A synthetic nucleoside analogue of deoxyadenosine and a prodrug of didanosine in which the 3' hydroxyl group on the ribose moiety is replaced by a hydrogen atom. 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.