February 28, 2007 / 6:38 PM / 12 years ago

Merck integrase inhibitor suppresses HIV: studies

LOS ANGELES (Reuters) - Merck & Co. Inc.’s experimental HIV drug in a new class called integrase inhibitors can control the virus in nearly 80 percent of previously treated patients, when combined with other commonly used AIDS drugs, researchers said on Tuesday.

“This is a major step in HIV therapeutics,” said Dr. John Mellors, chief of infectious diseases at the University of Pittsburgh, noting that the suppression rates mirror those seen with current drugs in newly-diagnosed patients.

Overall results from two Phase III studies show that after 16 weeks, 79 percent of patients treated twice daily with raltegravir, previously known as MK-0518, saw HIV levels fall to less than 400 copies per milliliter, said Dr. Roy Stiegbigel, professor of medicine, microbiology and pathology at the State University of New York at Stony Brook, and a study investigator.

Of patients treated with a placebo plus background therapy, 43 percent achieved that target, he said.

Stiegbigel also said that 61 percent of patients treated only with the integrase inhibitor achieved viral load suppression, compared with 5 percent of patients treated with placebo alone.

Each study involved about 350 patients who had stopped responding to current drugs.

“It is quite clear that across all baseline characteristics there was marked superiority of having raltegravir added,” said another trial investigator, Dr. David Cooper of the University of New South Wales in Sydney, Australia.

He said there was no difference between raltegravir patients and others in terms of adverse events, including liver inflammation.

The findings, presented at the 14th Conference on Retroviruses and Opportunistic Infections, offer a potential new weapon in the growing armory of drugs that fight HIV. The drug mixtures can keep HIV patients healthy for years, although they are not a cure.

Merck has said it expects to file for U.S. Food and Drug Administration approval of raltegravir by mid-year.

There are several classes of HIV drugs, also known as antiretroviral drugs. Each class attacks the virus at a different point in its cycle of replication.

When the human immunodeficiency virus infects a cell, usually an immune system cell called a T-cell, it attaches to the cell, pierces it and inserts its own genetic material.

The viral DNA re-programs the cell, in essence hijacking it, and forces it to produce copy after copy of the virus, which it pumps into the blood to infect other cells.

The integrase inhibitors stop the insertion of the HIV viral DNA into human DNA, shutting down the virus factory.

Other HIV drugs target other enzymes involved in this hijacking process.

“Based on the safety profile of the integrase inhibitors, confirmed in the data coming out ... it is highly likely that these drugs will eventually move into front line treatment regimens for HIV, both in combination with, and instead of, certain existing product classes,” Geoffrey Porges, an analyst at Sanford Bernstein, said in a research note this week.

He suggested that integrase inhibitors are most likely to replace non-nucleoside reverse transcriptase inhibitors, such as Sustiva, sold by Bristol-Myers Squibb and Merck, and potentially also protease inhibitors.

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