Pembrolizumab and a Vaccine (ATL-DC) for the Treatment of Surgically Accessible Recurrent Glioblastoma

Inclusion Criteria: * Participants with histologically confirmed diagnosis of surgically accessible recurrent/progressive glioblastoma will be enrolled in this study * Be at first or second relapse (Note: relapse is defined as progression following initial therapy, i.e., radiation +/- chemotherapy. For participants who had prior therapy for a low-grade glioma, the surgical diagnosis of a high-grade glioma will be considered the first relapse) * Must be undergoing surgery that is clinically indicated, and eligible for resection with the expectation that the surgeon is able to resect at least 2 gram of tumor for lysate and research with low risk of inducing neurological injury * A male participant must agree to use a contraception during the treatment period and for at least 120 days after the last dose of study treatment and refrain from donating sperm during this period * A female participant who has childbearing potential must have negative urine or serum pregnancy test 72 hrs prior to the first dose and be willing to use adequate method of contraception for course of study and 120 days after last dose * The participant (or legally acceptable representative if applicable) provides written informed consent for the trial * Have unequivocal evidence for contrast enhancing tumor progression by RANO criteria based on MRI scan within 14 days prior to randomization * Have a minimum tumor size of 2 x 2 cm\^2 based on MRI scan prior to surgery * An interval of the following duration…