Novel thiosemicarbazones induce high toxicity in estrogen-receptor-positive breast cancer cells (MCF7) and exacerbate cisplatin effectiveness in triple-negative breast (MDA-MB231) and lung adenocarcinoma (A549) cells.

Cis-diamminedichloroplatinum(II) (CDDP), known as cisplatin, has been extensively used against breast cancer, which is the most frequent cancer among women, and lung cancer, the leading cancer that causes death worldwide. Novel compounds such as thiazole derivatives have exhibited antiproliferative activity, suggesting they could be useful against cancer treatment. Herein, we synthesized two novel thiosemicarbazones and an aldehyde to combine with CDDP to enhance efficacy against ER-positive breast MCF7 cancer cells, triple-negative/basal-B mammary carcinoma cells (MDA-MB231) and lung adenocarcinoma (A549) human cells. We synthesized 2,3,5,6-tetrafluoro-4-(2-mercaptoetanothiolyl)benzaldehyde (ALD), 5-[(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenyl)thio]-2-furaldehyde thiosemicarbazone (TSC1) and 5-[(4-(trifluoromethyl)phenyl)thio]-2-furaldehyde thiosemicarbazone (TSC2) and used them alone or in combination with subtoxic CDDP concentrations to evaluate cytotoxicity, cytoskeleton integrity and mitochondrial function. We found that none of the synthesized compounds improved CDDP activity against MCF7 cell cultures; however, TSC2 was effective in enhancing the cytotoxicity of CDDP against MDA-MB231 and A549 cancer cell cultures. We demonstrated that the cytotoxic effect is related to the TSC2 capacity to induce disruption in the cytoskeleton network and to decrease mitochondrial function.

Phase I trial of daily triapine in combination with cisplatin chemotherapy for advanced-stage malignancies.

PURPOSE: Advanced-stage malignancies have increased deoxyribonucleotide demands in DNA replication and repair, making deoxyribonucleotide supply a potential exploitable target for therapy based on ribonucleotide reductase (RNR) inhibition. METHODS: A dose-finding phase I trial was conducted of intravenous (i.v.) triapine, a small-molecule RNR inhibitor, and cisplatin chemotherapy in patients with advanced-stage solid tumor malignancies. Patients received dose-finding levels of i.v. triapine (48-96 mg/m2) and i.v. cisplatin (20-75 mg/m2) on 1 of 3 different schedules. The primary endpoint was to identify the maximum tolerated dose of a triapine-cisplatin combination. Secondary endpoints included the rate of triapine-cisplatin objective response and the pharmacokinetics and bioavailability of a single oral triapine dose. (Clinicaltrials.gov number, NCT00024323). RESULTS: The MTD was 96 mg/m2 triapine daily days 1-4 and 75 mg/m2 cisplatin split over day 2 and day 3. Frequent grade 3 or 4 adverse events included fatigue, dyspnea, leukopenia, thrombocytopenia, and electrolyte abnormalities. No objective responses were observed; 5 (50%) of 10 patients treated at the MTD had stable disease. Pharmacokinetics indicated an oral triapine bioavailability of 88%. CONCLUSIONS: The triapine-cisplatin combination may be given safely in patients with advanced-stage solid tumor malignancies. On the basis of these results, a phase I trial adequately powered to evaluate oral triapine bioavailability in women with advanced-stage uterine cervix or vulvar cancers is underway.

PAN-811 Blocks Chemotherapy Drug-Induced In Vitro Neurotoxicity, While Not Affecting Suppression of Cancer Cell Growth.

Chemotherapy often results in cognitive impairment, and no neuroprotective drug is now available. This study aimed to understand underlying neurotoxicological mechanisms of anticancer drugs and to evaluate neuroprotective effects of PAN-811. Primary neurons in different concentrations of antioxidants (AOs) were insulted for 3 days with methotrexate (MTX), 5-fluorouracil (5-FU), or cisplatin (CDDP) in the absence or presence of PAN-811·Cl·H2O. The effect of PAN-811 on the anticancer activity of tested drugs was also examined using mouse and human cancer cells (BNLT3 and H460) to assess any negative interference. Cell membrane integrity, survival, and death and intramitochondrial reactive oxygen species (ROS) were measured. All tested anticancer drugs elicited neurotoxicity only under low levels of AO and elicited a ROS increase. These results suggested that ROS mediates neurotoxicity of tested anticancer drugs. PAN-811 dose-dependently suppressed increased ROS and blocked the neurotoxicity when neurons were insulted with a tested anticancer drug. PAN-811 did not interfere with anticancer activity of anticancer drugs against BNLT3 cells. PAN-811 did not inhibit MTX-induced death of H460 cells but, interestingly, demonstrated a synergistic effect with 5-FU or CDDP in reducing cancer cell viability. Thus, PAN-811 can be a potent drug candidate for chemotherapy-induced cognitive impairment.

