By Mary Welch

Schering-Plough Corp. filed a biologics license application for PEG-Intron powder for injection for the treatment of chronic hepatitis C.

PEG-Intron is a modified form of Schering-Plough's billion dollar drug, Intron A (interferon alfa-2b recombinant), that uses Enzon Inc. technology in order to have longer-acting properties.

"We expect Intron A will have 1999 sales of $1 billion, and PEG-Intron is substantially better," said Lesley Marino, an analyst with BancBoston Robertson Stephens Inc., of New York. "Not only is it more convenient - once-a-week treatment vs. three times a week - but we think there's a good chance that it is more effective. This clearly has blockbuster potential with sales of over $500 million, and Enzon is getting some nice royalties. PEG-Intron will definitely cannibalize Intron A sales."

In fact, Piscataway, N.J.-based Enzon will receive between 7 percent and 7.5 percent of all worldwide sales of PEG-Intron, said Kenneth Zuerblis, Enzon's vice president of finance and chief financial officer. "If you use the numbers given by the analysts, you can see that this is a very large product.

"First," he said, "it is expected that the number of hepatitis C patients will grow substantially in the next few years. It's estimated that there are about 4 million Americans infected with hepatitis C but only 400,000 to 500,000 being treated. That's because it has a long dormant phase, like AIDS. In addition, we're going after all the indications approved for Intron-A, and some other applications as well."

The BLA, which was filed last month, is for an indication of chronic hepatitis C in patients 18 years or older with compensated liver disease. The product is in Phase III trials for malignant melanoma and chronic myelogenous leukemia as well as in early stage trials for other solid tumors and forms of leukemia. It also is in Phase III trials as combination therapy with Rebetol (ribavirin) for hepatitis C.

Madison, N.J.-based Schering-Plough requested fast-track status. The filing prompted a $1 million milestone to Enzon. Another $2 million milestone is due upon approval. Schering-Plough submitted a centralized marketing authorization application for PEG-Intron in Europe in November.

"Our partnership goes back to 1990," Zuerblis said. "There's been a lot of changes over the years."

Intron A, marketed in more than 80 countries for 16 major anticancer and antiviral indications, was licensed to Schering-Plough from Biogen Inc., of Cambridge, Mass. Alpha interferon was the subject of a patent infringement lawsuit involving Biogen, Schering-Plough, F. Hoffmann-La Roche Ltd., of Basel, Switzerland, and Genentech Inc., of South San Francisco. The litigation was settled in 1998. (See BioWorld Today, June 22, 1998, p. 1.)

Intron A was modified using Enzon's Pegnology drug-delivery technology that employs polyethylene glycol to coat the protein, which helps prevent antibodies from binding to the protein molecule and reduces immunogenic reactions. As a result the drug is able to remain in the bloodstream longer.

Enzon's stock (NASDAQ:ENZN) closed Wednesday at $41.125, down 37.5 cents.