Phase I clinical and pharmacokinetic study of E7070, a novel sulfonamide given as a 5-day continuous infusion repeated every 3 weeks in patients with solid tumours. A study by the EORTC Early Clinical Study Group (ECSG)

Chasing molecular glue degraders: screening approaches

Protein-protein interactions (PPIs) govern all biological processes. Some small molecules modulate PPIs through induced protein proximity. In particular, molecular glue degraders are monovalent compounds that orchestrate interactions between a target protein and an E3 ubiquitin ligase, prompting the proteasomal degradation of the former. This and other pharmacological strategies of targeted protein degradation (e.g. proteolysis-targeting chimeras - PROTACs) overcome some limitations of traditional occupancy-based therapeutics. Here, we provide an overview of the "molecular glue" concept, with a special focus on natural and synthetic inducers of proximity to E3s. We then briefly highlight the serendipitous discoveries of some clinical and preclinical molecular glue degraders, and discuss the first examples of intentional discoveries. Specifically, we outline the different screening strategies reported in this rapidly evolving arena and our thoughts on future perspectives. By mastering the ability to influence PPIs, molecular glue degraders can induce the degradation of unligandable proteins, thus providing an exciting path forward to broaden the targetable proteome.

Genetic and compound screens uncover factors modulating cancer cell response to indisulam

The authors identify that loss of SRPK1 sensitises cancer cells to indisulam treatment and loss of CAND1 confers resistance. Resistance is mediated through RBM39. Furthermore, pharmacological Bcl-xL inhibition prevents acquired resistance to indisulam.

Discovering biomarkers of drug response and finding powerful drug combinations can support the reuse of previously abandoned cancer drugs in the clinic. Indisulam is an abandoned drug that acts as a molecular glue, inducing degradation of splicing factor RBM39 through interaction with CRL4^DCAF15. Here, we performed genetic and compound screens to uncover factors mediating indisulam sensitivity and resistance. First, a dropout CRISPR screen identified SRPK1 loss as a synthetic lethal interaction with indisulam that can be exploited therapeutically by the SRPK1 inhibitor SPHINX31. Moreover, a CRISPR resistance screen identified components of the degradation complex that mediate resistance to indisulam: DCAF15, DDA1, and CAND1. Last, we show that cancer cells readily acquire spontaneous resistance to indisulam. Upon acquiring indisulam resistance, pancreatic cancer (Panc10.05) cells still degrade RBM39 and are vulnerable to BCL-xL inhibition. The better understanding of the factors that influence the response to indisulam can assist rational reuse of this drug in the clinic.

Indisulam targets RNA splicing and metabolism to serve as a therapeutic strategy for high-risk neuroblastoma

Neuroblastoma is the most common paediatric solid tumour and prognosis remains poor for high-risk cases despite the use of multimodal treatment. Analysis of public drug sensitivity data showed neuroblastoma lines to be sensitive to indisulam, a molecular glue that selectively targets RNA splicing factor RBM39 for proteosomal degradation via DCAF15-E3-ubiquitin ligase. In neuroblastoma models, indisulam induces rapid loss of RBM39, accumulation of splicing errors and growth inhibition in a DCAF15-dependent manner. Integrative analysis of RNAseq and proteomics data highlight a distinct disruption to cell cycle and metabolism. Metabolic profiling demonstrates metabolome perturbations and mitochondrial dysfunction resulting from indisulam. Complete tumour regression without relapse was observed in both xenograft and the Th-MYCN transgenic model of neuroblastoma after indisulam treatment, with RBM39 loss, RNA splicing and metabolic changes confirmed in vivo. Our data show that dual-targeting of metabolism and RNA splicing with anticancer indisulam is a promising therapeutic approach for high-risk neuroblastoma.

Anti-proliferative effects of the combination of Sulfamethoxazole and Quercetin via caspase3 and NFkB gene regulation: an in vitro and in vivo study

Combination therapy comprising natural polyphenols and anticancer drugs has been used to decrease the adverse effects and increase the effectiveness and antioxidant activities of the drugs. The antioxidant and anticancer effects of quercetin (Q), a nutritive polyphenol, have been observed both in vitro and in vivo. Likewise, the anticancer activity of sulfamethoxazole (S) has been demonstrated in vitro and in vivo. This study aimed to investigate the in vitro and in vivo anticancer effects of Q alone and in combination with S. The in vitro effects of S, Q, and S + Q on HCT-116, HepG2, MCF-7, and PC3 cell lines were examined. Additionally, the in vivo effects of these drugs were evaluated using Ehrlich ascites carcinoma (EAC) tumor-bearing mice. The in vitro data revealed the potent anticancer activity of S + Q through the induction of apoptosis and cell cycle arrest. The EAC-inoculated mice treated with S + Q presented with elevated SOD, GSH, CAT, and TAC levels and decreased malondialdehyde levels compared with the untreated EAC group, thus revealing the antioxidant and protective actions of S + Q against EAC cell invasion. Furthermore, the downregulation of NFkB and upregulation of the caspase3 gene in the EAC-inoculated mice treated with the S + Q indicated the induction of the apoptotic pathway and decrease in both cell proliferation and metastasis. In conclusion, the combination of S and Q might exert anticancer effects by inducing apoptosis and exhibiting selective toxicity against the cancer cells and thereby protecting the vital organs.

