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  • AZT: The Clinical Trial that led to its approval.

    Posted on January 28th, 2011 admin No comments

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    The clinical trial that led to the approval of AZT for the treatment of AIDS in 1987 is a landmark event, not only in the field of HIV medicine but I believe it had a major impact on the drug regulatory process that has had effects in all fields of clinical medicine.

    The trial reported in the New England Journal of medicine, had produced a dramatic result (1). Before the planned 24 week duration of the study, after a mean period of participation of about 120 days, nineteen participants receiving placebo had died while there was only a single death among those receiving AZT.   This appeared to be a momentous breakthrough and accordingly there was no restraint at all in reporting the result; prominent researchers triumphantly proclaimed the drug to be “a ray of hope” and “a light at the end of the tunnel”.  Because of this dramatic effect, the placebo arm of the study was discontinued and all participants offered 1500mg of AZT daily.

    I was treating many HIV infected individuals in 1987 when the drug was approved for the treatment of advanced AIDS.  I was puzzled by the results of the trial quite simply because those patients of mine who resembled trial participants would not have died in the period before the placebo arm was terminated.   Many patients enrolled in the trial had experienced an episode of pneumocystis pneumonia within four months of participation.  My patients and those of other experienced physicians were unlikely to die within four months of an episode of this type of pneumonia.

    This means that if my patients had enrolled in the trial it’s probable that there would have been no deaths at all by the time the placebo arm was discontinued and thus an apparent dramatic effect of AZT on mortality would not have been seen.

    There had to be an explanation for the discrepancy between the outcome of my patients (and those of other experienced physicians) and individuals participating in the trial; I was confident that an academic clinical researcher would sort this out.

    But no explanation was forthcoming.

    I was then able to obtain a copy of the FDA review of the  application submitted by Burroughs Wellcome, (the NDA) and tried to understand the discrepancy myself.

    I reviewed the report as a primary care provider to people with AIDS, and thus challenged very aggressively, both by my colleagues and by many patient advocates, to prescribe AZT.  I also reviewed the report as a clinical researcher who had designed and implemented clinical trial protocols.

    This is the report I wrote after reading the review of the NDA. (1)

    Essentially it makes the point that patient management strategies were the most significant factor influencing mortality, at least in the short term, and it could not be excluded that differences in the ways patients were managed in the trial, were to a greater or lesser extent, responsible for survival differences.  Patient management in this context refers to all the measures available, before the introduction of specific antiviral therapy, to care for individuals susceptible to infections and malignancies associated with impaired cell mediated immunity.   For example, the speed with which a potentially fatal opportunistic infection is suspected and diagnosed and efficiently treated can make the difference between life and death.   Much experience in the treatment of immunocompromised individuals had been gained before the AIDS epidemic, particularly in the field of renal transplantation, but also in other conditions.

    The AZT trial took place in 12 centers across the country.  There was no uniform approach to patient management during the trial; each of the 12 medical centers approached the most important determinant of life and death in the short term, independently.

    I will return to the implications of this lack of uniformity in patient management strategies.

    It may seem surprising today that so little attention was paid to developing methods for the optimal day to day care of patients with AIDS, but at the time there was a pervasive defeatist attitude concerning treatment.    All too commonly it was felt that nothing could be done to halt the inevitable progression of the disease to its fatal end.

    I’m not sure that it’s even possible to adequately describe the terror and desperation felt in the early 1980s.   At that time doctors on the front lines were trying to do what they could for their patients but had received little help from experts at academic medical centers and virtually none at all from Government scientists, although by 1981 when the first AIDS cases were reported,  diseases of the immunocompromised host had already become a distinct medical subspecialty.

    But by 1986 nothing of any use regarding treatments had come from the Public Health Service.  For example, people with AIDS had to wait until 1989 for the CDC to issue guidelines for the prevention of pneumocystis pneumonia, the most frequent cause of death among them, while this type of pneumonia had often been routinely prevented in many other individuals who were also at risk because they were recipients of kidney transplants, or were children with leukemia.  The means to prevent pneumocystis pneumonia had been published in 1977.

