A strategy in the treatment of cancer by harnessing the immune system, called adoptive cell therapy, is to use an individual’s own immune cells (T cells) and genetically modify them to target them to kill the cancer. Our emerging clinical data demonstrates that these gene-modified T cells are very active in killing tumor cells initially, but they lose their ability to function within a few weeks. This experience points to the need to have a continuous source of gene-modified cells to maintain the ability to kill cancer cells. In this study, we hypothesize that gene-modified stem cells will allow a sustained production of active T cells with antitumor activity. Since there is a delay in the appearance of the T cells that come from stem cells to get out of the bone marrow and into the blood, we will give patients both gene-modified T cells for a first wave of antitumor activity and gene-modified stem cells which will provide a bridge until the stem cells have produced more T cells. The purpose of the current study is to give gene-modified T cells in combination with gene-modified stem cells to reprogram the immune system to recognize and kill cancer cells that have the NY-ESO-1 protein with sustained killing activity. The patient’s own white blood cells and stem cells from their blood are modified in the laboratory using genetic techniques to express a specific receptor against cancer cells. Gene modification of cells involves the transfer of foreign genetic material (DNA) into a cell, in this case the immune system cells and stem cells. This process will endow the recipient immune cells and descendants of the stem cells with the ability to eliminate cancer cells that express the cancer specific protein, NY-ESO-1. The specific receptor against cancer cells that will be transferred to the immune cells and stem cells is called NY-ESO-1 T cell receptor (or TCR). In this study, the gene-modified immune cells will be given in combination with the gene-modified stem cells.
To date, we have manufactured a batch of the lentiviral vector necessary to transfer the NY-ESO-1 TCR into stem cells and have demonstrated that this vector can gene-modify human stem cells. Preclinical safety studies are currently ongoing. We have demonstrated that when mouse stem cells are gene-modified with this lentiviral vector, the stem cells take up residence in the bone marrow and produce appropriate blood cells. There is no detrimental effect on the blood cells that are derived from the stem cells. In vitro assays have also been performed to assess whether the lentiviral vector could potentially transform cells. These studies are ongoing but interim data suggests that there the lentiviral vector has no transforming potential. A preclinical study is also ongoing in mice to assess the safety of combining the gene-modified T cells and stem cells in mice. In addition, a preclinical study was performed to demonstrate that the stem cells are able to be specifically eliminated using ganciclovir, which provides a safety feature in case there was a problem when translating this research to humans. The vector includes a suicide gene which we have shown can be used to kill cells if necessary.
Preparations are ongoing towards opening a clinical trial. The manufacturing process is being optimized, and clinical documents have been submitted to internal committees for review.