KINETIC INTERACTION OF THE DIPHOSPHATES OF 9-(2-PHOSPHONYLMETHOXYETHYL)ADENINE AND OTHER ANTI-HIV ACTIVE PURINE CONGENERS WITH HIV REVERSE-TRANSCRIPTASE AND HUMAN DNA POLYMERASE-ALPHA, POLYMERASE-BETA AND POLYMERASE-GAMMA

The inhibitory effects of the diphosphates of 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and its analogues on HIV reverse transcriptase and human DNA polymerases alpha, beta, and gamma have been studied. The analogues investigated are the diphosphates of 9-(2-phosphonylmethoxypropyl)adenine (PMPApp), 9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine (PMPDAPpp), and (2R,5R)-9-[2,5-dihydro-5-(phosphonyl methoxy)-2-furanyl]adenine (D4APpp). These four compounds are much more inhibitory to HIV reverse transcriptase when an RNA template rather than a DNA template is used. The K-i values for the four compounds range from 11 to 22 nM with an RNA template. The K-i values for ddCTP and AZTTP are 54 nM and 8 nM, respectively. PMEApp and its analogues show varying degrees of inhibition of the human DNA polymerases, The K-i values for pMEApp, PMPApp and PMPDAPpp against DNA polymerase alpha are in the micromolar range, while D4APpp is a poor inhibitor of this enzyme with a K-i value of 65.9 mu M. The inhibition of DNA polymerase beta by PMEApp, PMPApp and D4APpp is minimal, while PMPDAPpp shows higher inhibition of DNA polymerase beta with a K-i value of 9.71 mu M. The K-i values for PMEApp and D4APpp against DNA polymerase gamma are submicromolar while PMPApp and PMPDAPpp are much less inhibitory to this enzyme. For comparison, ddCTP was found to be a more potent inhibitor of DNA polymerases beta and gamma than the diphosphates of PMEA and its analogues.