Phase II trial of escalated dose of tirapazamine combined with cisplatin in advanced malignant melanoma

Bioreductive drugs: from concept to clinic

One of the key issues for radiobiologists is the importance of hypoxia to the radiotherapy response. This review addresses the reasons for this and primarily focuses on one aspect, the development of bioreductive drugs that are specifically designed to target hypoxic tumour cells. Four classes of compound have been developed since this concept was first proposed: quinones, nitroaromatics, aliphatic and heteroaromatic N-oxides. All share two characteristics: (1) they require hypoxia for activation and (2) this activation is dependent on the presence of specific reductases. The most effective compounds have shown the ability to enhance the anti-tumour efficacy of agents that kill better-oxygenated cells, i.e. radiation and standard cytotoxic chemotherapy agents such as cisplatin and cyclophosphamide. Tirapazamine (TPZ) is the most widely studied of the lead compounds. After successful pre-clinical in vivo combination studies it entered clinical trial; over 20 trials have now been reported. Although TPZ has enhanced some standard regimens, the results are variable and in some combinations toxicity was enhanced. Banoxantrone (AQ4N) is another agent that is showing promise in early phase I/II clinical trials; the drug is well tolerated, is known to locate in the tumour and can be given in high doses without major toxicities. Mitomycin C (MMC), which shows some bioreductive activation in vitro, has been tested in combination trials. However, it is difficult to assign the enhancement of its effects to targeting of the hypoxic cells because of the significant level of its hypoxia-independent toxicity. More specific analogues of MMC, e.g. porfiromycin and apaziquone (EO9), have had variable success in the clinic. Other new drugs that have good pre-clinical profiles are PR 104 and NLCQ-1; data on their clinical safety/efficacy are not yet available. This paper reviews the pre-clinical data and discusses the clinical studies that have been reported.

Phase II study of tirapazamine plus cisplatin in patients with advanced or recurrent cervical cancer

The aim of this study was to evaluate the activity and toxicity of a tirapazamine (TPZ)/cisplatin drug combination in patients with stage IV or recurrent cervical cancer. The chemotherapy was administered for a maximum of eight cycles every 21 days. TPZ was administered intravenously at 330 mg/m(2) over a 2-h infusion, followed 1 h later by cisplatin intravenously at 75 mg/m(2) over 1 h on day 1. All patients received antiemetics including dexamethasone, ondansetron, and lorazepam. Subsequent doses were unchanged, reduced, or omitted according to observed toxicity and protocol guidelines. Response evaluation was performed every two cycles. Thirty-six patients with stage IV or recurrent cervical cancer were treated. Ninety-four percent of patients had prior radiotherapy. Two patients had prior chemotherapy. There were two complete responses and eight partial responses (27.8%). An additional 11 patients (30.6%) had stable disease as their best response. Response rate was greater in tumors outside of the previously radiated field (44.4% vs 11.1%). The median time to progression was 32.7 weeks. The most frequent grade 3 or 4 adverse events were nausea, vomiting, and fatigue, which occurred in 30.6%, 25%, and 22% of subjects, respectively. Anemia was the most frequent grade 3 or 4 hematologic toxicity at 8.3%. We conclude that the combination of cisplatin and TPZ was reasonably well tolerated in patients with recurrent or advanced cervical cancer. Further evaluation of this drug combination may be warranted.

Large-Scale Analysis of Genes that Alter Sensitivity to the Anticancer Drug Tirapazamine inSaccharomyces cerevisiae

Tirapazamine (TPZ) is an anticancer drug that targets topoisomerase II. TPZ is preferentially active under hypoxic conditions. The drug itself is not harmful to cells; rather, it is reduced to a toxic radical species by an NADPH cytochrome P450 oxidoreductase. Under aerobic conditions, the toxic compound reacts with oxygen to revert back to TPZ and a much less toxic radical species. We have used yeast (Saccharomyces cerevisiae) as a model to better understand the mechanism of action of TPZ. Overexpression of NCP1, encoding the yeast ortholog of the human P450 oxidoreductase, results in greatly increased sensitivity to TPZ. Likewise, overexpression of TOP2 (encoding topoisomerase II) leads to hypersensitivity to TPZ, suggesting that topoisomerase II is also a target of TPZ in yeast. Thus, our data show that yeast mimics human cells in terms of TPZ sensitivity. We have performed robot-aided screens for altered sensitivity to TPZ using a collection of approximately 4600 haploid yeast deletion strains. We have identified 117 and 73 genes whose deletion results in increased or decreased resistance to TPZ, respectively. For example, cells lacking various DNA repair genes are hypersensitive to TPZ. In contrast, deletion of genes encoding some amino acid permeases results in cells that are resistant to TPZ. This suggests that permeases may be involved in intracellular uptake of TPZ. Our discoveries in yeast may lead to a better understanding of TPZ biology in humans.

