A new antitumor agent: methyl sulfonium perchlorate of echinomycin

Veno-occlusive disease (VOD) is a serious complication of myeloablative therapy and stem cell transplantation. We here describe a case of VOD in a patient with acute myeloid leukemia (AML), who received an autologous peripheral blood stem cell graft after busulphan/cyclophosphamide conditioning in first complete remission and who developed severe VOD at day 17. Color-flow sonography of the portal and hepatic veins revealed hepatofugal blood flow in the portal vein and an absence of flow in the hepatic vein. Treatment with recombinant tissue plasminogen activator (t-PA) was started at a dose of 10 mg/day and increased to 20 mg/day because color-flow sonography indicated no change of blood flow. Daily sonography was continued to monitor the portal and hepatic blood flow in order to assess the need for continuation of t-PA. Once an objective sonographic improvement was observed, t-PA treatment was tapered and stopped. This case demonstrates that color-flow sonography can be used to confirm the clinical diagnosis of VOD. Furthermore this technique provides a way for easily and reliably evaluating the effect in relation to dose of thrombolytic therapy needed. It improves the quality of clinical monitoring which is needed for effective treatment of VOD while minimizing the risk of serious bleeding complications.     

Sirolimus, a new, potent immunosuppressive agent

Sirolimus (SRL), a potent immunosuppressant, is currently being investigated in phase III trials for prophylaxis of renal transplant rejection. The mechanism of action of SRL is a blockade of the response of T and B cells to cytokines, thereby preventing cell cycle progression in G1 and consequently cell proliferation. There seems to be a good correlation between SRL concentrations, estimated as exposure by the area under the concentration versus time curve, and trough whole blood concentration, so that therapeutic monitoring may be done by trough levels only. Because of the low frequency of allograft rejection, there has been no documented correlation between trough concentrations and efficacy. Trough SRL concentrations of 15 ng/ml or higher seem to be associated with an increased frequency of adverse effects. Drug-associated toxicities include thrombocytopenia, leukopenia, and increases in cholesterol and triglyceride levels. The drug has synergy with cyclosporine (CsA) in vitro as well as in animal and clinical studies. In phase II trials the combination of SRL-CsA therapy reduced the frequency of acute rejection episodes, permit withdrawal of concomitant corticosteroid therapy, and allowed reduction of CsA dosages in nonblack patients.     

Synthesis, cytotoxicity and antitumor activity of some new simplified pyrazole analogs of the antitumor agent CC-1065. Effect of an hydrophobic group on antitumor activity

Three simplified pyrazole analogs (7-9) of the antitumor agents CC-1065, were synthesized. In in vitro assays, against L1210 cell lines all derivatives showed a cytotoxicity in a pM range, values close to the natural target compound (+)-CC-1065. In in vivo tests, against disseminate L1210 leukemia cells, synthesized compounds showed a good potency (O.D. 300 micrograms/Kg) but no activity. These observations further validate the effect of the hydrophilic and/or hydrophobic characteristics of the substituents present on the molecules, confirming the relevance of this phenomena on in vivo activity. In fact in this case the increase of hydrophobic characteristics of the molecules produce the loss of activity, probably due to a worse bioavailability of the drugs in animals.     

A new screening system for NAD(P)H:quinone oxidoreductase (NQO1)-directed antitumor quinones: identification of a new aziridinylbenzoquinone, RH1, as a NQO1-directed antitumor agent

NAD(P)H:quinone oxidoreductase (NQO1; DT-diaphorase) is elevated in certain tumors, such as non-small cell lung cancer (NSCLC). Compounds such as mitomycin C and streptonigrin are efficiently bioactivated by NQO1 and have been used in an enzyme-directed approach to chemotherapy. Previously, 2,5-diaziridinyl-3,6-dimethyl-1,4-benzoquinone (MeDZQ) was identified as a potential antitumor agent based on its high rate of bioactivation by human NQO1 and its selective cytotoxicity to cells containing elevated NQO1. RH1, a water-soluble analogue of MeDZQ synthesized in this work, was a better substrate for recombinant human NQO1 than the parent compound. RH1 was, correspondingly, more cytotoxic to human tumor cells expressing elevated NQO1 activity (H460 NSCLC and HT29 human colon carcinoma), as measured by 3-(4,5-dimethylthiazol-2,5-diphenyl)tetrazolium assay, than it was to cells deficient in NQO1 activity (H596 NSCLC and BE human colon carcinoma). RH1 exhibited a greater selective toxicity (ratio of IC50s in H596:H460 and BE:HT29) to cells with elevated NQO1 activity relative to MeDZQ. Additionally, we report the establishment of a stable line of BE human colon carcinoma cells transfected with wild-type human NQO1 (BE-NQ7). BE cells are devoid of NQO1 activity due to a homozygous point mutation in the NQO1 gene. In comparison to the parental cell line, RH1, MeDZQ, and mitomycin C were significantly more cytotoxic to BE-NQ7 cells (17-, 7-, and 3-fold, respectively), confirming that the presence of NQO1 is sufficient to increase cytotoxicity of these antitumor quinones. These data suggest that RH1 may be an effective NQO1-directed antitumor agent for the therapy of tumors with elevated NQO1 activity, such as NSCLC.     

