Evaluation of the antitumor activity of NOV202, a novel microtubule targeting and vascular disrupting agent

Purpose

Overall, ~65% of patients diagnosed with advanced ovarian cancer (OC) will relapse after primary surgery and adjuvant first-line platinum- and taxane-based chemotherapy. Significant improvements in the treatment of OC are expected from the development of novel compounds having combined cytotoxic and antiangiogenic properties that make them effective on refractory tumors.

Methods

Permeability of NOV202 was determined with Caco-2 monolayer assay. The compound’s pharmacokinetic profile and plasma:brain distribution were assessed in male C57Bl/6 mice. The compound’s impacts on tubulin, microtubules and cell cycle were investigated by using in vitro tubulin polymerization assay, cell-based immunofluorescence and live cell microscopy. The IC₅₀ concentrations of NOV202 were assessed in a panel of eight cancer cell lines. Impact of the compound on vascular tube formation was determined using the StemKit and Chick chorioallantoic membrane assays. The in vivo efficacy of the compound was analyzed with an OC xenograft mouse model.

Results

NOV202 was found to suppress cancer cell proliferation at low nanomolar concentrations (IC₅₀ 2.3–12.0 nM) and showed equal efficacy between OC cell line A2780 (IC₅₀ 2.4 nM) and its multidrug-resistant subline A2780/Adr (IC₅₀ 2.3 nM). Mechanistically, NOV202 targeted tubulin polymerization in vitro in a dose-dependent manner and in cells induced an M phase arrest. In vivo, NOV202 caused a dose-dependent reduction of tumor mass in an A2780 xenograft model, which at the highest dose (40 mg/kg) was comparable to the effect of paclitaxel (24 mg/kg). Interestingly, NOV202 exhibited vascular disrupting properties that were similar to the effects of Combretastatin A4.

Conclusion

NOV202 is a novel tubulin and vascular targeting agent that shows strong anticancer efficacy in cells and OC xenograft models. The finding that the compound induced significantly more cell death in Pgp/MDR1 overexpressing OC cells compared to vincristine and paclitaxel warrants further development of the compound as a new therapy for OC patients with treatment refractory tumors and/or relapsing disease.

Doppler ultrasound estimation of microbubbles in the arterial line during extracorporeal circulation

A pulsed Doppler ultrasound system was used to analyse microbubble intensity and size in the arterial line during extracorporeal circulation (ECC). Thirty male patients, younger than 70 (range 28-69) years, underwent isolated coronary artery bypass grafting with either a bubble oxygenator (Shiley S-100) without (group 1, n = 10) or with (group 2, n = 10) a depth adsorption arterial line filter (Swank High Flow 6000); or with a membrane oxygenator (Shiley M-2000) without a filter (group 3, n = 10). Mean ECC and aortic crossclamp times were similar in the three groups. Measurements were performed during the initial five minutes of cooling, after 30-40 minutes of ECC and after 10 minutes of rewarming. Microbubble intensity and size did not differ significantly in the three groups at the different intervals. Significantly more and larger bubbles were detected in group 1 (15-150μm) compared to group 2 (< 35μm) (p< 0.001). In group 3 only a minimal number of small bubbles (< 65μm) were observed. An arterial line filter significantly reduced the number and size of microbubbles detected in the arterial line during ECC. A membrane oxygenator was associated with a further reduction of microbubble intensity.

Abstract A298: CHE202: A novel oral active microtubule depolymerizing vascular disrupting agent

Purpose: Microtubule targeting agents, represented by vinca alkaloids and taxanes, are extensively used in the clinic with good effects. However, these large molecules can only be administered by intravenous injections to the patient and they are also often substrates for Pgp efflux pumps which may lead to drug resistance and tumor progression. Thus, there is an unmet medical need for novel small molecule microtubule targeting agents with improved properties and less prone to development of tumor resistance than currently approved drugs.

Methods: Cell viability was measured with the fluorometric microculture cytotoxicity assay. Tubulin polymerization and colchicine displacement were performed in a cell free tubulin assay. For cell cycle experiments, apoptosis assays, and vascular disruption studies, a live cell imaging instrument were used. Human tumor xenografts of A2780 cells in NMRI nu/nu mice were used for in vivo efficacy studies.