Improved cytotoxicity of pyridyl-substituted thiosemicarbazones against MCF-7 when used as metal ionophores.

Zinc is the second most abundant transition metal in the human body, between 3 and 10% of human genes encoding for zinc binding proteins. We have investigated the interplay of reactive oxygen species and zinc homeostasis on the cytotoxicity of the thiosemicarbazone chelators against the MCF-7 cell line. The cytotoxicity of thiosemicarbazone chelators against MCF-7 can be improved through supplementation of ionic zinc provided the zinc ion is at a level exceeding the thiosemicarbazone concentration. Elimination of the entire cell population can be accomplished with this regime, unlike the plateau of cytotoxicity observed on thiosemicarbazone monotherapy. The cytotoxic effects of copper complexes of the thiosemicarbazone are not enhanced by zinc supplementation, displacement of copper from the complex being disfavoured. Treatment of MCF-7 with uncomplexed thiosemicarbazone initiates post G1 blockade alongside the induction of apoptosis, cell death being abrogated through subsequent supplementation with zinc ion after drug removal. This would implicate a metal depletion mechanism in the cytotoxic effect of the un-coordinated thiosemicarbazone. The metal complexes of the species, however, fail to initiate similar G1 blockade and apparently exert their cytotoxic effect through generation of reactive oxygen species, suggesting that multiple mechanisms of cytotoxicity can be associated with the thiosemicarbazones dependant on the level of metal ion association.

Controlled administration of penicillamine reduces radiation exposure in critical organs during 64Cu-ATSM internal radiotherapy: a novel strategy for liver protection.

PURPOSE: (64)Cu-diacetyl-bis (N (4)-methylthiosemicarbazone) ((64)Cu-ATSM) is a promising theranostic agent that targets hypoxic regions in tumors related to malignant characteristics. Its diagnostic usefulness has been recognized in clinical studies. Internal radiotherapy (IRT) with (64)Cu-ATSM is reportedly effective in preclinical studies; however, for clinical applications, improvements to reduce radiation exposure in non-target organs, particularly the liver, are required. We developed a strategy to reduce radiation doses to critical organs while preserving tumor radiation doses by controlled administration of copper chelator penicillamine during (64)Cu-ATSM IRT. METHODS: Biodistribution was evaluated in HT-29 tumor-bearing mice injected with (64)Cu-ATSM (185 kBq) with or without oral penicillamine administration. The appropriate injection interval between (64)Cu-ATSM and penicillamine was determined. Then, the optimal penicillamine administration schedule was selected from single (100, 300, and 500 mg/kg) and fractionated doses (100 mg/kg×3 at 1- or 2-h intervals from 1 h after (64)Cu-ATSM injection). PET imaging was performed to confirm the effect of penicillamine with a therapeutic (64)Cu-ATSM dose (37 MBq). Dosimetry analysis was performed to estimate human absorbed doses. RESULTS: Penicillamine reduced (64)Cu accumulation in the liver and small intestine. Tumor uptake was not affected by penicillamine administration at 1 h after (64)Cu-ATSM injection, when radioactivity was almost cleared from the blood and tumor uptake had plateaued. Of the single doses, 300 mg/kg was most effective. Fractionated administration at 2-h intervals further decreased liver accumulation at later time points. PET indicated that penicillamine acts similarly with the therapeutic (64)Cu-ATSM dose. Dosimetry demonstrated that appropriately scheduled penicillamine administration reduced radiation doses to critical organs (liver, ovaries, and red marrow) below tolerance levels. Laxatives reduced radiation doses to the large intestine. CONCLUSIONS: We developed a novel strategy to reduce radiation exposure in critical organs during (64)Cu-ATSM IRT, thus promoting its clinical applications. This method could be beneficial for other (64)Cu-labeled compounds.

