TRU-016 Produces Significant Anti-Tumor Activity and Long-Term Tumor Regression in Pre-Clinical Studies

SEATTLE, WA, USA | June 2, 2008 | Trubion Pharmaceuticals Inc. (Nasdaq: TRBN) today announced presentation of positive pre-clinical data showing that Trubion’s TRU-016 has potent anti-tumor activity and induces significant long-term tumor eradication in a human tumor xenograft model in which rituximab failed to induce durable responses. TRU-016 is Trubion’s proprietary CD37-targeted therapy in development for B-cell malignancies such as chronic lymphocytic leukemia (CLL) and non-Hodgkin’s lymphoma (NHL).

ASCO Abstract 3074

TRU-016, a small modular immunopharmaceutical (SMIPTM) candidate, targets the CD37 antigen on human B cells. Data from both in vivo and in vitro studies presented at the American Society of Clinical Oncology (ASCO) 2008 Annual Meeting showed TRU-016 has potent anti-tumor activity and induces significant long-term tumor eradication in a human tumor xenograft model in which rituximab failed to induce durable responses. Moreover, TRU-016 treatment produced anti-tumor activity that resulted in increased survival and a significant delay in tumor growth in NHL xenografts.

These data were presented during a poster session at the ASCO Annual Meeting on June 1, 2008, from 2-4 p.m. CDT. The poster is available on the investor section of Trubion’s Web site: http://investors.trubion.com/events.cfm.

"Data from this study, combined with data from previous studies, reinforce our belief that TRU-016’s novel mechanism of action may provide patients with a potent new therapeutic option for the treatment of B-cell malignancies," said Peter Thompson, M.D., FACP, president, chief executive officer and chairman of Trubion. "TRU-016 represents a first-in-class product opportunity with an exciting, differentiated pre-clinical profile. The demonstrated ability of TRU-016 to kill tumor cells through powerful apoptotic signaling as well as potent ADCC-mediated activity, combined with its synergy with chemotherapies and anti-CD20 therapies, adds to our confidence that this drug, either alone or in combination with other effective therapies, may offer meaningful benefits to patients with these diseases. We look forward to the results of our ongoing Phase 1/2 clinical trial currently evaluating TRU-016 in CLL patients."

About Trubion

Trubion is a biopharmaceutical company that is creating a pipeline of novel protein therapeutic product candidates to treat autoimmune and inflammatory diseases and cancer. The company’s mission is to develop a variety of first-in-class and best-in-class product candidates, customized for optimal safety, efficacy, and convenience that it believes may offer improved patient experiences. Trubion’s current product candidates are novel single- chain protein, or SMIP(TM), therapeutics, and are designed using its custom drug assembly technology. Trubion’s product pipeline includes CD20-directed candidates such as TRU-015 and SBI-087 for autoimmune and inflammatory diseases, developed under the company’s Wyeth collaboration. Trubion’s product pipeline also includes Trubion’s proprietary product candidate, TRU-016, a novel CD37-targeted therapy for the treatment of B-cell malignancies that is currently in Phase 1/2 clinical evaluation. In addition to Trubion’s current product candidates, the company is also developing additional alliance and proprietary product candidates that build on its product development experience. More information is available in the investors section of Trubion’s website: investors.trubion.com.

SOURCE: Trubion Pharmaceuticals Inc.