By Lisa Seachrist

Washington Editor

Immunex Corp.¿s stock soared on news that a pivotal trial testing the company¿s rheumatoid arthritis (RA) treatment, Enbrel (etanercept), in patients with early, active RA showed the drug slowed the progression of disease and reduced the signs and symptoms of the disease.

Seattle-based Immunex announced the results of the clinical trial after the markets closed on Monday, and was greeted Tuesday with a 33 percent increase in the company¿s stock (NASDAQ:IMNX), which closed Tuesday at $142.312, up $35.312.

The study results will be used to bolster efforts to expand the drug¿s label to include patients with early disease. Immunex intends to file for that label change in the third quarter of this year. Enbrel is co-marketed with Wyeth-Ayerst Laboratories, a division of American Home Products Corp., based in Madison, N.J.

¿This is tremendously good news for patients with RA and for Immunex,¿ said Michael Sheffery, partner at OrbiMed Advisors LLC, of New York. ¿They set a fairly high bar to cross with this trial, and they did. Enbrel is going to be at least a $500 million product and, perhaps, a billion-dollar product.¿

An injectable, genetically engineered protein ¿ two molecules of recombinant human tumor necrosis factor (TNF) receptor ¿ Enbrel works by binding TNF and blocking its interactions with cells that respond to its signal and damage tissues. TNF is found at elevated levels in fluid around the joints of RA patients.

In November 1998, the FDA approved Enbrel for use in patients with moderate to severe RA who have not responded well to disease-modifying antirheumatic drugs (DMARDs) such at methotrexate. The drug also can be used in combination with methotrexate.

The study the companies reported Monday included 633 RA patients with early, active disease who had suffered from RA for less than three years and had never been treated with methotrexate. The study participants were randomized to receive either 25 milligrams or 10 milligrams of Enbrel or up to 20 milligrams of methotrexate for 12 months. Patients received both Enbrel or placebo injections twice a week and methotrexate or placebo tablets once a week, in order to ensure that patients didn¿t know which therapy they were receiving.

Using joint X-rays, the researchers showed that Enbrel can slow the progression of joint damage that is often a consequence of RA. In addition, patients receiving Enbrel had greater improvement in the signs and symptoms of RA than with the control therapy, methotrexate.

Tim Warner, spokesman for Immunex, said it¿s ¿very important to show that we can slow the progression of the disease with Enbrel. We know Enbrel has a demonstrated ability to reduce the signs and symptoms, but we needed to know it could slow the progression.¿

Because Enbrel can slow the progression of the disease, it has entered the ranks of DMARDs such as methotrexate, which slows the destruction of joints. Non-steroidal anti-inflammatory drugs (NSAIDs) and their first cousins, the COX-2 inhibitors, affect only the signs and symptoms, like pain and stiffness.

Enbrel Best Of All Worlds¿

Mike King, senior analyst with BancBoston Robertson Stephens Inc. in New York, called Enbrel ¿the best of all worlds. You have the effectiveness of DMARDs with the safety profile of COX-2 inhibitors.¿

Based on first-quarter sales results and the pivotal trial outcomes, King altered his prediction for the drug and now sees it crossing the billion-dollar mark in 2001.

Since the launch of Enbrel, Immunex¿s stock has climbed steadily, doubling from $70.625 to $143.25. Sheffery places the credit with one factor.

¿What¿s been responsible for Immunex¿s stock increase? It¿s been Enbrel, Enbrel, Enbrel,¿ he said. ¿It¿s just that simple. I credit their management for managing Wall Street¿s expectations for the drug. But it became evident in April that Enbrel was going to be a breakthrough product.¿

However, Sheffery noted that every person diagnosed with RA probably won¿t start with Enbrel. Physicians, he said, are more likely to start with the NSAIDs that they know, especially because Enbrel is expensive. The drug is priced at $110 per vial, and the cost per patient per year at two vials per week comes to $11,440.

Immunex also disclosed that the label for Enbrel had been changed. The label always advised physicians that patients with active infections should stop Enbrel therapy until the infection had cleared. The new labeling says patients shouldn¿t start Enbrel therapy if they have an active infection.

Warner said an infection ¿has always been a contraindication for treatment with Enbrel. We did find that some doctors were starting Enbrel in patients with infections. The label has been changed to reflect that.¿ n