RNA-binding motif protein 39 (RBM39): An emerging cancer target

RNA-binding motif protein 39 (RBM39) is an RNA-binding protein involved in transcriptional co-regulation and alternative RNA splicing. Recent studies have revealed that RBM39 is the unexpected target of aryl sulphonamides, which act as molecular glues between RBM39 and the DCAF15-associated E3 ubiquitin ligase complex leading to selective degradation of the target. Loss of RBM39 leads to aberrant splicing events and differential gene expression, thereby inhibiting cell cycle progression and causing tumour regression in a number of preclinical models. Many clinical studies have shown that aryl sulphonamides were well tolerated, but their clinical performance was limited due to an insufficient understanding of the target, RBM39 biology and a lack of predictive biomarkers. This review summarises the current knowledge of RBM39 function and discusses the therapeutic potential of this spliceosome target in cancer therapy.

Mutations in spliceosome genes and therapeutic opportunities in myeloid malignancies

Since the discovery of RNA splicing more than 40 years ago, our comprehension of the molecular events orchestrating constitutive and alternative splicing has greatly improved. Dysregulation of pre-mRNA splicing has been observed in many human diseases including neurodegenerative diseases and cancer. The recent identification of frequent somatic mutations in core components of the spliceosome in myeloid malignancies and functional analysis using model systems has advanced our knowledge of how splicing alterations contribute to disease pathogenesis. In this review, we summarize our current understanding on the mechanisms of how mutant splicing factors impact splicing and the resulting functional and pathophysiological consequences. We also review recent advances to develop novel therapeutic approaches targeting splicing catalysis and splicing regulatory proteins, and discuss emerging technologies using oligonucleotide-based therapies to modulate pathogenically spliced isoforms.

Targeting splicing abnormalities in cancer

Recently splicing has been recognized as a key pathway in cancer. Although aberrant splicing has been shown to be a consequence of mutations or the abnormal expression of splicing factors (trans-effect changes) or mutations in the splicing sequences (cis-effect mutations), the connections between aberrant splicing and cancer initiation or progression are still not well understood. Here we review the mutational landscape of splicing factors in cancer and associated splicing consequences, along with the most important examples of the therapeutic approaches targeting the spliceosome currently being investigated in oncology.

Therapeutic targeting of RNA splicing in myelodysplasia

Genomic analysis of patients with myelodysplastic syndromes (MDS) has identified that mutations within genes encoding RNA splicing factors represent the most common class of genetic alterations in MDS. These mutations primarily affect SF3B1, SRSF2, U2AF1, and ZRSR2. Current data suggest that these mutations perturb RNA splicing catalysis in a manner distinct from loss of function but how exactly the global changes in RNA splicing imparted by these mutations result in MDS is not well delineated. At the same time, cells bearing mutations in RNA splicing factors are exquisitely dependent on the presence of the remaining wild-type (WT) allele to maintain residual normal splicing for cell survival. The high frequency of these mutations in MDS, combined with their mutual exclusivity and noteworthy dependence on the WT allele, make targeting RNA splicing attractive in MDS. To this end, two promising therapeutic approaches targeting RNA splicing are being tested clinically currently. These include molecules targeting core RNA splicing catalysis by interfering with the ability of the SF3b complex to interact with RNA, as well as molecules degrading the auxiliary RNA splicing factor RBM39. The preclinical and clinical evaluation of these compounds are discussed here in addition to their potential as therapies for spliceosomal mutant MDS.

In silico study of porphyrin-anthraquinone hybrids as CDK2 inhibitor

Cyclin-Dependent Kinases (CDKs) are known to play crucial roles in controlling cell cycle progression of eukaryotic cell and inhibition of their activity has long been considered as potential strategy in anti-cancer drug research. In the present work, a series of porphyrin-anthraquinone hybrids bearing meso-substituents, i.e. either pyridine or pyrazole rings were designed and computationally evaluated for their Cyclin Dependent Kinase-2 (CDK2) inhibitory activity using molecular docking, molecular dynamics simulation, and binding free energy calculation. The molecular docking simulation revealed that all six porphyrin hybrids were able to bind to ATP-binding site of CDK2 and interacted with key residues constituted the active cavity of CDK2, while molecular dynamics simulation indicated that all porphyrins bound to CDK2 were stable for 6ns. The binding free energies predicted by MM-PBSA method showed that most compounds exhibited higher affinity than that of native ligand (4-anilinoquinazoline, DTQ) and the affinity of mono-H₂PyP-AQ was about three times better than that of DTQ, indicating its potential to be advanced as a new CDK2 inhibitor.

Cell cycle inhibitors for the treatment of NSCLC

INTRODUCTION

Lung cancer remains to be the leading cause of cancer-related death worldwide. Treatment of lung cancer still poses a significant challenge. Cell cycle is a tightly integrated process and is frequently aberrant in lung cancer. Cell cycle inhibitors have emerged as novel therapeutics, in anticipation of overcoming the unrestricted cell division and growth in lung cancer.

AREAS COVERED

In this article, we first address the potential roles of cell cycle proteins and cell cycle deregulation in the development of lung cancer. The review then provides an overview for several major categories of cell cycle inhibitors with particular attention to their tolerability and disease control in early phases of lung cancer trials.

