A naturally occurring enterovirus with potential antitumor activity. Upon intratumoral administration, coxsackievirus A21 targets and binds to intracellular adhesion molecule 1 (ICAM-1) and decay acceleration factor (DAF), both cell surface molecules that are both overexpressed on certain malignant cells. After entering the cells, coxsackievirus A21 replicates in these cancer cells, thereby causing cancer cell lysis. This results in a reduction of tumor cell growth.