Response of multiple recurrent TaT1 bladder cancer to intravesical apaziquone (EO9): comparative analysis of tumor recurrence rates

Evaluation of toxicities for intravesical drugs in phase 1 bladder cancer trials

BACKGROUND

Improving clinical trial design is important for optimizing approval of safe and effective drugs. Phase 1 clinical trials seek to determine phase 2 doses by investigating predefined dose-limiting toxicities. Traditional definitions of dose-limiting toxicity may not be applicable to intravesical therapies for bladder cancer. This study compared the frequency of dose-limiting toxicities and serious adverse events in bladder cancer trials for intravesical therapies to other routes of administration.

METHODS

Studies were abstracted from ClinicalTrials.gov and reconciled with a PubMed search. Primary and secondary end points were predefined before data abstraction, and the primary end point was subject-level dose-limiting toxicity rate. Fisher exact tests were performed with p < .05 designated as significant.

RESULTS

Eighteen intravesical studies and 24 studies with other routes of administration (the per os/intravenous/intramuscular [PO/IV/IM] group) were identified. Dose-limiting toxicities were reported in 38.9% of intravesical studies, affecting 3.29% of subjects, compared with 30.0% of PO/IV/IM studies representing 4.19% of subjects (p = .52 for study-level and p = .60 for subject-level comparisons). Serious adverse events occurred in 53.9% of intravesical studies in 10.3% of subjects versus 91.0% of studies reporting serious adverse events affecting 41.4% of subjects in the PO/IV/IM group (p = .03 for subject-level and p < .0001 for study-level comparisons).

CONCLUSIONS

There was no difference in subject-level dose-limiting toxicity rate between intravesical and PO/IV/IM bladder cancer trials. The serious adverse event rate was lower in the intravesical group. Heterogeneity of dose-limiting toxicity definition may affect interpretation of toxicity in phase 1 bladder cancer clinical trials studying different routes of administration.

LAY SUMMARY

Bladder cancer is a common cancer type that may be treated with therapies that are instilled into the bladder and act locally, called intravesical therapies. This study used publicly available regulatory data from early phase clinical trials to determine whether measures of tolerability used in clinical trials are applicable to intravesical therapies for bladder cancer.

Inactivation of apaziquone by haematuria: implications for the design of phase III clinical trials against non-muscle invasive bladder cancer

Purpose

Despite positive responses in phase II clinical trials, the bioreductive prodrug apaziquone failed to achieve statistically significant activity in non-muscle invasive bladder cancer in phase III trials. Apaziquone was administered shortly after transurethral resection and here we test the hypothesis that haematuria inactivates apaziquone.

Methods

HPLC analysis was used to determine the ability of human whole blood to metabolise apaziquone ex vivo. An in vitro model of haematuria was developed and the response of RT112 and EJ138 cells following a 1-h exposure to apaziquone was determined in the presence of urine plus or minus whole blood or lysed whole blood.

Results

HPLC analysis demonstrated that apaziquone is metabolised by human whole blood with a half-life of 78.6 ± 23.0 min. As a model for haematuria, incubation of cells in media containing up to 75% buffered (pH 7.4) urine and 25% whole blood was not toxic to cells for a 1-h exposure period. Whole blood (5% v/v) significantly (p < 0.01) reduced the potency of apaziquone in this experimental model. Lysed whole blood also significantly (p < 0.05) reduced cell growth, although higher concentrations were required to achieve an effect (15% v/v).

Conclusions

The results of this study demonstrate that haematuria can reduce the potency of apaziquone in this experimental model. These findings impact upon the design of further phase III clinical trials and strongly suggest that apaziquone should not be administered immediately after transurethral resection of non-muscle invasive bladder cancer when haematuria is common.

Total synthesis of natural productsviairidium catalysis

An overview of the highlights in total synthesis of natural products using iridium as a catalyst is given.

