KaloBios Pharmaceuticals Inc, of Palo Alto, California, a privately held company devoted to the discovery and development of therapeutic antibodies and proteins, announced that it has raised $20 million in its Series B round of financing. The funds will be used to build a clinical development team and to advance and optimize its two lead antibodies into clinical evaluation. One of these, KB002, is being developed for the treatment of rheumatoid arthritis and other autoimmune diseases. An early version of KB002 was in-licensed from the Melbourne (Australia) branch of the Ludwig Institute for Cancer Research (LICR), and KaloBios will use its proprietary antibody engineering, humanizing and expression technologies to optimize the antibody's pharmacologically important properties.

KB002 binds to and neutralizes an undisclosed protein target that appears to play a key role in establishing and managing the destructive disease process. In animal studies, blocking the function of this protein appears to prevent the induction of arthritis, and treatment of ongoing disease halts progression.

According to company sources, the antibody interferes with the mobilization of immune cells from bone marrow and their migration to the joints and inhibits the activation and proliferation of these cells in the joint where they can promote damage to bone and cartilage. KB002 does not target TNF-α or interleukin-1, and a review of the relevant scientific literature suggests that the antibody likely targets granulocyte macrophage colony stimulating factor (GM-CSF), a well-known proliferation and differentiation molecule necessary for the development of hemopoietic progenitor cells into granulocytes, macrophages, and dendritic cells.

More recently, GM-CSF has been implicated as a key cytokine in inflammatory joint disease. This role is evidenced by the suppression of arthritic disease in a collagen-induced animal model, observed when GM-CSF is blocked using either neutralizing antibodies (administered at the time of antigen challenge or after establishment of disease) or gene deletion. Kalobios plans to enter KB002 into human clinical trials by the end of 2005.