    Some community doctors were not waiting for recommendations from government scientists or from their colleagues in academic medical centers, and were learning how to care for their patients. I and several colleagues were preventing pneumocystis pneumonia among our patients for many years before the Public Health Service got around to making their recommendations.

    Those who had taken on the medical leadership of the epidemic were telling us in their silence that there was nothing much we could do – we just had to wait for a drug.

    Then, after six years of silence regarding treatments Government scientists at last told us that help was on the way.  Dr Samuel Broder who was head of the National Cancer Institute appeared on television shows trumpeting the benefits of a drug he called Compound S.   I well remember a TV show where he appeared with an AIDS patient who enthusiastically attested to the benefit he had received from the drug, presumably from 1.5G of AZT daily.

    A note about patient management strategies:

    There really was a lot that we were able to do for our patients before the advent of specific antiviral therapy.    After all, most deaths were caused by opportunistic infections, and we certainly could do a great deal to prevent and treat many of them.

    Without much guidance some doctors with large practices were able to develop structured programs of patient care.   These included the prevention of opportunistic infections when possible, the determination of susceptibility to some, and their early diagnosis and aggressive treatment.

    All too often symptoms, particularly diarrhea, fever, weight loss, and anemia were simply attributed to AIDS and not investigated. In fact, such symptoms could frequently be ameliorated if their causes were aggressively sought.  More often than not they were caused by treatable conditions.   So, patient management strategies included aggressively trying to establish the causes of such symptoms and treating them.

    It was the experts who in fact were more likely to attribute them to AIDS and therefore consider them to be untreatable

    The provision of general support, including attention to nutrition and mental health issues are parts of patient management.

    All of this is pretty labour intensive doctoring, but these measures were able to prolong the lives of our patients.

    Needless to say, it was community doctors who had to develop such strategies without much help from the experts. I suppose one has to conclude that the government medical leadership of the response to the epidemic, unlike community doctors dealing with it, must have felt that nothing could be done for people with AIDS, that the only hope to be found was in a new drug.

    Returning to the original AZT trial:

    If in the short term patient management strategies can make the difference between life and death is there any reason to consider that such strategies may have differed in those receiving placebo or AZT?

    The reason why randomized placebo controlled clinical trials are blinded, (so that neither investigator nor participant knows who is receiving placebo or active drug) is to minimize bias.  Bias can influence the outcome that might incorrectly be attributed to a drug effect.   But it’s impossible to blind a trial using AZT.  The drug causes changes in routine blood counts that investigators need to see.   Therefore we must conclude that investigators could know who was receiving AZT or placebo.   The FDA reviewer was aware of this.

    If patient management is the most important determinant of mortality in the short term, could bias have influenced the ways patients were managed?

    Unfortunately, because this was essentially an unblinded trial, the answer is yes.

    Patients known to be taking AZT or placebo might have unintentionally been treated differently, with either greater or lesser care, when the investigator was also the treating physician.  AZT may therefore have been even more effective than claimed or may have been worse.

    In some centers were there  instances where the participant also had a personal physician?   There was no analysis of trial outcomes based on this difference.  There was also no analysis of outcomes by study center.   New York City was a study site.  Were patients referred to the study site at St Lukes Roosevelt Hospital Center by personal physicians who continued to care for their patients?

    Information must still be available regarding mortality at different study centers, and in relation to whether the participant was treated by the study doctor or had a personal physician.

    Dr Fischl was the principal investigator of the trial but I don’t know if she and her team at the University of Miami were the treating physicians as well as the trial investigators.

    Incidentally this also brings up the important question of   the propriety of an individual serving as both investigator and treating physician. I believe these two roles are often incompatible; that there can be an insuperable conflict of interest that should preclude an individual from functioning in these two roles concurrently.  I have served in both capacities but in most instances, not simultaneously.

