Xencor Initiates Phase 1b/2a Trial of XmAb®5871 for Autoimmune Disease

    Xencor Initiates Phase 1b/2a Trial of XmAb®5871 for Autoimmune Disease

PR Newswire

MONROVIA, Calif., Feb. 13, 2013

MONROVIA, Calif., Feb. 13, 2013 /PRNewswire/ --Xencor, Inc. today announced
that the first patient has been dosed in a Phase 1b/2a clinical trial of
XmAb®5871 in patients with moderate to severe rheumatoid arthritis. XmAb5871
is the first in a new class of therapeutic antibodies targeting the CD32b
(FcγRIIb) pathway in B cells, which shows potential to suppress autoimmune
disorders without the side effects caused by B cell depletion. The trial
initiation triggered a milestone payment of an undisclosed amount to Xencor
from Amgen.

XmAb5871 is a humanized and Fc engineered monoclonal antibody that uses a
uniquely selective dual-targeting mechanism for B cell inhibition by
co-engaging CD19 and CD32b. Amgen and Xencor entered into an option and
co-development agreement for XmAb5871 in January 2011. Amgen has the option to
an exclusive worldwide license following the completion of a pre-defined Phase
2 study. Xencor will lead all clinical development until that time and is
eligible for early development milestone payments.

"The FcγRIIb 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," said Bassil Dahiyat, Ph.D.,
president and CEO of Xencor. "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

The Phase 1b trial will evaluate biweekly doses of XmAb5871 in patients with
moderate to severe rheumatoid arthritis and will roll into a Phase 2a placebo
controlled study. Endpoints will include improvements in disease activity
scales, serum inflammation markers and mechanism biomarkers.

XmAb5871 was well tolerated in a Phase 1a dose escalation study that enrolled
48 healthy male subjects and potently inhibited multiple biomarkers of immune

About Xencor, Inc.
Xencor, Inc. engineers superior biotherapeutics using its proprietary Protein
Design Automation® technology platform, and is a leader in the field of
antibody engineering to significantly improve antibody half-life,
immune-regulatory function and potency. The company is advancing multiple
XmAb® antibody drug candidates in the clinic, including XmAb®5871 targeting
CD32b and CD19 for autoimmune diseases, and an anti-CD30 candidate XmAb®2513
for the treatment of Hodgkin's lymphoma. Xencor is also advancing a portfolio
of biosuperior versions of blockbuster antibody drugs engineered for superior
half-life and dosing schedule. Xencor has entered into multiple partnerships
with industry leaders such as Amgen, Pfizer, Janssen R&D LLC, MorphoSys,
Boehringer Ingelheim, CSL Ltd. and Human Genome Sciences. In these
partnerships Xencor is applying its suite of proprietary antibody Fc domains
to improve antibody drug candidates for traits such as sustained half-life
and/or potency. For more information, please visit www.xencor.com.

SOURCE Xencor, Inc.

Website: http://www.xencor.com
Contact: Heidi Chokeir, Canale Communications for Xencor, +1-619-849-5377,
Press spacebar to pause and continue. Press esc to stop.