Phase I and pharmacokinetic study of E7070, a novel sulfonamide, given at a daily times five schedule in patients with solid tumors. A study by the EORTC-early clinical studies group (ECSG)

RBM39 degrader invigorates natural killer cells to eradicate neuroblastoma despite cancer cell plasticity

The cellular plasticity of neuroblastoma is defined by a mixture of two major cell states, adrenergic (ADRN) and mesenchymal (MES), which may contribute to therapy resistance. However, how neuroblastoma cells switch cellular states during therapy remains largely unknown and how to eradicate neuroblastoma regardless of their cell states is a clinical challenge. To better understand the lineage switch of neuroblastoma in chemoresistance, we comprehensively defined the transcriptomic and epigenetic map of ADRN and MES types of neuroblastomas using human and murine models treated with indisulam, a selective RBM39 degrader. We showed that cancer cells not only undergo a bidirectional switch between ADRN and MES states, but also acquire additional cellular states, reminiscent of the developmental pliancy of neural crest cells. The lineage alterations are coupled with epigenetic reprogramming and dependency switch of lineage-specific transcription factors, epigenetic modifiers and targetable kinases. Through targeting RNA splicing, indisulam induces an inflammatory tumor microenvironment and enhances anticancer activity of natural killer cells. The combination of indisulam with anti-GD2 immunotherapy results in a durable, complete response in high-risk transgenic neuroblastoma models, providing an innovative, rational therapeutic approach to eradicate tumor cells regardless of their potential to switch cell states.

Indisulam synergizes with palbociclib to induce senescence through inhibition of CDK2 kinase activity

Inducing senescence in cancer cells is emerging as a new therapeutic strategy. In order to find ways to enhance senescence induction by palbociclib, a CDK4/6 inhibitor approved for treatment of metastatic breast cancer, we performed functional genetic screens in palbociclib-resistant cells. Using this approach, we found that loss of CDK2 results in strong senescence induction in palbociclib-treated cells. Treatment with the CDK2 inhibitor indisulam, which phenocopies genetic CDK2 inactivation, led to sustained senescence induction when combined with palbociclib in various cell lines and lung cancer xenografts. Treating cells with indisulam led to downregulation of cyclin H, which prevented CDK2 activation. Combined treatment with palbociclib and indisulam induced a senescence program and sensitized cells to senolytic therapy. Our data indicate that inhibition of CDK2 through indisulam treatment can enhance senescence induction by CDK4/6 inhibition.

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.

Therapeutic Targeting of Alternative RNA Splicing in Gastrointestinal Malignancies and Other Cancers

Recent comprehensive genomic studies including single-cell RNA sequencing and characterization have revealed multiple processes by which protein-coding and noncoding RNA processing are dysregulated in many cancers. More specifically, the abnormal regulation of mRNA and precursor mRNA (pre-mRNA) processing, which includes the removal of introns by splicing, is frequently altered in tumors, producing multiple different isoforms and diversifying protein expression. These alterations in RNA processing result in numerous cancer-specific mRNAs and pathogenically spliced events that generate altered levels of normal proteins or proteins with new functions, leading to the activation of oncogenes or the inactivation of tumor suppressor genes. Abnormally spliced pre-mRNAs are also associated with resistance to cancer treatment, and certain cancers are highly sensitive to the pharmacological inhibition of splicing. The discovery of these alterations in RNA processing has not only provided new insights into cancer pathogenesis but identified novel therapeutic vulnerabilities and therapeutic opportunities in targeting these aberrations in various ways (e.g., small molecules, splice-switching oligonucleotides (SSOs), and protein therapies) to modulate alternative RNA splicing or other RNA processing and modification mechanisms. Some of these strategies are currently progressing toward clinical development or are already in clinical trials. Additionally, tumor-specific neoantigens produced from these pathogenically spliced events and other abnormal RNA processes provide a potentially extensive source of tumor-specific therapeutic antigens (TAs) for targeted cancer immunotherapy. Moreover, a better understanding of the molecular mechanisms associated with aberrant RNA processes and the biological impact they play might provide insights into cancer initiation, progression, and metastasis. Our goal is to highlight key alternative RNA splicing and processing mechanisms and their roles in cancer pathophysiology as well as emerging therapeutic alternative splicing targets in cancer, particularly in gastrointestinal (GI) malignancies.