Results: A series of small molecule compounds were synthesized and screened for cytotoxicity in a large panel of cancer cell lines as well as on normal cells. CHE202 was identified as one of the most potent compounds on a large number of cancer cell lines, with IC50-values in the low nM range (2 -12 nM), and significantly less cytotoxicity on normal cells. In the multidrug-resistant cell line A2780/Adr, CHE202 was shown to have similar IC50-values as in the parent cell line, indicating that CHE202 is not a substrate for P-glycoprotein-mediated drug efflux. Gene expression analysis in cells exposed to CHE compounds caused down regulation of tubulin genes and a similar gene-expression pattern as other tubulin-active compounds, indicating that CHE202 is a microtubule active compound. Further in vitro studies confirmed that CHE202 exert its cytotoxic activity through disruption of microtubule networks in living cells and inhibition of tubulin polymerization, causing G2/M arrest and cell death through apoptosis. Molecular modeling and a colchicine binding assay demonstrated that CHE202 binds to the colchicine-site of tubulin. In an angiogenesis assay, CHE202 was found to act as a vascular disrupting agent with activity in the sub-nM range on neo-angiogenesis and in the nM range on established blood vessels. In vivo efficacy studies, in an ovarian cancer xenograft model (A2780), showed that CHE202 administered by the oral route caused around 80% reduction of tumor volume, which was in the same range as the gold standard, paclitaxel.

Conclusions: CHE202 is an oral active novel microtubule targeting and vascular disrupting agent with nanomolar potency on several cancer cell lines, as well as on multidrug-resistant cancer cells. These results warrant further development of CHE202 towards the clinic.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A298.

Citation Format: Marita Högberg, Linda Rickardson, Emma Dahlstedt, Mikael Gillner, Tommy Johansson, Ivan Romero, Olof Smitt. CHE202: A novel oral active microtubule depolymerizing vascular disrupting agent. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A298.

Isolation and characterization of a small antiretroviral molecule affecting HIV-1 capsid morphology

Background

Formation of an HIV-1 particle with a conical core structure is a prerequisite for the subsequent infectivity of the virus particle. We have previously described that glycineamide (G-NH₂) when added to the culture medium of infected cells induces non-infectious HIV-1 particles with aberrant core structures.

Results

Here we demonstrate that it is not G-NH₂ itself but a metabolite thereof that displays antiviral activity. We show that conversion of G-NH₂ to its antiviral metabolite is catalyzed by an enzyme present in bovine and porcine but surprisingly not in human serum. Structure determination by NMR suggested that the active G-NH₂ metabolite was α-hydroxy-glycineamide (α-HGA). Chemically synthesized α-HGA inhibited HIV-1 replication to the same degree as G-NH₂, unlike a number of other synthesized analogues of G-NH₂ which had no effect on HIV-1 replication. Comparisons by capillary electrophoresis and HPLC of the metabolite with the chemically synthesized α-HGA further confirmed that the antiviral G-NH₂-metabolite indeed was α-HGA.

Conclusion

α-HGA has an unusually simple structure and a novel mechanism of antiviral action. Thus, α-HGA could be a lead for new antiviral substances belonging to a new class of anti-HIV drugs, i.e. capsid assembly inhibitors.

Bioisosteric modification of PETT-HIV-1 RT-inhibitors: synthesis and biological evaluation

Bioisosteric substitution of the thiourea (3, 5, 7, 9) and urea (10) moiety of PETT compounds with sulfamide (1), cyanoguanidine (2, 4) and guanidine (6, 8) functionalities, and replacement of the phenethyl group with benzoylethyl group (compounds 11-20) have been studied. Synthesis and antiviral activities are described.

Urea-PETT compounds as a new class of HIV-1 reverse transcriptase inhibitors. 3. Synthesis and further structure-activity relationship studies of PETT analogues

The further development of allosteric HIV-1 RT inhibitors in the urea analogue series of PETT (phenylethylthiazolylthiourea) derivatives is described here. The series includes derivatives with an ethyl linker (1-5) and racemic (6-16) and enantiomeric (17-20) cis-cyclopropane compounds. The antiviral activity was determined both at the RT level and in cell culture on both wild-type and mutant forms of HIV-1. Most compounds have anti-HIV-1 activity on the wt in the nanomolar range. Resistant HIV-1 was selected in vitro for some of the compounds, and the time for resistant HIV-1 to develop was longer for urea-PETT compounds than it was for reference compounds. Preliminary pharmacokinetics in rats showed that compound 18 is orally bioavailable and penetrates well into the brain. The three-dimensional structure of complexes between HIV-1 RT and two enantiomeric compounds (17 and 18) have been determined. The structures show similar binding in the NNI binding pocket. The propionylphenyl moieties of both inhibitors show perfect stacking to tyrosine residues 181 and 188. The cyclopropyl moiety of the (+)-enantiomer 18 exhibits optimal packing distances for the interactions with leucine residue 100 and valine residue 179.

