A Phase I ascending dose study of initial Toca 511, followed by cycles of oral Toca FC, demonstrated a median overall survival of 14.3 months after the removal of brain tumors from 24 patients.

Developed by Tocagen, Toca 511 (vocimagene amiretrorepvec), administered at the time of tumor removal, and Toca FC (extended-release 5-fluorocytosine) demonstrated a favorable safety profile, and was tolerated well by patients with recurrent glioblastoma or anaplastic astrocytoma. Updated data showed that over 20 percent of patients demonstrated an overall response, with median duration of response lasting 20.7 months. Five patients showed stable disease.

Toca 511 and Toca FC are currently in the Phase II portion of a Phase II/III study. Toca 511 is an investigational injectable retroviral replicating vector that encodes a prodrug activator enzyme in cancer cells, cytosine deaminase, which is not found in humans. According to Tocagen, Toca FC is inactive until converted by the CD enzyme into an anticancer drug at high concentrations within the cancer cells infected by Toca 511.