Radiochemotherapy plus 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC #663249) in advanced-stage cervical and vaginal cancers.

OBJECTIVE: Cervical and vaginal cancers have virally-mediated or mutated defects in DNA damage repair responses, making these cancers sensible targets for ribonucleotide reductase inhibition during radiochemotherapy. METHODS: We conducted a phase II study evaluating 3× weekly 2-hour intravenous 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, 25 mg/m(2)) co-administered with 1× weekly intravenous cisplatin (40 mg/m(2)) and daily pelvic radiation (45 Gy) in women with stage I(B2)-IV(B) cervical (n=22) or stage II-IV vaginal (n=3) cancers. Brachytherapy followed (40 Gy). Toxicity was monitored by common terminology criteria for adverse events (version 3.0). The primary end point of response was assessed by 3-month posttherapy 2-[(18)F] fluoro-2-deoxy-d-glucose positron emission tomography (PET/CT) and clinical examination. RESULTS: 3-AP radiochemotherapy achieved clinical responses in 24 (96% [95% confidence interval: 80-99%]) of 25 patients (median follow-up 20 months, range 2-35 months). 23 (96% [95% confidence interval: 80-99%]) of 24 patients had 3-month posttherapy PET/CT scans that recorded metabolic activity in the cervix or vagina equal or less than that of the cardiac blood pool, suggesting complete metabolic responses. The most frequent 3-AP radiochemotherapy-related adverse events included fatigue, nausea, diarrhea, and reversible hematological and electrolyte abnormalities. CONCLUSIONS: The addition of 3-AP to cisplatin radiochemotherapy was tolerable and produced high rates of clinical and metabolic responses in women with cervical and vaginal cancers. Future randomized phase II and III clinical trials of 3-AP radiochemotherapy are warranted.

A phase I study of prolonged infusion of triapine in combination with fixed dose rate gemcitabine in patients with advanced solid tumors.

PURPOSE: Prolonged exposure of cancer cells to triapine, an inhibitor of ribonucleotide reductase, followed by gemcitabine enhances gemcitabine activity in vitro. Fixed-dose-rate gemcitabine (FDR-G) has improved efficacy compared to standard-dose. We conducted a phase I trial to determine the maximum tolerated dose (MTD), safety, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of prolonged triapine infusion followed by FDR-G. EXPERIMENTAL DESIGN: Triapine was given as a 24-hour infusion, immediately followed by FDR-G (1000 mg/m(2) over 100-minute). Initially, this combination was administered days 1 and 8 of a 21-day cycle (Arm A, triapine starting dose 120 mg); but because of myelosuppression, it was changed to days 1 and 15 of a 28-day cycle (Arm B, starting dose of triapine 75 mg). Triapine steady-state concentrations (Css) and circulating ribonucleotide reductase M2-subunit (RRM2) were measured. RESULTS: Thirty-six patients were enrolled. The MTD was determined to be triapine 90 mg (24-hour infusion) immediately followed by gemcitabine 1000 mg/m(2) (100-minute infusion), every 2 weeks of a 4-week cycle. DLTs included grade 4 thrombocytopenia, leukopenia and neutropenia. The treatment was well tolerated with fatigue, nausea/vomiting, fever, transaminitis, and cytopenias being the most common toxicities. Among 30 evaluable patients, 1 had a partial response and 15 had stable disease. Triapine PK was similar, although more variable, compared to previous studies using doses normalized to body-surface-area. Steady decline in circulating levels of RRM2 may correlate with outcome. CONCLUSIONS: This combination was well tolerated and showed evidence of preliminary activity in this heavily pretreated patient population, including prior gemcitabine failure.

Management of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone-induced methemoglobinemia.

