PathoGenesis Corp. later this year expects to file for FDA approval of its inhaled form of tobramycin for cystic fibrosis-related lung infections, following release of positive findings from two Phase III trials last week.

The drug, called TOBI, is a new formulation of the approved antibiotic, tobramycin, and is inhaled through a nebulizer to treat Pseudomonas aeruginosa infections. Cystic fibrosis patients currently receive tobramycin intravenously.

PathoGenesis officials said converting the antibiotic to an inhaled form allows for use of the infection-killing drug in higher concentrations and provides for easier administration.

PathoGenesis expects to file for FDA approval of TOBI in the second quarter of 1997 and plans to market the drug itself.

The company's stock (NASDAQ:PGNS) jumped 19 percent Thursday in anticipation of the Phase III trial results, which were released after the market closed. PathoGenesis shares continued their climb Friday ending the day at $30.25, up $5.25.

The two Phase III trials demonstrated TOBI achieved statistical significance, compared with placebo, for improving cystic fibrosis patients' lung function and reducing their hospital stays for treatment of infections. A total of 468 patients participated in the two studies.

Cystic fibrosis afflicts about 30,000 people in the U.S. and an almost equal number in Europe.

PathoGenesis officials have said TOBI may be used as a complementary treatment with South San Francisco-based Genentech Inc.'s Pulmozyme, an aerosol drug that breaks down thick mucous in the lungs of cystic fibrosis patients. The build-up of mucous fosters the spread of infection.

Genentech's Pulmozyme sales totaled $76 million in 1996. * Charles Craig