The antitubercular activity of various nitro(triazole/imidazole)-based compounds.

Twenty three 3-nitrotriazole- and five nitroimidazole-based compounds, mostly amides, were screened for antitubercular activity against Mycobacterium tuberculosis H37Rv (Mtb H37Rv) under aerobic or low oxygen conditions, intracellular activity in murine J774 macrophages or THP-1 cells, activity against resistant Mtb strains as well as cytotoxicity in normal cells. Compounds with a Minimum Inhibitory Concentration (MIC) less than 10µM and 10-50µM were characterized as active and moderately active, respectively, whereas compounds with a MIC >50µM were characterized inactive. Fifteen 3-nitrotriazole-based compounds were active or moderately active against aerobic Mtb and thirteen of them were bactericidal, however, only four 3-nitrotriazoles were moderately active against anaerobic Mtb. All examined 2-nitroimidazole-based compounds were inactive against aerobic Mtb, and from the ones examined against anaerobic Mtb, only one was found moderately active. All examined compounds demonstrated intracellular activity and lack of cross-resistance. The five active 3-nitrotriazoles demonstrated good selectivity for Mtb. In conclusion, these classes of 3-nitrotriazole-based compounds merit further investigation as potential antitubercular agents.

The antitrypanosomal and antitubercular activity of some nitro(triazole/imidazole)-based aromatic amines.

A limited number of novel 3-nitrotriazole- and 2-nitroimidazole-linked quinolines and quinazolines were synthesized and screened for in vitro antitrypanosomal and antitubercular activities as well as cytotoxicity in normal cells. All compounds were active against T. cruzi amastigotes, while all but one were active or moderately active against T. b. rhodesiense. However, only two chloroquinolines exhibited satisfactory selectivity indices (SI) against T. cruzi and only one of them demonstrated a satisfactory SI against T. b. rhodesiense. All tested compounds demonstrated a Minimum Inhibitory Concentration (MIC) ≥ 200 µM against aerobic Mtb. However, the 2-nitroimidazole-based analogs were active against hypoxic Mtb with MIC values 2.89-9.18 µM. The present data support our previous observations that 2-nitroimidazole-based aromatic amines are selectively active against nonreplicating Mtb, while 3-nitrotriazole-based aromatic amines are potent antichagasic agents.

Nitrotriazole-Based Compounds as Antichagasic Agents in a Long-Treatment In Vivo Assay.

3-Nitrotriazole-based compounds belonging to various chemical subclasses were found to be very effective against Chagas disease both in vitro and in vivo after a short administration schedule. In this study, five compounds with specific characteristics were selected to be administered for longer periods of time to mice infected with the virulent Trypanosoma cruzi Y strain to further evaluate their effectiveness as antichagasic agents and whether or not potential adverse effects occur. Benznidazole was included for comparison purposes. Complete parasitemia depletion, weight gain, 100% survival, and a lack of myocardial inflammation were observed with four of the compounds and benznidazole administered intraperitoneally at 15 or 20 mg/kg of body weight/day for 40 days. There was a significant reduction in the number of treatment days (number of doses) necessary to induce parasitemia suppression with all four compounds compared to that required with benznidazole. Partial cures were obtained with only one compound tested at 15 mg/kg/day and on the schedule mentioned above but not with benznidazole. Taken together, our data suggest that these compounds demonstrate potent trypanocidal activity comparable to or better than that of the reference drug, benznidazole, when they are administered at the same dose and on the same schedule.

Nitrotriazole-based acetamides and propanamides with broad spectrum antitrypanosomal activity.

3-Nitro-1H-1,2,4-triazole-based acetamides bearing a biphenyl- or a phenoxyphenyl moiety have shown remarkable antichagasic activity both in vitro and in an acute murine model, as well as substantial in vitro antileishmanial activity but lacked activity against human African trypanosomiasis. We have shown now that by inserting a methylene group in the linkage to obtain the corresponding propanamides, both antichagasic and in particular anti-human African trypanosomiasis potency was increased. Therefore, IC50 values at low nM concentrations against both T. cruzi and T. b. rhodesiense, along with huge selectivity indices were obtained. Although several propanamides were active against Leishmania donovani, they were slightly less potent than their corresponding acetamides. There was a good correlation between lipophilicity (clogP value) and trypanocidal activity, for all new compounds. Type I nitroreductase, an enzyme absent from the human host, played a role in the activation of the new compounds, which may function as prodrugs. Antichagasic activity in vivo was also demonstrated with representative propanamides.

