Strong T-cell costimulation can reactivate tumor antigen-specific T cells in late-stage metastasized colorectal carcinoma patients: Results from a phase I clinical study

T-cell costimulation is necessary to induce a response of naive T cells. Whether T-cell costimulation can also cause reactivation of unreactive, possibly anergized memory T cells (MTCs) from late-stage cancer patients is unknown. To investigate this question, we developed a bispecific anti-CD28 fusion protein (bsHN-CD28) which can easily be attached to the vaccine ATV-NDV. This virus-modified autologous tumor cell vaccine has already shown effectivity in colon cancer patients following resection of liver metastases. In this phase I clinical study, 14 colorectal carcinoma (CRC) patients with late-stage disease which could not be operated anymore with curative intent were treated with the vaccine ATV-NDV to which bsHN-CD28 was attached. No severe adverse events were recorded. All patients showed an immunological response of tumor-reactive T cells, at least once during the course of five vaccinations. Also, we demonstrate a dose-response relationship with the costimulatory molecule added to the vaccine. A partial response of metastases was documented in four patients. The study suggests that the three-component vaccine is safe and can reactivate possibly anergized T cells from a chronic disease like advanced-stage cancer.