Anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis is a systemic autoimmune disease characterized by small vessel inflammation caused by pathogenic autoantibodies directed against proteinase 3 (PR3) or myeloperoxidase (MPO). Immunosuppressive therapy can result in remission; however, many patients relapse, which results in additional injury.
Rituximab, a humanized murine monoclonal antibody directed against CD20 located on the surface of B-lymphocytes (B cells), is effective in depleting B cells. The RAVE and RITUXVAS trials have shown efficacy of rituximab with steroids for induction of remission in ANCA vasculitis, similar to cyclophosphamide and steroids. Rituximab is now FDA-approved for induction of remission therapy in ANCA vasculitis. The utility of anti-B-cell therapy for early induction of remission in ANCA vasculitis is not surprising given that ANCA are pathogenic in vitro and in vivo. It is clear that remission in many patients is not sustained with a single induction course of rituximab, and relapses often occur after B cell re-population suggesting that scheduled, serial dosing of rituximab could result in sustained remissions.
Despite yielding promising outcomes, rituximab is also associated with a number of adverse events including infectious complications and late onset of neutropenia5, 15. Furthermore, the complications of continuous B cell depletion for extended durations are unknown. One of the major goals in the field is to utilize prolonged B cell depletion only in the subpopulation of patients where the risk of disease relapse outweighs the risk of treatment-related adverse events.
A rise in ANCA titers and reconstitution of B cells are promising biomarkers of impending disease relapse following treatment with rituximab4-6
A prospective and longitudinal clinical trial is needed to determine the ideal treatment strategy for long-term maintenance of remission. We propose to compare intermittent rituximab dosing based on B cell return and a serologic ANCA flare
The study design is an open-label, single center, randomized and two-arm controlled trial to evaluate the optimal maintenance of remission strategy that provides the best relapse-free survival in patients with ANCA vasculitis as determined by relapse-free remission at 18, 24 and 36 months from enrollment. The investigators are looking to enroll and randomize 200 subjects with ANCA vasculitis on rituximab-induced continuous B cell depletion for a minimum of two years to one of two arms as follows:
1. Intermittent B cell depletion with rituximab re-dosing upon B cell return: Subjects will not receive their regularly-scheduled every-six-month dose of rituximab and will instead receive rituximab 1000 mg IV x 1 dose (spaced 2-3 weeks apart) once peripheral B cells return ( ≥ 10 B cells/mm3). This cycle will then re-start. Subjects will be seen in clinic every three months. Patients will continue to be dosed with rituximab each time the B cell count rises to 10 cells/mm3. In the unique scenario that the B cells are detectable, but less than the threshold of 10 cells/mm3, subjects will be asked to return in 6 weeks for repeat B cell testing.
2. Hold continuous dosing with rituximab with re-dosing upon a significant ANCA titer increase: For MPO, a significant increase will be defined as a 5-fold rise in ANCA titer and a level greater than 4 times the cutoff value for the assay. For PR3, a significant rise will be defined as a 4-fold rise in ANCA titer to a level at least twofold above the cutoff for the assay. Subjects will not receive regularly scheduled every six-month doses of rituximab and will instead be seen in clinic to have their ANCA titer monitored every three months. Subjects who sustain a significant increase in ANCA titer will receive rituximab 1000mg IV x 2 doses, \~2-3 weeks apart. If the ANCA titer remains two-fold above baseline and above a specified threshold (the cutoff value of the assay for PR3 and 4 times the cutoff value for MPO) , subjects will continue to receive rituximab 1000mg IV every 6 months for a maximum of 2 doses, at which time a new baseline ANCA titer will be established and the cycle will re-start.
