Xencor has announced dosing of the first patient in its Phase Ib/IIa trial of XmAbR5871 for rheumatoid arthritis, an autoimmune disease.
XmAb5871 is the first in a new class of therapeutic antibodies that target the CD32b (Fc?RIIb) pathway in B cells, with the potential to suppress autoimmune disorders.
The humanised and Fc engineered monoclonal antibody leverages a dual-targeting mechanism for B cell inhibition by co-engaging CD19 and CD32b.
Xencor president and CEO Dr Bassil Dahiyat said XmAb5871 offers a selective approach for engaging Fc?RIIb pathway that adopts new therapeutic strategy to suppress autoimmune responses.
"In this trial, we are looking for disease activity outcomes to inform a larger Phase II study and to further support the potential of XmAb5871 in autoimmune diseases such as lupus and rheumatoid arthritis," Dahiyat said.
The Phase Ib trial will assess two doses of XmAb5871 per week in patients with moderate-to-severe rheumatoid arthritis and move into a Phase IIa placebo-controlled study.
Improvements in disease activity scales, serum inflammation markers and mechanism biomarkers are the study endpoints.
XmAb5871 was well-tolerated in 48 healthy male subjects enrolled in the Phase Ia dose escalation study and potently inhibited multiple biomarkers of immune function.
Xencor received an undisclosed payment from Amgen for the commencement of the trial, according to an option and co-development agreement signed between the companies for XmAb5871 in January 2011.
Amgen has the option to an exclusive worldwide license subsequent to the completion of a pre-defined Phase II study, until which Xencor will lead all clinical development, and is eligible for early development milestone payments.