Efficacy, pharmacokinetic and pharmacodynamic evaluation of apaziquone in the treatment of non-muscle invasive bladder cancer

INTRODUCTION

Apaziquone (also known as EO9 and Qapzola^TM) is a prodrug that is activated to DNA damaging species by oxidoreductases (particularly NQO1) and has the ability to kill aerobic and/or hypoxic cancer cells. Areas covered: Whilst its poor pharmacokinetic properties contributed to its failure in phase II clinical trials when administered intravenously, these properties were ideal for loco-regional therapies. Apaziquone demonstrated good anti-cancer activity against non-muscle invasive bladder cancer (NMIBC) when administered intravesically to marker lesions and was well tolerated with no systemic side effects. However, phase III clinical trials did not reach statistical significance for the primary endpoint of 2-year recurrence in apaziquone over placebo although improvements were observed. Post-hoc analysis of the combined study data did indicate a significant benefit for patients treated with apaziquone, especially when the instillation of apaziquone was given 30 min or more after surgery. A further phase III study is ongoing to test the hypotheses generated in the unsuccessful phase III studies conducted to date. Expert opinion: Because of its specific pharmacological properties, Apaziquone is excellently suited for local therapy such as NMIBC. Future studies should include proper biomarkers.

Targeting the hypoxic fraction of tumours using hypoxia-activated prodrugs

The presence of a microenvironment within most tumours containing regions of low oxygen tension or hypoxia has profound biological and therapeutic implications. Tumour hypoxia is known to promote the development of an aggressive phenotype, resistance to both chemotherapy and radiotherapy and is strongly associated with poor clinical outcome. Paradoxically, it is recognised as a high-priority target and one of the therapeutic strategies designed to eradicate hypoxic cells in tumours is a group of compounds known collectively as hypoxia-activated prodrugs (HAPs) or bioreductive drugs. These drugs are inactive prodrugs that require enzymatic activation (typically by 1 or 2 electron oxidoreductases) to generate cytotoxic species with selectivity for hypoxic cells being determined by (1) the ability of oxygen to either reverse or inhibit the activation process and (2) the presence of elevated expression of oxidoreductases in tumours. The concepts underpinning HAP development were established over 40 years ago and have been refined over the years to produce a new generation of HAPs that are under preclinical and clinical development. The purpose of this article is to describe current progress in the development of HAPs focusing on the mechanisms of action, preclinical properties and clinical progress of leading examples.

Targeting the hypoxic fraction of tumours using hypoxia-activated prodrugs

The presence of a microenvironment within most tumours containing regions of low oxygen tension or hypoxia has profound biological and therapeutic implications. Tumour hypoxia is known to promote the development of an aggressive phenotype, resistance to both chemotherapy and radiotherapy and is strongly associated with poor clinical outcome. Paradoxically, it is recognised as a high-priority target and one of the therapeutic strategies designed to eradicate hypoxic cells in tumours is a group of compounds known collectively as hypoxia-activated prodrugs (HAPs) or bioreductive drugs. These drugs are inactive prodrugs that require enzymatic activation (typically by 1 or 2 electron oxidoreductases) to generate cytotoxic species with selectivity for hypoxic cells being determined by (1) the ability of oxygen to either reverse or inhibit the activation process and (2) the presence of elevated expression of oxidoreductases in tumours. The concepts underpinning HAP development were established over 40 years ago and have been refined over the years to produce a new generation of HAPs that are under preclinical and clinical development. The purpose of this article is to describe current progress in the development of HAPs focusing on the mechanisms of action, preclinical properties and clinical progress of leading examples.

Antitumour indolequinones: synthesis and activity against human pancreatic cancer cells

An important determinant of the growth inhibitory activity of indolequinones against pancreatic cancer cells is substitution on the 2-position with 2-unsubstituted derivatives being markedly more potent. A series of indolequinones bearing a range of substituents on nitrogen and at the indolylcarbinyl position was prepared by copper(II)-mediated reaction of bromoquinones and enamines, followed by functional group interconversions. The compounds were then assayed for their ability to inhibit the growth of pancreatic cancer cells. The pKa of the leaving group at the 3-position was shown to influence growth inhibitory activity that is consistent with the proposed mechanism of action of reduction, loss of leaving group and formation of a reactive iminium species. Substitutions on the indole nitrogen were well tolerated with little influence on growth inhibitory activity while substitutions at the 5- and 6-positions larger than methoxy led to decreased activity. The studies presented define the range of substitutions of 2-unsubstituted indolequinones required for optimal growth inhibitory activity.

