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As Elion modified 6-MP, other researchers
discovered that the drug suppressed the immune
response in rabbits. Scientists had already
experimented with organ transplantation, but the
body's natural rejection of foreign substances had
prevented success in all but identical twins, who
have the same genetic structure.
In 1958, a young British surgeon used 6-MP to
prevent temporarily the rejection of a transplanted
kidney in a dog. Excited, Elion gave him several
similar compounds, in the hopes that one would be
even more effective. The following year, he used
Elion's drug azathioprine (known as Imuran), to
transplant a kidney successfully into a dog named
Lollipop. In 1961, doctors used Imuran to perform
the first successful kidney transplant between two
unrelated humans. Thanks to Elion's work, organ
transplantation has become routine today.
In 1968, Elion returned to an area she had first
studied in the 1940s: antiviral medications.
Scientists had long believed that any drug able to
harm the DNA of a virus would be toxic to the
surrounding healthy cells, too. Indeed, one of
Elion's early compounds had shown some
effectiveness against viruses but was so highly
toxic that Elion put it aside in favor of her work
on leukemia, transplantation, and gout.
But when she heard that a similar compound had
shown some antiviral properties, she returned to
the subject.
After several years of work, the Burroughs
Wellcome team triumphantly unveiled acyclovir
(Zovirax), the first medication effective against
viruses. Elion later referred to acyclovir as her
"final jewel.... That such a thing was possible
wasn't even imagined up until then." In 1984,
the year after Elion retired, her lab developed
AZT, the only drug licensed to treat AIDS in the
United States until 1991. Although Elion claimed to
have had little to do with AZT, her methodology had
laid the groundwork for its discovery.
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