Promising Results for Alpha Particle Radiation Therapy

Researchers have found that a radioimmunoconjugate containing a highly specific monoclonal antibody labeled with the alpha-emitting radionuclide thorium-227 (227Th) was highly effective in killing cancer cells both in vivo and in vitro.

Investigators from the cancer therapeutics company Algeta ASA (Oslo, Norway) and two academic institutions, the Norwegian Radium Hospital (Oslo, NOrway) and the Fred Hutchison Cancer Research Center (Seattle, WA, USA), linked thorium-227 to the antibody rituximab, a humanized monoclonal antibody that selectively binds to CD20, a protein found on the surface of normal and malignant B cells. Rituximab is used to reduce the numbers of circulating B cells in patients who have B-cell non-Hodgkin's lymphoma (NHL).

A study published in the May 29, 2007, issue of the journal Blood reported that 227Th-rituximab killed lymphoma cells in vitro at low dosages in the Bq /ml range. A single injection of 227Th-rituximab induced complete tumor regression in up to 60% of nude mice bearing macroscopic human B-lymphoma xenografts at Bq/g levels without apparent toxicity. Therapy with 227Th-rituximab was significantly more effective than the control radioimmunoconjugate 227Th-trastuzumab, which does not bind CD20, and the standard beta-emitting radioimmunoconjugate for CD20-positive lymphoma, 90Y-tiuxetan-ibritumomab.

Dr. Thomas Ramdahl, president and CEO of Algeta said, "This important paper provides more evidence of the potential of alpha particle-based molecules for targeted cancer therapy. We are working with collaborators to validate our TH-1 technology and are looking for further partnering opportunities with companies that have interesting cancer-targeting molecules that would benefit from this approach.”


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Algeta
Norwegian Radium Hospital