The medicine, known as XmAb5871, was developed for those with moderate to severe rheumatoid arthritis. It is the first in a new class of therapeutic antibodies that targets the CD32b pathway in B cells. Xencor said that it shows potential to suppress autoimmune disorders without harmful side effects usually caused when B cells are depleted.
When the first patient was dosed, it triggered a milestone payment from Amgen to Xencor for an undisclosed amount.
“The FcγRIIb [CD32b] pathway is generating increased interest as a novel therapeutic strategy for suppressing autoimmune responses, and XmAb5871 offers a unique and selective approach for engaging this pathway,” Dr. Bassil Dahiyat, the president and CEO of Xencor, said. “In this trial, we are looking for disease activity outcomes to inform a larger Phase 2 study and to further support the potential of XmAb5871 in autoimmune diseases such as lupus and rheumatoid arthritis.”
The Phase Ib trial has been designed to evaluate biweekly doses of XmAb5871. It will then rollover into a Phase IIa placebo controlled study. They study’s will also explore improvements in disease activity scales, serum inflammation markers and mechanism biomarkers.