Xencor presents final results from Phase 2 study of XmAb5871
Xencor has announced the final results from a Phase 2 study of XmAb5871 in patients with active IgG4-RD. Data show that 12 of 15 patients completed the study, and all 12 achieved the primary endpoint of at least a two-point reduction in the IgG4-RD Responder Index on Day 169. None of the 12 required corticosteroids after month two. Eight patients achieved remission and the other four achieved IgG4-RD RI scores of less than or equal to4 at Day 169. Fourteen of 15 patients achieved a decrease of greater than or equal to 5 in the IgG4-RD RI. One patient had been on baseline CS for two years and was able to discontinue CS within two months. Four others received CS at the start of the trial and tapered off within two months. XmAb5871 was well tolerated. Three patients had minor, transient GI side-effects during the first infusion; all completed the study. Two serious adverse events unrelated to XmAb5871 were observed in one patient, pneumonia and recurrence of pneumonia due to non-compliance. Three patients discontinued the study, as disclosed previously. One discontinued patient was atypical with laryngeal involvement only who did not respond to XmAb5871 or to subsequent rituximab. A second patient responded, but flared at 12 weeks and did not respond to subsequent rituximab therapy. The third patient responded but developed infusion-related symptoms including transient rash and arthralgias following the fifth infusion. Plasmablasts were reduced 70%-80% from baseline and B cells were reduced 40-55% from baseline, with decreases occurring within the first two weeks.