New antiretroviral agents in the clinic

Since the first controlled clinical trial of zidovudine (ACT) was terminated in the fall of 1986, much has been learned concerning the use of this agent in the treatment of human immunodeficiency virus (HIV) infection. The recent report of HIV resistance associated with long-term AZT therapy has accelerated the sense of urgency about the development of additional agents for use--either alone or in combination with AZT--against this infection. Several new agents are in various stages of preclinical or clinical evaluation. Some, such as dideoxycytidine, dideoxyinosine, dideoxydidehydrothymidine, azidouridine, and foscarnet, inhibit viral DNA synthesis through inhibition of reverse transcriptase. Other potentially useful agents presumably act at different stages of infection. Soluble CD4, for example, is a soluble form of the receptor to which HIV must bind to infect cells, and castanospermine represents a new class of compounds that block the maturation process of the viral glycoprotein. An apparently more potent and less toxic analogue of the latter agent, N-butyl-deoxynojirimycin, is currently in phase I testing.