Pembrolizumab +/- Bevacizumab for Recurrent GBM

Pembrolizumab (MK-3475) is a humanized monoclonal antibody. An antibody is a common type of protein made in the body in response to a foreign substance. Antibodies attack foreign substances and protect against infection. Antibodies can also be produced in the laboratory for use in treating patients, an antibody that is made in the lab is also known as a humanized monoclonal antibody. There are now several approved antibodies for the therapy of cancer and other disease. Pembrolizumab (MK-3475) has been studied in lab experiments and in other types of cancer. Information from these studies suggests that Pembrolizumab (MK-3475) may be beneficial in your type of cancer. Bevacizumab, also known as Avastin, is approved by the FDA for treating recurrent GBM. Bevacizumab is an anti-angiogenic medicine, which means it blocks blood vessels from forming that could supply the tumor with nutrients and oxygen. There is a safety lead-in to evaluate pembrolizumab in combination of with bevacizumab (cohort A) expected to enroll up to 18 participants. Three dose levels (DL) are evaluated for pembrolizumab administered at 200 mg (flat dosing) under various dose intervals: every 3 (DL 0), 4 (DL -1) or 6 (DL -2) weeks. A standard 3+3 design is used starting at DL 0. De-escalation may occur depending on observation of dose-limiting toxicity (DLT). At least 6 participants will be evaluated for DLT at DL 0. The Phase II study randomizes participants to cohort A: pembrolizumab (using the MTD determined in the safety lead-in) and bevacizumab or cohort B: pembrolizumab monotherapy (using the MTD determined in the safety lead-in). Accrual goals are established for each cohort: A n=50 and B n=30 participants. The two cohorts are evaluated independently against a historical control and not compared. All participants treated at the safety lead-in established MTD dose level will be rolled into the Phase II cohort.