Merck & Company and Seattle Genetics have entered into an agreement for the joint development and subsequent commercialization of Ladiratuzumab Vedotin, a breast cancer drug. Under the terms of the deal, Merck will pay Seattle Genetics $600 million in advance and buy back 5 million shares for $1 billion. Seattle Genetics will also be entitled to interim payments of up to $2.6 billion at the development and sales stages of the drug.