EXPERT OPINION

Targeted agents against different components of cell cycle regulation, such as cyclin-dependent kinase, polo-like kinase, checkpoint kinase and aurora kinase, are currently in clinical development for lung cancer management. Their clinical benefits remain to be defined. When evaluated as single agents in lung cancer, cell cycle inhibitors are often associated with limited clinical activity and tolerable toxicities. The key challenges in the drug development are to understand resistance mechanisms and to identify predictive biomarkers that can potentially guide patient selection and optimize the utility of these targeted inhibitors.

DNA repair and cell cycle checkpoint defects as drivers and therapeutic targets in melanoma

The ultraviolet radiation (UVR) component of sunlight is the major environmental risk factor for melanoma, producing DNA lesions that can be mutagenic if not repaired. The high level of mutations in melanomas that have the signature of UVR-induced damage indicates that the normal mechanisms that detect and repair this damage must be defective in this system. With the exception of melanoma-prone heritable syndromes which have mutations of repair genes, there is little evidence for somatic mutation of known repair genes. Cell cycle checkpoint controls are tightly associated with repair mechanisms, arresting cells to allow for repair before continuing through the cell cycle. Checkpoint signaling components also regulate the repair mechanisms. Defects in checkpoint mechanisms have been identified in melanomas and are likely to be responsible for increased mutation load in melanoma. Loss of the checkpoint responses may also provide an opportunity to target melanomas using a synthetic lethal approach to identify and inhibit mechanisms that compensate for the defective checkpoints.

Targeting cell cycle kinases and kinesins in anticancer drug development

The cell cycle is regulated by kinases such as the cyclin-dependent kinases (CDKs) and non-CDKs, which include Aurora and polo-like kinases, as well as checkpoint proteins. Mitotic kinesins are involved in the establishment of the mitotic spindle formation and function, and also play a role in cell cycle control. The disruption of the cell cycle is a hallmark of malignancy. Genetic or epigenetic events result in the upregulation of these kinases and mitotic kinesins in a myriad of tumour types, suggesting that their inhibition could result in preferential targeting of malignant cells. Such findings make the development of these inhibitors a rational and attractive new area for cancer therapeutics. Although challenges of potency and non-specificity have hampered their progress through the clinic, several novel compounds are presently in various phases of clinical trial evaluation.

Targeting cell cycle regulation in cancer therapy

Cell proliferation is an essential mechanism for growth, development and regeneration of eukaryotic organisms; however, it is also the cause of one of the most devastating diseases of our era: cancer. Given the relevance of the processes in which cell proliferation is involved, its regulation is of paramount importance for multicellular organisms. Cell division is orchestrated by a complex network of interactions between proteins, metabolism and microenvironment including several signaling pathways and mechanisms of control aiming to enable cell proliferation only in response to specific stimuli and under adequate conditions. Three main players have been identified in the coordinated variation of the many molecules that play a role in cell cycle: i) The cell cycle protein machinery including cyclin-dependent kinases (CDK)-cyclin complexes and related kinases, ii) The metabolic enzymes and related metabolites and iii) The reactive-oxygen species (ROS) and cellular redox status. The role of these key players and the interaction between oscillatory and non-oscillatory species have proved essential for driving the cell cycle. Moreover, cancer development has been associated to defects in all of them. Here, we provide an overview on the role of CDK-cyclin complexes, metabolic adaptations and oxidative stress in regulating progression through each cell cycle phase and transitions between them. Thus, new approaches for the design of innovative cancer therapies targeting crosstalk between cell cycle simultaneous events are proposed.

Therapeutic potential and molecular mechanism of a novel sulfonamide anticancer drug, indisulam (E7070) in combination with CPT-11 for cancer treatment

PURPOSE

Indisulam (N-(-3-chloro-7-indolyl)-1,4-benzenedisulfonamide; E7070) is an experimental anticancer agent. Microarray analysis indicates that indisulam downregulates several genes involved in drug resistance, and this finding led us to test the effect of combining indisulam with other anticancer drugs. We investigated the antitumor effect and mechanism of synergism when indisulam was administered in combination with CPT-11.

METHODS

In vitro cytotoxic activity was examined using a cell counter kit, and the combination effect was determined by isobologram analysis. The level of topoisomerase IIα was measured by Western blotting. The in vivo antitumor effect was assessed in mice inoculated with human colorectal cancer SW620 cells.

RESULTS

Isobologram analysis indicated that a 24-h exposure to indisulam and SN-38, an active metabolite of CPT-11, had a synergistic effect in HCT116 and SW620 cells and an additive effect in HCT15 and WiDr cells. Prolongation of exposure to 48 h resulted in a synergistic effect in HCT15 and WiDr cells. Treatment with SN-38 alone increased the amount of intracellular topoisomerase IIα in all cell lines tested. Co-treatment with indisulam suppressed the SN-38-induced upregulation of topoisomerase IIα after 24 h of exposure in HCT116 and SW620 cells and after 48 h of exposure in HCT15 and WiDr cells. This apparent association between a synergistic effect and suppression of SN-38-mediated upregulation of topoisomerase IIα suggests that indisulam enhances SN-38 cytotoxicity by suppressing topoisomerase IIα upregulation to compensate for topoisomerase I inhibition by SN-38. Synergy was also observed in xenografted tumors and was accompanied by complete suppression of topoisomerase IIα upregulation induced by CPT-11 treatment.

