Infectious Disease · 1987
AZT (Zidovudine) Trial for AIDS
Azidothymidine
By 1986, AIDS had killed tens of thousands of people in the United States and was accelerating. There was no approved treatment. The immune destruction caused by HIV proceeded inevitably from infection through symptomatic disease to death, typically within two years of an AIDS diagnosis. The Food and Drug Administration's standard drug approval pathway required years of phased trials, a timeline that was incompatible with the urgency of a uniformly fatal epidemic with no therapeutic options. Patient advocacy groups were demanding access to experimental drugs, and pressure on the FDA and the National Cancer Institute to move faster was intense.
Zidovudine had first been synthesized by Jerome Horwitz at the Detroit Institute for Cancer Research in 1964 as a potential cancer treatment; it failed in that application and was shelved. Phillip Furman and colleagues at Burroughs Wellcome identified its anti-HIV activity in 1985, finding that it inhibited HIV reverse transcriptase and blocked viral replication in cell culture. Samuel Broder at the National Cancer Institute pushed the compound into clinical development, moving it through Phase I safety studies at a pace driven by clinical urgency rather than standard scheduling. The placebo-controlled Phase II trial enrolled 282 patients with AIDS or advanced AIDS-related complex.
An interim safety monitoring board analysis halted the trial early when it found 19 deaths among placebo recipients against 1 among those receiving AZT. The magnitude of the difference at interim analysis made continued placebo assignment untenable. The FDA received the application in December 1986 and approved zidovudine on March 19, 1987, completing the review in 107 days, faster than any prior new drug application had been processed. The full clinical trial data were published in the New England Journal of Medicine in 1987.
The early benefits were real but incomplete. AZT reduced opportunistic infections and extended survival in patients with advanced disease. Within months, however, the benefit eroded as resistant viral variants emerged under monotherapy pressure. CD4 counts that had stabilized began declining again, and patients who had responded initially progressed. The failure of monotherapy drove the research agenda toward combination antiretroviral therapy, ultimately yielding the triple-drug regimens that suppressed viral replication durably when introduced in the mid-1990s. Zidovudine remained a component of many of those combinations.
The regulatory pathway the 1987 approval created proved as consequential as the drug itself. The FDA codified accelerated approval as a formal mechanism applicable to serious conditions with no available therapy, using surrogate endpoints as the basis for initial approval with confirmatory post-marketing trials required. That pathway, later refined through the 1992 Accelerated Approval regulations, governed the approval of dozens of antiretrovirals, oncology agents, and other drugs for life-threatening conditions over the following three decades. The principle that the existing alternative of certain death changed the risk-benefit calculus, justifying faster access to a drug with uncertain long-term safety, became embedded in both FDA policy and clinical ethics.
Key People
- Samuel Broder — NCI director who championed zidovudine's clinical development
- Jerome Horwitz — Detroit Institute for Cancer Research chemist who first synthesized AZT in 1964
- Phillip Furman — Burroughs Wellcome researcher who established AZT's anti-HIV activity
- Margaret Fischl — University of Miami investigator who led the pivotal Phase II AZT clinical trial
N Engl J Med. 1987;317(4):185-191
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