Shares of Genocea Biosciences Inc. surged 101% in premarket trade Monday after the biotech announced promising data from an early-stage clinical trial of its lead drug candidate, a personalized cancer vaccine. Genocea's vaccine, called GEN-009, uses neoantigens -- antigens corresponding to tumor mutations that a patient's immune system sees as foreign to the body -- to prime the immune system to find and kill tumors. The company is currently running a Phase 1/2 clinical trial to evaluate the vaccine's safety and efficacy. So far, immune-response data is available for five patients, and the therapy induced T-cell responses to 91% of the vaccine neoantigens given to the patients, according to the company. Also, 47% of the neoantigens were able to elicit ex vivo CD8+ T-cell responses, the company said. Shares of Genocea have gained 144% in the year to date through Friday. The S&P 500 has gained 9.8%.