A genetically engineered strain of Salmonella (TAPET-CD) has completed phase 1 clinical trials for patients with stage 4 metastatic cancer.[10]Listeria-based cancer vaccines are currently being produced and are undergoing many clinical trials.[11] Phase I trials of the Clostridium strain called Clostridium novyi (C. novyi-NT) for patients with treatment-refractory tumors or tumors that are unresponsive to treatment is currently underway.[12]