Antitrypanosomal activity of 5-nitro-2-aminothiazole-based compounds.

A small series of 5-nitro-2-aminothiazole-based amides containing arylpiperazine-, biphenyl- or aryloxyphenyl groups in their core were synthesized and evaluated as antitrypanosomatid agents. All tested compounds were active or moderately active against Trypanosoma cruzi amastigotes in infected L6 cells and Trypanosoma brucei brucei, four of eleven compounds were moderately active against Leishmania donovani axenic parasites while none were deemed active against T. brucei rhodesiense. For the most active/moderately active compounds a moderate selectivity against each parasite was observed. There was good correlation between lipophilicity (clogP value) and antileishmanial activity or toxicity against L6 cells. Similarly, good correlation existed between clogP values and IC50 values against T. cruzi in structurally related subgroups of compounds. Three compounds were more potent as antichagasic agents than benznidazole but were not activated by the type I nitrorectusase (NTR).

3-Nitrotriazole-based piperazides as potent antitrypanosomal agents.

Novel linear 3-nitro-1H-1,2,4-triazole-based piperazides were synthesized and evaluated as antitrypanosomal agents. In addition, some bisarylpiperazine-ethanones which were formed as by-products were also screened for antiparasitic activity. Most 3-nitrotriazole-based derivatives were potent and selective against Trypanosoma cruzi parasites, but only one displayed these desired properties against Trypanosoma brucei rhodesiense. Moreover, two 3-nitrotriazole-based chlorophenylpiperazides were moderately and selectively active against Leishmania donovani. Although the bisarylpiperazine-ethanones were active or moderately active against T. cruzi, none of them demonstrated an acceptable selectivity. In general, 3-nitrotriazole-based piperazides were less toxic to host L6 cells than the previously evaluated 3-nitrotriazole-based piperazines and seven of 13 were 1.54- to 31.2-fold more potent antichagasic agents than the reference drug benznidazole. Selected compounds showed good ADMET characteristics. One potent in vitro antichagasic compound (3) was tested in an acute murine model and demonstrated antichagasic activity after a 10-day treatment of 15 mg/kg/day. However, neither compound 3 nor benznidazole showed a statistically significant P value compared to control due to high variability in parasite burden among the untreated animals. Working as prodrugs, 3-nitrotriazole-based piperazides were excellent substrates of trypanosomal type I nitroreductases and constitute a novel class of potentially effective and more affordable antitrypanosomal agents.

Discovery of potent nitrotriazole-based antitrypanosomal agents: In vitro and in vivo evaluation.

3-Nitro-1H-1,2,4-triazole- and 2-nitro-1H-imidazole-based amides with an aryloxy-phenyl core were synthesized and evaluated as antitrypanosomal agents. All 3-nitrotriazole-based derivatives were extremely potent anti-Trypanosoma cruzi agents at sub nM concentrations and exhibited a high degree of selectivity for the parasite. The 2-nitroimidazole analogs were only moderately active against T. cruzi amastigotes and exhibited low selectivity. Both types of compound were active against Leishmania donovani axenic amastigotes with excellent selectivity for the parasite, whereas three 2-nitroimidazole-based analogs were also moderately active against infected macrophages. However, no compound demonstrated selective activity against Trypanosoma brucei rhodesiense. The most potent in vitro anti-T. cruzi compounds were tested in an acute murine model and reduced the parasites to an undetectable level after five days of treatment at 13 mg/kg/day. Such compounds are potential inhibitors of T. cruzi CYP51 and, being excellent substrates for the type I nitroreductase (NTR) which is specific to trypanosomatids, work as prodrugs and constitute a new generation of effective and more affordable antitrypanosomal agents.

