BOTHELL, Wash.--(BUSINESS WIRE)--Seattle Genetics, Inc. (Nasdaq:SGEN) announced today that it has initiated a phase Ib clinical trial of SGN-40 in combination with Rituxan® (rituximab) and Gemzar® (gemcitabine) for patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL), the most common type of non-Hodgkin lymphoma.