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Early Clinical Trial to Test Leukemia Antibody Safety

Chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia cells, stained purple (California Institute for Regenerative Medicine)

17 September 2014. An early stage clinical trial at University of California in San Diego is testing the safety of an antibody that in lab animals decreases the number of chronic lymphocytic leukemia cells, the most common form of leukemia among adults. The study is led by UC-San Diego medical school professor Thomas Kipps, who is also director of the Chronic Lymphocytic Leukemia Research Consortium.

Chronic lymphocytic leukemia is a disorder of the blood and bone marrow, where the bone marrow makes too many blood stem cells that fail to mature into healthy white blood cells. The overabundance of these leukemia cells crowd out the healthy blood cells, including other white blood cells that support the immune system as well as platelets and red blood cells. The disease causes individuals, primarily adults, to develop infections, anemia, and easier bleeding.

Kipps and colleagues at UC-San Diego designed an antibody called cirmtuzumab that targets a protein known as ROR1 found on the surface of chronic lymphocytic leukemia cells. The UC-San Diego team developed cirmtuzumab using antibody drug conjugate techniques devised by biotechnology company Concortis Biosystems. In June, Concortis Biosystems was acquired by Sorrento Therapeutics, also in San Diego, another biotechnology company designing antibodies as cancer therapies.

ROR1, the target for cirmtuzumab, is a protein that appears to occur only in cancer cells, not in healthy cells, thus the researchers believe this protein acts as a reliable biomarker of chronic lymphocytic leukemia. Previous research by Kipps’s lab found ROR1 to occur in a range of solid-tumor and blood-related cancers, where it combines with cancer-causing mutations early in the process to encourage the proliferation of cancer cells, as well as the spread of cancer or metastasizing to other parts of the body.

In tests of cirmtuzumab with lab cultures and animals, the UC-San Diego researchers found the antibody to target cells with ROR1 proteins, i.e. cancer cells, while avoiding healthy cells without ROR1. The findings also showed cirmtuzumab injections kill many more human chronic lymphocytic leukemia cells with ROR1 in lab animals than those not getting the injections, while cells without ROR1 proteins are unaffected. In addition, the results show the antibody has potential for killing pancreas and breast cancer cells expressing the ROR1 protein.

The clinical trial is enrolling 56 patients with chronic lymphocytic leukemia who have relapsed or advanced forms of the disease that do not respond to approved treatments. The patients will receive intravenous doses of cirmtuzumab at various levels, where clinicians will be watching for adverse reactions and overall tolerability of the treatments, although signs of clinical benefits to patients will also be noted. The treatments will be given every 14 days for 8 weeks.

The trial is expected to be completed in August 2016.

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