Synthesis and anti-HIV activities of urea-PETT analogs belonging to a new class of potent non-nucleoside HIV-1 reverse transcriptase inhibitors

A series of potent specific HIV-1 RT inhibitory compounds is described. The compounds are urea analogs of PETT (PhenylEthylThiazoleThiourea) derivatives and the series includes derivatives with an ethyl linker (1-6) and conformationally restricted analogs (7-13). The antiviral activity is determined both at the RT level and in cell culture on both native and mutant forms of HIV-1. Many compounds display activity in the nM range against wt-RT.

Evaluation of the Q16 questionnaire on neurotoxic symptoms and a review of its use

OBJECTIVES

The questionnaire 16 (Q16) is commonly used to study prevalences of neurotoxic symptoms among workers exposed to organic solvents. It has also been recommended that exposed workers reporting more than six symptoms should be referred for further examination of possible chronic toxic encephalopathy. It would be useful to know whether symptoms reported in the questionnaire also reflect impairment of similar functions measured with objective or semiobjective methods in a formerly highly exposed group.

METHODS

135 painters and 71 carpenters answered the Q16, were interviewed about symptoms compatible with an organic brain damage, and took a battery of psychometric tests. A subsample of 52 painters and 45 carpenters were interviewed for psychiatric diagnosis according to Diagnostic and Statistical Manual for Mental Disorders, 3rd version (DSM III) and their vibration thresholds in hands and feet were measured. The entire group was followed up in the register of diagnoses at early retirement 1971-93. The lifetime exposure to organic solvents was assessed. Current exposure to organic solvents was found to be low or none.

RESULTS

The prevalence of people with more than six symptoms in the Q16 rose with increasing cumulative exposure to solvents. The sensitivity of the questionnaire (more than six symptoms) to detect people who were assessed to exhibit symptoms compatible with an organic brain damage was only 38%. One of seven people who had retired early with a diagnosis compatible with a chronic toxic encephalopathy, and two of five people with a psychiatric diagnosis compatible with this condition, had more than six symptoms in the Q16. The agreement between Q16 replies and psychometric test results, as well as other examinations, was low.

CONCLUSIONS

The notable exposure-response relation indicates that the questionnaire is useful for comparison of groups with different exposures to organic solvents. There was low agreement between the number of symptoms on the questionnaire and the assessment of symptoms compatible with organic brain damage, as well as psychiatric, or early retirement diagnoses compatible with chronic toxic encephalopathy. The questionnaire does not seem useful for screening of patients with chronic toxic encephalopathy in groups without ongoing exposure to organic solvents.

Phenethylthiazolylthiourea (PETT) compounds as a new class of HIV-1 reverse transcriptase inhibitors. 2. Synthesis and further structure-activity relationship studies of PETT analogs

Phenylethylthiazolylthiourea (PETT) derivatives have been identified as a new series of non-nucleoside inhibitors of HIV-1 RT. Structure-activity relationship studies of this class of compounds resulted in the identification of N-[2-(2-pyridyl)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea hydrochloride (trovirdine; LY300046.HCl) as a highly potent anti-HIV-1 agent. Trovirdine is currently in phase one clinical trials for potential use in the treatment of AIDS. Extension of these structure-activity relationship studies to identify additional compounds in this series with improved properties is ongoing. A part of this work is described here. Replacement of the two aromatic moieties of the PETT compounds by various substituted or unsubstituted heteroaromatic rings was investigated. In addition, the effects of multiple substitution in the phenyl ring were also studied. The antiviral activities were determined on wild-type and constructed mutants of HIV-1 RT and on wild-type HIV-1 and mutant viruses derived thereof, Ile100 and Cys181, in cell culture assays. Some selected compounds were determined on double-mutant viruses, HIV-1 (Ile 100/Asn103) and HIV-1 (Ile100/Cys181). A number of highly potent analogs were synthesized. These compounds displayed IC50's against wild-type RT between 0.6 and 5 nM. In cell culture, these agents inhibited wild-type HIV-1 with ED50's between 1 and 5 nM in MT-4 cells. In addition, these derivatives inhibited mutant HIV-1 RT (Ile 100) with IC50's between 20 and 50 nM and mutant HIV-1 RT (Cys 181) with IC50's between 4 and 10 nM, and in cell culture they inhibited mutant HIV-1 (Ile100) with ED50's between 9 and 100 nM and mutant HIV-1 (Cys181) with ED50's between 3 and 20 nM.