Monohydroxyethylrutoside, a dose-dependent cardioprotective agent, does not affect the antitumor activity of doxorubicin

The cumulative dose-related cardiotoxicity of doxorubicin is believed to be caused by the production of oxygen- free radicals. 7-Monohydroxyethylrutoside (monoHER), a semisynthetic flavonoid and powerful antioxidant, was investigated with respect to the prevention of doxorubicin-induced cardiotoxicity in mice and to its influence on the antitumor activity of doxorubicin in vitro and in vivo. Non-tumor-bearing mice were equipped with a telemeter in the peritoneal cavity. They were given six weekly doses of 4 mg/kg doxorubicin i.v., alone or in combination with either 100 or 250 mg/kg monoHER i.p., 1 h prior to doxorubicin administration and for the following 4 days. Cardiotoxic effects were measured from electrocardiogram changes up to 2 weeks after treatment. Protection against cardiotoxicity was found to be dose dependent, with 53 and 75% protection, respectively, as calculated from the reduction in the increase in the ST interval. MonoHER and several other flavonoids with good antioxidant properties were tested for their antiproliferative effects in the absence or the presence of doxorubicin in A2780 and OVCAR-3 human ovarian cancer cells and MCF-7 human breast cancer cells in vitro. Some flavonoids were directly toxic at 50 and 100 microM, whereas others, including monoHER, did not influence the antiproliferative effects of doxorubicin at these concentrations. The influence of monoHER was further tested on the growth-inhibitory effect of 8 mg/kg doxorubicin i.v., given twice with an interval of 1 week in A2780 and OVCAR-3 cells that were grown as s.c. xenografts in nude mice. MonoHER, administered 1 h before doxorubicin in a dose schedule of 500 mg/kg i.p. 2 or 5 days per week, was not toxic and did not decrease the antitumor activity of doxorubicin. It can be concluded that monoHER showed a dose-dependent protection against chronic cardiotoxicity and did not influence the antitumor activity of doxorubicin in vitro or in vivo.     

Dynamic compatibility testing of DMP 840, an experimental antitumor agent

The purpose of this study is to evaluate the potential for DMP 840, a novel experimental antitumor agent, to precipitate during injection or dilution with infusion solutions. The influence of predilution of the drug solution before injection and addition of buffers to the drug vehicle were also investigated. The compatibility of normal saline solution, pH 7.4 phosphate buffers, and human plasma with DMP 840 was examined in vitro under both static conditions and dynamic flow. The combination of DMP 840 solutions with normal saline solution resulted in conversion of the drug to an insoluble dihydrochloride salt. Under conditions of dynamic flow, precipitation, accompanied by large changes in turbidity, occurred at relatively high concentrations of the drug in the injection solution. Dilution of the injection solution below 2 mg/mL or slow injection avoided precipitation. As was the case with the normal saline system, turbidity changes after injection into protein-phosphate buffer (PPB) were dependent on the initial concentration of DMP 840 solution as well as the rate of administration. In addition, the maximum injection rate at which complete miscibility occurred increased exponentially as the drug injection solution was made more dilute. Buffering the DMP 840 injection solution with acetate buffer improved the miscibility of DMP 840 with PPB, which indicated that the turbidity increases were most likely due to conversion of the drug to its insoluble free base form. The observed effects of the buffer on the turbidity response agreed qualitatively with predictions from a graphical approach that considers the effects of dilution and pH changes on drug solubility. Despite these observations, no evidence for the formation of a solid precipitate could be found after injection of the unbuffered drug solution into PPB. Further investigation indicated that the presence of albumin in the PPB prevented the formation of a solid phase during injection. Likewise, fresh human plasma, spiked with 1 and 2 mg/mL solutions of DMP 840, showed no evidence for the formation of a solid precipitate.     

