Multi-Institutional Phase I/II Trial of Oral Bexarotene in Combination With Cisplatin and Vinorelbine in Previously Untreated Patients With Advanced Non–Small-Cell Lung Cancer

The novel function of bexarotene for neurological diseases

Bexarotene, a retinoid X receptor (RXR) agonist, is approved by FDA to treat cutaneous T-cell lymphoma. However, it has also demonstrated promising therapeutic potential for neurological diseases such as stroke, traumatic brain injury, Parkinson's disease, and particularly Alzheimer's disease(AD). In AD, bexarotene inhibits the production and aggregation of amyloid β (Aβ), activates Liver X Receptor/RXR heterodimers to increase lipidated apolipoprotein E to remove Aβ, mitigates the negative impact of Aβ, regulates neuroinflammation, and ultimately improves cognitive function. For other neurological diseases, its mechanisms of action include inhibiting inflammatory responses, up-regulating microglial phagocytosis, and reducing misfolded protein aggregation, all of which aid in alleviating neurological damage. Here, we briefly discuss the characteristics, applications, and adverse effects of bexarotene, summarize its pharmacological mechanisms and therapeutic results in various neurological diseases, and elaborate on the problems encountered in preclinical research, with the aim of providing help for the further application of bexarotene in central nervous system diseases.

Modulating retinoid-X-receptor alpha (RXRA) expression sensitizes chronic myeloid leukemia cells to imatinib in vitro and reduces disease burden in vivo

Introduction: The ligand-activated transcription factors, nuclear hormone receptors (NHRs), remain unexplored in hematological malignancies except for retinoic acid receptor alpha (RARA). Methods: Here we profiled the expression of various NHRs and their coregulators in Chronic myeloid leukemia (CML) cell lines and identified a significant differential expression pattern between inherently imatinib mesylate (IM)-sensitive and resistant cell lines. Results: Retinoid-X-receptor alpha (RXRA) was downregulated in CML cell lines inherently resistant to IM and in primary CML CD34⁺ cells. Pre-treatment with clinically relevant RXRA ligands improved sensitivity to IM in-vitro in both CML cell lines and primary CML cells. This combination effectively reduced the viability and colony-forming capacity of CML CD34⁺ cells in-vitro. In-vivo, this combination reduced leukemic burden and prolonged survival. Overexpression (OE) of RXRA inhibited proliferation and improved sensitivity to IM in-vitro. In-vivo, RXRA OE cells showed reduced engraftment of cells in the bone marrow, improved sensitivity to IM, and prolonged survival. Both RXRA OE and ligand treatment markedly reduced BCR::ABL1 downstream kinase activation, activating apoptotic cascades and improving sensitivity to IM. Importantly, RXRA OE also led to the disruption of the oxidative capacity of these cells. Conclusion: Combining IM with clinically available RXRA ligands could form an alternative treatment strategy in CML patients with suboptimal response to IM.

The Novel RXR Agonist MSU-42011 Differentially Regulates Gene Expression in Mammary Tumors of MMTV-Neu Mice

Retinoid X receptor (RXR) agonists, which activate the RXR nuclear receptor, are effective in multiple preclinical cancer models for both treatment and prevention. While RXR is the direct target of these compounds, the downstream changes in gene expression differ between compounds. RNA sequencing was used to elucidate the effects of the novel RXRα agonist MSU-42011 on the transcriptome in mammary tumors of HER2+ mouse mammary tumor virus (MMTV)-Neu mice. For comparison, mammary tumors treated with the FDA approved RXR agonist bexarotene were also analyzed. Each treatment differentially regulated cancer-relevant gene categories, including focal adhesion, extracellular matrix, and immune pathways. The most prominent genes altered by RXR agonists positively correlate with survival in breast cancer patients. While MSU-42011 and bexarotene act on many common pathways, these experiments highlight the differences in gene expression between these two RXR agonists. MSU-42011 targets immune regulatory and biosynthetic pathways, while bexarotene acts on several proteoglycan and matrix metalloproteinase pathways. Exploration of these differential effects on gene transcription may lead to an increased understanding of the complex biology behind RXR agonists and how the activities of this diverse class of compounds can be utilized to treat cancer.

The continuum of care of anticancer treatment-induced hypothyroidism in patients with solid non thyroid tumors: time for an intimate collaboration between oncologists and endocrinologists

INTRODUCTION

Hypothyroidism is a common adverse event of various anticancer treatment modalities, constituting a notable paradigm of the integration of the endocrine perspective into precision oncology.

AREAS COVERED

The present narrative review provides a comprehensive and updated overview of anticancer treatment-induced hypothyroidism in patients with solid non-thyroid tumors. A study search was conducted on the following electronic databases: PubMed, Google Scholar, Scopus.com, ClinicalTrials.gov, and European Union Clinical Trials Register from 2011 until August 2021.

EXPERT OPINION

In patients with solid non-thyroid tumors, hypothyroidism is a common adverse event of radiotherapy, high dose interleukin 2 (HD IL-2), interferon alpha (IFN-α), bexarotene, immune checkpoint inhibitors (ICPi), and tyrosine kinase inhibitors (TKIs), while chemotherapy may induce hypothyroidism more often than initially considered. The path forward for the management of anticancer treatment-induced hypothyroidism in patients with solid non-thyroid tumors is an integrated approach grounded on 5 pillars: prevention, vigilance, diagnosis, treatment and monitoring. Current challenges concerning anticancer treatment-induced hypothyroidism await counteraction, namely awareness of the growing list of related anticancer treatments, identification of predictive factors, counteraction of diagnostic pitfalls, tuning of thyroid hormone replacement, and elucidation of its prognostic significance. Close collaboration of oncologists with endocrinologists will provide optimal patient care.

The rexinoid V-125 reduces tumor growth in preclinical models of breast and lung cancer

Rexinoids are ligands which activate retinoid X receptors (RXRs), regulating transcription of genes involved in cancer-relevant processes. Rexinoids have anti-neoplastic activity in multiple preclinical studies. Bexarotene, used to treat cutaneous T cell lymphoma, is the only FDA-approved rexinoid. Bexarotene has also been evaluated in clinical trials for lung and metastatic breast cancer, wherein subsets of patients responded despite advanced disease. By modifying structures of known rexinoids, we can improve potency and toxicity. We previously screened a series of novel rexinoids and selected V-125 as the lead based on performance in optimized in vitro assays. To validate our screening paradigm, we tested V-125 in clinically relevant mouse models of breast and lung cancer. V-125 significantly (p < 0.001) increased time to tumor development in the MMTV-Neu breast cancer model. Treatment of established mammary tumors with V-125 significantly (p < 0.05) increased overall survival. In the A/J lung cancer model, V-125 significantly (p < 0.01) decreased number, size, and burden of lung tumors. Although bexarotene elevated triglycerides and cholesterol in these models, V-125 demonstrated an improved safety profile. These studies provide evidence that our screening paradigm predicts novel rexinoid efficacy and suggest that V-125 could be developed into a new cancer therapeutic.

