1195 Discovery of CBO421, a first-in-class drug Fc-conjugate (DFC), targeting CD73 in cancer by María Hernández, Simon Dohrmann, James Levin, Nicholas Dedeic, Amanda Almaguer, Doug Zuill, Elizabeth Abelovski, Rajvir Grewal, Joanne Fortier, Qiping Zhao, Karin Amundson, Madison Moniz, Hongyuan Chen, Dhanya Panicker, Thanh Lam, Thomas P Brady, Allen Borchardt, Jason N Cole, Leslie W Tari