tirapazamine and 4-(3-(2-nitro-1-imidazolyl)-propylamino)-7-chloroquinoline-hydrochloride

Solid tumours contain regions of very low oxygen concentrations that are said to be hypoxic. Hypoxia is a natural phenotype of solid tumours resulting from an imperfect vascular network. There are a number of consequences associated with tumour hypoxia including: resistance to ionising radiation, resistance to chemotherapy and the magnification of mutated p53. In addition tissue hypoxia has been regarded as a key factor for tumour aggressiveness and metastasis by activation of signal transduction pathways and gene regulatory mechanisms. It is clear that hypoxia in solid tumours promotes a strong oncogenic phenotype and is a phenomenon that occurs in all solid tumours. As such this provides a significant target for drug discovery particularly for tumour-targeting agents. A range of chemical classes (N-oxides, quinones, nitro-aromatics) have been explored as bioreductive agents that target tumour hypoxia. The most advanced agent, tirapazamine, is in phase III clinical trials in combination with cis-platin. The aim of this review is to give a brief overview of the current molecules and strategies being explored for targeting tumour hypoxia.

Topics: Anthraquinones; Antineoplastic Agents; Aziridines; Benzoquinones; Cell Hypoxia; Clinical Trials, Phase III as Topic; Drug Screening Assays, Antitumor; Humans; Imidazoles; Indolequinones; Neoplasms; Prodrugs; Quinolines; Radiation-Sensitizing Agents; Tirapazamine; Triazines

Bioreductive drugs can cause retinal toxicity, mediated by extensive apoptosis in the outer retina of rodents and monkeys. In the present study, we have investigated whether or not the novel and promising hypoxia-selective cytotoxin 4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1, NSC 709257) can cause hypoxia-dependent retinal toxicity in BALB/c mice alone or in combination with cyclophosphamide (CPM), one of the anti-cancer agents that acts synergistically with NLCQ-1 against mouse tumours and human xenografts. The bioreductive agent tirapazamine (TPZ) was included for comparison purposes. Retinal damage was quantified by morphometric analysis of histological sections following IP treatment of female BALB/c mice. No retinal toxicity was observed with 10 or 22 mg/kg of NLCQ-1 or 23 mg/kg TPZ alone, whereas statistically significant retinal toxicity was observed with the higher TPZ dose of 52 mg/kg (p < 0.001). Thus, a normalized photoreceptor layer thickness (NPT) value of 0.50 ± 0.04, 0.48 ± 0.03 and 0.33 ± 0.06 was determined for untreated, NLCQ-1 and TPZ-treated mice at the highest dose, respectively. Marginal retinal toxicity was observed with the lower dose of TPZ in combination with CPM.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Cyclophosphamide; Cytotoxins; Dose-Response Relationship, Drug; Drug Synergism; Female; Humans; Hypoxia; Imidazoles; Mice; Mice, Inbred BALB C; Neoplasms; Quinolines; Retina; Tirapazamine; Triazines

Metastases cause most cancer-related deaths. We investigated the use of hypoxia-selective cytotoxins as adjuvants to radiotherapy in the control of metastatic tumour growth.. The NLCQ-1, RB6145 and tirapazamine were assessed against the spontaneously metastasising KHT model. Subcutaneous KHT tumours (250 mm(3)) were irradiated with 25 Gy (single fraction) to control primary growth. Equitoxic drug treatments (NLCQ-1 (10 mg kg(-1)) once daily; RB6145 (75 mg kg(-1)) and tirapazamine (13 mg kg(-1)) twice daily) were administered 3-6 days post-radiotherapy when hypoxic cells were evident in lung micrometastases. Mice were culled when 50% of controls exhibited detrimental signs of lung metastases.. In total, 95% of control mice presented with lung disease. This was significantly reduced by NLCQ-1 (33%; P=0.0002) and RB6145 (60%; P=0.02). Semi-quantitative grading of lung disease revealed a significant improvement with all treatments, with NLCQ-1 proving most efficacious (median grades: control, 4; NLCQ, 0 (P<0.0001); RB6145, 1 (P<0.001), tirapazamine, 3 (P=0.007)). Positron emission tomography (PET) was evaluated as a non-invasive means of assessing metastatic development. Primary and metastatic KHT tumours showed robust uptake of [(18)F]fluorodeoxyglucose ([(18)F]FDG). Metastatic burden discernable by [(18)F]FDG PET correlated well with macroscopic and histological lung analysis.. The hypoxia-selective cytotoxin NLCQ-1 controls metastatic disease and may be a successful adjuvant to radiotherapy in the clinical setting.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Hypoxia; Cell Line, Tumor; Chemotherapy, Adjuvant; Combined Modality Therapy; Drug Administration Schedule; Drug Evaluation, Preclinical; Imidazoles; Lung Neoplasms; Mice; Mice, Inbred C3H; Neoplasm Metastasis; Nitroimidazoles; Quinolines; Sarcoma; Tirapazamine; Triazines

