Ibrutinib Effective for Severe Hairy Cell Leukemia by Angela Mohan on July 22, 2021 at 8:36 AM Blood. Hairy cell leukemia has generally a good prognosis for the majority of people affected. But, a small group of patients with variants of the disease do not respond well to existing U.S. Food and Drug Administration (FDA) approved therapies or cannot tolerate the side effects of established therapies. "There is a critical unmet need for therapy options in this subset of patients to achieve long-term cancer control," said Dr. Kerry Rogers, principal investigator of the clinical trial and a hematologist/scientist at the OSUCCC - James.