Two mechanisms dominate the clinical pipeline for oligonucleotide-based gene silencing, namely, the antisense approach that recruits RNase H to cleave target RNA and the RNAi approach that recruits the RISC complex to cleave target RNA. Multiple chemical designs can be used to elicit each pathway. We compare the silencing of the asthma susceptibility gene ADAM33 in MRC-5 lung fibroblasts using four classes of gene silencing agents, two that use each mechanism: traditional duplex small interfering RNAs (siRNAs), single-stranded small interfering RNAs (ss-siRNAs), locked nucleic acid (LNA) gapmer antisense oligonucleotides (ASOs), and novel hexadecyloxypropyl conjugates of the ASOs. Of these designs, the gapmer ASOs emerged as lead compounds for silencing ADAM33 expression: several gapmer ASOs showed subnanomolar potency when transfected with cationic lipid and low micromolar potency with no toxicity when delivered gymnotically. The preferential susceptibility of ADAM33 mRNA to silencing by RNase H may be related to the high degree of nuclear retention observed for this mRNA. Dynamic light scattering data showed that the hexadecyloxypropyl ASO conjugates self-assemble into clusters. These conjugates showed reduced potency relative to unconjugated ASOs unless the lipophilic tail was conjugated to the ASO using a biocleavable linkage. Finally, based on the lead ASOs from (human) MRC-5 cells, we developed a series of homologous ASOs targeting mouse Adam33 with excellent activity. Our work confirms that ASO-based gene silencing of ADAM33 is a useful tool for asthma research and therapy.

Several salt forms of 4-aminopyridine and 3,4-diaminopyridine with nitric, sulfuric, and phosphoric acids, comprising anhydrates and some hydrates, have been prepared and structurally characterized, and the role of water assessed in the latter cases. Our study has confirmed that anhydrates can be obtained even when water is present in the crystallizing solution. Protonation of the aminopyridines is consistent with ΔpK a differences. 4-Aminopyridine uniquely forms a mono cation only, with protonation at the pyridine nitrogen, whilst 3,4-diaminopyridine forms both a mono cation, again with protonation at the pyridine nitrogen, and a dication, with the second protonation at the 3-amino position. Thus, 4-aminopyridine forms a 1 : 1 nitrate anhydrate, a 1 : 1 bisulphate anhydrate, a 2 : 1 sulfate hydrate and a 1 : 1 dihydrogen phosphate hydrate. 3,4-Diaminopyridine forms a 1 : 1 nitrate anhydrate and 1 : 2 nitrate anhydrate and hydrate, 2 : 1 and 1 : 1 sulfate hydrates and a 1 : 1 dihydrogen phosphate anhydrate. Analysis of the structures found suggests that the H-bonding capability of the water O-H donors and O acceptor components have similar tendencies to N-H donors and other O acceptors. At the same time, we recognise that, whilst water molecules may occasionally be structure forming, they also act as spacers or fillers in the development of the primary H-bonded assemblies. These will mainly be controlled by the stoichiometries and H-bonding possibilities of the anion/cation components. It is also possible that, in some circumstances, the inclusion or otherwise of water in structures may be competitive with supplementary weak interactions such as C-H⋯O hydrogen bonding. pyridine with other, generally pharmaceutically acceptable acids, including the inorganic acids hydrochloric, hydrobromic, nitric, sulfuric, and phosphoric, and characterized the products, and their behaviour under humid conditions. The halide salts proved to be a complex group of compounds, particularly in the formation of hydrates, and the structures adopted. We will describe these results, still undergoing analysis, in separate papers, 2,3 but report here on the particular forms obtained with the three oxyacids. In this work, we were interested in assessing, on the one hand, the interplay between the acidities and basicities of the components, yielding, where relevant, mono-and/or di-acid or base salt forms, and on the other, the formation, or not, of hydrates.