Novel 3-nitrotriazole-based amides and carbinols as bifunctional antichagasic agents.

3-Nitro-1H-1,2,4-triazole-based amides with a linear, rigid core and 3-nitrotriazole-based fluconazole analogues were synthesized as dual functioning antitrypanosomal agents. Such compounds are excellent substrates for type I nitroreductase (NTR) located in the mitochondrion of trypanosomatids and, at the same time, act as inhibitors of the sterol 14α-demethylase (T. cruzi CYP51) enzyme. Because combination treatments against parasites are often superior to monotherapy, we believe that this emerging class of bifunctional compounds may introduce a new generation of antitrypanosomal drugs. In the present work, the synthesis and in vitro and in vivo evaluation of such compounds is discussed.

Novel nitro(triazole/imidazole)-based heteroarylamides/sulfonamides as potential antitrypanosomal agents.

We have previously shown that 3-nitro-1H-1,2,4-triazole-based arylamides and arylsulfonamides demonstrate significant activity in vitro against Trypanosoma cruzi, the causative parasite of Chagas disease. More importantly, several such analogs displayed significant antichagasic activity in vivo, superior to that of benznidazole, the current clinical standard. We now report the synthesis and in vitro evaluation of a small series of novel nitro(triazole/imidazole)-based heteroarylamides/sulfonamides (including 3-nitrotriazole-, 2- and 4-nitroimidazole-based compounds) as potential antitrypanosomal agents. All nitrotriazoles displayed significant growth inhibitory properties against T. cruzi with the most potent generating IC50 values of <1 µM and up to >1400-fold selectivity toward the parasite. The 2-nitroimidazole-based derivatives were moderately active against T. cruzi and displayed selectivity <50, while the 4-nitroimidazoles were mostly inactive. Several 3-nitrotriazole-based analogs showed activity against Trypanosoma brucei rhodesiense but none of the tested compounds displayed activity toward Leishmania donovani. From the detailed SARs presented here, we identified the 3-nitrotriazole-based chlorinated thiophene/benzothiophene sulfonamides/amides as being the most active antichagasic compounds, displaying up to 14-fold higher potency against T. cruzi than the reference compound benznidazole.

Nitrotriazole- and imidazole-based amides and sulfonamides as antitubercular agents.

Twenty-three 3-nitrotriazole-based and 2-nitroimidazole-based amides and sulfonamides were screened for antitubercular (anti-TB) activity in aerobic Mycobacterium tuberculosis H37Rv by using the BacTiter-Glo (BTG) microbial cell viability assay. In general, 3-nitrotriazole-based sulfonamides demonstrated anti-TB activity, whereas 3-nitrotriazole-based amides and 2-nitroimidazole-based amides and sulfonamides were inactive. Three 3-nitrotriazole-based sulfonamides (compounds 4, 2, and 7) demonstrated 50% inhibitory concentration (IC50), IC90, and MIC values of 0.38, 0.43, and 1.56 µM (compound 4), 0.57, 0.98, and 3.13 µM (compound 2), and 0.79, 0.87, and 3.13 µM (compound 7), respectively. For 3-nitrotriazole-based sulfonamides, anti-TB activity increased with lipophilicity, whereas the one-electron reduction potential (E1/2) did not play a role. 2-Nitroimidazole-based analogs, which were inactive in the BTG assay, were significantly more active in the low-oxygen assay and more active than the 3-nitrotriazoles. All active nitrotriazoles in the BTG assay were similarly active or more potent (lower MIC values) against resistant strains, with the exception of compounds 2, 3, 4, and 8, which demonstrated greater MIC values against isoniazid-resistant strains. Five 3-nitrotriazole-based sulfonamides demonstrated activity in infected murine J774 macrophages, causing log reductions similar to those seen with rifampin. However, some compounds caused toxicity in uninfected macrophages. In conclusion, the classes of 3-nitrotriazole-based amides and sulfonamides merit further investigation as potential antitubercular agents.