Expert review: an update in current and developing intravesical therapies for non-muscle-invasive bladder cancer

Non-muscle-invasive bladder cancer is a highly prevalent disease and recurrences, after initial therapy, are common. Consequently, the healthcare costs for non-muscle-invasive bladder cancer are high. Despite a primary adequate response to adjuvant intravesical treatment, many patients suffer from recurrences, and some even from progression. To date, cystectomy remains the only option for those non-responding patients with high risk of recurrence and progression. Mainly because outcome after progression, in this group, is poor. Therefore, new intravesical therapies are needed. Moreover, new accurate and individual parameters, to distinguish responder from non-responders, will provide additional benefit in clinical decision-making. In this review, current diagnostics and therapies will be discussed. In addition, we will elucidate developing therapies in non-muscle-invasive bladder cancer.

EO9 (Apaziquone): from the clinic to the laboratory and back again

EO9 (Apaziquone) is a bioreductive drug that has a chequered history. It underwent clinical trial but failed to show activity in phase II clinical trials when administered i.v. Poor drug delivery to tumours caused by a combination of rapid pharmacokinetic elimination and poor penetration through avascular tissue were the major factors responsible for EO9's poor efficacy. Based upon an understanding of why EO9 failed, a further clinical trial against patients with superficial transitional cell carcinoma of the bladder was conducted. The rationale for this was that intravesical administration directly into the bladder would circumvent the drug delivery problem, and any drug reaching the blood supply would be rapidly cleared thereby reducing the risk of systemic exposure. EO9 was well tolerated, and clinical activity against marker lesions was recorded in both phase I and II clinical trials. This article charts the pharmacological history of EO9 and discusses the potential implications that 'the EO9 story' has for the development of other loco-regional therapies.

Copper(II)-Mediated Synthesis of Indolequinones from Bromoquinones and Enamines

The reaction of enamines and bromoquinones in the presence of copper(II) acetate and potassium carbonate results in a regiospecific synthesis of indolequinones. The reaction is broad in scope and scalable and provides a route to the core structure that is present in several biologically interesting natural and synthetic compounds.

Perioperative chemotherapy: when to use it, what to use, and why

This article provides an overview of intravesical chemotherapy agents used for non-muscle invasive bladder cancer; summarizes the evidence on single-dose perioperative administration, induction therapy, and maintenance therapy; and briefly discusses ongoing research.

Best practice in the treatment of nonmuscle invasive bladder cancer

Bladder carcinoma is the most common malignancy of the urinary tract. Approximately 75-85% of patients with bladder cancer present with a disease that is confined to the mucosa (stage Ta, carcinoma in situ) or submucosa (stage T1). These categories are grouped as nonmuscle invasive bladder cancer (NMIBC). Although the management of NMIBC tumours has significantly improved during the past few years, it remains difficult to predict the heterogeneous outcome of such tumours, especially if high-grade NMIBC is present. Transurethral resection is the initial treatment of choice for NMIBC. However, the high rates of recurrence and significant risk of progression in higher-grade tumours mandate additional therapy with intravesical agents. We discuss the role of various intravesical agents currently in use, including the immunomodulating agent bacillus Calmette-Guérin (BCG) and chemotherapeutic agents. We also discuss the current guidelines and the role of these therapeutic agents in the context of higher-grade Ta and T1 tumours. Beyond the epidemiology, this article focuses on the risk factors, classification and diagnosis, the prediction of recurrence and progression in NMIBC, and the treatments advocated for this invasive disease.

