Drug industry giant Merck & Co. said Thursday its scientists have developed a detailed molecular picture of an enzyme that the deadly AIDS virus needs to grow.
Merck expects its three-dimensional model of AIDS enzyme protease to yield clues leading to possible AIDS treatments. But a spokeswoman for Merck, based in Rahway, N.J., stressed that any treatment stemming from the company's advance was many years away.
The discovery, published in the British scientific journal Nature, was viewed as an important step. "It is a very exciting, very promising advance," said Charles Craik, a pharmacy professor at UC San Francisco and an expert on protease.
No Magic Bullet
However, Craik said Merck's discovery wouldn't discourage research into other ways to attack the AIDS virus. "I wouldn't say it is a magic bullet," he said.
According to Merck, protease helps the AIDS virus reproduce by separating two AIDS proteins that are fused together. The virus can't copy itself until protease slices those proteins apart.
Merck hopes to use its model to find a chemical that will prevent protease from clipping the fused proteins. So far, Merck has been able to block protease in the laboratory by using a chemical called pepstatin, but the chemical won't work inside the body.
In composite trading on the New York Stock Exchange, Merck's shares closed at $64.75, up $1.
Robert H. Uhl Jr., a drug industry analyst at Salomon Bros. in New York, said Merck's research "is still at the level of basic science." He said, "I don't see anybody making great strides toward developing drug therapy. The research seems to be at a temporary plateau phase."
Uhl said that for a treatment or cure to be a big money-maker for a drug company, it normally would need to combat a disease affecting more than the number of people suffering from AIDS.
The promise of an AIDS treatment can influence a company's stock price. Shares in ICN Pharmaceuticals soared three-fold over the summer of 1986 to a high of $34 on speculation that its drug, ribavirin, would eventually be approved for use against AIDS. The drug is currently in clinical tests after a long delay, but the Costa Mesa-based company has become the subject of an investigation by the U.S. Justice Department into unspecified concerns raised by the U.S. Food and Drug Adminsitration.
ICN's shares closed at $6.75 on Thursday.
But when Burroughs-Wellcome received FDA permission to market the drug AZT to treat AIDS symptoms on March 20, 1987, the price of its British parent, Wellcome PLC, rose only the equivalent of 62 cents to $7.97 in London trading. AZT, or zidovudine, seems to help prolong the life of some AIDS patients, but it is not a cure.
AIDS is a fatal disease that attacks the body's immune system. Since 1981, 86,157 cases of the disease have been reported, and 49,390 persons stricken with the disease have died. The Centers for Disease Control in Atlanta estimates that between 1 million and 1.5 million people have been exposed to the AIDS virus.
Besides Merck, two other drug companies, Abbott Laboratories and SmithKline Beckman, are conducting research into protease. Robert Janicki, director of research and development at Abbott Laboratories, said Merck's discovery was "of significance," but he added, "we'll continue our work on the structure of protease to confirm Merck's findings."
SmithKline, based in Philadelphia, has studied protease since 1986 and developed the first test that could be used to find potential blockers. But the company is also looking at another possible AIDS treatment.
SmithKline is testing a synthetic protein that acts as a decoy, attracting the AIDS virus away from the body's cells. It started testing that protein, called T-4, at Walter Reed Army Medical Center in Washington earlier this month.