To investigate potential synergistic interactions between bioreductive agents, either NLCQ-1 or tirapazamine (TPZ) and two alkylating chemotherapeutic drugs, and how such interactions compare in vitro and in vivo.. V79 cells (in vitro studies) and the SCCVII/C3H murine tumor model (in vivo studies) were used. The alkylating chemotherapeutic agents examined were cisplatin (cisDDP) and melphalan (L-PAM). In vivo, all agents were administered by i.p. injection wherein NLCQ-1 and TPZ were given at equitoxic doses of 10 and 23 mg/kg, respectively. Optimal administration schedules and dose modification factors (DMF) were determined in vivo for the antitumor effect or bone marrow toxicity by using the in vivo-in vitro clonogenic assay as the endpoint.. A schedule-dependent synergistic interaction was observed between NLCQ-1/TPZ and each alkylating agent, both in vitro and in vivo, and an optimal potentiation was obtained when each bioreductive agent was administered prior to each chemotherapeutic drug. However, significant DMF values and an in vivo therapeutic index (TI) was obtained only with NLCQ-1. Limited mechanistic studies in V79 cells by using the alkaline comet assay demonstrated that hypoxic preincubation with NLCQ-1 increases the cross-links induced by subsequent aerobic exposure to cisDDP.. These results verify our previous observations in EMT6 tumors and suggest a potential clinical use of NLCQ-1 as a synergistic adjuvant to chemotherapy with alkylating agents against solid tumors possessing hypoxic regions.

Topics: Animals; Antineoplastic Agents; Antineoplastic Agents, Alkylating; Cisplatin; Comet Assay; Cricetinae; Drug Synergism; Female; Hypoxia; Imidazoles; In Vitro Techniques; Melphalan; Mice; Mice, Inbred C3H; Neoplasm Transplantation; Quinolines; Tirapazamine; Triazines

The antitumor effect of taxol was investigated in combination with the bioreductive compounds NLCQ-1 or tirapazamine (TPZ), in vivo. The EMT6/BALB/c and SCCVII/C3H murine tumor models were used. All drugs were given by IP injection: NLCQ-1 at 10 mg/kg (28% of its LD50), TPZ at 30 or 23 mg/kg (38% or 28% of its LD50, respectively), and taxol up to 25 mg/kg. Dose modification factors (DMF) were calculated at the optimal administration intervals for potentiation of taxol by NLCQ-1/TPZ, by using the in vivo-in vitro assay as the endpoint. Bone marrow toxicity studies were performed in parallel by using a modified CFU-GM assay. A schedule-dependent potentiation of taxol was observed with either hypoxic cytotoxin and in both tumor models. The percentage of tumor cells, P, that were killed beyond additivity was 59.2 and 29.5 when NLCQ-1 was administered 1-3 h after, and TPZ 3 h before taxol, respectively, in the EMT6/ BALB/c model. The P values in the SCCVII/C3H model were 31.0 and 24.6 for NLCQ-1 and TPZ, respectively, when either of them was administered ca. 2 h after taxol. At the above time schedules, therapeutic indexes [ThI = DMF(T)/DMF(BM), where DMF(T) and DMF(BM) are the DMF values for the antitumor effect and bone marrow toxicity, respectively] of 2.5 and 2.0 were obtained by NLCQ-1 in the EMT6 and SCCVII tumors, respectively, whereas a ThI of 1.2 was obtained by TPZ in both type of tumors. These results suggest a potential clinical use of NLCQ-1 as a potentiator of taxol againstsolid tumors possessing hypoxic regions.

