Biopharmaceutical firm Xencor has reported interim positive results from the Phase II clinical trial of XmAb5871 for the treatment of patients with active IgG4-Related Disease (IgG4-RD).
XmAb5871 is a monoclonal antibody currently being developed to target CD19 using its variable domain and the XmAb immune inhibitor-Fc domain for targeting a FcγRIIb receptor known to inhibit B-cell function.
The results from the ongoing, open-label, single-arm, pilot Phase II trial indicated that 93% of the total 15 patients demonstrated a response to therapy, including 12 subjects who responded within two weeks after receiving the first dose.
The trial assessed the safety, tolerability, pharmacokinetics and immunogenicity of an intravenous infusion of XmAb5871 every other week over six months.
The primary endpoint of the trial is the proportion of patients on day 169 who showed an improved disease activity score.
Xencor chief medical officer Paul Foster said: “We continue to be very encouraged by the rapid initial response in IgG4-RD disease activity observed in this interim data set, in which now 14 of 15 patients evaluated for IgG4-RD responder index (RI) achieved a response, with initial responses typically occurring after the first dose and deepening over time."
The response to XmAb5871 therapy was found to be greater than or equal to a two-point decrease in the IgG4-RD RI.
At two weeks after the last dose, five patients were reported to have an IgG4-RD RI of 0 and were not on corticosteroid therapy between two-six months. A sixth patient achieved remission later in the post-therapy follow-up period.
The circulating CD19+ plasmablast levels and the numbers of circulating SLAMF7+ CD4+ cytotoxic T-lymphocytes were found to be lowered following treatment with XmAb5871.
The final data from the trial is expected to be available within the coming months.