CONCLUSION

These observations prompted the clinical evaluation of indisulam and CPT-11 combination therapy.

Predictive ability of a semi-mechanistic model for neutropenia in the development of novel anti-cancer agents: two case studies

In cancer chemotherapy neutropenia is a common dose-limiting toxicity. An ability to predict the neutropenic effects of cytotoxic agents based on proposed trial designs and models conditioned on previous studies would be valuable. The aim of this study was to evaluate the ability of a semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model for myelosuppression to predict the neutropenia observed in Phase I clinical studies, based on parameter estimates obtained from prior trials. Pharmacokinetic and neutropenia data from 5 clinical trials for diflomotecan and from 4 clinical trials for indisulam were used. Data were analyzed and simulations were performed using the population approach with NONMEM VI. Parameter sets were estimated under the following scenarios: (a) data from each trial independently, (b) pooled data from all clinical trials and (c) pooled data from trials performed before the tested trial. Model performance in each of the scenarios was evaluated by means of predictive (visual and numerical) checks. The semi-mechanistic PK/PD model for neutropenia showed adequate predictive ability for both anti-cancer agents. For diflomotecan, similar predictions were obtained for the three scenarios. For indisulam predictions were better when based on data from the specific study, however when the model parameters were conditioned on data from trials performed prior to a specific study, similar predictions of the drug related-neutropenia profiles and descriptors were obtained as when all data were used. This work provides further indication that modeling and simulation tools can be applied in the early stages of drug development to optimize future trials.

Development of cell-cycle inhibitors for cancer therapy

The cell cycle governs the transition from quiescence through cell growth to proliferation. The key parts of the cell cycle machinery are the cyclin-dependent kinases (CDKS) and the regulatory proteins called cyclins. The CDKS are rational targets for cancer therapy because their expression in cancer cells is often aberrant and their inhibition can induce cell death. Inhibitors of CDKS can also block transcription.Several drugs targeting the cell cycle have entered clinical trials. These agents include flavopiridol, indisulam, AZD5438, SNS-032, bryostatin-1, seliciclib, PD 0332991, and SCH 727965. Phase i studies have demonstrated that these drugs can generally be administered safely. Phase ii studies have shown little single-agent activity in solid tumors, but combination studies with cytotoxic chemotherapy have been more promising. In hematologic malignancies, reports have shown encouraging single-agent and combination activity. Pharmacodynamic studies show that the dose and schedule of these drugs are crucial to permit maximum therapeutic effect.

Covariate-based dose individualization of the cytotoxic drug indisulam to reduce the risk of severe myelosuppression

AIM

Chemotherapy with indisulam causes myelosuppression. This study aimed to evaluate the influence of patient-related covariates on pharmacokinetics and pharmacodynamics, to identify patients at risk for severe myelosuppression and to develop a dosing algorithm for treatment optimization.

METHODS

Pharmacokinetic and pharmacodynamic data of 412 patients were available. Non-linear mixed effects modeling was used to determine the relative risk of dose-limiting myelosuppression for various covariates (demographics, physical condition, prior treatment, comedication, CYP2C genotype and biochemistry).

RESULTS

Body surface area (BSA), race and CYP2C genotype had a significant impact on indisulam elimination (P < 0.001). Low BSA, Japanese race, variant CYP2C genotype, low baseline neutrophil and thrombocyte counts and female sex were clinically relevant risk factors of dose-limiting myelosuppression (RR > 1.1). A dosing strategy was developed to optimize treatment for patient subgroups.

CONCLUSIONS

This study has identified covariates related to an increased risk of myelosuppression after indisulam therapy. Dose individualization may contribute to treatment optimization.

Two-stage model-based clinical trial design to optimize phase I development of novel anticancer agents

Background The phase I program of anticancer agents usually consists of multiple dose escalation studies to select a safe dose for various administration schedules. We hypothesized that pharmacokinetic and pharmacodynamic (PK–PD) modeling of an initial phase I study (stage 1) can be used for selection of an optimal starting dose for subsequent studies (stage 2) and that a post-hoc PK–PD analysis enhances the selection of a recommended dose for phase II evaluation. The aim of this analysis was to demonstrate that this two-stage model-based design, which does not interfere in the conduct of trials, is safe, efficient and effective. Methods PK and PD data of dose escalation studies were simulated for nine compounds and for five administration regimens (stage 1) for drugs with neutropenia as dose-limiting toxicity. PK–PD models were developed for each simulated study and were used to determine a starting dose for additional phase I studies (stage 2). The model-based design was compared to a conventional study design regarding safety (number of dose-limiting toxicities (DLTs)), efficiency (number of patients treated with a dose below the recommended dose) and effectiveness (precision of dose selection). Retrospective data of the investigational anticancer drug indisulam were used to show the applicability of the model-based design. Results The model-based design was as safe as the conventional design (median number of DLTs = 3) and resulted in a reduction of the number of patients who were treated with a dose below the recommended dose (−27%, power 89%). A post-hoc model-based determination of the recommended dose for future phase II studies was more precise than the conventional selection of the recommended dose (root mean squared error 8.3% versus 30%). Conclusions A two-stage model-based phase I design is safe for anticancer agents with dose-limiting myelosuppression and may enhance the efficiency of dose escalation studies by reducing the number of patients treated with a dose below the recommended dose and by increasing the precision of dose selection for phase II evaluation.