Topics: Animals; Antineoplastic Agents; Antineoplastic Agents, Phytogenic; Dose-Response Relationship, Drug; Drug Synergism; Imidazoles; Mammary Neoplasms, Experimental; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Paclitaxel; Quinolines; Tirapazamine; Triazines

The antitumor effect and bone marrow toxicity of 5-fluorouracil (5FU) in combination with the hypoxia-selective cytotoxins NLCQ-1 or tirapazamine (TPZ) were investigated in vivo.. Using appropriate intraperitoneal administration schedules for optimal synergistic interactions, the antitumor effect and the bone marrow toxicity of combinations of NLCQ-1 or TPZ and 5FU were determined in EMT6/BALB/c and SCCVII/C3H models in terms of dose modification factors (DMF) using the in vivo-in vitro clonogenic assay as endpoint. Bone marrow toxicity studies were performed in parallel using a modified CFU-GM assay. The antitumor efficacies of each combination treatment under optimal administration conditions were evaluated in the SCCVII/C3H model using also the tumor regrowth assay as endpoint.. A schedule-dependent and tumor-specific synergistic interaction was observed for NLCQ-1 plus 5FU and DMFs of 2.0-2.3 and 1.0 were obtained for the antitumor effect and bone marrow toxicity, respectively, in both tumor models. The antitumor effect of 5FU was slightly potentiated (DMF 1.2) by TPZ in the EMT6/BALB/c model but not in the SCCVII/C3H model when the in vivo-in vitro assay was used as the endpoint. Significant additional tumor regrowth delays (about 11 and 6 days for NLCQ-1 and TPZ, respectively) were observed, compared to the effect of 5FU alone, when an equitoxic dose of NLCQ-1 (10 mg/kg) or TPZ (23 mg/kg) was administered 1 h before 5FU (50 mg/kg) twice a day at 4-h intervals on days 0 and 9.. These results corroborate the therapeutic advantage of combining hypoxia-selective cytotoxins such as NLCQ-1 and TPZ with chemotherapy.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Bone Marrow; Drug Synergism; Female; Fluorouracil; Hypoxia; Imidazoles; Mice; Mice, Inbred BALB C; Quinolines; Tirapazamine; Triazines; Tumor Cells, Cultured; Tumor Stem Cell Assay

The antitumor effect of paclitaxel was investigated against murine tumors and human xenografts in combination with the hypoxia-selective cytotoxin NLCQ-1.. The tumor regrowth assay was used as the endpoint and an optimal administration schedule was followed, based on previous studies. In certain cases the hypoxia-selective cytotoxin tirapazamine (TPZ) was included for comparison. NLCQ-1 was given i.p. in saline, whereas paclitaxel was given i.p. (C3H) or i.v. (athymic mice) in an appropriately formulated vehicle.. In the SCCVII/C3H model, when NLCQ-1 (10 mg/kg) was given 90 min after paclitaxel (8 mg/kg) twice a day 4 h apart on days 0 and 9, tumor regrowth delay was increased by 10.3 days compared to paclitaxel alone, at fivefold the original tumor size. This corresponds to 1.51 log cell kill. In the same study, TPZ resulted in 4.6 days of extra delay compared to paclitaxel alone, which corresponds to 0.91 log cell kill. Paclitaxel alone resulted in 3.9 days of tumor growth delay compared to control, or 0.42 log cell kill, but this delay was not statistically significant ( P<0.2). In the FSaIIC/C3H model, when NLCQ-1 (10 mg/kg) was given 90 min after paclitaxel (12 mg/kg) on day 0, tumor regrowth delay was increased by 5.8 days compared to paclitaxel alone, at 20-fold the original tumor size. In athymic nude mice bearing PC-3 prostate xenografts, NLCQ-1 (10 mg/kg) given 90 min before paclitaxel (8 mg/kg) for five consecutive days, increased tumor regrowth delay by 5.6 days compared to paclitaxel alone, at threefold the original tumor size. This corresponds to 0.95 log cell kill whereas the log cell kill for paclitaxel alone was 0.52. No improvement was observed in the tumor regrowth delay at any lower paclitaxel doses given in combination with NLCQ-1. No concurrent enhancement in paclitaxel-induced toxicity was observed in any of the combination treatments or in any of the models tested. NLCQ-1 alone was ineffective at the doses given.. These results suggest that an enhancement in tumor growth delay can be achieved both in murine tumors and in human xenografts due to a synergistic interaction between NLCQ-1 and paclitaxel.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Survival; Female; Humans; Imidazoles; Injections, Subcutaneous; Male; Mice; Mice, Inbred C3H; Mice, Nude; Neoplasm Transplantation; Neoplasms, Experimental; Paclitaxel; Quinolines; Tirapazamine; Transplantation, Heterologous; Triazines; Tumor Cells, Cultured