A new antitumor agent amrubicin induces cell growth inhibition by stabilizing topoisomerase II-DNA complex

Amrubicin is a novel, completely synthetic 9-aminoanthracycline derivative. Amrubicin and its C-13 alcohol metabolite, amrubicinol, inhibited purified human DNA topoisomerase II (topo II). Compared with doxorubicin (DXR), amrubicin and amrubicinol induced extensive DNA-protein complex formation and double-strand DNA breaks in CCRF-CEM cells and KU-2 cells. In this study, we found that ICRF-193, a topo II catalytic inhibitor, antagonized both DNA-protein complex formation and double-strand DNA breaks induced by amrubicin and amrubicinol. Coordinately, cell growth inhibition induced by amrubicin and amrubicinol, but not that induced by DXR, was antagonized by ICRF-193. Taken together, these findings indicate that the cell growth-inhibitory effects of amrubicin and amrubicinol are due to DNA-protein complex formation followed by double-strand DNA breaks, which are mediated by topo II.     

Structure-activity relationships of the 7-substituents of 5,4'-diamino-6,8,3'-trifluoroflavone, a potent antitumor agent

Recently, we reported that 5,4'-diamino-6,8,3'-trifluoroflavone (1b) exhibits potent antitumor activity against certain types of human cancer cell lines both in vitro and in vivo. Since the antiproliferative activity of 5,4'-diaminoflavone (1a), the lead compound of 1b, was modulated by the addition of apigenin, we hypothesized that the 7-position is important for the interaction with a putative target molecule. On the basis of this hypothesis, the structure-activity relationships of the substituents at the 7-position of 1b were explored. As a result, 7-methyl (7a), 7-hydroxymethyl (7l), 7-(acyloxy)methyl (9a,c,e,g,j), and 7-aminomethyl (12f) derivatives were found to exhibit comparable or superior antitumor activity to compound 1b against MCF-7 cells both in vitro and in vivo (po administration). In particular, compounds 9e,g,j, and 12f were sufficiently water-soluble as compared with 1b which hardly solubilizes in water. A lipophilic 7-(hexanoyloxy)methyl derivative (9c) was also found to exhibit strong antitumor activity especially in vivo. Since the modes of action and the target molecule(s) are unknown, a mechanistic study will be important in the future.     

Interaction between enoxacin, a new antimicrobial, and nimesulide, a new non-steroidal anti-inflammatory agent in mice

Convulsions induced by the combination of enoxacin, a new antimicrobial, and nonsteroidal anti-inflammatory drugs including nimesulide, ketoprofen, pranoprofen and loxoprofen sodium, were investigated in mice. The oral administration of nimesulide alone induced clonic convulsions at more than 300 mg/kg. The oral administration of ketoprofen, pranoprofen or loxoprofen sodium induced no convulsion up to 1000 mg/kg, 500 mg/kg and 600 mg/kg, respectively, and that of enoxacin induced no convulsion at more than 5000 mg/kg. The combination of nimesulide at 200 mg/kg and enoxacin at 400 mg/kg induced no convulsion. In contrast, the combination of enoxacin at 100 mg/kg and either ketoprofen at 125 mg/kg or pranoprofen at 500 mg/kg induced clonic convulsions, while that of enoxacin at 400 mg/kg and loxoprofen sodium at 600 mg/kg induced no convulsion. These results suggest that the combination of nimesulide and enoxacin may possibly induce few or less convulsions in the clinical setting.     

Combined analysis of two studies using the conjunctival allergen challenge model to evaluate olopatadine hydrochloride, a new ophthalmic antiallergic agent with dual activity

PURPOSE: To evaluate the effectiveness and safety of olopatadine hydrochloride and to determine its optimal concentration and the onset and duration of action for treating allergic conjunctivitis. Olopatadine is a new topical ophthalmic antiallergic agent that demonstrates activity as both an antihistamine and a mast cell stabilizer. Two double-masked, randomized, placebo-controlled, contralateral eye comparison studies were conducted using the conjunctival allergen challenge model. METHODS: A total of 169 subjects received 0.05% or 0.1% olopatadine. Study subjects were healthy adult men and women with a history of active allergic conjunctivitis within the previous two seasons but not receiving current treatment. With an allergen dose that produced signs and symptoms of allergic conjunctivitis at visits 1 and 2, the conjunctival allergen challenge was performed 27 minutes after study drug administration at the third visit (onset-of-action challenge) and at 8 hours after study drug administration at the fourth visit (duration-of-action challenge). Olopatadine was administered in one eye and placebo in the opposite eye. Itching and redness were scored for both eyes at 3, 10, and 20 minutes after the conjunctival allergen challenge. RESULTS: Both 0.05% and 0.1% concentrations of olopatadine were significantly (P < .05) more effective than placebo in inhibiting itching and redness at all evaluations when administered 27 minutes or 8 hours before the conjunctival allergen challenge. There were no serious or drug-related ocular or nonocular adverse events in either study. CONCLUSION: These findings demonstrate the rapid and prolonged (at least 8 hours) ocular antiallergic action of olopatadine.     

