Orally bioavailable prodrugs of a BCS class 2 molecule, an inhibitor of HIV-1 reverse transcriptase.

The N-2 position of pyridazinone 1, a potent HIV-1 NNRTI that has limited aqueous solubility, was derivatized into a series of hydroxymethyl esters and carbonates as well as one phosphate. The derivatives served as prodrugs to effectively deliver 1 to rat plasma upon oral treatment at 50 mpk. Increases of 4.3- to 8.6-fold in 24-hour exposure of 1 (over that of parent) were observed while the prodrugs and the hydroxymethyl adduct 2 were undetectable.

Discovery and optimization of pyridazinone non-nucleoside inhibitors of HIV-1 reverse transcriptase.

A series of benzyl pyridazinones were evaluated as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs). Several members of this series showed good activity against the wild-type virus and NNRTI-resistant viruses. The binding of inhibitor 5a to HIV-RT was analyzed by surface plasmon resonance spectroscopy. Pharmacokinetic studies of 5a in rat and dog demonstrated that this compound has good oral bioavailability in animal species. The crystal structure of a complex between HIV-RT and inhibitor 4c is also described.

Discovery of triazolinone non-nucleoside inhibitors of HIV reverse transcriptase.

Novel non-nucleoside inhibitors of HIV-RT that contain pyridazinone isosteres were prepared, and a series of triazolinones were found to be potent inhibitors of HIV replication. These compounds were active against several NNRTI-resistant virus strains. Pharmacokinetic studies indicated that inhibitor 7e has good bioavailability in rats. Several fragments of inhibitor 7c were prepared, and the binding of these compounds to HIV-RT was analyzed by surface plasmon resonance spectroscopy.

Toward a new genetic system with expanded dimensions: size-expanded analogues of deoxyadenosine and thymidine.

We describe the design, preparation, and properties of two key building blocks of a size-expanded genetic system. Nucleoside analogues of the natural nucleosides dA and dT are reported in which the fusion of a benzo ring increases their size by ca. 2.4 A. The expanded dA analogue (dxA), having a tricyclic base, was first reported by Leonard nearly three decades ago. We describe a shortened and more efficient approach to this compound. The expanded dT analogue (dxT), a methylquinazolinedione C-glycoside, was previously unknown; we describe its preparation in eight steps from 5-methylanthranilic acid. The key glycoside bond formation employed Pd-mediated coupling of an aryl iodide precursor with a dihydrofuran derivative of deoxyribose. Both nucleosides are shown to be efficient fluorophores, emitting light in the blue-violet range. The base-protected phosphoramidite derivatives were prepared, and short oligonucleotides containing them were characterized. The two size-expanded nucleosides are key components of a new four-base genetic system designed to form helical paired structures having a diameter greater than that of natural DNA. Elements of the design of this expanded genetic molecule, termed xDNA, are discussed, including the possibility of up to eight base pairs of information storage capability.

A four-base paired genetic helix with expanded size.

We describe a new molecular class of genetic-pairing system that has a native DNA backbone but has all four base pairs replaced by new, larger pairs. The base pairs include size-expanded analogs of thymine and of adenine, both extended by the width of a benzene ring (2.4 A). The expanded-diameter double helices are more thermodynamically stable than the Watson-Crick helix, likely because of enhanced base stacking. Structural data confirm a right-handed, double-stranded, and base-paired helical form. Because of the larger base size, all the pairs of this helical system are fluorescent, which suggests practical applications in detection of natural DNA and RNA. Our findings establish that there is no apparent structural or thermodynamic prohibition against genetic systems having sizes different from the natural one.