EMERYVILLE, Calif. -- Cetus Corp. said Thursday that it againsued E. I. du Pont de Nemours, this time alleging that Du Pontinfringed on Cetus' newest patent on PCR (polymerase chainreaction) technology.

Cetus (NASDAQ:CTUS) asked the U.S. District Court in SanFrancisco to stop Du Pont's sales of PCR-related products. Cetuscontends that Du Pont's products induce its customers toinfringe Cetus' U.S.P. 4,964,188, issued last Oct. 23, for the useof thermostable enzymes to carry out PCR.

The patent describes "the most commercially useful method ofdoing PCR," said Peter Staple, Cetus' vice president of legalaffairs.

Cetus and Du Pont are scheduled for a trial next Monday in thesame U.S. district court to decide the validity of two prior CetusPCR patents. Du Pont contends in that suit that Cetus' U.S.Patents 4,683,195 and 4,683,202 are invalid becausedescriptions of PCR technology were published prior to Cetus'claims

U.S. District Court Judge Marilyn Hall Patel is expected to ruleon Cetus' request for a preliminary injunction soon aftercompleting the patent validity trial, which she will also hear,Staple said.

Dr. George Frank, Du Pont's senior counsel, said that Cetus'newest suit was anticipated. Cetus last summer alleged that DuPont infringed the two patents that are the subject of nextweek's patent validity trial.

Cetus' stock closed Thursday at $7.75 a share, down 38 cents.Investors probably would not react strongly to Thursday'sannouncement of yet another PCR suit, said Denise Gilbert, ananalyst for County NatWest in San Francisco.

She predicted that Cetus will win the patent validity trial, butthat even a court victory is not likely to dispel investors'concerns about Cetus' overall business plans. Hoffmann-LaRoche Inc., the exclusive licensee for human diagnostic uses ofPCR, does not expect the technology to produce significantrevenues for at least two to three years, Gilbert said.

Cetus' Staple acknowledged that entry into the diagnosticmarketplace is a ways off. However, Cetus sold $26 million ofPCR-related products for research purposes during the mostrecent fiscal year, he said.

Even if Cetus wins the PCR wars, it would still face competitionfrom rival technologies such as a gene amplification technologybased on a different enzyme that is being developed byBiotechnica Inc. of Cambridge, Mass., and Abbott Laboratoriesof Abbott Park, Ill.

(For further background on these cases, keyword searchIndustry Library for 110190DUPONT, 103090CTUS,102690CTUS, 082890CTUS, 061590PCR, 041690PCR,030690PCR and 021590PCR.)

-- Carol Talkington Verser, Ph.D. Special to BioWorld

(c) 1997 American Health Consultants. All rights reserved.

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