RNA-binding protein 39: a promising therapeutic target for cancer

RNA-binding motif protein 39 (RBM39), as a key factor in tumor-targeted mRNA and protein expression, not only plays a vital role in tumorigenesis, but also has broad development prospects in clinical treatment and drug research. Moreover, since RBM39 was identified as a target of sulfonamides, it has played a key role in the emerging field of molecule drug development. Hence, it is of great significance to study the interaction between RBM39 and tumors and the clinical application of drug-targeted therapy. In this paper, we describe the possible multi-level regulation of RBM39, including gene transcription, protein translation, and alternative splicing. Importantly, the molecular function of RBM39 as an important splicing factor in most common tumors is systematically outlined. Furthermore, we briefly introduce RBM39’s tumor-targeted drug research and its clinical application, hoping to give reference significance for the molecular mechanism of RBM39 in tumors, and provide reliable ideas for in-depth research for future therapeutic strategies.

Cancer therapies based on targeted protein degradation - lessons learned with lenalidomide

For decades, anticancer targeted therapies have been designed to inhibit kinases or other enzyme classes and have profoundly benefited many patients. However, novel approaches are required to target transcription factors, scaffolding proteins and other proteins central to cancer biology that typically lack catalytic activity and have remained mostly recalcitrant to drug development. The selective degradation of target proteins is an attractive approach to expand the druggable proteome, and the selective oestrogen receptor degrader fulvestrant served as an early example of this concept. Following a long and tragic history in the clinic, the immunomodulatory imide drug (IMiD) thalidomide was discovered to exert its therapeutic activity via a novel and unexpected mechanism of action: targeting proteins to an E3 ubiquitin ligase for subsequent proteasomal degradation. This discovery has paralleled and directly catalysed myriad breakthroughs in drug development, leading to the rapid maturation of generalizable chemical platforms for the targeted degradation of previously undruggable proteins. Decades of clinical experience have established front-line roles for thalidomide analogues, including lenalidomide and pomalidomide, in the treatment of haematological malignancies. With a new generation of 'degrader' drugs currently in development, this experience provides crucial insights into class-wide features of degraders, including a unique pharmacology, mechanisms of resistance and emerging therapeutic opportunities. Herein, we review these past experiences and discuss their application in the clinical development of novel degrader therapies.

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.

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.

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.

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.

Self-associated indisulam in phospholipid-based nanomicelles: a potential nanomedicine for cancer

This study aimed to begin development of a nanomedicine containing indisulam solubilized in sterically stabilized micelles (SSMs) composed of DSPE-PEG(2000) or sterically stabilized mixed micelles (SSMMs) composed of DSPE-PEG(2000) plus egg phosphatidylcholine. Micelles were prepared by co-precipitation and reconstitution of drug and lipids. Particle size distributions of micellar formulations were determined by quasi-elastic light scattering. Amounts of solubilized drug were determined by reverse-phase high-performance liquid chromatography (RP-HPLC). In vitro cytotoxicity of indisulam in nanocarrier was determined on the MCF-7 cell line by the National Cancer Institute-developed sulforhodamine B assay. Optimal solubilized indisulam concentrations in 5 mM total lipid were 10 microg/mL for SSMMs and 400 microg/mL for SSMs. HPLC results demonstrated that the encapsulation capacity of both micelles was over 95%. In vitro studies showed that indisulam in micellar system was more effective than free indisulam. The optimized formulation was successfully freeze-dried without any addition of lyoprotectants or cryoprotectants. We conclude that SSMs are a promising nanocarrier for indisulam, and indisulam-SSMs should be developed further as a novel targeted nanomedicine.

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.

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).

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.