Potential therapeutic uses of rexinoids

The discovery of nuclear receptors, particularly retinoid X receptors (RXR), and their involvement in numerous pathways related to development sparked interest in their immunomodulatory properties. Genetic models using deletion or overexpression of RXR and the subsequent development of several small molecules that are agonists or antagonists of this receptor support a promising therapeutic role for these receptors in immunology. Bexarotene was approved in 1999 for the treatment of cutaneous T cell lymphoma. Several other small molecule RXR agonists have since been synthesized with limited preclinical development, but none have yet achieved FDA approval. Cancer treatment has recently been revolutionized with the introduction of immune checkpoint inhibitors, but their success has been restricted to a minority of patients. This review showcases the emerging immunomodulatory effects of RXR and the potential of small molecules that target this receptor as therapies for cancer and other diseases. Here we describe the essential roles that RXR and partner receptors play in T cells, dendritic cells, macrophages and epithelial cells, especially within the tumor microenvironment. Most of these effects are site and cancer type dependent but skew immune cells toward an anti-inflammatory and anti-tumor effect. This beneficial effect on immune cells supports the promise of combining rexinoids with approved checkpoint blockade therapies in order to enhance efficacy of the latter and to delay or potentially eliminate drug resistance. The data compiled in this review strongly suggest that targeting RXR nuclear receptors is a promising new avenue in immunomodulation for cancer and other chronic inflammatory diseases.

Beyond the limitation of targeted therapy: Improve the application of targeted drugs combining genomic data with machine learning

Precision oncology involves effectively selecting drugs for cancer patients and planning an effective treatment regimen. However, for Molecular targeted drug, using genomic state of the drug target to select drugs has limitations. Many patients who could benefit from molecularly targeted drugs, but they are being missed due to the insufficient labelling ability of the existing target genes. For non-specific chemotherapy drugs, most of the first-line anticancer drugs do not have biomarkers to guide doctor make treatment regimen. Furthermore, it is important to determine a long-term treatment plan based on the patient's genomic data during tumor evolution. Therefore, it is necessary to establish a tumor drug sensitivity prediction model, which can assist doctors in designing a personalized tumor treatment regimen. This paper proposed a novel model to predict tumor drug sensitivity including targeted drugs and non-specific chemotherapy drugs. This model uses statistical methods based on Bimodal distribution to select multimodal genetic data to solve dimensional challenges and reduce noise and to establish a classification model to predict the effectiveness of the drug in the tumor cell line using machine learning. The experimental test 87 molecular targeted drugs and non-specific chemotherapy drugs. The results show that the method can effectively predict the sensitivity of tumor drugs with an average sensitivity of 0.98 and specificity of 0.97. This model is worth to promotion. If it can be successfully used in clinical trials, it will effectively assist doctors to develop personalized cancer treatment programs and expand the application of molecularly targeted drugs.

Drug Combinatorial Therapies for the Treatment of KRAS Mutated Lung Cancers

KRAS is the most common oncogene to be mutated in lung cancer, and therapeutics directly targeting KRAS have proven to be challenging. The mutations of KRAS are associated with poor prognosis, and resistance to both adjuvant therapy and targeted EGFR TKI. EGFR TKIs provide significant clinical benefit for patients whose tumors bear EGFR mutations. However, tumors with KRAS mutations rarely respond to the EGFR TKI therapy. Thus, combination therapy is essential for the treatment of lung cancers with KRAS mutations. EGFR TKI combined with inhibitors of MAPKs, PI3K/mTOR, HDAC, Wee1, PARP, CDK and Hsp90, even miRNAs and immunotherapy, were reviewed. Although the effects of the combination vary, the combined therapeutics are one of the best options at present to treat KRAS mutant lung cancer.

Cancer Chemoprevention: Preclinical In Vivo Alternate Dosing Strategies to Reduce Drug Toxicities

Cancer chemopreventive agents inhibit the formation of precursor lesions and/or the progression of these lesions to late stage disease. This approach to disease control has the potential to reduce the physical and financial costs of cancer in society. Several drugs that have been approved by the FDA for other diseases and have been extensively evaluated for their safety and pharmacokinetic/pharmacodynamic characteristics have the potential to be repurposed for use as cancer chemopreventive agents. These agents often mechanistically inhibit signaling molecules that play key roles in the carcinogenic process. The safety profile of agents is a primary concern when considering the administration of drugs for chemoprevention, as the drugs will be given chronically to high-risk, asymptomatic individuals. To decrease drug toxicity while retaining efficacy, several approaches are currently being explored. In this short review, we describe studies that use preclinical in vivo models to assess efficacy of alternative drug dosing strategies and routes of drug administration on chemopreventive drug efficacy. In vivo drug dosing strategies that reduce toxicity while retaining efficacy will pave the way for future cancer prevention clinical trials.

The potential of retinoids for combination therapy of lung cancer: Updates and future directions

Lung cancer is the most common cancer-related death worldwide. Natural compounds have shown high biological and pharmaceutical relevance as anticancer agents. Retinoids are natural derivatives of vitamin A having many regulatory functions in the human body, including vision, cellular proliferation and differentiation, and activation of tumour suppressor genes. Retinoic acid (RA) is a highly active retinoid isoform with promising anti-lung cancer activity. The abnormal expression of retinoid receptors is associated with loss of anticancer activities and acquired resistance to RA in lung cancer. The preclinical promise has not translated to the general clinical utility of retinoids for lung cancer patients, especially those with a history of smoking. Newer retinoid nano-formulations and the combinatorial use of retinoids has been associated with lower toxicity and more favorably efficacy in both the preclinical and clinical settings. Here, we highlight epidemiological and clinical therapeutic studies involving retinoids and lung cancer. We also discuss the biological actions of retinoids in lung cancer, which include effects on cancer stem cell differentiation, angiogenesis, metastasis, and proliferative. We suggest that the use of retinoids in combination with conventional and targeted anticancer agents will broaden the utility of these potent anticancer compounds in the lung cancer clinic.

A phase I/II study of bexarotene with carboplatin and weekly paclitaxel for the treatment of patients with advanced non-small cell lung cancer

BACKGROUND

Rexinoids demonstrate anti-proliferative differentiation-inducing activity in multiple cancer types, including NSCLC. Prior studies have shown promising results when combining rexinoids with chemotherapy. This phase I/II study evaluates the tolerability and activity of a rexinoid, bexarotene, combined with weekly paclitaxel and monthly carboplatin.

METHODS

Patients with confirmed advanced stage IIIB or IV NSCLC and adequate organ function were enrolled. They were scheduled to receive carboplatin (AUC =6) and 3 doses of weekly paclitaxel (100 mg/m2) every 4 weeks. Oral bexarotene was administered daily at two doses: 300 and 400 mg/m2/day.

RESULTS

Thirty-three patients were enrolled. Fourteen received 300 mg/m2/day and 19 received 400 mg/m2/day of bexarotene. Hematologic toxicity included grade 3 neutropenia in 7 patients. Hyperlipidemia was a major non-hematologic toxicity which was medically managed. The recommended phase II dose of bexarotene was 400 mg/m2/day. Response rate was 35%. Median overall survival (OS) for all patients was 8.3 months with 1-year survival of 43%. Median OS for the 300 mg/m2 dose of bexarotene was 6.6 versus 9.8 months for the 400 mg/m2 dose (HR, 0.73; Log rank P=0.37). Patients who experienced hypertriglyceridemia had a median OS of 9.8 months compared to 4.9 months for those who did not (HR, 0.69; Log rank P=0.33).

