Activity Of Novel Compounds Research Articles

Activation of the cloned human NK3 receptor in Chinese Hamster Ovary cells characterized by the cellular acidification response using the Cytosensor microphysiometer.

1. The aim of the present study was to validate the Cytosensor microphysiometer, a novel system that measures the extracellular acidification rate as a reliable index of the integrated functional response to receptor activation, as a method for studying NK3 receptor pharmacology, and then to use this system to assess the functional activity of novel compounds at this receptor. 2. The selective NK3 agonist senktide caused reproducible, concentration-related increases in acidification ratein CHO-NK3 cells, with a pEC50 value of 8.72+/-0.11 (n=15). [Beta-Ala8]NKA(4-10), the selective NK2 agonist, elicited a much weaker response (pEC50=6.68+/-0.08, n=4), while the NK1-selective agonist substance P methylester only caused a very weak response at concentrations > or =3 microM (n=2). The rank order of potency for the endogenous tachykinins NKB>NKA>substance P (n=3) confirmed the response was mediated by the NK3 receptor. Moreover, the actual potencies obtained were consistent with affinities measured in radioligand binding studies. 3. The novel compounds PD156319-121 (0.3-1 microM), PD161182 (10-300 nM), PD168001 (10-100 nM) and PD168073 (10-100 nM) all acted as surmountable antagonists of the senktide-induced acidification response, with pA2 values of 7.49, 8.67, 9.17 and 9.25 respectively (n=3-5). In comparison the known NK3 antagonist SR142801 (10-100 nM) had a pA2 value of 8.83 (n=8) for the interaction with senktide. Again, these values are consistent with the radioligand binding data. 4. Amiloride (1 mM) inhibited the senktide-induced acidification response by 68.3+/-3.3 (n=4), indicating that the Na+/H+ antiporter plays an important role in this response, and this is consistent with the importance of this antiporter in other acidification responses. 5. Inhibition of protein kinase C with staurosporine (0.1 microM), or depletion of the intracellular Ca2+ stores with thapsigargin (1 microM), both resulted in a reduction in the maximum response to senktide (63.3+/-1.7 and 68.9+/-3.2% respectively, n=3-5), and co-application of these inhibitors abolished the response (n=3). This strongly suggested that the NK3 receptor was coupling via phospholipase C (PLC), as would be expected, although this could not be confirmed by the use of the putative PLC/PLA2 inhibitor U73122. 6. In conclusion, we have demonstrated the utility of the Cytosensor in the characterization of functional responses to agonists, and assessment of the affinities of antagonists in CHO cells expressing the human NK3, and have shown that our series of novel compounds are non-peptide NK3 antagonists of high affinity, as exemplified by PD168073.

108 Antiproliferative activity and mode of action of novel compounds of marine origin

LoVo and mdr-l overexpressing LoVo/DX cells were exposed for 1 or 24 h to 14 compounds with novel structures (mycaperoxide B, Kahalide, isobengazole, crambescidin, thiocoraline, isohomoalichondrin B, epidioximanadic acid A, sesbanimida, lamellarin, MB-2, LL-15, Palauamine, compound 21 and dehydrodidemnin). The cytotoxic potency ranged from <1 pM to >1μM. Most drugs were less active against LoVo/DX than against LoVo cells with few exceptions (e.g. isohomoalichondrin B). Flow cytometry studies showed that some compounds caused an accumulation of cells in G₂M phases. Detailed studies on the mode of action of these drugs are in progress. Preliminary data indicate that thiocoraline inhibit the decatenation reactions catalyzed by DNA-topoisomerase II, suggesting that a novel topoisomerase II inhibitor has been identified.

Characterization and catalytic activity of novel compounds containing metal ions incorporated into a layered vanadyl phosphate

The addition of metal ions such as Zn2+, Ni2+ and Pd2+ during the preparation of the layered vanadyl hydrogen phosphate VOHPO4·0.5H2O in aqueous medium, leads to the formation of a new phase containing mixed-valent vanadium. In contrast, when the same metal ions are added during the preparation of the vanadyl hydrogen phosphate in organic medium, the structure of the parent compound is retained and the metal ions appear to be present in the lattice. The metal ions incorporated into the vanadyl hydrogen phosphate prepared in different media have been found to be catalytically active, with the activity depending upon the mode of incorporation of the metal ion.