A dose-escalation study of indisulam in combination with capecitabine (Xeloda) in patients with solid tumours

This dose escalation study was designed to determine the recommended dose of the multi-targeted cell cycle inhibitor indisulam in combination with capecitabine in patients with solid tumours and to evaluate the pharmacokinetics of the combination. Thirty-five patients were treated with indisulam on day 1 of each 21-day cycle. Capecitabine was administered two times daily (BID) on days 1–14. Plasma concentrations of indisulam, capecitabine and its three metabolites were determined for pharmacokinetic analysis. The main dose-limiting toxicity was myelosuppression. Hand/foot syndrome and stomatitis were the major non-haematological toxicities. The recommended dose was initially established at indisulam 700 mg m⁻² and capecitabine 1250 mg m⁻² BID. However, during cycle 2 the recommended dose was poorly tolerated in three patients. A dose of indisulam 500 mg m⁻² and capecitabine 1250 mg m⁻² BID proved to be safe at cycle 1 and 2 in nine additional patients. Indisulam pharmacokinetics during cycle 1 were consistent with pharmacokinetic data from phase I mono-therapy studies. However, exposure to indisulam was remarkably increased at cycle 2 due to a drug–drug interaction between capecitabine and indisulam. Partial response was confirmed in two patients, one with colon carcinoma and the other with pancreatic carcinoma. Seventeen patients had stable disease. Indisulam (700 mg m⁻²) in combination with capecitabine (1250 mg m⁻² BID) was well tolerated during the first cycle. A dose of indisulam 500 mg m⁻² and capecitabine 1250 mg m⁻² BID was considered safe in multiple treatment cycles. The higher incidence of toxicities observed during cycle 2 can be explained by a time-dependent pharmacokinetic drug–drug interaction.

PK/PD model of indisulam and capecitabine: interaction causes excessive myelosuppression

The anticancer agent indisulam was evaluated in a dose-escalation study in combination with capecitabine. Severe myelotoxicity was observed after multiple treatment cycles. We hypothesized that capecitabine inhibits the synthesis of CYP2C9, which metabolizes indisulam. The objectives were to develop a pharmacokinetic/pharmacodynamic (PK/PD) model for the combination treatment and to estimate the impact of a drug-drug interaction on the safety of various dose levels. NONMEM was used to develop a PK/PD model, including the impact of capecitabine coadministration on indisulam pharmacokinetics. A simulation study was performed to evaluate the risk of dose-limiting neutropenia. A time-dependent pharmacokinetic drug-drug interaction resulted in increased exposure to indisulam and in increased myelotoxicity. The risk of dose-limiting neutropenia increased with treatment duration and with dose. The excessive myelosuppression after multiple cycles may be explained by a pharmacokinetic interaction between indisulam and capecitabine. The combination of 550 mg/m(2) indisulam and 1,250 mg/m(2) capecitabine twice daily was considered safe.

CYP2C9 and CYP2C19 polymorphic forms are related to increased indisulam exposure and higher risk of severe hematologic toxicity

PURPOSE

The anticancer agent indisulam is metabolized by the cytochrome P450 of enzymes CYP2C9 and CYP2C19. Polymorphisms of these enzymes may affect the elimination rate of indisulam. Consequently, variant genotypes may be clinically relevant predictors for the risk of developing severe hematologic toxicity. The purposes of this study were to evaluate the effect of genetic variants of CYP2C9 and CYP2C19 on the pharmacokinetics of indisulam and on clinical outcome and to assess the need for pharmacogenetically guided dose adaptation.

EXPERIMENTAL DESIGN

Pharmacogenetic screening of CYP2C polymorphisms was done in 67 patients treated with indisulam. Pharmacokinetic data were analyzed with a population pharmacokinetic model, in which drug elimination was described by a linear and a Michaelis-Menten pathway. The relationships between allelic variants and the elimination pharmacokinetic parameters (CL, V(max), K(m)) were tested using nonlinear mixed-effects modeling. Polymorphisms causing a high risk of dose-limiting neutropenia were identified in a simulation study.

RESULTS

The Michaelis-Menten elimination rate (V(max)) was decreased by 27% (P<0.0001) for heterozygous CYP2C9*3 mutants. Heterozygous CYP2C19*2 and CYP2C19*3 mutations reduced the linear elimination rate (CL) by 38% (P < 0.0001). The risk of severe neutropenia was significantly increased by these mutations and dose reductions of 50 to 100 mg/m(2) per mutated allele may be required to normalize this risk.

CONCLUSIONS

CYP2C9*3, CYP2C19*2, and CYP2C19*3 polymorphisms resulted in a reduced elimination rate of indisulam. Screening for these CYP2C polymorphisms and subsequent pharmacogenetically guided dose adaptation may assist in the selection of an optimized initial indisulam dosage.