CONCLUSIONS

The 43% 1-year survival for patients receiving bexarotene with weekly paclitaxel and monthly carboplatin is encouraging. With the availability of new classes of agents for lung cancer, further evaluation of this regimen in unselected patients is not warranted. Our study confirms prior subgroup analyses showing a significant correlation between bexarotene-induced hypertriglyceridemia and survival. Further research is needed to identify molecular biomarkers to identify this subset of patients and to explore rexinoids in other combinations, especially with immunotherapy.

Novel strategies to prevent the development of multidrug resistance (MDR) in cancer

The development of multidrug resistance (MDR) is one of the major challenges to the success of traditional chemotherapy treatment in cancer patients. Most studies to date have focused on strategies to reverse MDR following its development. However, agents utilizing this approach have proven to be of limited clinical use, failing to demonstrate an improvement in therapeutic efficacy with almost no significant survival benefits observed in cancer clinical trials. An alternative approach that has been applied is to prevent or delay MDR prior or early in its development. Recent investigations have shown that preventing the emergence of MDR at the onset of chemotherapy treatment, rather than reversing MDR once it has developed, may assist in overcoming drug resistance. In this review, we focus on a number of novel strategies used by small-molecule inhibitors to prevent the development of MDR. These agents hold great promise for prolonging the efficacy of chemotherapy treatment and improving the clinical outcomes of patients with cancers that are susceptible to MDR development.

A Way Forward for Cancer Chemoprevention: Think Local

As cells progress through carcinogenesis, the associated exponential expansion of genetic and molecular aberrations and resultant heterogeneity make therapeutic success increasingly unattainable. Therapeutic intervention at early stages of carcinogenesis that occurs within the primary organ and in the face of a lower burden of molecular aberrations, constitutes a basic tenet of cancer chemoprevention, and provides a situation that favors a greater degree of therapeutic efficacy compared with that of advanced cancer. A longstanding barrier to chemoprevention relates to the requirement for essentially no systemic toxicity, and the fact that when large numbers of people are treated, the emergence of systemic toxicity is almost universal. A rational means to address this in fact relates to a second basic tenet of the chemopreventive strategy: the focus of therapeutic intervention is to disrupt a process that is in essence localized to a single organ. Based upon this consideration, a strategy which is based upon local delivery of therapeutics to an at-risk organ will achieve therapeutic efficacy while avoiding systemic delivery and its associated toxicity. This article will review the rationale for undertaking such an approach, describe successful clinical achievements based on this strategy, describe ongoing efforts to expand the impact of this approach, and together will highlight the high impact that this approach has already had on the field as well as its extremely high potential for future impact. Cancer Prev Res; 10(1); 14-35. ©2016 AACR.

Retinoids and rexinoids in cancer prevention: from laboratory to clinic

Early in the age of modern medicine the consequences of vitamin A deficiency drew attention to the fundamental link between retinoid-dependent homeostatic regulation and malignant hyperproliferative diseases. The term "retinoid" includes a handful of endogenous and a large group of synthetic derivatives of vitamin A. These multifunctional lipid-soluble compounds directly regulate target genes of specific biological functions and critical signaling pathways to orchestrate complex functions from vision to development, metabolism, and inflammation. Many of the retinoid activities on the cellular level have been well characterized and translated to the regulation of processes like differentiation and cell death, which play critical roles in the outcome of malignant transformation of tissues. In fact, retinoid-based differentiation therapy of acute promyelocytic leukemia was one of the first successful examples of molecularly targeted treatment strategies. The selectivity, high receptor binding affinity and the ability of retinoids to directly modulate gene expression programs present a distinct pharmacological opportunity for cancer treatment and prevention. However, to fully exploit their potential, the adverse effects of retinoids must be averted. In this review we provide an overview of the biology of retinoid (activated by nuclear retinoic acid receptors [RARs]) and rexinoid (engaged by nuclear retinoid X receptors [RXRs]) action concluded from a long line of preclinical studies, in relation to normal and transformed states of cells. We will also discuss the past and current uses of retinoids in the treatment of malignancies, the potential of rexinoids in the cancer prevention setting, both as single agents and in combinations.

Aldehyde dehydrogenases and cancer stem cells

Aldehyde dehydrogenases (ALDHs), as essential regulators of aldehyde metabolism in the human body, protect organisms from damage induced by active aldehydes. Given their roles in different cancer types, ALDHs have been evaluated as potential prognostic markers of cancer. ALDHs exhibit high activity in cancer stem cells (CSCs) and may serve as markers of CSCs. Moreover, studies indicated that ALDHs and their regulated retinoic acid, reactive oxygen species and reactive aldehydes metabolism were strongly related with various properties of CSCs. Besides, recent research evidences have demonstrated the transcriptional and post-translational regulation of ALDH expression and activation in CSCs. Thus, this review focuses on the function and regulation of ALDHs in CSCs, particularly ALDH1A1 and ALDH1A3.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported.

A transcriptomic network identified in uninfected macrophages responding to inflammation controls intracellular pathogen survival

Intracellular pathogens modulate host cell function to promote their survival. However, in vitro infection studies do not account for the impact of host-derived inflammatory signals. Examining the response of liver-resident macrophages (Kupffer cells) in mice infected with the parasite Leishmania donovani, we identified a transcriptomic network operating in uninfected Kupffer cells exposed to inflammation but absent from Kupffer cells from the same animal that contained intracellular Leishmania. To test the hypothesis that regulated expression of genes within this transcriptomic network might impact parasite survival, we pharmacologically perturbed the activity of retinoid X receptor alpha (RXRα), a key hub within this network, and showed that this intervention enhanced the innate resistance of Kupffer cells to Leishmania infection. Our results illustrate a broadly applicable strategy for understanding the host response to infection in vivo and identify Rxra as the hub of a gene network controlling antileishmanial resistance.

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Leishmania infection rapidly activates infected and uninfected Kupffer cells in mice

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Transcriptomics of inflamed and infected KC uncover distinct and overlapping networks

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A network centered on RXRα is uniquely activated in inflammation-exposed uninfected KCs

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Manipulation of RXRα function leads to a reduction in early parasite burden

Phase I and pharmacokinetic study of bexarotene in combination with gefitinib in the third-line treatment of non-small-cell lung cancer: brief report

Gefitinib (an epidermal growth factor receptor tyrosine kinase inhibitor) and bexarotene (a rexinoid) affect similar oncogenic pathways and are both metabolized through cytochrome P450 CYP3A4. We studied the combination of bexarotene and gefitinib in the third-line treatment of advanced non-small-cell lung cancer to examine pharmacokinetic interactions and establish the maximum tolerated dose. This was a single-institution, nonrandomized, open-label, phase I clinical trial with a standard 3+3 dose escalation. Three patients were enrolled at each dose level on the basis of pharmacokinetic analysis with dose level 1 including gefitinib (Iressa) 250 mg oral daily and bexarotene (Targretin) 400 mg/m oral daily and dose level +1 including gefitinib 500 mg oral daily and bexarotene 400 mg/m oral daily. Patients received gefitinib alone for 2 weeks to allow for steady state and thereafter, bexarotene was added. In dose level 1, two of three patients had undetectable gefitinib levels at day 15 for unknown reasons. However, the peak levels on day 29 for all three patients receiving 250 mg of gefitinib with bexarotene are lower than published peak levels. Among the three patients in dose level +1, ∼40% lower gefitinib plasma concentrations were noted on day 29 compared with day 15 along with a mean 44% reduction in area under the plasma concentration-time curve from 0 to 24 h (AUC0-24). Bexarotene appears to lower the C max and AUC0-24 of gefitinib through cytochrome P450 CYP3A4. Our results have pharmacokinetic implications for ongoing trials that combine bexarotene with other small molecules in the era of personalized cancer therapy.

