Together, the companies will develop and commercialize ladiratuzumab vedotin, an investigational ADC targeting LIV-1, which is in phase II clinical trials for breast cancer and other solid tumors. Joint development will evaluate the ADC as a monotherapy and in combination with Keytruda, Merck's anti-PD-1 therapy, in triple-negative breast cancer and other solid tumors.

Seattle Genetics will receive a $600 million upfront payment and Merck will make a $1 billion equity investment in 5 million shares of Seattle Genetics at a price of $200 per share. Seattle Genetics will also be eligible for progress-dependent milestone payments of up to $2.6 billion.

Merck will commercialize tucatinib (Tukysa), a small-molecule tyrosine kinase inhibitor for the treatment of HER2-positive cancers, in Asia, the Middle East, and Latin America and other regions outside of the U.S., Canada, and Europe. Seattle Genetics will receive an upfront payment of $125 million from Merck and is eligible for progress-dependent milestones of up to $65 million. Merck will also co-fund global development efforts, including several ongoing and planned clinical trials. Seattle Genetics will continue to lead these projects.