Clinical anticancer drug development: targeting the cyclin-dependent kinases

Cell division involves a cyclical biochemical process composed of several step-wise reactions that have to occur once per cell cycle. Dysregulation of cell division is a hallmark of all cancers. Genetic and epigenetic mechanisms frequently result in deranged expression and/or activity of cell-cycle proteins including the cyclins, cyclin-dependent kinases (Cdks), Cdk inhibitors and checkpoint control proteins. The critical nature of these proteins in cell cycling raises hope that targeting them may result in selective cytotoxicity and valuable anticancer activity.

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.

Carbonic anhydrase inhibitors: inhibition of the tumor-associated isozyme IX with fluorine-containing sulfonamides. The first subnanomolar CA IX inhibitor discovered

Polyfluorinated CAIs show very good inhibitory properties against different carbonic anhydrase (CA) isozymes, such as CA I, II, and IV, but such compounds have not been tested for their interaction with the transmembrane, tumor-associated isozyme CA IX. Thus, a series of such compounds has been obtained by attaching 2,3,5,6-tetrafluorobenzoyl- and 2,3,5,6-tetrafluorophenylsulfonyl- moieties to aromatic/heterocyclic sulfonamides possessing derivatizable amino moieties. Some of these compounds showed excellent CA IX inhibitory properties and also selectivity ratios favorable to CA IX over CA II, the other physiologically relevant isozyme with high affinity for sulfonamide inhibitors. The first subnanomolar and rather selective CA IX inhibitor has been discovered, as the 2,3,5,6-tetrafluorobenzoyl derivative of metanilamide showed an inhibition constant of 0.8 nM against hCA IX, and a selectivity ratio of 26.25 against CA IX over CA II. Several other low nanomolar CA IX inhibitors were detected among the new derivatives reported here. The reported derivatives constitute valuable candidates for the development of novel antitumor therapies based on the selective inhibition of tumor-associated CA isozymes.

Cell-cycle targeted therapies

Eukaryotic organisms depend on an intricate and evolutionary conserved cell cycle to control cell division. The cell cycle is regulated by a number of important protein families which are common targets for mutational inactivation or overexpression in human tumours. The cyclin D and E families and their cyclin-dependent kinase partners initiate the phosphorylation of the retinoblastoma tumour suppressor protein and subsequent transition through the cell cycle. Cyclin/cdk activity and therefore control of cell division is restrained by two families of cyclin dependent kinase inhibitors. A greater understanding of the cell cycle has led to the development of a number of compounds with the potential to restore control of cell division in human cancers. This review will introduce the protein families that regulate the cell cycle, their aberrations in malignant progression and pharmacological strategies targeting this important process.

Quantitative determination of the novel anticancer drug E7070 (indisulam) and its metabolite (1,4-benzenedisulphonamide) in human plasma, urine and faeces by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry

E7070 (indisulam) is a novel anticancer drug currently undergoing clinical investigation. We present a sensitive and specific method for the quantitative determination of E7070 and its metabolite M1 (1,4-benzenedisulphonamide) in human plasma, urine and faeces. The analytes and their tetra-deuterated analogues, which were used as internal standards, were isolated from the biological matrix by solid-phase extraction with OASIS cartridges (0.5 mL plasma or 1 mL urine) and by liquid-liquid extraction with ethyl acetate at pH 5 (1 mL faecal homogenate). The analytes were separated on a C8 reversed-phase chromatographic column and analyzed using electrospray ionization and tandem mass spectrometric detection in the negative ion mode. The validated concentration ranges in plasma were 0.1-20 microg/mL for E7070 and 0.01-2 microg/mL for M1. In urine and faecal homogenate, a concentration range from 0.05-10 microg/mL or microg/g, respectively, was validated for both analytes. Validation of the plasma assay was performed according to the most recent FDA guidelines. The assay fulfilled all generally accepted requirements for linearity (r > 0.99, residuals between -8 and 10%), accuracy (-13.5 to 1.4%) and precision (all less than 11%) in the tested matrices. We investigated recovery, stability (working solutions at -20 degrees C and at room temperature, biological matrices at -20 degrees C, room temperature and after 3 freeze/thaw cycles; final extracts at room temperature) and robustness. All these parameters were found acceptable. This method is suited for mass balance studies or therapeutic drug monitoring, as demonstrated by a case example showing plasma concentrations and cumulative excretion of E7070 and M1 in urine and faeces. Furthermore, we show the presence of E7070 metabolites in patient urine.