Molecular pathways: current role and future directions of the retinoic acid pathway in cancer prevention and treatment

Retinoids and their naturally metabolized and synthetic products (e.g., all-trans retinoic acid, 13-cis retinoic acid, bexarotene) induce differentiation in various cell types. Retinoids exert their actions mainly through binding to the nuclear retinoic acid receptors (α, β, γ), which are transcriptional and homeostatic regulators with functions that are often compromised early in neoplastic transformation. The retinoids have been investigated extensively for their use in cancer prevention and treatment. Success has been achieved with their use in the treatment of subtypes of leukemia harboring chromosomal translocations. Promising results have been observed in the breast cancer prevention setting, where fenretinide prevention trials have provided a strong rationale for further investigation in young women at high risk for breast cancer. Ongoing phase III randomized trials investigating retinoids in combination with chemotherapy in non-small cell lung cancer aim to definitively characterize the role of retinoids in this tumor type. The limited treatment success observed to date in the prevention and treatment of solid tumors may relate to the frequent epigenetic silencing of RARβ. Robust evaluation of RARβ and downstream genes may permit optimized use of retinoids in the solid tumor arena.

The effect of bexarotene on atorvastatin pharmacokinetics: results from a phase I trial of bexarotene plus chemotherapy in patients with advanced non-small cell lung cancer

PURPOSE

Bexarotene (Targretin(®) capsules) is a retinoid-X-receptor agonist and an inducer of CYP3A4-mediated metabolism. This phase I trial evaluated the pharmacokinetic (PK) and drug-drug interactions of bexarotene with chemotherapy and a lipid-lowering agent (atorvastatin or fenofibrate). This trial was run in parallel with phase III trials of the combinations to determine whether repeated doses of bexarotene capsules affect the pharmacokinetics (PK) of the chemotherapeutic or the lipid-lowering agents.

METHODS

Patients (n = 48) with advanced non-small cell lung cancer were treated with repetitive cycles of either paclitaxel/carboplatin or cisplatin/vinorelbine chemotherapy, bexarotene (400 mg/m(2)/day) administered continuously starting on day 4 of chemotherapy, and a lipid-lowering drug, either atorvastatin or fenofibrate, starting at least 5 days before chemotherapy due to hypertriglyceridemia induced by bexarotene. Extensive plasma sampling to characterize the PK profiles of the lipid-lowering drugs, relevant chemotherapy agents was performed on day 1 (without bexarotene) and during chemotherapy cycles 2 or 3 (with bexarotene).

RESULTS

Here, we report the drug-drug interactions between the lipid-lowering agents and bexarotene. Mean atorvastatin clearance and dose-corrected AUC values were reduced by nearly 50% with the addition of concomitant bexarotene. As fenofibrate was less effective at controlling hypertriglyceridemia, too few patients received this agent to make any meaningful conclusions about drug-drug interactions.

CONCLUSIONS

A drug-drug interaction was seen in this trial with bexarotene co-administration leading to a significant reduction in the AUC of atorvastatin. The likely mechanism for this interaction is through induction of CYP3A4 by bexarotene given the role of this enzyme in the metabolism of atorvastatin. Knowledge of this interaction is important for optimizing lipid management with atorvastatin for patients receiving bexarotene.

Cancer-preventive rexinoid modulates neutral lipid contents of mammary epithelial cells through a peroxisome proliferator-activated receptor γ-dependent mechanism

Synthetic rexinoids effectively suppress both estrogen receptor-positive and estrogen receptor-negative mammary tumors in animal models, which makes them prime candidates for a novel class of cancer-preventive agents. When used in combination with chemotherapy for non-small-cell lung cancer, the rexinoid bexarotene was most effective for patients who developed hypertriglyceridemia as a side effect. Although serum triglycerides originate from the liver, the effect of bexarotene on lipogenesis in breast epithelial cells is not known. Gene expression studies with normal mammary epithelial cells indicated that rexinoids modulate lipid metabolism, particularly enzymes involved in triglyceride synthesis. High-content analysis revealed dose-dependent accumulation of neutral lipids within adipocyte differentiation-related protein-associated cytoplasmic lipid droplets after long-term bexarotene treatment. Bexarotene also induced mRNA and protein levels for peroxisome proliferator-activated receptor (PPAR) γ, whereas selective knockdown of PPARγ attenuated the induction of both lipid droplets and adipocyte differentiation-related protein. Pharmacological activation of PPARγ, but not PPARα or retinoic acid receptors, effectively induced lipid accumulation. Furthermore, the combination of the PPARγ agonist rosiglitazone with bexarotene synergistically suppressed the growth of human mammary epithelial cells and revealed a strong, nonlinear, inverse correlation of cell growth with lipid droplet accumulation in the cell population. These findings indicate that rexinoids activate a lipogenic program in mammary epithelial cells through a retinoid X receptor/PPARγ-mediated mechanism. It is noteworthy that combining low doses of bexarotene with the PPARγ agonist rosiglitazone provides effective growth suppression of mammary epithelial cells, potentially dissociating systemic adverse effects associated with standard bexarotene treatment from the antiproliferative effects on mammary epithelium.

Bexarotene plus erlotinib suppress lung carcinogenesis independent of KRAS mutations in two clinical trials and transgenic models

The rexinoid bexarotene represses cyclin D1 by causing its proteasomal degradation. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib represses cyclin D1 via different mechanisms. We conducted a preclinical study and 2 clinical/translational trials (a window-of-opportunity and phase II) of bexarotene plus erlotinib. The combination repressed growth and cyclin D1 expression in cyclin-E- and KRAS/p53-driven transgenic lung cancer cells. The window-of-opportunity trial in early-stage non-small-cell lung cancer (NSCLC) patients (10 evaluable), including cases with KRAS mutations, repressed cyclin D1 (in tumor biopsies and buccal swabs) and induced necrosis and inflammatory responses. The phase II trial in heavily pretreated, advanced NSCLC patients (40 evaluable; a median of two prior relapses per patient (range, 0-5); 21% with prior EGFR-inhibitor therapy) produced three major clinical responses in patients with prolonged progression-free survival (583-, 665-, and 1,460-plus days). Median overall survival was 22 weeks. Hypertriglyceridemia was associated with an increased median overall survival (P = 0.001). Early PET (positron emission tomographic) response did not reliably predict clinical response. The combination was generally well tolerated, with toxicities similar to those of the single agents. In conclusion, bexarotene plus erlotinib was active in KRAS-driven lung cancer cells, was biologically active in early-stage mutant KRAS NSCLC, and was clinically active in advanced, chemotherapy-refractory mutant KRAS tumors in this study and previous trials. Additional lung cancer therapy or prevention trials with this oral regimen are warranted.

