In combination with conventional therapies (e.g.,
targeted therapy,
chemotherapy, and
angiogenesis inhibitors etc.), immunotherapies targeting checkpoint molecules have shown promise in the treatment of
solid or liquid tumors. However, apoptotic regulatory T cells (Treg) induced by such therapies often become more suppressive in the
tumor microenvironment (TME), through increased generation of
adenosine tightly controlled by ectonucleotidases, viz. CD39 and CD73. CD39 / ENTPD1, a novel checkpoint molecule, is highly expressed and activated on the
tumor vasculature and infiltrating immune cells, promoting
tumor growth. Deletion or
blockade of CD39 enhances anti-tumor activity by augmenting anti-tumor immune responses and inhibiting
tumor angiogenesis. The present invention is based at least in part on the development of anti-CD39 antibodies which mediate CD39 downregulation on immune cells, such as T-cells with markers of T-
cell exhaustion, and the demonstrated utility of these antibodies in blocking
tumor growth with minimal side effects in pre-clinical models.