Cyclophosphamide Therapy in ANCA-Associated Vasculitis

Introduction to Cyclophosphamide Therapy

The Kidney Disease: Improving Global Outcomes (KDIGO) 2024 guidelines recommend glucocorticoids in combination with either rituximab or cyclophosphamide as initial treatment for new-onset AAV (Grade 1B recommendation) 1, 2

Cyclophosphamide achieves high remission rates when combined with glucocorticoids, particularly in severe renal disease, with rituximab being non-inferior in terms of efficacy but with similar rates of infectious complications 1, 2, 3
For MPO-ANCA vasculitis, cyclophosphamide and rituximab show equivalent efficacy 1, 5
For PR3-ANCA vasculitis, particularly relapsing disease, rituximab demonstrates superior remission rates (OR 3.57 at 6 months, OR 4.32 at 12 months) 1, 5, 3

The CYCLOPS trial established that pulse intravenous cyclophosphamide is as effective as daily oral cyclophosphamide for remission induction, with important safety advantages, including lower leukopenia rates 1, 5, 3
Dosing for intravenous cyclophosphamide is 15 mg/kg at weeks 0, 2, 4, 7, 10, 13 (with additional doses at weeks 16, 19, 21, 24 if required) 6

Glucocorticoid dosing is standardized across trials, with an initial dose of 1 mg/kg/day oral prednisolone (maximum 60 mg/day) for week 1 6, 4
The PEXIVAS trial demonstrated that rapid glucocorticoid tapering (achieving 5mg/day by week 19-20) is as effective but safer than standard tapering in patients with GFR <50 ml/min/1.73 m² 1, 4

For non-life-threatening disease in MPO-ANCA patients, mycophenolate mofetil (MMF) (2000-3000 mg/day) may be an alternative, with similar remission rates to cyclophosphamide in both PR3- and MPO-ANCA 1, 5, 3
Methotrexate is used for AAV without kidney disease in absence of irreversible tissue damage, but is associated with higher relapse rate and higher late accrual of damage compared to cyclophosphamide 1, 5

Mandatory supportive measures during cyclophosphamide therapy include pneumocystis jirovecii prophylaxis with trimethoprim/sulfamethoxazole, hydration, and monitoring for leukopenia 7, 8
MESNA (2-mercaptoethanesulfonate sodium) may be given with pulse cyclophosphamide to bind acrolein, reducing bladder toxicity 8

Following successful remission induction with cyclophosphamide, switching to less toxic maintenance therapy such as azathioprine (2 mg/kg/day) is standard, as it is as effective as continued cyclophosphamide but safer at 18 months 7
Maintenance therapy should continue for at least 18-24 months 7