One-pot synthesis of benzo[f]indole-4,9-diones from 1,4-naphthoquinones and terminal acetylenes

In this paper, a concise one-pot method for the construction of benzo[f]indole-4,9-dione motifs is described. These transformations proceed via a sequential palladium- and copper-catalyzed coupling reaction of 1,4-naphthoquinones with terminal acetylenes, followed by a copper-catalyzed intramolecular cyclization reaction of the resulting coupling product.

Six degrees of separation: the oxygen effect in the development of radiosensitizers

The popular theory six degrees of separation is used in this review as an analogy to relate all radiosensitization to oxygen. As the prime mover of all radiosensitizers, the pervasive influence of oxygen has consciously or unconsciously influenced the direction of research and development and provided the benchmark against which all other compounds and approaches are measured. It is the aim of this review to develop the six degrees of separation from oxygen analogy as a unifying framework for conceptually organizing the field and for giving context to its varied subspecializations and theories. Under such a framework, it would become possible for one area to consider questions and problems found in other areas of radiosensitization, using a common analogy, that would allow for further development and unification of this multifaceted discipline. In this review, approaches to the development of radiosensitizers and the current state of research in this field are discussed, including promising new agents in various stages of clinical development.

Targeting hypoxia in cancer therapy

Hypoxia is a feature of most tumours, albeit with variable incidence and severity within a given patient population. It is a negative prognostic and predictive factor owing to its multiple contributions to chemoresistance, radioresistance, angiogenesis, vasculogenesis, invasiveness, metastasis, resistance to cell death, altered metabolism and genomic instability. Given its central role in tumour progression and resistance to therapy, tumour hypoxia might well be considered the best validated target that has yet to be exploited in oncology. However, despite an explosion of information on hypoxia, there are still major questions to be addressed if the long-standing goal of exploiting tumour hypoxia is to be realized. Here, we review the two main approaches, namely bioreductive prodrugs and inhibitors of molecular targets upon which hypoxic cell survival depends. We address the particular challenges and opportunities these overlapping strategies present, and discuss the central importance of emerging diagnostic tools for patient stratification in targeting hypoxia.

Optimal timing of radical cystectomy in T1 high-grade bladder cancer

T1 high-grade (formerly T1G3) bladder cancer is a challenging clinical entity representing approximately 10-15% of all new bladder cancer cases. The variable natural history of the disease and possible impairment in quality of life associated with radical treatment makes T1 high-grade one of the most challenging uro-oncological patient groups to manage. In particular, the risk of clinical understaging and not recognizing muscle-invasive disease may have detrimental effects on patient outcome. The cornerstone of contemporary staging is restaging transurethral resection (TUR), which helps in defining further management. In patients with restaging TUR stage less than T1, induction bacillus Calmette-Guérin combined with maintenance offers good results. The option of radical cystectomy should be discussed with patients with restaging TUR stage T1 or higher and it is highly recommended to all patients with recurrent T1 of carcinoma in situ during bacillus Calmette-Guérin maintenance. In addition to restaging TUR stage, several other clinicopathological factors, such T1 substaging, associated carcinoma in situ, tumor size and appearance, lymphovascular invasion, and hydronephrosis, aid in the decision making between radical and conservative treatment. Future prospects include improved staging and molecular markers that may guide toward conservative therapy or allow more cT1 patients to be offered nerve-sparing cystectomies and neobladders and, thus, improving quality of life for patients undergoing radical surgery.

Hypoxia-activated prodrugs in cancer therapy: progress to the clinic

The hypoxic cells common in solid tumors (because of their inefficient blood supply) limit the effectiveness of radiotherapy and many cytotoxic drugs. Nontoxic prodrugs that generate active species in hypoxic tissue by selective bioreduction have long been explored, and the first examples, representing a variety of different chemistries, have now reached advanced clinical trials. In the process, a great deal has been learnt about the properties that such drugs require to be successful, notably, efficient extravascular diffusion, appropriate reduction chemistry and kinetics, and an effective biological profile of the activated species, including a good bystander effect. The critical importance of prodrug diffusion and techniques to quantify this have assisted the development of models to predict the killing of tumor cells, which promises to help accelerate new drug evaluation. A cell cycle-independent mechanism of killing by the released cytotoxin is also a potential advantage, although it is likely that much of the killing will be when out-of-cycle hypoxic cells reoxygenate and resume division.

