Cbl-b is a negative regulator of immune cell activation and has been described as a “master checkpoint” in immune function. Disrupting Cbl-b expression by silencing the Cbl-b gene enhances T cell and NK cell activity and results in reduced tumor growth in animal models. Blocking the Cbl-b function thereby activates both adaptive (T cells) and innate (NK cells) anti-tumor mechanisms, leading to more effective tumor destruction.

APN401 and INV441 are autologous cell therapies designed to inhibit the immune checkpoint Cbl-b using RNAi technology to enhance the immune response in cancer patients. Additionally, they benefit from repeated dosing of freshly modified cells, reducing immune escape of cancer cells.

Cbl-b-silenced PBMCs show a clear increase in proliferation and production of certain cytokines such as interferon gamma (IFN-γ) and interleukin 2 (IL-2) in response to stimulation. Importantly, neither proliferation nor cytokine production are induced in unstimulated T cells, indicating that Cbl-b silencing enhances T cell responses only in the context of antigen stimulation. This approach is superior to generalized systemic activation of all lymphocytes or to systemic administration of cytokines, which are often associated with severe toxicity and may also have negative immunoregulatory effects. Specifically, Cbl-b deficiency enhances anti-tumor activity of T cells and NK cells in vitro, resulting in: enhanced expression of inflammatory cytokines and activation markers when stimulated via the T cell receptor (TCR); enhanced proliferation and anti-tumor cell cytotoxicity; resistance to transforming growth factor beta (TGF-β)-mediated immune suppression (T cells); and increased activation of NK cells upon cytokine stimulation or tumor cell contact.