Genentech Buoyed by Drug Study : Biotechnology: Demand for its anti-clotting drug for heart attack victims is expected to grow after a clinical test underscores its effectiveness.

Genentech, one of the nation’s leading biotechnology firms, got a much-needed lift Friday when a massive study of heart attack victims showed that its expensive clot-busting drug--which accounts for a third of company sales--is more effective than a much-less-costly alternative in preventing deaths.

Analysts and doctors were nearly unanimous in predicting that the study, financed by South San Francisco-based Genentech, would result in more widespread use of the company’s Activase drug--also known as t-PA--in U.S. and European hospitals.

Sales of the drug had been flat since separate European studies in 1990 and ’91 showed Activase with insignificant advantages over other drugs that break up blood clots, particularly Streptokinase, a European drug that costs about $400 per dose, compared to $2,200 for Activase.

On Friday, some cardiologists continued to describe the Genentech drug’s advantage over Streptokinase as “slight” and “less than dramatic.”

Nevertheless, investors buoyed by the news pushed Genentech’s stock up $4.75 to close at $37.50 in heavy trading on the New York Stock Exchange.

“The results are extremely positive,” said Stu Weisbrod, biotechnology analyst with Merrill Lynch in New York. “It’s really going to expand the use of thrombolytics (clot busters) in the United States. Only 20% of heart attack victims get them in the U.S, compared to 40% in Europe. That’s going to go up.”

Positive but less enthusiastic was Dr. Valentin Fuster, professor of cardiology at Harvard Medical School, who said the drug appears to especially benefit elderly patients and those treated within four hours after heart attacks.

“One must now analyze the data to see what patients really have the maximum benefit and come up with an answer whether there are a number of patients in which the benefit is borderline and a cheaper thrombolytic approach is called for,” Fuster said.

James T. Willerson, a cardiologist, professor and chairman of internal medicine at University of Texas Medical School at Houston, said: “Data shows that t-PA and heparin are slightly superior to Streptokinase. . . . The issue about whether a slight difference is cost-effective will have to be studied further.”

The study was welcome news for the entire biotechnology industry--a highly cyclical industry that finds itself in a periodic trough. Always vulnerable to the success or failure of individual products, biotechnology stocks were pummeled this year by the failure of highly touted antisepsis drugs and by President Clinton’s criticism of rapidly increasing drug prices.

The stock price decline has hurt biotechnology companies’ ability to raise capital and form joint ventures to finance costly, long-term product development.

Friday’s results delighted executives at Genentech, which has been through ups and downs of its own. Chief Executive Kirk Raab said that while he doesn’t expect “every physician in every hospital to embrace these studies,” there is “no doubt” that Activase is cost-effective.

The company introduced Activase in 1987 amid expectations that it would generate $1 billion in sales as a therapy for heart attack patients.

But after peaking at $210 million in 1990, Activase sales were about $180 million of Genentech’s $544 million in revenue last year.

Streptokinase, which is made by Hoechst of Germany and Astra and Kabi Farmacia of Sweden, claims most of the remainder.

Among biotech concerns, Genentech is second in revenue to Thousand Oaks-based Amgen.