WT1 Antigen

Our lead product candidate, galinpepimut-S (GPS), is a WT1-targeting cancer immunotherapeutic licensed from Memorial Sloan Kettering Cancer Center, which we are developing as a monotherapy and in combination with other therapeutic agents to treat different types of cancers that result from uninhibited tumor cell growth.

The WT1 protein is one of the most widely expressed cancer proteins in multiple malignancies. In 2009, the National Cancer Institute ranked the WT1 protein as a top priority for immunotherapy.

WT1 is a protein that resides in the cell’s nucleus and participates in the process of cancer formation and progression. In 20 or more cancer types, WT1 becomes detectable in at least 50% of tumor pathology specimens in the cells of these cancers. WT1 appears in large amounts, or becomes “overexpressed,” in numerous hematological malignancies, including acute myeloid leukemia (AML) and multiple myeloma (MM) as well as in many solid malignancies such as malignant pleural mesothelioma (MPM), ovarian cancer, and small cell lung cancer (SCLC).

We believe that GPS targets malignancies and tumors characterized by an overexpression of the WT1 protein through direct activation of the patient’s immune system specifically and solely against the WT1 protein. A healthy immune system is designed to identify foreign or abnormal proteins expressed on tumor cells; however, this process is often defective in people with cancer. T cells are involved in both sensing and killing abnormal cells, in addition to coordinating the activation of other cells in an immune response. T cells can be classified into two major subsets: CD4 cells and CD8 cells. CD8 cells, known as killer T cells, recognize, bind to, and kill target cells, including cancer cells. CD4 cells, known as helper T cells, are critical to providing the signals necessary for sustained CD8 cell responses and are also capable of direct anti-tumor activity.

Typically, cancer patients harboring WT1-positive malignancies have very few or no T cells specifically reactive or responsive to, and therefore activated by, WT1. GPS is designed to elicit both CD4 and CD8 cell immune responses. GPS is designed to activate CD8 cells which transform into cytotoxic T-lymphocytes (CTLs) that could attack and kill up to 10-20 WT1-positive cancer cells. Eventually, the CD4 cells could establish immunologic memory against a WT1-expressing cancer, which then are able to activate CTLs and B cells. These B-cells helped by the helper T cells produce antibodies to specific WT1 epitopes. This combination of actions initiates the process of immunity against WT1, potentially resulting in an anti-cancer effect.

We are currently developing GPS as a monotherapy and in combination with checkpoint inhibitors. For more information on our development program for GPS, please view our pipeline.