Corvas International Inc. said it granted Johnson & Johnson'sOrtho Diagnostics Inc. unit worldwide rights to manufactureand distribute prothrombin time (PT) clotting testsincorporating Corvas' recombinant tissue factor (rTF).

Introduced around 1935, PT tests are used to determine theblood clotting ability of patients. Using Corvas' rTF factor offersa more accurate and reproducible clotting times thantraditional tests, which employ thromboplastins derived fromanimal tissue to determine clotting time. Unlike the traditionaltests, rTF-based tests will not need to be recalibrated with eachbatch, said John E. Crawford, Corvas' executive vice presidentand chief financial officer.

Corvas' rTF-based test is also expected to address the need fora more accurate and finely tuned method of monitoring theincreasingly more common low-dose regimens of anti-coagulant therapy, the company said.

Under the agreement, Corvas (NASDAQ:CVAS) will produce rTFfor Ortho in return for licensing fees, manufacturing incomeand product royalties expected to total at least $1.5 millionthrough 1993. The agreement completes a co-developmentrelationship initiated in January 1991.

Corvas of San Diego holds an exclusive license to the in vitrodiagnostic uses of rTF. from The Scripps Research Institute ofLa Jolla, Calif., the company said. Scripps was granted a U.S.patent on May 5 on the gene encoding tissue factor and onmethods of preparing tissue factor.

PT tests comprise a $50 million worldwide market involvingabout 500 million tests to determine the status of a patient'sblood-clotting system before, during and after surgery, and tomonitor anti-coagulant therapy in heart attack and strokepatients.

"I'm hoping Ortho will get a premium, but it'll have to be inline" with the relatively low cost of existing tests,Crawford.said.

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