Comparisons of schedule-dependent interactions between the hypoxic cytotoxins NLCQ-1/ tirapazamine (TPZ) and various chemotherapeutic drugs in BALB/c mice bearing EMT6 tumors.. The antitumor effects of the single or combined drugs were assessed with various administration time intervals using the in vivo-in vitro clonogenic assay as the endpoint. The chemotherapeutic drugs tested were cisplatin (cisDDP), melphalan (L-PAM), cyclophosphamide (CPM), 5-fluorouracil (5-FU), doxorubicin (Doxo), etoposide (VP-16) and Taxol at doses of 8, 5, 100, 150, 12, 35 and 20 mg/kg, respectively. NLCQ-1 was given at 10 mg/kg (28% of its single LD50 value) and TPZ was given at 30 mg/kg (38% of its single LD50 value). All drugs were given by i.p. injection in saline or as commercially available pharmaceutical solutions.. Schedule-dependent synergistic interactions with different patterns for each bioreductive drug were observed with almost all of the chemotherapeutic agents examined. Potentiation accounting for more than 25% of the total tumor cell killing was observed with NLCQ-1/TPZ and cisDDP, L-PAM, CPM, 5-FU and Taxol at the optimal administration intervals. Potentiation accounting for 70% of the total tumor cell killing was found with NLCQ-1 and CPM.. These results suggest a potential clinical use of NLCQ-1/TPZ as adjuvants to certain chemotherapeutic agents.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cisplatin; Cyclophosphamide; Doxorubicin; Drug Administration Schedule; Drug Synergism; Etoposide; Female; Fluorouracil; Imidazoles; Mammary Neoplasms, Experimental; Melphalan; Mice; Mice, Inbred BALB C; Paclitaxel; Quinolines; Tirapazamine; Triazines; Tumor Cells, Cultured

The novel hypoxia-selective cytotoxin NLCQ-1, which is a weak DNA intercalator, was studied in conjunction with radiation against V79 cultured cells and EMT6 or SCCVII tumors in their syngeneic mice and compared with tirapazamine (TPZ). NLCQ-1 was a very potent and efficient radiosensitizer of hypoxic V79 cells, providing SER values of 2.27-2.56 at 20-80 microM concentration (measured at 10% survival level). Its C1.6 (concentration for an SER of 1.6 to be obtained) was 7.2+/-0.2 microM. Its in vitro therapeutic index (ThI, defined as CT50(Air),/C1.6) varied by the exposure time from 57 (1-h exposure) to 145 (4.5-h exposure). The corresponding C1.6 value for TPZ was 16.9 microM whereas its in vitro therapeutic index was 49 (3-h exposure). A schedule-dependent synergistic interaction was observed between NLCQ-1 or TPZ and 20 Gy of radiation in both tumor models examined, by using the in vivo-in vitro assay as endpoint. Optimal synergism (> 1 log) was observed in EMT6 tumors when each bioreductive drug was given between 45 and 60 min before irradiation. NLCQ-1 alone had no significant antitumor activity at 10 mg/kg (28% of its single LD50), whereas a 0.4 surviving fraction was obtained by TPZ at 30 mg/kg (38% of its single LD50). SER values of 1.52 and 1.25 were obtained with 10 mg/kg NLCQ-1 and 30 mg/kg TPZ, respectively, in EMT6 tumors. An SER value of 1.58 was obtained for both hypoxia-selective cytotoxins, at equitoxic doses, in SCCVII tumors, by using a fractionated regimen. These results suggest a possible use of NLCQ-1 or TPZ as adjuvants to radiotherapy.

