The FDA has announced that the anti-CD20-directed monoclonal antibodies rituximab (Rituxan) and ofatumumab (Arzerra) will carry a boxed warning for immunosupression-related reactivation of hepatitis B virus (HBV) in a drug safety communication.

The two drugs are used to treat patients with chronic lymphocytic leukemia. Rituximab is also used for nonHodgkin’s lymphoma, rheumatoid arthritis, vasculitis and other conditions. 

HBV reactivation can occur in patient who previously had an HBV infection that was clinically resolved, but who later require immunosupressive therapy for conditions such as cancer, or in patients who were unaware of an initial HBV infection in whom the virus remains latent in liver tissue. Subsequent liver failure and death can result, the FDA is warning. 

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The agency has identified more than 100 possible cases of fatal HBV-associated hepatic injury associated with rituximab and ofatumumab in it’s Adverse Even Reporting System database.

Although labeling for both medications already warns of the potential for HBV reactivation, the FDA is adding more information to the rituximab label and a new boxed warning to ofatumumab.

Labeling changes will include a recommendation that healthcare providers screen all patients for previous HBV exposure by measuring hepatitis B surface antigen (HBsAg) and the hepatitis B core antibody (anti-HBc) prior to initiating treatment with rituximab or ofatumumab.

The new recommendations also advise healthcare professionals to consult with hepatitis experts for advise on monitoring treatment in patients who test positive for HBV.

Treatment with rituximab or ofatumumab or any other immunosuppressive treatment should be discontinued in any patient that develops HBV reactivation and HBV treatment should be initiated.

As of August 2012, the FDA has identifed 109 cases of fatal HBV-related acute liver injury associated with these therapies — 106 with rituximab and 3 with ofatumumab — of which 32 cases had sufficient information to be deemed an HBV reactivation. Most patients were men with a mean age of 62 years.

The time of reactivation in relation to exposure to anti-CD20 monoclonal antibody was highly variable, ranging from 63 days from the first dose to 12 months after the last dose. All cases had recent or concomitant exposure to other chemotherapy agents also.

The FDA is urging healthcare professionals to discuss the risk of serious infections with all patients prior to beginning therapy, and to report any such events to the FDA’s MedWatch Safety Information and Adverse Event Reporting Program.

This article originally appeared on Clinical Advisor