Novel 3-nitro-1H-1,2,4-triazole-based compounds as potential anti-Chagasic drugs: in vivo studies.

BACKGROUND: Chagas disease is caused by the parasite Trypanosoma cruzi, is endemic in Latin America and leads to an estimated 14,000 deaths per year and around 100 million people at risk of infection. Drugs currently used in the treatment of Chagas are old, partially effective and have numerous side effects. METHODOLOGY: We have previously reported that 3-nitro-1H-1,2,4-triazole-based compounds demonstrate significant and selective activity against T. cruzi amastigotes in infected L6 cells via activation of a type I nitroreductase, specific to trypanosomatids. In the present work we evaluated in vivo 13 of these compounds based on their high in vitro potency against T. cruzi (IC50 < 1 µM) and selectivity (SI: toxicity to L6 cells/toxicity against T. cruzi amastigotes > 200). Representative compounds of different chemical classes were included. A fast luminescence assay with transgenic parasites that express luciferase, and live imaging techniques were used. A total of 11 out of 13 compounds demonstrated significant antichagasic activity when administered intraperitoneally for 5-10 days at relatively small doses. The best in vivo activity was demonstrated by amides and sulfonamide derivatives. ADMET studies were performed for specific compounds. CONCLUSION: At least three compounds were identified as effective, non-toxic antichagasic agents suitable for further development.

Novel 3-nitro-1H-1,2,4-triazole-based piperazines and 2-amino-1,3-benzothiazoles as antichagasic agents.

We have previously shown that 3-nitro-1H-1,2,4-triazole-based amines demonstrate significant trypanocidal activity, in particular against Trypanosoma cruzi, the causative parasite of Chagas disease. In the present work we further expanded our research by evaluating in vitro the trypanocidal activity of nitrotriazole-based piperazines and nitrotriazole-based 2-amino-1,3-benzothiazoles to establish additional SARs. All nitrotriazole-based derivatives were active or moderately active against T. cruzi; however two of them did not fulfill the selectivity criteria. Five derivatives were active or moderately active against Trypanosoma brucei rhodesiense while one derivative was moderately active against Leishmania donovani. Active compounds against T. cruzi demonstrated selectivity indexes (toxicity to host cells/toxicity to T. cruzi amastigotes) from 117 to 1725 and 12 of 13 compounds were up to 39-fold more potent than the reference compound benznidazole. Detailed SARs are discussed.

Novel 3-nitro-1H-1,2,4-triazole-based amides and sulfonamides as potential antitrypanosomal agents.

A series of novel 3-nitro-1H-1,2,4-triazole-based (and in some cases 2-nitro-1H-imidazole-based) amides and sulfonamides were characterized for their in vitro antitrypanosomal and antileishmanial activities as well as mammalian toxicity. Out of 36 compounds tested, 29 (mostly 3-nitro-1H-1,2,4-triazoles) displayed significant activity against Trypanosoma cruzi intracellular amastigotes (IC(50) ranging from 28 nM to 3.72 µM) without concomitant toxicity to L6 host cells (selectivity 66-2782). Twenty-three of these active compounds were more potent (up to 58-fold) than the reference drug benznidazole, tested in parallel. In addition, nine nitrotriazoles which were moderately active (0.5 µM ≤ IC(50) < 6.0 µM) against Trypanosoma brucei rhodesiense trypomastigotes were 5-31-fold more active against bloodstream-form Trypanosoma brucei brucei trypomastigotes engineered to overexpress reduced nicotinamide adenine dinucleotide dependent nitroreductase. Finally, three nitrotriazoles displayed a moderate activity against the axenic form of Leishmania donovani . Therefore, 3-nitro-1H-1,2,4-triazole-based amides and sulfonamides are potent antitrypanosomal agents.

Accelerated partial breast irradiation using once-daily fractionation: analysis of 312 cases with four years median follow-up.

