Dideoxyadenosine (2′,3′-dideoxyadenosine) is a prodrug form of didanosine (2',3'-dideoxyinosine), a nucleoside reverse transcriptase inhibitor analog of adenosine. 2',3'-Dideoxyadenosine and 2',3'-dideoxyinosine were shown to be equally effective in the inhibition of HIV proliferation in human T cells. Dideoxyadenosine competitively inhibits adenylyl cyclase, thereby reducing levels of cyclic adenosine monophosphate (cAMP). By inhibiting cAMP-mediated gene activation in tumor cells, this agent may retard tumor cell proliferation. 2',3'-dideoxyadenosine inhibits retroviral DNA synthesis and mRNA expression in T cells exposed to the virus that causes acquired immunodeficiency syndrome, and affords such cells long-term protection in vitro under conditions of substantial viral excess. 2',3'-dideoxyadenosine appears to completely block reverse transcription from viral RNA to viral DNA. 2',3'-dideoxyadenosine was also shown not only to possess antibacterial activity in vitro against a variety of Enterobacteriaceae, but also to be effective in vivo, dideoxyadenosine was active in experimental mouse infections by the oral route against 5 Salmonella strains, 2 of 3 Arizona strains, 5 of 7 Citrobacter strains, 3 of 8 Klebsiella strains, 3 of 5 Escherichia strains, 1 of 3 Shigella strains, and 3 of 15 Serratia strains at concentrations generally well below the toxic level.