Rituximab resistance at 3months of induction therapy in newly diagnosed or relapsing ANCA-associated vasculitis: A French multicentre retrospective study in 116 patients.

OBJECTIVE:To evaluate rituximab (RTX) resistance at 3months (M3) of induction therapy in antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV). METHODS:Multicentre French retrospective study conducted between 2010 and 2020 including patients with newly diagnosed or relapsing AAV (granulomatosis with polyangiitis or microscopic polyangiitis) having received induction therapy with RTX. Primary endpoint was the presence of RTX resistance at 3months (M3) defined as uncontrolled disease (worsening feature on the BVAS/WG 1month after RTX induction) or disease flare (increase in BVAS/WG of≥1 point before M3). RESULTS:Out of 121 patients included, we analysed 116 patients. Fourteen patients (12%) had RTX resistance at M3 with no difference in baseline demographics, vasculitis type, ANCA type, disease status or organ involvement. Patients with RTX resistance at M3 had a greater proportion of localized disease (43% vs. 18%, P<0.05) and were less often treated by initial methylprednisolone (MP) pulse (21% vs. 58%, P<0.01). Out of the 14 patients with RTX resistance, seven received additional immunosuppressive therapy. All patients were in remission at 6months. Compared to responders, patients with RTX resistance at M3 were less often treated with prophylactic trimethoprim-sulfamethoxazole (57% vs. 85%, P<0.05). Twenty-four patients died during follow-up, one-third of them from infections and half of them from SARS-CoV-2. CONCLUSION:Twelve percent of patients had RTX resistance at M3. These patients more often had localized form of the disease and were less treated by initial MP pulse and by prophylactic trimethoprim-sulfamethoxazole.