Tri-N-Boc-tetraazamacrocycle-nucleoside conjugates: synthesis and anti-HIV activities

5'-phosphonate derivatives of 2',3'-dideoxy-3'-thiacytidine as new anti-HIV prodrugs

Two new phosphonate 3TC prodrugs were synthesized and studied in MT-4 cells as inhibitors of HIV replication. Their pharmacokinetic parameters were evaluated following intragastric administration in rabbits and oral administration in dogs. Both compounds were much less toxic than parent 3TC in cell cultures and could generate the active nucleoside in laboratory animals.

Prodrug and antedrug: two diametrical approaches in designing safer drugs

The prodrug and antedrug concepts, which were developed to overcome the physical and pharmacological shortcomings of various therapeutic classes of agents, employ diametrically different metabolic transformations. The prodrug undergoes a predictable metabolic activation prior to exhibiting its pharmacological effects in a target tissue while the antedrug undergoes metabolic deactivation in the systemic circulation upon leaving a target tissue. An increased therapeutic index is the aspiration for both approaches in designing as well as evaluation criteria. The recent research endeavors of prodrugs include the gene-directed and antibody-directed enzymatic activation of a molecule in a targeted tissue, organ specific delivery, improved bioavailabilities of nucleosides and cellular penetration of nucleotides. As for antedrugs, emphasis in research has been based upon the design and synthesis of systemically inactive molecule by incorporating a metabolically labile functional group into an active molecule.

New bicyclam-AZT conjugates: design, synthesis, anti-HIV evaluation, and their interaction with CXCR-4 coreceptor

We report the synthesis of mono- and bis-tetraazamacrocycle-AZT conjugates. All new compounds were screened for their ability to inhibit HIV-1 replication in MT4 cell line and were compared to AZT alone. It appears that N-protected covalent prodrugs are equipotent to AZT as inhibitor of HIV replication, while N-deprotected analogues exhibit both higher activity and selectivity against HIV-infected cells. The most active antiviral compounds 27, 28, 34, and 35 were then tested for their binding capability to CXCR-4 receptor. N-Boc analogues 27 and 34 were only weakly effective; in contrast, N-deprotected conjugates 28 and 35 were antagonists to 12G5 mAb binding until 0.05 and 5 microg/mL, respectively. The stability of compound 28 in human plasma was evaluated, and half-life was found to be approximately 8 h in the described conditions. All these results seem to demonstrate the confidence of our prodrug approach, with analogue 28 emerging as the best candidate as lead compound in HIV-1 polytherapy perspective.