    The survival benefit in the trial attributed to AZT   may therefore, to a greater or lesser extent have been due to differences in how placebo or AZT recipients were managed.  All we can say is that the question remains, not that this was in fact the case.

    The problems resulting from unblinding were clearly acknowledged by the FDA reviewer but not by the study investigators.   Around the time of the trial report I took part in a Canadian Broadcasting Corporation telephone interview.  When I tried to bring up the issue of bias I was cut short by a NIH official who said this was too technical a detail for the audience!

    Very unfortunately, the most vocal of the critics of the AZT trial included some individuals who believed that HIV could not cause AIDS.   Their strident criticisms were unhelpful; it was evident that none of these critics had any experience in clinical trial methodology.

    It was immensely disappointing to find that many of the problems in the trial were identified by Ellen Cooper, the FDA reviewer, yet the drug was still approved at a dosage that proved to be so toxic that another trial compared a similar dose with half that dose. This exercise resulted in excess deaths among those taking the higher dose. (A randomized controlled trial of a reduced daily dose of zidovudine in patients with the Acquired Immunodeficiency Syndrome. Margaret A Fischl et al. NEJM 1990: 323:1009-14).

    Among the many bizarre aspects surrounding the introduction of AZT was the claim that the excess deaths in those receiving the higher dose were due to AIDS – that in the case of AZT, less is better – the explanation given for the superiority of the low dose compared to the high dose was that the lower dose allowed people to remain on the drug for longer – not even a hint that the higher dose contributed to the increased mortality.  Here is the representation of the mortality differences between the two dosages:

    It’s worth reproducing the disingenuous words in which this is stated.

    “The findings in this study indicate that a lower daily dose of zidovudine is at least as effective ………as the initially tested dose of 1500mg per day and is less toxic”  “Moreover low dose therapy was associated with a better survival rate” “The reason for this better interim survival is not certain, but is most likely related to the greater likelihood that continuous antiviral therapy can be maintained with lower doses of zidovudine”

    If ever evidence was needed that AZT – at the initial recommended dose of 1500mg daily probably caused an excess mortality – the figure above provides it, despite the disingenuous claims of the authors that the deaths were due to AIDS.  A rational response would have been to work out the minimum effective dose. Why stop at 600mg a day? 300mg a day is probably just as good.  It is the dose I prescribed with no evidence that 300mg AZT daily was associated with a worse outcome.  As described in another article it is likely that endogenous interferon plays a role in pathogenesis, and AZT promptly removes it from the circulation

    That the possibility that more people on the higher dose died from AZT toxicity  is not even mentioned in the above report is a sad indication of what has become of the discussion of results section in a scientific paper, at least in the field of AIDS. Traditionally all reasonable possibilities are discussed, even to be dismissed, but not in this paper.

    The publicity following the approval of AZT was huge. Doctors received a video where AZT was billed as “A ray of hope”. I recall white coated doctors speaking about the “light at the end of the tunnel”.

    The dosage schedule was absurd.  There was no scientific basis at all for four hourly dosing.  AZT was to be taken even at night, and patients were given beepers to remind them to take their medicine exactly at the appointed time.   AZT is not the compound that blocks HIV replication. It is changed into the active compound within the cell by the addition of phosphate, and so blood levels tell you nothing about the levels of the active form in the cell. It is also a little gruesome – because as it turned out adherence to this difficult ritual was associated with great toxicity, and I can imagine that sometimes the manifestations of this toxicity would be attributed to AIDS and patients encouraged to still keep their beeper going and continue to take AZT.  At first the drug was only available if patients met certain criteria, and I know colleagues, devoted to their patients, who forged the papers to enable their patients to get the huge dose of AZT.   All on the basis of an approval based on a terribly flawed trial.

    Of course the need for some therapy was quite desperate and one must wonder if this desperation lowered the threshold of what was deemed to be acceptable, so that there was perhaps less scrutiny of the trial and the failures of AZT at the dose used – until of course toxicity forced a reconsideration of the dosage.

