RAPID FUNCTIONALIZATION AND LOADING OF SOLID SUPPORTS

Metabolism, pharmacokinetics, tissue distribution, and stability studies of the prodrug analog of an anti-hepatitis B virus dinucleoside phosphorothioate

The alkoxycarbonyloxy dinucleotide prodrug R(p), S(p)-2 is an orally bioavailable anti-hepatitis B virus agent. The compound is efficiently metabolized to the active dinucleoside phosphorothioate R(p), S(p)-1 by human liver microsomes and S9 fraction without cytochrome P450-mediated oxidation or conjugation. The conversion of R(p), S(p)-2 to R(p), S(p)-1 appears to be mediated by liver esterases, occurs in a stereospecific manner, and is consistent with our earlier reported studies of serum-mediated hydrolytic conversion of R(p), S(p)-2 to R(p), S(p)-1. However, further metabolism of R(p), S(p)-1 does not occur. The presence of a minor metabolite, the desulfurized product 10 was noted. The prodrug R(p), S(p)-2 was quite stable in simulated gastric fluid, whereas the active R(p), S(p)-1 had a half-life of <15 min. In simulated intestinal fluid, the prodrug 2 was fully converted to 1 in approximately 3 h, whereas 1 remained stable. To ascertain the tissue distribution of the prodrug 2 in rats, the synthesis of (35)S-labeled R(p), S(p)-2 was undertaken. Tissue distribution studies of orally and intravenously administered radiolabeled [(35)S]2 demonstrated that the radioactivity concentrates in the liver, with the highest liver/plasma ratio in the intravenous group at 1 h being 3.89 (females) and in the oral group at 1 h being 2.86 (males). The preferential distribution of the dinucleotide 1 and its prodrug 2 into liver may be attributed to the presence of nucleoside phosphorothioate backbone because phosphorothioate oligonucleotides also reveal a similar tissue distribution profile upon intravenous administration.

Orally bioavailable anti-HBV dinucleotide acyloxyalkyl prodrugs

The acyloxyalkyl derivatives of a model anti-HBV dinucleotide were synthesized and evaluated as orally bioavailable prodrugs. Our studies have led to the identification of the first orally bioavailable dinucleotide prodrugs for further therapeutic development against the hepatitis B virus (HBV).

Anti-HBV nucleotide prodrug analogs: synthesis, bioreversibility, and cytotoxicity studies

Several pronucleotide analogs of the model anti-HBV dinucleotide 3'-dA-U(2'OMe) have been synthesized and evaluated for stability, bioreversibility and cytotoxicity. These studies have helped identify potential candidates for further evaluation.

Microwave-assisted functionalization of solid supports for rapid loading of nucleosides

Ultra-fast and efficient functionalization of solid supports such as controlled-pore glass (CPG), amino methyl polystyrene, and Tentagel has been achieved using microwave-assisted procedures. Both amino- and carboxy-terminated supports are easily prepared within minutes, in a reproducible manner, using microwave-assisted methodologies. The resulting functionalized supports are efficiently coupled to nucleosides using dimethylformamide as a solvent in conjunction with a specially designed reactor and workstation called LOTUS. Using these improved protocols, CPG with loadings of 75 to 85 micromol/g can be prepared on a large scale within 3 to 4 days starting from native CPG, as opposed to traditional methods that require 10 to 15 days to achieve the same objective. In addition, the methods described here can potentially be employed for rapid functionalization of other solid matrices such as beads, slides, and pins for applications in microarrays or combinatorial chemistry.