Vitamin A and retinoid derivatives for lung cancer: a systematic review and meta analysis

BACKGROUND

Despite reported antiproliferative activity of vitamin A and its common use for cancer, there is no comprehensive synthesis of its safety and efficacy in lung cancers. To address this issue we conducted a systematic review of the safety and efficacy of vitamin A for the treatment and prevention of lung cancers.

METHODS AND FINDINGS

Two independent reviewers searched six electronic databases from inception to July 2009 for clinical, observational, and preclinical evidence pertaining to the safety and efficacy of vitamin A and related retinoids for lung cancers. 248 studies were included for full review and analysis. Five RCTs assessed treatment of lung cancers, three assessed primary prevention, and three looked at secondary prevention of lung cancers. Five surrogate studies, 26 phase I/II, 32 observational, and 67 preclinical studies were also included. 107 studies were included for interactions between vitamin A and chemo- or radiation-therapy. Although some studies demonstrated benefits, there was insufficient evidence overall to support the use of vitamin A or related retinoids for the treatment or prevention of lung cancers. Retinyl palmitate combined with beta carotene increased risk of lung cancer in smokers in the large CARET trial. Pooling of three studies pertaining to treatment and three studies on secondary prevention revealed no significant effects on response rate, second primary tumor, recurrence, 5-year survival, and mortality. There was a small improvement in event free survival associated with vitamin A compared to controls, RR 1.24 (95% CI 1.13-1.35). The synthetic rexinoid bexarotene increased survival significantly among a subset of patients in two RCTs (p<0.014, <0.087).

CONCLUSIONS

There is a lack of evidence to support the use of naturally occurring retinoids for the treatment and prevention of lung cancers. The rexinoid bexarotene may hold promise for use among a subset of patients, and deserves further study.

Randomized Phase II Trial of All-Trans-Retinoic Acid With Chemotherapy Based on Paclitaxel and Cisplatin As First-Line Treatment in Patients With Advanced Non–Small-Cell Lung Cancer

Purpose

This randomized phase II trial evaluated whether the combination of cisplatin and paclitaxel (PC) plus all-trans retinoic acid (ATRA) increases response rate (RR) and progression-free survival (PFS) in patients with advanced non–small-cell lung cancer (NSCLC) with an acceptable toxicity profile and its association with the expression of retinoic acid receptor beta 2 (RAR-β2) as a response biomarker.

Patients and Methods

Patients with stages IIIB with pleural effusion and IV NSCLC were included to receive PC, and randomly assigned to receive ATRA 20 mg/m2/d (RA/PC) or placebo (P/PC) 1 week before treatment until two cycles were completed. RAR-β2 expression was analyzed in tumor and adjacent lung tissue.

Results

One hundred seven patients were included, 55 in the P/PC group and 52 in the RA/PC group. RR for RA/PC was 55.8% (95% CI, 46.6% to 64.9%) and for P/PC, 25.4% (95% CI, 21.3 to 29.5%; P = .001). The RA/PC group had a longer median PFS (8.9 v 6.0 months; P = .008). Multivariate analysis of PFS showed significant differences for the RA/PC group (hazard ratio, 0.62; 95% CI, 0.4 to 0.95). No significant differences in toxicity grade 3/4 were found between groups, except for hypertriglyceridemia (10% v 0%) in RA/PC (P = .05). Immunohistochemistry and reverse-transcriptase polymerase chain reaction assays showed expression of RAR-β2 in normal tissues of all tumor samples, but only 10% of samples in the tumor tissue.

Conclusion

Adding ATRA to chemotherapy could increase RR and PFS in patients with advanced NSCLC with an acceptable toxicity profile. A phase III clinical trial is warranted to confirm these findings.

Phase III study of carboplatin and paclitaxel alone or with sorafenib in advanced non-small-cell lung cancer

PURPOSE This phase III, multicenter, randomized, placebo-controlled trial assessed the efficacy and safety of sorafenib, an oral multikinase inhibitor, in combination with carboplatin and paclitaxel in chemotherapy-naïve patients with unresectable stage IIIB or IV non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS Nine hundred twenty-six patients were randomly assigned to receive up to six 21-day cycles of carboplatin area under the curve 6 and paclitaxel 200 mg/m(2) (CP) on day 1, followed by either sorafenib 400 mg twice a day (n = 464, arm A) or placebo (n = 462, arm B) on days 2 to 19. The maintenance phase after CP consisted of sorafenib 400 mg or placebo twice a day. The primary end point was overall survival (OS); secondary end points included progression-free survival and tumor response. RESULTS Overall demographics were balanced between arms; 223 patients (24%) had squamous cell histology. On the basis of a planned interim analysis, median OS was 10.7 months in arm A and 10.6 months in arm B (hazard ratio [HR] = 1.15; 95% CI, 0.94 to 1.41; P = .915). The study was terminated after the interim analysis concluded that the study was highly unlikely to meet its primary end point. A prespecified exploratory analysis revealed that patients with squamous cell histology had greater mortality in arm A than in arm B (HR = 1.85; 95% CI, 1.22 to 2.81). Main grade 3 or 4 sorafenib-related toxicities included rash (8.4%), hand-foot skin reaction (7.8%), and diarrhea (3.5%). CONCLUSION No clinical benefit was observed from adding sorafenib to CP chemotherapy as first-line treatment for NSCLC.

Recent development of molecular-targeted drugs in lung cancer

Numerous molecular target drugs have been introduced for the treatment of advanced malignancies. In the treatment of lung cancer, epidermoid growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) demonstrate striking antitumor activity in selected EGFR mutation positive patients. Patient selection by biomarker is extremely important to obtain successful results. The anti-vascular endothelial growth factor (VEGF) antibody, bevacizumab, shows a markedly increased response rate, progression free survival of advanced non-squamous cell lung cancer when combined with cytotoxic drugs. The classification of lung cancer is rapidly changing based on the advances in molecular biology. Here, the recent development of new molecular target drugs against lung cancer is thoroughly reviewed in addition to EGFR-TKIs and bevacizumab with special emphasis on the clinical application.

Drugs that suppress TSH or cause central hypothyroidism

Many different drugs affect thyroid function. Most of these drugs act at the level of the thyroid in patients with normal thyroid function, or at the level of thyroid hormone absorption or metabolism in patients requiring exogenous levothyroxine. A small subset of medications including glucocorticoids, dopamine agonists, somatostatin analogues and rexinoids affect thyroid function through suppression of TSH in the thyrotrope or hypothalamus. Fortunately, most of these medications do not cause clinically evident central hypothyroidism. A newer class of nuclear hormone receptors agonists, called rexinoids, cause clinically significant central hypothyroidism in most patients and dopamine agonists may exacerbate 'hypothyroidism' in patients with non-thyroidal illness. In this review, we explore mechanisms governing TSH suppression of these drugs and the clinical relevance of these effects.

