Synthesis and anti-HIV properties of new carbamate prodrugs of AZT.

A series of new 5'-O-carbamate prodrugs of AZT have been prepared. The stability in biological media, anti-HIV properties and pharmacokinetic parameters in dogs were evaluated. The compounds display moderate anti-HIV activity in cell culture. After oral administration of carbamate IV in dogs, both intact prodrug IV and released AZT were discovered in dog blood. Pharmacokinetic parameters of the compound IV were estimated. Half-life (T(1/2)) of AZT released after oral administration of IV in dogs was close to that after administration of AZT itself, and time to the maximum concentration (T(max)) of AZT released from IV was two and three times longer compared with that of AZT and H-phosphonate AZT, respectively. Acute toxicity was more than five times less if compared with AZT. As a result, we consider this series of carbamate derivatives of AZT as perspective for development of anti-HIV agents.

5'-aminocarbonyl phosphonates as new zidovudine depot forms: antiviral properties, intracellular transformations, and pharmacokinetic parameters.

The main disadvantages of 3'-azido-3'-deoxythymidine (zidovudine, AZT), the most common anti-HIV drug, are toxicity and a short half-life in the organism. The introduction of an H-phosphonate group into the AZT 5' position resulted in significant improvement of its therapeutic properties and allowed a new anti-HIV drug, Nikavir (AZT H-phosphonate). In this work, we described a new group of AZT derivatives, namely, AZT 5'-aminocarbonylphosphonates. The synthesized compounds displayed antiviral properties in cell cultures infected with HIV-1 and the capacity to release the active nucleoside in animals (rabbits and dogs) in a dose-dependent manner. The compounds were less toxic in MT-4 and HL-60 cell cultures and experimental animals compared with AZT. Major metabolites found in MT-4 cells after their incubation with AZT 5'-aminocarbonylphosphonate 1 were AZT and AZT 5'-phosphate (25 and 55%, respectively). Among the tested compounds, phosphonate 1 was the most effective AZT donor, and its longest t(1/2) and T(max) values in the line phosphonate 1--AZT H-phosphonate--AZT imply that compound 1 is an extended depot form of AZT. Although bioavailability of AZT after oral administration of phosphonate 1 was lower than those of AZT H-phosphonate and AZT (8 against 14 and 49%), we expect that this reduction would not cause essential decrease of antiviral activity but noticeably decrease toxicity as a result of gradual accumulation of AZT in blood and the absence of sharp difference between C(max) and C(min). Such a combination of properties makes the compounds of this group promising for further studies as extended-release forms of AZT.