Carbonic anhydrase inhibitors: E7070, a sulfonamide anticancer agent, potently inhibits cytosolic isozymes I and II, and transmembrane, tumor-associated isozyme IX

E7070 [N-(3-chloro-7-indolyl)-1,4-benzenedisulfonamide] is an anticancer drug candidate under clinical development for the treatment of several types of cancers. We prove here that this compound also acts as a potent carbonic anhydrase (CA) inhibitor. Similarly to the clinically used drugs acetazolamide, methazolamide and topiramate, E7070 showed inhibition constants in the range of 15-31nM against isozymes I, II and IX, being slightly less effective as a CA IV inhibitor (K(i) of 65nM). The X-ray crystal structure of the adduct of hCA II with E7070 revealed unprecedented interactions between the inhibitor and the active site, with three different conformations of the chloroindole fragment of the inhibitor interacting with different amino acid residues/water molecules of the enzyme. A superimposition of these conformations with those of other sulfonamide/sulfamate CA inhibitors indicated that similar regions of the hCA II active site could be involved in the interaction with inhibitors.

In vitro pharmacokinetic study of the novel anticancer agent E7070: red blood cell and plasma protein binding in human blood

E7070 is a novel sulfonamide anticancer agent that arrests the G(1)/S phase of the cell cycle. Preclinical and phase I studies have demonstrated non-linear pharmacokinetics (PK) of the drug. A population PK analysis revealed that the human plasma concentration-time data were best described by a three-compartment model with non-linear distribution. We have studied the in vitro interaction of 14C-radiolabeled E7070 with red blood cells (RBC) and its binding to plasma proteins in the concentration range where non-linearity in disposition was observed in humans to get more insight into the behavior of the drug. After the addition of E7070 to whole blood at 37 degrees C, the drug is taken up or binds to RBC in a concentration-dependent manner. The addition of sodium azide, however, did not result in a decrease of drug uptake by RBC, indicating passive diffusion processes. A non-linear increase in drug uptake was observed at incubation concentrations above 4 microg/ml E7070 in whole blood. This non-linearity was confirmed by lower partition coefficients between RBC and plasma at higher incubation concentrations (from 2.37 at 4 microg/ml to 0.31 at 200 microg/ml). The plasma protein binding of E7070 was high (98-99%) and linear in the concentration range studied (20-200 microg/ml). In conclusion, E7070 in whole blood is preferentially bound to RBC and exhibits high plasma protein binding. The non-linear distribution of E7070 in humans can be caused, in part at least, by saturable binding of E7070 to RBC.

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)

A single-agent dose-escalating phase I study on the novel sulfonamide E7070 was performed to determine the toxicity profile and the recommended dose for phase II studies. The pharmacokinetic profile of E7070 was also determined. E7070 was administered as a continuous infusion over 5 days repeated every 3 weeks. 27 patients were treated at doses ranging from 6 to 200 mg/m(2)/day. As with other administration schedules, the dose-limiting toxicities were dose-dependent, reversible neutropenia and thrombocytopenia. Although no objective responses were observed, seven patients had stable disease. E7070 displayed a non-linear pharmacokinetic profile, especially at dose-levels greater than 24 mg/m(2)/day, with a reduction in clearance and an increase in the half-life at the higher dose levels. The risk of myelosuppression became significant with an AUC greater than 4000 microg h/ml. The recommended dose of E7070 for further studies is 96 mg/m(2)/day when administered on a 5-day continuous infusion schedule every 3 weeks.

E7070: a novel synthetic sulfonamide targeting the cell cycle progression for the treatment of cancer

Cell cycle regulation and cell growth are interesting targets in the search for new antitumor agents as these processes are highly disturbed in malignant cells. E7070 is a novel synthetic sulfon-amide that targets the G1 phase of the cell cycle and is currently in clinical development for the treatment of solid tumors. The potential antitumor activity of the compound was discovered through optimization of the structure-activity relationships of a series of sulfonamide structures. E7070 causes a blockade in the G1/S transition through inhibition of the activation of both cyclin-dependent kinase 2 and cyclin E. Preclinical studies with E7070 showed activity in multiple tumor types, most prominently in colon and lung cancer. A phase I clinical program was conducted with E7070 evaluating different treatment regimens. Dose-limiting toxicities were hematological, including neutropenia and thrombocytopenia. Preliminary results of phase II studies demonstrated limited antitumor activity following treatment with E7070 as single agent in heavily pretreated patients with non-small cell lung and colon cancer. Studies evaluating the activity of E7070 in combination with other chemotherapeutic agents are being conducted.

