In vivo activation of the hypoxia-targeted cytotoxin AQ4N in human tumor xenografts.

AQ4N (banoxantrone) is a prodrug that, under hypoxic conditions, is enzymatically converted to a cytotoxic DNA-binding agent, AQ4. Incorporation of AQ4N into conventional chemoradiation protocols therefore targets both oxygenated and hypoxic regions of tumors, and potentially will increase the effectiveness of therapy. This current pharmacodynamic and efficacy study was designed to quantify tumor exposure to AQ4 following treatment with AQ4N, and to relate exposure to outcome of treatment. A single dose of 60 mg/kg AQ4N enhanced the response of RT112 (bladder) and Calu-6 (lung) xenografts to treatment with cisplatin and radiation therapy. AQ4N was also given to separate cohorts of tumor-bearing mice 24 hours before tumor excision for subsequent analysis of metabolite levels. AQ4 was detected by high performance liquid chromatography/mass spectrometry in all treated samples of RT112 and Calu-6 tumors at mean concentrations of 0.23 and 1.07 microg/g, respectively. These concentrations are comparable with those shown to be cytotoxic in vitro. AQ4-related nuclear fluorescence was observed in all treated tumors by confocal microscopy, which correlated with the high performance liquid chromatography/mass spectrometry data. The presence of the hypoxic marker Glut-1 was shown by immunohistochemistry in both Calu-6 tumors and RT112 tumors, and colocalization of AQ4 fluorescence and Glut-1 staining strongly suggested that AQ4N was activated in these putatively hypoxic areas. This is the first demonstration that AQ4N will increase the efficacy of chemoradiotherapy in preclinical models; the intratumoral levels of AQ4 found in this study are comparable with tumor AQ4 levels found in a recent phase I clinical study, which suggests that these levels could be potentially therapeutic.

Hypoxia-selective targeting by the bioreductive prodrug AQ4N in patients with solid tumors: results of a phase I study.

PURPOSE: AQ4N is a novel bioreductive prodrug under clinical investigation. Preclinical evidence shows that AQ4N penetrates deeply within tumors and undergoes selective activation to form AQ4, a potent topoisomerase II inhibitor, in hypoxic regions of solid tumors. This proof-of-principle, phase I study evaluated the activation, hypoxic selectivity, and safety of AQ4N in patients with advanced solid tumors. EXPERIMENTAL DESIGN: Thirty-two patients with cancer (8 glioblastoma, 9 bladder, 8 head and neck, 6 breast, and 1 cervix) received a single 200 mg/m(2) dose of AQ4N before elective surgery. AQ4 and AQ4N levels in 95 tissues (tumor, healthy tissue) were assessed by liquid chromatography-tandem mass spectrometry. Tissue sections were also analyzed for AQ4 fluorescence using confocal microscopy, and for expression of the hypoxia-regulated glucose transporter, Glut-1. RESULTS: Activated AQ4 was detected in all tumor samples with highest levels present in glioblastoma (mean 1.2 microg/g) and head and neck (mean 0.65 microg/g) tumors; 22 of 32 patients had tumor AQ4 concentrations > or = 0.2 microg/g, levels previously shown to be active in preclinical studies. In 24 of 30 tumor samples, AQ4 was detected at higher concentrations than in adjacent normal tissue (tumor to normal ratio range 1.1-63.6); distant skin samples contained very low concentrations of AQ4 (mean 0.037 microg/g). Microscopic evaluation of tumor sections revealed that AQ4 colocalized within regions of Glut-1+ hypoxic cells. CONCLUSIONS: AQ4N was activated selectively in hypoxic regions in human solid tumors. Intratumoral concentrations of AQ4 exceeded those required for activity in animal models and support the evaluation of AQ4N as a novel tumor-targeting agent in future clinical studies.

Randomized trial of the combination of lomeguatrib and temozolomide compared with temozolomide alone in chemotherapy naive patients with metastatic cutaneous melanoma.

PURPOSE: To evaluate tumor response, pharmacodynamic effects, and safety of a combination of lomeguatrib (LM), an O6-methylguanine DNA-methyltransferase (MGMT) inactivator, and temozolomide (TMZ), TMZ alone, and LM/TMZ after disease progression on TMZ alone in patients with advanced melanoma. PATIENTS AND METHODS: Patients with unresectable stage III or IV cutaneous melanoma who had no prior systemic chemotherapy were randomly assigned to receive either 40 to 80 mg LM and 125 mg/m2 TMZ or 200 mg/m2 TMZ on days 1 through 5 of each 28-day treatment cycle. Drugs were administered orally for up to six cycles of treatment. Patients on TMZ alone were offered LM/TMZ at progression, if fit enough to receive treatment. RESULTS: One hundred four patients were enrolled, with 52 in each trial arm. Twenty-seven TMZ-treated patients received LM/TMZ after progression on TMZ. Unexpectedly, analysis of tumor biopsies showed rapid recovery of MGMT after LM/TMZ with 40 mg/d LM. Therefore, doses of LM were escalated to 60 then 80 mg/d. Tumor response rates were 13.5% with LM/TMZ and 17.3% with TMZ alone. No patient responded to LM/TMZ having progressed through TMZ. Median time to disease progression was 65.5 days for LM/TMZ and 68 days for TMZ. All treatments were well tolerated, although hematologic and gastrointestinal adverse events were common. A higher incidence of hematological adverse events was observed in the LM/TMZ combination arm. CONCLUSION: The efficacy of LM and TMZ in the current dosing schedule is similar to that of TMZ alone. To maintain MGMT depletion in tumor dosing of LM needs to be continued beyond that of TMZ.

Virus-directed enzyme prodrug therapy: intratumoral administration of a replication-deficient adenovirus encoding nitroreductase to patients with resectable liver cancer.

PURPOSE: Virus-directed enzyme prodrug therapy depends on selective delivery of virus encoding a prodrug-activating enzyme to tumor, followed by systemic treatment with prodrug to achieve high levels of the activated cytotoxic at the intended site of action. The use of the bacterial enzyme nitroreductase to activate CB1954 (5-(aziridin-1-yl)-2,4-dinitrobenzamide) to a short lived, highly toxic DNA cross-linking agent has been demonstrated in tumor xenografts. In this study, we report the first clinical trial investigating the feasibility, safety, and transgene expression of a replication-defective adenovirus encoding nitroreductase (CTL102) in patients with liver tumors. PATIENTS AND METHODS: Patients with resectable primary or secondary (colorectal) liver cancer received a single dose of CTL102 delivered by direct intratumoral inoculation 3 to 8 days before surgical resection. RESULTS: Eighteen patients were treated with escalating doses of CTL102 (range, 10(8)-5 x 10(11) virus particles). The vector was well tolerated with minimal side effects, had a short half-life in the circulation, and stimulated a robust antibody response. Dose-related increases in tumoral nitroreductase expression measured by immunohistochemical analysis have been observed. CONCLUSION: Direct intratumoral inoculation of CTL102 to patients with primary and secondary liver cancer is feasible and well tolerated. The high level of nitroreductase expression observed at 1 to 5 x 10(11) virus particles mandates further studies in patients with inoperable tumors who will receive CTL102 and CB1954.