Tirapazamine with Cisplatin and Vinorelbine in Patients with Advanced Non–Small-Cell Lung Cancer: A Phase I/II Study

This phase I/II study was conducted to evaluate the safety and efficacy of tirapazamine in combination with cisplatin and vinorelbine for patients with advanced-stage IIIB/IV chemonaive non-small-cell lung cancer. Seventy patients with a Karnofsky performance status of > or = 60% were included. In the phase I part of the study, 21 patients were treated on day 1 with tirapazamine (escalating doses of 260, 330, or 390 mg/m(2)), cisplatin (75 or 100 mg/m(2)), and vinorelbine (25 or 30 mg/m(2)) for a maximum of 6 cycles every 4 weeks. Vinorelbine was repeated every week. In the phase II part of the study, 49 patients were treated on day 1 with tirapazamine 390 mg/m(2), cisplatin 100 mg/m(2), and vinorelbine 30 mg/m(2). The maximum tolerated dose was not reached. Muscle cramps, vomiting, nausea, tinnitus, neutropenia, and diarrhea were the most frequently reported adverse events in the phase I part of the study. Most of these events were grade 1 or 2. In the phase II part of the study, response rate was 47%, and median survival was 50 weeks. The most frequently reported adverse event was neutropenia. Asthenia, fever, anemia, vomiting, weight decrease, nausea, and muscle cramps were also noted. For patients treated at the maximum dose, dose reductions occurred 14% of tirapazamine cycles and in 4% of cisplatin cycles. The median number of cycles was 3. This regimen has a manageable toxicity profile. Response rate and median survival suggest that this combination might be more active than the cisplatin/vinorelbine combination. This triplet is currently being evaluated in a phase III study.

Extravascular Transport of Drugs in Tumor Tissue: Effect of Lipophilicity on Diffusion of Tirapazamine Analogues in Multicellular Layer Cultures

The extravascular diffusion of antitumor agents is a key determinant of their therapeutic activity, but the relationships between physicochemical properties of drugs and their extravascular transport are poorly understood. It is well-known that drug lipophilicity plays an important role in transport across biological membranes, but the net effect of lipophilicity on transport through multiple layers of tumor cells is less clear. This study examines the influence of lipophilicity (measured as the octanol-water partition coefficient P) on the extravascular transport properties of the hypoxic cytotoxin tirapazamine (TPZ, 1) and a series of 13 neutral analogues, using multicellular layers (MCLs) of HT29 human colon carcinoma cells as an in vitro model for the extravascular compartment of tumors. Flux of drugs across MCLs was determined using diffusion chambers, with the concentration-time profile on both sides of the MCL measured by HPLC. Diffusion coefficients in the MCLs (D(MCL)) were inversely proportional to M(r)(0.5) (M(r), relative molecular weight), although this was a minor contributor to differences between compounds over the narrow M(r) range investigated. Differences in lipophilicity had a larger effect, with a sigmoidal dependence of D(MCL) on log P. Correcting for M(r) differences, lipophilic compounds (log P > 1.5) had ca. 15-fold higher D(MCL) than hydrophilic compounds (log P < -1). Using a pharmacokinetic/pharmacodynamic (PK/PD) model in which diffusion in the extravascular compartment of tumors is considered explicitly, we demonstrated that hypoxic cell kill is very sensitive to changes in extravascular diffusion coefficient of TPZ analogues within this range. This study shows that simple monosubstitution of TPZ can alter log P enough to markedly improve extravascular transport and activity against target cells, especially if rates of metabolic activation are also optimized.

Phase I Trial of Tirapazamine and Cyclophosphamide in Children With Refractory Solid Tumors: A Pediatric Oncology Group Study

Purpose

To determine the dose limiting toxicity (DLT), maximum-tolerated dose (MTD), and pharmacokinetic profile of tirapazamine (Sanofi Synthelabo Research, Malvern, PA) combined with cyclophosphamide in children with recurrent solid tumors.

Patients and Methods

Patients received a 2-hour infusion of tirapazamine, followed by 1,500 mg/m2 cyclophosphamide, and mesna once every 3 weeks. Dose escalation of tirapazamine began at 250 mg/m2 and was increased by 30% in subsequent cohorts. If DLT was hematologic, less-heavily pretreated patients were to be enrolled until their DLTs were encountered, and MTDs defined. Pharmacokinetic profiles were also characterized.

