As the treatment of cancers has moved toward an increasing emphasis on the role the immune system can play in fighting tumors, a range of new ways to enlist and train the immune system have emerged. Candel Therapeutics is developing oncolytic viral immunotherapies, which it says combines anti-tumor activity while also stimulating the immune system. We spoke to Paul Peter Tak, president and CEO of Candel Therapeutics, oncolytic viral immunotherapies, how they work, and why they may be able to bring benefits to the treatment of a range of solid tumors.