Genentech Inc. and SmithKline Beecham Co. on Monday tried toput the best light on the results of the ISIS-3 trials comparingclot-busting drugs.
ISIS-3 researchers found no difference in the number of livessaved by an inexpensive, 30-year-old drug, streptokinase, andtwo new-generation thrombolytics: SmithKline's Eminase andduteplase, an unapproved form of tissue plasminogen activator(t-PA) produced by Burroughs Wellcome Co. The results wererevealed Saturday at the American College of Cardiologistsconvention in Atlanta.
Both SmithKline of Philadelphia, which helped fund ISIS-3, andGenentech of South San Francisco, Calif., disputed the design ofthe study, which concluded that mortality rates for all threedrugs were just over 10 percent.
Both companies downplayed the significance of the highernumber of cerebral hemorrhages found with Eminase (six per1,000) and duteplase (seven per 1,000) compared withstreptokinase (three per 1,000). Strokes were measured byphysician observation rather than by any objective measure, aSmithKline spokesman said.
SmithKline also said the administration of Eminase was delayedbecause of the double-blind nature of the study, thus possiblyreducing the efficacy of the drug. The company has spent about$200 million to develop the drug, which costs $1,700 a doseand has a 9 percent market share.
Although Genentech's Activase t-PA wasn't part of the study,the company has criticized the trial for administering heparin,an anti-coagulant, subcutaneously four hours after the start oftreatment. Genentech said that in data pooled from more than6,400 patients who received heparin intravenously at the sametime as t-PA, Activase had a mortality rate of 5.9 percent.
Biotechnology analysts interviewed on Monday didn't thinkISIS-3 would have a major impact on the use of Activase,which at $2,200 a dose has a 64 percent market share.
Streptokinase accounts for most of the rest of the thrombolyticmarket share.
"The choice of a thrombolytic drug is at this point an act offaith and a consequence of training," said David Stone, ananalyst at Cowen & Co. in Boston. Until a study shows adramatic difference among thrombolytics, that won't change,Stone said.
Linda Miller, a biotech analyst at PaineWebber in Boston,agreed with Genentech that ISIS-3 doesn't incorporate optimaluse of heparin with t-PA. "Physicians don't feel (ISIS-3)reflects their current practice," Miller said.
Genentech's stock (NYSE:GNE) closed down 88 cents on Mondayat $25.13. SmithKline (NYSE:SBH) fell 13 cents to $67.38.
-- Karen Bernstein BioWorld Staff
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