A randomized phase II pharmacokinetic and pharmacodynamic study of indisulam as second-line therapy in patients with advanced non-small cell lung cancer

PURPOSE

The primary aim of this study was to measure the objective tumor response rate following treatment with indisulam [E7070; N-(3-chloro-7-indolyl)-1,4-benzenedisulfonamide] as second-line therapy in patients with advanced non-small cell lung cancer. The secondary aims were to determine progression-free survival, to assess the safety and tolerability of indisulam, and to study its pharmacokinetic and pharmacodynamic profile.

EXPERIMENTAL DESIGN

Patients were randomized to receive indisulam every 3 weeks either as a single i.v. dose of 700 mg/m(2) on day one (dx1) or 130 mg/m(2) given on days 1 to 5 inclusive as a daily infusion (dx5). All patients had previously received platinum-based chemotherapy.

RESULTS

Forty-four patients were randomized. Only minor responses were seen. Myelosuppression, gastrointestinal symptoms, and lethargy were the most common toxicities and were more frequent in the dx1 arm. The pharmacokinetics of indisulam in each treatment schedule were adequately described using a previously developed population pharmacokinetic model and were mostly consistent with the results of the phase I program. Flow cytometric analysis of endobronchial and metastatic disease revealed a reduction in the fraction of cycling cells and an increase in apoptosis following indisulam compared with pretreatment levels.

CONCLUSIONS

We conclude that, despite evidence of tumor-specific indisulam-induced apoptosis, neither of these treatment schedules has single-agent activity as second-line treatment of non-small cell lung cancer.

A Semi-Physiological Population Pharmacokinetic Model Describing the Non-linear Disposition of Indisulam

The pharmacokinetic profile of the anti-cancer agent indisulam is non-linear. In addition to non-linear clearance, this may partially be explained by saturable distribution to red blood cells and saturable plasma protein binding. The aims of this study were to develop a semi-physiological population pharmacokinetic model of indisulam and to examine the impact of protein binding and distribution to red blood cells. Indisulam concentrations in plasma, plasma ultrafiltrate and in red blood cells from multiple phase I studies in Caucasian and Japanese patients were used to develop a pharmacokinetic model using NONMEM. This model comprised four physiological compartments: plasma, red blood cells, interstitial fluid and tissue. A simulation study was performed to examine the contribution of physiological processes in indisulam pharmacokinetics. Plasma albumin concentrations were predictive for the maximal protein binding capacity and considerably influenced total plasma concentrations of indisulam, whereas free plasma concentrations remained relatively unaffected. The maximal specific red blood cell binding capacity was 64.0 ( +/-5.9) mg/L and corresponded to the typical red blood cell carbonic anhydrase concentration. Simulation studies demonstrated that the hematocrit does not have a clinically relevant impact on indisulam disposition. This semi-physiological model allowed adequate prediction of the time profiles of indisulam concentrations in all monitored compartments for a large range of dose levels and several treatment regimens. The model has elucidated the mechanism and the role of saturable plasma protein binding and saturable distribution to red blood cells in indisulam pharmacokinetics and provides a basis for rationale PK-PD relationships.

Interactions between hypoxia and epidermal growth factor receptor in non-small-cell lung cancer

Tumor hypoxia has been recognized to confer resistance to anticancer therapy since the early 20th century. More recently, its fundamental role in tumorigenesis has been established. Hypoxia-inducible factor (HIF)-1 has been identified as an important transcription factor that mediates the cellular response to hypoxia, promoting both cellular survival and apoptosis under different conditions. Increased tumor cell expression of this transcription factor promotes tumor growth in vivo and is associated with a worse prognosis in patients with non-small-cell lung cancer (NSCLC) undergoing tumor resection. The epidermal growth factor receptor (EGFR) promotes tumor cell proliferation and angiogenesis and inhibits apoptosis. Epidermal growth factor receptor expression increases in a stepwise manner during tumorigenesis and is overexpressed in > 50% of NSCLC tumors. This review discusses the reciprocal relationship between tumor cell hypoxia and EGFR. Recent studies suggest that hypoxia induces expression of EGFR and its ligands. In return, EGFR might enhance the cellular response to hypoxia by increasing expression of HIF-1a and so act as a survival factor for hypoxic cancer cells. Immunohistochemical studies on a series of resected NSCLC tumors add weight to this contention by demonstrating a close association between expression of EGFR, HIF-1a, and 1 of HIF-1's target proteins, carbonic anhydrase IX. In this article we discuss emerging treatment strategies for NSCLC that target HIF-1, HIF-1 transcriptional targets, and EGFR.

Saturable binding of indisulam to plasma proteins and distribution to human erythrocytes

The anticancer agent indisulam has a nonlinear pharmacokinetic profile, which may be partly related to saturable binding to blood constituents. To gain insight into the complex nonlinear behavior of indisulam, we investigated binding to plasma proteins and erythrocytes. The purpose of the study was to develop a physiological model for the distribution of indisulam in blood. Concentrations of radiolabeled indisulam were measured in vitro 1) in total plasma and in ultrafiltrate to investigate plasma protein binding, 2) in erythrocytes and in plasma to investigate distribution to erythrocytes, and 3) in erythrocyte membranes to investigate nonspecific binding in erythrocytes. For in vivo assessment, 21 patients received 400 to 900 mg/m2 indisulam in a 1- or 2-h infusion. Total and free concentrations in plasma and concentrations in erythrocytes were determined at multiple time points. In vitro plasma protein binding was described by a Langmuir model with a maximal binding capacity (Bmax = 767 microM) and an equilibrium dissociation constant (KD = 1.02 microM). The maximal capacity of plasma protein binding in vivo corresponded to albumin levels. The bound concentration in erythrocytes was described by a two-site model, comprising a saturable and a nonspecific binding component. The saturable component (Bmax = 174 microM) may correspond to binding to carbonic anhydrase. The physiological model adequately described the nonlinear disposition of indisulam in whole blood. Indisulam was bound to plasma proteins and distributed to erythrocytes in a saturable manner. These saturable processes may be attributed to binding to albumin (in plasma) and to carbonic anhydrase (in erythrocytes).

