The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with time-resolved spectrophotometry. The initially observed absorption spectrum upon oxidation of DNA by the selenite radical is consistent with spin on cytosine (C), as the GC⢠pair neutral radical, followed by the spectra of oxidized ligands. The rate of oxidation of bound ligands increased with an increase in the ratio (r) ligands per base pair from 0.005 to 0.04. Both the rate of ligand oxidation and the estimated range of hole transfer (up to 30 DNA base pairs) decrease with the decrease in one-electron reduction potential between the GC⢠pair neutral radical of ca. 1.54 V and that of the ligand radicals (E0', 0.90-0.99 V). Linear plots of log of the rate of hole transfer versus r give a common intercept at r = 0 and a free energy change of 12.2 ± 0.3 kcal mol-1, ascribed to the GC⢠pair neutral radical undergoing a structural change, which is in competition to the observed hole transfer along DNA. The rate of hole transfer to the ligands at distance, R, from the GC⢠pair radical, k2, is described by the relationship k2 = k0 exp(constant/R), where k0 includes the rate constant for surmounting a small barrier.
Base Pairing , DNA , DNA/chemistry , Free Radicals/chemistry , Oxidation-Reduction , Benzimidazoles/chemistry , Animals , Cattle , Ligands , Bisbenzimidazole/chemistry , DNA Repair , DNA Damage , Cytosine/chemistry
Purpose DNA ligands labelled with 125I induce cytotoxic DNA double-strand breaks (DSB), suggesting a potential for Auger endoradiotherapy. Since the 60-day half-life of 125I is suboptimal for therapy, we have investigated another Auger-emitter 124I, with shorter half-life (4.18 days), and the additional feature of positron-emission, enabling positron emission tomography (PET) imaging. The purpose of this study was to compare the two radionuclides on the basis of DNA DSB per decay. Materials and methods Using a 124I- (or 125I)-labelled minor groove binding DNA ligand, we investigated DNA breakage using the plasmid DNA assay. Biodistribution of the conjugate of the labelled ligand with transferrin was investigated in nude mice bearing a K562 human lymphoma xenograft. Results The probability of DSB per decay was 0.58 and 0.85 for 124I and 125I, respectively, confirming the therapeutic potential of the former. The crystal structure of the ligand DNA complex shows the iodine atom deep within the minor groove, consistent with the high efficiency of induced damage. Biodistribution studies, including PET imaging, showed distinctive results for the conjugate, compared to the free ligand and transferrin, consistent with receptor-mediated delivery of the ligand. Conclusions Conjugation of 124I-labelled DNA ligands to tumor targeting peptides provides a feasible strategy for Auger endoradiotherapy, with the advantage of monitoring tumor targeting by PET imaging.
DNA/pharmacokinetics , Electrons/therapeutic use , Iodine Radioisotopes/therapeutic use , Neoplasms, Experimental/diagnostic imaging , Neoplasms, Experimental/radiotherapy , Radiotherapy, Image-Guided/methods , Animals , DNA/chemistry , Humans , Iodine Radioisotopes/pharmacokinetics , Isotope Labeling , K562 Cells , Mice , Mice, Inbred BALB C , Mice, Nude , Neoplasms, Experimental/metabolism , Radiopharmaceuticals/pharmacokinetics , Radiopharmaceuticals/therapeutic use , Radiotherapy/methods , Radiotherapy Dosage , Tissue Distribution , Treatment Outcome
The discovery and optimisation of a new class of benzothiazole small molecules that inhibit bacterial DNA gyrase and topoisomerase IV are described. Antibacterial properties have been demonstrated by activity against DNA gyrase ATPase and potent activity against Staphylococcus aureus, Enterococcus faecalis, Streptococcus pyogenes and Haemophilus influenzae. Further refinements to the scaffold designed to enhance drug-likeness included analogues bearing an α-substituent to the carboxylic acid group, resulting in excellent solubility and favourable pharmacokinetic properties.
Benzothiazoles/chemistry , Benzothiazoles/pharmacology , DNA Topoisomerase IV/antagonists & inhibitors , Drug Design , Isonipecotic Acids/chemistry , Topoisomerase II Inhibitors/chemical synthesis , Topoisomerase II Inhibitors/pharmacology , Animals , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacokinetics , Anti-Bacterial Agents/pharmacology , Benzothiazoles/chemical synthesis , DNA Gyrase/chemistry , DNA Gyrase/metabolism , DNA Topoisomerase IV/metabolism , Enterococcus faecalis/drug effects , Enterococcus faecalis/enzymology , Enzyme Activation/drug effects , Haemophilus influenzae/drug effects , Haemophilus influenzae/enzymology , Half-Life , Mice , Microbial Sensitivity Tests , Rats , Staphylococcus aureus/drug effects , Staphylococcus aureus/enzymology , Streptococcus pyogenes/drug effects , Streptococcus pyogenes/enzymology , Topoisomerase II Inhibitors/chemistry , Topoisomerase II Inhibitors/pharmacokinetics
A series of phenylaminopyrimidines has been identified as inhibitors of Janus kinases (JAKs). Development of this initial series led to the potent JAK2/JAK1 inhibitor CYT387 (N-(cyanomethyl)-4-[2-[[4-(4-morpholinyl)phenyl]amino]-4-pyrimidinyl]-benzamide). Details of synthesis and SAR studies of these compounds are reported.
Benzamides/chemistry , Janus Kinase 2/antagonists & inhibitors , Protein Kinase Inhibitors/chemistry , Pyrimidines/chemistry , Animals , Benzamides/chemical synthesis , Benzamides/pharmacology , Binding Sites , Caco-2 Cells , Cell Line, Tumor , Computer Simulation , Humans , Janus Kinase 2/metabolism , Male , Protein Isoforms/antagonists & inhibitors , Protein Isoforms/metabolism , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/pharmacokinetics , Pyrimidines/chemical synthesis , Pyrimidines/pharmacokinetics , Pyrimidines/pharmacology , Rats , Rats, Sprague-Dawley , Structure-Activity Relationship
The crystal structure of N-methyl-4-piperidyl 2,4-dinitrobenzoate, C(13)H(15)N(3)O(6), (I), at 130 (2) K reveals that, in the solid state, the molecule exists in the equatorial conformation, (Ieq). Thus, the through-bond interaction present in the axial conformation, (Iax), is not strong enough to overcome the syn-diaxial interactions between the axial methyl substituent and the axial H atoms on the two piperidyl ring C atoms either side of the ester-linked ring C atom. The carboxylate group in (I) is orthogonal to the aromatic ring, in contrast with other 2,4-dinitrobenzoates, which are coplanar. The piperidyl-ester C-O bond distance is 1.467 (3) A, which is actually shorter than other equatorial cyclohexyl-ester C-O distances. This shorter piperidyl-ester C-O bond distance is due to the reduced electron demand of the orthogonal ester group.
