FDA Approves New Drug in Fight Against AIDS Virus

The Food and Drug Administration approved the first in a new class of AIDS medicines Monday, clearing patients to start adding the drug nevirapine to their treatment combinations this summer.

Nevirapine, to be sold under the brand name Viramune, targets the same element of the human immunodeficiency virus that many older medicines do, inhibiting an enzyme key to HIV’s reproduction. But it is in a new class of drugs specially developed to fight the reverse transcriptase enzyme by blocking the receptor where the enzyme sits, much as a key fits into a lock.

Adding nevirapine to such older drugs as AZT and ddI modestly boosts their ability to lower the amount of HIV in the bloodstream and strengthens the immune system, studies suggest.

But it cannot be used alone, because HIV develops resistance to nevirapine rapidly, the FDA warned. Combining it with older drugs forces HIV to mutate in many different areas simultaneously before it can resist treatment.

Manufacturer Boehringer Ingelheim Corp. said Viramune will be on pharmacy shelves by Aug. 1.

Now doctors must decide how and when to best use nevirapine, said Dr. David Feigal, the FDA’s chief of AIDS drugs.

“The whole key to the use of this drug is to find the right combinations” with older medicines, he said. “We don’t really know where these things are going to work out. But the fact this was a new class of drugs, and required a different set of mutations, gave this product some importance.”

Nevirapine is the ninth anti-HIV drug available for patients and the fifth approved in just the last six months.

Nevirapine isn’t exciting doctors as much as protease inhibitors did. That group, approved last winter, targets a second enzyme vital to another step in HIV’s life cycle.

Indeed, nevirapine’s class of “non-nucleoside reverse transcriptase inhibitors” was largely shelved in 1992 when their rapid resistance was discovered.

But over the next four years, doctors discovered that combining three or even four AIDS medicines may work best. Doing so sometimes lowers the HIV in blood to undetectable levels--essentially allowing patients to manage AIDS like a chronic disease instead of as a fast killer--and slowing viral resistance.

But to brew those cocktails, doctors needed more drug options, and Boehringer, which had continued to pursue non-nucleoside treatment, introduced nevirapine.

For patients failing other treatments, adding nevirapine to an AZT-ddI mix provided about an extra 10 immune cells per deciliter of blood and kept HIV from rebounding as rapidly.

Then Boehringer studied patients who had never received any drug treatment. The triple therapy almost eliminated HIV in the blood of 70% of patients treated for six months. Just 40% of patients got that benefit from AZT and ddI alone.

Nevirapine was approved only for adults, but the University of Massachusetts is studying it in children.