Inhibition of HIV-1 replication in cultured cells with phosphorylated dideoxyuridine derivatives encapsulated in immunoliposomes.

Among the 2',3'-dideoxynucleoside 5'-triphosphates containing a physiological base, 2',3'-dideoxyuridine 5'-triphosphate (ddUTP) has been reported to be among the most powerful inhibitors of human immunodeficiency virus (HIV) reverse transcriptase (RT) in cell-free systems. However, in contrast to other dideoxynucleosides, 2',3'-dideoxyuridine (ddU) is inactive in treatment of HIV-infected cells in culture, since it is a poor substrate for cellular nucleoside kinases. This problem cannot be overcome by the use of phosphorylated ddU because such compounds are unable to cross cell membranes. To promote entry and thus bypass the limiting steps of intracellular phosphorylation, we have encapsulated mono- and tri-phosphorylated ddU in liposomes coupled to monoclonal antibodies (immunoliposomes). We investigated antiviral effects in two human T cell lines (MT-4, CEM). We observed that ddU nucleotides remain phosphorylated for several weeks after encapsulation in immunoliposomes, and potent antiviral activity is obtained when these drugs are delivered into infected cells by cell-specific antibodies (ED50 < or = 1 microM on CEM). In contrast, no inhibition was observed with non-targeted liposomes containing phosphorylated ddU, or with empty liposomes, whether targeted or not.

Trace determination of ethyl methanesulfonate in Viracept 250 mg tablets by gas chromatography-mass spectrometry.

Ethyl methanesulfonate (EMS) is a potential human mutagenic and carcinogenic compound which has been found by Roche laboratories in nelfinavir mesylate, the active pharmaceutical ingredient of Viracept. In order to verify the quality of the medicinal product, a gas chromatographic method using mass spectrometry detection was developed for the trace analysis of EMS in Viracept 250 mg tablets from Roche laboratories. Combined with suitable sample preparation including a liquid/liquid extraction this method allows the EMS quantification with a reporting limit of 5 ppm. The extract is injected on a gas chromatographic system with a CP624-CB capillary column. Selected Ion Monitoring mode was used for the EMS quantification. Some validation elements of the method are reported. The validation study was performed over a range from 5 ppm to 100 ppm.

DNA-nitrosourea interactions. High-performance liquid chromatography of cross-linked dinucleosides and substituted deoxynucleosides.

A reconstituted mixture of five cross-linked dinucleosides possibly involved in DNA-nitrosourea interactions, and of their degradation products (nucleobases, deoxynucleosides and mono- or disubstituted deoxynucleosides), was analysed by reversed-phase high-performance liquid chromatography using C18 columns and an diode-array detector. The chromatographic conditions for separating the twenty-one investigated compounds were optimized, and the compounds were identified by both their retention times and their UV spectra. A structure-retention time relationship was observed under suitable conditions and is discussed. Its validity was confirmed by the prediction of the retention time of a new cross-linked dinucleoside synthesized for this purpose.