RituximabRx

Trade Names: Rituxan

Drug Class: Anti CD-20 monoclonal antibody, biologic DMARD

Preparations: Injection: 100 mg/10 mL  and 500 mg/50 mL

Dose: Refer to individual i.v. infusion protocols in label.
For granulomatosis with polyangiitis:  375 mg/m2 once weekly for 4 weeks.  Also treated with IV  methylprednisolone.
For RA: 1,000 mg i.v. on days 1 and 15  and based on response readministration at 24 week intervals. Usually premedication with IV methylprednisolone 100 mg or equivalent. Usually administered for RA with background methotrexate therapy.

Indications: RA in combination with methotrexate and had inadequate response to at least one TNF inhibitor, granulomatosis with polyangiitis, non-Hodgkin’s lymphoma

Mechanism of Action: Binds to antigen on CD-20 positive cells and depletes B cells

Contraindications: Hypersensitivity to murine proteins; active infection; breast feeding; hepatitis B infection;

Precautions: Do not administer as intravenous push; administer slowly per protocols in package insert. Infusion reactions are common and may respond to slowing or temporary discontinuation of infusion or premedication with acetaminophen, diphenhydramine and corticosteroids. Screen to exclude hepatitis B and C before initiating therapy. For granulomatosis with polyangiitis consider prophylaxis against pneumocystis during, and for 6 months after, rituximab treatment.

Monitoring: Monitor for infusion reactions during infusion. Monitor  CBC and platelets every 2-4 months.

Pregnancy Risk: C

Adverse Effects
Common: Mild infusion reactions, allergy, headache, hypotension, nausea, leukopenia, urticaria
Less common: Vomiting, hypertension, thrombocytopenia, neutropenia, red cell aplasia, arrhythmia, serious (including fatal) infusion reactions, severe (including fatal) mucocutaneous reactions, reactivation of hepatitis B, bacterial viral and fungal infections, zoster, progressive multifocal leukoencephelopathy, bowel obstruction or perforation, psoriasis, vasculitis

Drug Interactions: Avoid concurrent use of other biologic immunosuppressants. Avoid live virus vaccines and BCG.

Comments: For severe ANCA-associated vasculitis a single course of rituximab was as effective as standard cyclophosphamide and then azathioprine for 18 months. The comparative efficacy and safety of rituximab retreatment compared to other strategies to maintain remission in ANCA-associated vasculitis is being defined. In a 28 month study low dose rituximab (500 mg) on days 0 and 14, and then at months 6, 12 and 18  was more effective than daily azathioprine in preventing major relapse in patients who had been in complete remission after a glucocorticoid and cyclophosphamide induction regimen.

Clinical Pharmacology: Half-life is approximately 18  days; can be detected in serum several months after administration; B cell recovery begins approximately 6 months after treatment and returns to baseline by 12 months.

Cost: $$$$$

BIBLIOGRAPHY

Specks U, Merkel PA, Seo P, et al. Efficacy of remission-induction regimens for ANCA-associated vasculitis. N Engl J Med 2013;369:417-27. PubMed PMID: 23902481.

Singh JA, Furst DE, Bharat A, et al. 2012 update of the 2008 American College of Rheumatology recommendations for the use of disease-modifying antirheumatic drugs and biologic agents in the treatment of rheumatoid arthritis. Arthritis Care Res 2012;64:625-39. PMID:22473917.