By Charles Craig

Less than three months after submitting its new drug application (NDA) for Viracept, Agouron Pharmaceuticals Inc. Friday received marketing clearance from the FDA for the HIV protease inhibitor for treatment of adults and children.

The agency also approved Abbott Laboratories' protease inhibitor, Norvir, for children, making it and Viracept the first two protease inhibitors for pediatric use. Abbott, of Abbott Park, Ill., received approval of Norvir for adults in March 1996. (See BioWorld Today, March 4, 1996, p. 1.)

Trading in Agouron's stock (NASDAQ:AGPH) was halted early in the day, but when it resumed the La Jolla, Calif., company's shares jumped 6.3 percent to close at $80.50.

Viracept will compete with three other protease inhibitors, which are the newest class of antiviral drugs in the war on AIDS. When used with reverse transcriptase inhibitors, such as AZT and 3TC, studies have shown the combination of drugs can reduce the amount of HIV in AIDS patients to undetectable levels.

Protease inhibitors attack HIV replication near the end of the cycle while reverse transcriptase inhibitors interfere near the beginning. The two classes of drugs are combined to try to counter the fast-mutating AIDS virus' ability to develop resistance.

The biggest selling AIDS combination includes AZT and 3TC, which are marketed by London-based Glaxo Wellcome plc, and Crixivan, a protease inhibitor made by Merck & Co., of Whitehouse Station, N.J.

Agouron submitted two NDAs for Viracept: one for a tablet for adults and the other for an oral powder for children. Agouron officials said as many as 7,000 to 10,000 children in the U.S. are infected with HIV.

Agouron will sell Viracept in the U.S. It has a collaboration with Japan Tobacco Inc., of Tokyo, for sales in Japan and Asia and with Roche Holding Ltd., of Basel, Switzerland for marketing in Europe.

Roche also has its own protease inhibitor, Invirase, which was the first in the class to be approved by the FDA.

Viracept, available next week, will cost about $5,650 per patient per year. The drug, approved without review by an FDA advisory panel, is considered as potent as Crixivan. Viracept's advantages, Agouron officials have said, are lack of serious side effects, more convenient administration and fewer problems interacting with other drugs.

In addition to Crixivan, Viracept will face tough competition from another protease inhibitor nearing the market, Vertex Pharmaceuticals Inc.'s VX-478, which is in Phase III trials. The Cambridge, Mass.-based Vertex is developing the drug with Glaxo.

Agouron filed the NDAs for Viracept in late December 1996. The marketing applications were supported by three Phase III studies. In all three trials, which evaluated the drug alone and in combination therapies, Viracept achieved statistical significance in reducing viral load and raising immune system CD4 T cell counts — the two markers against which all AIDS drugs are judged for effectiveness. *