The rexinoid LG100268 and the synthetic triterpenoid CDDO-methyl amide are more potent than erlotinib for prevention of mouse lung carcinogenesis

Female A/J mice injected with the carcinogen vinyl carbamate develop atypical adenomatous hyperplasias in lungs 4 weeks after injection with the carcinogen. The number and severity of tumors then increase over time, making these mice a useful model for evaluating potential chemopreventive agents. The rexinoid LG100268 (LG268), a selective ligand for the retinoid X receptor, and the methyl amide of the synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) both significantly reduced the number, size, and severity of the histopathology of lung tumors in female A/J mice when fed in diet for 14 to 20 weeks. The total tumor burden was 85% to 87% lower in mice fed LG268 and CDDO-MA than in controls, and the percentage of high-grade tumors decreased from 59% in the controls to 25% or 30% with CDDO-MA and LG268. Erlotinib, which is used to treat lung cancer patients and is an inhibitor of the epidermal growth factor receptor, was less effective in this model. Immunohistochemical staining of geminin, a marker of cell cycle progression, was higher in lung sections from control mice than in mice treated with LG268. Because rexinoids and triterpenoids signal through different biological pathways, they should be tested in combination for the prevention of lung cancer.

Randomized phase III trial comparing bexarotene (L1069-49)/cisplatin/vinorelbine with cisplatin/vinorelbine in chemotherapy-naive patients with advanced or metastatic non-small-cell lung cancer: SPIRIT I

PURPOSE

This study evaluated whether the combination of the synthetic rexinoid bexarotene with first-line cisplatin/vinorelbine therapy provides additional survival benefit in patients with advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients with stage IIIB with pleural effusion or stage IV NSCLC and Eastern Cooperative Oncology Group performance status 0 to 1 were randomly assigned to open-label bexarotene 400 mg/m(2)/d with cisplatin/vinorelbine or to cisplatin/vinorelbine alone. Antilipid agents were initiated on or before day 1 in the bexarotene arm. Primary efficacy end point was overall survival. Primary, secondary and supportive efficacy analyses were conducted.

RESULTS

A total of 623 patients (312 control, 311 bexarotene) were enrolled. Overall, no significant difference in survival occurred between the two treatment groups. However, an unplanned retrospective analysis showed that a subpopulation of bexarotene patients (n = 98 of 306) who experienced National Cancer Institute grade 3/4 hypertriglyceridemia had longer median survival compared with control patients (12.3 v 9.9 months; log-rank P = .08). Within that subgroup, those who benefited the most included males, smokers, those with stage IV disease, and those with a 6-month prior weight loss of 5% or more. Incidence, type and severity of grade 3/4 adverse events were comparable between arms, except for leukopenia (higher in chemotherapy arm) and hyperlipemia, hypothyroidism, dyspnea, and headache (higher in chemotherapy/bexarotene arm).

CONCLUSION

The addition of bexarotene to first-line chemotherapy did not increase survival in patients with advanced NSCLC. However, a subgroup (32%) of bexarotene-treated patients developing high-grade hypertriglyceridemia appeared to have better survival (12.3 months) than controls; thus triglyceride response may be a biomarker of survival benefit with bexarotene.

Phase III Trial Comparing Carboplatin, Paclitaxel, and Bexarotene With Carboplatin and Paclitaxel in Chemotherapy-Naïve Patients With Advanced or Metastatic Non–Small-Cell Lung Cancer: SPIRIT II

Purpose

The purpose of this study was to determine whether addition of the synthetic rexinoid bexarotene (Targretin; Eisai Inc, Woodcliff Lake, NJ) to standard first-line carboplatin and paclitaxel therapy provides additional survival benefit in patients with advanced non–small-cell lung cancer (NSCLC).

Patients and Methods

Patients with stage IIIB disease with pleural effusion, or stage IV NSCLC and Eastern Cooperative Oncology Group performance status 0 to 1, were randomly assigned to bexarotene 400 mg/m2/d combined with carboplatin and paclitaxel, or assigned to carboplatin and paclitaxel alone. Bexarotene patients also received lipid-lowering agents on or before day 1. The primary efficacy end point was overall survival; secondary efficacy and supportive analyses were also conducted.

Results

A total of 612 patients (306 per arm) were enrolled onto the study. In the intent-to-treat population, no significant difference in survival occurred between the two arms. However, a subpopulation (approximately 40%) of bexarotene-treated patients who experienced National Cancer Institute grade 3/4 hypertriglyceridemia had significantly longer median survival than control patients (12.4 v 9.2 months; log-rank, P = .014). Bexarotene-treated patients with grade 3/4 hypertriglyceridemia who received the most benefit included those who were male, were smokers, experienced 6-month prior weight loss ≥ 5%, and had stage IV disease. The incidence and severity of most adverse events were similar between arms, although hyperlipidemia, neutropenia, fatigue, leukopenia, arthralgia, and diarrhea were more frequent in the bexarotene arm.

Conclusion

Although the addition of bexarotene to chemotherapy did not improve survival in the overall study population, occurrence of high-grade hypertriglyceridemia in bexarotene-treated patients strongly correlated with increased survival, suggesting that bexarotene may benefit a segment of first-line NSCLC patients.

Modulation by bexarotene of mRNA expression of genes in mouse lung tumors

Bexarotene has demonstrated chemopreventive and therapeutic efficacy towards mouse lung tumors. Using specimens from our published study that demonstrated the efficacy of bexarotene, we report herein its ability to modulate mRNA expression of genes in both lung and lung tumors. Strain A/J mice were administered vinyl carbamate to induce lung tumors. This was followed by 200 mg/kg body weight of bexarotene administered by oral gavage during Wks 4-25 or 23-25. The mice were sacrificed at Wk 25. The expression of 26 genes was decreased in lung tumors, whereas only two genes, Apolipoprotein D and CYP26b, had their mRNA expression increased by bexarotene. Genes with increased mRNA expression in untreated lung tumors include: epiregulin and kininogen-1 (increased by more than 40-fold) and Caspase-3, Cyclin D1, DNA methyltransferase 3a (Dnmt-3a), E-prostanoid 3 receptor (EP3), c-myc, surfactant protein-C, and survivin (increased by 1.7- to 3.6-fold). Bexarotene decreased the mRNA expression of Caspase-3, Dnmt-3a, EP3, and survivin, as well as the expression of the Cyclin E1, estrogen receptor-alpha, and iNOS genes. Bexarotene had a greater effect in decreasing the expression of Caspase-3, Cyclin E1, Dnmt-3a, EP3, iNOS, and survivin, when administered to mice with established tumors than when administered to mice while tumors were emerging. In summary, bexarotene modulated mRNA expression of genes in mouse lung tumors, being more effective in established tumors than in emerging tumors, suggesting that modulation of expression could be useful as a biomarker for the therapeutic and chemopreventive activity of the drug, especially in established tumors.