Development and validation of limited sampling strategies for prediction of the systemic exposure to the novel anticancer agent E7070 (N-(3-chloro-7-indolyl)-1,4-benzenedisulphonamide)

AIMS

E7070 is a novel, sulphonamide anticancer agent currently under clinical development for the treatment of solid tumours. The aim of this study was to develop and validate limited sampling strategies for the prediction of E7070 exposure in two different treatment schedules for phase II studies using the Bayesian estimation approach.

METHODS

Data from two phase I dose finding studies were used in which E7070 was administered either as a single 1 h infusion or as a daily 1 h infusion for 5 days. Plasma concentration-time data from 75 patients were randomly divided into an index data set, used for the development of the strategies, and a validation data set. Population pharmacokinetic parameters were derived on the basis of the index data set. The D-optimality algorithm was used for the selection of optimal time points for both treatment schedules. The developed strategies were compared by assessment of their predictive performance of exposure, expressed as AUC (area under the plasma concentration vs time curve), in the validation data set.

RESULTS

The developed population pharmacokinetic model comprised three compartments, with saturable distribution to one peripheral compartment and both linear and saturable elimination from the central compartment. For the 1 h infusion, a four sample strategy was selected which resulted in unbiased and accurate predictions of AUC (bias 0.74%, precision 13%). A five sample strategy was generated for the daily times five schedule yielding unbiased (bias 3.2%) and precise (12% precision) predictions of AUC.

CONCLUSIONS

Optimal sampling strategies were developed and validated for estimation of E7070 exposure in two different treatment schedules. Both schedules enabled accurate and unbiased predictions of AUC.

Population pharmacokinetics of the novel anticancer agent E7070 during four phase I studies: model building and validation

PURPOSE

N-(3-Chloro-7-indolyl)-1,4-benzenedisulfonamide (E7070) is a novel sulfonamide anticancer agent currently in phase II clinical development for the treatment of solid tumors. Four phase I studies have been finalized, with E7070 administered at four different treatment schedules to identify the maximum-tolerated dose and the dose-limiting toxicities. Pharmacokinetic analyses of all studies revealed E7070 to have nonlinear pharmacokinetics. A population pharmacokinetic model was designed and validated to describe the pharmacokinetics of E7070 at all four treatment schedules and to identify the possible influences of patient characteristics on the pharmacokinetic parameters.

PATIENTS AND METHODS

Plasma concentration-time data of all patients (n = 143) were fitted to several pharmacokinetic models using NONMEM. Seventeen covariables were investigated for their relation with individual pharmacokinetic parameters. A bootstrap procedure was performed to check the validity of the model.

RESULTS

The data were best described using a three-compartment model with nonlinear distribution to a peripheral compartment and two parallel pathways of elimination from the central compartment: a linear and a saturable pathway. Body-surface area (BSA) was significantly correlated to both the volume of distribution of the central compartment and to the maximal elimination capacity. The fits of 500 bootstrap replicates of the data set demonstrated the robustness of the developed population pharmacokinetic model.

CONCLUSION

A population pharmacokinetic model has been designed and validated that accurately describes the data of four phase I studies with E7070. Furthermore, it has been demonstrated that BSA-guided dosing for E7070 is important.

