Synthesis, in Vitro Anti-Human Immunodeficiency Virus Structure—Activity Relationships and Biological Stability of 5′-O-Myristoyl Analogue Derivatives of 3′-Azido-2′,3′-Dideoxythymidine (AZT) as Potential Prodrugs

5′- O-Myristoyl analogue derivatives of 3′-azido-2′,3′-dideoxythymidine (AZT), designed as potential double-barrelled prodrugs to AZT and the myristic acid analogues, were synthesized. Their ability to protect CEM cells against human immunodeficiency virus (HIV)-induced cytopathogenicity was determined and structure–activity paradigms were developed. 3′-Azido-2′,3′-dideoxy-5′- O-(4-oxate-tradecanoyl)thymidine (EC50=1.4 nM) and 3′-azido-2′,3′-deoxy-5′- O-(12-bromododecanoyl)thymidine (EC50=3.2 nM) were the most effective anti-HIV-1 agents, relative to AZT (EC50=10 nM). These myristoyl analogue derivatives were more lipophilic (calculated log P=4.5–8.1 range) than the parent compound AZT (log P=0.06), and a linear correlation between their log P and HPLC log retention timeswas observed. The ester cleavage half-lives ( t1/2) for esters upon in vitro incubation with porcine liver esterase, rat plasma or rat brain homogenate was dependent on the steric bulk, and electronegative inductive effect of the α-substituent (H, Br, F), of the 5′- O-myristoyl analogue moiety. 3′-Azido-2′,3′-dideoxy-5′- O-(11-(4-iodophenoxy) undecanoyl)-thymidine exhibited t1/2 values of 80.4, 3.7 and 150.0 min upon incubation with porcine liver esterase, rat plasma and rat brain homogenate, respectively.

Concepts for the design of anti-HIV nucleoside prodrugs for treating cephalic HIV infection

The life cycle of HIV involves nine sequential stages. Of these, the reverse transcription (RT) process is a prime target for drug therapy, using both nucleoside and non-nucleoside inhibitors of RT. There are currently five marketed 2',3'-dideoxynucleoside RT inhibitors, but there is need for drugs with improved therapeutic efficacy, decreased development of resistance and broader spectrum to treat resistant strains.One approach to improve RT inhibitors is through chemical derivatization using metabolically-cleavable linkages that permit timely regeneration of the active nucleoside inside the body at the site of infection (prodrug formation). Four classes of prodrugs are now reviewed: 2',3'-dideoxynucleoside masked phosphates, 5'-O-carboxylic acid esters of 2',3'-dideoxynucleosides, 2',3'-dideoxycytidine N(4)-[(dialkylamino)methylene] prodrugs and 5-halo-6-alkoxy(azido or hydroxy)-5,6-dihydro 2',3'-dideoxynucleosides. Mutually-masking dual action (MMDA) prodrugs that release a nucleoside RT inhibitor and an abnormal N-myristoyl transferase substrate are presented as a special class of anti-HIV prodrugs that have the potential to interact with the life cycle of the virus at two distinct stages.

Synthesis, in vitro anti-HIV activity, and biological stability of 5'-O-myristoyl analogue derivatives of 3'-fluoro-2',3'-dideoxythymidine (FLT) as potential bifunctional prodrugs of FLT

A group of 5'-O-myristoyl analogue derivatives of FLT (2) were evaluated as potential anti-HIV agents that were designed to serve as prodrugs to FLT. 3'-Fluoro-2',3'-dideoxy-5'-O-(12-methoxydodecanoyl)thymidine (4) (EC50 = 3.8 nM) and 3'-fluoro-2',3'-dideoxy-5'-O-(12-azidododecanoyl)thymidine (8) (EC50 = 2.8 nM) were the most effective anti-HIV-1 agents. There was a linear correlation between Log P and HPLC Log retention time for the 5'-O-FLT esters. The in vitro enzymatic hydrolysis half-life (t1/2), among the group of esters (3-8) in porcine liver esterase, rat plasma and rat brain homogenate was longer for 3'-fluoro-2',3'-dideoxy-5'-O-(myristoyl)thymidine (7), with t1/2 values of 20.3, 4.6 and 17.5 min, respectively.