Bexarotene as add-on to antipsychotic treatment in schizophrenia patients: a pilot open-label trial

OBJECTIVES

Bexarotene is a synthetic retinoid used for treatment of neoplastic or dermatologic disorders. Based on the retinoid dysregulation hypothesis, it was hypothesized that bexarotene augmentation would have a beneficial effect in the antipsychotic treatment of schizophrenia patients. This study is the first to investigate the safety and efficacy of add-on oral bexarotene to ongoing antipsychotic treatment in chronic schizophrenia patients who were stabilized on regular antipsychotic treatment.

METHODS

A 6-week open label trial was conducted in 2 mental health centers from October 2005 to October 2006. Twenty-five patients with chronic schizophrenia received a low dose of bexarotene (75 mg/d) augmentation. Mental condition and laboratory tests were assessed at baseline and after weeks 2, 4, and 6 of the study. The primary outcome measure was change from baseline in 4 symptom scales: the Positive and Negative Symptom Scale, Extrapyramidal Symptom Rating Scale, Abnormal Involuntary Movement Scale, and Barnes Akathisia Scale. Blood cell count, liver and thyroid functions, cholesterol, and triglyceride rates were followed.

RESULTS

Significant improvement from baseline to endpoint was observed on total Positive and Negative Symptom Scale score (P = 0.022), general psychopathology (P = 0.024), positive (P = 0.012), and the dysphoric mood (P = 0.028) factor scores. Furthermore, a trend to a diminishing Extrapyramidal Symptom Rating Scale score (P = 0.053) was found. Bexarotene was found to be a safe medication as measured by all laboratory parameters with the exception of increased total cholesterol serum level.

CONCLUSIONS

This short-term pilot study supports bexarotene as a potential valuable adjunct in management of schizophrenia. Low doses of bexarotene were well tolerated. A double-blind controlled study should be performed to replicate these preliminary positive results.

A new rexinoid, NRX194204, prevents carcinogenesis in both the lung and mammary gland

PURPOSE

We evaluated the anti-inflammatory and growth-inhibitory properties of the novel rexinoid NRX194204 (4204) in vitro and then tested its ability to prevent and/or treat experimental lung and estrogen receptor (ER)-negative breast cancer in vivo.

EXPERIMENTAL DESIGN

In cell culture studies, we measured the ability of 4204 to block the effects of lipopolysaccharide and induce apoptosis. For the lung cancer prevention studies, A/J mice were injected with the carcinogen vinyl carbamate and then fed 4204 (30-60 mg/kg diet) for 15 weeks, beginning 1 week after the administration of the carcinogen. For breast cancer prevention studies, mouse mammary tumor virus-neu mice were fed control diet or 4204 (20 mg/kg diet) for 50 weeks; for treatment, tumors at least 32 mm3 in size were allowed to form, and then mice were fed control diet or 4204 (60 mg/kg diet) for 4 weeks.

RESULTS

Low nanomolar concentrations of 4204 blocked the ability of lipopolysaccharide and tumor necrosis factor-alpha to induce the release of nitric oxide and interleukin 6 and the degradation of IKBalpha in RAW264.7 macrophage-like cells. In the A/J mouse model of lung cancer, 4204 significantly (P < 0.05) reduced the number and size of tumors on the surface of the lungs and reduced the total tumor volume per slide by 64% to 81% compared with the control group. In mouse mammary tumor virus-neu mice, 4204 not only delayed the development of ER-negative mammary tumors in the prevention studies but also caused marked tumor regression (92%) or growth arrest (8%) in all of the mammary tumors when used therapeutically.

CONCLUSIONS

The combined anti-inflammatory and anticarcinogenic actions of 4204 suggest that it is a promising new rexinoid that should be considered for future clinical trials.

New targets for non-small-cell lung cancer therapy

Lung cancer remains the leading cause of malignancy-related deaths in the USA, regardless of advances in therapeutic agents. Non-small-cell lung cancer demonstrates great molecular heterogeneity in which several pathways are simultaneously active leading to tumorigenesis. Novel agents targeting specific pathways associated with apoptosis, cell proliferation, angiogenesis and other mechanisms have emerged as a separate and unique therapeutic class delivering promising results in a vast number of malignancies. This innovative class of agents has been studied in advanced-stage non-small-cell lung cancer and, although some agents have demonstrated a clinical benefit, the overall course of the disease remains relatively unchanged, still holding a poor overall prognosis. Most of these agents have been shown to be 'cytostatic', inducing more stable disease rather than objective responses. Thus, the entrance of these novel agents into our drug armamentarium seems to be more attractive in combination with conventional chemotherapy agents based on additive or synergistic response seen with this combined approach. Herein, we review the most relevant clinical data using these novel targeted agents either alone or in combination with chemotherapy in non-small-cell lung cancer.

p21WAF1/CIP1 is a common transcriptional target of retinoid receptors: pleiotropic regulatory mechanism through retinoic acid receptor (RAR)/retinoid X receptor (RXR) heterodimer and RXR/RXR homodimer

The divergent response and the molecular mechanisms underlying the anti-cancer effects of retinoid X receptor (RXR) ligand (rexinoid) therapy are poorly understood. This study demonstrates that ligand-activated RXR homodimer facilitated G(1) arrest by up-regulation of p21 in vitro and in vivo but failed to induce G(1) arrest when p21 expression was blocked by p21 small interfering RNA. RXR ligand-dependent p21 up-regulation was transcriptionally controlled through the direct binding of RXR homodimers to two consecutive retinoid X response elements in the p21 promoter. Structural overlap of a retinoic acid response element with these retinoid X response elements led to a high affinity binding of retinoic acid receptor/RXR heterodimer to the retinoic acid response element, resulting in the prevention of RXR ligand-mediated p21 transactivation. These data show that p21 is a potential and novel molecular target for RXR ligand-mediated anti-cancer therapy and that the expression level of retinoic acid receptor and RXR in tumors may be crucial to induce p21-mediated cell growth arrest in RXR ligand therapy.

Triterpenoids and rexinoids as multifunctional agents for the prevention and treatment of cancer

Synthetic oleanane triterpenoids and rexinoids are two new classes of multifunctional drugs. They are neither conventional cytotoxic agents, nor are they monofunctional drugs that uniquely target single steps in signal transduction pathways. Synthetic oleanane triterpenoids have profound effects on inflammation and the redox state of cells and tissues, as well as being potent anti-proliferative and pro-apoptotic agents. Rexinoids are ligands for the nuclear receptor transcription factors known as retinoid X receptors. Both classes of agents can prevent and treat cancer in experimental animals. These drugs have unique molecular and cellular mechanisms of action and might prove to be synergistic with standard anti-cancer treatments.

A Proof-of-Principle Clinical Trial of Bexarotene in Patients with Non–Small Cell Lung Cancer

PURPOSE

Bexarotene is a rexinoid (selective retinoid X receptor agonist) that affects proliferation, differentiation, and apoptosis in preclinical studies. The relationship between bexarotene levels and biomarker changes in tumor tissues has not been previously studied.

EXPERIMENTAL DESIGN

BEAS-2B human bronchial epithelial (HBE) cells, retinoid-resistant BEAS-2B-R1 cells, A427, H226, and H358 lung cancer cells were treated with bexarotene. Proliferation and biomarker expression were assessed. In a proof-of-principle clinical trial, bexarotene tumor tissue levels and intratumoral pharmacodynamic effects were assessed in patients with stages I to II non-small cell lung cancer. Bexarotene (300 mg/m(2)/day) was administered p.o. for 7 to 9 days before resection.

