Reduction of immune inhibitory myeloid derived suppressor cells by low dose sunitinib combined with a cancer vaccine to provide therapeutic benefit to tumor-bearing mice.

e23084Background: Sunitinib is a receptor tyrosine kinase inhibitor (RTK) approved as a monotherapy for the treatment of advanced RCC, gastrointestinal stromal tumors and advanced pancreatic neuroendocrine tumors. At the approved doses, it inhibits angiogenesis in tumors and targets RTKs (PDGF receptor, VEGF receptor, KIT, FLT-3, and RET) involved in tumor cell growth. Sunitinib also has been shown in murine studies and patients, to exhibit immunomodulatory properties that reduce a heterogeneous population of cells termed myeloid derived suppressor cells (MDSCs) and restore the immune stimulatory Th1 cytokine profile of T cells. The approved anti-angiogenic sunitinib dosing regimens in RCC have a safety profile that is overall manageable with the most commonly reported sunitinib-related grade 3 adverse events including hypertension, fatigue, diarrhea and hand-foot syndrome. Although the tolerability of sunitinib as monotherapy was acceptable in advanced stage diseases, the drug’s side effect profile could...