longer whichever lives half preceding investigational drug days dose study investigational whichever half longer lives product agent prior days study half lives agents investigational prior days treatment therapy study drug taken half investigational lives days shorter whichever agents minimum drug immunostimulatory whichever lives half agents systemic shorter treatment drug weeks shorter whichever half lives therapy weeks prior investigational chemotherapy treatment shorter half lives whichever days investigational dose drug study minimum whichever longer half lives drug investigational study days dose weeks antibody monoclonal lives half elapsed dose prior antibodies treatment days