The San Francisco Chronicle - Wednesday, November 8, 1995 Page B1
Carl T. Hall /San Francisco Chronicle

A U.S. Food and Drug Administration advisory panel voted to recommend approval of a Hoffmann-La Roche Inc. drug -- sequanivir, known by the trade name Invirase -- for AIDS patients with no other options. The move followed a decision Monday by the same advisory panel backing yet another long-awaited new AIDS drug, Glaxo Wellcome's 3TC.

Assuming the full FDA goes along as expected, Invirase would be the first of a new type of drug, called "protease inhibitors," approved for AIDS patients since the original AIDS drug, Glaxo's AZT, hit the market.

This new type of drug works by blocking the ability of the AIDS virus, or HIV, from replicating. Already, newer versions are being developed that may be before the FDA as early as next year.

AIDS groups have been demanding rapid access to the new protease drugs -- and FDA Commissioner David Kessler appears anxious to comply. He called the new drugs "the most active compounds that we have seen" against HIV.

Despite the enthusiasm, nobody viewed the latest breakthroughs as anything resembling a cure.

Clinical trials suggest both of the new drugs are most effective when used in combination with Glaxo's AZT, the most widely prescribed anti-viral, which hit the market eight years ago. The advisory panel recommended approval of Invirase only when used with existing drugs such as AZT. Its use as a stand-alone therapy awaits more study.

Although the beneficial effects don't show up in all patients, and can wear off quickly, the new drugs offer some hope to patients with few other options, said Brenda Lein, who tracks AIDS treatments at Project Inform, a San Francisco information and advocacy group.

But she said more is needed to round out the AIDS treatment arsenal. The key missing element, she said, is a long-term defense against infection.

Apart from the two drugs recommended for approval this week, scores of drug companies and academic researchers are working on a whole new class of potential AIDS treatments called "gene therapies." None are close to FDA approval.

The approach typically involves injecting a new gene or smaller bits of genetic material into patients. The inserted material may then reproduce or be incorporated into existing cells. Although the details vary, the basic idea is to give the body the blueprint needed to build its own new tools for fighting off disease.

Cutting-edge research is being done by a large number of small, private biotech companies and a handful of public ones such as Viagene, a San Diego-area company recently acquired by Emeryville-based Chiron Inc., and Cell Genesys Inc. of Foster City.

Important work is also being done at the Fred Hutchinson Cancer Center in Seattle and by university scientists in Michigan and Southern California.

"What really keeps a virus under control is immune-system surveillance," Lein said. "That may be the trick to making this a treatable disease."

Cell Genesys hopes to perfect so-called universal T-cells, described as a sort of guided missile system that can be programmed to attack HIV.

The first clinical trials involved a few sets of identical twins. In each set, one was HIV-positive and the other HIV-negative. Disease-fighting cells were removed from the healthy twin, retooled in the laboratory, then injected into the infected twin.

The company hopes the same strategy will aid in the fight against cancer. But it's only been tried in a handful of patients so far.

"It's very far away," said Cynthia Robbins-Roth, editor of BioVenture View, a trade publication in San Mateo. "Nobody has this figured out yet."

Part of the problem, she noted, is the surprising ability of the AIDS virus and other disease-causing microbes to change forms, thwarting whatever medical science throws at them.

"It's turning out that the bugs are a lot smarter than people gave them credit for," she added.

The scientific hurdles have already proven to be more than many investors can stomach. Cell Genesys stock, for example, had been as high as 22 in 1993, only to plummet to a recent low of 33/4. It got a boost recently when the company signed a development alliance with pharmaceutical giant Hoechst Marion Roussel. The stock closed yesterday at 7 5/16.

Chiron Viagene, meanwhile, is midway through a two-year trial involving 15 medical centers and about 200 patients.

Early-stage trials in almost 90 patients were designed simply to demonstrate that the therapy was safe enough for further testing. But they did yield "the kind of immune responses we wanted," said Steven Mento, company president.

Isis Pharmaceuticals in Carlsbad, is banking on "antisense" technology, sometimes described as a kind of molecular chewing gum that can be "stuck" to a virus in such a way that it can't infect healthy cells.

The company is furthest along with a potential treatment for CMV retinitis, a common form of blindness that strikes AIDS patients, but has a separate effort under way that targets AIDS directly.

Strictly speaking, the Isis program falls outside the usual definition of "gene therapy." But Isis President Daniel Kisner said he's still a believer in the approach.

Copyright (c) 1995/San Francisco Chronicle. Reproduced with permission. Reproduction of this article (other than one copy for personal reference) must be cleared through the Permissions Desk, San Francisco Chronicle, San Francisco, CA.

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