Tocagen Inc. (Tocagen) is a clinical-stage, cancer-selective gene therapy company. The Company is focused on developing product candidates designed to activate a patientâ€™s immune system against their own cancer. Its cancer-selective gene therapy platform is built on retroviral replicating vectors (RRVs), which are designed to selectively deliver therapeutic genes into the deoxyribonucleic acid (DNA) of cancer cells. Its lead product candidates are vocimagene amiretrorepvec (Toca 511) and flucytosine extended release (Toca FC). Toca 511 is an investigational injectable retroviral replicating vector (RRV) that encodes a prodrug activator enzyme, cytosine deaminase (CD). Toca FC is an investigational extended-release version of 5-fluorocytosine (5-FC), a prodrug that is inactive as an anti-cancer drug. As of February, 2017, Tocagen has completed enrollment of the Phase II portion with 187 patients.