Rituximab is the chimeric anti-CD20 monoclonal antibody used for the treatment of B-cell lymphoproliferative diseases. It has also been used to treat some chronic inflammatory disorders (e.g., rheumatoid arthritis).
It may be associated with allergic or hypersensitivity reactions at the time of administration, but other adverse effects are usually mild and transient.

Woodruff R. Palliative medicine evidence-based symptomatic and supportive care for patients with advanced cancer. 4th ed. Oxford University Press, 2004. p. 444.