MONROVIA, Calif., Nov. 13, 2016 /PRNewswire/ -- Xencor, Inc. (NASDAQ: XNCR), a clinical-stage biopharmaceutical company developing engineered monoclonal antibodies for the treatment of autoimmune diseases, asthma and allergic diseases and cancer, today announced preliminary data from XmAb5871-03, an ongoing, open-label, pilot Phase 2 study of XmAb5871 in patients with active IgG4- RD. Data show that 82% of patients achieved an initial response to therapy within two weeks of their first dose. The data are being presented by John H. Stone, M.D., MPH, director of rheumatology at Massachusetts General Hospital, at the American College of Rheumatology (ACR) 2016 Annual Meeting in the Miscellaneous Rheumatic and Inflammatory Disease session on Sunday, November 13, 2016 (today) at 2:45 p.m. EST.
"We are very encouraged by the rapid initial response in IgG4-RD disease activity observed in this preliminary data set, in which nine of the 11 patients evaluated for IgG4-RD Responder Index (RI) post-treatment achieved a response within two weeks of their first dose, with responses typically deepening over time," said Paul Foster, M.D., chief medical officer of Xencor. "We expect to report complete study results in 2017." "I am impressed by the steady 'dialing down' of the inflammatory response that XmAb5871 seems to exert in IgG4-RD and believe it is a promising potential therapy," said Dr. John H. Stone, the principal investigator of the study. "We are learning a lot about how to study this disease in the context of this small trial." As of a data cutoff of October 31, 2016, 12 patients with active IgG4-RD have been enrolled and dosed with XmAb5871 (median number of infusions = 7, range 1-12). Patients had a median IgG4-RD RI of 10 (range 2-30) with a median of four organs involved (range 1-10) at the time of study entry. Organ site involvement occurring at a frequency of greater than or equal to 50% included lymph nodes, submandibular glands, parotid glands and lacrimal glands. Preliminary Safety Data: Every other week intravenous administration of XmAb5871 has been well tolerated. As of October 31, 2016, no serious adverse events (AEs) have been reported. Treatment related AEs have occurred in five patients (42%). Treatment-related AEs that occurred in more than one patient were abdominal pain/discomfort in three patients (25%), occurring as part of Grade 1 (mild) infusion-related gastrointestinal symptoms (nausea and/or vomiting and/or diarrhea) during the first infusion, and Grade 1 (mild) headache in two patients (16.7%). One patient discontinued the study as the result of an AE. The patient developed a Grade 2 (moderate) hypersensitivity reaction with rash and arthritis, commonly referred to as serum sickness, following the fifth infusion. The event resolved quickly without the need for medical management. This patient was subsequently found to have developed anti-drug antibodies. Preliminary Efficacy Data: Eleven of the 12 patients dosed with XmAb5871 have had at least one IgG4-RD RI performed following dosing as of the data cutoff date. Nine of 11 patients (82%) have had an initial response to XmAb5871 therapy of at least a three-point reduction in the IgG4-RD RI within two weeks of the first dose. Five patients attained disease remission (an IgG4-RD RI of 0) during the study. Two patients entering the study on corticosteroids have been able to taper and discontinue steroid use during the study.