Interferon-alpha is an immune system hormone that is very helpful to a relatively small number of patients, and somewhat helpful to most patients. In about 65% of patients, the drug helps stabilize the disease or produce a slow, minor improvement for a partial response.The typical dosing schedule injects at least 3 million units of interferon-alpha (not pegylated versions) three times a week, although the original protocol began with 6 months of daily injections. Some patients tolerate IFN-alpha very well after the first fw weeks, while others find that its characteristic flu-like symptoms persist. About 10% of patients develop a level of depression. By maintaining a steadier level of the hormone in the body, daily injections might cause fewer side effects in selected patients. Drinking at least 2 liters of water each day, while avoiding caffeine and alcohol, can reduce many of the side effects. A drop in blood counts is usually seen during the first 1–2 months of treatment. Most patients find that their blood counts get worse for a few weeks immediately after starting treatment, although some patients find their blood counts begin to improve within just 2 weeks.Typically, 6 months are neededto figure out whether this therapy is useful. Common criteria for treatment success include:

Normalization of hemoglobin levels (above 12.0 g/dL),
A normal or somewhat low platelet count (above 100 K/µL), and
A normal or somewhat low absolute neutrophil count (above 1.5 K/µL).If it is well tolerated, patients usually take the hormone for 12 to 18 months.
All of these protein-based drugs combine part of an anti-B cell antibody with a bacterial toxin to kill the cells on internalization. BL22 and HA22 attack a common protein called CD22, which is present on hairy cells and healthy B cells. LMB-2 attacks a protein called CD25, which is not present in HCL-variant, so LMB-2 is only useful for patients with HCL-classic or the Japanese variant. HA-22, now renamed moxetumomab pasudotox, is being studied in patients with relapsed hairy cell leukemia at the National Cancer Institute in Bethesda, Maryland, MD Anderson Cancer Center in Houston, Texas, and Ohio State University in Columbus, Ohio. Other sites for the study are expected to start accepting patients in late 2014, including The Royal Marsden Hospital in London, England.Other clinical trials are studying the effectiveness of cladribine followed by rituximab in eliminating residual hairy cells that remain after treatment by cladribine or pentostatin. It is not currently known if the elimination of such residual cells will result in more durable remissions. BRAF mutation has been frequently detected in HCL (Tiacci et al. NEJM  2011) and some patients may respond to Vemurafenib. The major remaining research questions are identifying the cause of HCL and determining what prevents hairy cells from maturing normally. See also
Annexin A1
List of cutaneous conditions

References
External links

About HCL at the US National Cancer Institute
History of HCL and the Godmother of HCL