumor cells, or to bypass the need for BH3-only proteins by directly blocking possible interactions of Bcl-2-like pro-survival molecules with Bax and/or Bak, constitute interesting options for the design of novel anticancer therapies. For the optimization and clinical implementation of these novel anticancer strategies, a detailed understanding of the role of individual BH3-only proteins in cell death signaling in healthy cells and during tumor suppression is required. In this review, we will touch on the latest findings on BH3-only protein function and attempts to define the molecular properties of the so-called 'BH3 mimetics,' a novel class of anticancer agents, able to prompt apoptosis in tumor cells, regardless of their p53 or Bcl-2 status.

Novel systemic therapies for small cell lung cancer

A diagnosis of small cell lung cancer (SCLC) today confers essentially the same terrible prognosis that it did 25 years ago, when common use of cisplatin-based chemotherapy began for this disease. In contrast to past decades of research on many other solid tumors, studies of combination chemotherapy using later generation cytotoxics and targeted kinase inhibitors have not had a significant impact on standard care for SCLC. The past few years have seen suggestions of incrementally improved outcomes using standard cytotoxics, including cisplatin-based combination studies of irinotecan and amrubicin by Japanese research consortia. Confirmatory phase III studies of these agents are ongoing in the United States. Antiangiogenic strategies are also of primary interest and are in late-phase testing. Several novel therapeutics, including high-potency small molecule inhibitors of Bcl-2 and the Hedgehog signaling pathway, and a recently discovered replication-competent picornavirus, have shown remarkable activity against SCLC in preclinical models and are currently in simultaneous phase I clinical development. Novel therapeutic approaches based on advances in understanding of the biology of SCLC have the potential to radically change the outlook for patients with this disease.

Randomized phase II Study of carboplatin and etoposide with or without the bcl-2 antisense oligonucleotide oblimersen for extensive-stage small-cell lung cancer: CALGB 30103

PURPOSE

To assess the efficacy and toxicity of carboplatin, etoposide, and the bcl-2 antisense oligonucleotide oblimersen as initial therapy for extensive-stage small-cell lung cancer (ES-SCLC). bcl-2 has been implicated as a key factor in SCLC oncogenesis and chemotherapeutic resistance.

PATIENTS AND METHODS

A 3:1 randomized phase II study was performed to evaluate carboplatin and etoposide with (arm A) or without oblimersen (arm B) in 56 assessable patients with chemotherapy-naïve ES-SCLC. Outcome measures including toxicity, objective response rate, complete response rate, failure-free survival, overall survival, and 1-year survival rate.

RESULTS

Oblimersen was associated with slightly more grade 3 to 4 hematologic toxicity (88% v 60%; P = .05). Response rates were 61% (95% CI, 45% to 76%) for arm A and 60% (95% CI, 32% to 84%) for arm B. The percentage of patients alive at 1 year was 24% (95% CI, 12% to 40%) with oblimersen, and 47% (95% CI, 21% to 73%) without oblimersen. Hazard ratios for failure-free survival (1.79; P = .07) and overall survival (2.13; P = .02) suggested worse outcome for patients receiving oblimersen. These results hold when adjusted for other prognostic factors, such as weight loss, in multivariate regression analysis.

CONCLUSION

Despite extensive data supporting a critical role for Bcl-2 in chemoresistance in SCLC, addition of oblimersen to a standard regimen for this disease did not improve any clinical outcome measure. Emerging data from several groups suggest that this lack of efficacy may be due to insufficient suppression of Bcl-2 in vivo. Additional evaluation of this agent in SCLC is not warranted.