Emerging drug delivery systems to alter tumor immunosuppressive microenvironment: Overcoming the challenges in immunotherapy for glioblastoma.

Glioblastoma (GBM) is a highly proliferative, lethal cancer of the brain. The median survival at eight months is ca. 6.8%. Resistance towards the anti-glioblastoma drug temozolomide (TMZ), recurrence of cancer cells, blood-tumor brain barrier (BTBB), blood-brain barrier (BBB), and tumor immunosuppression are major challenges in treating GBM. Drug delivery systems employing TMZ and other anti-cancer drugs and combination therapy (temozolomide with immunotherapeutics) are under pre-clinical and clinical studies, respectively. Immunotherapeutics have emerged as a dominant mechanism to silence tumor development and dissemination. Paradoxically, immunotherapy has witnessed failure in treating GBM. This is due to the unique immunosuppressive microenvironment in GBM. Future immunotherapeutics with inherent tumor environment-modulating properties have to be identified. In this review, we discuss recent delivery systems and devices engineered to deliver immunotherapeutics with the ability to alter/silence tumor immune suppression.