One of the principal projects of the Retroviral Diseases Section is the pre-clinical and early clinical development of antiretroviral therapy for the treatment of HIV infection. Since 1984, members of the section have been involved in the development of anti-viral therapy for AIDS and related disorders (until 1991, this section, as well as the Experimental Retrovirology Section were the Laboratory of the Associate Director under the directorship of Dr. Samuel Broder). Members of the section played pivotal roles in the development of azidothymidine (AZT, zidovudine), 2',3'-dideoxycytidine (ddC, zalcytabine), and 2',3'-dideoxyinosine (ddI, didanosine) as anti-HIV drugs for AIDS and in particular conducted the initial clinical trials of these agents as well as associated pre-clinical and associated laboratory work. In addition, members of the section have been involved in the study of suramin, soluble recombinant CD4 (rCD4), CD4-IgG immunoadhesin (rCD4-IgG), 2',3'-dideoxyadenosine (ddA), and pentosan polysulfate as potential AIDS therapies. The section is presently studying the negative enantiomer of 3'-thia-cytadine (3TC) as a potential anti-HIV agent in collaboration with Glaxo, Inc. and is planning studies of other agents, including an inhibitor of HIV protease. As will be discussed in a separate project, the section is also involved in the study of combination therapy of HIV infection. Finally, the section is involved in a study of the relationship between CD4 counts, the development of opportunistic infections and tumors, and mortality in patients on anti-retroviral therapy.