Antiretroviral Therapy in AIDS

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Abstract
To review recent developments of antiretroviral therapy for the acquired immunodeficiency syndrome (AIDS) and related disorders. An edited and updated summary of a Clinical Staff Conference held 26 October 1988 at the National Institutes of Health. The speakers discussed their own work as well as related work from other groups. The discovery that human immunodeficiency virus (HIV) causes AIDS has permitted the development of rational antiviral therapy for this disease. Various steps in the replicative cycle of HIV can be targeted for intervention. More basic research into the life cycle of HIV is therefore likely to yield new therapeutic approaches. In 1985, nucleoside analogues called dideoxynucleosides were discovered to be potent inhibitors of HIV replication in vitro. Dideoxynucleosides selectively inhibit HIV reverse transcriptase after they are phosphorylated intracellularly to 5'-triphosphates. One dideoxynucleoside, 3'-azido-2',3'-dideoxythymidine (AZT or zidovudine) has been found to prolong the life of patients with AIDS. This drug can partially reverse HIV dementia and decrease short-term progression to AIDS; it has been approved for treating HIV-infected patients with fewer than 500 CD4+ cells/mm3. AZT is only a first step in developing new therapy for AIDS. Its use is associated with toxicities, particularly bone marrow suppression. Several groups have reported the development of AZT-resistant strains of HIV. Other dideoxynucleosides whose toxicity profiles differ from that of AZT have also shown activity against HIV in early clinical studies. Large-scale, randomized trials of these drugs are now under way. Studies have shown that the binding of HIV to CD4 may be blocked by genetically engineered forms of CD4 and that HIV protease may be inhibited by substrate analogues. Protease inhibitors are an excellent area for further study in patients. Antisense oligonucleotide therapy may target the regulatory genes of HIV and is also being considered. With these advances, AIDS is gradually changing from an imminently fatal disease to one that can be managed with the judicious use of drugs and biologics. Progress against AIDS will continue, provided that researchers adhere to the principles of controlled trials.