409 Development of ex vivo precision gene engineered B cell medicines that produce highly active and sustained levels of transgenic anti-tumor biologics by Richard A Morgan, David J Rawlings, Richard G James, Jasmine N Edelstein, Tyler F Hill, Michael D Leiken, Katherine M Molloy, Glory Adekanye, Caroline Bullock, Adam S Lazorchak, Ken-Edwin Aryee, Sean P Arlauckas