BACKGROUND: There are limited data on accelerated partial breast irradiation (APBI) using external beam techniques. Moreover, there are recent reports of increased fibrosis and unacceptable cosmesis with APBI using external beam with BID fractionation. We adopted a once daily regimen of APBI with fractionation similar to that shown to be effective in a Canadian randomized trial of whole breast irradiation. It is unclear whether patients with DCIS or invasive lobular carcinoma (ILC) are suitable for APBI. METHODS: The retrospective cohort included 310 patients with 312 tumors of T1-T2N0-N1micM0 invasive ductal carcinoma (IDC), ILC, or Tis (DCIS) treated with APBI via external beam. Most patients were treated using IMRT with 16 daily fractions of 270 cGy to a dose of 4320 cGy. The target volume included the lumpectomy cavity plus 1.0 cm to account for microscopic disease and an additional 0.5 to 1.0 cm for setup uncertainty and breathing motion. Ipsilateral breast failure (IBF) was pathologically confirmed as a local failure (LF) or an elsewhere failure (EF). RESULTS: Median follow-up was 49 months. Among the 312 cases, 213 were IDC, 31 ILC, and 68 DCIS. Median tumor size was 1.0 cm. There were 9 IBFs (2.9%) including 5 LFs and 4 EFs. The IBF rates among patients with IDC, ILC, and DCIS were 2.4%, 3.2%, and 4.4%, respectively, with no significant difference between histologies. When patients were analyzed by the ASTRO APBI consensus statement risk groups, 32% of treated cases were considered suitable, 50% cautionary, and 18% unsuitable. The IBF rates among suitable, cautionary, and unsuitable patients were 4.0%, 2.6%, and 1.8%, respectively, with no significant difference between risk groups. Acute skin reactions were rare and long-term cosmetic outcome was very good to excellent. CONCLUSIONS: External beam APBI with once daily fractionation has a low rate of IBF consistent with other published APBI studies. The ASTRO risk stratification did not differentiate a subset of patients with a higher rate of IBF. APBI may be an appropriate treatment for women with DCIS and ILC.

Novel 3-nitro-1H-1,2,4-triazole-based aliphatic and aromatic amines as anti-chagasic agents.

A series of novel 2-nitro-1H-imidazole- and 3-nitro-1H-1,2,4-triazole-based aromatic and aliphatic amines were screened for antitrypanosomal activity and mammalian cytotoxicity by the Drugs for Neglected Diseases initiative (DNDi). Out of 42 compounds tested, 18 3-nitro-1,2,4-triazoles and one 2-nitroimidazole displayed significant growth inhibitory properties against T. cruzi amastigotes (IC(50) ranging from 40 nM to 1.97 µM), without concomitant toxicity toward the host cells (L6 cells), having selectivity indices (SI) 44-1320. Most (16) of these active compounds were up to 33.8-fold more potent than the reference drug benznidazole, tested in parallel. Five novel 3-nitro-1,2,4-triazoles were active against bloodstream-form (BSF) T. b. rhodesiense trypomastigotes (IC(50) at nM levels and SI 220-993). An NADH-dependent nitroreductase (TbNTR) plays a role in the antiparasitic activity because BSF T. b. brucei trypomastigotes with elevated TbNTR levels were hypersensitive to tested compounds. Therefore, a novel class of affordable 3-nitro-1,2,4-triazole-based compounds with antitrypanosomal activity has been identified.

Hypoxia-dependent retinal toxicity of NLCQ-1 (NSC 709257) in BALB/c mice. Comparison with tirapazamine.

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.

Investigational new drug-directed toxicology and pharmacokinetic study of 4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1, NSC 709257) in Beagle dogs.

