No abstract

No abstract

Database searching and compound screening identified 1-benzyl-3-(3-dimethylaminopropyloxy)indazole (benzydamine, 3) as a potent activator of the nitric oxide receptor, soluble guanylate cyclase. A comprehensive structure-activity relationship study surrounding 3 clearly showed that the indazole C-3 dimethylaminopropyloxy substituent was critical for enzyme activity. However replacement of the indazole ring of 3 by appropriately substituted pyrazoles maintained enzyme activity. Compounds were evaluated for inhibition of platelet aggregation and showed a general lipophilicity requirement. Aryl-substituted pyrazoles 32, 34, and 43 demonstrated potent activation of soluble guanylate cyclase and potent inhibition of platelet aggregation. Pharmacokinetic studies in rats showed that compound 32 exhibits modest oral bioavailability (12%). Furthermore 32 has an excellent selectivity profile notably showing no significant inhibition of phosphodiesterases or nitric oxide synthases.

Respiratory syncytial virus (RSV) is the cause of one-fifth of all lower respiratory tract infections worldwide and is increasingly being recognized as representing a serious threat to patient groups with poorly functioning or immature immune systems. Racemic 1,4-benzodiazepines show potent anti-RSV activity in vitro. Anti-RSV evaluation of 3-position R- and S-benzodiazepine enantiomers and subsequent optimization of this series resulted in selection of a clinical candidate. Antiviral activity was found to reside mainly in the S-enantiomer, and the R-enantiomers were consistently less active against RSV. Analogues of 1,4-(S)-benzodiazepine were synthesized as part of the lead optimization program at Arrow and tested in the XTT assay. From this exercise, (S)-1-(2-fluorophenyl)-3-(2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]-diazepin-3-yl)-urea, 17b (RSV-604) was identified as a clinical candidate, exhibiting potent anti-RSV activity in the XTT assay, which was confirmed in secondary assays. Compound 17b also possessed a good pharmacokinetic profile and has now progressed into the clinic.

Summary The potent kinase inhibitor staurosporine and its protein kinase C (PKC)-selective analogue CGP 41251 are known to sensitise cells with the multidrug resistance (MDR) phenotype mediated by Pglycoprotein (P-gp) to cytotoxic agents. Here four PKC-selective staurosporine cogeners, CGP 41251, UCN-01, RO 31 8220 and GF 109203X, were compared with staurosporine in terms of their MDR-reversing properties and their susceptibility towards P-gp-mediated drug efflux from MCF-7/Adr cells. Staurosporine was the most potent and the bisindolylmaleimides RO 31 8220 and GF 109203X the least potent cytostatic agents. When compared with MCF-7 wild-type cells, MCF-7/Adr cells were resistant towards the growth-arresting properties of RO 31 8220 and UCN-01, with resistance ratios of 12.6 and 7.0 respectively. This resistance could be substantially reduced by inclusion of the P-gp inhibitor reserpine. The ratios for GF 109203X, staurosporine and CGP 41251 were 1.2, 2.0 and 2.9 respectively, and they were hardly affected by reserpine. These results suggest that RO 31 8220 and UCN-01 are avidly transported by P-gp but that the other compounds are not. Staurosporine and CGP 41251 at 10 and 20 nm, respectively, decreased efflux of the P-gp probe rhodamine 123 (R123) from MCF-7/Adr cells, whereas RO 31 8220 and GF 109203X at 640 nm were inactive. CGP 41251 was the most effective and GF 109203X the least effective inhibitor of equilibrium binding of [3H]vinblastine to its specific binding sites, probably P-gp, in MCF-7/Adr cells. Overall, the results imply that for this class of compound the structural properties that determine susceptibility towards P-gp-mediated substrate transport are complex. Comparison with ability to inhibit PKC suggests that the kinase inhibitors affect P-gp directly and not via inhibition of PKC. Among these compounds CGP 41251 was a very potent MDR-reversing agent with high affinity for P-gp and least affected by P-gp-mediated resistance, rendering it an attractive drug candidate for clinical development.

Summary The MCF-7 doxorubicin-resistant cell line MCF-7/Dox has been used extensively for studies of the multidrug resistance phenomenon. Using fluorescence-activated cell sorting (FACS), these cells were separated into two populations on the basis of rhodamine 123 (R123) accumulation. We designated these as low Pglycoprotein (LP-gp) and high P-gp (HP-gp)

The hypothesis was tested that 9 kinase inhibitors with diverse specificities for protein kinase C (PKC), including staurosporine and four of its analogues, interfere differently with PKC derived from either the cytosolic or particulate fractions of MCF-7 breast carcinoma cells. GF 109203X inhibited the enzyme identically in either preparation. CGP 41251 and calphostin C inhibited cytosolic PKC more effectively than membrane-derived PKC with ratios of ICso (cytosolic PKC) over IC50 (membrane-derived PKC) of 0.07 and 0.04, respectively. The other six agents inhibited membrane-derived PKC more potently than cytosolic enzyme. Staurosporine and RO 31 8220 exhibited IC50 ratios of 12.3 and 21.6, respectively. The results suggest that there are dramatic differences between kinase inhibitors in their divergent effects on cytosolic and membrane-derived PKC which should be borne in mind in the interpretation of their pharmacological properties.but possess much better selectivity for PKC [7][8][9][10]. Two such PKC-specific analogues, UCN-01 and CGP 41251, have been shown to possess antineoplastic activity in human tumour models grown in rodents [9,11]. In most investigations of the ability of compounds to inhibit PKC, cytosolic enzyme preparations have been used. In the light of the fact that it is predominantly PKC in the membrane which is of functional importance, we tested the hypothesis that kinase inhibitors display different potencies against membrane-derived as compared to cytosolic enzyme. To that end nine well-characterised PKC inhibitors, including staurosporine and four analogues, were investigated with respect to their ability to inhibit PKC prepared from the cytosol or membrane of human-derived MCF-7 breast cancer cells. The susceptibility of these cells towards the growth-arresting ability of PKC inhibitors has recently been described [12].

No abstract