Topics: Animals; Antineoplastic Agents; Carcinoma, Squamous Cell; Cell Hypoxia; Cell Line; Cell Survival; Cricetinae; Cytotoxins; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Drug Administration Schedule; Female; Imidazoles; Mammary Neoplasms, Experimental; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Neoplasms, Experimental; Quinolines; Radiation-Sensitizing Agents; Tirapazamine; Triazines; Tumor Cells, Cultured; Tumor Stem Cell Assay; Xenograft Model Antitumor Assays

Combined radioimmunotherapy (RAIT) and hypoxic cytotoxin therapy (SR4233 or NLCQ-1) have been evaluated with both modalities administered on the same day with only moderate improvement compared with the effects of RAIT alone. In a series of studies using oxygen electrodes, immunohistochemistry and radiotracers, we have demonstrated that RAIT induces a prolonged state of hypoxia in most tumors, without affecting the pO(2) levels in normal tissues. Using serial microelectrode measurements through subcutaneous (s.c.) GW-39 human colonic xenografts, we established that the median pO(2) was unrelated to the initial size of the tumor, over a range of sizes from 1.0 to 4.0 cm. Fourteen days after mice were given a 240-microCi dose of (131)I-MN-14 anti-carcinoembryonic antigen immunoglobulin G, their median pO(2) declined from 26.1 +/- 9.6 mmHg to 9.8 +/- 3.9 mmHg (p < 0.001). Using the radiotracer (3)H-MISO that accumulates in hypoxic regions, uptake in GW-39, LoVo and LS174T s.c. human colonic tumors increased 3.0- to 4.2-fold from day 14 through day 28 post-RAIT, but uptake of (3)H-MISO in CALU-3 tumors remained unchanged after RAIT. Normal tissue (liver, kidney, lung) uptake of (3)H-MISO did not exhibit significant changes. The increase in tumor hypoxia was also demonstrated visually using anti-PIMO staining of tumor sections. We postulated that sequential delivery of the 2 therapeutic agents, with the hypoxic cytotoxin given 2 weeks after RAIT when tumor pO(2) levels were at their nadir, would improve the therapeutic response above either modality alone or above the 2 agents delivered on the same day. Tumor growth was compared in mice given either RAIT or cytotoxin alone, the combined treatment on the same day or with the cytotoxin delivered 14 days after RAIT. Tumor size on day 35 for RAIT-treated and SR4233-treated GW-39 were 3.56 +/- 0.40 and 7.98 +/- 2.50 cm(3). When RAIT + SR4233 were delivered on the same day, tumor size dropped to 2.78 +/- 0.80 cm(3). If RAIT was given on day 0 and SR4233 on day 14, size further declined further to 1.74 +/- 0.32 cm(3) (p < 0.05 compared with same day delivery). For LS174T, tumor size on day 28 for RAIT-treated and SR4233-treated tumors were 1.14 +/- 0.36 cm(3) and 3.65 +/- 0.78 cm(3), respectively. When RAIT + SR4233 were delivered on the same day, size was 0.51 +/- 0.174 cm(3). If RAIT was dosed on day 0 and SR4233 was given on day 14, tumor size was 0.13 +/- 0.07 cm(3) (p < 0.05). Similar results were obtained for L

Topics: Animals; Antineoplastic Agents; Carcinoembryonic Antigen; Cell Hypoxia; Combined Modality Therapy; Cytotoxins; Drug-Related Side Effects and Adverse Reactions; Female; Humans; Hypoxia; Imidazoles; Immunoglobulin G; Mice; Mice, Nude; Microelectrodes; Neoplasm Transplantation; Neoplasms; Oxygen; Quinolines; Radiation-Sensitizing Agents; Radioimmunotherapy; Time Factors; Tirapazamine; Triazines; Tumor Cells, Cultured