4-[3-(2-Nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1), a 2-nitroimidazole-based hypoxia-selective cytotoxin has been shown to target hypoxic regions of solid tumours. The present study is one of several pre-clinical toxicology studies conducted in support of an 'investigational new drug' (IND) application to test this agent as an adjuvant to radio/chemotherapy for the treatment of cancer in humans. Twenty-four dogs were each assigned to one vehicle control group or to one of three test article-treated groups (three dogs/sex/treatment group). Intravenous (i.v.) doses of 0, 2.74, 5.48 and 10.95 mg/kg/day (54.8, 109.6 or 219 mg/m(2)/day) were administered on a per day x 5 days (qd x 5) schedule. NLCQ-1 was formulated as a solution in sterile saline at 1.5 mg/ml. None of the dogs died during this 33-day study. With few exceptions, most of the clinical signs of toxicity were noted within 2 hr following dosing in the 10.95 mg/kg/day dose group. These observations included aggressive behaviour, ataxia, tachypnea, emesis, hypoactivity, excessive salivation, tremors, and involuntary urination and defecation. Aggressive behaviour was judged to be dose-limiting. No clinical signs of toxicity were noted during the 28-day observation period that followed the 5-day dose period. Findings in a functional observation battery examination were consistent with the clinical observations. No drug-related effects were noted on the body weight or food consumption values, and no drug-related changes were noted during ocular examinations made on these animals prior to scheduled necropsy or during examination of electrocardiogram recordings made at 15 min. and 2 hr after dosing on days 1 and 5. No definitive changes in haematology, clinical chemistry or coagulation values were noted in dogs treated with NLCQ-1. NLCQ-1 was detected in the plasma of treated dogs on days 1 and 5, up to 60 min. after dosing (2.74 and 5.48 mg/kg/day) and up to 8 hr after dosing (10.95 mg/kg/day). There was a dose-related increase in maximum plasma concentration of NLCQ-1 at 5 min. after dosing; comparable concentrations were noted on days 1 and 5. No definitive test article-related lesions were noted during microscopic evaluation of tissues from dogs in this study, although lesions noted at the injection site and in the vascular tissue, lungs, thymus, prostate gland, muscle, adrenal cortex and tongue may have resulted from treatment with this drug. Any drug-related toxicity noted was readily reversible and not cumulative. No sex difference was detected in the susceptibility to NLCQ-1-induced toxicity.

Investigational new drug-directed, 5-day repeat dose toxicity study of 4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1, NSC 709257) administered with or without Taxol in Sprague-Dawley rats.

In pre-clinical studies, 4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1, NSC 709257) is a weak DNA-intercalating, hypoxia-selective cytotoxin with a promising profile as an adjuvant to radio/chemotherapy and it is about to enter phase I clinical trials. The present investigation was undertaken to further evaluate potential systemic toxicity induced by i.v. doses of NLCQ-1 alone or in combination with Taxol in Sprague-Dawley rats, in support of an investigational new drug application. Doses of NLCQ-1 were based on previous range-finding studies. In the present study, NLCQ-1 was administered either alone, at 0, 6, 9 or 12 mg/kg/dose to male rats and 8, 12 or 16 mg/kg/dose to female rats or, at 9 (male rats) and 12 (female rats) mg/kg/dose, in combination with Taxol, on a qd x 5 schedule. Taxol was administered i.v. at 3.5 mg/kg/dose 1 hr before NLCQ-1. Observations were recorded for mortality/moribundity, clinical signs of toxicity, body weights, food consumption, haematology, clinical chemistry, gross lesions at necropsy and histopathology. Blood samples were taken from 10 animals from each dose group on each of 2 days (days 8 and prior to scheduled necropsy on day 33). Administration of i.v. doses of NLCQ-1 alone, on a qdx5 schedule, resulted in no signs of toxicity over the 33-day study. Taxol-induced toxicity included minimal decreases in the group mean RBC, haemoglobin and haematocrit values, minimal increases in group mean reticulocyte counts (females), marked decreases in group mean neutrophil counts and minimal decreases in group mean monocyte and eosinophil counts. Lymphoid atrophy of thymus, atrophy of bone marrow and atrophy of the germinal epithelium of the testis were also associated with the administration of Taxol. There was no additional toxicity associated with the co-administration of NLCQ-1 and Taxol. In the present study, the 'no observable adverse effect level' for NLCQ-1, when administered on a qdx5 schedule, was >12 and >16 mg/kg/dose in male and female rats respectively. Daily administration of 9 (male rats) or 12 (female rats) mg/kg of NLCQ-1 1 hr after i.v. administration of Taxol (3.5 mg/kg) had no effect on Taxol-induced toxicity.

