Tocagen Plunges Following Phase III Flop of Brain Cancer Drug

Shares of San Diego-based Tocagen have plunged more than 82% in premarket trading after the company announced its Phase III brain cancer treatment failed to achieve its primary and secondary endpoints.

Tocagen said the late-stage Toca 5 trial evaluating Toca 511 & Toca FC in patients with recurrent high-grade glioma undergoing resection missed its overall survival endpoint compared to standard of care treatment. The company product provided a median of 11.1 months OS compared to 12.2 months for standard of care. Additionally, Tocagen said the Toca 511 & Toca FC treatment did not show a meaningful difference in secondary endpoints compared to standard-of-care.

Tocagen said it will conduct additional analysis of the trial data and present the results at an upcoming medical conference.

Marty Duvall, Tocagen’s chief executive officer, expressed his disappointment at the trial results. Duvall said recurrent brain cancer remains a high unmet medical need and patients with this diagnosis have few treatment options. Duvall said the company’s analysis of the trial data will include molecular analyses and pre-planned subgroups. He also noted that the company will be conducting an “operational review.” That phrase suggests the possibility that there could be some layoffs in the near future, or that some assets could be dumped to focus resources on other assets. Duvall went on to thank the support from patients, employees and others who have been “been committed to the rigorous study of Toca 511 & Toca FC in the Toca 5 trial."

Tocagen's lead product candidate is a two-part cancer-selective immunotherapy that includes an investigational biologic, which is Toca 511, and an investigational small molecule, Toca FC. According to company data, Toca 511 is a retroviral replicating vector that selectively infects cancer cells and delivers a gene for the enzyme, cytosine deaminase (CD). Through this targeted delivery, only infected cancer cells carry the CD gene and produce CD. Toca FC is an orally administered prodrug, 5-fluorocytosine (5-FC), which is converted into an anti-cancer drug, 5-fluorouracil (5-FU), when it encounters CD. 5-FU kills cancer cells and immune-suppressive myeloid cells resulting in anti-cancer immune activation and subsequent tumor killing, according to the company.

Last month, the company announced its intentions to submit a draft protocol to the U.S. Food and Drug Administration for a planned Phase II/III trial of Toca 511 & Toca FC in patients with newly diagnosed glioblastoma.

As of June 30, the company had $68.3 million in cash, cash equivalents and marketable securities, according to its most recent quarterly report. Share prices had fallen to 72 cents in premarket trading from Wednesday’s close of $4.18.