RESULTS

Bexarotene-induced dosage-dependent repression of growth, cyclin D1, cyclin D3, total epidermal growth factor receptor (EGFR), and phospho-EGFR expression in BEAS-2B, BEAS-2B-R1, A427, and H358, but not H226 cells. Twelve patients were enrolled, and 10 were evaluable. Bexarotene treatment was well tolerated. There was nonlinear correlation between plasma and tumor bexarotene concentrations (r(2) = 0.77). Biomarker changes in tumors were observed: repression of cyclin D1, total EGFR and proliferation in one case; repression of cyclin D3, total and phospho-EGFR in another. The cases with multiple biomarker changes had high tumor bexarotene (107-159 ng/g). A single biomarker change was detected in one case with low tumor bexarotene.

CONCLUSION

Bexarotene represses proliferation and biomarker expression in responsive, but not resistant HBE and lung cancer cells. Similar biomarker changes occur in lung tumors when therapeutic intratumoral bexarotene levels are achieved. This proof-of-principle trial approach is useful to uncover pharmacodynamic mechanisms in vivo and relate these to intratumoral pharmacokinetic effects.

Single-dose rexinoid rapidly and specifically suppresses serum thyrotropin in normal subjects

CONTEXT

Retinoid X receptor agonists (rexinoids) have demonstrated benefit in patients with certain malignancies but appear to cause central hypothyroidism in some patients with advanced cancer. The influence of rexinoids on thyroid function in healthy subjects is not clear.

OBJECTIVE

The objective of this study was to determine the effect of a single dose of bexarotene on levels of TSH, T4, and T3 in healthy subjects.

DESIGN

This study was a randomized, double-blind, placebo-controlled, crossover trial.

SETTING

This study was conducted at the General Clinical Research Center (University of Colorado Health Sciences Center, Aurora, CO).

SUBJECTS

Six healthy adults (>18 yr old) were studied.

INTERVENTION

Single-dose rexinoid (bexarotene, 400 mg/m2) or placebo, with TSH measurements at 0, 1, 2, 4, 8, 12, 24, and 48 h, were used.

MAIN OUTCOME MEASURE

The main outcome was the serum TSH level at 24 h.

RESULTS

Single-dose bexarotene suppressed serum TSH (P < 0.001) over time. Compared with placebo, levels of TSH were significantly lower by 12 h (P = 0.043); the nadir of 0.32 +/- 0.02 mU/liter (P < 0.001) was seen at 24 h. Free T4 index and free T3 index were also significantly lower than placebo over time (48 h) (P = 0.029; P = 0.004, respectively). Serum prolactin, cortisol, and triglycerides were not affected (P > 0.05 for all). There was no significant effect of single-dose bexarotene on rT3 or T3/rT3 ratio at 24 h.

CONCLUSION

A single dose of a rexinoid can rapidly and specifically suppress serum TSH levels in healthy subjects. These data provide insight into the mechanisms by which rexinoids cause central hypothyroidism and potential ways this effect can be used for treatment of disorders such as thyroid hormone resistance and TSH-secreting pituitary tumors.

Phase II Trial of Bexarotene Capsules in Patients With Advanced Non–Small-Cell Lung Cancer After Failure of Two or More Previous Therapies

Purpose

To evaluate the effect of bexarotene on survival in patients with relapsed non–small-cell lung cancer (NSCLC).

Patients and Methods

Patients with stage IIIB NSCLC with pleural effusion or stage IV NSCLC, who had Eastern Cooperative Oncology Group performance status 0 to 2, and were previously treated with ≥ two different regimens that must have included a platinum and a taxane, received oral bexarotene 400 mg/m2/d plus concomitant levothyroxine and a lipid-lowering agent. Primary efficacy end point was survival.

Results

For the 146 assessable patients treated with bexarotene, median age was 66 years (range, 34 to 87 years), 51% were men, and the median number of prior regimens was three (range, one to seven). The overall median survival was 5 months (95% CI, 4 to 7 months) and the 1-year survival was 23% (95% CI, 16% to 31%). Survival was significantly longer in patients with bexarotene-induced hypertriglyceridemia and/or skin rash. In 26 patients who had both adverse effects, the median and 1-year survival rates were 12 months (95% CI, 8 to 15 months) and 48%, respectively. In 40 patients who had neither adverse effect, median and 1-year survival rates were 2 months (95% CI, 2 to 5 months) and 15%, respectively (P = .0002). Twenty patients (14%) discontinued therapy because of bexarotene-related toxicity. For the remaining patients, adverse reactions to bexarotene were generally mild to moderate.

Conclusion

In the intent-to-treat population, bexarotene given as third or subsequent line of therapy for relapsed NSCLC did not achieve the intended median survival of 6 months. Survival may have been extended in patients who developed bexarotene-induced hypertriglyceremia and/or skin rash. It is important to confirm these observations in a randomized controlled trial.

Targeted therapy in advanced non-small cell lung cancer (NSCLC): where do we stand?

Cytotoxic chemotherapy has helped improve the outcomes in patients with advanced non-small cell lung cancer (NSCLC), but we seem to have reached a plateau with respect to the benefit obtained. Also, a large subset of elderly patients and those with a poor performance status cannot tolerate these drugs at recommended doses. There is a growing need to incorporate newer drugs with different mechanisms of action and better safety profile. The epidermal growth factor receptor family (EGFR) and vascular endothelial growth factor (VEGF) have been identified as potential targets and agents acting specifically against these targets have been developed with the hope of improving outcomes. Although recent data with the small molecule EGFR tyrosine kinase inhibitors have been disappointing, there have been instances of dramatic responses thereby raising questions about the ideal patient to whom these drugs should be administered. Cetuximab, the anti-EGFR antibody has shown promising results. Bevacizumab, the anti-VEGF antibody was the first drug to demonstrate a survival benefit in first line treatment when added to chemotherapy. This review will briefly discuss the important trials using these targeted agents in advanced NSCLC.

Current approaches to advanced-stage non-small-cell lung cancer: first-line therapy in patients with a good functional status

Lung cancer is the leading cause of cancer-related death among men and women in the United States. Approximately 80-85% of lung cancer cases are non-small-cell lung cancer (NSCLC), and approximately 65% of these patients have advanced-stage (IIIB/IV) disease at diagnosis. The median survival for patients with advanced-stage NSCLC treated with platinum-based chemotherapy is a disappointing 8-10 months. This article reviews the current status of chemotherapy in patients with a good functional status and evaluates the treatments in terms of efficacy, toxicity, survival, and impact on quality of life in the first-line treatment. Biologic agents such as bevacizumab and erlotinib have been investigated in phase III trials in the first- and second-line setting. These agents could play a role in select patient populations. This article also highlights some of the more promising new strategies, such as advances in pharmacogenomics and immune-based therapy. There is a clear need for improvement in the current standard of care. Well-designed clinical trials with appropriate patient selection, as well as continued efforts in translational research and pharmacogenomics, are crucial for progress in this disease.