Category: Science & Technology Key figures: Jerome Horwitz (original synthesizer, Wayne State University), Samuel Broder, Hiroaki Mitsuya, Robert Yarchoan (NCI researchers), Janet Rideout (Burroughs Wellcome chemist), David Barry (Burroughs Wellcome research director)
Zidovudine — sold under the brand name Retrovir and known by its earlier name azidothymidine (AZT) — became the first drug approved by the U.S. Food and Drug Administration for the treatment of HIV/AIDS when the agency granted approval on March 20, 1987. Its path from laboratory bench to pharmacy involved two separate scientific generations working more than two decades apart.
Jerome Horwitz, a chemist at Wayne State University’s Barbara Ann Karmanos Cancer Institute, first synthesized the compound in 1964 under a National Cancer Institute grant. Horwitz designed it as a potential cancer treatment on the theory that a modified nucleoside might disrupt DNA replication in rapidly dividing tumour cells. The compound failed in animal tests — it did not slow cancer growth — and Horwitz set it aside, never patenting the molecule.
Two decades later, the AIDS epidemic created urgent demand for any drug that could inhibit the newly identified human immunodeficiency virus. In 1984–1985, researchers at Burroughs Wellcome — including chemist Janet Rideout and research director David Barry — screened a library of compounds against HIV. They identified AZT as a candidate and supplied it to the National Cancer Institute team led by Samuel Broder, Hiroaki Mitsuya, and Robert Yarchoan, who confirmed in February 1985 that the drug potently inhibited HIV replication in laboratory cell cultures. Phase I clinical trials followed immediately at NCI and Duke University, demonstrating tolerability and evidence of efficacy.
AZT works as a nucleoside reverse transcriptase inhibitor (NRTI). The active metabolite, zidovudine 5′-triphosphate, mimics thymidine (a natural DNA building block) and is incorporated into the growing viral DNA chain by HIV’s reverse transcriptase enzyme. Because AZT lacks the 3′-hydroxyl group needed for the next nucleotide to attach, DNA chain elongation terminates — blocking viral replication without directly attacking the virus. The drug does not cure HIV infection but substantially slows the destruction of CD4+ T-cells and delays the onset of AIDS-defining illnesses.
A pivotal double-blind, placebo-controlled Phase II trial enrolled 282 patients; it was halted early in September 1986 when interim results showed a stark survival benefit: 1 patient died in the AZT group versus 19 in the placebo group over 24 weeks. The trial also showed increased CD4 counts and reduced opportunistic infections. Burroughs Wellcome filed a New Drug Application (NDA) with the FDA on December 2, 1986. The agency approved Retrovir on March 20, 1987, after a review of less than four months under the FDA’s 1-AA (highest) priority designation — the fastest approval in FDA history to that point. From the first laboratory demonstration to market approval, the elapsed time was approximately 25 months.
The approved indication was treatment of adult patients with symptomatic HIV infection — specifically those who had experienced at least one episode of Pneumocystis carinii pneumonia (PCP) or who had an absolute CD4 lymphocyte count below 200 cells/mm³. Burroughs Wellcome set the initial annual cost of Retrovir at approximately $8,000–$10,000 per patient — more than twelve times its estimated production cost — drawing immediate criticism from patient advocates and from ACT UP (which had been founded just eight days earlier, on March 12, 1987) given that the early research was funded largely by US taxpayers through the NCI. Congressional hearings and activist pressure eventually led Burroughs Wellcome to reduce the price twice, in 1987 and 1989.
The FDA later approved AZT as a preventive treatment (1990) and for use in pregnant women to reduce mother-to-child HIV transmission (1994) — a use that dramatically cut perinatal HIV infection rates worldwide. Monotherapy with AZT eventually revealed its limitation: HIV mutates rapidly and develops resistance. By the mid-1990s, combination antiretroviral therapy (cART) — using three or more drugs from different classes — supplanted AZT monotherapy and transformed HIV/AIDS into a manageable chronic condition for most patients with access to treatment. AZT remains on the World Health Organization’s Model List of Essential Medicines and is still used as a component of combination regimens.
The March 20, 1987 approval of AZT marked the first time in the six-year AIDS epidemic — which had by then killed approximately 25,000 Americans — that a licensed pharmaceutical agent was available to treat the underlying infection. Before AZT, physicians could only treat opportunistic infections as they arose; the virus itself was untouchable. AZT changed that, demonstrating that HIV could be pharmacologically suppressed and that the FDA’s accelerated-review mechanisms could be adapted to respond to urgent public health crises.
The approval reshaped the relationship between AIDS activists, the pharmaceutical industry, and the FDA. ACT UP’s campaigns against AZT’s pricing — and later its 1988 protest at FDA headquarters demanding faster access to experimental drugs — permanently accelerated the agency’s drug-approval timelines and led to the 1992 creation of the Accelerated Approval Program, which has since benefited patients with cancer, rare diseases, and other serious conditions.
Scientifically, AZT validated the NRTI class of antiretrovirals and established the biochemical template for dozens of subsequent HIV drugs. The discovery that combination regimens could achieve durable viral suppression, announced publicly in 1996 and built substantially on AZT combinations, converted a uniformly fatal diagnosis into a chronic disease compatible with near-normal life expectancy — one of the most consequential therapeutic achievements of the twentieth century.