As per the terms of the agreement, Amgen has the option for the exclusive worldwide license of XmAb 5871 following the completion of a pre-defined Phase 2 study.
However, Xencor will lead all clinical development until that time.
Amgen is responsible to pay an up-front and early development milestone payment to Xencor and will also pay tiered royalties on future sales of XmAb5871 to Xencor.
If Amgen does exercise its option, Amgen will assume responsibility for future development and Xencor will receive $75m as an option-exercise fee which, combined with the up-front and early development milestones.
Additionally, Xencor could receive up to an additional $425m in clinical, regulatory and commercialization milestone payments.
Xencor CEO Bassil Dahiyat said that they expect that XmAb5871 will soon become the fifth XmAb-engineered antibody in clinical development.
"This program is a testament to the progress we’ve made expanding the XmAb platform into autoimmune disease with our CD32b technology, which is at the core of the XmAb5871 compound," Dahiyat said.