An excretion balance and pharmacokinetic study of the novel anticancer agent E7070 in cancer patients

E7070 is a novel sulfonamide anticancer agent that arrests the G /S phase of the cell cycle. Preclinical and phase I studies have demonstrated non-linear pharmacokinetics of the drug. The objective of this study was to quantify the excretion of E7070 and the metabolite 1,4-benzene-sulfonamide (M1) in cancer patients. E7070 (1,000 mg) radiolabeled by (14)C in the benzene disulfonamide moiety (cohort 1, n = 6) or in the indole moiety (cohort 2, n = 7) was i.v. infused over 1 h. The levels of radioactivity in plasma, red blood cells, urine and feces were determined by liquid scintillation counting, and the E7070 and M1 concentrations in plasma, urine and feces were determined by coupled liquid chromatography-tandem mass spectrometry (LC/ESI-MS/MS). In plasma, the mean area under the concentration-time curve (AUC) based on radio-activity measurements (32.5 and 28.9 h. mM in cohorts 1 and 2, respectively) was substantially higher than the mean AUC of E7070 (3.8 h x mmol/l) and M1 (0.1 h x mmol/l) in all patients. The excretion of radioactivity (mean +/- SD) as a percentage of administered radioactivity was higher in urine [63.7 +/- 9.8% (cohort 1) and 61.5 +/- 5.5% (cohort 2)] than in feces [22.7 +/- 2.6% (1) and 21.1 +/- 3.1% (2)] during a mean collection period of 11 days. In both cohorts, the contribution of urinary and fecal recovery of E7070 (2.3 and 2.7%, respectively) and M1 (5.3 and 5.1%, respectively) was low. Subsequent HPLC analysis with online radioisotope detection of urine showed that the high radioactivity levels are caused by compounds other than E7070 and M1. The major metabolite is formed by glucuronidation of a hydroxylated metabolite of E7070. In conclusion, the excretion of the benzene sulfonamide and the indole moieties of E7070 was the same with a higher renal than gastrointestinal excretion. E7070 is extensively converted into currently unidentified metabolites. Glucuronidation is a major metabolic pathway.

Synthesis and biological evaluation of N-(7-indolyl)-3-pyridinesulfonamide derivatives as potent antitumor agents

We herein report the synthesis and antitumor activity of E7070 analogues containing a 3-pyridinesulfonamide moiety. E7070 was selected from our sulfonamide-based compound collections, currently undergoing Phase II clinical trials because of its tolerable toxicity profile and some antitumor responses in the Phase I setting. Of the analogues examined, ER-35745, a 6-amino-3-pyridinesulfonamide derivative, demonstrated significant oral efficacy against the HCT116 human colon carcinoma xenograft in nude mice.

Phase I and pharmacokinetic study of E7070, a novel chloroindolyl sulfonamide cell-cycle inhibitor, administered as a one-hour infusion every three weeks in patients with advanced cancer

PURPOSE

The objectives were to determine the maximum-tolerated dose, the recommended dose, the dose-limiting toxicity, the pharmacokinetics, and the activity of E7070, a novel cell-cycle inhibitor.

PATIENTS AND METHODS

E7070 was given as a 1-hour intravenous infusion every 3 weeks in two groups of patients with advanced solid tumors who met prespecified eligibility criteria (group A) or who met the same eligibility criteria but in addition were less heavily pretreated and had more favorable liver functions (group B).

RESULTS

Forty patients (31 patients in group A and nine patients in group B) were entered. Dose escalation proceeded through eight levels (range, 50 to 1,000 mg/m(2)). In group A, neutropenia and thrombocytopenia were dose-limiting toxicities occurring during the first cycle in two of seven patients treated at the doses of 700 mg/m(2) and two of four patients treated at 800 mg/m(2). Identical dose-limiting toxicities were observed in zero of six and two of three patients from group B at doses of 800 and 1,000 mg/m(2), respectively. Other toxicities included acne-like skin eruption, mucositis, conjunctivitis, nausea, fatigue, and alopecia. At doses greater than 400 mg/m(2), the area under the concentration-time curve increased disproportionately to the administered dose. Tumor stabilization lasting > or = 6 months was observed in six assessable patients.

CONCLUSION

The recommended doses of E7070 in this schedule were 700 mg/m(2) (group A) and 800 mg/m(2) in patients who were less heavily pretreated (group B) with a moderate tumor burden. Prolonged disease stabilization observed in this study might warrant further investigation of E7070 in selected tumor types.