Seattle Genetics has a new agreement with Bayer HealthCare to jointly develop cancer-fighting drugs.

Bayer will pay fees of up to $20 million for worldwide rights to utilize Seattle Genetics’ auristatin-based antibody-drug conjugates technology.

Antibody-drug conjugates are designed to attack cancer tumor cells in a much more targeted way with the goal of lessening negative effects on healthy cells.

Bothell-based Seattle Genetics could also get up to about $500 million in potential milestone payments, along with royalties on worldwide net sales of any resulting products under the collaboration. Bayer is responsible for research, product development, manufacturing and commercialization of all products under the agreement.

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Shares of Seattle Genetics fell 20 cents, or 0.7 percent, to $29.70 at Tuesday’s close.