Trubion Pharmaceuticals, Inc. (Nasdaq: TRBN) 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 ands 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.