Xencor's XmAb5871 Receives Orphan Drug Designation from FDA for Treatment of IgG4-Related Disease

Xencor announced XmAb5871 has been granted orphan drug designation by the U.S. Food and Drug Administration (FDA) for the treatment of IgG4-Related Disease (IgG4-RD), a newly defined fibro-inflammatory autoimmune disorder that is estimated to impact up to 40,000 patients in the United States.

"There currently are no approved therapies for IgG4-RD, an immune-mediated condition responsible for fibro-inflammatory lesions that can lead to irreversible damage to virtually any organ," Bassil Dahiyat, Ph.D., president and chief executive officer of Xencor said. "New treatment options are clearly needed, and we are diligently moving XmAb5871 forward in clinical development to fill this void. Preliminary data from our Phase 2 study of XmAb5871 showed promising activity in patients with IgG4-RD, and we are on track to complete the study and report topline results by the end of this year.  We are also planning to engage the FDA later this year to discuss future clinical trials and potential registration requirements in IgG4-RD."

The FDA's Orphan Drug Designation program provides orphan status to drugs defined as those intended for the safe and effective treatment, diagnosis or prevention of rare diseases that affect fewer than 200,000 people in the U.S. Orphan designation qualifies the sponsor of the drug for certain development incentives, including tax credits for qualified clinical testing, prescription drug user fee exemptions and seven-year marketing exclusivity upon FDA approval.

XmAb5871 is a monoclonal antibody that targets CD19 with its variable domain and that uses Xencor's XmAb immune inhibitor Fc domain to target FcγRIIb, a receptor that inhibits B-cell function. XmAb5871 is the first drug candidate that Xencor is aware of that targets FcγRIIb inhibition. Xencor has demonstrated in multiple animal models and in initial human clinical trials that XmAb5871 inhibits B-cell function without destroying these important immune cells.

IgG4-Related Disease is a rare fibro-inflammatory autoimmune disorder responsible for fibro-inflammatory lesions that can lead to irreversible damage to virtually any organ. IgG4-RD is estimated to impact up to 40,000 patients in the United States. The disease affects multiple organ systems and is characterized by a distinct microscopic appearance of diseased organs, including the presence of IgG4-positive plasmablast cells.