    The approval of AZT also set an important precedent that seemed to go unnoticed at the time, and indeed has escaped comment subsequently.

    AZT was the first drug of its kind to be approved for lifelong human use.

    The drug  is an analogue of thymidine which is a normal building block of DNA.  It is incorporated, instead of thymidine, into DNA during its synthesis, and then immediately stops further DNA chain elongation because nothing can be added to it.

    The use of such analogues able to disrupt DNA synthesis was considered to be perilous when I first dealt with them in the 1960s.  I had used them in the virology laboratory in experiments conducted in vitro, and they were handled with caution, as potentially hazardous substances.

    In clinical practice, apart from acyclovir which is a similar drug, but in a special category,   such analogues were used systemically in malignancies and some viral infections – such as herpes encephalitis or neonatal herpes, but only for short periods.  Acyclovir is in a different category as it can only be used by the herpes virus enzymes, and has no effect in cells not infected with herpes viruses.    The idea of a possibly lifelong exposure to a DNA chain terminating compound – or even an analogue that is incorporated into DNA that continues to be synthesized, was I believe a novel concept at that time. To emphasize, what was novel was not the use of such compounds, but a life time exposure to them. .    So, I was somewhat concerned at the very idea of this approach, and also found it strange that colleagues were mostly silent on this issue.  These analogues need to undergo changes in the cell, and are added to the growing DNA chain by enzymes, either those that belong to the cell, or enzymes that are specific to the virus, such as the reverse transcriptase of HIV.  It was hoped that AZT, which is turned into its active form by cellular enzymes, would be preferentially used by the viral rather than the cell enzymes that synthesize DNA, and therefore not terminate cellular DNA synthesis; there was some evidence to support this. HIV’s reverse transcriptase adds AZT to the viral DNA chain, while cellular enzymes add it to cellular DNA. Cell DNA is found in two different sites. In the nucleus it is the DNA that constitutes our genome – that is all the information that determines our inherited characteristics. DNA is also found in cellular structures called mitochondria which are the source of the energy needed by the cell. Two different enzymes are needed to make DNA in each situation. While there was comforting evidence that AZT much preferred the viral reverse transcriptase to the enzyme that makes our genomic DNA, this preference was less evident in the case of the enzyme that makes mitochondrial DNA. In fact much of the toxicity of AZT is a result of its effect on mitochondrial DNA synthesis.

    I never prescribed AZT when it was first approved, and when I did it was at a dose of 300mg a day.  Because I was one of the few physicians around 1987 who did not prescribe AZT I attracted patients who were reluctant to take it and whose physicians were nor supportive of this choice.  I also received severe criticism for my position

    This original AZT trial did however clearly demonstrate to me how important patient management strategies were in the treatment of AIDS, particularly in the days before the more potent antiviral drugs became available.

    The New England Journal of medicine, which reported the original trial, rejected my review of the FDA report.    I sent copies to all the clinicians who were prominent in the field – as well as to several patient advocates. There was not a single response – not even to reject the points I made.  Just total silence.  Realizing the difficulty in publishing independent material we – myself and mostly Michael Callen , decided to publish an independent journal.  We called it AIDS Forum. Michael was the editor, and it lasted for three issues.

    One last comment on the baneful effects of this trial:  While it was not responsible for the undue influence industry has on medical practice, this trial probably provided the greatest impetus towards the sad situation we are in today. It is possible that in the field of HIV medicine, industry had its greatest opportunity to establish a firm hold on many different ways to influence practice. These include not only marketing strategies, but influence on guidelines committees, support of continuing medical education, the support of medical conferences and influence on reports of their proceedings, as well as the invention of the Key Opinion leader or KOL, to provide information to physicians.    “Key Opinion Leader” is not the only absurd designation in this field.  We also have “Thought Leader”.  Needless to say these distinctions are not conferred by any academic institution; I would assume that the marketing departments of pharmaceutical companies are responsible for choosing who deserve these titles.


    N Engl J Med 1987; 317:185-191July 23, 1987