A fourth drug has been approved by FDA for the treatment of HIV and AIDS. The anti-viral drug is specifically for adults with advanced HIV infection who no longer respond to or are intolerant of other anti-viral drugs.
Zerit (stavudine, also known as D4T) belongs to the nucleoside analog class, which includes previously approved Retrovir (zidovudine, also known as AZT), Videx (didanosine, also known as DDI), and HIVID (zalcitabine, also known as DDC). Nucleoside analogs are thought to slow the progression of AIDS by inhibiting HIV replication. Data indicate that drugs in this class may delay the onset of AIDS symptoms in HIV-infected individuals, and may extend patient survival.
The drug was approved under FDA's accelerated approval mechanism allowing the drug's effectiveness to be assessed by surrogate rather than clinical endpoints. The major surrogate endpoint in the Zerit trials is CD4 cell counts.
In an ongoing trial comparing Zerit with continued Retrovir treatment of HIV-infected adults, all participants had taken Retrovir for at least 24 weeks. Their CD4 cell counts, which reflect the strength of the immune system, were between 50 and 500. (Counts in healthy individuals are normally 1,000 or higher.) Twelve weeks into the trial with 359 patients, the mean CD4 cell count in patients receiving Zerit increased by 22 cells per milliliter of blood, while the mean count in patients continuing on Retrovir declined by 22.
FDA concluded that the increase in CD4 counts is a likely indicator of a meaningful clinical benefit. Accelerated approval applicants must continue studies after approval to evaluate the true clinical benefit of their drugs. If data do not verify a benefit, FDA may withdraw its approval.
Between 15 and 21 percent of patients in Zerit trials experienced the drug's major side effect, peripheral neuropathy, which causes pain and tingling or numbness in the hands and feet. This side effect appears to be dose-related and can usually be reversed by stopping treatment.
In October 1992, Zerit became the first drug FDA granted parallel track status, which allowed the agency to make the promising new drug available to patients before approval. Since then, about 11,000 patients have been treated with Zerit.
Zerit's manufacturer is Bristol-Myers Squibb Co., New York, N.Y.
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