Preclinical phase II studies in human tumor xenografts: A European multicenter follow-up study

The EORTC New Drug Development Office has initiated a multicenter collaborative program to evaluate the use of human tumor xenografts to predict phase II clinical activity. A first study confirmed the efficacy of doxorubicin and inactivity of amsacrine against human tumor xenografts (Boven et al., Cancer Res: 52, 5940, 1992). In the follow-up study reported here, the activities of cisplatin, AZQ (diaziquone), pazelliptine and retelliptine have been evaluated against a panel of 40 established tumor lines grown subcutaneously in nude mice. The xenografts used represent carcinomas of the breast, colon, head+neck, ovary, small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC) and melanoma. Drugs were administered intravenously on days 0 and 7. Doses were for cisplatin 5 mg/kg, AZQ 3-7 mg/kg, pazelliptine 20-80 mg/kg and retelliptine 6-12.5 mg/kg and were selected to give a median loss of about 10%-15% body weight. When activity was defined as a specific growth delay > 1 and a tumor growth inhibition > 50%, then cisplatin demonstrated activity in 15 of 40 xenografts tested (3 of 5 breast, 1 of 6 colon, 0 of 5 head+neck, 2 of 6 NSCLC, 4 of 7 SCLC, 1 of 5 melanoma and 4 of 6 ovarian cancers); AZQ was active in 23 of 38 xenografts (2 of 3 breast, 2 of 7 colon, 4 of 5 head+neck, 3 of 6 NSCLC, 6 of 6 SCLC, 2 of 5 melanoma, 4 of 6 ovarian cancers); pazelliptine was active in 2 of 38 xenografts (1 of 5 breast cancers, 1 of 5 melanoma) while retelliptine was active in 1 of 39 xenografts (a breast cancer xenograft) tested. These results are reasonably consistent with the clinical activity of cisplatin, but overpredict the clinical efficacy of AZQ. Since pazelliptine and retelliptine are investigational compounds, the clinical phase II studies will provide a prospective test for this model. The results of the present study and the previous one indicate that the human tumor xenograft model could be suitable for predicting the activity of novel compounds to be developed for treatment of cancer patients.

Specificity of piracetam's anti-amnesic activity in three models of amnesia in the mouse

The effects of piracetam on the amnesias induced by scopolamine, diazepam and electroconvulsive shock (ECS) were studied in a passive avoidance procedure in the mouse and compared with the interactions of piracetam with the major behavioral effects of these treatments, namely scopolamine-induced hyperactivity, diazepam-induced release of punished behavior (Four Plates Test) and ECS-induced convulsions. Amnesia was induced by injecting scopolamine or diazepam (1 mg/kg, IP) 30 minutes before or applying ECS immediately after the first session (S1) of the passive avoidance task. Piracetam was studied at 3 doses (512, 1024 and 2048 mg/kg) administered PO 60 minutes before S1. Retention was measured 24 hours later (S2) in the absence of any treatment. Piracetam dose-dependently attenuated the memory deficits induced by the three amnesic treatments but did not affect either scopolamine-induced hyperactivity, diazepam-induced release of punished behavior or ECS-induced convulsions. These results point to the specificity of piracetam's anti-amnesic activity and, in particular, suggest that piracetam can suppress the memory disturbances induced by diazepam without affecting diazepam's anxiolytic activity. The test battery employed would therefore seem highly suitable for evaluating the potential nootropic activity of novel compounds.

A new animal model for the prediction of antidepressant activity.

Animal models presently in use for the screening of potential antidepressant drugs yield numerous false positives and false negatives. In search of a more specific model, we have studied the effects of psychotropic compounds on the behavioural changes induced in rats by the removal of the olfactory bulbs. We have observed that subchronic treatment with antidepressants in general reverses the behavioural alterations displayed by bulbectomized rats in tests of conditioned behaviour. The present paper describes a brief test, the so-called anxiosoif test, which may be used to assess the effects of drugs on the behaviour of bulbectomized rats. Removal of the olfactory bulbs leads to increased water intake in the anxiosoif test and to an attenuation of avoidance when the drinking spout is electrified. This latter effect can be reversed by subchronic treatment with the antidepressant drugs amitriptyline and mianserine (Org GB 94). It is suggested that the behavior of bulbectomized rats may be used as a specific tool in the prediction of antidepressant activity of novel compounds.