Nitroimidazole-based bioreductive compounds bearing a quinazoline or a naphthyridine chromophore.

In our search for novel bioreductive agents with weak DNA-binding characteristics, we have synthesized two new 2-nitroimidazolyl derivatives tethered to a fused aromatic-ring chromophore with two nitrogen atoms: 4-[3-(2-nitro-1-imidazolyl)-propylamino]-2-methyl-quinazoline hydrochloride (NLQZ-1) and 4-[3-(2-nitro-1-imidazolyl)-propylamino]-1,5-naphthyridine hydrochloride (NLPP-1). DNA binding was evaluated by using the ethidium bromide displacement assay. Cytotoxicity, radiosensitization, and interaction with chemotherapeutic agents were evaluated in V79 and A549 cells by using the clonogenic assay. Both compounds are not DNA intercalators and showed relatively low uptake characteristics in V79 cells. A slightly increasing hypoxic selectivity [HS = IC(50)(A)/IC(50)(H) (IC(50) is the product of a compound's concentration and the time necessary for 50% reduction in clonogenicity under aerobic (A) or hypoxic (H) conditions)] was observed with incubation time in the case of NLPP-1 (12-19 and 15-26 in V79 and A549 cells, respectively, with 1-3 h of incubation). The HS of NLQZ-1 was approximately 14, independently of incubation time. Good radiosensitization of hypoxic V79 cells was obtained with both compounds at nontoxic concentrations [the concentration for a sensitization enhancement ratio of 1.6 (C(1.6)) was 61.4 and 75.0 micromol/l for NLQZ-1 and NLPP-1, respectively]. For NLPP-1, a C(1.6) of 44.1 micromol/l was obtained in A549 cells. Both compounds interacted synergistically with cisplatin or melphalan in V79 cells, under hypoxic preexposure conditions and dose modification factors values of approximately 2.5 were obtained at 10% survival. It is concluded that although compounds that do not bind to DNA are in general less potent hypoxic cytotoxins, they can still show good HS values and interact synergistically with radiation/chemotherapeutic agents. Therefore, a further in-vivo evaluation of NLQZ-1 and NLPP-1 is worthwhile.

NLNQ-1, a 2-[3-(2-nitro-1-imidazolyl) propylamino]-3-chloro-1,4-naphthoquinone, as a hypoxia-selective cytotoxin and radiosensitizer.

BACKGROUND: Compounds bearing two independent redox centers are considered bis-bioreductive agents and usually demonstrate increased hypoxic selectivity with exposure time due to different requirements for reduction of each center. We have synthesized a novel 2-[3-(2-nitro-1-imidazolyl)propylamino]-3-chloro-1,4-naphthoquinone (NLNQ-1), through Michael addition. NLNQ-1, which combines a naphthoquinone (with a relatively high one electron reduction potential) with a 2-nitroimidazole (with a relatively low one electron reduction potential), could perform as a more potent hypoxia-selective cytotoxin and radiosensitizer. MATERIALS AND METHODS: NLNQ-1 was evaluated in V79 cells under hypoxic/normoxic conditions, alone or with radiation, by using the clonogenic assay. RESULTS: Clearly NLNQ-1 was a more potent cytotoxin than the 2-alkylsulfonyloxy-naphthoquinones (VH-compounds), developed previously in our lab, demonstrating hypoxic and aerobic IC50 values at microM rather than mM concentrations. As a radiosensitizer of hypoxic cells, NLNQ-1 was superior to the best bis-nitroimidazolic compound, NNB (which combines a 2-nitroimidazole with a 5-nitroimidazole), demonstrating a C1.6 value of 25.4 microM (ca. 25 fold lower than that of NNB), whereas its in vitro therapeutic index (IC50A/C1.6) ranged from 5.3-13.2. CONCLUSION: NLNQ-1 could be used as a novel scaffold for bis-bioreductive agents that can be properly modified for further optimization of their hypoxia-selective toxicity and radiosensitization properties.