An adenovirus comprising an E1A polypeptide comprising one or more modifications and comprising an E4orf6/7 polypeptide comprising one or more modifications is described. Compositions and kits comprising the modified adenoviruses are also described. Further described is a method of treating a proliferative disorder in a subject comprising administering to the subject an adenovirus comprising the E1A polypeptide comprising one or more modifications and comprising the E4orf6/7 polypeptide comprising one or more modifications.
