LAUSR

OBJECTIVES Secondary inefficacy with infusion reactions and anti-drug antibodies (2NDNR) occurs in 14% of SLE patients receiving repeated rituximab courses. We evaluated baseline clinical characteristics, efficacy and safety of obinutuzumab, a next-generation humanised type-2 anti-CD20 antibody licensed for haematological malignancies in SLE patients with 2NDNR to rituximab. METHODS We collated data from SLE patients receiving obinutuzumab for secondary non-response to rituximab in BILAG centres. Disease activity was assessed using BILAG-2004, SLEDAI-2K and serology before, and 6 months after, obinutuzumab 2x1000mg infusions alongside methylprednisolone 100 mg. RESULTS All 9 patients included in the study received obinutuzumab with concomitant oral immunosuppression. At 6 months post-obinutuzumab, there were significant reductions in median SLEDAI-2K from 12 to 6 (p= 0.014) and total BILAG-2004 score from 21 to 2 (p= 0.009). Complement C3 and dsDNA titres improved significantly (both p= 0.04). Numerical, but not statistically significant improvements were seen in C4 levels. Of 8/9 patients receiving concomitant oral prednisolone at baseline (all >10mg/day), 5/8 had their dose reduced at 6 months. 4/9 patients were on 5 mg/day and were in Lupus Low Disease Activity State following obinutuzumab. After obinutuzumab, 6/9 patients with peripheral B cell data achieved complete depletion including 4/4 assessed with highly-sensitive assays. 1/9 obinutuzumab non-responder required cyclophosphamide therapy. 1 unvaccinated patient died from COVID-19. CONCLUSIONS Obinutuzumab appears to be effective and steroid-sparing in renal and non-renal SLE patients with secondary non-response to rituximab. These patients have severe disease with few treatment options but given responsiveness to B cell depletion, switching to humanised type-2 anti-CD20 therapy is a logical approach.