In addition to the use of drugs (Cladribine or Pentostatin), some patients are treated with a monoclonal antibody called Rituximab.

This antibody is able to attach to the leukemic cells in this disease. Hairy cells express a marker called CD20. Rituximab is an antibody that attaches to CD20 and can result in the death of the leukemic cells. This agent has been useful in treating some patients with non-responding hairy cell leukemia. In addition, there are studies that have used this agent to treat patients with minimal residual leukemia. The use of this agent for eradicating minimal residual disease is still an ongoing research approach.

Interferon is an agent that produced responses in about 80% of patients with hairy cell leukemia. The number of patients achieving a complete response is much lower (e.g., 10%). While the effectiveness of this agent is far lower than that with the usual drugs used to treat these patients, this agent can still help to improve blood counts in patients who are unable to tolerate the standard drugs.