The anticancer agent 3-aminopyridine-2-carboxaldehyde thiosemicarbazone is a ribonucleotide reductase inhibitor. It inactivates ribonucleotide reductase by disrupting an iron-stabilized radical in ribonucleotide reductase's small subunits, M2 and M2b (p53R2). Unfortunately, 3-aminopyridine-2-carboxaldehyde thiosemicarbazone also alters iron II (Fe(2+)) in hemoglobin. This creates Fe(3+) methemoglobin that does not deliver oxygen. Fe(2+) in hemoglobin normally auto-oxidizes to inactive Fe(3+) methemoglobin at a rate of nearly 3% per day and this is counterbalanced by a reductase system that normally limits methemoglobin concentrations to less than 1% of hemoglobin. This balance may be perturbed by symptomatic toxicity levels during 3-aminopyridine-2-carboxaldehyde thiosemicarbazone therapy. Indications of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone sequelae attributable to methemoglobinemia include resting dyspnea, headaches and altered cognition. Management of methemoglobinemia includes supplemental oxygen, ascorbate and, most importantly, intravenously administered methylene blue as a therapeutic antidote.

A phase I and pharmacokinetic study of oral 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC #663249) in the treatment of advanced-stage solid cancers: a California Cancer Consortium Study.

BACKGROUND: 3-Aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) is a novel small-molecule ribonucleotide reductase inhibitor. This study was designed to estimate the maximum tolerated dose (MTD) and oral bioavailability of 3-AP in patients with advanced-stage solid tumors. METHODS: Twenty patients received one dose of intravenous and subsequent cycles of oral 3-AP following a 3 + 3 patient dose escalation. Intravenous 3-AP was administered to every patient at a fixed dose of 100 mg over a 2-h infusion 1 week prior to the first oral cycle. Oral 3-AP was administered every 12 h for 5 consecutive doses on days 1-3, days 8-10, and days 15-17 of every 28-day cycle. 3-AP was started at 50 mg with a planned dose escalation to 100, 150, and 200 mg. Dose-limiting toxicities (DLT) and bioavailability were evaluated. RESULTS: Twenty patients were enrolled. For dose level 1 (50 mg), the second of three treated patients had a DLT of grade 3 hypertension. In the dose level 1 expansion cohort, three patients had no DLTs. No further DLTs were encountered during escalation until the 200-mg dose was reached. At the 200 mg 3-AP dose level, two treated patients had DLTs of grade 3 hypoxia. One additional DLT of grade 4 febrile neutropenia was subsequently observed at the de-escalated 150 mg dose. One DLT in 6 evaluable patients established the MTD as 150 mg per dose on this dosing schedule. Responses in the form of stable disease occurred in 5 (25%) of 20 patients. The oral bioavailability of 3-AP was 67 ± 29% and was consistent with the finding that the MTD by the oral route was 33% higher than by the intravenous route. CONCLUSIONS: Oral 3-AP is well tolerated and has an MTD similar to its intravenous form after accounting for the oral bioavailability. Oral 3-AP is associated with a modest clinical benefit rate of 25% in our treated patient population with advanced solid tumors.

Phase II trial of the ribonucleotide reductase inhibitor 3-aminopyridine-2-carboxaldehydethiosemicarbazone plus gemcitabine in patients with advanced biliary tract cancer.

BACKGROUND: 3-Aminopyridine-2-carboxaldehydethiosemicarbazone (3-AP) is a novel small molecule ribonucleotide reductase (RR) inhibitor which is more potent than hydroxyurea, the prototype of RR inhibitors. 3-AP enhances the cellular uptake and DNA incorporation of gemcitabine in tumor cell lines. We evaluated the combination of 3-AP plus gemcitabine in advanced biliary tract adenocarcinoma. METHODS: Thirty-three patients with advanced adenocarcinoma of the gall bladder or biliary tract received gemcitabine (1,000 mg/m(2) on days 1, 8, and 15 every 28 days) 1 h after completing a 4-h infusion of 3-AP given at a dose of 105 mg/m(2) in patients with normal liver function (stratum A) or 80 mg/m(2) if abnormal liver function (stratum B). The trial was designed to determine whether the response rate was at least 30% in stratum A and 20% in stratum B. RESULTS: Objective response occurred in 3 of 23 patients (13%, 95% confidence intervals [CI] 3, 34%) with normal liver function, and in 0 of 10 patients with abnormal liver function. The most common grade 3-4 adverse events in all patients included neutropenia (42%), infection (33%), thrombocytopenia (27%), anemia (18%), and fatigue (15%). Fine needle aspiration of tumor samples obtained before and 24 h after 3-AP therapy showed increased R2 mRNA expression by in situ RT-PCR, suggesting RR inhibition. CONCLUSIONS: Despite evidence for RR inhibition in vivo, the 3-AP plus gemcitabine combination is not likely to be associated with a response rate exceeding 30% in patients with adenocarcinoma of the biliary tract.

