Trubion Pharmaceuticals Inc. Says Pfizer Inc. to Stop Development of Arthritis Drug, TRU-015

SEATTLE, June 14 /PRNewswire-FirstCall/ -- Trubion Pharmaceuticals, Inc. today announced Pfizer's decision to discontinue development of TRU-015 (PF-05212374), an investigational drug in Phase 2 evaluation for the treatment of rheumatoid arthritis (RA) developed under the companies' CD20 collaboration. However, Pfizer has confirmed that it will continue to develop SBI-087 (PF-05230895), Trubion's next-generation, humanized, subcutaneous CD20 RA product candidate also in Phase 2 clinical evaluation.

Pfizer's decision is based on preliminary results from the Phase 2b (2203) randomized, parallel, double-blind, placebo-controlled study designed to evaluate the efficacy and safety of two dosing regimens (a single dose of 800mg TRU-015 compared with an induction dose of 800mg TRU-015 followed by an additional dose of 800mg TRU-015 at week 12) in combination with methotrexate in patients with active rheumatoid arthritis.

Although the ACR (American College of Rheumatology) 20/50/70 results in the Phase 2 (2203) study were consistent with previous studies and similar to other B-cell-depleting therapies, the results did not meet the internally predefined primary endpoint, a 20% difference in ACR50 response compared with placebo at week 24 (p value = 0.06 for the single-dose group ACR 50 compared with placebo and p= 0.12 for the induction-dose group ACR 50 compared with placebo). A previously conducted interim analysis of the trial data on approximately 50% of the total enrolled patient population revealed that the primary endpoint had been met at that point in time. No significant safety issues were reported, and they were not a factor in Pfizer's decision to discontinue development.

TRU-015 demonstrated biologic activity including peripheral B-cell depletion and a statistically significant decrease in C-reactive protein in both dose groups compared with placebo. Specifically, ACR 20 was 67.1% for the induction-dose group, 61.3% for the single-dose group and 43.2% for the placebo group. ACR 50 was 27.4% for the induction dose, 29.3% for the single dose and 16.2% for placebo. ACR 70 was 9.6% for the induction dose, 9.3% for the single dose and 2.7% for placebo. TRU-015 was generally well-tolerated, and serious adverse events and medically important infection rates in both dose groups were similar to placebo.

"Given the higher than usual placebo response, TRU-015 did not meet the internal hurdle for continued development," said Scott C. Stromatt, M.D., senior vice president and chief medical officer at Trubion. "It is evident that the drug has significant biological and clinical activity with no significant safety concerns, but market dynamics dictate that we pursue a differentiated and best-in-class product to bring into Phase 3 development. At this time our next-generation CD20 SMIP product candidate, SBI-087, meets that criteria, and its Phase 2 development will continue."

"Although we are not moving forward with this compound, we are encouraged by our analysis to date of SBI-087," said Evan Loh, senior vice president of BioTherapeutics Research and Development at Pfizer. "The goal of our collaboration with Trubion continues to be the development of best-in-class CD20 therapies, and we look forward to the results of the ongoing SBI-087 Phase 2 study."

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, therapeutics, and are designed using its custom drug assembly technology. Trubion's product pipeline includes CD20-directed SMIP therapeutics such as SBI-087 for autoimmune and inflammatory diseases, developed under the Company's Pfizer collaboration. Trubion's product pipeline also includes TRU-016, a novel CD37-targeted therapy for the treatment of B-cell malignancies developed under the Company's Facet collaboration. In addition to Trubion's current clinical stage product pipeline, the Company is also developing its multi-specific SCORPION technology, both for targeting cell-surface molecules as well as simultaneously neutralizing soluble ligands. More information is available in the investors section of Trubion's website:

Forward-Looking Statements

Certain statements in this release may constitute "forward-looking statements" within the meaning of Section 21E of the Securities Exchange Act of 1934 and Section 27A of the Securities Act of 1933. These statements include, but are not limited to, those related to the future clinical development of the Company's programs that are the subject of the Pfizer collaboration, the timing and availability of data resulting from these programs and Pfizer's intentions regarding these programs. These statements are based on current expectations and assumptions regarding future events and business performance and involve certain risks and uncertainties that could cause actual results to differ materially. These risks include, but are not limited to, risks associated with the Company's Pfizer collaboration, including Pfizer's control over development timelines and over decisions regarding the advancement of TRU-015 and SBI-087, the risks that data resulting from our clinical development programs are unfavorable or uncertain and such other risks as identified in the Company's report on Form 10-Q for the quarter ended March 31, 2010, and from time to time in other reports filed by Trubion with the U.S. Securities and Exchange Commission. These reports are available on the Investors page of the Company's corporate website at Trubion undertakes no duty to update any forward-looking statement to conform the statement to actual results or changes in the Company's expectations.

TRBN-G Contact: Jim DeNike Senior Director, Corporate Communications Trubion Pharmaceuticals, Inc. (206) 838-0500

Waggener Edstrom Worldwide Healthcare Amy Petty Account Manager (617) 576-5788

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