Results

Twenty-three patients were enrolled onto the study. Pharmacokinetic data were calculated for 22 patients. Prolonged neutropenia was the DLT at 420 mg/m2 in heavily pretreated patients. Grade 3, reversible ototoxicity was the DLT in less-heavily pretreated patients at 420 mg/m2. Two (one with neuroblastoma and one with rhabdomyosarcoma) had partial responses. One child with neuroblastoma had prolonged stable disease (10 cycles) at a dose of 250 mg/m2. This patient had disease detectable in the bone marrow only and all evidence of bone marrow involvement resolved for 17 cycles of therapy. Four other patients had stable disease. An apparent dose-proportional increase in tirapazamine maximal concentration and area under the curvelast was observed. Tirapazamine clearance, volume of distribution at steady-state, and terminal half-life did not appear to be dose-dependent.

Conclusion

The recommended dose of tirapazamine given with 1,500 mg/m2 of cyclophosphamide once every 3 weeks is 325 mg/m2. Neutropenia and ototoxicity were dose-limiting. Based on early evidence of antitumor activity, additional studies appear warranted.

Hypoxic pelvic and limb perfusion with melphalan and mitomycin C for recurrent limb melanoma: a pilot study

Hypoxic pelvic and limb perfusion by means of a balloon occlusion technique was evaluated in patients with recurrent melanoma of the lower limbs who were non-responders to isolated hyperthermic limb perfusion or who were not eligible for this procedure. A pilot study was performed in 17 patients, who underwent hypoxic pelvic and limb perfusion with 50 mg/m(2) of melphalan or 50 mg/m(2) of melphalan and 25 mg/m(2) of mitomycin C. Each procedure was followed by haemofiltration. A leakage monitoring study was performed in five of the 17 patients. The response rate and time to disease progression were the primary endpoints, with overall survival as the secondary endpoint. During the procedures there were no technical, haemodynamic or vascular complications, and no deaths occurred during surgery or in the postoperative period. Significant leakage (median 40%) was measured in the five patients studied. No severe systemic or regional toxicity was observed. After one course of treatment, the objective response rate was 47% (95% confidence interval 22.5-71.5%), the median time to disease progression was 10 months (range 2-40 months), and the 3 year overall survival was 20%. Hypoxic pelvic and limb perfusion seems to be a safe and effective treatment for patients with unresectable recurrent limb melanoma who are not eligible for isolated hyperthermic limb perfusion. Due to the non-homogeneity of the study, with some patients receiving a combination of melphalan and mitomycin C and others receiving only melphalan, it is not possible to make definite conclusions with regard to efficacy. Further studies are necessary to establish whether the response rates can be improved by using different drug regimens.

Systemic chemotherapy for the treatment of metastatic melanoma

The role of systemic chemotherapy in the treatment of patients with metastatic melanoma remains of questionable benefit. Despite encouraging phase II data from multiple institutions that suggested an improved overall response rate for patients treated with the Dartmouth regimen, recently completed phase III trials have failed to demonstrate a significant benefit in survival. Of concern is the fact that there have been relatively few new chemotherapeutic agents in the past several years that have demonstrated any activity in this disease. More recently there has been a shift away from combination chemotherapy to biochemotherapy. However, this approach has yet to be clearly defined as superior. The basis for optimism in the future in this field resides in the realm of molecular oncology. As mechanisms of resistance are identified, new molecules such as antisense oligonucleotides may provide the basis for increasing the sensitivity of melanoma to chemotherapeutic and/or immunotherapeutic treatments.

Deliberate hypoxic pelvic and limb chemoperfusion in the treatment of recurrent melanoma

BACKGROUND

The treatment of patients with advanced or recurrent pelvic melanoma, which are often associated with lesions in the lower limbs, is still unsatisfactory and controversial. A simplified hypoxic pelvic and limb perfusion has been recently recommended to provide therapeutic options for palliation and possibly cure.

METHODS

A nonrandomized and noncontrolled phase II experimental study was performed in 11 patients with symptomatic unresectable recurrent melanoma of the pelvis and limb. Patients were submitted to hypoxic pelvic and limb perfusion with 25 mg/m(2) of melphalan, 50 mg/m(2) of cisplatin, 300 mg/m(2) of dacarbazine, and 75 mg/m(2) of epirubicin by means of a simplified balloon occlusion technique. Response rate and time to disease progression were the primary endpoints; overall survival was the secondary endpoint.

RESULTS

During the procedures there were no technical, hemodynamic, or vascular complications, and no deaths occurred during surgery or in the postoperative period. Response rate was 82% (95% confidence interval, 58% to 100%). Median time to disease progression was 12 months (range 9 to 30 months). Three-year overall survival was 34%.

CONCLUSIONS

Hypoxic pelvic and limb perfusion is a safe and good palliative treatment for patients with unresectable recurrent melanoma. Further studies are necessary to to confirm these data and to establish if refinements can be made with acceptable toxicity.