Iron Chelators: Development of Novel Compounds with High and Selective Anti-Tumour Activity.

Targeting essential nutrients (eg., those required for DNA synthesis) to inhibit cancer cell growth is a well established therapeutic strategy. A good example is the highly successful folate antagonist, methotrexate. However, up until recently, strategies to target iron which is also crucial for DNA synthesis have not been systematically explored to develop agents for the treatment of cancer. Over the last 15 years, our laboratory has embarked upon structure-activity studies designed to develop novel Fe chelators with anti-cancer efficacy. These studies have led to the development of the dipyridyl thiosemicarbazone chelators that show potent and selective anti-cancer activity and which overcome resistance to other cytotoxic agents. This class of compounds include the chelator, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), which at optimal doses markedly inhibits tumour growth and is well tolerated. Moreover, this ligand does not induce overt Fe-depletion in vivo, probably because very low doses (0.4 mg/kg) are effective at inhibiting tumour growth. Importantly, our compounds are far more active and less toxic than the chelator, Triapine®, that is being assessed in a wide variety of international clinical trials. A vital part of the mechanism of action of these compounds is their ability to form a redox-active Fe complex that generates radicals to inhibit tumour growth. Due to their relatively high lipophilicity and low molecular weight of this class of compounds, oral activity may be expected in addition to their well known efficacy via the intravenous route.

Phase I trial of pelvic radiation, weekly cisplatin, and 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC #663249) for locally advanced cervical cancer.

PURPOSE: This study assessed the safety/tolerability, pharmacokinetics, and clinical activity of three times weekly i.v. 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC #663249) in combination with once-weekly i.v. cisplatin and daily pelvic radiation in patients with gynecologic malignancies. 3-AP is a novel small-molecule inhibitor of ribonucleotide reductase (RNR) and is being tested as a potential radiosensitizer and chemosensitizer. EXPERIMENTAL DESIGN: Patients with stage IB2 to IVB cervical cancer (n = 10) or recurrent uterine sarcoma (n = 1) were assigned to dose-finding cohorts of 2-hour 3-AP infusions during 5 weeks of cisplatin chemoradiation. Pharmacokinetic and methemoglobin samples and tumor biopsy for RNR activity were obtained on day 1 and day 10. Clinical response was assessed. RESULTS: The maximum tolerated 3-AP dose was 25 mg/m(2) given three times weekly during cisplatin and pelvic radiation. Two patients experienced manageable 3-AP-related grade 3 or 4 electrolyte abnormalities. 3-AP pharmacokinetics showed a 2-hour half-life, with median peak plasma concentrations of 277 ng/mL (25 mg/m(2)) and 467 ng/mL (50 mg/m(2)). Median methemoglobin levels peaked at 1% (25 mg/m(2)) and 6% (50 mg/m(2)) at 4 hours after initiating 3-AP infusions. No change in RNR activity was found on day 1 versus day 10 in six early complete responders, whereas elevated RNR activity was seen on day 10 as compared with day 1 in four late complete responders (P = 0.02). Ten (100%) patients with stage IB2 to IVB cervical cancer achieved complete clinical response and remained without disease relapse with a median 18 months of follow-up (6-32 months). CONCLUSIONS: 3-AP was well tolerated at a three times weekly i.v. 25 mg/m(2) dose during cisplatin and pelvic radiation. Clin Cancer Res; 16(4); 1298-306.

A phase II trial of triapine (NSC# 663249) and gemcitabine as second line treatment of advanced non-small cell lung cancer: Eastern Cooperative Oncology Group Study 1503.