Targeting the cell cycle: a new approach to cancer therapy

The cell cycle represents a series of tightly integrated events that allow the cell to grow and proliferate. Critical parts of the cell cycle machinery are the cyclin-dependent kinases (CDKs), which, when activated, provide a means for the cell to move from one phase of the cell cycle to the next. The CDKs are regulated positively by cyclins and regulated negatively by naturally occurring CDK inhibitors (CDKIs). Cancer represents a dysregulation of the cell cycle such that cells that overexpress cyclins or do not express the CDKIs continue to undergo unregulated cell growth. The cell cycle also serves to protect the cell from DNA damage. Thus, cell cycle arrest, in fact, represents a survival mechanism that provides the tumor cell the opportunity to repair its own damaged DNA. Thus, abrogation of cell cycle checkpoints, before DNA repair is complete, can activate the apoptotic cascade, leading to cell death. Now in clinical trials are a series of targeted agents that directly inhibit the CDKs, inhibit unrestricted cell growth, and induce growth arrest. Recent attention has also focused on these drugs as inhibitors of transcription. In addition, there are now agents that abrogate the cell cycle checkpoints at critical time points that make the tumor cell susceptible to apoptosis. An understanding of the cell cycle is critical to understanding how best to clinically develop these agents, both as single agents and in combination with chemotherapy.

Phase I pharmacokinetic and pharmacogenomic study of E7070 administered once every 21 days

E7070 is a novel sulfonamide anticancer agent that disrupts the G1/S phase of the cell cycle. The objectives of this phase I study of E7070 were to estimate the maximal tolerated dose (MTD), to determine the recommended dose for phase II, and to clarify the pharmacokinetic profile of E7070 and its relation to polymorphisms of CYP2C9 (*2, *3) and CYP2C19 (*2, *3) in Japanese patients. Patients received 1-2-h i.v. infusions of E7070 (400, 600, 700, 800 or 900 mg/m2) on day 1 of a 21-day cycle. Twenty-one patients received between one and eight cycles of E7070. The dose-limiting toxicities (DLT) comprised leukopenia, neutropenia, thrombocytopenia, elevation of aspartate aminotransferase, colitis, and ileus. The mean area under the plasma concentration-time curve (AUC) for successive dose levels increased in a non-dose-proportional manner. Two patients were heterozygous for the CYP2C9 mutation. For CYP2C19, eight patients were wild type and the remainder had heterozygous (n = 8) or homozygous mutations (n = 5). Regarding the CYP2C19 genotype, the AUC of patients with mutant alleles were higher than those of patients with wild type at a dose of 600 mg/m2 or more. The severity of toxic effects, such as myelosuppression, seemed to depend on the AUC. No partial responses were observed. One patient treated at a dose of 700 mg/m2 experienced a maximum tumor volume reduction of 22.5%. The MTD was estimated to be 900 mg/m2. A dose of 800 mg/m2 is recommended for further phase II studies. The pharmacokinetic/pharmacodynamic properties of E7070 seemed to be influenced by CYP2C19 genotype. The observed safety profile and preliminary evidence of antitumor activity warrant further investigation of this drug in monotherapy or in combination chemotherapy.

Semi-physiological model describing the hematological toxicity of the anti-cancer agent indisulam

Indisulam (N-(3-chloro-7-indolyl)-1,4-benzenedisulfonamide, GOAL, E7070) is a novel anti-cancer drug currently in phase II clinical development for the treatment of solid tumors. Phase I dose-escalation studies were conducted comparing four treatment schedules. Neutropenia and thrombocytopenia were dose limiting in all schedules. The aim of this study was to describe the extent and the time course of the hematological toxicity and its possible schedule dependency using a semi-physiological model. Data from 142 patients were analyzed using NONMEM. The semi-physiological model comprised a progenitor blood cell compartment, linked to the central circulation compartment, through 3 transition compartments representing the maturation chain in the bone marrow. Plasma concentrations of the drug were assumed to reduce the proliferation rate in the progenitor compartment according to a linear function. A feedback mechanism was included in the model representing the rebound effect of endogenous growth factors. The model was validated using a posterior predictive check. The model adequately described the extent and time course of neutropenia and thrombocytopenia. The mean transition time (MTT, i.e. maturation time in bone marrow) of neutrophils was increased by 47% in patients who received indisulam as a weekly dose administered for four out of every six weeks. For platelets, MTT was increased by 33% in patients who received this schedule and also in patients who received a continuous 120-h infusion. The validation procedure indicated that the model adequately predicts the nadir value of neutrophils and platelets and the time to reach this nadir. A semi-physiological model was successfully applied to describe the time course and extent of the neutropenia and thrombocytopenia after indisulam administration for four treatment schedules.

