Shares of San Diego-based Tocagen Inc. (NASDAQ:TOCA) fell 77.7% to 93 cents on Sept. 12, and further since, after its two-part immunotherapy for people with recurrent brain cancer failed to surpass standard of care on overall survival (OS), the primary endpoint of the company's phase III Toca 5 trial. Secondary endpoints in the registrational study were also missed, showing no meaningful difference between study arms.