Background: We have developed an autologous T cell product directed to the EGFR variant III mutation via lentiviral transduction of a chimeric antigen receptor (CAR), and opened an IND. We have initiated a pilot study enrolling patients with recurrent EGFRvIII-positive glioblastoma (GBM). Methods: Patients with recurrent GBM have their tumors screened for the presence of the EGFRvIII mutation by a next-generation sequencing based assay. Eligible patients undergo leukapheresis for collection of autologous T cells, which are genetically modified ex vivo to express the EGFRvIII CAR, expanded, and then cryopreserved for infusion. Results: We report results on the nine patients we have treated. To date, we have found that infusion of 1-5x10⁸ CART-EGFRvIII cells is feasible to manufacture and infusion is safe, without evidence of off-tumor toxicity or cross-reactivity to wild type EGFR. No clinical or laboratory signs of systemic cytokine release syndrome have been observed, though elevations in serum IL-6 occur concurrently with CART-EGFRvIII expansion in the peripheral blood. One patient developed non-convulsive status epilepticus nine days after CART-EGFRvIII infusion, which resolved with standard treatment and anti-cytokine therapy. All patients have had significant expansion of CART-EGFRvIII cells between 7-10 days post-infusion, as measured by flow cytometry and quantitative PCR in peripheral blood samples. Five patients have undergone surgical resection of tumor between 6-120 days after infusion, and pathologic evaluation has demonstrated infiltration of activated CAR T cells, recruitment of new T cells (as assessed by next generation T cell receptor deep sequencing), and specific EGFRvIII target antigen loss in GBM cells in some cases. Conclusions: These findings provide evidence that CART-EGFRvIII cells are safe, without evidence of off-target toxicity or cytokine release syndrome, and are immunologically active. The data also suggest a mechanism of antigen editing by activated CART-EGFRvIII cells that track to specific EGFRvIII GBM cells. Clinical trial information: NCT02209376