Phase II study of E7070 in patients with metastatic melanoma

E7070 is a synthetic chloro-indolyl sulphonamide that is being developed as an anti cancer agent. In this phase II study, 28 patients with metastatic melanoma received 700 mg/m(2) of E7070 as a 60-min infusion repeated every 3 weeks. Although therapy was well tolerated, with one patient receiving 14 courses of treatment, there were only minor responses on independent radiological review. E7070 does not warrant further development as a single agent for the treatment of metastatic melanoma.

A phase II clinical and pharmacodynamic study of E7070 in patients with metastatic, recurrent, or refractory squamous cell carcinoma of the head and neck: modulation of retinoblastoma protein phosphorylation by a novel chloroindolyl sulfonamide cell cycle inhibitor

PURPOSE

E7070 is a synthetic sulfonamide cell cycle inhibitor that induces hypophosphorylation of the retinoblastoma (Rb) protein and G(1) arrest in vitro. This Phase II study was conducted to explore the efficacy, safety, and pharmacodynamics of E7070 in squamous cell carcinoma of the head and neck (SCCHN).

EXPERIMENTAL DESIGN

Patients with metastatic, recurrent, or refractory SCCHN, treated with no more than one prior therapy for recurrent disease, received E7070 at 700 mg/m(2) over 1 h every 3 weeks. Pre- and posttreatment tumor fine needle aspirates were subjected to immunohistochemistry with a panel of phospho-specific anti-Rb antibodies. End points included progression-free survival, response rate and duration, overall survival, toxicity profile, and inhibition of Rb phosphorylation.

RESULTS

Because none of the first 15 patients achieved progression-free survival > 4 months, the early stopping rule was invoked. Eleven patients had oropharyngeal cancer and 12 were male. Median age was 59 years (range, 49-73 years). Thirty-nine cycles of E7070 were delivered (median, 2.6 cycles/patient; range, 1-5 cycles). Six patients had stable disease after 2 cycles and 2 patients each subsequently received 1, 2, and 3 additional cycles, respectively, before experiencing progression. Immunohistochemistry of tumor cell aspirates from 3 patients demonstrated reduced Rb phosphorylation posttreatment.

CONCLUSIONS

At this dose and schedule, E7070 is unlikely to be superior over single-agent chemotherapy in SCCHN. However, the data suggest that cdk activity can be inhibited in tumor cells, resulting in posttreatment modulation of Rb phosphorylation. In the absence of cytotoxicity, more frequent administration of E7070 may be required to sustain Rb hypophosphorylation and cytostatic growth arrest.

Pharmacokinetics of the nonsteroidal steroid sulphatase inhibitor 667 COUMATE and its sequestration into red blood cells in rats

Breast cancer is a major cause of mortality in Western countries and there is an urgent requirement for novel treatment strategies. The nonsteroidal sulphatase inhibitor 667 COUMATE inhibits hepatic steroid sulphatase and growth of oestrone sulphate stimulated tumours in the nitrosomethylurea-induced rat mammary model. Other compounds that contain an aryl sulphamate moiety, for example, oestrone-3-O-sulphamate, are sequestered into red blood cells (RBCs). The aims of this study were to determine the pharmacokinetics of 667 COUMATE and to investigate its sequestration into RBCs. We administered a single p.o. or i.v. dose (10 mg kg⁻¹) of 667 COUMATE to rats and used a high-performance liquid chromatography method to measure the levels of the agent and its putative metabolites in plasma. 667 COUMATE had a bioavailability of 95% and could be detected in plasma for up to 8 h. Using two independent analytical methods, we demonstrated that 667 COUMATE is sequestered by RBCs both ex vivo and in vivo. Previous investigations have revealed that 667 COUMATE is rapidly degraded in plasma ex vivo. In this study, we demonstrate that 667 COUMATE is stabilised due to its sequestration into RBCs. In conclusion, the pharmacological efficacy and high oral bioavailability of 667 COUMATE may be partly a consequence of the ability of RBCs to both protect the agent from metabolic degradation and facilitate its transport to tissues. These data support the further clinical evaluation of this novel endocrine therapeutic agent.

Sulfur Dioxide Mediated One-Pot, Three- and Four-Component Syntheses of Polyfunctional Sulfonamides and Sulfonic Esters: Study of the Stereoselectivity of the Ene Reaction of Sulfur Dioxide

The ene reaction of sulfur dioxide with enoxysilanes or with allylsilanes generates silyl sulfinates that can be brominated (Br(2) or NBS) or chlorinated (NCS or Cl(2)) to produce the corresponding sulfonyl halides. They react with primary and secondary amines or alcohols to give the corresponding sulfonamides and sulfonic esters, respectively. The hetero-Diels-Alder addition of sulfur dioxide to 1-oxy- or 1,3-dioxy-1,3-dienes generates zwitterions that add to enoxysilanes or allylsilanes giving silyl sulfinates that can be converted in situ into polyfunctional sulfonamides or sulfonic esters. This realizes quick access to libraries of complicated sulfonamides and sulfonic esters applying one-pot, three- and four-component methods.