UCB and Immunomedics reported positive results from a follow-up phase I/II trial of epratuzumab for the treatment of systemic lupus erythematosus (SLE). Phase I of the trial enrolled 12 subjects with SLE and analyzed the effect of epratuzumab on circulatory B-cell subsets. Results showed that epratuzumab preferentially targets naive and transitional B-cells.

Phase II of the trial enrolled 11 subjects with SLE and 7 subjects without SLE. It was designed to analyze the effect of epratuzumab on the inhibition of the activation of B-cells. Epratuzumab stopped the over-activation of B-cells from SLE subjects but not normal B-cells, when activated by certain immune stimulating agents. Based on the results, Immunomedics plans to move forward with the development of epratuzumab. In May 2006, Immunomedics co-licensed exclusive rights to epratuzumab for all autoimmune indications to UCB.

Lupus is an autoimmune disease that causes the body's immune system to attack its own tissues, causing serious inflammation and pain. The Lupus Foundation of America (LFA) estimates that between 1.5 and 2 million people in the U.S. have the disease.