Selective proteolytic activity of the antitumor agent kedarcidin

Kedarcidin is a potent antitumor antibiotic chromoprotein, composed of an enediyne-containing chromophore embedded in a highly acidic single chain polypeptide. The chromophore was shown to cleave duplex DNA site-specifically in a single-stranded manner. Herein, we report that in vitro, the kedarcidin apoprotein, which lacks any detectable chromophore, cleaves proteins selectively. Histones that are the most opposite in net charge to the apoprotein are cleaved most readily. Our findings imply that the potency of kedarcidin results from the combination of a DNA damaging-chromophore and a protease-like apoprotein.     

Dual topoisomerase I and II inhibition by intoplicine (RP-60475), a new antitumor agent in early clinical trials

The mechanisms of action of intoplicine (RP-60475), a 7H-benzo[e]pyrido[4,3-b]indole derivative that is presently in early clinical trials, have been investigated. Intoplicine induced both topoisomerase I- and II-mediated DNA strand breaks, using purified topoisomerases. The topoisomerase cleavage site patterns induced by intoplicine were unique, relative to those of camptothecin, 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA), and other known topoisomerase inhibitors. Both topoisomerase I- and II-induced DNA breaks decreased at drug concentrations higher than 1 microM, which is consistent with the DNA-intercalating activity of intoplicine. DNA damage was investigated in KB cells in culture by using alkaline elution. Intoplicine induced single-strand breaks (SSB) in a bell-shaped manner with respect to drug concentration (maximum frequency at 1 microM approximately 220 rad-equivalents). SSB formation was fast, whereas reversal after drug removal was slow. Similar bell-shaped curves were obtained for DNA double-strand breaks (DSB) and DNA-protein cross-links. SSB and DNA-protein cross-link frequencies were approximately equal, and no protein-free breaks were detectable, indicating the protein concealment of the breaks, as expected for topoisomerase inhibition. Comparison of SSB and DSB frequencies indicated that intoplicine produced a significant amount of SSB not related to DSB, which is consistent with concomitant inhibition of both DNA topoisomerases I and II in cells. Data derived from resistant cell lines indicated that multidrug-resistant cells were cross-resistant to intoplicine but that m-AMSA- and camptothecin-resistant cells were sensitive to intoplicine. Hence, intoplicine might circumvent topoisomerase I-mediated and topoisomerase II-mediated resistance by poisoning both enzymes simultaneously.     

Taxol: the chemistry and structure-activity relationships of a novel anticancer agent

Taxol is an exciting new anticancer drug, showing clinical activity against ovarian and breast cancer. Its development as a clinically useful drug has involved major efforts to overcome the supply problem; this has now been done, and the focus of interest has moved to the development of improved analogs of the drug. Recent notable achievements include the first total synthesis of taxol, and the first indications of its binding site on tubulin.     

Chronotropic effects of cilostazol, a new antithrombotic agent, in patients with bradyarrhythmias

Size and asymmetry (size difference between the left and right sides) of inner ear otoliths of larval cichlid fish were determined after a long-term stay in moderate hypergravity conditions (3g; centrifuge), in the course of which the animals completed their ontogenetic development from hatch to freely swimming. Neither the normal morphogenetic development nor the timely onset and gain of performance of swimming behaviour were impaired by the experimental conditions. However, both utricular and saccular otoliths (lapilli and sagittae, respectively) were significantly smaller after hyper-g exposure compared to 1g control specimens raised in parallel. The asymmetry of sagittae was significantly increased in the experimental animals, whereas the respective asymmetry of lapilli was pronouncedly decreased compared with the 1g controls. These findings suggest that growth and development of bilateral asymmetry of otoliths are guided by the environmental gravity vector. Some of the hyper-g animals revealed a kinetotic behaviour on transfer to normal 1g earth conditions, which was similar to the behaviour observed in previous experiments on the transfer from 1g to microgravity (parabolic aircraft flights). The lapillar asymmetry of kinetotic samples was found to be significantly higher than that of normally behaving experimental specimens. No differences in asymmetry of sagittae were obtained between the two groups. This supports an earlier theoretical concept, according to which human static space sickness might be based on asymmetric utricular otoliths.     

Resveratrol as a new type of DNA-cleaving agent

The first demonstration of DNA cleavage by resveratrol '3,5,4'-trihydroxy-trans-stilbene' is presented. Resveratrol mediated relaxation of pBR322 at micromolar concentrations in the presence of Cu2+. Evidence is provided that resveratrol is capable of binding to DNA, and that the Cu(2+)-dependent DNA damage is more likely caused by a copper-peroxide complex rather than by a freely diffusible oxygen species.