BACKGROUND: The objective of ECOG 1503 was to determine the response rate of this combination in the second-line treatment of advanced NSCLC. METHODS: Triapine 105 mg/m(2) IV on days 1, 8, and 15, and gemcitabine 1,000 mg/m(2) on days 1, 8, and 15, of a 28 day cycle. RESULTS: Eighteen patients enrolled. Three patients were not eligible due to protocol violations. No objective antitumor responses were seen. Three patients (20%) experienced stable disease (90% CI 5.7-44%). Median overall survival: 5.4 months (95% CI 4.2-11.6 months); median time to progression: 1.8 months (95% CI 1.7-3.5 months). Five patients developed acute infusion reactions to Triapine related to elevated methemoglobinemia. Patients with MDR1 variant genotypes of C3435T experienced superior overall survival compared to non-variants (13.3 vs. 4.3 months, respectively, p = 0.023). CONCLUSION: This regimen did not demonstrate activity in relapsed NSCLC. Prolonged survival seen with MDR1 variant genotypes is hypothesis-generating.

A phase I study of Triapine in combination with doxorubicin in patients with advanced solid tumors.

PURPOSE: To assess the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacokinetics and antitumor activity of Triapine administered in combination with doxorubicin. STUDY DESIGN: Patients were treated with doxorubicin intravenously (IV) on day 1 and Triapine IV on days 1-4 of a 21-day cycle. The starting dose (level 1) was doxorubicin 60 mg/m(2) and Triapine 25 mg/m(2). PK analysis was performed at various time-points before and after treatment. RESULTS: Twenty patients received a total of 49 courses of treatment on study. At dose level 2 (doxorubicin 60 mg/m(2), Triapine 45 mg/m(2)), two patients experienced DLTs (febrile neutropenia, grade 4 thrombocytopenia). An additional three patients were enrolled at dose level 1 without initial toxicity. Enrollment then resumed at dose level 2a with a decreased dose of doxorubicin (45 mg/m(2)) with Triapine 45 mg/m(2). The two patients enrolled on this level had two DLTs (diarrhea, CVA). Enrollment was planned to resume at dose level 1; however, the sixth patient enrolled to this cohort developed grade 5 heart failure (ejection fraction 20%, pretreatment EF 62%) after the second course. Thus, doxorubicin and Triapine were reduced to 45 and 25 mg/m(2), respectively (level 1a), prior to resuming enrollment at dose level 1, the MTD. The main drug-related toxicity was myelosuppression. Non-hematologic toxicities included mild-to-moderate fatigue, grade 3 diarrhea and grade 4 CVA. There was one treatment-related death due to heart failure. While no objective responses were observed, subjective evidence of clinical activity was observed in patients with refractory melanoma and prostate cancer. CONCLUSIONS: Pretreated patients with advanced malignancies can tolerate the combination of Triapine and doxorubicin at doses that achieve subjective clinical benefit with the main treatment-related toxicities being myelosuppression and fatigue. The MTD was determined to be doxorubicin 60 mg/m(2) on day 1 and Triapine 25 mg/m(2) on days 1-4 of a 21-day cycle.

A phase 2 consortium (P2C) trial of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) for advanced adenocarcinoma of the pancreas.

3-Aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, Triapine) is a novel small molecule inhibitor of ribonucleotide reductase (RR) with clinical signs of activity in pancreatic cancer. Therefore, the Phase 2 Consortium (P2C) initiated a trial (two single stage studies with planned interim analysis) of 3-AP at 96 mg/m(2) intravenously days 1-4 and 15-18 of a 28-day cycle in both chemotherapy-naive and gemcitabine-refractory (GR) patients with advanced pancreatic cancer. The primary endpoint was survival at six months (chemotherapy-naive) and four months (GR). Secondary endpoints were toxicity, response, overall survival, time to progression and mechanistic studies. Fifteen patients were enrolled including one chemotherapy-naïve and 14 GR. The chemotherapy-naïve patient progressed during cycle 1 with grade 3 and 4 toxicities. Of 14 GR patients, seven received two cycles, six received one cycle and one received eight cycles. Progression precluded further treatment in 11 GR patients. Additionally, one died of an ileus in cycle 1 considered related to treatment and two stopped treatment due to toxicity. Five GR patients had grade 4 toxicities possibly related to 3-AP and six GR patients had grade 3 fatigue. Toxicities and lack of meaningful clinical benefit prompted early study closure. Four-month survival in GR patients was 21% (95% CI: 8-58%). Correlative studies confirmed that 3-AP increased the percentage of S-phase buccal mucosal cells, the presence of multidrug resistance gene polymorphisms appeared to predict leukopenia, and baseline pancreatic tumor RR M2 expression was low relative to other tumors treated with 3-AP. In conclusion, this regimen appears inactive against predominantly GR pancreatic cancer. RR M2 protein may not have a critical role in the malignant potential of pancreatic cancer.