Phenethylthiazolethiourea (PETT) compounds, a new class of HIV-1 reverse transcriptase inhibitors. 1. Synthesis and basic structure-activity relationship studies of PETT analogs

A novel series of potent specific HIV-1 inhibitory compounds is described. The lead compound in the series, N-(2-phenethyl)-N'-(2-thiazolyl)thiourea (1), inhibits HIV-1 RT using rCdG as the template with an IC50 of 0.9 microM. In MT-4 cells, compound 1 inhibits HIV-1 with an ED50 of 1.3 microM. The 50% cytotoxic dose in cell culture is > 380 microM. The chemical structure-activity relationship (SAR) was developed by notionally dividing the lead compound in four quadrants. The SAR strategy had two phases. The first phase involved optimization of antiviral activity through independent variation of quadrants 1-4. The second phase involved the preparation of hybrid structures combining the best of these substituents. Further SAR studies and pharmacokinetic considerations led to the identification of N-(2-pyridyl)-N'-(5-bromo-2-pyridyl)-thiourea (62; LY300046.HCl) as a candidate for clinical evaluation. LY300046.HCl inhibits HIV-1 RT with an IC50 of 15 nM and in cell culture has an ED50 of 20 nM.

Liver function tests and urinary albumin in house painters with previous heavy exposure to organic solvents

The serum activities or concentrations of aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), alkaline phosphatase (ALP), albumin, gamma-glutamyl transpeptidase (GGT), bilirubin (BIL), cholic acid (CHOL), chenodeoxycholic acid (CHENO), and transferrin with isoelectric point 5.7, and the urinary excretion of albumin were determined among male current or former house painters (n = 135) and house carpenters (n = 71) who had worked in their trades for at least 10 years before 1970. Workers who showed a value above the 90th percentile among the carpenters in at least one of the tests ASAT, ALAT, GGT, BIL, CHOL, or CHENO were regarded as showing "possible signs of liver dysfunction". Each participant's lifetime solvent exposure was evaluated by interview. The painters were divided into categories with low, intermediate, and heavy cumulative exposure during life (LTSE) or during the most exposed year (MEYSE). All participants stated none or slight recent exposure. The prevalence of possible signs of liver dysfunction increased with solvent exposure category according to LTSE as well as MEYSE with a numerically higher risk estimate in the heavy exposure category for MEYSE than for LTSE. ALP activity increased with exposure category according to both exposure estimates. This increase seemed to be due to an interaction between exposure to solvents and current or previous long term intake of medicines potentially toxic to the liver. None of these results was affected by whether or not the subjects had been exposed to solvents during the year before the investigation. The exposure to solvents was not significantly related to any other outcome variable. It is concluded that long term heavy exposure to solvents may elicit changes in conventional liver function tests indicative of a mild chronic effect on the liver. The findings also suggest that heavy solvent exposure during short time periods is a more likely cause of the findings than lifetime cumulative solvent exposure and that an interaction between solvent exposure and medicines potentially harmful to the liver may be important in the causation of the effects.

Health screening for occupational dermatoses in house painters

During 1976-77 a field investigation was carried out into skin diseases among house painters in Stockholm, Sweden. The study was divided into three stages: I. questionnaires investigation, II. examination of painters who reported skin diseases, and III. patch testing and final classification. Of the 2,622 painters registered on 30 November 1976, 2239 (85.4%) answered the questionnaire. Current dermatoses were reported by 373 painters (16.7%) and of these, 227 were examined by us, 40 had recently been examined, and 106 did not attend. Occupational contact eczemas were diagnosed in 87 cases, and it was doubtful if the dermatoses were occupational in an additional 56 cases. A prevalence of 3.9% was suggested, but this represents a minimum figure. Chloracetamide was found to be an important cause of occupational contact eczema. A personal and/or family history of atopy was common among the affected painters. Solvents were widely used for skin cleansing; there is a great need for continuous information on protective measurements, and on skin cleansing and care. It is concluded that field investigation give higher and probably more reliable prevalence figures for occupational dermatoses than data compiled from outpatient clinics.