**3. Preclinical models**

**Table 2.** Anti-cancer drugs in colorectal clinical trials. This table gives an overview of the main colorectal cancer thera‐ pies being currently evaluated in clinical trials. Drugs are presented sorted by type, i.e. small molecule or biologics. For each compound, the pathway target and clinical status is provided. Source: National Cancer Institute database, 2012 and the clinical database of the *Journal of Gene Medicine* (http://www.wiley.com/legacy/wileychi/genmed/clinical).

Oncolytic viral therapy represents an appealing alternative therapeutic strategy for the treat‐ ment of CRC, both as single agent or in combination with existing clinical regimens. Onco‐ lytic viruses, like the vaccinia virus (a virus previously used for worldwide vaccination against smallpox), have the property to selectively infect and destroy tumor cells with limit‐ ed or no toxicity to normal tissues. These viruses efficiently replicate in tumor tissue, cause

*2.3.5. Unconventional approaches*

442 Drug Discovery