Future of toxicology--iron chelators and differing modes of action and toxicity: the changing face of iron chelation therapy.

Iron (Fe) chelation therapy was initially designed to alleviate the toxic effects of excess Fe evident in Fe-overload diseases. However, the novel toxicological properties of some Fe chelator-metal complexes have shifted appreciable focus to their application in cancer chemotherapy. Redox-inactive Fe chelator complexes are well suited for the treatment of Fe-overload diseases, whereas Fe chelator complexes with high redox activity have shown promising results as chemotherapeutics against cancer. Within this perspective, we discuss the different modes of action and toxicological profiles of Fe chelators, including analogues of 2-pyridylcarboxaldehyde isonicotinoyl hydrazone, di-2-pyridylketone isonicotinoyl hydrazone, di-2-pyridylketone thiosemicarbazone, and the clinically trialed chelator 3-aminopyridine-2-carboxaldehyde thiosemicarbazone. The potential application of these agents in the changing face of Fe chelation therapy is discussed.

Phase II study of Triapine in patients with metastatic renal cell carcinoma: a trial of the National Cancer Institute of Canada Clinical Trials Group (NCIC IND.161).

Triapine is a novel small molecule ribonucleotide reductase inhibitor that showed activity in renal cell carcinoma (RCC) cell lines. Evaluating new agents with novel mechanisms remains of interest for patients with incurable RCC. This was a single-arm, multicentre phase II trial where Triapine was given at a schedule of 96 mg/m2 2-h infusion daily x 4 repeated every 2 weeks in patients with recurrent RCC. A median of four cycles of Triapine was administered to 19 eligible patients. One response was seen (7%.) Median time to progression was 3.6 months. Common adverse events (AEs) were grade 1-2, with fatigue in 74%, nausea in 68% and vomiting in 58%. However grade 3/4 neutropenia was seen in 79% and acute reactions of hypoxia, hypotension, methemoglobinemia were seen. Dose reductions/delays due to AEs were common with only 47% of patients receiving > 90% of planned dose intensity. The study closed, at the end of stage 1 as it did not meet the minimal efficacy criteria to proceed. Further evaluation of Triapine at this dose and schedule in patients with advanced kidney cancer is not recommended.

Recognition and management of methemoglobinemia and hemolysis in a G6PD-deficient patient on experimental anticancer drug Triapine.

We report occurrence of severe methemoglobinemia in a patient on novel experimental anti-cancer drug, Triapine. Treatment with methylene blue led to massive hemolysis due to concomitant G6PD deficiency. We recommend that G6PD screening be done in high-risk populations prior to commencement of Triapine therapy.

Triapine and cytarabine is an active combination in patients with acute leukemia or myelodysplastic syndrome.

Triapine, an iron chelator and a potent inhibitor of ribonucleotide reductase, has significant anti-leukemia activity. A phase I study of Triapine in combination with ara-C was conducted in 32 patients with refractory acute leukemia and high-risk MDS. Triapine (105 mg/m2/day 6-h infusion) was followed immediately by ara-C [100 (n=4), 200 (n=6), 400 (n=7), or 800 (n=8)mg/m2/day] as an 18-h infusion for 5 consecutive days. Dose-limiting toxicities (DLTs) were observed at the 800 mg/m2 ara-C dose level (one patient each with grade 4 mucositis; grade 4 neutropenic colitis, sepsis; grade 4 neuropathy; and grade 4 hyperbilirubinemia). Therefore, the study was amended to include an ara-C dose level of 600 mg/m2/day, no DLTs occurred in seven patients treated at this dose level. Mean Triapine C(max) and AUC were 1.13 microg/mL and 251.5 minmicrog/mL. Of 31 evaluable patients, 4 (13%) (3 AML, 1 Ph+ALL) achieved a CR (1 at a dose of 800 mg/m2; 2 at 600 mg/m2; 1 at 200mg/m2). The recommended phase II regimen is Triapine 105 mg/m2/day followed by ara-C 600 mg/m2/day for 5 consecutive days every 3-6 weeks.