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Merck AIDS Pill Isentress Effective, FDA Staff Says
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By Angela Zimm
Aug. 31 (Bloomberg) -- Merck & Co.'s HIV pill Isentress, aimed at patients who fail to respond to other treatments, is effective in suppressing the virus that causes AIDS, U.S. regulators said.
Studies by Merck show the medicine reduces HIV in the blood of patients with resistant forms of the human immunodeficiency virus, or HIV, staff of the Food and Drug Administration said in documents posted today on the agency's Web site. A panel of expert advisers to the FDA will meet Sept. 5 to recommend whether Isentress should be cleared for sale.
Isentress uses a different mechanism to attack HIV than marketed AIDS drugs. Approval would add another strategy for doctors to use against resistant HIV strains in an estimated 76 percent of patients. The product may generate more than a $1 billion in annual sales, according to Mario Corso, an analyst with Summer Street Research Partners in Boston.
``FDA analyses of the safety and efficacy data submitted in the new drug application support the applicant's findings,'' FDA staff reviewers said in the documents.
Merck rose 73 cents, or 1.5 percent to $50.39 at 9:47 a.m. New York time in Nasdaq composite trading, after gaining 14 percent this year before today.
Isentress blocks the process used by the HIV virus to insert its genetic material into human DNA, allowing replication. The drug targets an enzyme called integrase, which HIV uses to accomplish this task. Studies have shown the medicine helps patients with resistant strains of HIV when used in combination with other drugs.
Almost Undetectable
Two studies presented at an AIDS meeting last year found that Isentress, also known as raltegravir, reduced the virus to almost undetectable levels after four months in 61 to 62 percent of patients getting the medicine in combination with other anti- HIV drugs. That compares with 33 to 36 percent of patients who got a placebo along with their most effective treatments.
Successful treatment reduces levels of the virus to less than 50 copies per milliliter. The patients came into the studies with at least 1,000 copies of the virus per milliliter of blood.
``Phase 2 and 3 trial data provide evidence that the antiviral activity of raltegravir is superior to optimized background therapy in treatment experience patients with few or no remaining treatment options,'' FDA reviewers said in the document.
Pfizer's Selzentry
Last month, Pfizer Inc., the world's biggest drugmaker, won FDA approval for Selzentry, the first HIV drug to block the CCR5 receptor, a chemical portal on immune system cells used by the virus. Selzentry, also known as maraviroc, is the first new class of AIDS medicine to reach the market in a decade.
In approving Selzentry, the FDA required Pfizer to conduct additional studies on the drug's side effects. The package insert carries the agency's strongest caution, a black box surrounding the prescribing information, warning about liver damage and possible heart attacks.
There are now 30 U.S.-approved AIDS treatments, according to the U.S. National Institutes of Health.
All HIV drugs are designed to interfere with a part of the HIV life cycle of infection and replication. HIV attacks and destroys white blood cells, which the immune system uses to fend off invasions from viruses and bacteria.
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