Investigational therapies for non-muscle invasive bladder cancer

IMPORTANCE OF THE FIELD

Bacillus Calmette-Guérin (BCG) is currently the most effective adjuvant intravesical agent at preventing disease recurrence and the only therapy shown to inhibit disease progression in non-muscle invasive bladder cancer (NMIBC). However, recurrence rates as high as 30% and significant local/systemic toxicity have resulted in an increased interest in the use of alternative intravesical agents.

AREAS COVERED IN THE REVIEW

Our aim is to discuss recent clinical trial evidence utilizing novel intravesical agents for treatment of NMIBC. A systematic literature review was performed via the National Center for Biotechnology Information databases to identify pertinent studies from 2000-2009.

WHAT THE READER WILL GAIN

A durable response has been demonstrated with alternative agents in patients refractory to or intolerant of BCG. This review compares the merits and shortcomings of these emerging agents, focusing on clinical trial safety and efficacy results.

TAKE HOME MESSAGE

Despite recent enthusiasm for novel agents, radical cystectomy remains the treatment of choice for patients with NMIBC who have failed intravesical therapy. However, evidence is accumulating that novel agents provide an efficacious alternative in patients refractory or intolerable to BCG or unfit for cystectomy. Further randomized prospective data are required to demonstrate a recurrence- and progression-free benefit compared with BCG.

Definition and management of patients with bladder cancer who fail BCG therapy

Intravesical administration of bacillus Calmette-Guérin (BCG) following resection of non-muscle-invasive bladder tumor is the current 'gold standard'. However, up to 40% of patients will fail therapy within the first year and response rates to salvage intravesical therapy after appropriate trial of BCG (i.e., after induction and one maintenance course) average 15-20% at 1 year. Radical cystectomy remains the only treatment with proven long-term benefit after BCG failure. Nonetheless, with appropriate selection, certain patients who 'fail' BCG (but have other favorable risk factors, e.g., a long interval between BCG and recurrence) can be managed with intravesical regimens including repeated BCG, BCG plus cytokines and/or intravesical chemotherapy. In this review, optimal risk stratification, appropriate definitions and management of BCG failures are discussed.

Two-year follow-up of the phase II marker lesion study of intravesical apaziquone for patients with non-muscle invasive bladder cancer

OBJECTIVES

To study the time-to-recurrence and duration of response in non-muscle invasive bladder cancer (NMIBC) patients, with a complete ablative response after intravesical apaziquone instillations.

METHODS

Transurethral resection of bladder tumour(s) (TURBT) was performed in patients with multiple pTa-T1 G1-2 urothelial cell carcinoma (UCC) of the bladder, with the exception of one marker lesion of 0.5-1.0 cm. Intravesical apaziquone was administered at weekly intervals for six consecutive weeks, without maintenance instillations. A histological confirmed response was obtained 2-4 weeks after the last instillation. Routine follow-up (FU) was carried out at 6, 9, 12, 18 and 24 months from the first apaziquone instillation.

RESULTS

At 3 months FU 31 of 46 patients (67.4%) had a complete response (CR) to ablative treatment. Side-effects on the long-term were only mild. Two CR patients dropped out during FU. On intention-to-treat (ITT) analysis 49.5% of the CR patients were recurrence-free at 24 months FU, with a median duration of response of 18 months. Of 15 no response (NR) patients, only two received additional prophylactic instillations after TURBT. On ITT-analysis 26.7% of the NR patients were recurrence-free (log rank test, P = 0.155). The overall recurrence-free survival was 39% (18 of 46 patients) at 24 months FU.

CONCLUSIONS

The CR of the marker lesion in 67% of patients was followed by a recurrence-free rate of 56.5% at 1-year FU, and 49.5% at 2-year FU. These long-term results are good in comparison with the results of other ablative studies.